Pedersen, Preben Terndrup; Jensen, Jørgen Juncher
2009-01-01
-induced loads are evaluated for specific operational profiles. Non-linearity in the wave bending moment is modeled using results derived from a second-order strip theory and water entry solutions for wedge type sections. Hence, bow flare slamming is accounted for through a momentum type of approach....... The stochastic properties of this non-linear response are calculated through a monotonic Hermite transformation. In addition, the impulse loading due to e.g. bottom slamming or a rapid change in bow flare is included using a modal expansion in the two lowest vertical vibration modes. These whipping vibrations...
Andersen, Ingrid Marie Vincent; Jensen, Jørgen Juncher
2012-01-01
analysis is done using the First Order Reliability Method (FORM) supplemented with Monte Carlo simulations. Furthermore, strip-theory calculations are compared to model tests in regular waves of different wave lengths using a segmented, flexible model of the case-ship and good agreement is obtained...... for the 9,400 TEU container ship used as case-ship in the EU project TULCS (Tools for Ultra Large Container Ships). A non-linear time-domain strip theory is used for the hydrodynamic analysis of the vertical bending moment amidships in sagging and hogging conditions for a flexible and a rigid modelling...... of the ship. The theory takes into account non-linear radiation forces (memory effects) through the use of a set of higher order differential equations. The non-linear hydrostatic restoring forces and non-linear Froude-Krylov forces are determined accurately at the instantaneous position of the ship...
The maximum bending moment resistance of plate girders
Abspoel, R.
2014-01-01
In many steel structures like buildings, industrial halls and bridges, standard hot-rolled sections like IPE, HEA, HEB, HEM, HED and UNP in Europe and similar profiles in other regions of the world are used. The range of hot-rolled sections is limited and therefore fabricated plate girders are used
The maximum bending moment resistance of plate girders
Abspoel, R.
2014-01-01
In many steel structures like buildings, industrial halls and bridges, standard hot-rolled sections like IPE, HEA, HEB, HEM, HED and UNP in Europe and similar profiles in other regions of the world are used. The range of hot-rolled sections is limited and therefore fabricated plate girders are used
Effects of vertical girder realignment in the Argonne APS storage ring.
Lessner, E.
1999-04-14
The effects of vertical girder misalignments on the vertical orbit of the Advanced Photon Source (APS) storage ring are studied. Partial sector-realignment is prioritized in terms of the closed-orbit distortions due to misalignments of the corresponding girders in the sectors. A virtual girder-displacement (VGD) method is developed that allows the effects of a girder realignment to be tested prior to physically moving the girder. The method can also be used to anticipate the corrector strengths needed to restore the beam orbit after a realignment. Simulation results are compared to experimental results and found to reproduce the latter quite closely. Predicted corrector strengths are also found to be close to the actual local corrector strengths after a proof-of-principle two-sector realignment was performed.
Extreme value prediction of the wave-induced vertical bending moment in large container ships
Andersen, Ingrid Marie Vincent; Jensen, Jørgen Juncher
2015-01-01
in the present paper is based on time series of full scale measurements from three large container ships of 8600, 9400 and 14000 TEU. When carrying out the extreme value estimation the peak-over-threshold (POT) method combined with an appropriate extreme value distribution is applied. The choice of a proper...... increase the extreme hull girder response significantly. Focus in the present paper is on the influence of the hull girder flexibility on the extreme response amidships, namely the wave-induced vertical bending moment (VBM) in hogging, and the prediction of the extreme value of the same. The analysis...... threshold level as well as the statistical correlation between clustered peaks influence the extreme value prediction and are taken into consideration in the present paper....
Wave induced extreme hull girder loads on containerships
Jensen, Jørgen Juncher; Pedersen, Preben Terndrup; Shi, Bill;
2009-01-01
, forward speed and hull flexibility. The vertical hull girder loads are evaluated for specific operational profiles. Firstly a quadratic strip theory is presented which can give separate predictions for the hogging and sagging bending moments and shear forces and for hull girder loads. Then this procedure...... is used as a base to derive semi-analytical formulas such that approximate wave load calculations can be performed by a simple spreadsheet program. Due to the few input parameters this procedure can be used to estimate the wave-induced bending moments at the conceptual design phase. Since the procedure...
Effect of train carbody's parameters on vertical bending stiffness performance
Yang, Guangwu; Wang, Changke; Xiang, Futeng; Xiao, Shoune
2016-10-01
Finite element analysis(FEA) and modal test are main methods to give the first-order vertical bending vibration frequency of train carbody at present, but they are inefficiency and waste plenty of time. Based on Timoshenko beam theory, the bending deformation, moment of inertia and shear deformation are considered. Carbody is divided into some parts with the same length, and it's stiffness is calculated with series principle, it's cross section area, moment of inertia and shear shape coefficient is equivalent by segment length, and the fimal corrected first-order vertical bending vibration frequency analytical formula is deduced. There are 6 simple carbodies and 1 real carbody as examples to test the formula, all analysis frequencies are very close to their FEA frequencies, and especially for the real carbody, the error between analysis and experiment frequency is 0.75%. Based on the analytic formula, sensitivity analysis of the real carbody's design parameters is done, and some main parameters are found. The series principle of carbody stiffness is introduced into Timoshenko beam theory to deduce a formula, which can estimate the first-order vertical bending vibration frequency of carbody quickly without traditional FEA method and provide a reference to design engineers.
Influence of Whipping on Long term Vertical Bending Moment
Baarholm, G. S.; Jensen, Jørgen Juncher
2004-01-01
This paper is concerned with estimating the response value corresponding to a long return period, say a twenty years. Time domain simulation is required to obtain the nonlinear response, and long time series are required to limit the statistical uncertainty in the simulations. It is crucial to in......). Results are presented for the S-175 container ship, (15th & 16th ITTC Seakeeping Committee 1983). The analysis shoes that whipping increases the vertical bending moment and that the correlation is significant...
Behavior of horizontally curved steel tubular-flange bridge girders
Fan, Zhuo
system than in an I-girder system, which results in smaller cross frame members. The study also indicates that a curved tubular-flange girder system may need fewer cross frames than a curved I-girder system. Finally, for curved girder systems with a composite deck, the behavior of tubular-flange girder systems is dominated by bending stresses, while the behavior of I-girder systems includes significant warping stresses, again suggesting that the tubular-flange girder system may be more efficient.
何庆华; 卫星
2013-01-01
曲线箱形梁兼具弯梁桥与箱形梁两者的特点,由于曲率的影响,竖向荷载作用下曲线箱梁弯矩与扭矩互相耦合同时存在.根据国内外既有研究成果,对曲线箱形梁空间受力特点及影响因素进行了总结.以60m单跨单箱形截面曲线混凝土简支梁为例,利用有限元软件TDV建立空间板单元模型,分析自重作用下,不同曲线半径下主梁截面正应力及剪应力分布,根据弯曲变形与应变的关系,比较曲线梁桥与直线梁桥正应力横向分布规律,提出用应力增大系数来表征曲线内外侧弧长不同引起的应力变化.研究结果表明,除了受剪力滞后效应影响,曲线箱梁桥截面正应力分布还与内外侧弧长不等引起的应力增大系数有关.%Curved box girder has both characters of curved girder and box girder, and the coupling effect between bending moment and torsion moment caused by the curvature under vertical load should be taken into account. Based on research results of curved girder at home and abroad, the spatial mechanical characters and influencing factors of curved box girder were summarized in this thesis. Choosing a 60m single-span curved PC simply supported girder with single cell boxed cross-section as the example, spatial plate element models were established by TDV finite element software. Then the distributions of normal stress and shear stress of cross-section of main girder with different curve radius under the action of dead load were analyzed. Afterwards, according to the relationship between bending deformation and strains, and by comparing the transverse distributions of normal stress of curved bridge with that of straight bridge, the thesis put forward a view point that the stress variation caused by the arc length difference between the internal arc and external arc of the curve can be expressed by a magnification coefficient. Analysis results show that, except the effect of shear lag, the distributions of
Dynamic Analysis of Horizontally Curved Thin-Walled Box-Girder Bridge due to Moving Vehicle
K. Nallasivam
2007-01-01
Full Text Available The impact on curved box-girder bridges due to vehicle moving across rough bridge deck have been analyzed using bridge-vehicle coupled dynamics. The bridge deck unevenness has been assumed to be a homogeneous random process in space specified by a PSD function. The analysis incorporates the effect of centrifugal forces due to vehicle moving on curved bridge. The curved box-girder bridge has been numerically modeled using computationally efficient thin-walled box-beam finite elements which take into account the torsional warping, distortion and distortional warping, that are important features of thin-walled box girders. Rigid vehicle with longitudinal and transverse input to the wheels giving rise to heave-pitch-roll degrees of freedom has been considered. The theoretical bridge model used in simulation study has been validated by a free vibration experiment using impact excitation. The impact factors for several response parameters such as bending moment, shear force, torsional moment, torsional bi-moment, distortional moment, distortional bi-moment and vertical deflections have been obtained for various bridge-vehicle parameters. Both constant velocity and forward acceleration of the vehicle have been considered to examine impact factor. The results highlighted that the impact factors of a curved box girder bridge corresponding to torsion, distortion and their corresponding bimoments have been observed to be generally very high, while those of the other responses are also relatively higher than that of corresponding straight box girder bridge.
Kortright, J.B.; Rice, M.; Hussain, Z. [Lawrence Berkeley National Lab., CA (United States)] [and others
1997-04-01
Growing interest in utilizing circular polarization prompted the design of bend-magnet beamline 9.3.2 at the Advanced Light Source, covering the 30-1500 eV spectral region, to include vertical aperturing capabilities for optimizing the collection of circular polarization above and below the orbit plane. After commissioning and early use of the beamline, a multilayer polarimeter was used to characterize the polarization state of the beam as a function of vertical aperture position. This report partially summarizes the polarimetry measurements and compares results with theoretical calculations intended to simulate experimental conditions.
Comparison of Temperature Loadings of Bridge Girders
J. Římal
2008-01-01
Full Text Available This paper compares the effect of temperature changes on the superstructure of bridges, above all the effect of non-uniform temperature. Loadings according to standards ESN 73 6203, ENV 1991-1-5 and DIN 1072 are compared here. The paper shows a short summary of temperature loading according to each standard and shows the comparison of bending moments arisen from these temperature loadings on superstructure made from continuous girder from a steel-concrete box girder with a composite concrete slab. With respect to a variety of design processes, the comparison is made without any coefficient of loading, combination or material.
Li, Tianjin, E-mail: tjli@tsinghua.edu.cn; Zhang, He; Liu, Malin; Huang, Zhiyong; Bo, Hanliang; Dong, Yujie
2017-04-01
Highlights: • The work concerns granular flow in a vertical pipe with a bend. • Discharge rate fluctuation in vertical pipe are mainly from velocity fluctuation. • Steady discharge rate decreases rapidly and saturates with μ{sub s} increasing. • Steady discharge rate W{sub s} still obey the 5/2 power law of pipe internal diameter. • A correlation developed for steady discharge rate for this new geometry. - Abstract: Absorber sphere pneumatic conveying is a special application of pneumatic conveying technique in the pebble bed High Temperature Gas-Cooled Reactor (HTGR or HTR). Granular discharge through a vertical pipe with a bend outlet is one of the control modes to determine solid mass flowrate which is an important parameter for the design of absorber sphere pneumatic conveying. Granular discharge rate through the vertical pipe with a bend outlet in the small absorber sphere system are investigated by discrete element method simulation. The effect of geometry parameters on discharge rate, the discharge rate fluctuation in the vertical pipe, and the effect of friction on steady discharge rate (W{sub s}) are analyzed and discussed. The phenomena of discharge rate fluctuation in the vertical pipe are observed, which are mainly resulted from the evolution of the average downward granular velocity. The steady discharge rate decreases rapidly with sliding friction coefficient increasing from 0.125 to 0.5, and gradually saturates with the friction coefficient further increasing from 0.5 to 1. It is interesting that the linear relation between W{sub s}{sup 2/5} and pipe internal diameter D with zero intercept are found for the vertical pipe discharge with a bend outlet, which is different from the orifice discharge through a hopper or silo with none-zero intercept. A correlation similar to Beverloo’s correlation is developed to predict the steady discharge rate through the vertical pipe with a bend outlet. These results are helpful for the design of sphere
Suspension Bridge Flutter for Girder with Separate Control Flaps
Huynh, T.; Thoft-Christensen, Palle
Active vibration control of long span suspension bridge flutter using separated control flaps (SFSC) has shown to increase effectively the critical wind speed of bridges. In this paper, an SFSC calculation based on modal equations of the vertical and torsional motions of the bridge girder including...
Wind Turbine Blade with Angled Girders
2011-01-01
The present invention relates to a reinforced blade for a wind turbine, particularly to a blade having a new arrangement of two or more girders in the blade, wherein each of the girders is connected to the upper part and the lower part of the shell and forms an angle with another girder thereby...
Wind Turbine Blade with Angled Girders
2011-01-01
The present invention relates to a reinforced blade for a wind turbine, particularly to a blade having a new arrangement of two or more girders in the blade, wherein each of the girders is connected to the upper part and the lower part of the shell and forms an angle with another girder thereby...
Distortional Buckling Analysis of Steel-Concrete Composite Girders in Negative Moment Area
Zhou Wangbao
2014-01-01
Full Text Available Distortional buckling is one of the most important buckling modes of the steel-concrete composite girder under negative moment. In this study, the equivalent lateral and torsional restraints of the bottom flange of a steel-concrete composite girder under negative moments due to variable axial forces are thoroughly investigated. The results show that there is a coupling effect between the applied forces and the lateral and torsional restraint of the bottom flange. Based on the calculation formula of lateral and torsional restraints, the critical buckling stress of I-steel-concrete composite girders and steel-concrete composite box girders under variable axial force is obtained. The critical bending moment of the steel-concrete composite girders can be further calculated. Compared to the traditional calculation methods of elastic foundation beam, the paper introduces an improved method, which considers coupling effect of the external loads and the foundation spring constraints of the bottom flange. Fifteen examples of the steel-concrete composite girders in different conditions are calculated. The calculation results show a good match between the hand calculation and the ANSYS finite element method, which validated that the analytic calculation method proposed in this paper is practical.
Pangaribuan, Adrianus; Dhiputra, I. M. K.; Nugroho, Yulianto S.
2017-03-01
Electrical cable is a whole of the material including metal (cooper) conductor and its insulation, when an electrical cable is flowed by electric current, based on its own capacity, the temperature of cable conductor increases gradually. If the current flows above the cable carrying capacity, then an extreme temperature rises are expected. When temperature increase, the electric current flow inside cable conductor will decrease gradually related to the resistance and could occur repeatedly in a period. Since electrical faults on electrical cable system are often suspected as the cause of fires, thus this research aims to investigate measures of preventing the fire to start by means of controlling oxygen concentration in a cable compartment. The experimental work was conducted in laboratory by using electrical power cable of 1.5 mm2 size. Two transparent chambers were applied for studying the effect of vertical and horizontal orientations on the cable temperature rise, under various oxygen concentration of the gas streams. In the present work, the electrical was maintained at a constant level during a typical test run. Parametric studies reported in the paper include the use of a bare and insulated cables as well as the bending shape of the cable lines of a straight cable, coiled cable and randomly bent cable which were loaded with the same electric load and oxygen concentration in the gas supply.
Matrix Analysis on Flexural Behavior of Thin-walled Box Girder%薄壁箱梁挠曲性能的矩阵分析
张元海; 林丽霞; 李乔
2011-01-01
On the basis of the shape function matrix which is established through assuming the homogeneous solution to the governing differential equation for shear lag of the thin-walled box girder as the element displacement function, the formula of the equivalent nodal force of the element under vertical concentrated loads is derived by applying the principle of virtual work. The reasonable warping displacement function of shear lag is proposed for the box girder with the twin-cell cross-section. The plexiglass model of the cantilever box girder with variable cross-sections is calculated, thus validating the effectiveness of the finite segment element in analysis of the box girder with variable cross-sections. The flexural behavior of the prestressed concrete continuous box girder with variable cross-sections is analyzed through a practical example. The results show as follows:The finite segment element has high computing efficiency for the box girder with variable cross-sections; under the action of vertical concentrated loads, the shear lag moment diagram of the box girder is a smooth curve and the absolute value of the shear lag moment is not greater than that of the bending moment at any cross-sections; the shear lag effect increases the mid-span deflection of the continuous box girder significantly, which shall be treated seriously in engineering practice.%在选取薄壁箱梁剪力滞控制微分方程的齐次解作为单元位移函数建立形函数矩阵基础上,运用虚功原理推导竖向集中荷载作用下单元等效节点力公式,提出双室箱梁的合理剪滞翘曲位移函数.通过对变截面悬臂箱梁有机玻璃模型进行计算,验证提出的梁段单元对分析变截面箱梁的有效性.结合实际箱梁算例,分析预应力混凝土变截面连续箱梁的挠曲性能.研究结果表明:所提出的梁段单元用于变截面箱梁分析时,具有较高的计算精度;在竖向集中荷载作用下,箱梁剪滞力矩图是一条
On the Influence of Hull Girder Flexibility on the Wave
Seng, Sopheak; Andersen, Ingrid Marie Vincent; Jensen, Jørgen Juncher
2012-01-01
Numerical predictions and model test results of the wave induced bending moments in a 9,400 TEU post-Panamax container vessel are presented for two regular wave scenarios. Different numerical procedures have been applied: a linear and non-linear time-domain strip theory and a direct calculation (...... (CFD) solving the Navier-Stokes equations with the free surface captured by a volume-of-fluid (VOF) method. In all procedures the flexibility of the hull girder is modelled as a non-uniform Timoshenko beam. It is observed that the non-linear models agree well with the model tests...
Precast Prestressed Concrete Truss-Girder for Roof Applications
Peter Samir
2014-01-01
Full Text Available Steel trusses are the most popular system for supporting long-span roofs in commercial buildings, such as warehouses and aircraft hangars. There are several advantages of steel trusses, such as lightweight, ease of handling and erection, and geometric flexibility. However, they have some drawbacks, such as high material and maintenance cost, and low fire resistance. In this paper, a precast concrete truss is proposed as an alternative to steel trusses for spans up to 48 m (160 ft without intermediate supports. The proposed design is easy to produce and has lower construction and maintenance costs than steel trusses. The truss consists of two segments that are formed using standard bridge girder forms with block-outs in the web which result in having diagonals and vertical members and reduces girder weight. The two segments are then connected using a wet joint and post-tensioned longitudinally to form a crowned truss. The proposed design optimizes the truss-girder member locations, cross-sections, and material use. A 9 m (30 ft long truss specimen is constructed using self-consolidated concrete to investigate the constructability and structural capacity of the proposed design. A finite element analysis of the specimen is conducted to investigate stresses at truss diagonals, verticals, and connections. Testing results indicate the production and structural efficiency of the developed system.
邵天吉; 余本俊
2014-01-01
铜陵公铁两用长江大桥为五跨连续钢桁梁三索面斜拉桥，钢桁梁采用板桁结合形式，由3片主桁、上层正交异性公路板式桥面、下层正交异性铁路钢箱桥面及横联构成。钢桁梁采用整体焊接式桁片结构，每2个节间的主桁上、下弦杆，斜杆，竖杆通过整体节点焊接成桁片上桥安装。为验证制造工艺和精度并指导实桥施工，选取3．5个连续节间钢桁梁在工厂内一次完成立体试拼装。由于主桁桁片采用水平拼装制作工艺，采用800 t龙门吊机2×200 t吊钩提升加横移对桁片进行90°转体翻身后试拼装。试拼装过程中设置了抗推拉刚性斜撑增强桁片与铁路桥面的稳定性；在斜杆件加垫片，通过调整间隙控制桥梁预拱度。试拼装过程中设置了测量控制网，检测结果满足设计和验收标准，达到了立体试拼装目的。%The Tongling Changjiang River Rail‐cum‐Road Bridge is a five‐span continuous steel truss girder cable‐stayed bridge with three cable planes .The steel truss girder is the combined or‐thotropic steel plates and steel trusses structure ,containing three main trusses ,the upper ortho‐tropic steel plate deck for vehicles ,the lower orthotropic railway steel box deck and lateral brac‐ings .The steel truss girder is a integrally‐welded truss structure ,the upper and lower chords ,di‐agonal struts and vertical struts of the main trusses in every two blocks are welded by integral nodes to be truss block for assembling on the bridge .In order to verify the manufacturing tech‐nique and precision and to direct the construction of the real bridge ,the steel truss girder in 3 .5 continuous blocks were selected to conduct one‐time trial vertical assembly in the factory .The main truss blocks were fabricated by the horizontal assembling technique ,the 800 t overhead lift‐ing gantry with two lifting hooks of 200 t was adopted to lift and horizontally
Experimental Evaluation of the Post-ultimate Strength Behavior of a Ship's Hull Girder in Waves
Weijun Xu; Kazuhiro Iijima; Ryota Wada; Masahiko Fujikubo
2012-01-01
Experimental investigations into the collapse behavior of a box-shape hull girder subjected to extreme wave-induced loads are presented.The experiment was performed using a scaled model in a tank.In the middle of the scaled model,sacrificial specimens with circular pillar and trough shapes which respectively show different bending moment-displacement characteristics were mounted to compare the dynamic collapse characteristics of the hull girder in waves.The specimens were designed by using finite element (FE)-analysis.Prior to the tank tests,static four-point-bending tests were conducted to detect the load-carrying capacity of the hull girder.It was shown that the load-carrying capacity of a ship including reduction of the capacity after theultimate strength can be reproduced experimentally by employing the trough type specimens.Tank tests using these specimens were performed under a focused wave in which the hull girder collapses under once and repetitive focused waves.It was shown from the multiple collapse tests that the increase rate of collapse becomes higher once the load-carrying capacity enters the reduction path while the increase rate is lower before reaching the ultimate strength.
Almabrok, Almabrok A.; Aliyu, Aliyu M.; Baba, Yahaya D.; Lao, Liyun; Yeung, Hoi
2017-08-01
We investigate the effect of a return U-bend on flow behaviour in the vertical upward section of a large-diameter pipe. A wire mesh sensor was employed to study the void fraction distributions at axial distances of 5, 28 and 47 pipe diameters after the upstream bottom bend. The study found that, the bottom bend has considerable impacts on up-flow behaviour. In all conditions, centrifugal action causes appreciable misdistribution in the adjacent straight section. Plots from WMS measurements show that flow asymmetry significantly reduces along the axis at L/D = 47. Regime maps generated from three axial locations showed that, in addition to bubbly, intermittent and annular flows, oscillatory flow occurred particularly when gas and liquid flow rates were relatively low. At this position, mean void fractions were in agreement with those from other large-pipe studies, and comparisons were made with existing void fraction correlations. Among the correlations surveyed, drift flux-type correlations were found to give the best predictive results.
Vibration and Buckling of Web Plate of the Plate Girder
高橋, 和雄; 呉, 明強; 中澤, 聡志; 筑紫, 宏之
1998-01-01
The vibration and buckling of the web of the plate girder are studied in this paper. The small deflection theory of the thin plate is used. The finite strip method is employed to solve vibration and buckling of the plate girder. Natural frequenies of buckling properties are shown for various plate girder bridges.
Stanislav Kitarović
2016-06-01
Full Text Available This paper considers the hull girder ultimate strength of a bulk carrier at its midship section, as determined by an incremental-iterative progressive collapse analysis method prescribed by the International Association of Classification Societies Common Structural Rules for Bulk Carriers. In addition to the originally prescribed load – end shortening curves, curves determined by the nonlinear finite element method analysis (considering the influence of the idealized initial geometrical imperfections are also considered. Results obtained by both sets of curves are compared and discussed on both local (structural components load – end shortening curve and global (hull girder ulti-mate bending capacity and collapse sequence level, for both sagging and hogging cases.
Experiments with Externally Prestressed Continuous Composite Girders
M. Safan
2001-01-01
Full Text Available Steel-concrete composite girders have attractive potentials when applied in bridge construction. The serviceability performance of continuous composite girders is becoming more and more a deterministic parameter in the design of this type of structures. An effective method for improving this performance is to apply prestressing to control or completely eliminate concrete deck cracking caused by static and time dependent actions. Little literature has been found addressing the experimental analysis of continuous girders prestressed by means of external deviated tendons. The current research aims to investigate the behavior of a double-span steel composite beam externally prestressed by means of continuous tendons in terms of cracking characteristics, load deflection response, and load carrying capacity. The efficiency of prestressing is evaluated by comparing the results to those of a non-prestressed beam with similar cross sections and spans.
Fatigue crack detection in a plate girder using Lamb waves
Greve, D. W.; Oppenheim, I. J.; Wu, Wei; Zheng, Peng
2007-04-01
We report on the application of wafer-type PZT transducers to the detection of flaws in steel plate girders. In these experiments one transducer is used to emit a pulse and the second receives the pulse and reflections from nearby boundaries, flaws, or discontinuities (pitch-catch mode). In this application there will typically be numerous reflections observed in the undamaged structure. A major challenge is to recognize new reflections caused by fatigue cracks in the presence of these background reflections. A laboratory specimen plate girder was fabricated at approximately half scale, 910 mm deep with an h/t ratio of 280 for the web and a b/t ratio of 16 for the flanges, and with transverse stiffeners fabricated with a web gap at the tension flange. Two wafer-type transducers were mounted on the web approximately 175 mm from the crack location, one on each side of the stiffener. The transducers were operated in pitch-catch mode, excited by a windowed sinusoid to create a narrowband transient excitation. The transducer location relative to the crack corresponded to a total included angle of roughly 30 degrees in the path reflecting from the crack. Cyclic loading was applied to develop a distortion-induced fatigue crack in the web at the web gap location. After appearance of the crack, ultrasonic measurements were performed at a range of center frequencies below the cutoff frequency of the A1 Lamb wave mode. Subsequently the crack was extended mechanically to simulate crack growth under primary longitudinal (bending) stress and the measurements were repeated. Direct differencing of the signals showed arrivals at times corresponding to reflection from the crack location, growing in amplitude as the crack was lengthened mechanically. These results demonstrate the utility of Lamb waves for crack detection even in the presence of numerous background reflections.
Committee VI.1. Extreme Hull Girder Loading
Jensen, Jørgen Juncher
2000-01-01
Committee Mandate. Evaluate and develop direct calculation procedures for extreme wawe loads on ship hull girders. Due consideration shall be given to stochastic and non-linear effects. The procedures shall be assessed by comparison with in-service experiences, model tests and more refined...
Locally Corroded Stiffener Effect on Shear Buckling Behaviors of Web Panel in the Plate Girder
Jungwon Huh
2015-01-01
Full Text Available The shear buckling failure and strength of a web panel stiffened by stiffeners with corrosion damage were examined according to the degree of corrosion of the stiffeners, using the finite element analysis method. For this purpose, a plate girder with a four-panel web girder stiffened by vertical and longitudinal stiffeners was selected, and its deformable behaviors and the principal stress distribution of the web panel at the shear buckling strength of the web were compared after their post-shear buckling behaviors, as well as their out-of-plane displacement, to evaluate the effect of the stiffener in the web panel on the shear buckling failure. Their critical shear buckling load and shear buckling strength were also examined. The FE analyses showed that their typical shear buckling failures were affected by the structural relationship between the web panel and each stiffener in the plate girder, to resist shear buckling of the web panel. Their critical shear buckling loads decreased from 82% to 59%, and their shear buckling strength decreased from 88% to 76%, due to the effect of corrosion of the stiffeners on their shear buckling behavior. Thus, especially in cases with over 40% corrosion damage of the vertical stiffener, they can have lower shear buckling strength than their design level.
Estimating Design Resistance of Wrought Balcony Girders
Jung Karel
2017-06-01
Full Text Available The contribution is focused on reliability of balcony girders of a Czech national heritage monument. As preliminary reliability assessment suggests insufficient resistance, a series of nondestructive tests supplemented by a single tensile test are performed and evaluated by the statistical methods. Values of material properties, recommended in standards for historic materials, seem to be overly conservative and it is advised to specify properties of historic metallic materials by tests.
Jensen, Find M.; Branner, K.; Nielsen, Per H. (and others)
2008-03-15
This report presents the setup and result of a full-scale test of a reinforced glass fibre/epoxy box girder used in 34m wind turbine blade. The tests were performed at the Blaest test facility in August 2006. The test is an important part of a research project established in cooperation between Risoe DTU, the National Laboratory for Sustainable Energy at the Technical University of Denmark -, SSP-Technology A/S and Blaest (Blade test centre A/S) and it has been performed as a part of Find Moelholt Jensen's PhD study. This report contains the complete test data for the final test, in which the box girder was loaded until failure. A comprehensive description of the test setup is given. This report deals only with tests and results. There are no conclusions on the data in this report, but references are given to publications, where the data are used and compared with FEM etc. Various kinds of measuring equipment have been used during these tests: acoustic emission, 330 strain gauges, 24 mechanical displacement devices and two optical deformation measuring systems. The mechanical displacement devices measured both global (absolute) and local (relative) deflection and the optical systems measured surface deformation. A prediction was made on the location of the failure of the girder. At this location the majority of the measuring equipment was concentrated. The prediction was proved to be correct and valuable information of the behaviour of the box girder prior to failure was obtained. The experimental investigation consisted of the following load configurations: -Flapwise bending -Torsion Ultrasonic scanning of the box girder was performed before, during and after the test the box girder. This was done to investigate whether the girder was damaged by the load or imperfection (productions defects) growth. (au)
Stress and noises of steel box girders in Sutong Bridge
Xue Tao; Chen Zhijian; Dong Xuewu
2008-01-01
Sutong Bridge is a cable-stayed bridge with a main span of 1 088 m.370 high-precision stress monitoring measured data show that in the process of hoisting the steel box girders,the stress of the main girders is in the fluctuant and complex state and many meteorological factors,such as sunshine radiation,temperature and wind,have important influence on the change of stress of the steel box girders.According to the real-time weather data,the stress data after the process of wavelet denoising from representative measuring points in different weather conditions is picked to estab-lish the stress response brought by meteorological factors with Layered Separation method,thereby basically eliminating the influence of meteorological factors on the stress of main girders,so that accurate and reliable stress data can be got for steel box girders adjustment and cable-tensioned construction control.
Unconventional Bearing Capacity Analysis and Optimization of Multicell Box Girders
Jovan Tepic
2014-01-01
Full Text Available This study deals with unconventional bearing capacity analysis and the procedure of optimizing a two-cell box girder. The generalized model which enables the local stress-strain analysis of multicell girders was developed based on the principle of cross-sectional decomposition. The applied methodology is verified using the experimental data (Djelosevic et al., 2012 for traditionally formed box girders. The qualitative and quantitative evaluation of results obtained for the two-cell box girder is realized based on comparative analysis using the finite element method (FEM and the ANSYS v12 software. The deflection function obtained by analytical and numerical methods was found consistent provided that the maximum deviation does not exceed 4%. Multicell box girders are rationally designed support structures characterized by much lower susceptibility of their cross-sectional elements to buckling and higher specific capacity than traditionally formed box girders. The developed local stress model is applied for optimizing the cross section of a two-cell box carrier. The author points to the advantages of implementing the model of local stresses in the optimization process and concludes that the technological reserve of bearing capacity amounts to 20% at the same girder weight and constant load conditions.
张无畏; 胡腾飞; 陈长胜; 荣浩
2016-01-01
study show that modal analysis re‐sults gained from the three model calculations are basically consistent , the frequency and main girder equivalent mass gained from the combined plate‐beam element model and spatial shell ele‐ment model are approximate ,nevertheless ,the spatial beam element model could not accurately calculate the main girder uniform equivalent mass of the high‐order lateral bending modes .As an exception ,the dynamic performance of the steel box girder cable‐stayed bridge without truss and with open cross section was analyzed independently .The results of the analysis show that the com‐bined plate‐beam element model and spatial shell element model are in good agreement ,but the in‐ertia moment of the main girder uniform equivalent mass under the first order torsional mode gained from the spatial beam element model reveal an error of 9% .T russ has slight influence on the lateral bending frequency of the main girder ,but can improve the vertical bending frequency and torsional frequency of the main girder ,w hich is favorable for the wind resistant performance of the bridge .
Behaviour of parallel girders stabilised with U-frames
Virdi, Kuldeep; Azzi, Walid
2010-01-01
Lateral torsional buckling is a key factor in the design of steel girders. Stability can be enhanced by cross-bracing, reducing the effective length and thus increasing the ultimate capacity. U-frames are an option often used to brace the girders when designing through type of bridges and where...... overhead bracing is not practical. This paper investigates the effect of the U-frame spacing on the stability of the parallel girders. Eigenvalue buckling analysis was undertaken with four different spacings of the U-frames. Results were extracted from finite element analysis, interpreted and conclusions...
Girder Support Scheme for the LCLS Undulator System
Welch, J.
2005-01-31
Differential settlement of the foundation of the LCLS Undulator Hall will cause quadrupoles to move and the electron beam trajectory to distort. The resulting phase errors will decrease the FEL power and require time consuming beam-based alignment sessions to correct. By supporting quadrupoles on girders, with three quadrupoles to a girder, the foundation motion induced phase error between the beam and the X Ray radiation can be reduced by a factor of 5 compared with supporting each quadrupole with a separate column. This comes about because the motions of three quadrupoles on a girder are linearly correlated so their effect on the beam is largely canceled out. Thus a girder support scheme can significantly help to extend the time between required beam based alignments and contribute to a more stable operation of the LCLS FEL beam.
Spatial Effect on Railway Trough Girder with Reactive Powder Concrete%铁路活性粉末混凝土槽形梁的空间作用效应
李志光; 余自若; 王月
2013-01-01
The authors carried out three-dimensional finite element analysis on a 32 m railway trough girder which was made of reactive powder concrete.After working out shear lag coefficients under different load conditions,the rule of shear lag was analyzed,and the results indicated that the shear lag effect in this reactive powder concrete trough girder was larger than that of common concrete girder.Further,the spatial effect on transversal and longitudinal bending moments was analyzed,and the study result on the influence lines of transversal bending moments indicated that,due to the spatial effect,any force on any point of the trough girder would cause transversal bending moment which should not be ignored.Finally,the study result on influence lines of longitudinal bending moments showed that,there was spatial effect on equivalent load in reactive powder concrete trough girder; the closer to the girder end the place was,the more obviously the effect became,which also should not be ignored.Therefore,in the design of this kind of railway girder,the spatial effect on the vicinity of girder end should be taken seriously.%对32 m铁路活性粉末混凝土槽形梁进行三维有限元分析,计算出不同工况下的剪力滞系数,并对剪力滞规律进行分析,研究表明该梁的剪力滞效应较普通混凝土梁更加明显;对其横向和纵向弯矩的空间效应进行分析,对横向弯矩影响线的研究表明,受空间作用的影响,梁上任意一点受力均会在某一截面产生不可忽略的横向弯矩;对纵向弯矩影响线的研究表明空间作用对活性粉末混凝土槽形梁换算荷载的影响在越靠近端部影响越明显,且该影响不可忽略,所以在设计该种梁时需要在靠近端部位置充分考虑空间作用的影响.
桥式起重机轻量化主梁结构模型试验研究%Structural Model Test of Lightweight Girder of Bridge Crane
焦洪宇; 周奇才; 李英; 陈庆樟; 许广举
2015-01-01
针对桥式起重机主梁的轻量化设计方案对主梁强度、静态刚度的影响问题,基于相似理论和弹性静力学,采用方程分析法推导出原型主梁与相似主梁应力场相似的相似准则.依据主梁结构形式及受力特点,设计切实可行的主梁结构模型试验方案,开展轻量化主梁结构模型试验研究.结果表明,轻量化主梁在跨中截面腹板下半部分的弯曲正应力有一定程度的增加,腹板上半部分的弯曲正应力(绝对值)有小幅度下降;轻量化主梁在跨端截面的切应力增加幅度较大;轻量化主梁的最大挠度有所下降.依据《起重机设计规范》对轻量化主梁进行强度和静态刚度校核.在满足主梁强度、静态刚度要求的前提下,周期性去除腹板上的部分材料实现主梁轻量化设计具有一定的可行性.%In order to research the influence of girder's lightweight plan on strength and static rigidity, similarity criterions between prototype girder and similarity girder are derived from equational analysis based on similarity theory and elastostatics. The scheme of structural model test is designed reasonably and the study of structural model test is carried out. Results show that bending normal stress of upper half of web at midspan of lightweight girder increases to some extent and bending normal stress of bottom half of web decreases within a narrow range. Shear stress at the end-span declines by a great margin. The maximum deflection of lightweight girder comes down. The strength and static rigidity of lightweight girder are checked based on design rules for cranes. It is feasible to wipe off some material periodically in order to realize the lightweight design of girder on the premise of satisfying the strength and static rigidity.
Measurements in a container ship of wave-induced hull girder stresses in excess of design values
Andersen, Ingrid Marie Vincent; Jensen, Jørgen Juncher
2014-01-01
This paper describes full-scale measurements of the wave-induced vertical bending moment amidships a 9400 TEU container carrier and focuses on the effect of the hydro-elastic high-frequency vibration on the extreme hogging wave bending moment. One extreme event, where the vertical wave-induced ho......This paper describes full-scale measurements of the wave-induced vertical bending moment amidships a 9400 TEU container carrier and focuses on the effect of the hydro-elastic high-frequency vibration on the extreme hogging wave bending moment. One extreme event, where the vertical wave......-frequency vibrations caused by impulsive loads are observed to be of the same magnitude as the rigid-body wave-induced response and thus acts to double the total vertical bending moment amidships. It was also found that even though the ship is sailing in bow quartering seas, only the 2-node vertical vibration mode...
Hirayama, J.; Sakamoto, M.; Nakao, T.; Koga, N. [Honshu-Shikoku Bridge Authority, Tokyo (Japan)
1996-06-20
Perpendicular construction of bridge girder for a long span suspension bridge, which is to be constructed over the Kurushima Channel, an international route, has been investigated. For the construction of suspension bridge over channels, the overhang construction is generally employed. Bridge girder perpendicular construction, in which unit girder block is lifted from a carrier barge and directly constructed by means of lifting beams located at main cable, is a superb method in terms of cost, time, and safety. It is necessary to stay the carrier barge during the anchoring of girder block and lifting beams. Mooring of the carrier barge is required under a rapid stream, which results in the trouble of under way ships. A propulsion positioning system has been developed for the bridge girder carrier barge, by which the position/propulsion of four thrusters equipped at each corner of the barge can be automatically controlled. Thus, the perpendicular construction of bridge girder has been developed, in which mooring is not required even under the rapid stream. The position of barge can be maintained within a range of {plus_minus}2.5 m even under a rapid stream with a speed of 3 kn. The quick joint can be certainly connected for about one minute in the horizontal movement within {plus_minus}2.5 m and vertical movement within 0.5 m. For this perpendicular construction, the construction time can be shortened to around 16 to 17 minutes, which has been usually taken for three hours. 2 refs., 17 figs., 4 tabs.
Acoustic Emission Monitoring of Multicell Reinforced Concrete Box Girders Subjected to Torsion
Marya Bagherifaez; Arash Behnia; Abeer Aqeel Majeed; Chai Hwa Kian
2014-01-01
Reinforced concrete (RC) box girders are a common structural member for road bridges in modern construction. The hollow cross-section of a box girder is ideal in carrying eccentric loads or torques introduced by skew supports. This study employed acoustic emission (AE) monitoring on multicell RC box girder specimens subjected to laboratory-based torsion loading. Three multicell box girder specimens with different cross-sections were tested. The aim is to acquire AE analysis data indicative fo...
考虑腹板剪切行为的波形钢腹板梁理论模型%Theory Model of Corrugated Steel Web Girder Considering Web Shear Behavior
聂建国; 李法雄
2011-01-01
为研究波形钢腹板剪切变形对波形钢腹板梁受力行为的影响,引入腹板剪切变形转角函数,将波形钢腹板梁的弯曲行为分解为桁架作用和弯曲作用,建立一个能够考虑波形钢腹板剪切变形的波形钢腹板梁理论模型。推导了端部无约束条件下简支波形钢腹板梁在均布荷载和端部约束条件下简支波形钢腹板梁在跨中集中荷载作用下的解析解,采用有限元方法验证了理论模型和解析解的正确性和适用性。研究结果表明：端部约束条件对主梁变形影响很小;波形钢腹板的剪切变形对主梁变形影响显著,在常见波形钢腹板梁桥尺寸范围内,由腹板剪切变形引起的主梁挠度占总挠度的10%～30%。%In order to study the influence of shear deformation of forcing behavior for corrugated steel web,shear rotation function of calculating shear deformation in the web was introduced,a theory model of corrugated steel web girder was presented.In the model,bending behavior of corrugated steel web girder could be divided into truss action and bending action between upper-flange and sub-flange.Then,analytical solutions for the cases of simply-supported corrugated steel web girder without end restraint sustaining under uniform distribution load and simply-supported corrugated steel web girder with end restraint under sustaining mid-span concentrated load were derived,validity and usability of the analytical solution and the model were well proved by finite element method.Results show that the end constraint conditions have little effect on the deformation of the main girder.However,the shear deformation of corrugated steel web has great impact on the deformation of main girder.In the common size ranges of bridge with corrugated steel web girders,the proportion of main girder deflection caused by shear deformation in the web may reach 10% to 30% of total deflection.
Particle deposition in industrial duct bends.
Peters, Thomas M; Leith, David
2004-07-01
A study of particle deposition in industrial duct bends is presented. Particle deposition by size was measured by comparing particle size distributions upstream and downstream of bends that had geometries and flow conditions similar to those used in industrial ventilation. As the interior surface of the duct bend was greased to prevent particle bounce, the results are applicable to liquid drops and solid particles where duct walls are sticky. Factors investigated were: (i) flow Reynolds number (Re = 203 000, 36 000); (ii) particle Reynolds number (10 vertical); and (vii) construction technique (smooth, gored, segmented). Measured deposition was compared with models developed for bends in small diameter sampling lines (Re 20 microm, deposition was slightly greater in the horizontal-to-horizontal orientation than in the horizontal-to-vertical orientation due to gravitational settling. Penetration was not a multiplicative function of bend angle as theory predicts, due to the developing nature of turbulent flow in bends. Deposition in a smooth bend was similar to that in a gored bend; however, a tight radius segmented bend (R0 = 1.7) exhibited much lower deposition. For more gradual bends (3 < R0 < 12), curvature ratio had negligible effect on deposition.
Optimization Method for Girder of Wind Turbine Blade
Yuqiao Zheng
2014-01-01
Full Text Available This paper presents a recently developed numerical multidisciplinary optimization method for design of wind turbine blade. The objective was the highest possible blade weight under specified atmospheric conditions, determined by the design giving girder layer and location parameter. Wind turbine blade on box-section beams girder is calculated by ply thickness, main girder and trailing edge. In this study, a realistic 30 m blade from a 1.2 MW wind turbine model of blade girder parameters is established. The optimization evolves a structure which transforms along the length of the blade, changing from a design with spar caps at the maximum thickness and a trailing edge mass to a design with spar caps toward the tip. In addition, the cross-section structural properties and the modal characteristics of a 62 m rotor blade were predicted by the developed beam finite element. In summary, these findings indicate that the conventional structural layout of a wind turbine blade is suboptimal under the static load conditions, suggesting an opportunity to reduce blade weight and cost.
Preliminary study to facilitate smart structure systems in bridge girders
Kirkpatrick, Thomas C.; Peterson, Danford O.; Rossi, Peter J.; Ray, Laura R.; Livingston, Richard A.
1999-05-01
Sensors are currently available and used to monitor structural performance and loads incurred by bridges already in service. However, there has been limited research concerning the stresses that steel bridge girders endure during transport from the manufacturer to the job site and during the installation process. This paper reports the measured stresses on steel bridge girders during transportation from Lancaster, PA to Hanover, NH and during construction of the Ledyard Bridge on the New Hampshire - Vermont border. Two different monitoring system were developed for this data acquisition in a mobile environment. The first, a fiber optic strain monitoring system, utilizing Bragg grating technology. The second utilized an electrical- resistive foil strain gage network, in conjunction with wireless telemetry equipment. Together, these two systems formed a smart structure system for monitoring bridge girders while confirming the accuracy of data gathered through redundancy. Result conclusively demonstrated for the first time, that stresses in beams during transportation are significant and approach the factor of safety margin in girder design.
Shi, Li; Cai, Yuanqiang; Wang, Peng; Sun, Honglei
2016-07-01
A railway viaduct model consisting of infinite spans of elastically-supported girders carrying a slab track of infinite length is established to investigate the influence of the slabs on the vertical dynamic response of the viaduct, when a moving harmonic point load or a moving sprung wheel is applied. The infinite rail, the discontinuous slabs and girders of identical span lengths are idealized as Euler-Bernoulli beams. The rail fasteners, the cushion layer beneath the slab and the elastic bearings at the girder supports are represented by discretely distributed springs of hysteretic damping. Due to the repetitive nature of the girders, the model can be divided into periodic three-beam units by the span length of the girder, and then solved analytically in the frequency domain using the property of periodic structure. Besides the first natural frequency of the girder with elastic bearings, it is found that the resonance frequency of the slab on the cushion layer has a significant influence on the dynamic response of the track and the girder. Parametric excitations due to the moving wheel periodically passing the discontinuous slabs contribute significantly to the wheel/rail interactions.
Iman MOHSENI; A.R.Khalim RASHID
2012-01-01
Concrete precast multicell box-girder (MCB) bridges combine aesthetics with torsional stiffness perfectly.Previous analytical studies indicate that currently available specifications are unable to consider the effect of the twisting moment (torsional moment) on bridge actions.In straight bridges the effect of torsion is negligible and the transverse reinforced design is governed by other requirements.However,in the case of skewed bridges the effect of the twisting moment should be considered.Therefore,an in-depth study was performed on 90 concrete MCB bridges with skew angles ranging from 0° to 60°.For each girder the bridge actions were determined under the American Association of State Highway and Transportation Officials (AASHTO) live load conditions.The analytical results show that torsional stiffness and live load positions greatly affected the bridges' responses.In addition,based on a statistical analysis of the obtained results,several skew correction factors are proposed to improve the precision of the simplified Henry's method,which is widely used by bridge engineers to predict bridge actions.The relationship between the bending moment and secondary moments was also investigated and it was concluded that all secondary actions increase with an increase in skewness.
Design and test of box girder for a large wind turbine blade
Nielsen, Per Hørlyk; Tesauro, Angelo; Bitsche, Robert
This report is covering the structural design and full scale test of a box girder as a part of the project “Demonstration of new blade design using manufacturing process simulations” supported by the EUDP program. A box girder with a predetermined outer geometry was designed using new inventions......, which create an inner structure in the box girder. With a combination of advanced FEM analysis and the inventions it was possible to reduce the material thickness of the cap by up to 40%. The new design of the box girder was manufactured at SSP Technology A/S, where it was demonstrated...... that the manufacturing process could include the new inventions. Subsequently the box girder was transported to the blade test facility at DTU Wind Energy. A series of test was performed with the blade to investigate the behaviour during loading, and finally the girder was loaded to ultimate failure. The report includes...
Spatial Finite Element Analysis for Dynamic Response of Curved Thin-Walled Box Girder Bridges
Yinhui Wang
2016-01-01
Full Text Available According to the flexural and torsional characteristics of curved thin-walled box girder with the effect of initial curvature, 7 basic displacements of curved box girder are determined. And then the strain-displacement calculation correlations were established. Under the curvilinear coordinate system, a three-noded curved girder finite element which has 7 degrees of freedom per node for the vibration characteristic and dynamic response analysis of curved box girder is constructed. The shape functions are used as the interpolation functions of variable curvature and variable height to accommodate to the variation of curvature and section height. A MATLAB numerical analysis program has been implemented.
Life-Cycle Management Strategy on Steel Girders in Bridges
Kevin K. L. So
2012-01-01
Full Text Available The major problems affecting the service life of bridges are related to various factors such as fatigue-sensitive details, increased service loads, corrosion deterioration, and the lack of proper maintenance. Among them, corrosion deterioration and fatigue damages of structures particularly to steel girder bridges are the most common ones. Bridges of different structural forms, at different locations or under different climates, may suffer from various degrees of deterioration. Steel girders at different positions of a bridge may also suffer from different degrees of damage. How to effectively maintain the bridge asset at a minimal cost and how to predict the time for future works are crucial, particularly when government funding sources become stretched. A comprehensive bridge management framework assisting stakeholders to appropriately and reasonably prioritize their future maintenance-related works in their bridge stocks, such that stakeholders can better allocate the limited resources, is utmost concerned. This paper proposes an integrated life-cycle management (LCM strategy on steel girders in bridges in which corrosion deterioration and fatigue damage prediction models are mapped with girders’ performance conditions. A practical example to demonstrate the applicability of the proposed LCM strategy is also illustrated.
Sakai, F.; Yabe, J.; Ogaki, K.; Sakugawa, K.; Ito, A.; Takeuchi, K.; Tomoda, T. [Kawasaki Heavy Industries, Ltd., Kobe (Japan)
1996-01-20
Rationalization and labor-saving in the construction of bridges are the pending problems arising from the shortage of skilled construction workers, shortened time usable for construction, and demand for lower cost. Under the circumstances, experiment and study were conducted about the PC slab for two- or three-girder bridges. On the assumption of a PC slab located between two main girders, the interval 6 meters long, specimens near the real size were subjected to experiments. Springs were attached to the free sides so that load tests might be conducted under boundary conditions equivalent to those of a finite continuous slab along the direction of the bridge length as in case of a real bridge. It was found that a partial slab model of limited dimensions was usable when a long span slab experiment was necessary. A PC slab, unlike an RC slab, regained its elastic behavior when the load was removed even after the appearance of cracks. Crack producing loads fell within the range which could generally be estimated by calculation, and the PC slab was capable of restoring its original state upon unloading even after the production of cracks. The PC slab, as compared with the RC slab, demonstrated a greater ultimate strength, but the strength was not affected by the size of the prestress. In case of a PC slab on a long span, the bend fracture precedes and the ultimate strength is determined by the bend strength. 9 refs., 9 figs., 5 tabs.
Research on the special lifting devices for steel box girders of Sutong Bridge
Chen Ming; Wu Qihe; Luo Chengbin; Zhou Hanfa
2009-01-01
Sutong Bridge is a cable-stayed bridge with a steel box girder and a main span of 1 088 m. The steel box girder of main span includes five portions: back span large unit, large block of pylon, standard girder, back span closure girder and middle span closure girder. Each back span large unit is fabricated by welding several deck segments together in factory, and is erected by floating crane. As navigational clearance of the main bridge is high, the traditional truss lifting device can' t satisfy the requirement of domestic lifting cranes for this kind of lifting height and weight. Hence, a kind of lighter lifting device for the erection of back span large units was accepted for this bridge. In this paper, the design and use of this lifting device is introduced.The upper structure used lifting gantry to install the standard girder segment by cantilever method. Because the bridge's navigation clearance is high, and the girder segment is wide and heavy, the meteorology and hydrology condition of the bridge district is abominable, and the requirements of long cable girder side pull-in, structure and performance propose high request to the lifting gantry. In this paper, the design and use key point of long cable pull-in angle adjustment device integrate into lifting gantry is introduced.
Design and test of box girder for a large wind turbine blade
Nielsen, Per H.; Tesauro, A.; Bitsche, R. [Technical Univ. of Denmark. DTU Wind Energy, DTU Risoe Campus, Roskilde (Denmark)] [and others
2012-09-15
This report is covering the structural design and full scale test of a box girder as a part of the project ''Demonstration of new blade design using manufacturing process simulations'' supported by the EUDP program. A box girder with a predetermined outer geometry was designed using new inventions, which create an inner structure in the box girder. With a combination of advanced FEM analysis and the inventions it was possible to reduce the material thickness of the cap by up to 40%. The new design of the box girder was manufactured at SSP Technology A/S, where it was demonstrated that the manufacturing process could include the new inventions. Subsequently the box girder was transported to the blade test facility at DTU Wind Energy. A series of test was performed with the blade to investigate the behaviour during loading, and finally the girder was loaded to ultimate failure. The report includes the description of the test setup, the test and an overview over the results from the test performed on the box girder. During the final test the box girder failed at 58 % of the expected ultimate load. Unfortunately, no definite conclusion could be made concerning the failure mechanism. (Author)
S M Mosavi; A Sadeghi Nik
2015-02-01
Applying composites in order to strengthen and renew the infrastructures has globally been accepted. Traditional methods to strengthen the out-of-standard structures are costly, time consuming and requires a lot of labour. Today, new techniques are hired using light and strong substances which also resist against corrosion, known as Carbon Fibre Reinforced Polymer (CFRP) plates. Regarding the high tensile strength and proper module of elasticity, CFRP plates are considered as a suitable alternative to strengthen girders. The behaviour of steel–concrete composite girders being statically loaded and strengthened by CFRP plates in this study. The CFRP plates used in this study have been stuck, with epoxy adhesive, under the tensile sections of three steel girders. The results accompanied with analytical study of moment–curvature and numerical analysis done with ANSYS, show that CFRP plates with epoxy adhesive increases the ultimate loading capacity of steel–concrete composite girder. Plastic stiffness of the girders was also increased.
Buffeting Response of Suspension Bridge Girder with Separate Control Flaps
Huynh, Truc; Thoft-Christensen, Palle
This paper presents the calculation of the root mean square (RMS) response of a suspension bridge using separate control flaps (SCF) in turbulence conditions. It is assumed that the mean wind velocity is not large enough to cause coupled vibrations and that single mode buffeting response...... is of interest. The RMS response is determined on the basis of the equation of motion, which is formulated stochastically according to the wind random turbulence components. It is further assumed that the sum of the motion-induced forces and the buffeting-induced forces from the girder and the flaps is computed...
Design of bridge crane girder strain acquisition system based on virtual instrument
Wenxue LIU
Full Text Available Girder is an important part of the bridge crane, which is also the main force element. In order to prevent accidents, it is necessary to collect the bridge crane girder stress data to analyse the fatigue life. This paper constructs a bridge crane girder strain acquisition system. The hardware system consists of sensors, connectors, data acquisition cards, wireless data transmission groups, POE power and host computer. The software system consists of NI MAX to interface with the computer's NI hardware and software resources,and LabVIEW programming to display and storage the girder strain data. Through this system, positions and working days strain data acquisition for the 50/10 t bridge crane girder gets the key positions strain data. The results show that the girder strain data acquisition system runs stably, channel signals of acquisition task transmit accurately, and the terminal data stores competely, meeting the detection requirements, which provides an important data support for the subsequent fatigue analysis and accurate remaining service life prediction of the crane girder.
EFFECTIVE STIFFNESS METHOD FOR CALCULATING DEFLECTION OF CORRUGATED WEB GIRDER%波形钢腹板梁变形计算的有效刚度法
聂建国; 李法雄; 樊健生
2012-01-01
By introducing a shear rotation function accounting for the shear deformation in the webs, the paper presents a beam theory model of corrugated web girder, where the flexural behavior of corrugated web girder is modeled as the combination of truss action and bending action between upper flange and lower flange. Then analytical solutions for simply supported corrugated steel web girders and cantilever corrugated steel web girders are derived under uniformly distributed load and concentrated load, and the analytical solutions are well verified through a comparison with FEM results. In order to determine the deformation of corrugated web girders for the purpose of practical design, a simplified design method to calculate the deflection of corrugated web girders considering web shear deformation is presented by introducing an importance parameter. The deflections calculated by this method agree well with those obtained from experiments. According to the comparison of calculated deflections among different design methods for corrugated web girders, the simplified method presented in this study has good accuracy and is convenient to use.%为研究波形钢腹板剪切变形对波形钢腹板梁受力行为的影响，引入腹板剪切变形转角函数，将波形钢腹板梁的弯曲行为分解为桁架作用和弯曲作用，建立一个能够考虑波形钢腹板剪切变形的波形钢腹板梁理论模型，推导了简支和悬臂波形钢腹板梁在不同类型荷载作用下的变形解析解，采用有限元方法验证了理论模型和解析解的正确性和适用性。根据变形等效原理，引入重要影响参数对波形钢腹板梁的变形解析解进行简化，提出了考虑腹板剪切行为的波形钢腹板梁变形简化计算方法——有效刚度法。用该文提出的有效刚度法计算波形钢腹板梁在正常使用极限状态下的变形值和试验结果吻合良好，为波形钢腹板梁在正常使用极限状态下的
Research on temperature field and temperature stress of prestressed concrete girders
Chen Cheng
2011-02-01
Full Text Available This paper introduces the establishment and simplification of the temperature field and the general calculation method of temperature stress of the prestressed concrete box girders. Three kinds of sunshine temperature gradient models were loaded to a real bridge respectively, and got stress and displacement curves. Research data of several prestressed concrete box girders were selected from different regions of China to compare the relative error of the calculated and measured value. We indicate that the study of temperature field and thermal stress of prestressed concrete box girders is necessary, and will help engineers to solve the problem in structure design.
Choi, H. J.; Lee, S. B.; Lee, H. G.; Y Back, S.; Kim, S. H.; Kang, H. S.
2017-07-01
Several parts that comprise the large scientific device should be installed and operated at the accurate three-dimensional location coordinates (X, Y, and Z) where they should be subjected to survey and alignment. The location of the aligned parts should not be changed in order to ensure that the electron beam parameters (Energy 10 GeV, Charge 200 pC, and Bunch Length 60 fs, Emittance X/Y 0.481 μm/0.256 μm) of PAL-XFEL (X-ray Free Electron Laser of the Pohang Accelerator Laboratory) remain stable and can be operated without any problems. As time goes by, however, the ground goes through uplift and subsidence, which consequently deforms building floors. The deformation of the ground and buildings changes the location of several devices including magnets and RF accelerator tubes, which eventually leads to alignment errors (∆X, ∆Y, and ∆Z). Once alignment errors occur with regard to these parts, the electron beam deviates from its course and beam parameters change accordingly. PAL-XFEL has installed the Hydrostatic Leveling System (HLS) to measure and record the vertical change of buildings and ground consistently and systematically and the Wire Position System (WPS) to measure the two dimensional changes of girders. This paper is designed to introduce the operating principle and design concept of WPS and discuss the current situation regarding installation and operation.
Research on the stiffening girder erection sequence of three-tower suspension bridge
Zheng Runqing; Luo Xiheng
2012-01-01
Compared to the conventional two-tower suspension bridge, the three-tower suspension bridge has obviously different characteristics in structural performance because of the extra middle tower and main span. The construction sequence for the stiffening girder is significantly different between the three-tower suspension bridge and the two-tower suspension bridge. The tangential angle of the main cable is one of the controlling factors of the stiffening girder erection stage for a suspension bridge. According to 5 feasible cases for the stiffening girder erection scheme in Taizhou Bridge, the research about the tangential angle in each case mentioned above was made, and some factors that should be taken into account for the erection scheme of stiffening girder were pointed out.
运架一体式架梁机隧道架梁技术%Tunnel Girder Skill of Transported Frame Integrated Girder Machine
乐锋
2013-01-01
本文介绍了运架一体式架梁机的组成结构，施工前的各项准备工作。本文详细阐述了运架一体式架梁机进出隧道架设第一孔或最后一孔双线整孔预制箱梁的施工技术。%This article describes the structure composition of the transported frame integrated girder machine and the preparatory work before construction. This paper describes the double track prefabricated box girder construction technology of entering and going out the first or last hole of tunnel for the transported frame integrated girder machine.
M B ANOOP; K BALAJI RAO
2016-08-01
A methodology for performance evaluation of reinforced concrete bridge girders in corrosive environments is proposed. The methodology uses the concept of performability and considers both serviceability- and ultimate-limit states. The serviceability limit states are defined based on the degree of cracking (characterized by crack width) in the girder due to chloride induced corrosion of reinforcement, and the ultimate limit states are defined based on the flexural load carrying capacity of the girder (characterized in terms of rating factor using the load and resistance factor rating method). The condition of the bridge girder is specified by the assignment of a condition state from a set of predefined condition states. Generally, the classification of condition states is linguistic, while the condition states are considered to be mutually exclusive and collectivelyexhaustive. In the present study, the condition states of the bridge girder are also represented by fuzzy sets to consider the ambiguities arising due to the linguistic classification of condition states. A non-homogeneous Markov chain (MC) model is used for modeling the condition state evolution of the bridge girder with time. The usefulness of the proposed methodology is demonstrated through a case study of a severely distressed beam of the Rocky Point Viaduct. The results obtained using the proposed approach are compared with those obtained using conventional MC model. It is noted that the use of MC with fuzzy states leads to conservative decision making for the problem considered in the case study.
Gi-Ha Eom
2017-03-01
Full Text Available A recent trend in bridge construction has been the optimization of the cost-to-performance ratio. The most effective way to optimize the cost-to-performance ratio is to maximize the efficiency of the superstructure. Currently, many bridge engineers and designers favor two- or three- girder plate superstructures, due to their cost advantages. However, research on the performance enhancements of the I-type girder in two- or three- girder plate bridges is lacking. One of the most important performance improvement technologies for the I-type girder is the “preflex” method. In the preflex method, the specimen is inverted during the construction process to apply prestressed cambering to the specimen by using self-weight. However, a problem with the preflex construction method is difficulty with inverting the girder/plate system during the concrete curing process. Therefore, a new inverting system called Turn-Over (TO wheel was proposed. Using TO wheels, wider variations to the I-type girder design can be achieved. Using this TO construction method, various cross sectional designs of girder plate systems can be considered due to its easiness in inverting the girder/plate system. In this study, the location of concrete confinement sections between the steel I-beams and concrete plates was varied in an I-girder cross-sectional design. Design parameters included effective height, flange thickness, flange width, confining concrete section width, etc. From this study, the optimum cross-sectional design of the I-girder/concrete plate system was achieved. Then, a single 20 m TO girder/plate system and two 20 m TO girder bridges were constructed and tested to evaluate their performance. From the test, failure behavior, load carrying capacity, crack pattern, etc., are obtained. The results are discussed in detail in this paper.
2002-01-01
A Japanese team has found a way to bend and shape silicon substrates by growing a thin layer of diamond on top. The technique has been proposed as an alternative to mechanical bending, which is currently used to make reflective lenses for X-ray systems and particle physics systems (2 paragraphs).
Occipital bending in schizophrenia.
Maller, Jerome J; Anderson, Rodney J; Thomson, Richard H; Daskalakis, Zafiris J; Rosenfeld, Jeffrey V; Fitzgerald, Paul B
2017-01-01
To investigate the prevalence of occipital bending (an occipital lobe crossing or twisting across the midline) in subjects with schizophrenia and matched healthy controls. Occipital bending prevalence was investigated in 37 patients with schizophrenia and 44 healthy controls. Ratings showed that prevalence was nearly three times higher among schizophrenia patients (13/37 [35.1%]) than in control subjects (6/44 [13.6%]). Furthermore, those with schizophrenia had greater normalized gray matter volume but less white matter volume and had larger brain-to-cranial ratio. The results suggest that occipital bending is more prevalent among schizophrenia patients than healthy subjects and that schizophrenia patients have different gray matter-white matter proportions. Although the cause and clinical ramifications of occipital bending are unclear, the results infer that occipital bending may be a marker of psychiatric illness.
Jensen, Find M.; Branner, K.; Nielsen, Per H. (and others)
2008-05-15
This report presents the setup and result from three static full-scale tests of the reinforced glass fiber/epoxy box girder used in a 34m wind turbine blade. One test was without reinforcement one with cap reinforcement and the final test was with rib reinforcement. The cap reinforcement test was part of a proof of concept investigation for a patent. The tests were performed at the Blaest test facility in August 2007. The tests are an important part of a research project established in cooperation between Risoe National Laboratory for sustainable energy--Technical university of Denmark, SSP-Technology A/S and Blaest (Blade test centre A/S) and it has been performed as a part of Find Moelholt Jensen's PhD thesis. This report is the second data report containing the complete test data for the three full-scale tests. This report deals only with the test methods and the obtained results, no conclusions are drawn. These can be found in papers and patent referenced in the data report. Various kinds of measuring equipment have been used during these tests: acoustic emission, force transducers, strain gauges and optical deformation measuring system (DIC). The experimental investigation consisted of the following tests: 1) Flapwise bending with no reinforcement 2) Flapwise bending with wire reinforcements 3) Flapwise bending with rib reinforcements. (au)
Seismic response of skewed RC box-girder bridges
Ahmed Abdel-Mohti; Gokhan Pekcan
2008-01-01
It is critical to ensure the functionality of highway bridges after earthquakes to provide access to important facilities.Since the 1971 San Fernando earthquake,there has been a better understanding of the seismic performance of bridges.Nonetheless,there are no detailed guidelines addressing the performance of skewed highway bridges.Several parameters affect the response of skewed highway bridges under both service and seismic loads which makes their behavior complex.Therefore,there is a need for more research to study the effect of skew angle and other related factors on the performance of highway bridges.This paper examines the seismic performance of a three-span continuous concrete box girder bridge with skew angles from 0 to 60 degrees,analytically.Finite element (FE) and simplified beam-stick (BS) models of the bridge were developed using SAP2000.Different types of analysis were considered on both models such as:nonlinear static pushover,and linear and nonlinear time history analyses.A comparison was conducted between FE and BS,different skew angles,abutment support conditions,and time history and pushover analysis.It is shown that the BS model has the capability to capture the coupling due to skew and the significant modes for moderate skew angles.Boundary conditions and pushover load profile are determined to have a major effect on pushover analysis.Pushover analysis may be used to predict the maximum deformation and hinge formation adequately.
Kang Jae-Yoon
2015-01-01
Full Text Available The dynamic flexural behaviour of the railway bridge is influenced by its torsional behaviour. Especially, in the case of girder railway bridges, the dynamic response tends to amplify when the natural frequency in flexure (1st vibration mode is close to that in torsion (2nd vibration mode. In order to prevent such situation, it is necessary to adopt a flexural-to-torsional natural frequency ratio larger than 120%. This study proposes a solution shifting the natural frequency in torsion to high frequency range and restraining torsion by installing concrete panels on the bottom flange of the girder so as to prevent the superposition of the responses in the girder bridge. The applicability of this solution is examined by finite element analysis of the shift of the torsional natural frequency and change in the dynamic response according to the installation of the concrete panels. The analytical results for a 30 m-span girder railway bridge indicate that installing the concrete panels increases the natural frequency in torsion by restraining the torsional behaviour and reduces also the overall dynamic response. It is seen that the installation of 100 mm-thick concrete panels along a section of 4 m at both extremities of the girder can reduce the dynamic response by more than 30%.
Yue Zheng
2015-01-01
Full Text Available This paper aims to evaluate the impact interaction between the abutment and the girder subjected to nonuniform seismic excitation. An impact model based on tests is presented by taking material properties of the backfill of the abutment into consideration. The conditional simulation is performed to investigate the spatial variation of earthquake ground motions. A two-span continuous steel box girder bridge is taken as the example to analyze and assess the pounding interaction between the abutment and the girder. The detailed nonlinear finite element (FE model is established and the steel girder and the reinforced concrete piers are modeled by nonlinear fiber elements. The pounding element of the abutment is simulated by using a trilinear compression gap element. The elastic-perfectly plastic element is used to model the nonlinear rubber bearings. The comparisons of the pounding forces, the shear forces of the nonlinear bearings, the moments of reinforced concrete piers, and the axial pounding stresses of the steel girder are studied. The made observations indicate that the nonuniform excitation for multisupport bridge is imperative in the analysis and evaluation of the pounding effects of the bridges.
Xu Chen
2015-01-01
Full Text Available The steel-concrete composite girder has been usually applied in the bridge and building structures, mostly consisting of concrete slab, steel girder, and shear connector. The current fatigue damage assessment for the composite girder is largely based on the strain values and concrete crack features, which is time consuming and not stable. Hence the vibration-based fatigue damage assessment has been considered in this study. In detail, a steel-steel fiber reinforced concrete (SFRC composite girder was tested. The steel fiber reinforced concrete is usually considered for dealing with the concrete cracks in engineering practice. The composite girder was 3.3m long and 0.45m high. The fatigue load and impact excitation were applied on the specimen sequentially. According to the test results, the concrete crack development and global stiffness degradation during the fatigue test were relatively slow due to the favourable performance of SFRC in tension. But on the other hand, the vibration features varied significantly during the fatigue damage development. Generally, it confirmed the feasibility of executing fatigue damage assessment of composite bridge based on vibration method.
Acoustic emission monitoring of multicell reinforced concrete box girders subjected to torsion.
Bagherifaez, Marya; Behnia, Arash; Majeed, Abeer Aqeel; Hwa Kian, Chai
2014-01-01
Reinforced concrete (RC) box girders are a common structural member for road bridges in modern construction. The hollow cross-section of a box girder is ideal in carrying eccentric loads or torques introduced by skew supports. This study employed acoustic emission (AE) monitoring on multicell RC box girder specimens subjected to laboratory-based torsion loading. Three multicell box girder specimens with different cross-sections were tested. The aim is to acquire AE analysis data indicative for characterizing torsion fracture in the box girders. It was demonstrated through appropriate parametric analysis that the AE technique could be utilized to effectively classify fracture developed in the specimens for describing their mechanical behavior under torsion. AE events localization was presented to illustrate the trend of crack and damage propagation in different stages of fracture. It could be observed that spiral-like patterns of crack were captured through AE damage localization system and damage was quantified successfully in different stages of fracture by using smoothed b-value analysis.
Acoustic Emission Monitoring of Multicell Reinforced Concrete Box Girders Subjected to Torsion
Marya Bagherifaez
2014-01-01
Full Text Available Reinforced concrete (RC box girders are a common structural member for road bridges in modern construction. The hollow cross-section of a box girder is ideal in carrying eccentric loads or torques introduced by skew supports. This study employed acoustic emission (AE monitoring on multicell RC box girder specimens subjected to laboratory-based torsion loading. Three multicell box girder specimens with different cross-sections were tested. The aim is to acquire AE analysis data indicative for characterizing torsion fracture in the box girders. It was demonstrated through appropriate parametric analysis that the AE technique could be utilized to effectively classify fracture developed in the specimens for describing their mechanical behavior under torsion. AE events localization was presented to illustrate the trend of crack and damage propagation in different stages of fracture. It could be observed that spiral-like patterns of crack were captured through AE damage localization system and damage was quantified successfully in different stages of fracture by using smoothed b-value analysis.
The Design and Construction of 160T Girder Station%160T提梁站设计与施工
邓洪钧
2012-01-01
Guangshen Coastal Expressway Shenzhen Girder Station uses the steel pipe piles combined with Bailey girders in the construction.The headroom of the girder stations and the cast-in-place box girder is 7m, and the span is 17.25m. This paper makes a brief description of the installation method of the girder station% 广深沿江高速深圳段提梁站施工采用钢管桩结合贝雷梁形式。提梁站与现浇箱梁净空高度7m，跨度为17.25m，文章就提梁站的安装方法作简要介绍。
沈耀海
2011-01-01
结合西部某新建火车站进站人行天桥工程实例，分析了设计和施工的多种控制条件，论证了主梁采用钢箱梁结构的合理性．通过有限元分析和动力特性计算可知，结构设计的控制因素为竖向自振频率，采用中墩与主梁固结的连接方式可以有效地调整结构竖向自振频率．%Based on the project case of one pedestrian bridge in one new constructed railway station at west China, many controlled conditions are analyzed about structural design and engineering construction, and the rationalitles of steel box girder bridge adopted in the design are also demonstrated. It is learned from finite - element analysis and dynamic characteristics calculation that the control factor of structural design is vertical vibration frequency, which can be improved effectively by means of fixed connection between central pier and steel box girder.
Closure technique for the hybrid girder cable stayed bridge of Edong Bridge
Liu Minghu; Tan Hao; Xu GuoPing; Zhao Canhui
2012-01-01
Based on Edong Yangtze River Bridge, which is the second longest hybrid girder cable stayed bridge with 926 m long main span, the influencing factors and crucial techniques of the main span closure method for long span hybrid girder cable stayed bridge are studied. After theoretical analysis, numerical evaluation and practical test, the loading assistant closure method is employed in Edong Yangtze River Bridge. The loading assistant closure method, with better thermal adaptability and less influence on bridge line and the forced status, can meet the requirements of the unstressed state control method. Based on the mentioned advantages, the loading assistant closure method is applicable to long span hybrid girder cable stayed bridges. The conclusion can provide a reference for the further design of the similar brid~es.
A Simple Technique to Determine Interface Slip of Stud Connected SCC Girders
Rajasankar J.
2012-01-01
Full Text Available A simple technique is proposed to compute interface slip of stud connected steel-concrete composite (SCC girders based on the results of a flexure test. The technique makes use of relative longitudinal displacement of the concrete slab and steel beam to calculate the interface slip. In the flexure test of a SCC girder, a cost-effective instrumentation arrangement consisting of mechanical dial gauges is used to measure the relative longitudinal displacement. Responses measured from experiments on SCC girders conducted by the authors are used for numerical implementation and validation of the technique. Alternatively, interface slip is also evaluated by applying an analytical model which is based on first principles of mechanics. The values of interface slip computed by using the proposed technique are found to have close correlation with those of the analytical model. The effect of edge restraint on slip due to friction between steel and concrete is also studied
Lateral static and dynamic characteristics of thin-walled box girder
CAN Yan-an; ZHOU Guang-chun
2009-01-01
To analyze the static and dynamic behaviors of the thin-walled box girder in its lateral webs in consideration of shear lag effect and shear deformation, an approach based on the minimum potential principle is introduced in this paper. Both static and dynamic response equations as well as the corresponding natural boundary conditions of the box girder are deduced. Meanwhile, three generalized displacement functions:w(x), U(x) and 0(x) are employed and their differences in the calculus of variation are quantitatively investigated. The comparison of finite shell element results with analytical results of calculation examples validates the feasibility of the proposed approach.
Welding of girders to insert plates of composite steel-concrete structure of tower in Kuwait
A. Lisiecki; J. Szlek; A. Klimpel
2007-01-01
Purpose: A study of influence of preheating and MMA welding technique of tee-joints of plate girders to insert plates of a composite steel-concrete structure of the telecommunication tower, on the properties and quality of the concrete in the region of the insert plate has been carried out.Design/methodology/approach: Studies of thermo-mechanical phenomena during manual arc welding MMA of tee-joints between plate girders and insert plates were carried out to identify possible sources of the ...
Welding of girders to insert plates of composite steel-concrete structure
A. Klimpel; A. Lisiecki; J. Szlek
2007-01-01
Purpose: of this paper: A study of influence of preheating and MMA welding technique of tee-joints of plate girders to insert plates of a composite steel-concrete structure of the telecommunication tower, on the properties and quality of the concrete in the region of the insert plate has been carried out.Design/methodology/approach: Studies of thermo-mechanical phenomena during manual arc welding MMA of tee-joints between plate girders and insert plates were carried out to identify possible s...
连续箱梁的日照温差应力计算研究%Study on Calculation of Sunshine Thermal Stress in Continuous Box-girders
陈权; 王丽娟; 张元海; 诸昌钤
2009-01-01
According to the harmonious condition of deformation and the assumption of plane section, the general formula for calculating sunshine thermal stress of continuous box girders was derived. Then based on the existing experimental results and the modes of sunshine thermal gradients in the present code for design of railway and highway bridges, the practical calculating formula of thermal stress was presented. The method and formula for calculating secondary thermal bending moment were provided tnnzekew continuous box girders based on the three-moment equation of skew continuous beam. The corresponding programmaing was fulfilled. The thermal stresses in figh and skew continuous box girders were calculated through engineering practice and good agreement was achieved compared with those of ANSYS calculation. The longitudinal distribution pattern of the thermal stress in continuous box girder bridges was ascertained. It is put forward that (1) much attention should be paid to the checking calculation for nonnal stress and crack resistance at midspan cross-section of central span in the design of prestrssed concrete continuous box girder bridges; (2) the checking calculation for crack resistance of inclined cross -section near gravity axis in internal support area should also be treated seriously.%根据变形协调条件及平截面假定,首先推导了连续箱梁日照温差总应力的一般公式,并针对试验观测资料及我国铁路桥梁和公路桥梁设计规范中的不同日照温差梯度模式,给出了温度应力的实用计算公式.为了能够进一步应用于斜交连续箱梁,以斜交连续梁的三力矩方程为基础,给出了温度次弯矩的计算方法及公式.编制了相应温度应力分析程序,结合工程实例分别对正交和斜交连续箱梁的温度应力进行了计算分析,并与ANSYS有限元计算结果进行对比.通过分析连续箱梁日照温差应力沿梁跨方向的分布规律,提出在设计预应力混凝
CERN PhotoLab
1981-01-01
During 1981, the PS South-Hall, no longer used for physics experiments, was cleared for the installation of the Low Energy Antiproton Ring, LEAR. In October 1981, 3 of the 4 bending magnet quadrants were in place, this is one of them.
Effect of material uncertainties on dynamic response of segmental box girder bridge
Suchart Limkatanyu
2007-11-01
Full Text Available The main objective of this paper was to investigate the effect of material uncertainties on dynamic response of segmental box girder bridge subjected to a moving load, in this case a rapid passing trains. Literatures concerned with the design of segmental box girder bridge, the application of finite element analysis to model the segmental box girder bridge, and the minimum requirement for structural conditions of the bridge were described and discussed in detail. A series of finite element analysis was carried out using SAP2000 Nonlinear software. The effect was investigated by varying the Modulus of Elasticity by 5%, 10% and 15%. The results were then compared with the case of assumed uniform property which had already been checked for model accuracy using the Standard prEN 1991-2. The results showed that, for the uniform case, the dynamic responses of the bridge gave the highest response at the resonance speed. When considering the non-uniform material properties (non-uniform case, the effect of material uncertainties appeared to have an effect on both displacement and acceleration responses. Nonetheless, the dynamic factor provided in the design code was sufficient for designing the segmental box girder bridge with either uniform or non-uniform material properties for the train speeds considered in this study.
Jiao, Pengcheng; Borchani, Wassim; Hasni, Hassene; Lajnef, Nizar
2017-08-01
This study develops a novel buckling-based mechanism to measure the thermal response of prestressed concrete bridge girders under continuous temperature changes for structural health monitoring. The measuring device consists of a bilaterally constrained beam and a piezoelectric polyvinylidene fluoride transducer that is attached to the beam. Under thermally induced displacement, the slender beam is buckled. The post-buckling events are deployed to convert the low-rate and low-frequency excitations into localized high-rate motions and, therefore, the attached piezoelectric transducer is triggered to generate electrical signals. Attaching the measuring device to concrete bridge girders, the electrical signals are used to detect the thermal response of concrete bridges. Finite element simulations are conducted to obtain the displacement of prestressed concrete girders under thermal loads. Using the thermal-induced displacement as input, experiments are carried out on a 3D printed measuring device to investigate the buckling response and corresponding electrical signals. A theoretical model is developed based on the nonlinear Euler-Bernoulli beam theory and large deformation assumptions to predict the buckling mode transitions of the beam. Based on the presented theoretical model, the geometry properties of the measuring device can be designed such that its buckling response is effectively controlled. Consequently, the thermally induced displacement can be designed as limit states to detect excessive thermal loads on concrete bridge girders. The proposed solution sufficiently measures the thermal response of concrete bridges.
Reliability Assessment for PSC Box-Girder Bridges Based on SHM Strain Measurements
Chuang Chen
2017-01-01
Full Text Available A reliability assessment method for prestressed concrete (PSC continuous box-girder bridges based on structural health monitoring (SHM strain measurements was proposed. First, due to the fact that measured strain was compositive and the variation periods of its components were different, a series of limit state equations under normal use limit state were given. Then, a linear fitting method was used to determine the relationship between the ambient temperature and the measured strain, which was aimed at extracting the vehicle load effect and the temperature load effect from the measured strain. Finally, according to the equivalent normalization method, the load effects unsatisfying the normal distribution by probability density function fitting were transformed, and the daily failure probabilities of monitored positions were calculated for evaluating the safety state of the girder. The results show that (1 the top plate of the box girder is more sensitive than the bottom plate to the high temperature, (2 the daily and seasonal strain variations induced by uniform temperature reveal an inconsistent tendency to the seasonal variation for mid-span cross sections, and (3 the generalized extreme value distribution is recommended for temperature gradient stress and vehicle induced stress fitting for box-girder bridges.
Numerical Investigation on Aerodynamic Force of Streamlined Box Girder with Uniform Air Suction
Tang Ke
2014-06-01
Full Text Available In the present study, the flow around a streamlined box girder with uniform air suction has been investigated numerically. Two-dimensional incompressible unsteady Reynolds averaged Navier-Stokes (URANS equations are solved in conjunction with the SST k −ω turbulence model in simulations. Taking the Great Belt Bridge girder as an example, cases of different suction positions on the girder section were discussed. The effect of the suction ratio and the angle of attack (AOA of wind also were investigated. The result showed that the aerodynamic drag force was influenced by the uniform suction through either upper surface or lower surface of the box girder. The larger the suction ratio was, the more the drag-reducing could be. The suction position and AOA had a comprehensive effect on the drag force. The vortex shedding frequency was also affected by air suction. For the aerodynamic lift force and moment, air suction showed no obvious influence. If necessary, using a combined suction scheme to reduce the aerodynamic drag force or to control the flow wake would be more efficient in engineering design.
Maintained ship hull girder ultimate strength reliability considering corrosion and fatigue
Hu, Yong; Cui, W.; Pedersen, Preben Terndrup
2004-01-01
The prupose of this paper is to propose a methodology to assess the time-variant ultimate strength of ship hull girder under the degradations of corrosion and fatigue. The effects of fatigue cracks on the tensile and compressive residual ultimate strength of stiffened panels and unstiffened plate...
Deflection monitoring for a box girder based on a modified conjugate beam method
Chen, Shi-Zhi; Wu, Gang; Xing, Tuo
2017-08-01
After several years of operation, a box girder bridge would commonly experience excessive deflection, which endangers the bridge’s life span as well as the safety of vehicles travelling on it. In order to avoid potential risks, it is essential to constantly monitor the defection of box girders. However, currently, the direct deflection monitoring methods are limited by the complicated environments beneath the bridges, such as rivers or other traffic lanes, which severely impede the layouts of the sensors. The other indirect deflection monitoring methods mostly do not thoroughly consider the inherent shear lag effect and shear deformation in the box girder, resulting in a rather large error. Under these circumstances, a deflection monitoring method suiting box girders is proposed in this article, based on the conjugate beam method and distributed long-gauge fibre Bragg grating (FBG) sensor. A lab experiment was conducted to verify the reliability and feasibility of this method under practical application. Further, the serviceability under different span-depth ratios and web thicknesses was examined through a finite element model.
Sivak, David Alexander
DNA bending elasticity on length scales of tens of basepairs is of critical importance in numerous biological contexts. Even the simplest models of DNA bending admit of few simple analytic results, thus there is a need for numerical methods to calculate experimental observables, such as distance distributions, forces, FRET efficiencies, and timescales of particular large-scale motions. We have implemented and helped develop a coarse-grained representation of DNA and various other covalently-linked groups that allows simple calculation of such observables for varied experimental systems. The simple freely-jointed chain (FJC) model and extremely coarse resolution proved useful in understanding DNA threading through nanopores, identifying steric occlusion by other parts of the chain as a prime culprit for slower capture as distance to the pore decreased. Enhanced sampling techniques of a finer resolution discrete wormlike chain (WLC) model permitted calculation of cyclization rates for small chains and identified the ramifications of a thermodynamically-sound treatment of thermal melts. Adding treatment of double-stranded DNA's helical nature and single-stranded DNA provided a model system that helped demonstrate the importance of statistical fluctuations in even highly-stressed DNA mini-loops, and allowed us to verify that even these constructs show no evidence of excitation-induced softening. Additional incorporation of salt-sensitivity to the model allowed us to calculate forces and FRET efficiencies for such mini-loops and their uncircularized precursors, thereby furthering the understanding of the nature of IHF binding and bending of its recognition sequence. Adding large volume-excluding spheres linked to the ends of the dsDNA permits calculation of distance distributions and thus small-angle X-ray scattering, whereby we demonstrated the validity of the WLC in describing bending fluctuations in DNA chains as short as 42 bp. We also make important connections
刘朵; 张建东; 刘钊
2013-01-01
The steel truss-web and pre-stressed concrete composite girder bridge consists of two parts :steel truss-web and top-and-bottom concrete board .Because the distribution of shear deformation is non-uniform ,the composite box girder bridge has the obvious shear-lag effect under longitudinal bending .Taking a steel truss-web and pre-stressed concrete composite girder bridge for example ,the shear-lag effect and the distribution law of effective width are analyzed by the fi-nite element model of space ,and the effects of top-and-bottom thickness and steel pipe thickness on the shear-lag effect are studied here so as to provide references for the similar design in the future .%钢桁腹预应力混凝土组合梁桥在截面形式上采用桁式腹杆和混凝土顶底板，由于剪切变形的不均匀性，使得组合箱梁在纵向弯曲时产生较为明显的剪滞效应。以某钢桁腹混凝土组合梁桥为例，利用空间实体模型分析了剪滞效应和有效宽度分布规律，并研究了顶底板厚度及钢管壁厚对剪滞效应的影响，为今后同类桥型的设计提供参考。
A multipurpose tissue bending machine.
Vesely, I; Boughner, D R
1985-01-01
A unique tissue bending machine was developed to test the bending properties of normal and bioprosthetic heart valve material. It can be operated in air or in a tissue bath and can measure bending torques with an accuracy in excess of 1.0 microN m. Three contrasting substances were tested to compare their stiffness and to demonstrate the machine.
EXPERIMENTAL STUDY OF 3-D TURBULENT BEND FLOWS IN OPEN CHANNEL
LIU Yue-qin; ZHENG Shao-wen; WU Qiang
2005-01-01
A generalized bend flow model, treating a 90° single bend and 60° continuous bends, was designed to quantitatively describe 3-D turbulence mechanism of circulating not-fully-developed flow in open channels with bends.The 3-D fluctuating velocities of turbulent flow were measured and analyzed with a 3-D acoustic-Doppler velocimeter.Formula for 3-D turbulent intensity was derived using the dimension analysis approach.Expressions of vertical turbulent-intensity distributions were obtained with the multivariant-regression theory, which agree with experiment data.Distributions of turbulent intensity and turbulent stress were characterized, and their relationships were concluded.In the bend-turbulent-flow core region, longitudinal and lateral turbulent-intensity distributions are coincident with linear distribution, but in near-wall region are coincident with the Gamma distribution.Vertical turbulent intensity distributions are coincident with the Rayleigh distribution.Herein, it is concluded that the bend turbulence is anisotropic.
Strengthening and repair of steel-concrete composite girders using CFRP laminates
Tavakkolizadeh, Mohammadreza
The use of advanced composite materials for rehabilitation and repair of deteriorating infrastructure has been embraced worldwide. The conventional techniques for strengthening of substandard bridges are costly, time consuming and labor intensive. A total of 38 specimens made of steel and carbon fibers were prepared and tested to investigate the possibility of galvanic corrosion. Two simulated aggressive environments and three different amounts of epoxy coating were used. Potentiodynamic polarization and galvanic corrosion tests were conducted. The results of the experiments showed the existence of galvanic corrosion however the rate of such corrosion could be decreased significantly by epoxy coating. A total of 21 specimens made of S 5 x 10 A36 steel beams were prepared and tested to determine the effectiveness of CFRP patch on fatigue life of notched beam. The results showed that not only CFRP patch tends to extend the fatigue life of a detail more than three times, but also it decreases the crack growth rate significantly. To investigate the effectiveness of the epoxy bonded CFRP sheets in repair and retrofit of composite girders, a total of six large-scale steel-concrete composite girders made of W 14 x 30 A36 steel beam and 7.5 cm. thick by 91 cm wide concrete slab were prepared and tested. Three different numbers of CFRP layers and three different damage level in Range were considered. The retrofitting test results showed that epoxy bonded CFRP Sheet increased the ultimate load carrying capacity of composite girders and the behavior can be conservatively predicted by traditional methods. The repair test results showed that epoxy bonded CFRP sheet could restore the ultimate load carrying capacity and stiffness of damaged steel-concrete composite girders. The ultimate capacity of the repaired beam was predicted by traditional methods of analysis of steel-concrete composite beams, which was fairly conservative. Guidelines and procedures for design of Steel
叶华文; T. Ummenhofer; 强士中
2009-01-01
Bonding Prestressed carbon fiber reinforcement polyester (CFRP) plate is a promising technique to strengthen steel member damaged by fatigue. First, a modification of Paris' equation was used to analyze the crack propagation of the steel member strengthened by CFRP plate. Four-point bending fatigue test of pre-cracked steel girder strengthened with prestressed CFRP plates was also conducted to investigate the flexural fatigue performance of reinforced steel girder. In the end a simplified calculation and design method was also presented to estimate the re-quired prestress preliminary to stop the propagation of fatigue cracks. The result shows that (1) this technique pro-duces a significant increment of fatigue life of steel girder which is more than 10 times compared with that of pre-crack stage; (2) the fatigue lives, which extended from the reinforcement with different pre-crack sizes, differ up to 10 times. The post-tensioning method was applied to prestress the CFRP of steel girder plate successfully and an-chorage system can real-time control the prestress in CFRP plates and the prestress loss is slight.%首先,采用修正的Pairs公式分析粘贴预应力CFRP板加固的钢构件的疲劳裂纹扩展行为.然后通过粘贴CFRP板的预制裂纹钢梁4点弯曲进行疲劳试验研究,最后基于阻止裂纹扩展的角度提出一种初步估计加固所需预应力大小的简化计算和设计方法.结果表明,粘贴预应力CFRP板对钢梁疲劳寿命的影响很大,与预制裂纹阶段比寿命提高最高可达10倍以上.不同的预制裂纹,同样的加固措施效果差别可达10倍.采用后张法施加预应力效果很好,锚固装置可以实时控制有效预应力,且预应力损失很小.
The Compare Between Steel Box Girder And Steel Truss In City Overpass%钢箱梁及钢桁架城市人行天桥对比分析
范旭辉
2012-01-01
Steel box girder bridges are widely used in our city pedestrian bridge and it has the characteristic such as linear appearance and easy factory prefabricated construction. However, due to the need to control the vertical nat- ural vibration frequency, the box girder general beam steel is too high. As a result the steel truss bridge in the city pedestrian bridge is also a widely the popularity of the bridge type. The particle compares among the same span of two bridge type comprehensive comparison of the amount of structural steel, vertical natural frequency, constructa- bility, stairways climbed higher.%钢箱梁桥在我国城市人行天桥中应用广泛,其优点是线型美观,工厂预制装配式施工方便等。然而由于需要控制竖向自振频率,钢箱梁一般梁高过高,造成压抑感强,两侧梯道过长等缺点也不容忽视,因此钢桁架桥在城市人行桥中也是一种可以广泛普及的桥型,本文对相同跨径的两种桥型就结构用钢量、竖向自振频率、施工性、梯道爬高等方面进行了综合对比。
Li Jianzhong; Peng Tianbo; Xu yan
2008-01-01
An investigation of girder bridges on National Highway 213 and the Doujiangyan-Wenchuan expressway after the Wenchuan earthquake showed that typical types of damage included:span collapses due to unseating at expansion joints;shear key failure;and damage of the expansion joint due to the slide-induced large relative displacement between the bottom of the girder and the top of the laminated-rubber bearing.This slide,however,can actually act as a form of isolation for the substructure,and as a result,the piers and foundation of most of the bridges on state route 213 suffered minor damage.The exception was the Baihua Bridge,which suffered severe damage.Corresponding seismic design recommendations are presented based on this investigation.
Nguyen, Khac Duy; Lee, So Young; Kim, Jeong Tae [Pukyong National University, Busan (Korea, Republic of)
2011-12-15
Ensuring the designed prestress force is very important for the safety of prestressed concrete bridge. The loss of prestress force in tendon could significantly reduce load carrying capacity of the structure. In this study, an automated prestress-loss monitoring system for prestressed concrete girder using PZT-interface and wireless impedance sensor node is presented. The following approaches are carried out to achieve the objective. Firstly, wireless impedance sensor nodes are designed for automated impedance-based monitoring technique. The sensor node is mounted on the high-performance Imote2 sensor platform to fulfill high operating speed, low power requirement and large storage memory. Secondly, a smart PZT-interface designed for monitoring prestress force is described. A linear regression model is established to predict prestress-loss. Finally, a system of the PZT-interface interacted with the wireless sensor node is evaluated from a lab-scale tendon-anchorage connection of a prestressed concrete girder.
Structural Optimization of Steel Cantilever Used in Concrete Box Girder Bridge Widening
Qian Wang
2015-01-01
Full Text Available The structural optimization method of steel cantilever used in concrete box girder bridge widening is illustrated in this paper. The structural optimization method of steel cantilever incorporates the conceptual layout design of steel cantilever beam based on the topological theory and the determination of the optimal location of the transverse external prestressed tendons which connect the steel cantilever and the box girder. The optimal design theory and the analysis process are illustrated. The mechanical model for the prestressed steel cantilever is built and the analytical expression of the optimal position of the transverse external tendon is deduced. At last the effectiveness of this method is demonstrated by the design of steel cantilevers which are used to widen an existing bridge.
Full Scale Test of a SSP 34m box girder 1. Data report
Jensen, Find Mølholt; Branner, Kim; Nielsen, Per Hørlyk;
This report presents the setup and result of a full-scale test of a reinforced glass fibre/epoxy box girder used in 34m wind turbine blade. The tests were performed at the Blaest test facility in August 2006. The test is an important part of a research project established in cooperation between...... the box girder was loaded until failure. A comprehensive description of the test setup is given. This report deals only with tests and results. There are no conclusions on the data in this report, but references are given to publications, where the data are used and compared with FEM etc. Various kinds...... of measuring equipment have been used during these tests: acoustic emission, 330 strain gauges, 24 mechanical displacement devices and two optical deformation measuring systems. The mechanical displacement devices measured both global (absolute) and local (relative) deflection and the optical systems measured...
Numerical Simulation for Progressive Collapse of Continuous Girder Bridge Subjected to Ship Impact
田力; 黄飞
2014-01-01
The three-stage simulation method based on LS-DYNA was introduced in this study to simulate the pro-gressive collapse of a continuous girder bridge after a ship-bridge collision. The pile-soil dynamic interaction and the initial stress and deformation of the whole bridge before the collision were considered. By analyzing the damage, de-formation, stress distribution and collapse process of the whole bridge, the results show that the displacement response of the cap beam lags behind the pile cap. The response order of the whole bridge’s components depends on their dis-tances from the collision region. The plastic deformation of soil around piles has a positive effect on delaying the fur-ther increase in the displacement of piles. The impacted pier’s losing stability and its superstructure’s excessive defor-mation are the main reasons leading to the progressive collapse of the continuous girder bridge.
Continuous rigid PC frame box girder cantilever pouring construction reasonable maintenance method
Wulin
2015-08-01
Full Text Available In recent years, prestressed concrete continuous rigid frame box girder plate and web plate produced a large number of non-structural cracks disease caused the attention of large bridge workers, to solve the problem of continuous rigid-frame structure of the cantilever of the disease, this article briefly introduced the cantilever construction method and the performance requirements of modern concrete, through to the modern concrete composition change and keeping in good health on the impact of environment on its early performance analysis summary, points out the present problems of box girder early curing, finally combining with the characteristics of modern concrete performance and the characteristics of the cantilever construction method, puts forward "model attach +manual+automatic water spray mist stick " composite curing method in order to reduce the structural cracks, provides a new train of thought.
客货共线1-156m简支钢桁结构分析%Structural analysis of 156 m simply supported steel truss girder
郝云杉
2012-01-01
The simply supported steel truss girder is widely used in railway bridge, because of definite stress, lower structural height, light weight and short construction period. Huanglin Hancheng Houma railway 156 m simply supported steel truss girder is the most span length in China. The bridge uses the triangle web member system without vertical members, which main truss members are box sections, the web members are box sections and H-shape sections. In the plane of the upper chords, the crisscross top lateral bracings are arranged which use I-shape sections. MIDAS Civil 2010 is use to establish the three-dimensional finite element model, calculate internal forces of main truss elements, stress, fatigue stress range and natural vibration period.%简支钢桁梁桥因其受力明确、结构高度低、自重轻以及施工周期短等优点,在铁路桥梁中得到了越来越广泛的采用.黄韩侯铁路单线l-156m栓焊下承式简支钢桁梁是目前国内最大跨度的简支钢桁梁结构.该桥主桁采用无竖杆的三角形腹杆体系,主桁弦杆均采用箱形截面；腹杆采用箱形截面和H形截面；上、下均采用交叉式平纵联,采用工字型截面.采用MIDAS Civil 2010建立该桥三维有限元模型,计算其主桁杆件内力、应力、疲劳应力幅,及全桥自振周期.
Finite Element Analysis of the Effect of Crack Depth and Crack Opening On the Girder
Md. Kamrul Hassan
2011-01-01
Full Text Available In order to identify the effect of crack depth and opening on the girder, finite element method (FEM has been used in this paper. In FE analysis, six nodded two dimensional plane elements (PLANE-2 are considered. Each node has two degree of freedom such as UX and UY. For the plane elements, a plane stress width/thickness option is chosen. For analytical model of crack of the concrete bridge girder, crack opening was increased from 0.2 mm to 1mm at an interval 0.2 mm and crack depth also increased from 30 mm to 150 mm at an interval 30 mm. The models were discreatized by a triangular mesh and convergence test was executed to obtain satisfactory results from the Plane-2 element. From the numerical result, it is seen that the principal stress become a higher with increased the crack depth and also crack opening with respect to load increasing. But the crack depth at 90 mm and crack opening at 0.6 mm, it has more effect on the girder because the stress concentration is higher than other crack depth and opening.
The vibration research of the AC dipole-girder system for CSNS/RCS
Renhong, Liu; Huamin, Qu; Ling, Kang; Motuo, Wang; Guangyuan, Wang; Haijing, Wang
2013-01-01
China spallation neutron source(CSNS) is a high intensity proton accelerator based facility, and its accelerator complex includes two main parts: an H- linac and a rapid cycling synchrotron(RCS). The rcs accumulates the 80MeV proton beam, and accelerates it to 1.6GeV, with a repetition rate of 25 Hz. The AC dipole of the RCS is operated at a 25Hz sinusoidal alternating current which causes severe vibration. The vibration will influence the long-term safety and reliable operation of the magnet. The dipole magnet of RCS is active vibration equipment which is different with ground vibration accelerator. It is very important to design and research the dynamic characteristic of the dipole-girder system. This paper takes the dipole and girder as a specific model system, a method for researching the dynamic characteristic of the system is put forward by combining theoretical calculation with experimental testing. The ansys simulation method plays a very important role in the girder structure design stage. With the m...
Study the vibration and dynamic response of the dipole girder system for CSNS/RCS
Renhong, Liu; JunSong, Zhang; GuangYuan, Wang
2015-01-01
China Spallation Neutron Source is a high intensity proton accelerator based facility, and its accelerator complex includes two main parts an H- linac and a rapid cycling synchrotron. The RCS accumulates the 80MeV proton beam, and accelerates it to 1.6GeV, with a repetition rate of 25Hz. The dipole of the CSNS RCS is operated at a 25 Hz sinusoidal alternating current which causes severe vibrate. The vibration will influence the long term safety and reliable operation of the magnet. The dipole of the CSNS RCS is an active vibration equipment which is different from the ground vibration accelerator. It is very important to design and study the dynamic characteristics of the dipole girder system. This paper takes the dipole and girder as a specific model system, a method for studying the dynamic characteristics of the system is put forward by combining theoretical calculation with experimental testing. The modal parameters with and without vibration isolator of the dipole girder system are obtain through ANSYS s...
Computer Simulation of Dynamic Interactions Between Vehicle and Long Span Box Girder Bridges
Lei Gong; Moe S.Cheung
2008-01-01
Moving vehicle loads,associated with roadway traffic can induce significant dynamic effects on the structural behaviours of bridges,especially for long-span bridges.The main objective of current research is to study traffic induced dynamic responses of long-span box-girder bridges.The finite element method has been employed in this study to obtain a three-dimensional mathematical model for the bridge system.For vehicle-bridge dynamic interaction analysis,the vehicle is modeled as a more realistic three-axle,six-wheel system,and the corresponding dynamic interaction equations have been derived.The bridge-vehicle inter- action is affected by many factors.The current study has been focused on such factors as:vehicle speed, vehicle damping ratio,multiple traffic lanes,mass ratio of vehicle and bridge,and dynamic characteristics of bridge.Case studies have been conducted to investigate these factors by using several box girder bridge examples including Confederation Bridge,the longest box girder bridge in the world.
Field test on temperature field and thermal stress for prestressed concrete box-girder bridge
Baoguo CHEN; Rui DING; Junjie ZHENG; Shibiao ZHANG
2009-01-01
A field test was conducted to investigate the distribution of temperature field and the variation of thermal stress for a prestressed concrete (PC) box-girder bridge. The change of hydration heat temperature consists of four periods: temperature rising period, constant temperature period, rapid temperature fall period and stow temperature fall period. The peak value of hydration heat temperature increases with the increasing casting temperature of concrete; the relation between them is approximately linear. According to field tests, the thermal stress incurred by hydration heat may induce temperature cracks on the PC box-girder. Furthermore, the nonlinear distribution of temperature gradient and the fluctuation of thermal stress induced by exposure to sunlight were also obtained based on continuous in-situ monitoring. Such results show that the prevailing Chinese Code (2004) is insufficient since it does not take into account the temperature gradient of the bottom slab. Finally, some preventive measures against temperature cracks were proposed based on related studies. The conclusions can provide valuable reference for the design and construction of PC box-girder bridges.
Shear and shear friction of ultra-high performance concrete bridge girders
Crane, Charles Kennan
Ultra-High Performance Concrete (UHPC) is a new class of concrete characterized by no coarse aggregate, steel fiber reinforcement, low w/c, low permeability, compressive strength exceeding 29,000 psi (200 MPa), tensile strength ranging from 1,200 to 2,500 psi (8 to 17 MPa), and very high toughness. These properties make prestressed precast UHPC bridge girders a very attractive replacement material for steel bridge girders, particularly when site demands require a comparable beam depth to steel and a 100+ year life span is desired. In order to efficiently utilize UHPC in bridge construction, it is necessary to create new design recommendations for its use. The interface between precast UHPC girder and cast-in-place concrete decks must be characterized in order to safely use composite design methods with this new material. Due to the lack of reinforcing bars, all shear forces in UHPC girders have to be carried by the concrete and steel fibers. Current U.S. codes do not consider fiber reinforcement in calculating shear capacity. Fiber contribution must be accurately accounted for in shear equations in order to use UHPC. Casting of UHPC may cause fibers to orient in the direction of casting. If fibers are preferentially oriented, physical properties of the concrete may also become anisotropic, which must be considered in design. The current research provides new understanding of shear and shear friction phenomena in UHPC including: (1) Current AASHTO codes provide a non-conservative estimate of interface shear performance of smooth UHPC interfaces with and without interface steel. (2) Fluted interfaces can be created by impressing formliners into the surface of plastic UHPC. AASHTO and ACI codes for roughened interfaces are conservative for design of fluted UHPC interfaces.(3) A new equation for the calculation of shear capacity of UHPC girders is presented which takes into account the contribution of steel fiber reinforcement. (4) Fibers are shown to preferentially
Rensink, Arend; Gorrieri, Roberto
We investigate criteria to relate specifications and implementations belonging to conceptually different abstraction levels, and propose vertical bisimulation as a candidate relation for this purpose. Vertical bisimulation is indexed by a function mapping abstract actions onto concrete processes,
Zhou Danfeng
2017-01-01
Full Text Available The maglev vehicle-girder coupled vibration problem has been encountered in many maglev test or commercial lines, which significantly degrade the performance of the maglev train. In previous research on the principle of the coupled vibration problem, it has been discovered that the fundamental model of the maglev girder can be simplified as a series of mass-spring resonators of different but related resonance frequencies, and that the stability of the vehicle-girder coupled system can be investigated by separately examining the stability of each mass-spring resonator – electromagnet coupled system. Based on this conclusion, a maglev test platform, which includes a single electromagnetic suspension control system, is built for experimental study of the coupled vibration problem. The guideway of the test platform is supported by a number of springs so as to change its flexibility. The mass of the guideway can also be changed by adjusting extra weights attached to it. By changing the flexibility and mass of the guideway, the rules of the maglev vehicle-girder coupled vibration problem are to be examined through experiments, and related theory on the vehicle-girder self-excited vibration proposed in previous research is also testified.
Optimal Orthogonal Graph Drawing with Convex Bend Costs
Bläsius, Thomas; Wagner, Dorothea
2012-01-01
Traditionally, the quality of orthogonal planar drawings is quantified by either the total number of bends, or the maximum number of bends per edge. However, this neglects that in typical applications, edges have varying importance. Moreover, as bend minimization over all planar embeddings is NP-hard, most approaches focus on a fixed planar embedding. We consider the problem OptimalFlexDraw that is defined as follows. Given a planar graph G on n vertices with maximum degree 4 and for each edge e a cost function cost_e : N_0 --> R defining costs depending on the number of bends on e, compute an orthogonal drawing of G of minimum cost. Note that this optimizes over all planar embeddings of the input graphs, and the cost functions allow fine-grained control on the bends of edges. In this generality OptimalFlexDraw is NP-hard. We show that it can be solved efficiently if 1) the cost function of each edge is convex and 2) the first bend on each edge does not cause any cost (which is a condition similar to the posi...
田仲初; 陈耀章; 赵利平; 程永舟
2012-01-01
In order to study local force characters of the large span continuous steel tank girder incremental launching, taking a 6× 90 m vertical curve of variable curvature continuous steel girder as the research object, the whole simulation model was set up by the software MIDAS 2006 with ＂beam remain still and only lower supports reverse move＂ method. Then based on the analysis re- suits of the whole girder, a ＂beam-shell-solid-contact＂ hybrid finite element model was set up with ANSYS APDL and by means of Excel and CAD assistance under the unfavorable condition. The theoretical and measured values show that the steel girder local force meets the requirements at the sliding part, but the angular displacement is too large. According to the actual engineering situation, two effective improvements are suggested to solve a series of problems which are caused by the exaggerated angular displacement, the one is that the steps nose beam is adopted in the first measure, the second measure adopt a combination of steps nose beam, weights and in- creasing the stiffness of part of the steel beam. 6 tabs, 9 figs, 13 refs.%为了研究大跨度连续钢梁顶推的局部受力特性,以6×90m变曲率竖曲线连续钢梁顶推为研究对象,根据梁不动、下部支撑移动的＂倒退＂方法,采用商用程序MIDAS 2006建立顶推整体有限元模型,并对其进行仿真分析。在此基础上,根据顶推整体仿真计算结果,选取滑道处钢梁最不利工况,借助EXCEL和CAD等辅助工具,运用ANSYS的APDL语言快速建立＂梁-壳-实-接触＂混合有限元模型。理论和实测值均表明：最不利工况下滑道处钢梁局部受力满足要求,但转角位移过大。结合工程实际情况,提出了2种有效改善措施：第一种采用台阶导梁;第二种采用台阶导梁、压重和增大部分钢梁截面刚度的组合方式。
Bending instability in galactic discs. Advocacy of the linear theory
Rodionov, S A
2013-01-01
We demonstrate that in N-body simulations of isolated disc galaxies there is numerical vertical heating which slowly increases the vertical velocity dispersion and the disc thickness. Even for models with over a million particles in a disc, this heating can be significant. Such an effect is just the same as in numerical experiments by Sellwood (2013). We also show that in a stellar disc, outside a boxy/peanut bulge, if it presents, the saturation level of the bending instability is rather close to the value predicted by the linear theory. We pay attention to the fact that the bending instability develops and decays very fast, so it couldn't play any role in secular vertical heating. However the bending instability defines the minimal value of the ratio between the vertical and radial velocity dispersions $\\sigma_z / \\sigma_R \\approx 0.3$ (so indirectly the minimal thickness) which could have stellar discs in real galaxies. We demonstrate that observations confirm last statement.
Sheet Bending using Soft Tools
Sinke, J.
2011-05-01
Sheet bending is usually performed by air bending and V-die bending processes. Both processes apply rigid tools. These solid tools facilitate the generation of software for the numerical control of those processes. When the lower rigid die is replaced with a soft or rubber tool, the numerical control becomes much more difficult, since the soft tool deforms too. Compared to other bending processes the rubber backed bending process has some distinct advantages, like large radius-to-thickness ratios, applicability to materials with topcoats, well defined radii, and the feasibility of forming details (ridges, beads). These advantages may give the process exclusive benefits over conventional bending processes, not only for industries related to mechanical engineering and sheet metal forming, but also for other disciplines like Architecture and Industrial Design The largest disadvantage is that also the soft (rubber) tool deforms. Although the tool deformation is elastic and recovers after each process cycle, the applied force during bending is related to the deformation of the metal sheet and the deformation of the rubber. The deformation of the rubber interacts with the process but also with sheet parameters. This makes the numerical control of the process much more complicated. This paper presents a model for the bending of sheet materials using a rubber lower die. This model can be implemented in software in order to control the bending process numerically. The model itself is based on numerical and experimental research. In this research a number of variables related to the tooling and the material have been evaluated. The numerical part of the research was used to investigate the influence of the features of the soft lower tool, like the hardness and dimensions, and the influence of the sheet thickness, which also interacts with the soft tool deformation. The experimental research was focused on the relation between the machine control parameters and the most
Yan Shiguang; Li Hongtao; Wang Chao
2012-01-01
This article presents in detail the assembling and welding process technique of the steel box girder tuyere blocks of Taizhou Bridge. The application of this process technique effectively solves the problem of welding stress release in tuyere block assembling and welding without increasing the number of turns of the blocks and overhead welding, thus avoiding possible structural deformation due to excessive accumulation of internal welding stress, greatly reducing the repeated deformation and correction work during assembling and welding, and ensuring the weld seam quality and overall dimensions of tuvere blocks of Taizhou Bridze.
Methods for determination of ultimate load of eccentrically patch loaded steel I-girders
Šćepanović, B.
2014-12-01
Full Text Available Experimental tests show that most eccentrically patch loaded steel I-girders have a collapse mode quite different from that of centrically loaded girders. Concerning engineering practice, the most important difference between collapse modes is in ultimate load. The reduction in ultimate load with an increase in load eccentricity is obvious in some eccentrically loaded girders. Under certain circumstances, for a certain combination of influential parameters, eccentrically loaded girders behave as if loaded in the web plane, with no or no significant reduction in ultimate load due to load eccentricity. Dealing with such a big number of mutually dependant parameters that influence collapse mode and level of ultimate load reduction due to load eccentricity, still without theoretical formulation of collapse mechanism, two approaches for ultimate load determination are analysed: empirical mathematical expressions and artificial neural networks forecast models. Results of two procedures are compared. Recommendations for application in engineering practice are given.Las pruebas experimentales muestran que la mayoría de vigas en I de acero cargadas excéntricamente tienen un modo de colapso muy diferente del de las vigas cargadas centradas. En cuanto a la práctica de ingeniería, la diferencia más importante entre los modos de colapso es la carga final. La reducción de la carga última con un aumento de la excentricidad de carga es evidente en algunas vigas cargadas excéntricamente, mientras que bajo ciertas circunstancias, para una determinada combinación de parámetros influyentes, las vigas cargadas excéntricamente se comportan como si se carga en el plano del alma, con ninguna reducción significativa en la carga última debido a la carga excéntrica. Se analizan dos métodos para la determinación de la carga máxima: expresiones matemáticas empíricas y redes neuronales artificiales. Los resultados de ambos procedimientos se comparan. Se
Double Girder Bridge Crane with Double Cycling: Scheduling Strategy and Performance Evaluation
Dandan Wang
2014-01-01
Full Text Available This paper introduces a novel quay crane design, double girder bridge crane (DGBC. DGBC is capable of handling containers of two adjacent bays simultaneously, avoiding crane collisions, saving travelling and reposition cost, and eventually improving terminal efficiency. This problem is formulated as a resource-constrained project scheduling with objective to minimize the maximum completion time. A two-stage heuristic algorithm is proposed in which an operating sequences on each bay is obtained by double cycling, and the integrated timetable for both bays is constructed by solving resource conflicts using the proposed minimum cost strategy. We examine effectiveness and performance of applying DGBC with double cycling. A case study is presented to illustrate how DGBC works with the two-stage method. Three extreme cases with respective conflict types are investigated to develop the performance bounds of DGBC with double cycling. The results show that DGBC can significantly improve terminal productivity, and outperforms single girder crane in both makespan and the lift operation percentage. The highest DGBC efficiency does not require maximum double cycles in two bay schedules; rather the integrated timetable for two bays is the main contribution to the DGBC performance as it yields better cooperation between two spreaders and the driver.
Xiaoguang Deng
2015-01-01
Full Text Available Based on the nonlinear stability analysis method, the 3D nonlinear finite element model of a composite girder cable-stayed bridge with three pylons is established to research the effect of factors including geometric nonlinearity, material nonlinearity, static wind load, and unbalanced construction load on the structural stability during construction. Besides, the structural nonlinear stability in different construction schemes and the determination of temporary pier position are also studied. The nonlinear stability safety factors are calculated to demonstrate the rationality and safety of construction schemes. The results show that the nonlinear stability safety factors of this bridge during construction meet the design requirement and the minimum value occurs in the maximum double cantilever stage. Besides, the nonlinear stability of the structure in the side of edge-pylon meets the design requirement in the two construction schemes. Furthermore, the temporary pier can improve the structure stability, effectively, and the actual position is reasonable. In addition, the local buckling of steel girder occurs earlier than overall instability under load in some cable tension stages. Finally, static wind load and the unbalanced construction load should be considered in the stability analysis for the adverse impact.
Fatigue stress monitoring and analyses for steel box girder of Runyang Suspension Bridge
Ying WANG; Zhaoxia LI; Baijian WU
2008-01-01
The monitoring of fatigue stress of steel bridge is a key issue of bridge health monitoring and safety assessment. This paper aims to find out the strain history features of the girder components of Runyang Suspension Bridge (RYSB) under vehicle and environmental loading during its first year of service based on the strain-history data recorded by structural health monitoring system installed in the bridge. The fatigue stress spectrums of steel box girders under normal traffic load, heavy trucks and typhoon loads were studied as well as the correlation between varying strain and temperature based on real-time monitoring of temperature histories. The results show that, monitoring on local strain in health monitoring systems of RYSB can effectively provide the information on fatigue stresses. The range of the equivalent fatigue stress on the monitoring location of the bridge is currently low, mainly due to varying traffic loading and temper-ature. There exists significant correlation between varying temperature and mean value of fatigue stress. Effect of the passing of heavy trucks on bridge fatigue is quite signifi-cant since the value of the cumulative fatigue damage generated by heavy trucks is 10 to 100 times larger than that by normal traffic. Therefore, the effect on fatigue cumulative damage due to heavy trucks or overloaded vehicles needs to be monitored and paid much attention to.
Free vibrations of multi-girder and multi-cell box bridges with transverse deformations effects
Hamed, E.; Frostig, Y.
2005-01-01
A general mathematical approach is developed for the free vibration behaviour analysis of multi-girder and multi-cell box bridges with a single or multi span, including the effects of the transverse deformations of the bridge cross-section. The governing equations of motion and the corresponding boundary and continuity conditions are derived via the variational principle of virtual work following Hamilton's principle. The model is general and valid for any boundary and continuity conditions, and is applicable for multi-girder bridges with longitudinal and cross beams and for multi-cell box bridges. The warping and the distortion of the bridge cross-section effects are included in the proposed model. Closed-form solutions of the governing equations are derived and the Newton-Raphson method is used to determine the eigenfrequencies. Numerical examples are presented to validate the proposed model, and are also used to examine the accuracy of other approximate models used in the analysis of bridges. The results of the proposed model are validated through comparison with three-dimensional finite element models. The results reveal that the transverse deformations decrease the magnitudes of the eigenfrequencies of the torsional mode shapes, as well as the high flexural modes.
Coupled Vibration of Long-Span Railway Curved Girder Bridges and Vehicles
Shan Deshan; Li Qiao
2005-01-01
The structure of a long curved girder bridge is represented with a three-dimensional curved finite element model. Each 4-axle vehicle is modeled by a dynamic system of 35 degrees of freedom. The random irregularities of the track are generated from a power spectral density function under the given track condition. The dynamic interaction between the bridge and train is realized through the contact forces between the wheels and track. Then based on these models, the coupled equations of motion are solved by applying the time-integration and iteration techniques to the coupled system. The proposed formulation and the associated computer program are then applied to a real curved girder bridge. The dynamic responses of the bridge-vehicle system and the derailments and offload factors related to the riding and running safeties of vehicles are computed. The results show that the formulation presented in this paper can well predict dynamic behaviors of both bridge and train with reasonable computation efforts.
A Cyber-Physical System for Girder Hoisting Monitoring Based on Smartphones
Han, Ruicong; Zhao, Xuefeng; Yu, Yan; Guan, Quanhua; Hu, Weitong; Li, Mingchu
2016-01-01
Offshore design and construction is much more difficult than land-based design and construction, particularly due to hoisting operations. Real-time monitoring of the orientation and movement of a hoisted structure is thus required for operators’ safety. In recent years, rapid development of the smart-phone commercial market has offered the possibility that everyone can carry a mini personal computer that is integrated with sensors, an operating system and communication system that can act as an effective aid for cyber-physical systems (CPS) research. In this paper, a CPS for hoisting monitoring using smartphones was proposed, including a phone collector, a controller and a server. This system uses smartphones equipped with internal sensors to obtain girder movement information, which will be uploaded to a server, then returned to controller users. An alarming system will be provided on the controller phone once the returned data exceeds a threshold. The proposed monitoring system is used to monitor the movement and orientation of a girder during hoisting on a cross-sea bridge in real time. The results show the convenience and feasibility of the proposed system. PMID:27399710
Zhengjie Zhou
2010-01-01
Full Text Available Precast, prestressed concrete box girders are commonly used as superstructure components for short and medium span bridges. Their configuration and typical side-by-side placement make large portions of these elements inaccessible for visual inspection or the application of nondestructive testing techniques. This paper demonstrates that vibration-based damage detection (VBDD is an effective alternative for monitoring their structural health. A box girder removed from a dismantled bridge was used to evaluate the ability of five different VBDD algorithms to detect and localize low levels of spalling damage, with a focus on using a small number of sensors and only the fundamental mode of vibration. All methods were capable of detecting and localizing damage to a region within approximately 1.6 times the longitudinal spacing between as few as six uniformly distributed accelerometers. Strain gauges configured to measure curvature were also effective, but tended to be susceptible to large errors in near support damage cases. Finite element analyses demonstrated that increasing the number of sensor locations leads to a proportional increase in localization accuracy, while the use of additional modes provides little advantage and can sometimes lead to a deterioration in the performance of the VBDD techniques.
A Cyber-Physical System for Girder Hoisting Monitoring Based on Smartphones.
Han, Ruicong; Zhao, Xuefeng; Yu, Yan; Guan, Quanhua; Hu, Weitong; Li, Mingchu
2016-07-07
Offshore design and construction is much more difficult than land-based design and construction, particularly due to hoisting operations. Real-time monitoring of the orientation and movement of a hoisted structure is thus required for operators' safety. In recent years, rapid development of the smart-phone commercial market has offered the possibility that everyone can carry a mini personal computer that is integrated with sensors, an operating system and communication system that can act as an effective aid for cyber-physical systems (CPS) research. In this paper, a CPS for hoisting monitoring using smartphones was proposed, including a phone collector, a controller and a server. This system uses smartphones equipped with internal sensors to obtain girder movement information, which will be uploaded to a server, then returned to controller users. An alarming system will be provided on the controller phone once the returned data exceeds a threshold. The proposed monitoring system is used to monitor the movement and orientation of a girder during hoisting on a cross-sea bridge in real time. The results show the convenience and feasibility of the proposed system.
TRAPEZOIDAL PLATE BENDING ELEMENT WITH DOUBLE SET PARAMETERS
Shao-chun Chen; Dong-yang Shi; I chiro Hagiwara
2003-01-01
Using double set parameter method, a 12-parameter trapezoidal plate bending element is presented. The first set of degrees of freedom, which make the element convergent, are the values at the four vertices and the middle points of the four sides together with the mean values of the outer normal derivatives along four sides. The second set of degree of freedom, which make the number of unknowns in the resulting discrete system small and computation convenient are values and the first derivatives at the four vertices of the element. The convergence of the element is proved.
A Numerical Study of the Spring-Back Phenomenon in Bending with a Rebar Bending Machine
Chang Hwan Choi; Lawrence Kulinsky; Joon Soo Jun; Jin Ho Kim
2014-01-01
Recently, the rebar bending methodology started to change from field processing to utilizing rebar bending machines at plant sites prior to transport to the construction locations. Computerized control of rebar plant bending machines provides more accurate and faster bending of rebars than the low quality inefficient field processing alternative. The bending process involves plastic deformation of rebars, where bending stress beyond the yield point of the material is applied. When the bending...
Ultra low vertical emittance at SLS through systematic and random optimization
Aiba, M.; Milas, N.; Streun, A.
2012-01-01
A new vertical emittance record of 0.9+-0.4 pm rad was established in the storage ring of the Swiss Light Source (SLS) at 2.4 GeV by the application of a sequence of methods: Magnet girders were remotely vertically realigned in order to suppress the dipolar fields that produce the spurious dispersion in the vertical plane. A systematic optimization was then performed by measuring and correcting the betatron coupling and the vertical dispersion by means of 36 skew quadrupole correctors. The correction is performed until a limit is reached from the orbit response matrix (ORM) measurement errors and residual model deficiencies. At this point, the method of random optimization (RO), a multi-variable optimization procedure, was invoked. In the present experiment, the vertical beam size is the target function while the skew quadrupole currents act as the correction variables. The methodology of RO and the systematic correction scheme are described.
Wang Changfeng
2014-10-01
Full Text Available During an earthquake, the nonlinearity of the bridge structure mainly occurs at the supports, bridge piers and restrainers. When entering nonlinear stage, members of the bridge structure affect the elasto-plastic seismic response of the whole structure to a certain extent; for multi-span continuous bridges, longitudinal restrainers can be installed on the movable piers to optimise the distribution of seismic force and enable the movable piers to bear a certain amount of seismic effect. In order to evaluate the effect of nonlinearity of restrainer and supports on the elasto-plastic seismic response of continuous girder bridge, analytical models of continuous girder bridge structure considering the nonlinearity of movable supports, restrainers and bridge piers were built and the nonlinear time history analysis was conducted to evaluate the effect of nonlinearity of restraining devices and supports on the elasto-plastic seismic response of continuous girder bridge. Relevant structural measures and recommendation were made to reduce the seismic response of the fixed piers of the continuous girder bridge.
Bending fracture in carbon nanotubes.
Kuo, Wen-Shyong; Lu, Hsin-Fang
2008-12-10
A novel approach was adopted to incur bending fracture in carbon nanotubes (CNTs). Expanded graphite (EG) was made by intercalating and exfoliating natural graphite flakes. The EG was deposited with nickel particles, from which CNTs were grown by chemical vapor deposition. The CNTs were tip-grown, and their roots were fixed on the EG flakes. The EG flakes were compressed, and many CNTs on the surface were fragmented due to the compression-induced bending. Two major modes of the bending fracture were observed: cone-shaped and shear-cut. High-resolution scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to examine the crack growth within the graphene layers. The bending fracture is characterized by two-region crack growth. An opening crack first appears around the outer-tube due to the bending-induced tensile stress. The crack then branches to grow along an inclined direction toward the inner-tube due to the presence of the shear stress in between graphene layers. An inner-tube pullout with inclined side surface is formed. The onset and development of the crack in these two regions are discussed.
Tube bending on the roll machine
Nepershin, Rostislav I.
2013-10-01
Computer simulation of the elastic-plastic tube bending by pushing on three-roll machine with work hardening effect consideration is presented. Non-steady tube bending process for specified curvature is simulated with axis of bending roll displacement, followed by transfer to the steady-state bending process. Estimation of curvature, constrained by tube section elliptical distortion modeled by plastic hinge mechanism is given. Elastic-plastic bending moment versus curvature and critical curvature estimation reasonably correlated with experiments.
无
2000-01-01
A new kind of bend sensor is introduced.It can be used to detect the bend angle of an object or inclination between two objects.It has characteristics of small size, lightweight, high reliability, fine flexibility and plasticity.When this bend sensor is used with a proper converting circuit, it can implement dynamic measuring the bend angle of an object conveniently.The application of the bend sensor in dataglove is also described.
Design of an impedance matching acoustic bend
Yang, Yuzhen; Jia, Han; Lu, Wenjia; Sun, Zhaoyong; Yang, Jun
2017-01-01
We propose the design of an impedance matching acoustic bend in this article. The bending structure is composed of sub-wavelength unit cells with perforated plates and side pipes, whose mass density and bulk modulus can be tuned simultaneously. So the refraction index and the impedance of the acoustic bend can be modulated simultaneously to guarantee both the bending effect and the high transmission. The simulation results of sound pressure field distribution show that the bending effect of t...
Bending characteristics of resin concretes
Ribeiro Maria Cristina Santos
2003-01-01
Full Text Available In this research work the influence of composition and curing conditions in bending strength of polyester and epoxy concrete is analyzed. Various mixtures of resin and aggregates were considered in view of an optimal combination. The Taguchi methodology was applied in order to reduce the number of tests, and in order to evaluate the influence of various parameters in concrete properties. This methodology is very useful for the planning of experiments. Test results, analyzed by this methodology, shown that the most significant factors affecting bending strength properties of resin concretes are the type of resin, resin content and charge content. An optimal formulation leading to a maximum bending strength was achieved in terms of material parameters.
Albert, Stephen L.; Spencer, Jeffrey B.
1994-01-01
'THE VERTICAL' computer keyboard is designed to address critical factors which contribute to Repetitive Motion Injuries (RMI) (including Carpal Tunnel Syndrome) in association with computer keyboard usage. This keyboard splits the standard QWERTY design into two halves and positions each half 90 degrees from the desk. In order to access a computer correctly. 'THE VERTICAL' requires users to position their bodies in optimal alignment with the keyboard. The orthopaedically neutral forearm position (with hands palms-in and thumbs-up) reduces nerve compression in the forearm. The vertically arranged keypad halves ameliorate onset occurrence of keyboard-associated RMI. By utilizing visually-reference mirrored mylar surfaces adjustable to the user's eye, the user is able to readily reference any key indicia (reversed) just as they would on a conventional keyboard. Transverse adjustability substantially reduces cumulative musculoskeletal discomfort in the shoulders. 'THE VERTICAL' eliminates the need for an exterior mouse by offering a convenient finger-accessible curser control while the hands remain in the vertically neutral position. The potential commercial application for 'THE VERTICAL' is enormous since the product can effect every person who uses a computer anywhere in the world. Employers and their insurance carriers are spending hundreds of millions of dollars per year as a result of RMI. This keyboard will reduce the risk.
A model of the response of thermoplastic composites to bend-forming operations
Talbott, M.F.
1991-01-01
The model discussed in this dissertation describes the response of a thermoplastic composite laminate made from unidirection prepreg tape to operations which bend it into an arbitrarily complex singly-curved shape. It predicts, for any such bending, the extent of relative ply sliding and the stresses and strains which arise. The model contains several options for the process definition: for different locations along the laminate, the user may specify the curvatures, the perpendicular forces imposed, or the vertical displacements.
石广田; 杨新文; 张小安; 杨建近
2015-01-01
A high speed train-track coupling dynamics model was established using Simpack software, and the wheel/rail vertical contact force excited by track irregularity spectrum was calculated. The wheel/rail vertical force was taken as a boundary condition and applied to the finite element model (FEM) of an elevated box girder structure to calculate its surface vibration response. Then, the vibration response was taken as the acoustic boundary conditions and was applied to the bound-ary element model (BEM) of the elevated box-girder structure to analyze its sound radiation. The results show that, using the finite element method and the boundary element method, the vibration noise of the concrete simply-supported box-beam structure can be effectively calculated with shell elements. The vibration noise is mainly concentrated in the low frequency range of 0-200 Hz, and the peaks mainly appear at the central frequencies of 16 Hz, 25 Hz, 80 Hz-100 Hz. The sound pres-sure level decreases with the increase of the distance from the ground in the lateral sound field and this tendency is more ob-vious for lower frequency sound field. The sound pressure level generally increases with the increase of the distance from the ground in the vertical acoustic field, and the sound pressure level in far field area does not change obviously for the fre-quencies below 31.5 Hz. In the range of 80 Hz-100 Hz, the sound pressure levels of the field points near the girder, especial-ly above the girder, are higher than those in the other regions.%利用Simpack软件建立高速列车-轨道耦合动力学模型，计算在轨道不平顺谱激励下的轮轨垂向力，以此作为载荷边界条件施加到高架箱梁结构的有限元模型。计算了高架箱梁表面的振动响应，并利用箱梁结构振动响应作为声学边界条件。进而又采用间接边界元法对其进行声辐射分析。研究结果表明，利用板壳单元，采用有限元—边界元方法能够有效
Flooding characteristics of gas-liquid two-phase flow in a horizontal U bend pipe
Sakaguchi, T.; Hosokawa, S.; Fujii, Y. [Kobe Univ. (Japan)] [and others
1995-09-01
For next-generation nuclear reactors, hybrid safety systems which consist of active and passive safety systems have been planned. Steam generators with horizontal U bend pipelines will be used as one of the passive safety systems. It is required to clarify flow characteristics, especially the onset of flooding, in the horizontal U bend pipelines in order to examine their safety. Flooding in vertical pipes has been studied extensively. However, there is little study on flooding in the horizontal U bend pipelines. It is supposed that the onset of flooding in the horizontal U bend pipelines is different from that in vertical pipes. On the other hand, liquid is generated due to condensation of steam in pipes of the horizontal steam generators at the loss of coolant accident because the steam generators will be used as a condenser of a cooling system of steam from the reactor. It is necessary to simulate this situation by the supply of water at the middle of horizontal pipe. In the present paper, experiments were carried out using a horizontal U bend pipeline with a liquid supply section in the midway of pipeline. The onset of flooding in the horizontal U bend pipeline was measured. Effects of the length of horizontal pipe and the radius of U bend on the onset of flooding were discussed.
Analysis of the hull girder vibration by dynamic stiffness matrix method
ZHOU Ping; ZHAO De-you
2006-01-01
Dynamic stiffness matrix method is applied to compute vibration of hull girder in this paper.This method can not only simplify the computational model, but also get much higher frequencies and responses accurately. The analytical expressions of dynamic stiffness matrix of a Timoshenko beam for transverse vibration are presented in this paper. All effects of rotatory inertia and shear deformation are taken into account in the formulation. The resulting dynamic stiffness matrix combined with the Wittrick-Williams algorithm is used to compute natural frequencies and mode shapes of the 299,500 DWT VLCC, and then the vibrational responses are solved by the mode superposition method. The computational results are compared with those obtained from other approximate methods and experiment,and it indicates that the method is accurate and efficient.
Prediction of Fatigue Life of a Continuous Bridge Girder Based on Vehicle Induced Stress History
V.G. Rao
2003-01-01
Full Text Available The fatigue damage assessment of bridge components by conducting a full scale fatigue testing is often prohibitive. A need, therefore, exists to estimate the fatigue damage in bridge components by a simulation of bridge-vehicle interaction dynamics due to the action of the actual traffic. In the present paper, a systematic method has been outlined to find the fatigue damage in the continuous bridge girder based on stress range frequency histogram and fatigue strength parameters of the bridge materials. Vehicle induced time history of maximum flexural stresses has been obtained by Monte Carlo simulation process and utilized to develop the stress range frequency histogram taking into consideration of the annual traffic volume. The linear damage accumulation theory is then applied to calculate cumulative damage index and fatigue life of the bridge. Effect of the bridge span, pavement condition, increase of vehicle operating speed, weight and suspension characteristics on fatigue life of the bridge have been examined.
Dynamic finite element model updating of prestressed concrete continuous box-girder bridge
Lin Xiankun; Zhang Lingmi; Guo Qintao; Zhang Yufeng
2009-01-01
The dynamic finite element model (FEM) of a prestressed concrete continuous box-girder bridge, called the Tongyang Canal Bridge, is built and updated based on the results of ambient vibration testing (AVT) using a real-coded accelerating genetic algorithm (RAGA). The objective functions are defined based on natural frequency and modal assurance criterion (MAC) metrics to evaluate the updated FEM. Two objective functions are defined to fully account for the relative errors and standard deviations of the natural frequencies and MAC between the AVT results and the updated FEM predictions. The dynamically updated FEM of the bridge can better represent its structural dynamics and serve as a baseline in long-term health monitoring, condition assessment and damage identification over the service life of the bridge.
Time-Variant Reliability Analysis of FPSO Hull Girder Considering Corrosion Based on Statistics
ZHANG Dao-kun; TANG Wen-yong; ZHANG Sheng-kun
2007-01-01
FPSO is a kind of important exploitation platform used in ocean oil and gas industry, which has the unique character of mooring at outsea for a long time. Since it can not be inspected and maintained thoroughly at dock like other kinds of ships, the reliability of FPSO hull girder during the whole service should be focused. Based on latest corrosion database and rational corrosion model, the ultimate strength of one FPSO is calculated under the conditions of slight, moderate and severe corrosion. The results not only provide the reliability under different corrosion conditions, but also do well for further inspection and maintenance research. The results provide necessary foundation for deciding inspection intervals and maintenance measures, which has practical sense to improve the general safety level of ocean engineering.
A compilation of research on self-consolidating concrete for prestressed bridge girders
Torres, Eduardo S.
This thesis is composed of three research papers, for each paper a separate chapter is used, which investigates various aspects for the production of SCC utilizing materials available in the state of Wisconsin. Chapter one provides a summary of the current state-of-the-art and practice of technical documentation and specifications related to material properties and test methods for prestressed SCC bridge girders. Chapter two provides an experimental program designed to investigate the effect of material constituents on performance of SCC mixtures. From this experimental program specific mixture parameters were recommended for the application of SCC in Wisconsin DOT projects. Finally, chapter three consisted in monitoring samples of five SCC mixtures batched at three different precast plants from Wisconsin. Creep and shrinkage readings were taken for a period of 112 days to investigate the effect of specific mixture parameters of selected mixtures with performance desired by the Wisconsin DOT and precast plants. (Abstract shortened by ProQuest.).
Bending behavior of lapped plastic ehv cables
Morgan, G H; Muller, A C
1980-01-01
One of the factors delaying the development of lapped polymeric cables has been their reputed poor bending characteristics. Complementary programs were begun at BNL several years ago to mathematically model the bending of synthetic tape cables and to develop novel plastic tapes designed to have moduli more favorable to bending. A series of bend tests was recently completed to evaluate the bending performance of several tapes developed for use in experimental superconducting cables. The program is discussed and the results of the bend tests are summarized.
Load Test and Model Calibration of a Horizontally Curved Steel Box-Girder Bridge
Freydoon Rezaie
2015-12-01
Full Text Available In this paper, full scale load test of a horizontally curved steel box-girder bridge is carried out in order to detect structural defects, which reportedly result in unwanted vibrations in nearby buildings. The bridge is tested under the passage of six heavy vehicles at different speeds, so as to determine its static and dynamic responses. A total number of one hundred and two (102 sensors are used to measure the displacements, strains, and accelerations of different points of the bridge. It is observed that the bridge vibrates at a fundamental frequency of 2.6 Hz intensively and the first mode of vibration is torsional instead of flexural. The dominant frequency of vibration of the nearby buildings is computed to be approximately 2.5Hz using rational formulas. Thus, nearness of the fundamental frequency of the bridge to those of the adjacent buildings may be causing resonance phenomenon. However, in static load tests, low ranges of strain and displacement illustrated adequate structural capacity and appropriate safety under static loads. Numerical models are created using ANSYS and SAP2000 software products, so as to design the loading test and calibrate the finite element models. The connections of the transversal elements to the girders, transversal element spacing, and changes of the stiffness values of the slabs were found to be the most influential issues in the finite elements calibration process. Finally, considering the total damage of all members, the final health score of the bridge was evaluated as 89% indicating that the bridge is in a very good situation.
Hormonal regulation of gravitropic bending
Hu, X.; Cui, D.; Xu, X.; Hu, L.; Cai, W.
Gravitropic bending is an important subject in the research of plant Recent data support the basics of the Cholodny-Went hypothesis indicating that differential growth in gravitropism is due to redistribution of auxin to the lower sides of gravistimulated roots but little is known regarding the molecular details of such effects So we carried a series of work surround the signals induced by auxin end center We found the endogenous signaling molecules nitric oxide NO and cGMP mediate responses to gravistimulation in primary roots of soybean Glycine max Horizontal orientation of soybean roots caused the accumulation of both NO and cGMP in the primary root tip Fluorescence confocal microcopy revealed that the accumulation of NO was asymmetric with NO concentrating in the lower side of the root Auxin induced NO accumulation in root protoplasts and asymmetric NO accumulation in root tips Gravistimulation NO and auxin also induced the accumulation of cGMP a response inhibited by removal of NO or by inhibitors of guanylyl cyclase compounds that also reduced gravitropic bending Asymmetric NO accumulation and gravitropic bending were both inhibited by an auxin transport inhibitor and the inhibition of bending was overcome by treatment with NO or 8-bromo-cGMP a cell-permeable analog of cGMP These data indicate that auxin-induced NO and cGMP mediate gravitropic curvature in soybean roots From Hu et al Plant Physiol 2005 137 663-670 The asymmetric distribution of auxin plays a fundamental role in plant gravitropic bending
陈建兵; 陈荣; 李强
2014-01-01
空间圆管桁架混凝土组合结构是一种新型组合结构，为了解其受力特点、破坏机理、变形能力、管桁架杆件的内力分布规律及界面相对滑移等，设计制作了2根弦杆未填充混凝土的不同混凝土翼板厚度的空间圆管桁架混凝土组合梁模型试件，采用三分点对称加载，对其进行受力性能试验研究。研究表明，在对称荷载作用下，组合梁的破坏形式为弯曲破坏，同时伴随有受拉腹杆节点焊缝的强度破坏；空间圆管桁架组合梁具有良好的承载能力和变形能力，相同荷载下，混凝土板厚的组合梁的承载能力高于板薄的组合梁；组合梁破坏时，其跨中挠度约为跨径的1/200；不考虑界面相对滑移的情况下，截面应变满足平截面假定；加载前期，支点截面界面相对滑移量大于 L/8截面，而加载后期，L/8截面界面相对滑移量大于支点截面；腹杆为非轴心受拉或受压杆件，且跨中位置腹杆的轴力较小，梁端位置腹杆的轴力较大。%The spatial steel truss of circular steel tubes and concrete composite structure is a new type of composite structure .In order to examine its load bearing behavior ,failure mechanism , deformability ,internal force distribution law of tubular truss members and interface relative slip -page ,a spatial steel truss of circular tubes and concrete composite girder model was designed and fabricated .The model was characterized by its two chords that are not filled with concrete as well as the concrete flange plates with variable thickness .Loads were symmetrically applied at the 1/3 and 2/3 locations of the calculated span length of the girder proposed .The mechanical behavior of the model was experimentally studied .The results of the study indicate that under the action of symmetric loads ,the composite girder succumbs to bending failure ,concurrently with strength damage at the welding joints of the tensile web
Electrical Reliability of a Film-Type Connection during Bending
Ryosuke Mitsui
2015-10-01
Full Text Available With the escalating demands for downsizing and functionalizing mobile electronics, flexible electronics have become an important aspect of future technologies. To address limitations concerning junction deformation, we developed a new connection method using a film-type connector that is less than 0.1 mm thick. The film-type connector is composed of an organic film substrate, a UV-curable adhesive that deforms elastically under pressure, and electrodes that are arranged on the adhesive. The film-type connection relies on a plate-to-plate contact, which ensures a sufficient contact area. The electrical reliability of the film-type connection was investigated based on changes in the resistance during bending at curvature radii of 70, 50, 25, 10, 5, and 2.5 mm. The connection was bent 1000 times to investigate the reproducibility of the connector’s bending properties. The tests showed that no disconnections occurred due to bending in the vertical direction of the electrode, but disconnections were observed due to bending in the parallel direction at curvature radii of 10, 5, and 2.5 mm. In addition, the maximum average change in resistance was less than 70 milliohms unless a disconnection was generated. These results support the application of the new film-type connection in future flexible devices.
Yoshida, K.; Hishiki, Y.; Furuichi, K. [Kajima Corp., Tokyo (Japan)
1999-09-30
A hybrid or mixed structure (composite structures) are a matter of increasing concern which takes in each advantage of steel and concrete. A field of bridges is no exception, with the plan and construction carried out for the new type of composite bridge, such as a composite cable-stayed bridge and a composite extra dose bridge as a long span bridge, and a composite truss bridge and a corrugated steel plate web bridge as a medium-span bridge, with technological development becoming active in this field. In such a technological trend, a hybrid two-girder structure was devised, a structure consisting of a concrete filled steel pipe for a girder and a precast (PC) floor plate for a floor board, as the girder structure of a long-span cable-stayed bridge in the subject research; also, applicability was examined using, as an example, the composite cable-stayed bridge with hybrid girders employed for the span. This paper reports the result of the analysis of the entire system, the analysis made for the purpose of examining the characteristic and the feasibility of this hybrid girder. The analysis revealed the structural feasibility of the long-span composite cable-stayed bridge using two hybrid girders of concrete-filled steel pipes thus devised. (NEDO)
冯丛; 华旭刚; 胡腾飞; 陈强; 陈政清
2016-01-01
T he cable-stayed Dongting Lake railway bridge under construction was case-studied in this paper. A finite element modeling of the cable-stayed bridge with box-truss composite girder and its vortex-induced vibration were analyzed. T hree finite element schemes for modeling box-truss girder of the bridge,namely the spatial beam model ( SBM) ,spatial plate-beam model( SPBM ) and spatial shell model( SSM ) ,were compared in terms of modal frequency,equivalent mass and mass moment of inertia per unit length. It shows that the results from the SPBM and the SSM are basically the same,while the SBM can't accurately produce the equivalent mass unit length girder for some higher-order lateral modes. T he vortex-induce vibration of the box-truss composite girder was tested in wind tunnel by flexibly mounted rigid sectional model tests. T he results indicate that this cross-section type may experience large-amplitude vertical vortex-induced vibrations at wind attack angle of -3°,which is caused by the vortex shedding at the leading edge of the box-girder part of the cross-section. T he effects of aerodynamic appendix for suppression of vortex-induced vibrations w ere studied and it is found that tw o stabilizers beneath the open orthotropic deck dramatically reduce the vibration amplitude. T he vibration amplitude is within the limit given in design specification when the height of stabilizers is half of the box-girder height; and the vortex-induced vibrations completely diminish when the height of stabilizers is the same as the box-girder height.%以在建的洞庭湖铁路三塔斜拉桥为工程背景，分析了箱桁断面斜拉桥主梁的建模方法以及涡激共振性能。首先比较了主梁建模的空间杆系模型、梁壳组合模型以及三维壳体模型在模态频率、主梁单位长度等效质量和等效质量惯性矩的差异。结果表明，三种模型的模态分析结果基本相近，但空间杆系模型不能准确得到高阶侧弯模
Rensink, Arend; Gorrieri, Roberto
2001-01-01
We investigate criteria to relate specifications and implementations belonging to conceptually different levels of abstraction. For this purpose, we introduce the generic concept of a vertical implementation relation, which is a family of binary relations indexed by a refinement function that maps
FFAG lattice without opposite bends
Trbojevic, Dejan; Courant, Ernest D.; Garren, Al
2000-08-01
A future "neutrino factory" or Muon Collider requires fast muon acceleration before the storage ring. Several alternatives for fast muon acceleration have previously been considered. One of them is the FFAG (Fixed Field Alternating Gradient) synchrotron. The FFAG concept was developed in 1952 by K. R. Symon (ref. 1). The advantages of this design are the fixed magnetic field, large range of particle energy, simple RF; power supplies are simple, and there is no transition energy. But a drawback is that reverse bending magnets are included in the configuration; this increases the size and cost of the ring. Recently some modified FFAG lattice designs have been described where the amount of opposite bending was significantly reduced (ref. 2, ref. 3).
FFAG lattice without opposite bends
Trbojevic, D; Garren, A
2000-01-01
A future 'neutrino factory' or Muon Collider requires fast muon acceleration before the storage ring. Several alternatives for fast muon acceleration have previously been considered. One of them is the FFAG (Fixed Field Alternating Gradient) synchrotron. The FFAG concept was developed in 1952 by K. R. Symon (ref. 1). The advantages of this design are the fixed magnetic field, large range of particle energy, simple RF; power supplies are simple, and there is no transition energy. But a drawback is that reverse bending magnets are included in the configuration; this increases the size and cost of the ring. Recently some modified FFAG lattice designs have been described where the amount of opposite bending was significantly reduced (ref. 2, ref. 3).
Stress analysis of box girders with corrugate steel webs under distorsion%波形钢腹板箱梁畸变应力分析
杨丙文; 黎雅乐; 万水; 张建东
2011-01-01
According to mechanical characteristics of box girders with corrugated steel webs and theory of box girders, the warping normal stress of box girders with corrugated steel webs caused by distortion is studied. Considering that corrugated webs have fold effects, the corrugated webs are regarded as an orthotropic plate. Distortion governing differential equations of box girders with corrugated steel webs are derived under the equilibrium relation of plane force system within them. Their distortion angle and distortion bimoment are obtained using the beam elastic foundation (BEF) method , and then the longitudinal distortion stress is obtained. An analytical example is given to compare two types of box girders, concrete box girders and box girders with corrugated steel webs. The results of the example demonstrate that the box girders with corrugated steel webs have less lateral frame stiffness than concrete ones; thus, the distortional warping normal stress of box girders with corrugated steel webs is larger than that of concrete box girders.%在箱梁理论的基础上,根据波形钢腹板箱梁的力学特性,对波形钢腹板箱梁由畸变引起的翘曲正应力进行了研究.考虑到波形钢腹板具有褶皱效应,把波形钢腹板看作正交异性板,利用波形钢腹板箱梁中各板元平面力系的平衡关系,推导出波形钢腹板箱梁的畸变控制微分方程.采用弹性地基梁法解出波形钢腹板箱梁的畸变角和畸变双力矩,最终得到纵向畸变正应力.通过算例对比分析相同截面的波形钢腹板箱梁和混凝土箱梁的畸变翘曲正应力,计算结果表明,波形钢腹板箱梁相对普通混凝土箱梁的横向框架刚度较小,因此由畸变产生的翘曲正应力大于混凝土箱梁的畸变翘曲正应力.
Performances of super-long span prestressed cable-stayed bridge with CFRP cables and RPC girder
Fang Zhi; Fan Fenghong; Ren Liang
2013-01-01
To discuss the applicability of advanced composite carbon fiber reinforced polymer (CFRP) and ultra-high performance concrete reactive powder concrete (RPC) in super-long span cable-stayed bridges , taking a 1 008 m cable-stayed bridge with steel girders and steel cables as an example,a new cable-stayed bridge in the same span with RPC girders and CFRP cables was designed,in which the cable’s cross section was determined by the principle of equivalent cable capacity and the girder’s cross section was determined in virtual of its stiffness, shear capacity and local stability. Based on the methods of finite element analysis,the comparative analysis of these two cable-stayed bridge schemes about static performances,dynamic performances,stability and wind resis-tance behavior were carried out. The results showed that it was feasible to form a highly efficient,durable concrete cable-stayed bridge with RPC girders and CFRP cables and made its applicable span range expand to 1 000 m long around.
Bending and stretching of plates
Mansfield, E H; Hemp, W S
1964-01-01
The Bending and Stretching of Plates deals with elastic plate theory, particularly on small- and large-deflexion theory. Small-deflexion theory concerns derivation of basic equations, rectangular plates, plates of various shapes, plates whose boundaries are amenable to conformal transformation, plates with variable rigidity, and approximate methods. Large-deflexion theory includes general equations and some exact solutions, approximate methods in large-deflexion theory, asymptotic large-deflexion theories for very thin plates. Asymptotic theories covers membrane theory, tension field theory, a
Effect of sensor placement on operational modal analysis of steel girder bridges
Whelan, Matthew J.; Gangone, Michael V.; Janoyan, Kerop D.
2011-04-01
With the advent and development of low-cost wireless structural health monitoring systems, the task of routinely assessing the in-service condition of highway bridges through distributed sensor-based measurements is an increasingly feasible component of bridge safety and management practice. Bridge monitoring encompasses placement of often a limited number of distributed sensors across a relatively large and complex structural system. Consequently, the selection of proper sensor locations is imperative to extraction of the most value from the recorded measurements. An experimental investigation is presented wherein sensor placement on the superstructure girders or primary beams is contrasted to the response measured on the surface of the bridge deck. The effect on the dataset richness, as evidenced by the modal content, is presented and conclusions regarding optimal placement for this structure type are presented. To affirm the plausibility of the observed responses and conclusions drawn, a finite element analysis is also performed on a model developed from the as-built drawings.
A Damage Prognosis Method of Girder Structures Based on Wavelet Neural Networks
Rumian Zhong
2014-01-01
Full Text Available Based on the basic theory of wavelet neural networks and finite element model updating method, a basic framework of damage prognosis method is proposed in this paper. Firstly, a damaged I-steel beam model testing is used to verify the feasibility and effectiveness of the proposed damage prognosis method. The results show that the predicted results of the damage prognosis method and the measured results are very well consistent, and the maximum error is less than 5%. Furthermore, Xinyihe Bridge in the Beijing-Shanghai Highway is selected as the engineering background, and the damage prognosis is conducted based on the data from the structural health monitoring system. The results show that the traffic volume will increase and seasonal differences will decrease in the next year and a half. The displacement has a slight increase and seasonal characters in the critical section of mid span, but the strain will increase distinctly. The analysis results indicate that the proposed method can be applied to the damage prognosis of girder bridge structures and has the potential for the bridge health monitoring and safety prognosis.
Farzad Shahabian
2013-12-01
Full Text Available This study aims to undertake a statistical study to evaluate the accuracy of nine models that have been previously proposed for estimating the ultimate resistance of plate girders subjected to patch loading. For each model, mean errors and standard errors, as well as the probability of underestimating or overestimating patch load resistance, are estimated and the resultant values are compared one to another. Prior to that, the models are initially calibrated in order to improve interaction formulae using an experimental data set collected from the literature. The models are then analyzed by computing design factors associated with a target risk level (probability of exceedance. These models are compared one to another considering uncertainties existed in material and geometrical properties. The Monte Carlo simulation method is used to generate random variables. The statistical parameters of the calibrated models are calculated for various coefficients of variations regardless of their correlation with the random resistance variables. These probabilistic results are very useful for evaluating the stochastic sensitivity of the calibrated models.
Assessment of seismic performance of skew reinforced concrete box girder bridges
Abdel-Mohti, Ahmed; Pekcan, Gokhan
2013-12-01
The seismic vulnerability of highway bridges remains an important problem and has received increased attention as a consequence of unprecedented damage observed during several major earthquakes. A significant number of research studies have examined the performance of skew bridges under service and seismic loads. The results of these studies are particularly sensitive to modeling assumptions in view of the interacting parameters. In the present study, three-dimensional improved beam-stick models of two-span highway bridges with skew angles varying from 0° to 60° are developed to investigate the seismic response characteristics of skew box girder bridges. The relative accuracy of beam-stick models is verified against counterpart finite element models. The effect of various parameters and conditions on the overall seismic response was examined such as skew angle, ground motion intensity, soil condition, abutment support conditions, bridge aspect ratio, and foundation-base conditions. The study shows that the improved beam-stick models can be used to conduct accurate nonlinear time history analysis of skew bridges. Skew angle and interacting parameters were found to have significant effect on the behavior of skewed highway bridges. Furthermore, the performance of shear keys may have a predominant effect on the overall seismic response of the skew bridges.
Chen, G. W.; Omenzetter, P.
2016-04-01
This paper presents the implementation of an updating procedure for the finite element model (FEM) of a prestressed concrete continuous box-girder highway off-ramp bridge. Ambient vibration testing was conducted to excite the bridge, assisted by linear chirp sweepings induced by two small electrodynamic shakes deployed to enhance the excitation levels, since the bridge was closed to traffic. The data-driven stochastic subspace identification method was executed to recover the modal properties from measurement data. An initial FEM was developed and correlation between the experimental modal results and their analytical counterparts was studied. Modelling of the pier and abutment bearings was carefully adjusted to reflect the real operational conditions of the bridge. The subproblem approximation method was subsequently utilized to automatically update the FEM. For this purpose, the influences of bearing stiffness, and mass density and Young's modulus of materials were examined as uncertain parameters using sensitivity analysis. The updating objective function was defined based on a summation of squared values of relative errors of natural frequencies between the FEM and experimentation. All the identified modes were used as the target responses with the purpose of putting more constrains for the optimization process and decreasing the number of potentially feasible combinations for parameter changes. The updated FEM of the bridge was able to produce sufficient improvements in natural frequencies in most modes of interest, and can serve for a more precise dynamic response prediction or future investigation of the bridge health.
张迅; 王党雄; 李小珍
2015-01-01
为探讨铁路混凝土箱梁箱内空腔共鸣噪声及其影响,以某客运专线32 m预应力混凝土简支箱梁为研究对象,开展实桥振动与噪声试验,分析箱梁振动与噪声的时域特性及频谱特性。采用有限元法建立三维空腔声模型,分析箱内空腔声模态与腔内噪声峰值的关联性。采用边界元法分别建立两端封闭与两端开口的箱梁声学模型,验证箱内空腔共鸣噪声的来源及其影响。结果表明：在特定行车速度下,箱内噪声出现“拍”现象,显著增大箱内噪声,瞬时最大声压可达40 Pa,峰值频率为75.0 Hz；箱内噪声的“拍”现象来源于顶板的振动噪声,顶板的振动峰值频率与箱内空腔垂向声模态频率吻合时,箱内噪声显著增大；由于梁缝的声泄漏特性,箱内空腔共鸣噪声在梁缝处衰减较大,但其对桥梁两侧总体噪声的影响不可忽略。%In order to study the cavity resonance noise of concrete box-girder and its influence,a field test con-cerning vibration and noise of a 32 m PC simply-supported box-girder was carried out,to investigate the time-domain characteristics and frequency spectrum characteristics of vibration and noise of the box-girder.A 3D cavity acoustical model was established based on FEM to analyze the correlation between cavity acoustic mode and cavity noise peak.Two acoustical models for box-girders with closed ends and open ends,were built based on BEM,respectively,to verify the source and influence of cavity resonance noise.Results showed that the“beat”wave phenomenon of cavity noise appeared under a specific train speed,significantly increasing the cavi-ty noise,with the transient maximum sound pressure of cavity noise reaching 40 Pa and the noise peak frequen-cy being 75.0 Hz;The “beat”wave phenomenon of cavity noise derived from the vibration of deck.When the peak vibration frequency of deck matched with the frequency of vertical acoustic modal of the cavity
Garment-Integrated Bend Sensor
Guido Gioberto
2014-09-01
Full Text Available Garment-integrated sensors equip clothes with a smart sensing capability, while preserving the comfort of the user. However, this benefit can be to the detriment of sensing accuracy due to the unpredictability of garment movement (which affects sensor positioning and textile folds (which can affect sensor orientation. However, sensors integrated directly into garments or fabric structures can also be used to detect the movement of the garment during wearing. Specifically, a textile bend sensor could be used to sense folds in the garment. We tested a garment-integrated stitched sensor for five types of folds, stitched on five different weights of un-stretchable denim fabric and analyzed the effects of fold complexity and fabric stiffness, under un-insulated and insulated conditions. Results show that insulation improves the linearity and repeatability of the sensor response, particularly for higher fold complexity. Stiffer fabrics show greater sensitivity, but less linearity. Sensor response amplitude is larger for more complex fold geometries. The utility of a linear bending response (insulated and a binary shorting response (un-insulated is discussed. Overall, the sensor exhibits excellent repeatability and accuracy, particularly for a fiber-based, textile-integrated sensor.
FACTORS INFLUENCING BENDING RIGIDITY OF SUBMERGED VEGETATION
WU Long-hua; YANG Xiao-li
2011-01-01
The bending rigidity of submerged vegetation is closely related with vegetative drag force.This work aims at determining the effects of flow conditions and characteristics of vegetation on the bending rigidity of submerged vegetation.Based on the dimensional analysis method,the factors influencing the bending rigidity of individual submerged vegetation were analyzed.The relationship between the relative bending rigidity and its influencing factors was investigated by experimental observation,and a relative bending rigidity expression for submerged vegetation was obtained by means of multiple linear regression method.The results show that the submerged vegetation has three states under different inflow conditions,and the each critical relative bending rigidity of individual submerged vegetation was determined for the different states of submerged vegetation.
Elastic bending modulus of monolayer graphene
Lu Qiang; Huang Rui [Department of Aerospace Engineering and Engineering Mechanics, University of Texas, Austin, TX 78712 (United States); Arroyo, Marino [Department of Applied Mathematics 3, LaCaN, Universitat Politecnica de Catalunya (UPC), Barcelona 08034 (Spain)
2009-05-21
An analytic formula is derived for the elastic bending modulus of monolayer graphene based on an empirical potential for solid-state carbon atoms. Two physical origins are identified for the non-vanishing bending stiffness of the atomically thin graphene sheet, one due to the bond-angle effect and the other resulting from the bond-order term associated with the dihedral angles. The analytical prediction compares closely with ab initio energy calculations. Pure bending of graphene monolayers into cylindrical tubes is simulated by a molecular mechanics approach, showing slight nonlinearity and anisotropy in the tangent bending modulus as the bending curvature increases. An intrinsic coupling between bending and in-plane strain is noted for graphene monolayers rolled into carbon nanotubes. (fast track communication)
Reliability-based research for failure risks of ship hull girder
无
2008-01-01
In order to find a simple and programmed method to analyze the reliability of hull beams when fatigue and corrosion act on ships, the stress of ships is to be calculated in compliance with the longitudinal bending and cross-section modulus of ship beams. The calculation value of stress is to be compared with the allowable stress in order to gain the actual ship load and margin of safety, and then assess the reliability and failure probability of ship beams. The longitudinal bending moment is a random variab...
Can hook-bending be let off the hook? Bending/unbending of pliant tools by cockatoos.
Laumer, I B; Bugnyar, T; Reber, S A; Auersperg, A M I
2017-09-13
The spontaneous crafting of hook-tools from bendable material to lift a basket out of a vertical tube in corvids has widely been used as one of the prime examples of animal tool innovation. However, it was recently suggested that the animals' solution was hardly innovative but strongly influenced by predispositions from habitual tool use and nest building. We tested Goffin's cockatoo, which is neither a specialized tool user nor a nest builder, on a similar task set-up. Three birds individually learned to bend hook tools from straight wire to retrieve food from vertical tubes and four subjects unbent wire to retrieve food from horizontal tubes. Pre-experience with ready-made hooks had some effect but was not necessary for success. Our results indicate that the ability to represent and manufacture tools according to a current need does not require genetically hardwired behavioural routines, but can indeed arise innovatively from domain general cognitive processing. © 2017 The Authors.
Thermal vertical bimorph actuators and their applications
Sehr, H J
2002-01-01
In this thesis, a novel concept for lateral actuators based on vertical bimorphs is presented. Vertical bimorphs consist of silicon beams side-coated with aluminium, which bend when heated due to the different thermal expansion coefficients of the two materials causing a displacement in the wafer plane. The heating of the actuator is provided by an electrical current through the silicon beam. The simplest implementation of a vertical bimorph actuator is a clamped-clamped beam. To obtain higher deflections, a meander shaped actuator has been designed. By combining four meander actuators, a two-dimensional positioning stage has been realised. The meander actuator has also been applied for normally closed and normally open micro-relays. Analytical calculations and ANSYS simulations have been carried out to predict the physical behaviour of the bimorph devices, including temperature distribution, static deflection, vertical stiffness, thermal time constant and lateral resonances. For both the clamped-clamped beam...
Ovalization of Tubes Under Bending and Compression
Demer, L J; Kavanaugh, E S
1944-01-01
An empirical equation has been developed that gives the approximate amount of ovalization for tubes under bending loads. Tests were made on tubes in the d/t range from 6 to 14, the latter d/t ratio being in the normal landing gear range. Within the range of the series of tests conducted, the increase in ovalization due to a compression load in combination with a bending load was very small. The bending load, being the principal factor in producing the ovalization, is a rather complex function of the bending moment, d/t ratio, cantilever length, and distance between opposite bearing faces. (author)
Numerical simulation for local failure of a steel box girder under blast loading%钢箱梁爆炸冲击局部破坏的数值模拟
蒋志刚; 朱新明; 严波; 姚术健
2013-01-01
The local failure of a steel box girder under blasting loads of vehicle bomb (TNT equivalent 100-500kg)was investigated with the nonlinear finite element software LS-DYNA and the fluid-solid coupling method ALE Multimaterial formulations.The results showed that there are two local failure modes of a steel box girder,one is that the deck and bottom plates rupture locally; the other is that the deck plate ruptures locally and the bottom plate does not rupture but has a local large plastic deformation; the main failure modes of diaphragms are large bending plastic deformation and rupture; the failure parameters increase nonlinearly with increase in explosive TNT equivalent; the impact effect of shock wave within the box on the bottom plate and diaphragms is less than the impact effect of the deck's fragments,the latter is the main cause of the local large plastic deformation and rupture of the bottom plate and diaphragms.%运用LS-DYNA非线性有限元软件,采用ALE多物质流-固耦合算法,研究了汽车炸弹(TNT当量100～500 kg)桥面爆炸冲击作用下钢箱梁的局部破坏.结果表明,钢箱梁局部破坏模式有两种:(1)桥面板和底板均破口；(2)桥面板破口,底板产生局部塑性大变形.隔板的主要破坏模式为弯曲塑性大变形和破口.破坏参数随炸药当量的增加呈非线性增加.箱体内冲击波对底板、隔板的冲击作用相对较小,顶板破片的冲击作用是底板和隔板产生局部塑性大变形和破口的主要原因.
Peeling, sliding, pulling and bending
Lister, John; Peng, Gunnar
2016-11-01
The peeling of an elastic sheet away from thin layer of viscous fluid is a simply-stated and generic problem, that involves complex interactions between the flow and elastic deformation on a range of length scales. Consider an analogue of capillary spreading, where a blister of injected viscous fluid spreads due to tension in the overlying elastic sheet. Here the tension is coupled to the deformation of the sheet, and thus varies in time and space. A key question is whether or not viscous shear stresses ahead of the blister are sufficient to prevent the sheet sliding inwards and relieving the tension. Our asymptotic analysis reveals a dichotomy between fast and slow spreading, and between two-dimensional and axisymmetric spreading. In combination with bending stresses and gravity, which may dominate parts of the flow but not others, there is a plethora of dynamical regimes.
Bending Angle Prediction Model Based on BPNN-Spline in Air Bending Springback Process
Zhefeng Guo; Wencheng Tang
2017-01-01
In order to rapidly and accurately predict the springback bending angle in V-die air bending process, a springback bending angle prediction model on the combination of error back propagation neural network and spline function (BPNN-Spline) is presented in this study. An orthogonal experimental sample set for training BPNN-Spline is obtained by finite element simulation. Through the analysis of network structure, the BPNN-Spline black box function of bending angle prediction is established, an...
A Numerical Study of the Spring-Back Phenomenon in Bending with a Rebar Bending Machine
Chang Hwan Choi
2014-10-01
Full Text Available Recently, the rebar bending methodology started to change from field processing to utilizing rebar bending machines at plant sites prior to transport to the construction locations. Computerized control of rebar plant bending machines provides more accurate and faster bending of rebars than the low quality inefficient field processing alternative. The bending process involves plastic deformation of rebars, where bending stress beyond the yield point of the material is applied. When the bending stress is removed, spring back is caused by the elastic restoring stress. Therefore, an accurate numerical analysis of the spring-back process is required to reduce the bending process errors. The most sensitive factors affecting the spring-back process are the bending radius, the bending angle, the diameter of the rebar, the friction coefficient, and the yielding strength of material. In this paper, we suggest a numerical modeling method using these factors. The finite element modeling of the dynamic mechanical behavior of the material during bending is performed using a commercial dynamic analysis program “DAFUL.” We use the least squares approach to derive the spring-back deflection as a function of the rebar bending parameters.
Study on Fatigue Behavior of Anchorage of Cable and Girder of Long Span Cable-Stayed Bridge
无
2001-01-01
A full scale model test is done and a FEM model is established toinvestigate the fatigue behavior of the Nancha cable-stayed bridge of the Nanjing Second Yangtz River Bridge, a long span steel bridge with a main span of 628 m. The results of test and FEM are analyzed and compared. It is shown that they are in good agreement. It is verified that the fatigue characteristic of the anchorage structure of cable and girder of the bridge satisfies the requirements specified by Chinese, British and American codes.
Girder deformation related phase errors on the undulators for the European X-Ray Free Electron Laser
Yuhui Li
2015-06-01
Full Text Available In long gap tunable undulators, strong magnetic forces always lead to some amount of gap-dependent girder deformation and resulting gap-dependent phase errors. For the undulators for the European XFEL, this problem has been investigated thoroughly and quantitatively. Using the different gap dependencies of suitable shims and pole height tuning, a method is presented which can be applied to reduce the overall gap dependence of the phase error if needed. It is exemplified by tuning one of the undulator segments for the European X-Ray Free Electron Laser back to specs.
Discontinious Galerkin formulations for thin bending problems
Nguyen, T.D.
2008-01-01
A structural thin bending problem is essentially associated with a fourth-order partial differential equation. Within the finite element framework, the numerical solution of thin bending problems demands the use of C^1 continuous shape functions. Elements using these functions are challenging and di
Restorying the Self: Bending toward Textual Justice
Thomas, Ebony Elizabeth; Stornaiuolo, Amy
2016-01-01
In this essay, Ebony Elizabeth Thomas and Amy Stornaiuolo explore new trends in reader response for a digital age, particularly the phenomenon of bending texts using social media. They argue that bending is one form of "restorying," a process by which people reshape narratives to represent a diversity of perspectives and experiences that…
Anharmonic Bend-Stretch Coupling in Water
Lindner, Jörg; Vöhringer, Peter; Pshenichnikov, Maxim S.; Cringus, Dan; Wiersma, Douwe A.; Corkum, Paul; Jonas, David M.; Miller, R.J. Dwayne.; Weiner, Andrew M.
2006-01-01
Following excitation of the H-O-H bending mode of water molecules in solution the stretching mode region is monitored over its entire width. The anharmonic coupling between the two modes results in a substantial change of the transient stretch absorption that decays with the bend depopulation time.
Bandwidth engineering of photonic crystal waveguide bends
Borel, Peter Ingo; Frandsen, Lars Hagedorn; Harpøth, Anders;
2004-01-01
An effective design principle has been applied to photonic crystal waveguide bends fabricated in silicon-on-insulator material using deep UV lithography resulting in a large increase in the low-loss bandwidth of the bends. Furthermore, it is experimentally demonstrated that the absolute bandwidth...
Bends and splitters in graphene nanoribbon waveguides
Zhu, Xiaolong; Yan, Wei; Mortensen, N. Asger
2013-01-01
We investigate the performance of bends and splitters in graphene nanoribbon waveguides. Although the graphene waveguides are lossy themselves, we show that bends and splitters do not induce any additional loss provided that the nanoribbon width is sub-wavelength. We use transmission line theory...
Millett, A. U.
1977-01-01
Combination protractor and scale for measuring tube bends has novel pivot that allows tube to remain in contact with scale arms for all bend angles. Device permits rapid and accurate scribing and measurement of mockup fluid lines to obtain production data.
Plausible cloth animation using dynamic bending model
Chuan Zhou; Xiaogang Jin; Charlie C.L. Wang; Jieqing Feng
2008-01-01
Simulating the mechanical behavior of a cloth is a very challenging and important problem in computer animation. The models of bending in most existing cloth simulation approaches are taking the assumption that the cloth is little deformed from a plate shape.Therefore, based on the thin-plate theory, these bending models do not consider the condition that the current shape of the cloth under large deformations cannot be regarded as the approximation to that before deformation, which leads to an unreal static bending. [This paper introduces a dynamic bending model which is appropriate to describe large out-plane deformations such as cloth buckling and bending, and develops a compact implementation of the new model on spring-mass systems. Experimental results show that wrinkles and folds generated using this technique in cloth simulation, can appear and vanish in a more natural way than other approaches.
Wire and Cable Cold Bending Test
Colozza, Anthony
2010-01-01
One of the factors in assessing the applicability of wire or cable on the lunar surface is its flexibility under extreme cold conditions. Existing wire specifications did not address their mechanical behavior under cold, cryogenic temperature conditions. Therefore tests were performed to provide this information. To assess this characteristic 35 different insulated wire and cable pieces were cold soaked in liquid nitrogen. The segments were then subjected to bending and the force was recorded. Any failure of the insulation or jacketing was also documented for each sample tested. The bending force tests were performed at room temperature to provide a comparison to the change in force needed to bend the samples due to the low temperature conditions. The results from the bending tests were plotted and showed how various types of insulated wire and cable responded to bending under cold conditions. These results were then used to estimate the torque needed to unroll the wire under these low temperature conditions.
49 CFR 195.212 - Bending of pipe.
2010-10-01
... 49 Transportation 3 2010-10-01 2010-10-01 false Bending of pipe. 195.212 Section 195.212... PIPELINE Construction § 195.212 Bending of pipe. (a) Pipe must not have a wrinkle bend. (b) Each field bend must comply with the following: (1) A bend must not impair the serviceability of the pipe. (2) Each...
A derivation of the generalized model of strains during bending of metal tubes at bending machines
Śloderbach Z.
2014-01-01
According to the postulate concerning a local change of the “actual active radius” with a bending angle in the bend zone, a generalized model of strain during metal tube bending was derived. The tubes should be subjected to bending at tube bending machines by the method of wrapping at the rotating template and with the use of a lubricated steel mandrel. The model is represented by three components of strain in the analytic form, including displacement of the neutral axis. Generalization of th...
Lipeng An
2016-07-01
Full Text Available To systematically study the vehicle–bridge coupled dynamic response and its change rule with different parameters, a vehicle model with seven degrees of freedom was built and the total potential energy of vehicle space vibration system was deduced. Considering the stimulation of road roughness, the dynamic response equation of vehicle–bridge coupled system was established in accordance with the elastic system principle of total potential energy with stationary value and the “set-in-right-position” rule. On the basis of the self-compiled Fortran program and bridge engineering, the dynamic response of long-span continuous girder bridge under vehicle load was studied. This study also included the calculation of vehicle impact coefficient, evaluation of vibration comfort, and analysis of dynamic response parameters. Results show the impact coefficient changes with lane number and is larger than the value calculated by the “general code for design of highway bridges and culverts (China”. The Dieckmann index of bridge vibration is also related to lane number, and the vibration comfort evaluation is good in normal conditions. The relevant conclusions from parametric analyses have practical significance to dynamic design and daily operation of long-span continuous girder bridges in expressways. Safety and comfort are expected to improve significantly with further control of the vibration of vehicle–bridge system.
Zheheng Chen
2015-01-01
Full Text Available Structural health monitoring (SHM has attracted much attention in recent years, which enables early warnings of structural failure, condition assessments, and rational maintenance/repair strategies. In the context of bridges, many long-span steel bridges in China have been installed with the SHM systems; however, the applications of the SHM in prestressed concrete (PSC bridges are still rather limited. On the other hand, the PSC box girder bridges are extensively used in highway and railway systems and premature damage of these bridges is often reported, resulting in considerable maintenance and/or replacement costs. First, this paper presents a state-of-art review on the SHM of long-span PSC bridges. Monitoring strategies, methods, and previous applications for these bridges are summarized and discussed. In order to well capture the behavior of the bridge during its whole life and to maximize the use of sensors, a life-cycle monitoring strategy is proposed, in which the sensor layout is determined according to requirements for construction monitoring, completion test, and in-service monitoring. A case study is made on a three-span PSC box girder bridge in China. The system configuration, sensor layout, and data communications, and so forth, are presented. The up-to-date monitored structural responses are analyzed and compared with the design values.
Damage Detection for Long-Span Cable-Stayed Bridge
Zhao Ling; Li Aiqun; Miao Changqing; Wang Yonglan
2006-01-01
Based on the updated finite-element model of a cable-stayed bridge, this study investigates the technique of identifying damage existing in cable or girder by means of numerical simulation. The modal analysis is performed to identify the changes in modal frequencies and curvatures caused by damage, and the static analysis is executed to detect the influence of damage on cable force. The results indicate a relatively significant decrease in frequencies of lower vertical bending modes due to the damage in cable and little change of frequencies due to damage in girder. Different sensitivities to the location of damaged cable are observed from the frequency changes of different bending modes, which can be used to initially locate the damaged cable. The damage in either cable or girder can be further localized by the most significant change in curvature of girder. The damage occurred in a cable produces a remarkable change in force of nearby cables, whereas the damage in girder brings little change of cable forces. In addition, a pragmatic approach for localizing the damage in girder or cable is proposed based on a comprehensive utilization of the changes in frequency of vertical bending modes, modal curvature of girder, and force in cables.
Low Loss S-Bend Structure With Tapered Curved Waveguides
无
2003-01-01
A novel S-bend with tapered curved waveguides is proposed. The normalized transmitted power is greater than the conventional bend with weakly guided waveguides. Small size and low loss can be reached by the proposed S-bend.
Bending stresses in Facetted Glass Shells
Bagger, Anne; Jönsson, Jeppe; Almegaard, Henrik
2008-01-01
A shell structure of glass combines a highly effective structural principle with a material of optimal permeability to light. A facetted shell structure has a piecewise plane geometry, and together the facets form an approximation to a curved surface. A distributed load on a plane-based facetted...... structure will locally cause bending moments in the loaded facets. The bending stresses are dependent on the stiffness of the joints. Approximate solutions are developed to estimate the magnitude of the bending stresses. A FE-model of a facetted glass shell structure is used to validate the expressions...
Bidirectional bending splitter of designer surface plasmons
Jin Zhou, Yong; Jiang, Quan; Jun Cui, Tie
2011-09-01
We propose and experimentally verify a bidirectional bending splitter of designer surface plasmons which is composed of two metallic gratings of trapezoid grooves. A metal wire is used to excite the designer surface plasmons propagating along the gratings. A full-wave numerical method has been used to simulate the performance of the bending splitter. The experimental verifications in the microwave frequencies have excellent agreements to the simulations. It is demonstrated that the splitter can not only split the electromagnetic waves at different frequencies, but also guide the electromagnetic waves effectively for large-angle bending.
Longqi Zhang
2014-09-01
Full Text Available The wind induced vibration is one of the key technical problems for long-span bridge design. Therefore, a study on the aerodynamic characteristics of a single-pylon cable-stayed bridge girder is carried out in this paper. The aerostatic coefficient of the bridge girder, including both construction state and service state, is investigated by wind tunnel test with varying wind attack angle. Then based on the computational fluid dynamics (CFD method, the flow field around the bridge girder is visualized numerically. The risk of vortex-induced vibration (VIV is qualitatively evaluated by analyzing the flow features and by considering the Scruton number (Sc. Later a dynamic section model is tested in wind tunnel and the VIV phenomenon is observed subsequently. Results show that the aerodynamic stability is assured by the positive slope of the lift coefficient. The VIV response is influenced by the structural damping and the bridge accessory. The amplitude of VIV response can be lower by increasing the structural damping. The maintenance track rail of the bridge girder also does some good for suppressing the VIV as long as the track rail is located at the appropriate place.
桥面铺装与小箱梁的共同作用试验%Experiment of Coaction of Bridge Deck Pavement and Small Box Girder
钱寅泉; 周正茂; 袁桂芳; 王素娟
2012-01-01
Load tests on a single small box girder and a bridge were carried out to evaluate the effects of deck pavement by comparing the deflections of the girders before and after the pavement surfaced. The comprehensive elastic modulus was obtained from the test before pavement surfaced, and the coaction degree of the bridge deck pavement and the girders was obtained by comparing the flexural inertia moment corresponding to the deflection in the test after pavement surfaced with the theoretical flexural inertia moment corresponding to the supposed thickness of the pavement in work. The results from these tests show that (1) the rough interface could greatly improve the coaction degree of bridge deck pavement with girders, which could reach 100% ; (2) in general cases, the extent of the coaction of bridge deck pavement with girders could reach 70% , and for a pavement with thickness of 8 cm, the thickness of the pavement in coaction could be taken as 60% or 3 cm in thickness could be substracted from the pavement in design; (3 ) the pavement could improve the uniformity of the transverse load distribution. Load tests on a single small box girder and a bridge were carried out to evaluate the effects of deck pavement by comparing the deflections of the girders before and after the pavement surfaced. The comprehensive elastic modulus was obtained from the test before pavement surfaced, and the coaction degree of the bridge deck pavement and the girders was obtained by comparing the flexural inertia moment corresponding to the deflection in the test after pavement surfaced with the theoretical flexural inertia moment corresponding to the supposed thickness of the pavement in work. The results from these tests show that (1) the rough interface could greatly improve the coaction degree of bridge deck pavement with girders, which could reach 100% ; (2) in general cases, the extent of the coaction of bridge deck pavement with girders could reach 70% , and for a pavement with
... sleeve; Gastrectomy - greater curvature; Gastrectomy - parietal; Gastric reduction; Vertical gastroplasty ... together using surgical staples. This creates a long vertical tube or banana-shaped stomach. The surgery does ...
EFFECT OF CHANNEL BENDS ON TRANSVERSE MIXING
user
1986-09-01
Sep 1, 1986 ... The first study of transverse mixing in bends of turbulent open channel flows ... Rozovskii's transverse velocity distribution for fully developed turbulent flow ... Yotsukura et al (3) employed a simulation procedure to predict the.
Bending artificial muscle from nylon filaments
Mirvakili, Seyed M.; Hunter, Ian W.
2016-04-01
Highly oriented nylon and polyethylene fibers shrink in length and expand in diameter when heated. Using this property, in this work, for the first time we are introducing a type of bending artificial muscle from nylon filaments such as fishing line. Reversible radius of curvature of 0.23 mm-1 was achieved with maximum reversible bending amplitude of 115 mm for the nylon bending actuator. Peak force of up to 2040 mN was measured with a catch-state force of up to 40% of the active force. A 3 dB roll-off frequency of around 0.7 Hz was observed in the frequency response of the bending actuator in water.
Variability of Darcian Flux in the Hyporheic Zone at a Natural Channel Bend
Shaofeng Xu
2017-02-01
Full Text Available Channel bends are one of the most important characteristic features of natural streams. These bends often create the conditions for a hyporheic zone, which has been recognized as a critical component of stream ecosystems. The streambed vertical hydraulic conductivity (Kv, vertical hydraulic gradient (VHG and Darcian flux (DF in the hyporheic zone were estimated at 61 locations along a channel bend of the Beiluo River during July 2015 and January 2016. All the streambed attributes showed great spatial variability along the channel bend. Both upward fluxes and downward fluxes occurred during the two test periods, most of studied stream sections were controlled by downwelling, indicating stream water discharge into the subsurface. The average downward flux was higher at the downstream side than at the upstream side of the channel bend, especially in July 2015. The distribution of streambed sediment grain size has a significant influence on the variability of Kv; high percentages of silt and clay sediments generally lead to low Kv values. Higher Kv at the depositional left bank at the upstream site shifted toward the erosional right bank at the downstream site, with Kv values positively correlated with the water depth. This study suggested that the variabilities of Kv and VHG were influenced by the stream geomorphology and that the distribution of Kv was inversely related, to a certain extent, to the distribution of VHG across the channel bend. Kv and VHG were found to have opposite effects on the DF, and the close relationship between Kv and DF indicated that the water fluxes were mainly controlled by Kv.
This is a slice of a LEP dipole bending magnet, made as a concrete and iron sandwich The bending field needed in LEP is small (about 1000 Gauss), equivalent to two of the magnets people stick on fridge doors. Because it is very difficult to keep a low field steady, a high field was used in iron plates embedded in concrete. A CERN breakthrough in magnet design, LEP dipoles can be tuned easily and are cheaper than conventional magnets.
This is a slice of a LEP dipole bending magnet, made as a concrete and iron sandwich. The bending field needed in LEP is small (about 1000 Gauss), equivalent to two of the magnets people stick on fridge doors. Because it is very difficult to keep a low field steady, a high field was used in iron plates embedded in concrete. A CERN breakthrough in magnet design, LEP dipoles can be tuned easily and are cheaper than conventional magnets.
Pipes under internal pressure and bending
Catinaccio, A
2009-01-01
This article covers the general behaviour of a straight uniform pipe, with built-in open ends, subject to internal pressure and in plane bending or curvature. It is intended as a summary of the basic equations driving the unintuitive phenomena of bending and instability of pipes under internal pressure. The analysis covers in addition the investigation of opposite pressure stabilisation effects that can be observed in some orthotropic material pipes like composite pressure hoses.
Zhang, Xun; Li, Xiaozhen; Hao, Hong; Wang, Dangxiong; Li, Yadong
2016-04-01
A side effect of high-speed railway and urban rail transit systems is the associated vibration and noise. Since the use of concrete viaducts is predominant in railway construction due to scarce land resources, low-frequency (20-200 Hz) structure-radiated noise from concrete bridges is a principal concern. Although it is the most commonly used bridge type, the mechanism of noise emission from box-shaped bridge girders when subjected to impact forces from moving trains, which sounds like beating a drum, has not been well studied. In this study, a field measurement was first made on a simply-supported box-shaped bridge to record the acceleration of the slabs and the associated sound pressures induced by running trains. These data indicated that a significant beat-wave noise occurred in the box-shaped cavity when the train speed was around 340 km/h, which arose from the interference between two sound waves of 75.0 Hz and 78.8 Hz. The noise leakage from the bridge expansion joint was serious and resulted in obvious noise pollution near the bridge once the beat-wave noise was generated in the cavity. The dominant frequency of the interior noise at 75.0 Hz was confirmed from the spectrum of the data and the modal analysis results, and originated from the peak vibration of the top slab due to resonance and the first-order vertical acoustic mode, which led to cavity resonance, amplifying the corresponding noise. The three-dimensional acoustic modes and local vibration modes of the slab were calculated by using the finite element method. A simplified vehicle-track-bridge coupling vibration model was then developed to calculate the wheel-rail interaction force in a frequency range of 20-200 Hz. Numerical simulations using the boundary element method confirmed the cavity resonance effect and the numerical results agreed well with the data. Based on the calibrated numerical model, three noise reduction measures, i.e., adding a horizontal baffle in the interior cavity, narrowing
姚术健; 蒋志刚; 卢芳云; 张舵; 赵楠
2015-01-01
采用ALE（Arbitrary Lagrangian Eulerian，ALE）多物质流固耦合算法，对汽车炸弹（TNT当量200 kg～1500 kg）在双层桥梁下层桥面典型位置爆炸的局部破坏效应进行了数值模拟，研究了内爆炸冲击作用下钢箱梁的响应过程、破坏模式、破坏参数及其主要影响因素。结果表明：破坏模式及破坏参数与爆炸位置和TNT当量密切相关，爆炸位置对桥梁主要受力体系的受损程度影响较为明显，加劲肋对其垂直方向的破口具有约束作用，箱体对冲击波的约束效应使破坏作用加剧。合理设置加劲肋、加强重要构件和设置防爆层等措施有利于提高桥梁结构抗爆能力。%The response process,failure modes and damage parameters of a double deck steel box girder subjected to internal blast loading of vehicle bombs (TNT equivalent 200kg&1500kg)were simulated by using the ALE (Arbitrary Lagrangian Eulerian)multi-material fluid-solid coupling arithmetic.In the simulation,three typical blast locations on the lower deck were considered.The results show that:the failure modes and damage parameters have a clear correlation with the TNT weight and blast location,and the explosion locations have strong effects on the damage degree of steel trusses. Stiffening ribs can restrict the crack in its vertical direction.The damage effects will be intensified by the restriction of the box-shaped girder.Some useful measurements were also proposed which can help engineers in bridge designing and protection consideration against possible explosion events.
A transparent bending-insensitive pressure sensor
Lee, Sungwon; Reuveny, Amir; Reeder, Jonathan; Lee, Sunghoon; Jin, Hanbit; Liu, Qihan; Yokota, Tomoyuki; Sekitani, Tsuyoshi; Isoyama, Takashi; Abe, Yusuke; Suo, Zhigang; Someya, Takao
2016-05-01
Measuring small normal pressures is essential to accurately evaluate external stimuli in curvilinear and dynamic surfaces such as natural tissues. Usually, sensitive and spatially accurate pressure sensors are achieved through conformal contact with the surface; however, this also makes them sensitive to mechanical deformation (bending). Indeed, when a soft object is pressed by another soft object, the normal pressure cannot be measured independently from the mechanical stress. Here, we show a pressure sensor that measures only the normal pressure, even under extreme bending conditions. To reduce the bending sensitivity, we use composite nanofibres of carbon nanotubes and graphene. Our simulations show that these fibres change their relative alignment to accommodate bending deformation, thus reducing the strain in individual fibres. Pressure sensitivity is maintained down to a bending radius of 80 μm. To test the suitability of our sensor for soft robotics and medical applications, we fabricated an integrated sensor matrix that is only 2 μm thick. We show real-time (response time of ∼20 ms), large-area, normal pressure monitoring under different, complex bending conditions.
Bending sound in graphene: Origin and manifestation
Adamyan, V.M., E-mail: vadamyan@onu.edu.ua [Department of Theoretical Physics, Odessa I.I. Mechnikov National University, 2 Dvoryanska St., Odessa 65026 (Ukraine); Bondarev, V.N., E-mail: bondvic@onu.edu.ua [Department of Theoretical Physics, Odessa I.I. Mechnikov National University, 2 Dvoryanska St., Odessa 65026 (Ukraine); Zavalniuk, V.V., E-mail: vzavalnyuk@onu.edu.ua [Department of Theoretical Physics, Odessa I.I. Mechnikov National University, 2 Dvoryanska St., Odessa 65026 (Ukraine); Department of Fundamental Sciences, Odessa Military Academy, 10 Fontanska Road, Odessa 65009 (Ukraine)
2016-11-11
Highlights: • The origin of sound-like dispersion of graphene bending mode is disclosed. • The speed of graphene bending sound is determined. • The renormalized graphene bending rigidity is derived. • The intrinsic corrugations of graphene are estimated. - Abstract: It is proved that the acoustic-type dispersion of bending mode in graphene is generated by the fluctuation interaction between in-plane and out-of-plane terms in the free energy arising with account of non-linear components in the graphene strain tensor. In doing so we use an original adiabatic approximation based on the alleged (confirmed a posteriori) significant difference of sound speeds for in-plane and bending modes. The explicit expression for the bending sound speed depending only on the graphene mass density, in-plane elastic constants and temperature is deduced as well as the characteristics of the microscopic corrugations of graphene. The obtained results are in good quantitative agreement with the data of real experiments and computer simulations.
A transparent bending-insensitive pressure sensor.
Lee, Sungwon; Reuveny, Amir; Reeder, Jonathan; Lee, Sunghoon; Jin, Hanbit; Liu, Qihan; Yokota, Tomoyuki; Sekitani, Tsuyoshi; Isoyama, Takashi; Abe, Yusuke; Suo, Zhigang; Someya, Takao
2016-05-01
Measuring small normal pressures is essential to accurately evaluate external stimuli in curvilinear and dynamic surfaces such as natural tissues. Usually, sensitive and spatially accurate pressure sensors are achieved through conformal contact with the surface; however, this also makes them sensitive to mechanical deformation (bending). Indeed, when a soft object is pressed by another soft object, the normal pressure cannot be measured independently from the mechanical stress. Here, we show a pressure sensor that measures only the normal pressure, even under extreme bending conditions. To reduce the bending sensitivity, we use composite nanofibres of carbon nanotubes and graphene. Our simulations show that these fibres change their relative alignment to accommodate bending deformation, thus reducing the strain in individual fibres. Pressure sensitivity is maintained down to a bending radius of 80 μm. To test the suitability of our sensor for soft robotics and medical applications, we fabricated an integrated sensor matrix that is only 2 μm thick. We show real-time (response time of ∼20 ms), large-area, normal pressure monitoring under different, complex bending conditions.
Oshio, M.; Nakano, R.; Niihara, Y.; Yano, K.; Takeda, T. [Kajima Corp., Tokyo (Japan)
1995-12-20
A PC cable-stayed bridge under extension construction having long span length may have long-cycle vibration generated because of wind. The vibration puts workers working on main girders into a state of seasick causing the workability to drop. Therefore, with an objective to reduce vibration occurring on the main girders during construction, discussions were given on application of an active type vertical vibration absorbing device. The vibration absorbing device is an active system that a weight is driven vertically by a hydraulic actuator. The device was developed with a target that damping ratio when a maximum extension is 120 m becomes three times that when no vibration is absorbed for a 5-span continuous PC cable-stayed bridge with a length of 675 m, a central span of 260 m, and a width of 11 m. A cage housing the weight is connected with the actuator at its top by using pins, and the weight is supported being suspended from the top of the actuator. Vibration is absorbed by utilizing reactive force generated when the weight is driven vertically by the hydraulic actuator. The hydraulic actuator contains a gas spring that supports the dead weight of the weight. Experiments have verified the effectiveness of the vertical vibration absorbing device. 4 refs., 12 figs., 3 tabs.
Inhibition of the gravitropic bending response of flowering shoots by salicylic acid.
Friedman, Haya; Meir, Shimon; Halevy, Abraham H; Philosoph-Hadas, Sonia
2003-10-01
The upward gravitropic bending of cut snapdragon, lupinus and anemone flowering shoots was inhibited by salicylic acid (SA) applied at 0.5 mM and above. This effect was probably not due to acidification of the cytoplasm, since other weak acids did not inhibit bending of snapdragon shoots. In order to study its mode of inhibitory action, we have examined in cut snapdragon shoots the effect of SA on three processes of the gravity-signaling pathway, including: amyloplast sedimentation, formation of ethylene gradient across the stem, and differential growth response. The results show that 1 mM SA inhibited differential ethylene production rates across the horizontal stem and the gravity-induced growth, without significantly inhibiting vertical growth or amyloplast sedimentation following horizontal placement. However, 5 mM SA inhibited all three gravity-induced processes, as well as the growth of vertical shoots, while increasing flower wilting. It may, therefore, be concluded that SA inhibits bending of various cut flowering shoots in a concentration-dependent manner. Thus, at a low concentration SA exerts its effect in snapdragon shoots by inhibiting processes operating downstream to stimulus sensing exerted by amyloplast sedimentation. At a higher concentration SA inhibits bending probably by exerting general negative effects on various cellular processes.
Forming characteristics of thin-walled tube bending process with small bending radius
LI Heng; YANG He; ZHAN Mei; GU Rui-Jie
2006-01-01
Currently requirements of thin-walled tube with small bending radius cause the defects such as wrinkling,overthinning and cross-section distortion more prone to occur in bending process. Based on the analysis of the forming characteristics by analytical and experimental methods,a complete 3D elastic-plastic FEM model of the process was developed using ABAQUS/Explicit code,including bending process,balls retracting and unloading process,and thus the plastic deformation characteristics with small bending radius were investigated. The main results show that: 1) The utmost deformation feature of the NC bending process is its continuous progressive deformation. 2) The occurring conditions of the defects such as wrinkling and tension instability in the process are obtained. The wrinkling is traditional on the double compressive stresses state and the tension instability is on the double tension stresses state. 3) The enhanced non-uniform deformation in thin-walled tube with small bending radius is demonstrated by comparing the stress/ strains distributions under the 1.5D and 1D bending conditions. 4) For 1D small bending process,a new method-"stepped mandrel retraction" is proposed to improve the bending quality in experiment according to the FE simulation. The simulation results are verified by experiment.
New Equation for Bending Development of Arbitrary Rods and Application to Palm Fronds Bending
Abdullah, Mikrajuddin
2016-01-01
A new general equation to explain bending of arbitrary rods (from arbitrary materials, cross sections, densities, strengthnesses, bending angles, etc) was proposed. This equation can solve several problems found in classical equations, which have many limitations such as only applies for small bending angles or must be solved using very complex schemes. Experiments were also conducted to confirm the theoretical predictions. The equation might be used to explain bending of palm fronds in a very simple way. The proposed equation may be used to obtain solution of several problems which are usually obtain with iteration procedures.
Yang, Peng-Fei; Sanno, Maximilian; Ganse, Bergita; Koy, Timmo; Brüggemann, Gert-Peter; Müller, Lars Peter; Rittweger, Jörn
2014-01-01
Bending, in addition to compression, is recognized to be a common loading pattern in long bones in animals. However, due to the technical difficulty of measuring bone deformation in humans, our current understanding of bone loading patterns in humans is very limited. In the present study, we hypothesized that bending and torsion are important loading regimes in the human tibia. In vivo tibia segment deformation in humans was assessed during walking and running utilizing a novel optical approach. Results suggest that the proximal tibia primarily bends to the posterior (bending angle: 0.15°-1.30°) and medial aspect (bending angle: 0.38°-0.90°) and that it twists externally (torsion angle: 0.67°-1.66°) in relation to the distal tibia during the stance phase of overground walking at a speed between 2.5 and 6.1 km/h. Peak posterior bending and peak torsion occurred during the first and second half of stance phase, respectively. The peak-to-peak antero-posterior (AP) bending angles increased linearly with vertical ground reaction force and speed. Similarly, peak-to-peak torsion angles increased with the vertical free moment in four of the five test subjects and with the speed in three of the test subjects. There was no correlation between peak-to-peak medio-lateral (ML) bending angles and ground reaction force or speed. On the treadmill, peak-to-peak AP bending angles increased with walking and running speed, but peak-to-peak torsion angles and peak-to-peak ML bending angles remained constant during walking. Peak-to-peak AP bending angle during treadmill running was speed-dependent and larger than that observed during walking. In contrast, peak-to-peak tibia torsion angle was smaller during treadmill running than during walking. To conclude, bending and torsion of substantial magnitude were observed in the human tibia during walking and running. A systematic distribution of peak amplitude was found during the first and second parts of the stance phase.
Bend-insensitive optical fibers for FTTH applications
Li, Ming-Jun
2009-01-01
This paper reviews recent development in bend-insensitive fibers for fiber-to-the-home (FTTH) applications. First, requirements for bend-insensitive fibers are discussed. Then different design approaches for reducing fiber bending loss are described and compared. A new bend-insensitive fiber using the nano-engineered ring design is presented in detail.
Hou, Tsung-Chin; Gao, Wei-Yuan; Chang, Chia-Sheng; Zhu, Guan-Rong; Su, Yu-Min
2017-04-01
The three-span steel-arch-steel-girder Jiaxian Bridge was newly constructed in 2010 to replace the former one that has been destroyed by Typhoon Sinlaku (2008, Taiwan). It was designed and built to continue the domestic service requirement, as well as to improve the tourism business of the Kaohsiung city government, Taiwan. This study aimed at establishing the baseline model of Jiaxian Bridge for hazardous scenario simulation such as typhoons, floods and earthquakes. Necessities of these precaution works were attributed to the inherent vulnerability of the sites: near fault and river cross. The uncalibrated baseline bridge model was built with structural finite element in accordance with the blueprints. Ambient vibration measurements were performed repeatedly to acquire the elastic dynamic characteristics of the bridge structure. Two frequency domain system identification algorithms were employed to extract the measured operational modal parameters. Modal shapes, frequencies, and modal assurance criteria (MAC) were configured as the fitting targets so as to calibrate/update the structural parameters of the baseline model. It has been recognized that different types of structural parameters contribute distinguishably to the fitting targets, as this study has similarly explored. For steel-arch-steel-girder bridges in particular this case, joint rigidity of the steel components was found to be dominant while material properties and section geometries relatively minor. The updated model was capable of providing more rational elastic responses of the bridge superstructure under normal service conditions as well as hazardous scenarios, and can be used for manage the health conditions of the bridge structure.
Finite Element Simulation of Magnesium Alloy AZ31 Tube Bending
Wu Wenyun
2016-01-01
Full Text Available A finite element method based model has been developed for magnesium alloy AZ31 tube bending process simulation, using the tensile (for bend outer radius and compressive (for bend inner radius properties of the AZ31 alloy at the bending temperature of 150°C. The results shown that very high compressive stresses are developed in the bend inner radius, limiting the minimum bend radius for the AZ31 tube. The simulation results suggest the minimum centerline bend radius to the tube outer diameter ratio is 1.5 to 2. The maximum diameter to thickness ratio is 30.
Tunable thermoelectric properties in bended graphene nanoribbons
Chang-Ning, Pan; Jun, He; Mao-Fa, Fang
2016-07-01
The ballistic thermoelectric properties in bended graphene nanoribbons (GNRs) are systematically investigated by using atomistic simulation of electron and phonon transport. We find that the electron resonant tunneling effect occurs in the metallic-semiconducting linked ZZ-GNRs (the bended GNRs with zigzag edge leads). The electron-wave quantum interference effect occurs in the metallic-metallic linked AA-GNRs (the bended GNRs with armchair edge leads). These different physical mechanisms lead to the large Seebeck coefficient S and high electron conductance in bended ZZ-GNRs/AA-GNRs. Combined with the reduced lattice thermal conduction, the significant enhancement of the figure of merit ZT is predicted. Moreover, we find that the ZTmax (the maximum peak of ZT) is sensitive to the structural parameters. It can be conveniently tuned by changing the interbend length of bended GNRs. The magnitude of ZT ranges from the 0.15 to 0.72. Geometry-controlled ballistic thermoelectric effect offers an effective way to design thermoelectric devices such as thermocouples based on graphene. Project supported by the National Natural Science Foundation of China (Grant No. 61401153) and the Natural Science Foundation of Hunan Province, China (Grant Nos. 2015JJ2050 and 14JJ3126).
Pure plate bending in couple stress theories
Hadjesfandiari, Ali R; Dargush, Gary F
2016-01-01
In this paper, we examine the pure bending of plates within the framework of modified couple stress theory (M-CST) and consistent couple stress theory (C-CST). In this development, it is demonstrated that M-CST does not describe pure bending of a plate properly. Particularly, M-CST predicts no couple-stresses and no size effect for the pure bending of the plate into a spherical shell. This contradicts our expectation that couple stress theory should predict some size effect for such a deformation pattern. Therefore, this result clearly demonstrates another inconsistency of indeterminate symmetric modified couple stress theory (M-CST), which is based on considering the symmetric torsion tensor as the curvature tensor. On the other hand, the fully determinate skew-symmetric consistent couple stress theory (C-CST) predicts results for pure plate bending that tend to agree with mechanics intuition and experimental evidence. Particularly, C-CST predicts couple-stresses and size effects for the pure bending of the ...
Tunable thermoelectric properties in bended graphene nanoribbons
潘长宁; 何军; 方卯发
2016-01-01
The ballistic thermoelectric properties in bended graphene nanoribbons (GNRs) are systematically investigated by using atomistic simulation of electron and phonon transport. We find that the electron resonant tunneling effect occurs in the metallic–semiconducting linked ZZ-GNRs (the bended GNRs with zigzag edge leads). The electron-wave quan-tum interference effect occurs in the metallic–metallic linked AA-GNRs (the bended GNRs with armchair edge leads). These different physical mechanisms lead to the large Seebeck coefficient S and high electron conductance in bended ZZ-GNRs/AA-GNRs. Combined with the reduced lattice thermal conduction, the significant enhancement of the figure of merit ZT is predicted. Moreover, we find that the ZTmax (the maximum peak of ZT) is sensitive to the structural parameters. It can be conveniently tuned by changing the interbend length of bended GNRs. The magnitude of ZT ranges from the 0.15 to 0.72. Geometry-controlled ballistic thermoelectric effect offers an effective way to design thermoelectric devices such as thermocouples based on graphene.
2010-11-24
... Forest Service Bend/Ft. Rock Ranger District; Deschutes National Forest; Deschutes County, OR; West Bend... Jeffries, District Ranger, Bend-Fort Rock Ranger District, Red Oaks Square, 1230 NE. Third Street, Suite A...-Fort Rock Ranger District, Red Oaks Square, 1230 NE. Third Street, Suite A-262, Bend, Oregon 97701...
Bending Angle Prediction Model Based on BPNN-Spline in Air Bending Springback Process
Zhefeng Guo
2017-01-01
Full Text Available In order to rapidly and accurately predict the springback bending angle in V-die air bending process, a springback bending angle prediction model on the combination of error back propagation neural network and spline function (BPNN-Spline is presented in this study. An orthogonal experimental sample set for training BPNN-Spline is obtained by finite element simulation. Through the analysis of network structure, the BPNN-Spline black box function of bending angle prediction is established, and the advantage of BPNN-Spline is discussed in comparison with traditional BPNN. The results show a close agreement with simulated and experimental results by application examples, which means that the BPNN-Spline model in this study has higher prediction accuracy and better applicable ability. Therefore, it could be adopted in a numerical control bending machine system.
Bending and Breathing Modes of the Galactic Disk
Widrow, Lawrence M; Chequers, Matthew H; Cheng, Edward
2014-01-01
We explore the hypothesis that a passing satellite or dark matter subhalo has excited coherent oscillations of the Milky Way's stellar disk in the direction perpendicular to the Galactic midplane. This work is motivated by recent observations of spatially dependent bulk vertical motions within ~ kpc of the Sun. A satellite can transfer a fraction of its orbital energy to the disk stars as it plunges through the Galactic midplane thereby heating and thickening the disk. Bulk motions arise during the early stages of such an event when the disk is still in an unrelaxed state. We present simple toy-model calculations and simulations of disk-satellite interactions, which show that the response of the disk depends on the relative velocity of the satellite. When the component of the satellite's velocity perpendicular to the disk is small compared with that of the stars, the perturbation is predominantly a bending mode. Conversely, breathing and higher order modes are excited when the vertical velocity of the satelli...
Disk heating and bending instability in galaxies with counterrotation
Khoperskov, Sergey
2016-01-01
With the help of high-resolution long-slit and integral-field spectroscopy observations, the number of confirmed cases of galaxies with counterrotation is increasing rapidly. The evolution of such counterrotating galaxies remains far from being well understood. In this paper we study the dynamics of counterrotating collisionless stellar disks by means of $N$-body simulations. We show that, in the presence of counterrotation, an otherwise gravitationally stable disk can naturally generate bending waves accompanied by strong disk heating across the disk plane, that is in the vertical direction. Such conclusion is found to hold even for dynamically warm systems with typical values of the initial vertical-to-radial velocity dispersion ratio $\\sigma_{\\rm R}/\\sigma_{\\rm z} \\approx 0.5$, for which the role of pressure anisotropy should be unimportant. We note that, during evolution, the $\\sigma_{\\rm R}/\\sigma_{\\rm z}$ ratio tends to rise up to values close to unity in the case of locally Jeans-stable disks, whereas ...
Robotic Arm Comprising Two Bending Segments
Mehling, Joshua S.; Difler, Myron A.; Ambrose, Robert O.; Chu, Mars W.; Valvo, Michael C.
2010-01-01
The figure shows several aspects of an experimental robotic manipulator that includes a housing from which protrudes a tendril- or tentacle-like arm 1 cm thick and 1 m long. The arm consists of two collinear segments, each of which can be bent independently of the other, and the two segments can be bent simultaneously in different planes. The arm can be retracted to a minimum length or extended by any desired amount up to its full length. The arm can also be made to rotate about its own longitudinal axis. Some prior experimental robotic manipulators include single-segment bendable arms. Those arms are thicker and shorter than the present one. The present robotic manipulator serves as a prototype of future manipulators that, by virtue of the slenderness and multiple- bending capability of their arms, are expected to have sufficient dexterity for operation within spaces that would otherwise be inaccessible. Such manipulators could be especially well suited as means of minimally invasive inspection during construction and maintenance activities. Each of the two collinear bending arm segments is further subdivided into a series of collinear extension- and compression-type helical springs joined by threaded links. The extension springs occupy the majority of the length of the arm and engage passively in bending. The compression springs are used for actively controlled bending. Bending is effected by means of pairs of antagonistic tendons in the form of spectra gel spun polymer lines that are attached at specific threaded links and run the entire length of the arm inside the spring helix from the attachment links to motor-driven pulleys inside the housing. Two pairs of tendons, mounted in orthogonal planes that intersect along the longitudinal axis, are used to effect bending of each segment. The tendons for actuating the distal bending segment are in planes offset by an angle of 45 from those of the proximal bending segment: This configuration makes it possible to
轻型钢结构吊车梁优化设计%Optimization Design of Crane Girder in Portal Frame Buildings
石永久
2001-01-01
This paper investigates the design method of crane girders applied in portal frame buildings.An optimal design approach was proposed to reduce the grider weight and fabricate the crane girder economically.Finally some design examples were given to illustrate the efficiency of the proposed method.%通过分析和研究单层门式刚架轻型钢结构厂房中的吊车梁设计，总结了轻型钢结构吊车梁的优化设计方法和节点连接构造，对合理设计吊车梁，降低用钢量提出了设计建议。
李慧萍
2011-01-01
Taking He-Yun highway box-girder fabrication project as the example,it summarizes the construction technology points for box-girder fabrication and installation engineering,respectively describes the fabrication plant layout,steel reinforcement preparation,pre-stressed tension,duct jacking and other critical construction procedures and attentions,which has provided certain guidance for future similar project.%以河运高速公路箱梁预制项目为例,针对箱梁预制及安装工程施工技术要点进行了总结,分别阐述了预制厂的布置,钢筋加工,预应力张拉,孔道压浆等关键工序施工步骤及注意事项,为今后同类项目提供了一定指导。
Dissociated Vertical Deviation
... Frequently Asked Questions Español Condiciones Chinese Conditions Dissociated Vertical Deviation En Español Read in Chinese What is Dissociated Vertical Deviation (DVD)? DVD is a condition in which ...
Tubular lining material for pipelines having bends
Moringa, A.; Sakaguchi, Y.; Hyodo, M.; Yagi, I.
1987-03-24
A tubular lining material for pipelines having bends or curved portions comprises a tubular textile jacket made of warps and wefts woven in a tubular form overlaid with a coating of a flexible synthetic resin. It is applicable onto the inner surface of a pipeline having bends or curved portions in such manner that the tubular lining material with a binder onto the inner surface thereof is inserted into the pipeline and allowed to advance within the pipeline, with or without the aid of a leading rope-like elongated element, while turning the tubular lining material inside out under fluid pressure. In this manner the tubular lining material is applied onto the inner surface of the pipeline with the binder being interposed between the pipeline and the tubular lining material. The lining material is characterized in that a part of all of the warps are comprised of an elastic yarn around which, over the full length thereof, a synthetic fiber yarn or yarns have been left-and/or right-handedly coiled. This tubular lining material is particularly suitable for lining a pipeline having an inner diameter of 25-200 mm and a plurality of bends, such as gas service pipelines or house pipelines, without occurrence of wrinkles in the lining material in a bend.
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Monitoring the Bending Stiffness of DNA
Yuan, Chongli; Lou, Xiongwen; Rhoades, Elizabeth; Chen, Huimin; Archer, Lynden
2007-03-01
In eukaryotic cells, the accessibility of genomic sequences provides an inherent regulation mechanism for gene expression through variations in bending stiffness encoded by the nucleic acid sequence. Cyclization of dsDNA is the prevailing method for determining DNA bending stiffness. Recent cyclization data for short dsDNA raises several fundamental questions about the soundness of the cyclization method, particularly in cases where the probability of highly bent DNA conformations is low. We herein evaluate the role of T4 DNA ligase in the cyclization reaction by inserting an environmental sensitive base analogue, 2-amino purine, to the DNA molecule. By monitoring the 2-AP fluorescence under standard cyclization conditions, it is found that in addition to trapping highly-bent cyclic DNA conformations, T4 DNA ligase enhances the apparent base pair flip out rate, thus exaggerating the measured flexibility. This result is further confirmed using fluorescence anisotropy experiments. We show that fluorescence resonance energy transfer (FRET) measurements on suitably labeled dsDNA provides an alternative approach for quantifying the bending stiffness of short fragments. DNA bending stiffness results obtained using FRET are compared with literature values.
Demonstration model of LEP bending magnet
CERN PhotoLab
1981-01-01
To save iron and raise the flux density, the LEP bending magnet laminations were separated by spacers and the space between the laminations was filled with concrete. This is a demonstration model, part of it with the spaced laminations only, the other part filled with concrete.
A process model for air bending
de Vin, L.J.; de Vin, L.J.; Streppel, A.H.; Singh, U.P.; Kals, H.J.J.
1996-01-01
A so called `three-section¿ model for air bending is presented. It is assumed that a state of plane strain exists and that Bernoulli's law is valid. The material behaviour is described with Swift's equation, and the change of Young's modulus under deformation is addressed. As compared with other
Design of a hydraulic bending machine
Steven G. Hankel; Marshall Begel
2004-01-01
To keep pace with customer demands while phasing out old and unserviceable test equipment, the staff of the Engineering Mechanics Laboratory (EML) at the USDA Forest Service, Forest Products Laboratory, designed and assembled a hydraulic bending test machine. The EML built this machine to test dimension lumber, nominal 2 in. thick and up to 12 in. deep, at spans up to...
Spring-back deformation in tube bending
Da-xin E; Hua-hui He; Xiao-yi Liu; Ru-xin Ning
2009-01-01
The spring-back of a bending metal tube was studied through extensive experiments and finite element method (FEM) analysis. An approximate equation for the spring-back angle of bending was deduced. It is noted that the mechanical properties of the material (in a tubular form) are quite different from those found in the standard tensile tests (when the materials are in bar forms). This is one of the major reasons that result in the discrepancies in the outcomes of experimental study, FEM calculations, and spring-back analysis. It is therefore of crucial importance to study the mechanical properties of the materials in their tubular forms. The experiments and FEM simulations prove that the spring-back angle is significantly affected by the mechanical properties of the materials. The angle decreases accordingly with plastic modulus, but changes inversely with the hardening index and elastic modulus. The spring-back angle is also affected by the conditions of tube deformation: it increases accordingly with the relative bending radius but changes inversely with the relative wall thickness. In addition, the spring-back angle increases nonlinearly with the bending an-gle.
Inelastic Deformation Analysis of Aluminum Bending Members
CHENG Ming; SHI Yongjiu; WANG Yuanqing
2006-01-01
Aluminum alloys are typical nonlinear materials, and consequently bending members made of this material exhibit a nonlinear behavior. Most design codes do not pay much attention to such deformations and adopt a simple linear analysis for the calculation of deflections. This paper presents an investigation of the nonlinear deformation of aluminum bending members using the finite-element analysis (FEA). The plastic adaptation coefficient, which can be used to limit the residual deflection, is introduced, and the influence of residual deflection is investigated. A method for evaluating the plastic adoption coefficient is proposed. This paper also shows the load-deflection curve of aluminum bending members and the influence of several parameters. A semi-empirical formula is derived, and some numerical examples are given by FEA. The coefficients of the semi-empirical formula are modified by the FEA results using the nonlinear fitting method. Based on these results, two improved design methods for strength and deformation of aluminum bending members are proposed. Through the comparison with test data, these methods are proved to be suitable for structural design.
Probing the elastic limit of DNA bending
Le, Tung T
2014-01-01
Many structures inside the cell such as nucleosomes and protein-mediated DNA loops contain sharply bent double-stranded (ds) DNA. Therefore, the energetics of strong dsDNA bending constitutes an essential part of cellular thermodynamics. Although the thermomechanical behavior of long dsDNA is well described by the worm-like chain (WLC) model, the length limit of such elastic behavior remains controversial. To investigate the energetics of strong dsDNA bending, we measured the opening rate of small dsDNA loops with contour lengths of 40-200 bp using Fluorescence Resonance Energy Transfer (FRET). From the measured relationship of loop stability to loop size, we observed a transition between two separate bending regimes at a critical loop size below 100 bp. Above this loop size, the loop lifetime decreased with decreasing loop size in a manner consistent with an elastic bending stress. Below the critical loop size, however, the loop lifetime became less sensitive to loop size, indicative of softening of the doub...
Finger-jointed beams in bending
Andreasen, Lotte; Hoffmeyer, Preben
1997-01-01
An investigation of the dynamic and static fatique of finger-jointed beams in bending was carried out. Results were obtained for five different frequencies from static loading to a load cycle period of two minutes. A total of seven series were long-term tested and five series were short-term tested...
Fuzzy model for Laser Assisted Bending Process
Giannini Oliviero
2016-01-01
Full Text Available In the present study, a fuzzy model was developed to predict the residual bending in a conventional metal bending process assisted by a high power diode laser. The study was focused on AA6082T6 aluminium thin sheets. In most dynamic sheet metal forming operations, the highly nonlinear deformation processes cause large amounts of elastic strain energy stored in the formed material. The novel hybrid forming process was thus aimed at inducing the local heating of the mechanically bent workpiece in order to decrease or eliminate the related springback phenomena. In particular, the influence on the extent of springback phenomena of laser process parameters such as source power, scan speed and starting elastic deformation of mechanically bent sheets, was experimentally assessed. Consistent trends in experimental response according to operational parameters were found. Accordingly, 3D process maps of the extent of the springback phenomena according to operational parameters were constructed. The effect of the inherent uncertainties on the predicted residual bending caused by the approximation in the model parameters was evaluated. In particular, a fuzzy-logic based approach was used to describe the model uncertainties and the transformation method was applied to propagate their effect on the residual bending.
Aerosol deposition in bends with turbulent flow
McFarland, A.R.; Gong, H.; Wente, W.B. [Texas A& M Univ., College Station, TX (United States)] [and others
1997-08-01
The losses of aerosol particles in bends were determined numerically for a broad range of design and operational conditions. Experimental data were used to check the validity of the numerical model, where the latter employs a commercially available computational fluid dynamics code for characterizing the fluid flow field and Lagrangian particle tracking technique for characterizing aerosol losses. Physical experiments have been conducted to examine the effect of curvature ratio and distortion of the cross section of bends. If it curvature ratio ({delta} = R/a) is greater than about 4, it has little effect on deposition, which is in contrast with the recommendation given in ANSI N13.1-1969 for a minimum curvature ratio of 10. Also, experimental results show that if the tube cross section is flattened by 25% or less, the flattening also has little effect on deposition. Results of numerical tests have been used to develop a correlation of aerosol penetration through a bend as a function of Stokes number (Stk), curvature ratio ({delta}) and the bend angle ({theta}). 17 refs., 10 figs., 2 tabs.
Head movements while steering around bends
Erp, J.B.F. van; Oving, A.B.
2012-01-01
In this study, the determinants of head motions (rotations) when driving around bends were investigated when drivers viewed the scene through a head-mounted display. The scene camera was either fixed or coupled to head motions along 2 or 3 axes of rotation. Eight participants drove around a
Byungik Chang
2012-01-01
Full Text Available With the Federal Highway Administration-mandated implementation of the LRFD specifications, many state departments of transportation (DOTs have already started implementing LRFD specifications as developed by the AASHTO. Many aspects of the LRFD specifications are being investigated by DOTs and researchers in order for seamless implementation for design and analysis purposes. This paper presents the investigation on several design aspects of post-tensioned box girder bridges designed by LRFD Specifications using conventional or High-Strength Concrete (HSC. A computer spreadsheet application was specifically developed for this investigation. It is capable of analysis, design, and cost evaluation of the superstructure for a cast-in-place post-tensioned box girder bridge. Optimal design of a post-tensioned box girder is achievable by correct selection of design variables. Cost evaluation of superstructures with different geometrical and material configurations has led to the development of optimum design charts for these types of superstructures. Variables used to develop these charts include, among others, span length, section depth, web spacing, tendon profile, and concrete strength. It was observed that HSC enables the achievement of significantly longer span lengths and/or longer web spacing that is not achievable when using normal strength concrete.
矿用汽车车架纵梁成形模开发研究%Mine Car Frame Girder Mold Development Research
向小汉
2013-01-01
To mine car frame girder for forming process analysis, with AutoForm software rebound calculation, the results of the analysis according to the rebound in ThinkDesign to girder local for the springback compensation, in the mold structure design also takes into account to springback control. Through the forming process of the optimization and reasonable die structure design, got to meet quality requirements of the girder products, and meet the needs of the mass production.%对矿用汽车车架纵梁进行成形工艺分析，用AutoForm软件进行回弹计算，根据回弹分析结果用ThinkDesign对纵梁局部进行回弹补偿，在模具结构设计中也考虑到对回弹的控制。通过成形工艺的优化和合理的模具结构设计，得到了满足质量要求的纵梁产品，并满足了批量生产的需要。
Experimental Characterization of Stretch-Bending Formability of AHSS Sheets
Kitting, Daniela; Ofenheimer, Aldo; Pauli, Heinrich; Till, Edwin T.
2011-05-01
Deformation conditions of combined stretching and bending are known to enhance material formability compared to forming conditions without bending (e.g. in-plane stretching). These phenomena can be observed for most conventional steel grades but is even more pronounced for Advanced High Strength Steel (AHSS) sheets. Consequently, there is an urgent need in industry to quantify the phenomena of enhanced material formability due to bending effects. In this work new stretch-bend test setups are presented which can be used in addition to the conventional Angular Stretch Bend Test to systematically investigate the influence of various stretch-bending deformation conditions on the formability of AHSS sheets.
Bending effects on lasing action of semiconductor nanowires.
Yang, Weisong; Ma, Yaoguang; Wang, Yipei; Meng, Chao; Wu, Xiaoqin; Ye, Yu; Dai, Lun; Tong, Limin; Liu, Xu; Yang, Qing
2013-01-28
High flexibility has been one of advantages for one-dimensional semiconductor nanowires (NWs) in wide application of nanoscale integrated circuits. We investigate the bending effects on lasing action of CdSe NWs. Threshold increases and differential efficiency decreases gradually when we decrease the bending radius step by step. Red shift and mode reduction in the output spectra are also observed. The bending loss of laser oscillation is considerably larger than that of photoluminescence (PL), and both show the exponential relationship with the bending radius. Diameter and mode dependent bending losses are investigated. Furthermore, the polarizations of output can be modulated linearly by bending the NWs into different angles continuously.
Vertical bounce of two vertically aligned balls
Cross, Rod
2007-11-01
When a tennis ball rests on top of a basketball and both drop to the floor together, the tennis ball is projected vertically at high speed. A mass-spring model of the impact, as well as air track data, suggest that the tennis ball should be projected at relatively low speed. Measurements of the forces on each ball and the bounce of vertically aligned superballs are used to resolve the discrepancy.
Narayanaswami, R.
1973-01-01
A new higher order triangular plate-bending finite element is presented which possesses high accuracy for practical mesh subdivisions and which uses only translations and rotations as grid point degrees of freedom. The element has 18 degrees of freedom, the transverse displacement and two rotations at the vertices and mid-side grid points of the triangle. The transverse displacement within the element is approximated by a quintic polynomial; the bending strains thus vary cubically within the element. Transverse shear flexibility is taken into account in the stiffness formulation. Two examples of static and dynamic analysis are included to show the behavior of the element.
Krivcov, Vladimir [Miass, RU; Krivospitski, Vladimir [Miass, RU; Maksimov, Vasili [Miass, RU; Halstead, Richard [Rohnert Park, CA; Grahov, Jurij [Miass, RU
2011-03-08
A vertical axis wind turbine is described. The wind turbine can include a top ring, a middle ring and a lower ring, wherein a plurality of vertical airfoils are disposed between the rings. For example, three vertical airfoils can be attached between the upper ring and the middle ring. In addition, three more vertical airfoils can be attached between the lower ring and the middle ring. When wind contacts the vertically arranged airfoils the rings begin to spin. By connecting the rings to a center pole which spins an alternator, electricity can be generated from wind.
Observation of free surface-induced bending upon nanopatterning of ultrathin strained silicon layer
Moutanabbir, Oussama; Reiche, Manfred; Zakharov, Nikolai [Max Planck Institute of Microstructure Physics, Weinberg 2, Halle (Saale), 06120 (Germany); Naumann, Falk; Petzold, Matthias, E-mail: moutanab@mpi-halle.mpg.de [Fraunhofer Institute for Mechanics of Materials, Walter-Huelse-Strasse 1, Halle (Saale), 06120 (Germany)
2011-01-28
We provide evidence of nanopatterning-induced bending of an ultrathin tensile strained silicon layer directly on oxide. This strained layer is achieved through the epitaxial growth of silicon on a Si{sub 0.84}Ge{sub 0.16} virtual substrate and subsequent transfer onto a SiO{sub 2}-capped silicon substrate by combining hydrophilic wafer bonding and the ion-cut process. Using high resolution transmission electron microscopy, we found that the upper face of the strained silicon nanostructures fabricated from the obtained heterostructure using electron beam lithography and dry reactive ion etching displays a concave shape. This bending results from the free-surface-induced strain relaxation, which implies lattice out-of-plane expansion near the edges and concomitant contraction at the center. For a {approx} 110 nm x 400 nm x 20 nm nanostructure, the bending is associated with an angle of 1.5 deg. between the (22-bar) vertical atomic planes at the edges of the {approx} 110 nm side. No bending is, however, observed at the strained Si/SiO{sub 2} interface. This phenomenon cannot be explained by the classical Stoney's formula or related formulations developed for nanoscale thin films. Here we employed a continuum mechanical approach to describe these observations using three-dimensional numerical calculations of relaxation-induced lattice displacements.
Worobets, Jay; Wannop, John William
2015-09-01
Prior research has shown that footwear can enhance athletic performance. However, public information is not available on what basketball shoe properties should be selected to maximise movement performance. Therefore, the purpose of the study was to investigate the influence of basketball shoe mass, outsole traction, and forefoot bending stiffness on sprinting, jumping, and cutting performance. Each of these three basketball shoe properties was systematically varied by ± 20% to produce three shoe conditions of varying mass, three conditions of varying traction, and three conditions of varying bending stiffness. Each shoe was tested by 20 recreational basketball players completing maximal effort sprints, vertical jumps, and a cutting drill. Outsole traction had the largest influence on performance, as the participants performed significantly worse in all tests when traction was decreased by 20% (p < 0.001), and performed significantly better in the cutting drill when traction was increased by 20% (p = 0.005). Forefoot bending stiffness had a moderate effect on sprint and cutting performance (p = 0.013 and p = 0.016 respectively) and shoe mass was found to have no effect on performance. Therefore, choosing a shoe with relatively high outsole traction and forefoot bending stiffness should be prioritised, and less concern should be focused on selecting the lightest shoe.
The development of studying flexible pipe bend reinforced by Kevlar fibers
SHUAI Chang-geng; HE Lin; LU Zhi-qiang
2003-01-01
The flexible pipe bend can not only reduce the structural vibration and fluid noise in pipeline, but also realize the flexible connection of a horizontal line and a vertical line and compensate the displacement of three dimensions produced by the shock or vibration of pipeline in the special situations. Up to now, little attention has been paid to study the flexible pipe bend applied in the pipeline of medium or high pressure, because no appropriate framework materials can be used to reinforce it which must endure the burst pressure higher than 10 MPa. The investigation shows that it is possible to produce the flexible pipe bend of medium or high pressure if such fibers with high performance as Kevlar fibers are used to be its reinforced materials. However, its structural designing theory, manufacturing technology and measuring techniques aren't yet perfect and systematic, which leads to the instability of the performance of products. Furthermore, few references about its research can be seen. Therefore, it is necessary to systematically and thoroughly develop the structural designing theory, manufacture technology and measuring techniques of flexible pipe bend.
The Dependency of Nematic and Twist-bend Mesophase Formation on Bend Angle
Mandle, Richard J.; Archbold, Craig T.; Sarju, Julia P.; Andrews, Jessica L.; Goodby, John W.
2016-11-01
We have prepared and studied a family of cyanobiphenyl dimers with varying linking groups with a view to exploring how molecular structure dictates the stability of the nematic and twist-bend nematic mesophases. Using molecular modelling and 1D 1H NOESY NMR spectroscopy, we determine the angle between the two aromatic core units for each dimer and find a strong dependency of the stability of both the nematic and twist-bend mesophases upon this angle, thereby satisfying earlier theoretical models.
刘林芽; 付奇川; 邵文杰; 李纪阳
2015-01-01
Taking the high speed railway 32 m concrete simply -supported box bridge as the research object,the theses used finite element software to set up for high speed railway track -bridge analysis model.Then,based on the theory of vehicle -track -bridge coupling vibration,this paper analyzed the vertical vibration of the struc-ture of the bridge.A vertical vibration response was finally gotten as boundary conditions,which we use in the boundary element model of box girder structure noise prediction.At the same time,based on panel acoustic con-tribution analysis theory,the box beam body panel pressure contribution analysis and panel acoustic power analy-sis were done.In this way,we determined the largest position of body radiation noise for box beam .The results of the study show that if the train speeds up to 200 km /h on the elevated rail,box beam body radiation noise mainly occur within the range of 0 -100 Hz,of which 20 Hz and 42 Hz are prominent peak.Meanwhile,by the panel acoustic contribution analysis,we come to the conclusion that the part of main radiation noise comes from the box girder roof and the two flank flange panel.%以高速铁路32 m 混凝土简支箱型桥梁为研究对象，通过有限元软件建立了轨道－桥梁分析模型，采用车辆－轨道－桥梁耦合振动理论，分析了桥梁结构的竖向振动，并将得到的竖向振动响应作为边界条件，导入到箱梁边界元模型中预测箱梁结构噪声。同时基于面板声学贡献分析理论，进行了箱梁梁体的面板声压贡献分析和声功率贡献分析，确定箱梁梁体辐射噪声的最大部位。研究结果表明：列车以200 km／h 的速度运行在高架轨道上时，箱梁梁体辐射噪声主要集中0－100 Hz 范围内，其中在20 Hz 和42 Hz 左右有比较突出峰值。同时由面板声学贡献分析可知箱梁梁体主要辐射噪声的部位是箱梁的顶板和两侧翼缘板下面板。
Oide Effect and Radiation in Bending Magnets
Blanco, Oscar; Bambade, Philip
2014-01-01
Including radiation effects during lattice design optimization is crucial in high energy accelerators. Oide effect and radiation in bending magnets are reviewed aiming to include them in the optical design process to minimize the IP beam size. The Oide double integral is expressed in simpler terms in order to speed up calculations, concluding in how longer quadrupoles with lower gradients may help reducing the Oide effect. Radiation in bending magnets is reviewed for linear lattices, generalizing to the case when the final dispersion is different from zero and making comparisons with theoretical results and particle tracking. An agreement between the theory, the implemented approximation included in MAPCLASS2 and the six-dimensional tracking in PLACET has been found.
Vortex breakdown in simple pipe bends
Ault, Jesse; Shin, Sangwoo; Stone, Howard
2016-11-01
Pipe bends and elbows are one of the most common fluid mechanics elements that exists. However, despite their ubiquity and the extensive amount of research related to these common, simple geometries, unexpected complexities still remain. We show that for a range of geometries and flow conditions, these simple flows experience unexpected fluid dynamical bifurcations resembling the bubble-type vortex breakdown phenomenon. Specifically, we show with simulations and experiments that recirculation zones develop within the bends under certain conditions. As a consequence, fluid and particles can remain trapped within these structures for unexpectedly-long time scales. We also present simple techniques to mitigate this recirculation effect which can potentially have impact across industries ranging from biomedical and chemical processing to food and health sciences.
Rock bending creep and disturbance effects
付志亮; 郑颖人; 刘元雪
2008-01-01
The bending creep and its disturbance effects of red sandstone rock beam and oil shale rock beam were studied by adopting the self-developed gravitation level style rock creep test machine and bending creep test system,and the constitutive equations were established.It is found that fracture morphology of rock beams under no disturbance load is regular,cracking position of fractures is on part of loading concentration,the crack starts from a neutral plane.However,fracture morphology of rock beams under disturbance load is irregular,cracking position of fractures deviates from a neutral plane.Delayed instability of rock beam occurs for some time under constant disturbance load.When disturbance load is beyond a certain range,suddenly instability of occurs rock beam in a certain time.The results show that there is a guiding significance for creep stability in the geotechnical engineering fields.
Ultrasonic fatigue testing device under biaxial bending
C. Brugger
2016-07-01
Full Text Available A new fatigue testing device has been developed to test specimens under biaxial loading at 20 kHz. A flat smooth specimen with a disc geometry is placed on a torus frame and cyclically loaded at the center of its upper face. Disc bending generates a biaxial proportional stress state at the center of the lower face. Any positive loading ratio can be applied. A cast aluminum alloy (used to produce cylinder heads has been tested under biaxial bending using this device in order to determine its fatigue strength at 109 cycles under high hydrostatic pressure. Self-heating is moderate but macroscopic fatigue cracks after testing are very long. First results in VHCF regime are consistent with literature results obtained under similar stress state but in HCF regime and at 20 Hz.
Thermal Analysis of Bending Under Tension Test
Ceron, Ermanno; Martins, Paulo A.F.; Bay, Niels
2014-01-01
The tribological conditions in deep drawing can be simulated in the Bending Under Tension test to evaluate the performance of new lubricants, tool materials, etc. Deep drawing production with automatic handling runs normally at high rate. This implies considerable heating of the tools, which...... sometimes can cause lubricant film breakdown and galling. In order to replicate the production conditions in bending under tension testing it is thus important to control the tool/workpiece interface temperature. This can be done by pre-heating the tool, but it is essential that the interface temperature...... during testing is similar to the one in the production tool. A universal sheet tribo-tester has been developed, which can run multiple tests automatically from coil. This allows emulating the temperature increase as in production. The present work performs finite element analysis of the evolution...
Parallel monostrand stay cable bending fatigue
Winkler, Jan Pawel
of damage and replacement of bridge stay cables due to wind and traffic-induced fatigue. The understanding of fatigue mechanisms in most steel structures is well established. However, in the case of cables composed of steel strands, many important aspects related with bending fatigue remain to be clarified......This dissertation investigates the bending fatigue response of high-strength steel monostrands and multistrand stay cables to cyclic transverse deformations. Increasing bridge stock numbers and a push for longer cable-supported span lengths have led to an increased number of reported incidents...... associated with variable loading, and different testing procedures. As most of the contemporary stay cables are comprised of a number of individual highstrength steel monostrands, the research study started with an extensive experimental work on the fatigue response of a single monostrand to cyclic flexural...
Approach to hot bending process simulation
Carmignani, B.; Daneri, A.; Toselli, G. [ENEA, Bologna (Italy). Centro Ricerche Energia `E. Clementel` - Area Energia e Innovazione
1995-06-01
An approach to the simulation of the thermal shaping or bending of large steel sheets, by ABAQUS/Standard code, will be presented. A thermal source representation, which can produce a temperature distribution, adequate to the processes which must be considered, has been set up. Some problems connected with the hot sheet shaping or bending process simulation have been approached and calculations have been executed in order to single out how to perform the sheet heating, so that the required sheet shape may be obtained. The results for one reference model for different source situations and one heating line, object of the first phase of the analyses performed, will be presented and discussed. The work will be presented at the 8th International Abaqus Users` Conference at Paris, 31 May - 2 June 1995.
Holey fibers for low bend loss
Nakajima, Kazuhide; Saito, Kotaro; Yamada, Yusuke; Kurokawa, Kenji; Shimizu, Tomoya; Fukai, Chisato; Matsui, Takashi
2013-12-01
Bending-loss insensitive fiber (BIF) has proved an essential medium for constructing the current fiber to the home (FTTH) network. By contrast, the progress that has been made on holey fiber (HF) technologies provides us with novel possibilities including non-telecom applications. In this paper, we review recent progress on hole-assisted type BIF. A simple design consideration is overviewed. We then describe some of the properties of HAF including its mechanical reliability. Finally, we introduce some applications of HAF including to high power transmission. We show that HAF with a low bending loss has the potential for use in various future optical technologies as well as in the optical communication network.
罗扣; 王东晖; 张强
2013-01-01
The main part of the Hong Kong-Zhuhai-Macau Bridge is a part of the combined bridge and tunnel,of which the non-navigable span bridge in the shallow water area is the 85 m span continuous composite girder bridge that totally has 64 spans of the composite girders and is 5 440 m in length.The span arrangement of the bridge mainly includes two kinds of arrangement of 6)× 85 m and 5)× 85 m.The composite girders are the separated continuous single-cell singlebox girders with constant depth and specifically are composed of the open steel box girders and the concrete deck slabs that are connected each other via shear studs.A steel box girder is the inverted trapezoid structure,a concrete deck slab is the precast full slab in the transverse direction and the grooves are pre-reserved at the locations of the shear studs.To improve the transverse mechanical behavior of the deck slabs,the stringers are set in the sections of the composite girders and to keep the integrity of the slabs,the shear studs are arranged in a way of clustering.The composite girders are erected and installed in each full span by the large transportation and erection floating crane and the girders are closed span by span.%港珠澳大桥主体工程采用桥隧组合方案,其中浅水区非通航孔桥采用85 m连续组合梁桥形式,全长5 440m,共64孔,跨径布置主要采用6×85 m和5×85m2种形式.组合梁采用单箱单室分幅等高连续梁,由开口钢箱梁和混凝土桥面板通过剪力钉联结而成.钢箱梁为倒梯形结构;混凝土桥面板为横向整块预制,在剪力钉处设置预留槽.为改善混凝土桥面板的横向受力性能,该桥组合梁截面设置小纵梁;为保持桥面板的整体性,剪力钉采用集束式布置方式.组合梁采用大型运架一体浮吊整孔安装架设,逐孔合龙.
Cyclic stretch-bending: mechanics, stability and formability
Emmens, W.C.; van den Boogaard, Antonius H.
2011-01-01
Cyclic stretch-bending has been studied using the so-called Continuous-Bending-under-Tension (CBT) test. This is a modified tensile test where the specimen is subjected to repetitive bending at the same time. A wide variety of materials have been tested this way. A simple mechanical model is
Short Range Wake Field Caused by Electron Cloud in Bending Magnet
Wang, L; Zimmermann, Frank; Ohmi, K
2001-01-01
A short-range wake field caused by the electron cloud has previously been studied for a drift space. In a bending magnet, the cloud electrons undergo cyclotron motion with a small radius (10 GHz) in the horizontal plane due to the strong magnetic field of order 1 T. In this report, we study the motion of electrons under the combined influence of a strong magnetic dipole field and the electric field of the beam on the time scale of the bunch length, discuss the short-range wake field caused by the electrons, and simulate the emittance growth. As expected, the wake field in a bending magnet is very different from that in a drift space. The dipole field almost completely suppresses any horizontal coherent motion and rms-size blow up, and it also slows down the instability in the vertical direction.
Cury, Alexandre; Cremona, Christian; Dumoulin, John
2012-11-01
For reliable performance of vibration-based damage detection algorithms, it is important to distinguish abnormal changes in modal parameters caused by structural damage from normal changes due to environmental fluctuations. This paper firstly addresses the modeling of temperature effects on modal frequencies of a PSC box girder bridge located on the A1 motorway in France. Based on a six-month monitoring experimental program, modal frequencies of the first seven mode shapes and temperatures have been measured at three hour intervals. Neural networks are then introduced to formulate regression models for quantifying the effect of temperature on modal parameters (frequencies and mode shapes). In 2009, this bridge underwent a strengthening procedure. In order to assess the effect of strengthening on the vibration characteristics of the bridge, modal properties had to be corrected from temperature influence. Thus, the first goal is to assess the changes on the vibration signature of this bridge induced by the strengthening. For this purpose, classical statistical analysis and clustering methods are applied to the data recorded over the period after strengthening. The second goal is to evaluate the influence of temperature effects on the clustering results. It comes that the temperature correction significantly improves the confidence in the novelty detection and in the strengthening efficiency.
Yang, Caiqian; Wu, Zhishen; Zhang, Yufeng
2008-06-01
The application of hybrid carbon fiber reinforced polymer (HCFRP) sensors was addressed to monitor the structural health of an existing prestressed concrete (PC) box girder bridge in a destructive test. The novel HCFRP sensors were fabricated with three types of carbon tows in order to realize distributed and broad-based sensing, which is characterized by long-gauge length and low cost. The HCFRP sensors were bonded on the bottom and side surfaces of the existing bridge to monitor its structural health. The gauge lengths of the sensors bonded on the bottom and side surfaces were 1.5 m and 1.0 m, respectively. The HCFRP sensors were distributed on the bridge for two purposes. One was to detect damage and monitor the structural health of the bridge, such as the initiation and propagation of new cracks, strain distribution and yielding of steel reinforcements. The other purpose was to monitor the propagation of existing cracks. The good relationship between the change in electrical resistance and load indicates that the HCFRP sensors can provide actual infrastructures with a distributed damage detection and structural health monitoring system. Corrections were made to this article on 13 May 2008. The corrected electronic version is identical to the print version.
Wu, Jie; Yan, Quan-sheng; Li, Jian; Hu, Min-yi
2016-04-01
In bridge construction, geometry control is critical to ensure that the final constructed bridge has the consistent shape as design. A common method is by predicting the deflections of the bridge during each construction phase through the associated finite element models. Therefore, the cambers of the bridge during different construction phases can be determined beforehand. These finite element models are mostly based on the design drawings and nominal material properties. However, the accuracy of these bridge models can be large due to significant uncertainties of the actual properties of the materials used in construction. Therefore, the predicted cambers may not be accurate to ensure agreement of bridge geometry with design, especially for long-span bridges. In this paper, an improved geometry control method is described, which incorporates finite element (FE) model updating during the construction process based on measured bridge deflections. A method based on the Kriging model and Latin hypercube sampling is proposed to perform the FE model updating due to its simplicity and efficiency. The proposed method has been applied to a long-span continuous girder concrete bridge during its construction. Results show that the method is effective in reducing construction error and ensuring the accuracy of the geometry of the final constructed bridge.
Wooden Model of Wide AA Bending Magnet
1978-01-01
The very particular lattice of the AA required 2 types of dipoles (bending magnets: BLG, long and narrow; BST, short and wide). The wide ones had a steel length of 2.71 m, a "good field" width of 0.564 m, and a weight of about 75 t. Here we see a wooden model, built in 1978, to gain dimensional experience with such a monster.
Electron cooling device without bending magnets
Sharapa, A. N.; Shemyakin, A. V.
1993-11-01
The scheme of an axisymmetric electron cooling device without bending magnets is proposed. Solutions for the most important elements, i.e., a gun and a recuperator, are considered. The main characteristics of the recuperator of the Faraday cup type having a reflector and a gun with a ring emitter are explored. In the gun, the beam is formed, the diameter of which is 40 mm and the dimension of a disturbance region is several millimeters.
AA, assembly of wide bending magnet
1980-01-01
The very particular lattice of the AA required 2 types of dipoles (bending magnets; BST, short and wide; BLG, long and narrow). The wide ones had a steel length of 2.71 m, a "good field" width of 0.564 m, and a weight of about 75 t. Here we see the copper coils being hoisted onto the lower half of a BST. See also 7811105, 8006050. For a BLG, see 8001044.
Drag Reduction, from Bending to Pruning
Lopez, Diego; Michelin, Sébastien; de Langre, Emmanuel
2013-01-01
Most plants and benthic organisms have evolved efficient reconfiguration mechanisms to resist flow-induced loads. These mechanisms can be divided into bending, in which plants reduce their sail area through elastic deformation, and pruning, in which the loads are decreased through partial breakage of the structure. In this work, we show by using idealized models that these two mechanisms or, in fact, any combination of the two, are equally efficient to reduce the drag experienced by terrestrial and aquatic vegetation.
Big Bend National Park, TX, USA, Mexico
1991-01-01
The Sierra del Carmen of Mexico, across the Rio Grande River from Big Bend National Park, TX, (28.5N, 104.0W) is centered in this photo. The Rio Grande River bisects the scene; Mexico to the east, USA to the west. The thousand ft. Boquillas limestone cliff on the Mexican side of the river changes colors from white to pink to lavender at sunset. This severely eroded sedimentary landscape was once an ancient seabed later overlaid with volcanic activity.
Signatures of Currency Vertices
Holme, Petter
2009-03-01
Many real-world networks have broad degree distributions. For some systems, this means that the functional significance of the vertices is also broadly distributed, in other cases the vertices are equally significant, but in different ways. One example of the latter case is metabolic networks, where the high-degree vertices — the currency metabolites — supply the molecular groups to the low-degree metabolites, and the latter are responsible for the higher-order biological function, of vital importance to the organism. In this paper, we propose a generalization of currency metabolites to currency vertices. We investigate the network structural characteristics of such systems, both in model networks and in some empirical systems. In addition to metabolic networks, we find that a network of music collaborations and a network of e-mail exchange could be described by a division of the vertices into currency vertices and others.
Multiculturalism, Gender and Bend it Like Beckham
Gamal Abdel-Shehid
2015-06-01
Full Text Available In this article, we explore the efficacy of sport as an instrument for social inclusion through an analysis of the film Bend it Like Beckham. The film argues for the potential of sport to foster a more inclusive society in terms of multiculturalism and gender equity by showing how a hybrid culture can be forged through the microcosm of an English young women’s football club, while simultaneously challenging assumptions about traditional masculinities and femininities. Yet, despite appearances, Bend it Like Beckham does little to challenge the structure of English society. Ultimately, the version of multiculturalism offered by the film is one of assimilation to a utopian English norm. This conception appears progressive in its availability to all Britons regardless of ethnicity, but falls short of conceptions of hybrid identity that do not privilege one hegemonic culture over others. Likewise, although the film presents a feminist veneer, underneath lurks a troubling reassertion of the value of chastity, masculinity, and patriarchy. Bend it Like Beckham thus provides an instructive case study for the potential of sport as a site of social inclusion because it reveals how seductive it is to imagine that structural inequalities can be overcome through involvement in teams.
SYMPLECTIC SOLUTION SYSTEM FOR REISSNER PLATE BENDING
姚伟岸; 隋永枫
2004-01-01
Based on the Hellinger-Reissner variatonal principle for Reissner plate bending and introducing dual variables, Hamiltonian dual equations for Reissner plate bending were presented. Therefore Hamiltonian solution system can also be applied to Reissner plate bending problem, and the transformation from Euclidian space to symplectic space and from Lagrangian system to Hamiltonian system was realized. So in the symplectic space which consists of the original variables and their dual variables, the problem can be solved via effective mathematical physics methods such as the method of separation of variables and eigenfunction-vector expansion. All the eigensolutions and Jordan canonical form eigensolutions for zero eigenvalue of the Hamiltonian operator matrix are solved in detail,and their physical meanings are showed clearly. The adjoint symplectic orthonormal relation of the eigenfunction vectors for zero eigenvalue are formed. It is showed that the all eigensolutions for zero eigenvalue are basic solutions of the Saint-Venant problem and they form a perfect symplectic subspace for zero eigenvalue. And the eigensolutions for nonzero eigenvalue are covered by the Saint-Venant theorem. The symplectic solution method is not the same as the classical semi- inverse method and breaks through the limit of the traditional semi-inverse solution. The symplectic solution method will have vast application.
Space, composition, vertical wall ...
Despot, Katerina; Sandeva, Vaska
2016-01-01
The space in which it is an integral segment of our life is nourished with many functional and decorative elements. One aspect for consideration of vertical walls or The vertical gardens and their aesthetic impact in space called function. Vertical gardens bordering the decoration to totally functional garden in areas where there is little oxygen and space, ideal for residential buildings and public spaces where missing greenery, special place occupies in interior design where their expres...
2012-06-15
... COMMISSION PPL Bell Bend, LLC; Bell Bend Nuclear Power Plant Combined License Application; Notice of Intent... its Bell Bend Nuclear Power Plant (BBNPP) site, located west of the existing Susquehanna Steam... by relocating the power block footprint and other plant components. For purposes of developing...
2013-01-22
... COMMISSION PPL Bell Bend, LLC; Combined License Application for Bell Bend Nuclear Power Plant; Exemption 1.0... Approvals for Nuclear Power Plants.'' This reactor is to be identified as Bell Bend Nuclear Power Plant... (RCOL) application for UniStar's Calvert Cliffs Nuclear Power Plant, Unit 3 (CCNPP3). The......
2011-12-29
... COMMISSION PPL Bell Bend, LLC; Combined License Application for Bell Bend Nuclear Power Plant; Exemption 1.0..., Certifications, and Approvals for Nuclear Power Plants.'' This reactor is to be identified as Bell Bend Nuclear Power Plant (BBNPP), in Salem County, Pennsylvania. The BBNPP COL application incorporates by...
Tunable waveguide bends with graphene-based anisotropic metamaterials
Chen, Zhao-xian
2016-01-15
We design tunable waveguide bends filled with graphene-based anisotropic metamaterials to achieve a nearly perfect bending effect. The anisotropic properties of the metamaterials can be described by the effective medium theory. The nearly perfect bending effect is demonstrated by finite element simulations of various structures with different bending curvatures and shapes. This effect is attributed to zero effective permittivity along the direction of propagation and matched effective impedance at the interfaces between the bending part and the dielectric waveguides. We envisage that the design will be applicable in the far-infrared and terahertz frequency ranges owing to the tunable dielectric responses of graphene.
Permanent bending and alignment of ZnO nanowires.
Borschel, Christian; Spindler, Susann; Lerose, Damiana; Bochmann, Arne; Christiansen, Silke H; Nietzsche, Sandor; Oertel, Michael; Ronning, Carsten
2011-05-06
Ion beams can be used to permanently bend and re-align nanowires after growth. We have irradiated ZnO nanowires with energetic ions, achieving bending and alignment in different directions. Not only the bending of single nanowires is studied in detail, but also the simultaneous alignment of large ensembles of ZnO nanowires. Computer simulations reveal how the bending is initiated by ion beam induced damage. Detailed structural characterization identifies dislocations to relax stresses and make the bending and alignment permanent, even surviving annealing procedures.
Permanent bending and alignment of ZnO nanowires
Borschel, Christian; Spindler, Susann; Oertel, Michael; Ronning, Carsten [Institut fuer Festkoerperphysik, Friedrich-Schiller-Universitaet Jena, Max-Wien-Platz 1, 07743 Jena (Germany); Lerose, Damiana [MPI fuer Mikrostrukturphysik, Weinberg 2, 06120 Halle/Saale (Germany); Institut fuer Photonische Technologien, Albert-Einstein-Strasse 9, 07745 Jena (Germany); Bochmann, Arne [Institut fuer Photonische Technologien, Albert-Einstein-Strasse 9, 07745 Jena (Germany); Christiansen, Silke H. [Institut fuer Photonische Technologien, Albert-Einstein-Strasse 9, 07745 Jena (Germany); MPI fuer die Physik des Lichts, Guenther-Scharowsky-Str. 1, 91058 Erlangen (Germany); Nietzsche, Sandor [Zentrum fuer Elektronenmikroskopie, Friedrich-Schiller-Universitaet Jena, Ziegelmuehlenweg 1, 07743 Jena (Germany)
2011-07-01
Ion beams can be used to bend or re-align nanowires permanently, after they have been grown. We have irradiated ZnO nanowires with ions of different species and energy, achieving bending and alignment in various directions. We study the bending of single nanowires as well as the simultaneous alignment of large ensembles of ZnO nanowires in detail. Computer simulations show that the bending is initiated by ion beam induced damage. Dislocations are identified to relax stresses and make the bending and alignment permanent and resistant against annealing procedures.
Tunable waveguide bends with graphene-based anisotropic metamaterials
Chen, Zhao-xian; Chen, Ze-guo; Ming, Yang; Wu, Ying; Lu, Yan-qing
2016-02-01
We design tunable waveguide bends filled with graphene-based anisotropic metamaterials to achieve a nearly perfect bending effect. The anisotropic properties of the metamaterials can be described by the effective medium theory. The nearly perfect bending effect is demonstrated by finite element simulations of various structures with different bending curvatures and shapes. This effect is attributed to zero effective permittivity along the direction of propagation and matched effective impedance at the interfaces between the bending part and the dielectric waveguides. We envisage that the design will be applicable in the far-infrared and terahertz frequency ranges owing to the tunable dielectric responses of graphene.
Parameter prediction in laser bending of aluminum alloy sheet
Xuyue WANG; Weixing XU; Hua CHEN; Jinsong WANG
2008-01-01
Based on the basic platform of BP neural net-works, a BP network model is established to predict the bending angle in the laser bending process of an aluminum alloy sheet (1-2 mm in thickness) and to optimize laser bending parameters for bending control. The sample experimental data is used to train the BP network. The nonlinear regularities of sample data are fitted through the trained BP network; the predicted results include laser bending angles and parameters. Experimental results indi-cate that the prediction allowance is controlled less than 5%-8% and can provide a theoretical and experimental basis for industry purpose.
Recent developments in bend-insensitive and ultra-bend-insensitive fibers
Boivin, David; de Montmorillon, Louis-Anne; Provost, Lionel; Montaigne, Nelly; Gooijer, Frans; Aldea, Eugen; Jensma, Jaap; Sillard, Pierre
2010-02-01
Designed to overcome the limitations in case of extreme bending conditions, Bend- and Ultra-Bend-Insensitive Fibers (BIFs and UBIFs) appear as ideal solutions for use in FTTH networks and in components, pigtails or patch-cords for ever demanding applications such as military or sensing. Recently, however, questions have been raised concerning the Multi-Path-Interference (MPI) levels in these fibers. Indeed, they are potentially subject to interferences between the fundamental mode and the higher-order mode that is also bend resistant. This MPI is generated because of discrete discontinuities such as staples, bends and splices/connections that occur on distance scales that become comparable to the laser coherent length. In this paper, we will demonstrate the high MPI tolerance of all-solid single-trench-assisted BIFs and UBIFs. We will present the first comprehensive study combining theoretical and experimental points of view to quantify the impact of fusion splices on coherent MPI. To be complete, results for mechanical splices will also be reported. Finally, we will show how the single-trench- assisted concept combined with the versatile PCVD process allows to tightly control the distributions of fibers characteristics. Such controls are needed to massively produce BIFs and to meet the more stringent specifications of the UBIFs.
B. Scherllin-Pirscher
2014-08-01
Full Text Available In this paper, we introduce a bending angle radio occultation climatology (BAROCLIM based on Formosat-3/COSMIC (F3C data. This climatology represents the monthly-mean atmospheric state from 2006 to 2012. Bending angles from radio occultation (RO measurements are obtained from the accumulation of the change in the raypath direction of Global Positioning System (GPS signals. Best quality of these near-vertical profiles is found from the middle troposphere up to the mesosphere. Beside RO bending angles we also use data from the Mass Spectrometer and Incoherent Scatter Radar (MSIS model to expand BAROCLIM in a spectral model, which (theoretically reaches from the surface up to infinity. Due to the very high quality of BAROCLIM up to the mesosphere, it can be used to detect deficiencies in current state-of-the-art analysis and reanalysis products from numerical weather prediction (NWP centers. For bending angles derived from European Centre for Medium-Range Weather Forecasts (ECMWF analysis fields from 2006 to 2012, e.g., we find a positive bias of 0.5% to % at 40 km, which increases to more than 2% at 50 km. BAROCLIM can also be used as a priori information in RO profile retrievals. In contrast to other a priori information (i.e., MSIS we find that the use of BAROCLIM better preserves the mean of raw RO measurements. Global statistics of statistically optimized bending angle and refractivity profiles also confirm that BAROCLIM outperforms MSIS. These results clearly demonstrate the utility of BAROCLIM.
Representation of horizontal strain due to tidal bending by observation and modeling
Rack, Wolfgang; King, Matt; Marsh, Oliver; Wild, Christian; Floricioiu, Dana
2017-04-01
An important control of ice sheet mass balance is the ice dynamics in the grounding zones around Antarctica. On many outflow glaciers a large temporal variability in ice flow has been observed, which is at least partly related to tides. Here we investigate the tide induced short term ice deformation in an ice shelf grounding zone and the related bending stresses and strain. We make use of the arguably most precise measurement method, differential SAR interferometry, in combination with ground based measurements and model assumptions for tidal bending. Ground validation and satellite data have been acquired within a dedicated field campaign. The Southern McMurdo Ice Shelf in the Western Ross Ice Shelf region was chosen as the experiment site. This area is optimal for the data interpretation because of a simple grounding line configuration, small ice flux, and favourable satellite imaging geometry. It is also a safe area which allowed the installation of tiltmeters and GPS stations, and glaciological measurements such as ice thickness and snow accumulation. From November 2014 to January 2015 the tidal movement was recorded over a period of 2.5 months. TerrSAR-X radar images have been acquired over the same period as a basis to derive ice shelf flexure maps. Despite the viscoelastic effects in ice shelf bending a simple elastic bending model for a beam of finite ice thickness can largely explain the GPS-observed surface strain. Using the same model and taking into account the viewing geometry of the satellite radar, it is now possible to separate horizontal and vertical displacement components in the satellite data. As a result we can obtain more realistic ice shelf flexure profiles from the interferometric SAR measurement. The newly derived flexure profiles are therefore more suitable to recover viscoelastic effects of tidal bending in grounding zones of ice shelves and outlet glaciers. These effects would have otherwise remained unnoticed.
Standard test methods for bend testing of material for ductility
American Society for Testing and Materials. Philadelphia
2009-01-01
1.1 These test methods cover bend testing for ductility of materials. Included in the procedures are four conditions of constraint on the bent portion of the specimen; a guided-bend test using a mandrel or plunger of defined dimensions to force the mid-length of the specimen between two supports separated by a defined space; a semi-guided bend test in which the specimen is bent, while in contact with a mandrel, through a specified angle or to a specified inside radius (r) of curvature, measured while under the bending force; a free-bend test in which the ends of the specimen are brought toward each other, but in which no transverse force is applied to the bend itself and there is no contact of the concave inside surface of the bend with other material; a bend and flatten test, in which a transverse force is applied to the bend such that the legs make contact with each other over the length of the specimen. 1.2 After bending, the convex surface of the bend is examined for evidence of a crack or surface irregu...
A study on springback of bending linear flow split profiles
Mahajan, P.; Taplick, C.; Özel, M.; Groche, P.
2016-11-01
The bending of linear flow split profiles made up of high strength materials involves high bending loads leading to high springback and geometrical defects. In addition, the linear flow split profiles are made stronger due to the high plastic deformation applied by the process itself. The bending method proposed in this paper combines the linear flow splitting process with a movable bending tool. The aim of the research was to investigate the effect of superimposed stresses exerted by the linear flow splitting process on bending load and springback of the profile by using a finite element model. The latter was validated by means of experimental results. The results show that the bending loads and the springback were reduced by increasing the superposition of stress applied by the linear flow splitting process. The reduction in the bending loads leads to a reduction in the cross-sectional distortion. Furthermore, the springback was compensated by controlling the amount of superimposed stress.
Bending magnets for the CBA beam-transport line
Thern, R.E.
1983-01-01
The beam-transport line from the AGS to CBA requires 68 large bending magnets, consisting of pure dipoles and two types of combined function gradient magnets. All three types were designed with magnetic-field calculation program POISSON, using the same exterior dimensions and coil package. The design goal of +-1% momentum acceptance for the transport line required a wide horizontal aperture, with a much-smaller vertical aperture for economy. Two prototypes of one gradient magnet were built, and a facility constructed to measure them and the later production magnets. Measurements were done using both a long coil and a point coil (Rawson-Lush gaussmeter). Preliminary results show ..delta..B/B < 0.2 x 10/sup -3/, ..delta..G/G < 0.3 x 10/sup -2/, and ..delta..B/sub 2//B < 0.3 x 10/sup -4/ cm/sup -2/ over the beam aperture. Due to end effects, the actual gradient differs from the design gradient by 1%, which has been compensated for in the beam-line design.
Nomura, T. [Obayashi Corp., Tokyo (Japan)
1999-01-10
In recent years, the construction of long-span bridges is on the increase. Prestressed concrete cable-stayed bridges are dynamically very efficient structures of relatively low cost that blend in well with the landscape. Maintenance is also easy. Consequently, the adoption of edge box girders for cable-stayed bridges is increasing worldwide, but problems related to the aerodynamic stability of the structure have emerged. The aerodynamic stability of edge box girders for a prestressed concrete cable-stayed bridge was investigated under uniform flow conditions by conducting several wind tunnel experiments. As a result, the section of the bridge deck was optimized to prevent torsional flutter within an angle of attack varying from -5 to +5 degrees. It is therefore possible to guarantee the aerodynamic stability of long-span prestressed concrete cable-stayed bridges. (author)
Li, Lun; Li, Aibing; Murphy, Michael A.; Fu, Yuanyuan V.
2016-09-01
Three-dimensional shear wave velocity and radial anisotropy models of the crust and upper mantle beneath the NE Tibetan plateau are constructed from new measurements of Love wave dispersions (20-77s) and previously obtained Rayleigh wave dispersions (20-87s) using a two-plane-wave method. The mid-lower crust is characterized with positive anisotropy (VSH > VSV) with large strength beneath the Qinling and Qilian Mountains and small values beneath the Anyemaqen Mountain. The large positive anisotropy can be explained by horizontal alignment of anisotropic minerals in the mid-lower crust due to crustal flow. The mantle lithosphere above 90 km is largely isotropic while weak positive anisotropy appears beneath 90 km, which probably marks the lithosphere-asthenosphere boundary (LAB). A low shear wave velocity anomaly and relatively negative radial anisotropy are imaged in the entire lithosphere beneath the restraining bend in the eastern Kunlun fault, consistent with a weak lithosphere experiencing vertical thickening under horizontal compression. The asthenosphere at the restraining bend is characterized by significant low velocity and positive radial anisotropy, reflecting that the asthenosphere here is probably hotter, has more melts, and deforms more easily than the surrounding region. We propose that the lithosphere at the restraining bend was vertically thickened and subsequently delaminated locally, and induced asthenosphere upwelling. This model explains the observations of velocity and anisotropy anomalies in the lithosphere and asthenosphere as well as geological observations of rapid rock uplift at the restraining bend of the Kunlun fault.
Traumatic vertical atlantoaxial dislocation.
Payer, M; Wetzel, S; Kelekis, A; Jenny, B
2005-08-01
We present a case of traumatic vertical atlantoaxial dislocation of 16 millimetres with a fatal outcome. We hypothesize that this extremely rare traumatic vertical atlantoaxial dislocation results from insufficiency of the C1/C2 facet capsules after rupture of the tectorial membrane and the alar ligaments.
魏巍
2011-01-01
Taking the erection of 700 t prestressed simply supported box girder along Wuhan-Huangshi special passenger line as the example, the paper sums up the erection equipment and structure characteristic of the box girder and its performance, and illustrates the construction craft of the erection for the box girder and the key points for bearing＇ s perfusion, so as to accumulate relative experience and direct the engineering prac- tice.%以武黄客运专线700t预制简支箱梁架设为例，对箱梁架设设备及其结构特点和性能作了归纳，重点对箱梁架设施工工艺及支座灌注要点进行了阐述，以积累相关施工经验，指导工程实践。
Cricket antennae shorten when bending (Acheta domesticus L.
Catherine eLoudon
2014-06-01
Full Text Available Insect antennae are important mechanosensory and chemosensory organs. Insect appendages, such as antennae, are encased in a cuticular exoskeleton and are thought to bend only between segments or subsegments where the cuticle is thinner, more flexible, or bent into a fold. There is a growing appreciation of the dominating influence of folds in the mechanical behavior of a structure, and the bending of cricket antennae was considered in this context. Antennae will bend or deflect in response to forces, and the resulting bending behavior will affect the sensory input of the antennae. In some cricket antennae, such as in those of Acheta domesticus, there are a large number (>100 of subsegments (flagellomeres that vary in their length. We evaluated whether these antennae bend only at the joints between flagellomeres, which has always been assumed but not tested. In addition we questioned whether an antenna undergoes a length change as it bends, which would result from some patterns of joint deformation. Measurements using light microscopy and SEM were conducted on both male and female adult crickets (Acheta domesticus with bending in four different directions: dorsal, ventral, medial and lateral. Bending occurred only at the joints between flagellomeres, and antennae shortened a comparable amount during bending, regardless of sex or bending direction. The cuticular folds separating antennal flagellomeres are not very deep, and therefore as an antenna bends, the convex side (in tension does not have a lot of slack cuticle to unfold and does not lengthen during bending. Simultaneously on the other side of the antenna, on the concave side in compression, there is an increasing overlap in the folded cuticle of the joints during bending. Antennal shortening during bending would prevent stretching of antennal nerves and may promote hemolymph exchange between the antenna and head.
姜竹生; 瞿涛; 吕磊; 吉伯海
2011-01-01
基于对我国钢箱梁桥的钢箱梁病害调查,总结出我国钢箱粱典型病害的类型,分析各种钢箱梁典型病害产生的机理及导致其破坏的原因,提出了钢箱梁病害的日常检测与维护技术.针对钢箱梁的涂装劣化、钢材腐蚀、结构性损伤等病害,给出了日常检测与维护的主要项目,介绍了人工目视检测、超声波检测、磁粉检测及涡流检测等主要的检测方法的工作原理、优缺点和适用范围.%Based on the survey of China steel box girder bridges' steel box girder defects, summing up the typical defects of China steel box girder, we analyse every typical defect production mechanism and the reasons of leading to destruction of steel box girder, and propose steel box girder defects' daily testing and maintenance technology. According to coating for the deterioration, steel corrosion, structural damage and other defects of steel box girder, we give the main items of the daily testing and maintenance technology and the main detection methods including manual visual inspection, ultrasonic testing, magnetic particle testing and eddy current testing. Studying the working principle of above testing methods, advantages and disadvantages, and scope of application, should be selected based on the actual requirements in the project.
黄家寅
2004-01-01
Under the case of ignoring the body forces and considering components caused by diversion of membrane in vertical direction ( z-direction ), the constitutive equations of the problem of the nonlinear unsymmetrical bending for orthotropic rectangular thin plate with variable thickness are given; then introducing the dimensionless variables and three small parameters, the dimensionaless governing equations of the deflection function and stress function are given.
Rahmah, Fitri; Sekartedjo, Sekartedjo; Hatta, Agus Muhamad
2016-11-01
Modelling of load effect on macro-bend losses for a singlemode-multimode-singlemode (SMS) fiber structure with small bend radius is presented. Load effect on macro-bend losses for the SMS fiber structure placed between two high-density polyethylene (HDPE) boards are investigated theoretically and experimentally. A model on macro-bend losses for SMS fiber structure is constructed by using the light transmission formula in a straight SMS fiber structure and taking into account the effective number of guided modes due to the macrobending. In the experimental, a mandrel with a diameter of 0.8 mm is used to induce the bend. When the loads are applied on the system, the mandrel will affect the bend losses for the SMS fiber structure. It is shown numerically and experimentally that the bend-loss of SMS fiber structure strongly depends on the applied loads and the multimode fiber (MMF) lengths.
Light bending in $f(T)$ gravity
Ruggiero, Matteo Luca
2016-01-01
In the framework of $f(T)$ gravity, we focus on a weak-field and spherically symmetric solution for the Lagrangian $f(T)=T+\\alpha T^{2}$, where $\\alpha$ is a small constant which parameterizes the departure from General Relativity. In particular, we study the propagation of light and obtain the correction to the general relativistic bending angle. Moreover, we discuss the impact of this correction on some gravitational lensing observables, and evaluate the possibility of constraining the theory parameter $\\alpha$ by means of observations.
Anomalous bending effect in photonic crystal fibers.
Tu, Haohua; Jiang, Zhi; Marks, Daniel L; Boppart, Stephen A
2008-04-14
An unexpected transmission loss up to 50% occurs to intense femtosecond pulses propagating along an endlessly single-mode photonic crystal fiber over a length of 1 m. A specific leaky-fiber mode gains amplification along the fiber at the expense of the fundamental fiber mode through stimulated four-wave mixing and Raman scattering, leading to this transmission loss. Bending near the fiber entrance dissipates the propagating seed of this leaky mode, preventing the leaky mode amplification and therefore enhancing the transmission of these pulses.
Thermoelastic bending of locally heated orthotropic shells
Shevchenko, V. P.; Gol'tsev, A. S.
2007-03-01
The thermoelastic bending of locally heated orthotropic shells is studied using the classical theory of thermoelasticity of thin shallow orthotropic shells and the method of fundamental solutions. Linear distribution of temperature over thickness and the Newton's law of cooling are assumed. Numerical analysis is carried out for orthotropic shells of arbitrary Gaussian curvature made of a strongly anisotropic material. The behavior of thermal forces and moments near the zone of local heating is studied for two areas of thermal effect: along a coordinate axis and along a circle of unit radius. Generalized conclusions are drawn
Extension versus Bending for Continuum Robots
George Grimes
2008-11-01
Full Text Available In this paper, we analyze the capabilities of a novel class of continuous-backbone ("continuum" robots. These robots are inspired by biological "trunks, and tentacles". However, the capabilities of established continuum robot designs, which feature controlled bending but not extension, fall short of those of their biological counterparts. In this paper, we argue that the addition of controlled extension provides dual and complementary functionality, and correspondingly enhanced performance, in continuum robots. We present an interval-based analysis to show how the inclusion of controllable extension significantly enhances the workspace and capabilities of continuum robots.
Wooden Model of Wide AA Bending Magnet
1978-01-01
The very particular lattice of the AA required 2 types of dipoles (bending magnets: BLG, long and narrow; BST, short and wide). A wide one had a steel length of 2.71 m, a "good field" width of 0.564 m, and a weight of about 75 t. A wooden model was build in 1978, to gain dimensional experience. Here, Peter Zettwoch, one of the largest men at CERN at that time, is putting a hand in the mouth of the wooden BST monster.
Clinical bending of nickel titanium wires
Stephen Chain
2015-01-01
Full Text Available Since the evolution and the involvement of Nickel Titanium wires in the field of Orthodontics. The treatment plan has evolved with the use of low force Nickel Titanium wires. Because of their high springback, low stiffness, they are the key initial wires in leveling and alignment but have poor formability. Since poor formability limits its ability to create variable arch forms thus; limits the form of treatment. We have devised a method to bend the Nickel Titanium wires to help in our inventory but also customized the wire according to the treatment.
何广宝
2014-01-01
Because of many advantage, such as f being light, high strength and corrosion resistance,car-bon fiber reinforced polymer is widely used in old bridge reinforcement. However, the study on theoretical analysis and numerical simulation is relatively delayed due to its complex mechanical properties com-pared common reinforced concrete girders. The finite element software ANSYS is used to establish an nu-merical simulation model of RC T-sectional girders strengthened with CFRP sheets in the article. The problem of convergence of nonlinear Finite Element Analysis (FEA) is solved in the numerical simulation analysis. The midspan deflection and maximum stress of T-sectional girder after reinforcement reduce by 11.6% and 20.7% respectively compared to initial girder, but the ultimate capacity increases by 52%, which demonstrates that CFRP sheets can improve the mechanical performance of RC beams.%碳纤维复合材料具有轻质、高强以及耐腐蚀等优点，在旧桥加固工程中得到广泛应用，但由于其力学性能和破坏模式比普通钢筋混凝土梁复杂，在理论和数值分析方面的研究相对滞后。依托某T型钢筋混凝土桥梁加固实例，运用ANSYS有限元软件建立模型进行分析，解决了CFRP布加固构件非线性数值求解难以收敛的问题。加固后T型梁的跨中挠度和最大应力相比于加固前分别下降了10.4%和17.1%了，然而极限承载力提升了52%，这表明CFRP布加固可以很好地改善钢筋混凝土梁的受力性能。
The delicate analysis of shear lag effect on trapezoidal box girders%梯形箱梁剪力滞后效应的精细化分析
甘亚南; 石飞停
2014-01-01
引入剪滞翘曲应力自平衡条件的影响，考虑了剪切变形和剪滞效应等因素，设置了三个不同的剪滞纵向位移差函数以准确反映梯形箱梁不同宽度翼板的剪滞变化幅度，提出了一种能对工程中常用箱梁静力学特性分析的精确解法。本文以能量变分原理为基础建立了薄壁箱梁的弹性控制微分方程和自然边界条件，获得了相应广义位移的闭合解。算例中，分析了不同荷载形式、跨宽比和悬臂板长度等因素对箱梁静力学特性的影响，结果显示出引入剪滞翘曲应力自平衡条件的必要性。%In consideration of self-equilibrium condition for shear lag warping stress ,shear deformation and shear lag effect ,three different longitudinal displacement difference functions are employed to accu-rately reflect the amplitude of change of shear lag in the trapezoidal box girders with various widths of wing slabs ,and a new warping displacement mode of trapezoidal thin-walled box girders is chosen to meet the axial self-equilibrium condition for corresponding stress ,a more accurate approach is proposed to analyze the mechanical characteristics of trapezoidal box girders generally used in engineering .Based on the minimum potential principle ,the governing differential equations and related natural boundary conditions are induced ,the closed-form solutions of generalized displacements are obtained .The varia-tions of stress of trapezoidal box girders ,caused by the change of factors such as self-equilibrium condi-tion ,type of loading and ratio of span and width are discussed ,the importance about the introduction of self-equilibrium condition is proved .
Hao Wang
2014-01-01
Full Text Available Train-induced vibration of steel truss bridges is one of the key issues in bridge engineering. This paper talks about the application of tuned mass damper (TMD on the vibration control of a steel truss bridge subjected to dynamic train loads. The Nanjing Yangtze River Bridge (NYRB is taken as the research object and a recorded typical train load is included in this study. With dynamic finite element (FE method, the real-time dynamic responses of NYRB are analyzed based on a simplified train-bridge time-varying system. Thereinto, two cases including single train moving at one side and two trains moving oppositely are specifically investigated. According to the dynamic characteristics and dynamic responses of NYRB, the fourth vertical bending mode is selected as the control target and the parameter sensitivity analysis on vibration control efficiency with TMD is conducted. Using the first-order optimization method, the optimal parameters of TMD are then acquired with the control efficiency of TMD, the static displacement of Midspan, expenditure of TMDs, and manufacture difficulty of the damper considered. Results obtained in this study can provide references for the vibration control of steel truss bridges.
Structure of the Mimas 5:3 Bending Wave in Saturn's Rings
Sega, Daniel D.; Colwell, Josh E.
2016-10-01
Saturn's moon Mimas is on an inclined orbit with several strong vertical orbital resonances in Saturn's rings. The 5:3 inner vertical resonance with Mimas lies in the outer A ring and produces a prominent spiral bending wave (BW) that propagates away from Mimas. While dozens of density waves in Saturn's rings have been analyzed to determine local surface mass densities and viscosities, the number of bending waves is limited by the requirement for a moon on an inclined orbit and because, unlike the Lindblad resonances that excite density waves, there can be no first order vertical resonances. The Mimas 5:3 BW is the most prominent in the ring system. Bending wave theory was initially developed by Shu et al. (1983, Icarus, 53, 185-206) following the Voyager encounters with Saturn. Later, Gresh et al. (1986, Icarus, 68, 481-502) modeled radio science occultation data of the Mimas 5:3 BW with an imperfect fit to the theory. The multitude of high resolution stellar occultations observed by Cassini UVIS provides an opportunity to reconstruct the full three-dimensional structure of this wave and learn more about local ring properties. Occultations at high elevation angles out of the ring plane are insensitive to the wave structure due to the small angles of the vertical warping of the rings in the wave. They thus reveal the underlying structure in the wave region. There is a symmetric increase in optical depth throughout the Mimas 5:3 BW region. This may be due to an increase in the abundance of small particles without a corresponding increase in surface mass density. We include this feature in a ray-tracing model of the vertical structure of the wave and fit it to multiple UVIS occultations. The observed amplitude of the wave and its damping behavior of are not well-described by the Shu et al. model, which assumes a fluid-like damping mechanism. A different damping behavior of the ring, perhaps radially varying across the wave region due to differences in the particle
Biondi, Riccardo; Ho, Shu‐Peng; Randel, William
2013-01-01
The accurate determination of tropical cyclone (TC) cloud-top height and its vertical thermal structure using the GPS radio occultation (RO) technique is demonstrated in this study. Cloud-top heights are determined by using the bending angle anomaly and the temperature anomaly profiles during...
Four-Dimensional Transform Fault Processes: Evolution of Step-Overs and Bends at Different Scales
Wakabayashi, J.; Hengesh, J. V.; Sawyer, T. L.
2002-12-01
Many bends or step-overs along strike-slip faults may evolve by propagation of the strike-slip fault on one side of the structure and progressive shut off of the strike-slip fault on the other side. In such a process, new transverse structures form, old ones become inactive, and the bend or step-over region migrates with respect to materials that were once affected by it. This process is the progressive asymmetric development of a strike-slip duplex. Consequences of this type of step-over evolution include the following: 1. the amount of vertical structural relief in restraining step-over or bend regions is less than expected (apatite fission track ages associated with these step-over regions predate the strike-slip faulting); 2. pull-apart basin deposits are left outside of the active basin and commonly subjected to contractional deformation and uplift; and 3. local basin inversion occurs that is not linked to regional plate motion changes. This type of evolution of step-overs and bends may be common along the dextral San Andreas fault system of California. Examples of pull-apart basin deposits related to migrating releasing () bends or step-overs are the Plio-Pleistocene Merced Formation (tens of km along strike), the Pleistocene Olema Creek Formation (several km along strike) along the San Andreas fault in the San Francisco Bay area, and an inverted colluvial graben exposed in a paleoseismic trench across the Miller Creek fault (meters to tens of meters along strike) in the eastern San Francisco Bay area. Examples of migrating restraining bends or step-overs include the transfer of slip from the Calaveras to Hayward fault in the Mission Peak area, and the Greenville to the Concord fault at Mount Diablo (10 km or more along strike), the offshore San Gregorio fold and thrust belt (40 km along strike), and the progressive transfer of slip from the eastern faults of the San Andreas system to the migrating Mendocino triple junction (over 150 km along strike). Another
Sediment transport in an active erodible channel bend of Brahmaputra river
Tapas Karmaker; Y Ramprasad; Subashisa Dutta
2010-12-01
Spatial variation of sediment transport in an alluvial sand-bed river bend needs to be understood with its inﬂuencing factors such as bank erosion, secondary current formation, land spur and bed-material characteristics. In this study, detailed hydrographic surveys with Acoustic Doppler Current Proﬁler (ADCP) were conducted at an active erodible river bend to measure suspended load, velocity, bathymetric proﬁle and characteristics of the bed material. Study indicates the presence of multi-thread ﬂow in the channel bend. Local variation of sediment transport is primarily controlled by active bank erosion, land spur and sand bar formation. Vertical distribution of suspended sediment concentration follows a power function with normalized depth. Average bed-material concentration at the reach level is computed from observed sediment proﬁles, and is compared against various sediment transport functions. Results show that the sediment transport function suggested by Yang gives better predictions for this reach. Transverse bed slopes at critical survey transects were computed from the bathymetric data and evaluated with analytical approaches. Out of three analytical approaches used, Odgaard’s approach estimates the bed slopes fairly close to the observed one. These two functions are suitable in the Brahmaputra river for further morphological studies.
Bending strain tolerance of MgB2 superconducting wires
Kováč, P.; Hušek, I.; Melišek, T.; Kulich, M.; Kopera, L.
2016-04-01
This work describes the strain tolerance of MgB2 superconductors subjected to variable bending stresses. Bending of MgB2 wire was done at room temperature in different modes: (i) direct bending of straight annealed samples to variable diameters and by (ii) indirect bending by straightening of bent and annealed samples. I c-bending strain characteristics of samples made by in situ PIT and by the internal magnesium diffusion (IMD) process were measured at 4.2 K. The results show a good agreement between the direct and indirect bending mode, which allows easier estimation of limits important for the winding process of MgB2 superconductors with brittle filaments. A comparison of MgB2 wires made by in situ PIT and IMD processes showed improved strain tolerance for IMD due to better grain connectivity the low annealing temperature, which does not appear to reduce the mechanical strength of sheath material.
Flexible bending of aluminum profiles with polyurethane pad
HE Zhu-bin; LIU Gang; WANG Zhong-ren
2006-01-01
The high flexibility of profile bending with hyperelastic pad enables it to be a promising method for small lot or single part production, especially for space frame and roof-rail parts in automotive and aerospace industries. Bending of two aluminum profiles with different sections was carried out to investigate the effect of main process parameters on the bending process. Results show that the shape of the cross-section and its relative thickness and section modulus in bending are the main factors that determine the bending properties of the profiles. Roller stroke, properties of polyurethane pad and constraints on profiles are key factors that determine the bending radius and section deformation of bent profiles. Failures and quality problems met in experiments were also analyzed.
Reduction Bending of Thin Crystalline Silicon Solar Cells
SHEN Lan-xian; LIU Zu-ming; LIAO Hua; TU Jie-lei; DENG Shu-kang
2009-01-01
Reported are the results of reduction the bending of thin crystalline silicon solar ceils after printing and sintering of back electrode by changing the back electrode paste and adjusting the screen printing parameters without effecting the electrical properties of the cell. Theory and experiments showed that the bending of the cell is changed with its thickness of suhstrate, the thinner cell, the more serious bending. The bending of the cell is decreased with the thickness decrease of the back contact paste. The substrate with the thickness of 190μm printing with sheet aluminum paste shows a relatively lower bend compared with that of the substrate printing with ordinary aluminum paste, and the minimum bend is 0.55 mm which is reduced by52%.
Composition of vertical gardens
Sandeva, Vaska; Despot, Katerina
2013-01-01
Vertical gardens are fully functional gardens in areas where there is less oxygen and space, ideal for residential and urban cities where there is no vegetation; occupy a special place in interiors furniture. The gardens occupy an important aesthetic problem. Aesthetic task in vertical gardens can be achieved by forming sectors of identification in the urban landscape through the choice of a particular plant spatial composition and composition, to create comfort and representation in commu...
Chung, Il-Sug; Mørk, Jesper
2010-01-01
A new hybrid vertical cavity laser structure for silicon photonics is suggested and numerically investigated. It incorporates a silicon subwavelength grating as a mirror and a lateral output coupler to a silicon ridge waveguide.......A new hybrid vertical cavity laser structure for silicon photonics is suggested and numerically investigated. It incorporates a silicon subwavelength grating as a mirror and a lateral output coupler to a silicon ridge waveguide....
INVESTIGATION INTO THE SPRINGBACK OF PIPE BENDING USING INDUCTION HEATING
1998-01-01
Stresses and deformation states of pipe bending are investigated under loading or unloading with various pipe materials, size, bending radius and deformation temperature. A theorem of springback of large diameter pipe bending is presented. The experiments are carried out with pipe materials of 20, 10CrMo910 and 12Cr1MoV steel. Results of computations are in good agreement with experiments.
BEND3 mediates transcriptional repression and heterochromatin organization.
Khan, Abid; Prasanth, Supriya G
2015-01-01
Transcription repression plays a central role in gene regulation. Transcription repressors utilize diverse strategies to mediate transcriptional repression. We have recently demonstrated that BEND3 (BANP, E5R and Nac1 domain) protein represses rDNA transcription by stabilizing a NoRC component. We discuss the role of BEND3 as a global regulator of gene expression and propose a model whereby BEND3 associates with chromatin remodeling complexes to modulate gene expression and heterochromatin organization.
Multiple-cladding fibers with reduced bend loss
Tomljenovic-Hanic, Snjezana; Bulla, Douglas A. P.; Ankiewicz, Adrian; Love, John D.; Bailey, Ron
2007-04-01
We demonstrate that a highly bend-resistant fiber can be realized. It is shown theoretically that, by introducing both depressed and elevated rings into the cladding, bending loss can be reduced significantly. A fiber based on this design has been fabricated and characterized as a first step toward achieving this goal. The results show that a multiple-cladding fiber is highly bend resistant when compared with the standard telecom single-mode fiber.
49 CFR 192.315 - Wrinkle bends in steel pipe.
2010-10-01
... 49 Transportation 3 2010-10-01 2010-10-01 false Wrinkle bends in steel pipe. 192.315 Section 192... Transmission Lines and Mains § 192.315 Wrinkle bends in steel pipe. (a) A wrinkle bend may not be made on steel pipe to be operated at a pressure that produces a hoop stress of 30 percent, or more, of SMYS. (b) Each...
Bending response of single layer MoS2.
Xiong, Si; Cao, Guoxin
2016-03-11
Using molecular mechanics (or dynamics) simulations, three different approaches, including the targeted molecular mechanics, four-point bending and nanotube methods, are employed to investigate the bending response of single layer MoS2 (SLMoS2), among which four-point bending is the most accurate approach to determine the bending stiffness according to the continuum theory. It is found that when the bending curvature radius is large enough (e.g. >4 nm), three approaches will give the same bending stiffness of SLMoS2 and the bending behavior is isotropic for SLMoS2, whereas the nanotube method with small tubes (e.g. bending stiffness. Compared with the reported result from the MoS2 nanotube calculated by density functional theory, the revised Stillinger-Weber (SW) and reactive empirical bond-order (REBO) potentials can give the reasonable bending stiffness of SLMoS2 (8.7-13.4 eV) as well as the effective deformed conformation. In addition, since the Mo-S bond deformation of SLMoS2 under bending is similar to that under in-plane tension/compression, the continuum bending theory can quite accurately predict the bending stiffness of SLMoS2 if a reasonable thickness of SLMoS2 is given. For SLMoS2, the reasonable thickness should be larger than the distance between its two S atomic planes and lower than the distance between two Mo atomic planes of bulk MoS2 crystal, e.g. 0.375-0.445 nm.
Bending response of single layer MoS2
Xiong, Si; Cao, Guoxin
2016-03-01
Using molecular mechanics (or dynamics) simulations, three different approaches, including the targeted molecular mechanics, four-point bending and nanotube methods, are employed to investigate the bending response of single layer MoS2 (SLMoS2), among which four-point bending is the most accurate approach to determine the bending stiffness according to the continuum theory. It is found that when the bending curvature radius is large enough (e.g. >4 nm), three approaches will give the same bending stiffness of SLMoS2 and the bending behavior is isotropic for SLMoS2, whereas the nanotube method with small tubes (e.g. <4 nm) cannot give the correct bending stiffness. Compared with the reported result from the MoS2 nanotube calculated by density functional theory, the revised Stillinger-Weber (SW) and reactive empirical bond-order (REBO) potentials can give the reasonable bending stiffness of SLMoS2 (8.7-13.4 eV) as well as the effective deformed conformation. In addition, since the Mo-S bond deformation of SLMoS2 under bending is similar to that under in-plane tension/compression, the continuum bending theory can quite accurately predict the bending stiffness of SLMoS2 if a reasonable thickness of SLMoS2 is given. For SLMoS2, the reasonable thickness should be larger than the distance between its two S atomic planes and lower than the distance between two Mo atomic planes of bulk MoS2 crystal, e.g. 0.375-0.445 nm.
Hot bending with a fiber coupled solid state laser
Bammer, F.; Schumi, T.; Schuöcker, D.
2010-09-01
For bending of brittle materials it is necessary to heat up the forming zone. This can be done with a fiber coupled solid state laser, whose beam is evenly distributed on the bending line with a beam splitter installed in the lower tool (die) of a bending press. With polarization optics the laser beam is divided there into partial beams that are evenly distributed on the bending line with lenses and prisms. A setup for a bending length of 200mm heated by a fiber-coupled 3kW Nd:YAG-laser shows the feasibility of the concept. Successful operation was shown for the Mg-alloy AZ31, which breaks during forming at room temperature, but can be well formed at temperatures in the range of 200-300°C. Other materials benefiting from this method are Ti-alloys, high-strength-Al-alloys, and high-strength-steels. Typical heating times are in the range of up to 5s and much of the heat input is generated during the bending operation where the laser continues to work. Laser Assisted Bending with a fiber coupled solid state laser is a straightforward way to perform the bending of brittle materials in a process as simple as cold bending.
A preliminary bending fatigue spectrum for steel monostrand cables
Winkler, Jan; Fischer, Gregor; Georgakis, Christos T.;
2011-01-01
This paper presents the results of the experimental study on the bending fatigue resistance of high-strength steel monostrand cables. From the conducted fatigue tests in the high-stress, low-cycle region, a preliminary bending fatigue spectrum is derived for the estimation of monostrand cable...... service life expectancy. The presented preliminary bending fatigue spectrum of high-strength monostrands is currently unavailable in the published literature. The presented results provide relevant information on the bending mechanism and fatigue characteristics of monostrand steel cables in tension...
PERMEABILITY OF SALTSTONE MEASUREMENT BY BEAM BENDING
Harbour, J; Tommy Edwards, T; Vickie Williams, V
2008-01-30
One of the goals of the Saltstone variability study is to identify (and, quantify the impact of) the operational and compositional variables that control or influence the important processing and performance properties of Saltstone mixes. A performance property for Saltstone mixes that is important but not routinely measured is the liquid permeability or saturated hydraulic conductivity of the cured Saltstone mix. The value for the saturated hydraulic conductivity is an input into the Performance Assessment for the SRS Z-Area vaults. Therefore, it is important to have a method available that allows for an accurate and reproducible measurement of permeability quickly and inexpensively. One such method that could potentially meet these requirements for the measurement of saturated hydraulic conductivity is the technique of beam bending, developed by Professor George Scherer at Princeton University. In order to determine the feasibility of this technique for Saltstone mixes, a summer student, David Feliciano, was hired to work at Princeton under the direction of George Scherer. This report details the results of this study which demonstrated the feasibility and applicability of the beam bending method to measurement of permeability of Saltstone samples. This research effort used samples made at Princeton from a Modular Caustic side solvent extraction Unit based simulant (MCU) and premix at a water to premix ratio of 0.60. The saturated hydraulic conductivities for these mixes were measured by the beam bending technique and the values determined were of the order of 1.4 to 3.4 x 10{sup -9} cm/sec. These values of hydraulic conductivity are consistent with independently measured values of this property on similar MCU based mixes by Dixon and Phifer. These values are also consistent with the hydraulic conductivity of a generic Saltstone mix measured by Langton in 1985. The high water to premix ratio used for Saltstone along with the relatively low degree of hydration for
佐々木, 善教; 大津, 雅亮; 松村, 正三; 森下, 和幸; 田中, 大樹; 八木, 秀樹; 関根, 雄一郎; 浅川, 基男
2015-01-01
In forming of glasses frame, bending and inverse bending of rim wires with 4 rolls are usually employed. Only an inverse bending roll, the 4th roll, can change the position to control the curvature of the rim wire. A deriving method of inverse bending roll position is proposed in this study. The proposed method requires not the computational simulations but only some simple steady inverse bending experiments to obtain a relationship between inverse bending roll position and bent curvature whi...
箱梁钢筋定位自动检测装置%The automatic detection device for box girder reinforced positioning
邵云
2014-01-01
In order to reduce or eliminate the box girder quality oroblems caused by box girder reinforced orotection layer and ore-stressed oosi-tioning network reinforced deformation and installation not in olace,this oaoer researched the reinforced oositioning of reinforced orotective layer and ore-stressed oositioning network in oost tensioned ore-stressed box beam construction orocess,designed a set of automatic detection each ten-sioned oositioning detection ooint tensioned whether accuracy oositioning or not and disolayed the tensioned oositioning automatic detection de-vice,solved the oroblem of reinforced oositioning detection.%为了减少或消除因箱梁钢筋保护层及预应力定位网钢筋形变和安装不到位而引起箱梁质量问题，对后张法预应力箱梁施工工艺中的钢筋保护层及预应力定位网的钢筋定位进行了研究，设计了一套能自动检测各检测点钢筋是否定位准确并显示的钢筋定位自动检测装置，解决了钢筋定位检测的问题。
On construction technique of arc model at box girder web%箱梁外腹板圆弧模施工技术
梁见
2012-01-01
Combining with the arc model construction of the continuous box girder web at Yijiang Bridge at Wuhu, the paper undertakes the mould installation by adopting various method according to the parameters of the web arc and the field fact, and mainly introduces the technique, including the making and the consolidation of the box girder arc models with two different parameters, so as to have better reference and direction for the similar bridge construction.%结合芜湖弋江桥连续箱梁外腹板圆弧模施工技术，根据外腹板圆弧半径大小，结合现场实际情况，通过采取不同方法进行模板制安施工，详细介绍了两种不同圆弧半径的箱梁圆弧模板的制作、加固等技术，对同类型桥梁施工具有较强的借鉴和指导作用。
Oe, S. [Honshu-Shikoku Bridge Authority, Tokyo (Japan)
1996-05-25
The Akashi straits bridge is the Kobe-Naruto route of the bridge connecting Honshu and Shikoku; the bridge links Kobe in Hyogo prefecture with Awaji Island and, when completed, it will be a 3-span 2-hinge suspension bridge with the longest center effective span in the world. This report centers on the outline of the construction of stiffening girders for the Akashi straits bridge and especially on the characteristics of the engineering method newly employed. As the method of installing the stiffening girders, an overhang installation of face bars was employed which was a time-tested method. As the installing direction of the side spans, it was decided to install them from the anchorage to the tower. At the beginning, six large block installations were performed. A special balance was developed for the installation of short hanger parts for the purpose of enhancing safety and reduction in the process. A rubber-tired transporting truck was adopted for transporting members of framework on the bridge. GPS survey was used as a method for surveying the configuration. The subject engineering method was based on the construction of suspension bridge stiffening trusses in the past Honshu-Shikoku connecting bridge and reinforced with the improvements as above. Since the bridge is in the middle of construction, a subsequent report will hopefully be made on the actual results of the installation and the spanning after the closure. 8 figs., 2 tabs.
On the gravitational seesaw and light bending
Accioly, Antonio; Shapiro, Ilya L
2016-01-01
Local gravitational theories with more than four derivatives are superrenormalizable, and also may be unitary in the Lee-Wick sense. It makes sense to study low-energy properties of these theories, e.g., identify observables which might be useful for experimental detection of higher derivatives. Using an analogy with neutrino Physics, we explore the possibility of a gravitational seesaw mechanism, in which several dimensional parameters of the same order of magnitude produce a hierarchy in the masses of propagating particles and make a relatively light degree of freedom detectable by frequency dependence in the gravitational light bending. It turns out that such a seesaw mechanism in the six- and more-derivative theories is unable to reduce the lightest mass more than in the simplest four-derivative model. Adding more derivatives can only make heavier masses even larger. This fact may be favorable for protecting the theory from instabilities, but makes experimental detection of higher derivatives more difficu...
Secondary turbulent flow in an infinte bend
Christensen, H. Bo; Gislason, Kjartan; Fredsøe, Jørgen
1999-01-01
The flow in an infinite circular bend is inverstigated in both the laminar and fully turbulent flow case, by use of laminar flow solver, a k-e turbulence model, and a fully Reynolds stress turbulence model. The topic of the analysis is to investigate whether a counter-rotating secondary flow cell...... is formed near the surface at the outer bank. This cell might help to stabilise the bank and hereby be an important factor for the morphology in a meandering river. In the laminar runs stability criterion related to a Dean number was estabilshed. In the simulations with the k-e model and the Reynolds stress...... model, the influence of the curvature ratio and cross section geometry on the vortex pattern is investigated. Furthermore, it is demonstrated that an-isotropy of turbulence plays an important role for the structure of flow pattern and existence of an extra flow cell....
Design Study: ELENA Bending Magnet Prototype
Schoerling, D
2013-01-01
The ELENA bending magnet prototype shall prove that the proposed design meets the requirements set by the ELENA beam dynamics. The following points will be discussed in detail: (i) production process of a magnetic yoke diluted with stainless steel plates, (ii) the stability and repeatability of the field homogeneity of such a yoke over the full working range, (iii) choice of soft magnetic steel, (iv) hysteresis effects, (v) mechanical deformations, (vi) thermal insulation to intercept heat load from baking for activation of NEG coating in the vacuum chamber, (vii) end shim design. In order to verify these points the following measurements will be performed: (i) Hall probe scanning, (ii) integrated field homogeneity measurement (DC), (iii) integrated field homogeneity measurement (AC).
Bend-insensitive fiber based vibration sensor
Xu, Yanping; Lu, Ping; Baset, Farhana; Bhardwaj, Vedula Ravi; Bao, Xiaoyi
2014-05-01
We report two novel fiber-optic vibration sensors based on standard telecom bend-insensitive fiber (BIF). A tapered BIF forming a fiber Mach-Zehnder interferometer could measure continuous and damped vibration from 1 Hz up to 500 kHz. An enclosed microcantilever is fabricated inside the BIF by chemical etching and fusion spliced with a readout singlemode fiber that exhibits a frequency range from 5 Hz to 10 kHz with high signal-to-noise ratio (SNR) up to 68 dB. The unique double cladding structure of the BIF ensures both sensors with advantages of compactness, high resistance to the external disturbance and stronger mechanical strength.
Bending of pipes with inconel cladding
Nachpitz, Leonardo; Menezes, Carlos Eduardo B.; Vieira, Carlos R. Tavares [Primus Processamento de Tubos S.A. (PROTUBO), Macae, RJ (Brazil)
2009-07-01
The high-frequency induction bending process, using API pipes coated with Inconel 625 reconciled to a mechanical transformation for a higher degree of resistance, was developed through a careful specification and control of the manufacturing parameters and inherent heat treatments. The effects of this technology were investigated by a qualification process consisting of a sequence of tests and acceptance criteria typically required by the offshore industry, and through the obtained results was proved the effectiveness of this entire manufacturing process, without causing interference in the properties and the quality of the inconel cladding, adding a gain of resistance to the base material, guaranteed by the requirements of the API 5L Standard. (author)
A Study on Residual Stress of U-Bending Heat Transfer Tube using Rotary Draw Bending Processing
Kwak, Ok Gyu; Jang, Kye Hwan; Kim, Won Seok [BHI Co., Haman (Korea, Republic of); Ku, Tae Wan [Pusan National University, Busan (Korea, Republic of)
2016-05-15
The heat transfer tubes can be considered a kind of heat exchange boundary that is direct heat exchange from inside the steam generator. The heat transfer tubes of the steam generator have various bending radius. The heat transfer tubes have the U-shape and L-shape, depending on installed location and arrangement. The forming of the heat transfer tubes can be applied to process of rotary draw bending, roll bending, ram bending and etc. The rotary draw bending process is mainly used, when the bending radius is small. Recently, Alloy 600 or Alloy 690 tubes have been used as material for the heat transfer tubes of the steam generator. The purpose of this study is to evaluate the residual stress of the heat transfer row-1 tubes for deriving the remaining residual stress after U-Bending processing, as a primary study. In this study, the samples of U-Bending tube were made using Rotary Draw Bending Machine by Alloy690 straight tube. This study was measured Residual Stresses of the Row-1 Heat Transfer Tube in Steam Generator. The measurement methods are used two type of the analytical method (FEM) and experimental method (HDM). It was confirmed that the correlation of the measurement of the FEM and HDM methods. The FEM and HDM both methods showed compressive residual stresses. In numerical terms, the HDM is shown that higher value than the FEM.
李粤东; 夏崇滔; 张翼; 巫正伟
2014-01-01
钢箱梁结构因其自身的特性在市政工程建设得到大量运用，钢箱梁吊装施工中空间就位及空形态的控制问题较为突出，其中带纵坡的弧形钢箱梁通过旋转结构找横坡就使得钢箱梁在施工过程中整体空间形态要有控制技术难度更高，极易造成钢箱梁支座托空。该文结合工程实例，就有纵坡且旋转结构找横坡弧形钢箱梁吊装后产生支座托空的处理措施进行论述。%Steel box girder structure is widely applied nowadays for its virtues, but the controlling problems in space location and spatial form in its con-struction are severe, and the finding of cross slope through rotating structure by arc steel box girder with longitudinal slope renders controlling technology of steel box girder over spatial form harder, easily causing empty bearing of steel box girder. The treatment measures for such problem are presented in de-tail.
Coupled-Mode Flutter of Bending-Bending Type in Highly-Flexible Uniform Airfoils
Pourazarm, Pariya; Modarres-Sadeghi, Yahya
2016-11-01
We study the behavior of a highly flexible uniform airfoil placed in wind both numerically and experimentally. It is shown that for a non-rotating highly-flexible cantilevered airfoil, placed at very small angles of attack (less than 1 degree), the airfoil loses its stability by buckling. For slightly higher angles of attack (more than 1 degree) a coupled-mode flutter in which the first and the second flapwise modes coalesce toward a flutter mode is observed, and thus the observed flutter has a bending-bending nature. The flutter onset and frequency found experimentally matched the numerical predictions. If the same airfoil is forced to rotate about its fixed end, the static deflection decreases and the observed couple-mode flutter becomes of flapwise-torsional type, same as what has already been observed for flutter of rotating wind turbine blades. The support provided by the National Science Foundation, CBET-1437988, is greatly acknowledged.
Bending the Curve: Sensitivity to Bending of Curved Paths and Application in Room-Scale VR.
Langbehn, Eike; Lubos, Paul; Bruder, Gerd; Steinicke, Frank
2017-04-01
Redirected walking (RDW) promises to allow near-natural walking in an infinitely large virtual environment (VE) by subtle manipulations of the virtual camera. Previous experiments analyzed the human sensitivity to RDW manipulations by focusing on the worst-case scenario, in which users walk perfectly straight ahead in the VE, whereas they are redirected on a circular path in the real world. The results showed that a physical radius of at least 22 meters is required for undetectable RDW. However, users do not always walk exactly straight in a VE. So far, it has not been investigated how much a physical path can be bent in situations in which users walk a virtual curved path instead of a straight one. Such curved walking paths can be often observed, for example, when users walk on virtual trails, through bent corridors, or when circling around obstacles. In such situations the question is not, whether or not the physical path can be bent, but how much the bending of the physical path may vary from the bending of the virtual path. In this article, we analyze this question and present redirection by means of bending gains that describe the discrepancy between the bending of curved paths in the real and virtual environment. Furthermore, we report the psychophysical experiments in which we analyzed the human sensitivity to these gains. The results reveal encouragingly wider detection thresholds than for straightforward walking. Based on our findings, we discuss the potential of curved walking and present a first approach to leverage bent paths in a way that can provide undetectable RDW manipulations even in room-scale VR.
蔡巍; 江湧; 陈波
2015-01-01
某桥主桥为主跨400 m的斜拉桥，1995年建成通车。在交通量激增、荷载超载、预应力损失等因素作用下，部分桥跨主梁呈现下挠加剧，主梁混凝土出现剥落、露筋及开裂等病害。为抑制主梁下挠不断发展的趋势，采用结构自重减载方式（将混凝土人行道板置换为轻型钢人行道板）来部分减缓主梁下挠，并对箱梁顶板底面粘贴碳纤维布进行加固。采用有限元软件建立主桥模型，计算结构自重减载及粘贴碳纤维布对改善主梁下挠的作用效应。结果表明，将混凝土人行道板置换成轻型钢人行道板后，主梁下挠程度相对减小；碳纤维布与主梁共同参与受力，在一定程度上抑制了混凝土病害进一步发展，也避免了因混凝土开裂而造成的主梁下挠，验证了该加固方案的可行性。%A Bridge was opened to traffic in 1995 .Its main bridge is a cable‐stayed bridge with a main span of 400 m .According to the inspection report ,the downwarping of main girder in some spans had been exarcebated ,the main girder concrete began to spalling ,deteriations including con‐crete spalling ,reinforcement exposure and concrete cracking were also found ,the causes of which can be attributed to the surge of traffic ,over load and prestress loss .To curb the exarcerbation of main girder downwarping ,the way of relieving the self weight of the structure was used to partial‐ly slow down the main girder downwarping ,specifically by replacing the concrete slabs in the side‐walks by the ligh weight steel plates ,and the main girder was strengthened by gluing carbon fiber sheet on the base of the top plate of the box girder .The finite element software was used to estab‐lish the model of the main bridge ,to calculate the effect of structural self weight reduction and car‐bon fiber sheets strengthening on the enhancement of main girder downwarping .The results of the calculation indicate
Effect of Bend Radius on Magnitude and Location of Erosion in S-Bend
Quamrul H. Mazumder
2015-01-01
Full Text Available Solid particle erosion is a mechanical process that removes material by the impact of solid particles entrained in the flow. Erosion is a leading cause of failure of oil and gas pipelines and fittings in fluid handling industries. Different approaches have been used to control or minimize damage caused by erosion in particulated gas-solid or liquid-solid flows. S-bend geometry is widely used in different fluid handling equipment that may be susceptible to erosion damage. The results of a computational fluid dynamic (CFD simulation of diluted gas-solid and liquid-solid flows in an S-bend are presented in this paper. In addition to particle impact velocity, the bend radius may have significant influence on the magnitude and the location of erosion. CFD analysis was performed at three different air velocities (15.24 m/s–45.72 m/s and three different water velocities (0.1 m/s–10 m/s with entrained solid particles. The particle sizes used in the analysis range between 50 and 300 microns. Maximum erosion was observed in water with 10 m/s, 250-micron particle size, and a ratio of 3.5. The location of maximum erosion was observed in water with 10 m/s, 300-micron particle size, and a ratio of 3.5. Comparison of CFD results with available literature data showed reasonable and good agreement.
[Duane vertical surgical treatment].
Merino, M L; Gómez de Liaño, P; Merino, P; Franco, G
2014-04-01
We report 3 cases with a vertical incomitance in upgaze, narrowing of palpebral fissure, and pseudo-overaction of both inferior oblique muscles. Surgery consisted of an elevation of both lateral rectus muscles with an asymmetrical weakening. A satisfactory result was achieved in 2 cases, whereas a Lambda syndrome appeared in the other case. The surgical technique of upper-insertion with a recession of both lateral rectus muscles improved vertical incomitance in 2 of the 3 patients; however, a residual deviation remains in the majority of cases. Copyright © 2011 Sociedad Española de Oftalmología. Published by Elsevier Espana. All rights reserved.
36 CFR 7.41 - Big Bend National Park.
2010-07-01
... 36 Parks, Forests, and Public Property 1 2010-07-01 2010-07-01 false Big Bend National Park. 7.41 Section 7.41 Parks, Forests, and Public Property NATIONAL PARK SERVICE, DEPARTMENT OF THE INTERIOR SPECIAL REGULATIONS, AREAS OF THE NATIONAL PARK SYSTEM § 7.41 Big Bend National Park. (a) Fishing; closed...
Rule bending by morally disengaged detectives : an ethnographic study
Loyens, Kim
2014-01-01
Rule bending is a well-known practice in policing worldwide, often linked to 'noble cause corruption'. This ethnographic study shows how police detectives sometimes consider to creatively bend rules when rule abidance would lead to other values being jeopardized. This paper illustrates that the theo
On the Bending Problem for Large Scale Mapping
Esteban, I.; Booij, O.; Dijk, J.; Groen, F.
2010-01-01
During Simultaneous Localization And Mapping, geometrical constraints are established between map features. These constraints, introduced through measurements and motion prediction, produce a bending effect in the event of closing a large loop. In this paper we present a discussion of the bending pr
On the bending problem for large scale mapping
I. Esteban; O. Booij; J. Dijk; F. Groen
2009-01-01
During Simultaneous Localization And Mapping, geometrical constraints are established between map features. These constraints, introduced through measurements and motion prediction, produce a bending effect in the event of closing a large loop. In this paper we present a discussion of the bending pr
Bending Resistance of Steel Plate-Reinforced Concrete Beam
TIAN Zhimin; CHEN Jie
2006-01-01
The formulas for calculating bending-resistant capacity of a steel plate-reinforced concrete composite beam are derived.To validate the formulas,experiments of the composite beam under three-point bending are carried out.Calculated results based on the formulas are in good agreement with experimental results.
On the bending problem for large scale mapping
Esteban, I.; Booij, O.; Dijk, J.; Groen, F.
2009-01-01
During Simultaneous Localization And Mapping, geometrical constraints are established between map features. These constraints, introduced through measurements and motion prediction, produce a bending effect in the event of closing a large loop. In this paper we present a discussion of the bending
APPLICABILITY OF THE BEND DEVELOPMENT THEORY IN NATURAL ALLUVIAL RIVERS
M.M.RAHMAN; M.A.HAQUE; M.M.HOQUE
2002-01-01
The theoretical conditions for the bend development or attenuation have been reviewed and tested for a study reach of the Meghna river.The field observations in the natural alluvial meander do not support the theories developed for bend development.The limitations of the theory to apply in the natural meandering river are discussed.
Flexible DNA bending in HU-DNA cocrystal structures.
Swinger, Kerren K; Lemberg, Kathryn M; Zhang, Ying; Rice, Phoebe A
2003-07-15
HU and IHF are members of a family of prokaryotic proteins that interact with the DNA minor groove in a sequence-specific (IHF) or non-specific (HU) manner to induce and/or stabilize DNA bending. HU plays architectural roles in replication initiation, transcription regulation and site-specific recombination, and is associated with bacterial nucleoids. Cocrystal structures of Anabaena HU bound to DNA (1P71, 1P78, 1P51) reveal that while underlying proline intercalation and asymmetric charge neutralization mechanisms of DNA bending are similar for IHF and HU, HU stabilizes different DNA bend angles ( approximately 105-140 degrees ). The two bend angles within a single HU complex are not coplanar, and the resulting dihedral angle is consistent with negative supercoiling. Comparison of HU-DNA and IHF-DNA structures suggests that sharper bending is correlated with longer DNA binding sites and smaller dihedral angles. An HU-induced bend may be better modeled as a hinge, not a rigid bend. The ability to induce or stabilize varying bend angles is consistent with HU's role as an architectural cofactor in many different systems that may require differing geometries.
Anharmonic bend-stretch coupling in neat liquid water
Lindner, Joerg; Cringus, Dan; Pshenichnikov, Maxim S.; Voehringer, Peter
2007-01-01
Femtosecond mid-IR spectroscopy is used to study the vibrational relaxation dynamics in neat liquid water. By exciting the bending vibration and probing the stretching mode, it is possible to reliably determine the bending and librational lifetimes of water. The anharmonic coupling between the bendi
Atmospheric Refractive Electromagnetic Wave Bending and Propagation Delay
Mangum, Jeffrey G
2014-01-01
In this tutorial we summarize the physics and mathematics behind refractive electromagnetic wave bending and delay. Refractive bending and delay through the Earth's atmosphere at both radio/millimetric and optical/IR wavelengths are discussed, but with most emphasis on the former, and with Atacama Large Millimeter Array (ALMA) applications in mind. As modern astronomical measurements often require sub-arcsecond position accuracy, care is required when selecting refractive bending and delay algorithms. For the spherically-uniform model atmospheres generally used for all refractive bending and delay algorithms, positional accuracies $\\lesssim 1^{\\prime\\prime}$ are achievable when observing at zenith angles $\\lesssim 75^\\circ$. A number of computationally economical approximate methods for atmospheric refractive bending and delay calculation are presented, appropriate for astronomical observations under these conditions. For observations under more realistic atmospheric conditions, for zenith angles $\\gtrsim 75^...
Sorting of bending magnets for the SSRF booster
HOU Jie; LIU Gui-Min; LI Hao-Hu; ZHANG Man-Zhou
2008-01-01
The Shanghai Synchrotron Radiation Facility(SSRF)booster ring,a full energy injector for the storage ring,is deigned to accelerate the electron beam energy from 150MeV to 3.5GeV that demands high extraction efficiency at the extraction energy with low beam loss rate when electrons are ramping.Closed orbit distortion(COD)caused by bending magnet field uniformity errors which affects the machine performance harmfully could be effectively reduced by bending magnet location sorting.Considering the affections of random errors in measurement,both ideal sorting and realistic sorting are studied based on measured bending magnet field uniformity errors and one reasonable combination of bending magnets which can reduce the horizontal COD by a factor of 5is given as the final installation sequence of the booster bending magnets in this paper.
Sorting of bending magnets for the SSRF booster
Hou, Jie; Liu, Gui-Min; Li, Hao-Hu; Zhang, Man-Zhou
2008-04-01
The Shanghai Synchrotron Radiation Facility (SSRF)booster ring, a full energy injector for the storage ring, is deigned to accelerate the electron beam energy from 150 MeV to 3.5 GeV that demands high extraction efficiency at the extraction energy with low beam loss rate when electrons are ramping. Closed orbit distortion (COD) caused by bending magnet field uniformity errors which affects the machine performance harmfully could be effectively reduced by bending magnet location sorting. Considering the affections of random errors in measurement, both ideal sorting and realistic sorting are studied based on measured bending magnet field uniformity errors and one reasonable combination of bending magnets which can reduce the horizontal COD by a factor of 5 is given as the final installation sequence of the booster bending magnets in this paper. Supported by SSRF Project
Revisit the anomalous bending elasticity of sharply bent DNA
Cong, Peiwen; Chen, Hu; van der Maarel, Johan R C; Doyle, Patrick S; Yan, Jie
2015-01-01
Several recent experiments have suggested that sharply bent DNA has a surprisingly high bending flexibility, but the cause is poorly understood. It has been demonstrated that excitation of flexible defects can explain the results; while whether such defects can be excited under the level of DNA bending in those experiments has remained unclear and been debated. Interestingly, due to experimental design DNA contained pre-existing nicks in nearly all those experiments, while the potential effect of nicks have never been considered. Here, using full-atom molecular dynamics (MD) simulations, we show that nicks promote DNA basepair disruption at the nicked sites which drastically reduced DNA bending energy. In the absence of nicks, basepair disruption can also occur, but it requires a higher level of DNA bending. Overall, our results challenge the interpretations of previous sharp DNA bending experiments and highlight that the micromechanics of sharply bent DNA still remains an open question.
Role of xyloglucan in gravitropic bending of azuki bean epicotyl.
Ikushima, Toshimitsu; Soga, Kouichi; Hoson, Takayuki; Shimmen, Teruo
2008-04-01
The mechanism of the gravitropic bending was studied in azuki bean epicotyls. The cell wall extensibility of the lower side became higher than that of the upper side in the epicotyl bending upward. The contents of matrix polysaccharides of the cell wall (pectin and xyloglucan in hemicellulose-II) in the lower side became smaller than those in the upper side. The molecular mass of xyloglucans in the lower side decreased. After an epicotyl was fixed to a metal rod to prevent the bending, gravistimulation was applied. Fundamentally the same results were obtained with respect to rheological and chemical characteristics of the cell wall as those of epicotyls showing gravitropic bending. The present results suggested that the initial gravitropic bending was caused by the increase in extensibility of the lower side and the decrease in extensibility of the upper side via the change of the cell wall matrix, especially xyloglucans.
Simulation and prediction in laser bending of silicon sheet
WANG Xu-yue; XU Wei-xing; XU Wen-ji; HU Ya-feng; LIANG Yan-de; WANG Lian-ji
2011-01-01
The laser bending of single-crystal silicon sheet (0.2 mm in thickness) was investigated with JK701 Nd:YAG laser. The models were developed to describe the beam characteristics of pulsed laser. In order to simulate the process of laser bending, the FEM softvare ANSYS was used to predict the heat temperature and stress-strain fields. The periodic transformation of temperature field and stress-strain distribution was analyzed during pulsed laser scanning silicon sheet. The results indicate that the mechanism of pulsed laser bending silicon is a hybrid mechanism in silicon bending, rather than a simple mechanism of TGM or BM. This work also gets silicon sheet bent after scanning 6 times with pulsed laser, and its bending angle is up to 6.5°. The simulation and prediction results reach well agreement with the verifying experiments.
Analysis and Simulation of Adiabatic Bend Transitions in Optical Fibers
YAO Lei; LOU Shu-Qin; JIAN Shui-Sheng
2009-01-01
A low-loss criterion for bend transitions in optical fibers is proposed. An optical fiber can be tightly bent with low loss to be adiabatic for the fundamental mode, provided that an approximate upper bound on the rate of change of bend curvature for a given bend curvature is satisfied. Two typical adiabatic bend transition paths, the optimum profile and linear profile, are analyzed and studied numerically. A realizable adiabatic transition with an Archimedean spiral profile is introduced for low bend loss in tightly bent optical fibers. Design of the transitions is based on modeling of the propagation and coupling characteristics of the core and cladding modes,which clearly illustrate the physical processes involved.
Bend-Induced Distortion in Large Mode Area Holey Fibre
TAN Xiao-Ling; GENG You-Fu; ZHANG Tie-Li; WANG Wei-Neng; WANG Peng; YAO Jian-Quan
2008-01-01
A simplified scheme of bend-induced mode distortion is introduced into bent holey fibres,the distorted mode distribution and mode effective area reduction are investigated using the finite difference method.Numerical results show that the modes of bent holey fibres with small bend radius shift away from the core and are deformed greatly,and the mode areas drop significantly as the bend radius decreases,which severely affects the fibre laser performance.The propagation characteristics of bent holey fibres at given wavelength are determined by fill factor and normalized bend radius.Finally,the transition normalized bend radius that represents the location of the mode area beginning to fall off is obtained.
On the Global Ship Hull Bending Energy in Ship Collisions
Pedersen, Preben Terndrup; Li, Y.
2004-01-01
During ship collisions part of the kinetic energy of the involved vessels prior to contact is absorbed as energy dissipated by crushing of the hull structures, by friction and by elastic energy. The purpose of this report is to present an estimate of the elastic energy that can be stored in elastic...... absorbed by the struck ship normally is small and varies from 1 to 6 % of the energy released for crushing. The energy stored as elastic global hull girder vibrations depends on the ship mass, the local stiffness of the side structure, and of the position of contact. The results also show that for highly...... hull vibrations during a ship collision. When a ship side is strengthened in order to improve the crashworthiness it has been argued in the scientific literature that a non trivial part of the energy released for structural deformation during the collision can be absorbed as elastic energy in global...
On the global ship hull bending energy in ship collisions
Pedersen, Preben Terndrup; Li, Yujie
2009-01-01
be stored in elastic hull vibrations during a ship collision. When a ship side is strengthened in order to improve the crashworthiness it has been argued in the scientific literature that a non-trivial part of the energy released for structural deformation during the collision can be absorbed as elastic...... energy absorbed by the struck ship normally is small and varies from 1 to 6% of the energy released for crushing. The energy stored as elastic global hull girder vibrations depends on the ship mass, the local stiffness of the side structure, and of the position of contact. The results also show......During ship collisions part of the kinetic energy of the involved vessels immediately prior to contact is absorbed as energy dissipated by crushing of the hull structures, by friction and by elastic energy. The purpose of this report is to present an estimate of the elastic energy that can...
卢朋
2015-01-01
某客运专线一联道岔连续梁因土堆堆载产生横向偏移，在多跨连续梁桥精确复位中，对同步控制顶升、摩阻自平衡平移技术进行研究。连续箱梁对竖向不均匀位移高度敏感，桥墩与梁底之间空间有限，横向反力台座施工困难，通过对比分析、模拟计算，采用 PLC 计算机同步控制顶升、摩阻自平衡平移技术，能保证顶升过程中的同步性，并巧妙平衡了水平千斤顶横向顶推反力。通过工程实例的应用，证明技术的安全性和可行性。%Due to the load of earth piling,the lateral deviation was occured in a continuous beam of turnout with a joint in a passenger dedicated line,the study on synchronizing control jacking-up technology and self-equation of friction technology for translation in accurate restoring of multi-span continuous beam bridge was introduced.Continuous box girder was highly sensi-tive to vertical non-uniform displacement,and the gap between top of pier and bottom of beam was limited,that caused diffi-culty in construction of lateral counterforce pedestal.By the comparative analysis and simulative calculation,the result showed that synchronizing control jacking-up technology and self-equation of friction technology by adopting PLC computer for translation of continuous box girder could not only ensure the synchronism in jacking-up process,but also subtly balance the lateral jacking counterforce of horizontal jack.The safety and feasibility of technology were proven through application of the project.
Odishelidze; N; Criado-Aldeanueva; F
2010-01-01
This paper addresses the problem of plate bending for a doubly connected body with outer and inner boundaries in the form of regular polygons with a common center and parallel sides.The neighborhoods of the vertices of the inner boundary are equal full-strength smooth arcs symmetric about the rays coming from the vertices to the center,but have unknown positions.Rigid bars are attached to the linear parts of the boundary.The plate bends by the moments applied to the middle point bars.The unknown arcs are free from external stresses.The same problem of plate bending is considered for a regular hexagon weakened by a full-strength hole.Using the methods of complex analysis,the analytical image of Kolosov-Muskhelishvili’s complex potentials (characterizing an elastic equilibrium of the body),the plate deflection and unknown parts of its boundary are determined under the condition that the tangential normal moment on that plate takes a constant value.Numerical analyses are also performed and the corresponding graphs are constructed.
Groß, Thomas; Mödersheim, Sebastian Alexander
2011-01-01
The security of key exchange and secure channel protocols, such as TLS, has been studied intensively. However, only few works have considered what happens when the established keys are actually used—to run some protocol securely over the established “channel”. We call this a vertical protocol com...
2016-01-01
The present invention provides a vertical cavity laser comprising a grating layer comprising an in-plane grating, the grating layer having a first side and having a second side opposite the first side and comprising a contiguous core grating region having a grating structure, wherein an index...
Schrader, Alexander; Martin, Stephen
1998-01-01
Firms that operate at both levels of vertically related Cournot oligopolies will purchase some input supplies from independent rivals, even though they can produce the good at a lower cost, driving up input price for nonintegrated firms at the final good level. Foreclosure, which avoids this stra...... this strategic behavior, yields better market performance than Cournot beliefs...
ZERODUR: bending strength data for etched surfaces
Hartmann, Peter; Leys, Antoine; Carré, Antoine; Kerz, Franca; Westerhoff, Thomas
2014-07-01
In a continuous effort since 2007 a considerable amount of new data and information has been gathered on the bending strength of the extremely low thermal expansion glass ceramic ZERODUR®. By fitting a three parameter Weibull distribution to the data it could be shown that for homogenously ground surfaces minimum breakage stresses exist lying much higher than the previously applied design limits. In order to achieve even higher allowable stress values diamond grain ground surfaces have been acid etched, a procedure widely accepted as strength increasing measure. If surfaces are etched taking off layers with thickness which are comparable to the maximum micro crack depth of the preceding grinding process they also show statistical distributions compatible with a three parameter Weibull distribution. SCHOTT has performed additional measurement series with etch solutions with variable composition testing the applicability of this distribution and the possibility to achieve further increase of the minimum breakage stress. For long term loading applications strength change with time and environmental media are important. The parameter needed for prediction calculations which is combining these influences is the stress corrosion constant. Results from the past differ significantly from each other. On the basis of new investigations better information will be provided for choosing the best value for the given application conditions.
Bending strength of delaminated aerospace composites.
Kinawy, Moustafa; Butler, Richard; Hunt, Giles W
2012-04-28
Buckling-driven delamination is considered among the most critical failure modes in composite laminates. This paper examines the propagation of delaminations in a beam under pure bending. A pre-developed analytical model to predict the critical buckling moment of a thin sub-laminate is extended to account for propagation prediction, using mixed-mode fracture analysis. Fractography analysis is performed to distinguish between mode I and mode II contributions to the final failure of specimens. Comparison between experimental results and analysis shows agreement to within 5 per cent in static propagation moment for two different materials. It is concluded that static fracture is almost entirely driven by mode II effects. This result was unexpected because it arises from a buckling mode that opens the delamination. For this reason, and because of the excellent repeatability of the experiments, the method of testing may be a promising means of establishing the critical value of mode II fracture toughness, G(IIC), of the material. Fatigue testing on similar samples showed that buckled delamination resulted in a fatigue threshold that was over 80 per cent lower than the static propagation moment. Such an outcome highlights the significance of predicting snap-buckling moment and subsequent propagation for design purposes.
2014 land cover land use horseshoe bend
Hanson, Jenny L.; Hoy, Erin E.; Robinson, Larry R.
2016-01-01
This collection of conservation areas consists of the floodplain of the combined streams of the Iowa River and the Cedar River. The study area begins just southeast of Wapello, IA, and continues southeast until the Horseshoe Bend Division, Port Louisa NWR. The area is currently managed to maintain meadow or grassland habitat which requires intensive management due to vegetative succession. In addition, this floodplain area contains a high proportion of managed lands and private lands in the Wetland Reserve Program and is a high priority area for cooperative conservation actions. This project provides a late-summer baseline vegetation inventory to assess future management actions in an adaptive process. Changes in levees, in addition to increased water flows and flood events due to climate change and land use practices, make restoration of floodplain processes more complex. Predictive models could help determine more efficient and effective restoration and management techniques. Successful GIS tools developed for this project would be applicable to other floodplain refuges and conservation areas.
PROGRESS IN STUDIES ON ICE ACCUMULATION IN RIVER BENDS
WANG Jun; CHEN Pang-pang; SUI Jue-yi
2011-01-01
River ice is an important hydraulic element in temperate and polar environments and would affect hydrodynamic conditions of rivers through changes both in the boundary conditions and the thermal regime.The river bend has been reported as the common location for the initiation of ice jams because the water flow along a river bend is markedly affected by the channel curvature.In this article,the experimental studies about the ice accumulation in a river bend are reviewed.Based on experiments conducted so far,the criteria for the formation of ice jams in the river bend,the mechanisms of the ice accumulation in the river bend and the thickness profile of the ice accumulation in the river bend are discussed.The k- ε two-equation turbulence model is used to simulate the ice accumulation under an ice cover along a river bend.A formula is proposed for describing the deformation of the ice jam bottom.Our results indicate that all simulated thickness of the ice accumulation agrees reasonably well with the measured thickness of the ice accumulation in the laboratory.
Fixed bending current for Elekta SL25 linear accelerators.
Kok, J G
2001-01-01
In a medical linear accelerator a bending magnet is used to bend the electron beam produced by the accelerator tube, in the treatment direction. For each electron energy the strength of the magnetic field has to be set to a specific level. Changing the magnetic field strength is done by changing the electric current through the bending magnet. When electron energy and magnetic field strength are not matched, performance of the linac can be affected. As electron energy, magneticfield strength and electrical current through the bending magnet are related to each other, it is reasonable to assume that for each electron energy the correct bending current can be predetermined. This calculated bending current reduces the number of variable parameters used to set up a treatment beam. Predetermining a variable simplifies the tuning procedures. It also prevents a deviation of the electron beam energy being compensated by variation of the bending current. Preventing false machine settings can contribute to increase linac performance and reduce down time and cost of ownership.
郭晓明
2012-01-01
时速350公里客运专线单线后张法单箱单室预应力混凝土简支箱梁属首次应用。为验证其各项指标,进行了4孔箱梁的试验工作;通过对箱梁的各项工艺试验进行研究,充分验证箱梁的设计。%The post-tensioning method single-cell pre-stressed concrete simple box girder for 350 km/h dedicated passenger railway single-track line is used for the first time.To verify its performance indexes,four-truss box girder test is carried out,studies on box girder process tests fully verify the design of box girder.
张强; 王海舰; 胡南
2015-01-01
为研究起升载荷下门式起重机主梁的损伤和疲劳寿命，通过有限元软件ANSYS Workbench建立门式起重机主梁力学模型，采用 nsoft 疲劳分析软件对主梁的动静态力学特性和疲劳损伤进行了分析，采用 nCode GlypWorks中的Rainflow 模块对各载荷作用的应力时间历程进行雨流计数、载荷外推和叠加，采用 nCode GlypWorks中的Stress Life模块计算主梁的疲劳寿命以及敏感性分析，得到不同工况下门式起重机箱型主梁应力和应变云图以及叠加后雨流直方图、主梁损伤直方图、裂纹—寿命关系曲线。研究结果表明：主梁的最大等效应力位置在跨中或端部以及主梁与支腿连接部位，易产生疲劳损伤；40 t以上起重量是造成主梁损伤主要载荷；过载、残余应力和表面粗糙度均对主梁的使用寿命具有明显影响。冲击损伤仿真结果与计算结果较为接近，说明冲击损伤计算结果具有较高的可信度。%In order to study the damage and fatigue life of gantry crane's girder under rising load , the mechanical model of gantry crane's girder was established through the finite element software ANSYS Workbench ,the dynamic and static mechanical properties and fatigue damage of girder were analyzed by using fatigue analysis software nsoft ,the rain flow counting ,the extrapolation superstition of the stress time on load w ere carried out by using Rainflow module in nCode Glyp Works .The life stress module in nCode GlypWorks was used to calculate the fatigue life and ana‐lyze the sensitivity of girder ,through w hich the stress and strain image ,superimposed rain flow histogram ,girder damage histogram and crack‐life relationship curve of gantry crane chassis type girder were got .The results showed that ,the maximum equivalent stress positions appeared in the middle or end of the girder ,the joints of girder and legs where were easy to produce fatigue damage;the lifting
两跨连续斜交梁桥振动台试验研究%Shaking table tests for a two-span continuous skew girder bridge
许永吉; 卓卫东; 孙颖
2016-01-01
The dynamic characteristics and three-dimensional seismic response of a two-span continuous skew girder bridge were analyzed,using parameters,such as,skew angle,shear span ratio,reinforcement ratio and axial compression ratio and so on.Taking a skewed girder bridge of Fujian as an engineering example,a 1 ∶5 scale two-span continuous skewed girder bridge model was designed for shaking table tests.Adopting shaking table tests and FE numerical analysis, the seismic responses and damage characteristics of the skewed girder bridge were studied.Results of shaking table tests showed that the structure's acceleration response and displacement response are guite different under different types of ground motion and at the same site or different types of ground motion and at different sites;under the same skew angle. the smaller the axial compression ratio,the larger the acceleration and displacement responses;when the axial compression ratio is the same,the smaller the skew angle,the larger the acceleration and displacement responses;a reasonable choice of skew angle has a great influence on the dynamic performance of skew bridges in the design of skew bridges.%选取了斜交角、配箍率和轴压比等设计参数，对两跨连续斜交梁桥进行结构动力特性分析和单向地震动输入下结构的地震反应分析。以福建省高速公路某座斜交梁桥为工程背景，设计制作了一座1／5缩尺两跨连续混凝土斜交梁桥试验模型，结合振动台模型试验和数值模拟分析，研究斜交梁桥地震响应及震害特点。振动台模型试验结果表明：不同场地类别的地震动及同一场地类别但不同的地震动作用下，结构的加速度响应、位移响应差别较大；在相同斜交角时，轴压比越小，加速度和位移响应越大；当轴压比相同时，斜交角越小，加速度和位移响应越大。从试验可知，在斜交桥设计中，合理选择斜交角对桥梁动力性能有很大的影响。
Discuss the Full Framing Construction of Cast-in-place Box Girder%浅谈现浇箱粱满堂支架搭设施工
黄亮
2013-01-01
在进行桥梁上部结构的箱梁现浇施工时，满堂支架法的应用已经非常普遍。但是在进行满堂支架法施工时，其施工事故发生的频率也比较高。如何有效提高满堂支架法的施工安全，是值得去深入探究的问题。%During conduct the box girder cast-in-place const-ruction of upper structure in bridge, the application of ful fra-ming method has become so common. But when making ful framing construction method, its construction has a high acide-nt frequency. It is worth to delve into the problem of how to i-mprove the method of ful framing construction safety.
Design of Norway HAKRDANGER Steel Box Girder Bridge Coating Process%挪威HAKRDANGER大桥钢箱梁涂装工艺设计
李连缀; 李敏风
2011-01-01
The anti-corrosion matching scheme and performance of the Norwegian HAKRDANGER bridge steel box girder inside and outside were introduced. The design of coating process including surface treatment, arc spraying zinc process, spray construction process equipment and related technical parameters requirements were introduced in detail.%介绍了挪威HAKRDANGER大桥钢箱梁内外侧防腐配套方案及性能。着重介绍了涂装工艺设计，包括表面处理、电弧喷锌工艺、喷漆施工等工艺设备及相关技术参数要求等。
Mathieson, Haley Aaron
This thesis investigates experimentally and analytically the structural performance of sandwich panels composed of glass fibre reinforced polymer (GFRP) skins and a soft polyurethane foam core, with or without thin GFRP ribs connecting skins. The study includes three main components: (a) out-of-plane bending fatigue, (b) axial compression loading, and (c) in-plane bending of sandwich beams. Fatigue studies included 28 specimens and looked into establishing service life (S-N) curves of sandwich panels without ribs, governed by soft core shear failure and also ribbed panels governed by failure at the rib-skin junction. Additionally, the study compared fatigue life curves of sandwich panels loaded under fully reversed bending conditions (R=-1) with panels cyclically loaded in one direction only (R=0) and established the stiffness degradation characteristics throughout their fatigue life. Mathematical models expressing fatigue life and stiffness degradation curves were calibrated and expanded forms for various loading ratios were developed. Approximate fatigue thresholds of 37% and 23% were determined for non-ribbed panels loaded at R=0 and -1, respectively. Digital imaging techniques showed significant shear contribution significantly (90%) to deflections if no ribs used. Axial loading work included 51 specimens and examined the behavior of panels of various lengths (slenderness ratios), skin thicknesses, and also panels of similar length with various rib configurations. Observed failure modes governing were global buckling, skin wrinkling or skin crushing. In-plane bending involved testing 18 sandwich beams of various shear span-to-depth ratios and skin thicknesses, which failed by skin wrinkling at the compression side. The analytical modeling components of axially loaded panels include; a simple design-oriented analytical failure model and a robust non-linear model capable of predicting the full load-displacement response of axially loaded slender sandwich panels
Tan, S T; Ashworth, G; Czypionka, S; Poole, M D; Briggs, M
1996-06-01
Many pathologic processes may lead to vertical orbital dystopia. We reviewed 47 consecutive cases seen over a 13-year period. Twenty-nine patients underwent eye leveling procedures to improve cosmesis, 2 of these by camouflage procedures and 27 by orbital translocation. Ten patients had 16 secondary operations. There was one death, serious complications occurred in 3 patients, and nuisance complications occurred in 20 others. Seven patients developed diplopia postoperatively, and in 6 patients it was troublesome. In these, it resolved fully in 2 patients, improved to be of no consequence in 2, and in the remaining 2 troublesome symptoms persisted requiring inferior oblique muscle recession in 1. Binocular vision was never restored when not present preoperatively, and in 3 patients temporary loss occurred. There was an overall modest but significant improvement in appearance after surgery. It is concluded that vertical orbital translocation is rewarding and worthwhile.
Four point bending setup for characterization of semiconductor piezoresistance
Richter, Jacob; Arnoldus, Morten Berg; Hansen, Ole
2008-01-01
We present a four point bending setup suitable for high precision characterization of piezoresistance in semiconductors. The compact setup has a total size of 635 cm3. Thermal stability is ensured by an aluminum housing wherein the actual four point bending fixture is located. The four point...... bending fixture is manufactured in polyetheretherketon and a dedicated silicon chip with embedded piezoresistors fits in the fixture. The fixture is actuated by a microstepper actuator and a high sensitivity force sensor measures the applied force on the fixture and chip. The setup includes heaters...
Stored Energy of Plastic Deformation in Tube Bending Processes
Śloderbach, Z.; Pająk, J.
2013-03-01
The paper presents an aproximate analytic method for determination of the stored energy of plastic deformation during cold bending of metal tubes at bending machines. Calculations were performed for outer points of the tube layers subjected to tension and compression (the points of maximum strains). The percentage of stored energy related to the plastic strain work was determined and the results were presented in graphs. The influence and importance of the stored energy of plastic deformation on the service life of pipeline bends are discussed.
Hamiltonian system for orthotropic plate bending based on analogy theory
无
2001-01-01
Based on analogy between plane elasticity and plate bending as well as variational principles of mixed energy, Hamiltonian system is further led to orthotropic plate bending problems in this paper. Thus many effective methods of mathematical physics such as separation of variables and eigenfunction expansion can be employed in orthotropic plate bending problems as they are used in plane elasticity. Analytical solutions of rectangular plate are presented directly, which expands the range of analytical solutions. There is an essential distinction between this method and traditional semi-inverse method. Numerical results of orthotropic plate with two lateral sides fixed are included to demonstrate the effectiveness and accuracy of this method.
Bends in nanotubes allow electric spin control and coupling
Flensberg, Karsten; Marcus, Charles Masamed
2010-01-01
We investigate combined effects of spin-orbit coupling and magnetic field in carbon nanotubes containing one or more bends along their length. We show how bends can be used to provide electrical control of confined spins, while spins confined in straight segments remain insensitive to electric...... fields. Device geometries that allow general rotation of single spins are presented and analyzed. In addition, capacitive coupling along bends provides coherent spin-spin interaction, including between otherwise disconnected nanotubes, completing a universal set of one- and two-qubit gates....
Buffers affect the bending rigidity of model lipid membranes.
Bouvrais, Hélène; Duelund, Lars; Ipsen, John H
2014-01-14
In biophysical and biochemical studies of lipid bilayers the influence of the used buffer is often ignored or assumed to be negligible on membrane structure, elasticity, or physical properties. However, we here present experimental evidence, through bending rigidity measurements performed on giant vesicles, of a more complex behavior, where the buffering molecules may considerably affect the bending rigidity of phosphatidylcholine bilayers. Furthermore, a synergistic effect on the bending modulus is observed in the presence of both salt and buffer molecules, which serves as a warning to experimentalists in the data interpretation of their studies, since typical lipid bilayer studies contain buffer and ion molecules.
Influence of plywood grain direction on sandwich panel bending properties
Jaroslav Kljak; Mladen Brezović; Alan Antonović
2009-01-01
This paper investigates the influence of plywood grain direction on bending properties of a sandwich panel, as well as on stress distribution in each layer. Experimental sandwich panels (tnom= 29 mm) were made of two three-ply plywood panels and a rigid PVC core between them. Grain directions of plywood panels were between 0° and 90°, continuously raised by 15°. Seven models of sandwich panels were made. Bending properties of a sandwich panel was determined by three point bending method and s...
Damage Analysis of Rectangular Section Composite Beam under Pure Bending
Liu, Yiping; Xiao, Fan; Liu, Zejia; Tang, Liqun; Fang, Daining
2013-02-01
Laminated composite beams are commonly used in engineering applications involving macro to nano structures. Based on the assumption that plain sections remain plain after deformation, this paper analyzes stress distributions in cross-ply laminated composite beams with rectangular cross-sections, and formulates the basic damage equations through Kachanov's damage definition and Janson's failure criterion. The location of the neutral axis and the ultimate bending moment are obtained for pure bending cases. The effect of the elastic modulus of the two layers on the damage evolution is analyzed; a reasonable damage composite beam model is proposed to predict the ultimate bending moment.
"Bending the cost curve" in gastroenterology.
Slattery, E; Harewood, G C; Murray, F; Patchett, S
2013-12-01
Increasing attention is being focused on reigning in escalating costs of healthcare, i.e. trying to 'bend the cost curve'. In gastroenterology (GI), inpatient hospital care represents a major component of overall costs. This study aimed to characterize the trend in cost of care for GI-related hospitalizations in recent years and to identify the most costly diagnostic groups. All hospital inpatients admitted between January 2008 and December 2009 with a primary diagnosis of one of the six most common GI-related Diagnosis Related Groups (DRGs) in this hospital system were identified; all DRGs contained at least 40 patients during the study period. Patient Level Costing (PLC) was used to express the total cost of hospital care for each patient; PLC comprised a weighted daily bed cost plus cost of all medical services provided (e.g., radiology, pathology tests) calculated according to an activity-based costing approach; cost of medications were excluded. All costs were discounted to 2009 values. Mean length of stay (LOS) was also calculated for each DRG. Over 2 years, 470 patients were admitted with one of the six most common GI DRGs. Mean cost of care increased from 2008 to 2009 for all six DRGs with the steepest increases seen in 'GI hemorrhage (non-complex)' (31 % increase) and 'Cirrhosis/Alcoholic hepatitis (non-complex)' (45 % increase). No differences in readmission rates were observed over time. There was a strong correlation between year-to-year change in costs and change in mean LOS, r = 0.93. The cost of GI-related inpatient care appears to be increasing in recent years with the steepest increases observed in non-complex GI hemorrhage and non-complex Cirrhosis/Alcoholic hepatitis. Efforts to control the increasing costs should focus on these diagnostic categories.
Advantages of customer/supplier involvement in the upgrade of River Bend`s IST program
Womack, R.L.; Addison, J.A.
1996-12-01
At River Bend Station, IST testing had problems. Operations could not perform the test with the required repeatability; engineering could not reliably trend test data to detect degradation; licensing was heavily burdened with regulatory concerns; and maintenance could not do preventative maintenance because of poor prediction of system health status. Using Energy`s Total Quality principles, it was determined that the causes were: lack of ownership, inadequate test equipment usage, lack of adequate procedures, and lack of program maintenance. After identifying the customers and suppliers of the IST program data, Energy management put together an upgrade team to address these concerns. These customers and suppliers made up the IST upgrade team. The team`s mission was to supply River Bend with a reliable, functional, industry correct and user friendly IST program. The IST program in place went through a verification process that identified and corrected over 400 individual program discrepancies. Over 200 components were identified for improved testing methods. An IST basis document was developed. The operations department was trained on ASME Section XI testing. All IST tests have been simplified and shortened, due to heavy involvement by operations in the procedure development process. This significantly reduced testing time, resulting in lower cost, less dose and greater system availability.
王艳峰; 潘军
2015-01-01
港珠澳大桥浅水区非通航孔桥上部结构采用钢-混组合连续梁。文中主要从桥面板预制、钢主梁整孔制造、钢主梁桥面板组合、组合梁整孔运架，以及组合梁体系转换技术方面阐述了组合梁整孔制造整孔架设技术，体现了大型构件海上施工的“大型化、标准化、工厂化、装配化”理念。%The non-navigable bridge in the shallow water area of the Hong Kong-Zhuhai-Macao Bridge is made of steel-concrete composite structure in the form of continuous box girder structure.This arti-cle expounded the technology of integral fabrication and erection on box girder from fabrication of the precast concrete bridge deck,fabrication of integral span on box girder,combined with steel box gird-er and bridge deck,transport and erection on composite girder,stress system transformation on com-posite girder.It shows the advanced construction concept which is″large-scale,industrialized,stand-ardized and assembled″ in the marine construction.
Flow structure caused by a local cross-sectional area increase and curvature in sharp river bends
Vermeulen, B.
2015-12-01
Horizontal flow recirculation is often observed in sharp river bends, causing a complex three-dimensional flow structure with large implications for the morphological and planimetric development of meanders. Several field observations in small scale systems show that sharp bends are often found in association with a strong increase in cross-sectional area, the deposition of outer bank benches and reattachment bars near the inner bank. Recent studies show that these bends can also occur in large scale systems. In this study, we present field measurements of a sharp bend in the Mahakam River, East Kalimantan, Indonesia. The cross-sectional area increases by a factor of three compared with the reach averaged cross-sectional area. Along a river reach of about 150 km, cross-sectional area correlates strongly with curvature. The field measurements are analyzed together with the results from numerical simulation with a 3D finite element model, which yields a comprehensive view of the intricate flow structure. In turn, the model is used to validate a new equation that captures the water surface topography dependence on cross-sectional area variation and curvature. The results show the importance of the increase in cross-sectional area in the development of horizontal recirculation. Vertical acceleration of the flow into the scour causes the pressure to deviate from a hydrostatic pressure distribution. Strong downflow (up to 12 cm/s) advects longitudinal momentum towards the bed, causing the flow to concentrate in the lower part of the cross-section. This increases the velocity magnitude throughout the cross-section, which is expected to maintain the large scour depth found in several bends along the Mahakam River.
Flow structure caused by a local cross-sectional area increase and curvature in a sharp river bend
Vermeulen, B.; Hoitink, A. J. F.; Labeur, R. J.
2015-09-01
Horizontal flow recirculation is often observed in sharp river bends, causing a complex three-dimensional flow structure with large implications for the morphological and planimetric development of meanders. Several field observations in small-scale systems show that sharp bends are often found in association with a strong increase in cross-sectional area, the deposition of outer bank benches, and reattachment bars near the inner bank. Recent studies show that these bends can also occur in large-scale systems. In this study, we present field measurements of a sharp bend in the Mahakam River, East Kalimantan, Indonesia. The cross-sectional area increases by a factor of 3 compared with the reach-averaged cross-sectional area. Along a river reach of about 150 km, cross-sectional area correlates strongly with curvature. The field measurements are analyzed together with the results from numerical simulation with a three-dimensional finite element model, which yields a comprehensive view of the intricate flow structure. In turn, the model is used to validate a new equation that captures the water surface topography dependence on cross-sectional area variation and curvature. The results show the importance of the increase in cross-sectional area in the development of horizontal recirculation. Vertical acceleration of the flow into the scour causes the pressure to deviate from a hydrostatic pressure distribution. Strong downflow (up to 12 cm s-1) advects longitudinal momentum toward the bed, causing the flow to concentrate in the lower part of the cross section. This increases the velocity magnitude throughout the cross section, which is expected to maintain the large scour depth found in several bends along the Mahakam River.
An Experimental Study of Air-Solid Two-Phase Flow in a 90° Bend Using LDV System
无
1992-01-01
The measurements of he mean streamwise and radial velocities,the associated turbulence and the relative particle densities were made in an air-solid two-phase flow in square sectioned(30mm×30mm) 90° vertical to horizontal bend using laser Doppler velocimetry.The radius ratio of the bedn was 2.0.Glass beads of 100um in diameter were employed to form the solid phase.The measurements of air and solid phases were performed separately at the same bulk velocity 19.34m/s,correaponding to a Reynolds number of 3.87×104.The mass ratio of solid to air was 1.6%,The results indicate that the particle trajectories are very close to straight lines.The streamwise velocity profiles for the gas and the solids cross over near the outer wall with the solids having the higher speed.At θ=30° and 45°，particle-wall collisions happen mostly in the region fromθ=30°to θ=75°,and cause a sudden change in solid velocity,The particles tned to move towards the outer wall in 90°bend,The particle concentration near the outer wall is umch higher than that near the inner wall in the bend,and there are few particles in the inside of the bend.The bend leads to apparent phase separation.atθ=45°,the solids concentrate in the half of the duct near the outer wall,After θ=60° the second peak concentration appears,and goes gradually towards the inner wall.
Monitoring Composites under Bending Tests with Infrared Thermography
Carosena Meola
2012-01-01
Full Text Available The attention of the present paper is focused on the use of an infrared imaging device to monitor the thermal response of composite materials under cyclic bending. Three types of composites are considered including an epoxy matrix reinforced with either carbon fibres (CFRP or glass fibres (GFRP and a hybrid composite involving glass fibres and aluminium layers (FRML. The specimen surface, under bending, displays temperature variations pursuing the load variations with cooling down under tension and warming up under compression; such temperature variations are in agreement with the bending moment. It has been observed that the amplitude of temperature variations over the specimen surface depends on the material characteristics. In particular, the presence of a defect inside the material affects the temperature distribution with deviation from the usual bending moment trend.
Turbulent flow computation in a circular U-Bend
Miloud Abdelkrim
2014-03-01
Full Text Available Turbulent flows through a circular 180° curved bend with a curvature ratio of 3.375, defined as the the bend mean radius to pipe diameter is investigated numerically for a Reynolds number of 4.45×104. The computation is performed for a U-Bend with full long pipes at the entrance and at the exit. The commercial ANSYS FLUENT is used to solve the steady Reynolds–Averaged Navier–Stokes (RANS equations. The performances of standard k-ε and the second moment closure RSM models are evaluated by comparing their numerical results against experimental data and testing their capabilities to capture the formation and extend this turbulence driven vortex. It is found that the secondary flows occur in the cross-stream half-plane of such configurations and primarily induced by high anisotropy of the cross-stream turbulent normal stresses near the outer bend.
Fishery Manangement Plan : Holla Bend National Wildlife Refuge
US Fish and Wildlife Service, Department of the Interior — This plan describes fishery management for Holla Bend National Wildlife Refuge in 1990. The plan outlines goals, objectives for fishery management for the benefit of...
Holla Bend National Wildlife Refuge: Comprehensive Conservation Plan
US Fish and Wildlife Service, Department of the Interior — This Comprehensive Conservation Plan (CCP) was written to guide management on Holla Bend NWR for the next 15 years. This plan outlines the Refuge vision and purpose...
Novel boundary element method for resolving plate bending problems
陈颂英; 王乐勤; 焦磊
2003-01-01
This paper discusses the application of the boundary contour method for resolving plate bending problems. The exploitation of the integrand divergence free property of the plate bending boundary integral equation based on the Kirchhoff hypothesis and a very useful application of Stokes' Theorem are presented to convert surface integrals on boundary elements to the computation of bending potential functions on the discretized boundary points, even for curved surface elements of arbitrary shape. Singularity and treatment of the discontinued corner point are not needed at all. The evaluation of the physics variant at internal points is also shown in this article. Numerical results are presented for some plate bending problems and compared against analytical and previous solutions.
Low Cycle Fatigue of Steel in Strain Controled Cyclic Bending
Kulesa Anna
2016-03-01
Full Text Available The paper presents a comparison of the fatigue life curves based on test of 15Mo3 steel under cyclic, pendulum bending and tension-compression. These studies were analyzed in terms of a large and small number of cycles where strain amplitude is dependent on the fatigue life. It has been shown that commonly used Manson-Coffin-Basquin model cannot be used for tests under cyclic bending due to the impossibility of separating elastic and plastic strains. For this purpose, some well-known models of Langer and Kandil and one new model of authors, where strain amplitude is dependent on the number of cycles, were proposed. Comparing the results of bending with tension-compression it was shown that for smaller strain amplitudes the fatigue life for both test methods were similar, for higher strain amplitudes fatigue life for bending tests was greater than for tension-compression.
Gender differences in variability patterns of forward bending
Villumsen, Morten; Madeleine, Pascal; Jørgensen, Marie Birk
2016-01-01
The variability pattern is highly relevant in the analysis of occupational physical exposures. It is hypothesized that gender differences exist in the variability pattern of forward bending between work and leisure....
1984 Deer Harvest Summary for Holla Bend National Wildlife Refuge
US Fish and Wildlife Service, Department of the Interior — This memo summarizes the 1984 deer harvest for Holla Bend National Wildlife Refuge. Tables summarize numerical findings, including bucks, does, and points.
Narrative report 1968: U. L. Bend National Wildlife Refuge
US Fish and Wildlife Service, Department of the Interior — This annual narrative report for Ul Bend NWR outlines Refuge accomplishments during the 1968 calendar year. The report begins by summarizing the weather conditions,...
Wildlife Inventory Plan : Holla Bend National Wildlife Refuge
US Fish and Wildlife Service, Department of the Interior — This plan describes wildlife inventory in Holla Bend National Wildlife Refuge in 1983. This plan helps achieve refuge objectives by detailing the plan, purpose, and...
Magnetically Assisted Bilayer Composites for Soft Bending Actuators
Sung-Hwan Jang
2017-06-01
Full Text Available This article presents a soft pneumatic bending actuator using a magnetically assisted bilayer composite composed of silicone polymer and ferromagnetic particles. Bilayer composites were fabricated by mixing ferromagnetic particles to a prepolymer state of silicone in a mold and asymmetrically distributed them by applying a strong non-uniform magnetic field to one side of the mold during the curing process. The biased magnetic field induces sedimentation of the ferromagnetic particles toward one side of the structure. The nonhomogeneous distribution of the particles induces bending of the structure when inflated, as a result of asymmetric stiffness of the composite. The bilayer composites were then characterized with a scanning electron microscopy and thermogravimetric analysis. The bending performance and the axial expansion of the actuator were discussed for manipulation applications in soft robotics and bioengineering. The magnetically assisted manufacturing process for the soft bending actuator is a promising technique for various applications in soft robotics.
Active vibration control of structures undergoing bending vibrations
Pla, Frederic G. (Inventor); Rajiyah, Harindra (Inventor)
1995-01-01
An active vibration control subassembly for a structure (such as a jet engine duct or a washing machine panel) undergoing bending vibrations caused by a source (such as the clothes agitator of the washing machine) independent of the subassembly. A piezoceramic actuator plate is vibratable by an applied electric AC signal. The plate is connected to the structure such that vibrations in the plate induced by the AC signal cause canceling bending vibrations in the structure and such that the plate is compressively pre-stressed along the structure when the structure is free of any bending vibrations. The compressive prestressing increases the amplitude of the canceling bending vibrations before the critical tensile stress level of the plate is reached. Preferably, a positive electric DC bias is also applied to the plate in its poling direction.
Preliminary Project Investigation : Holla Bend National Wildlife Refuge
US Fish and Wildlife Service, Department of the Interior — This report covers the proposed expansion of Holla Bend National Wildlife Refuge to increase the quantity and quality of wintering habitat primarily for mallards and...
Energy Dissipation Analysis of Bended SMA Bar in Isothermal State
PENG Gang; LI Li; TAN Jia-xiang
2004-01-01
The theory calculation formula is deduced about stress distribution in cross section and changes in Martensite percentages with the section height of random section shape bar under the action of the bending moment according to the Brinson's Constitutive Relation.The bar's energy dissipation capability under circulation of bending moment was analyzed and the calculation theory was set up. By using MATLAB program and the numerical calculation for uniform rectangle cross section bar, the relationships among the maximal stress and strain on cross section edge with bend load, the stress and Martensite percent's with cross section height, the energy dissipation capability with cross section height, and the energy dissipation capability with maximal strain on cross section edge are gained, also those curves are discused. It is put forward that the SMA material can be used for passive structure vibration control to dissipate energy of bend load.
Tidal bending of glaciers: a linear viscoelastic approach
Reeh, Niels; Christensen, Erik Lintz; Mayer, Christoph;
2003-01-01
In theoretical treatments of tidal bending of floating glaciers, the glacier is usually modelled as an elastic beam with uniform thickness, resting on an elastic foundation. With a few exceptions, values of the elastic (Young's) modulus E of ice derived from tidal deflection records of floating...... glaciers are in the range 0.9-3 GPa. It has therefore been suggested that the elastic-beam model with a single value of E approximate to 1 GPa adequately describes tidal bending of glaciers.In contrast, laboratory experiments with ice give E =93 GPa, i.e. 3-10 times higher than the glacier-derived values....... This suggests that ice creep may have a significant influence on tidal bending of glaciers. Moreover, detailed tidal-deflection and tilt data from Nioghalvfjerdsfjorden glacier, northeast Greenland, cannot be explained by elastic-beam theory. We present a theory of tidal bending of glaciers based on linear...
1984 Deer Harvest Summary for Holla Bend National Wildlife Refuge
US Fish and Wildlife Service, Department of the Interior — This memo summarizes the 1985 deer harvest for Holla Bend National Wildlife Refuge. Tables summarize numerical findings, including bucks, does, and points.
Computational Strategies for the Architectural Design of Bending Active Structures
Tamke, Martin; Nicholas, Paul
2013-01-01
Active bending introduces a new level of integration into the design of architectural structures, and opens up new complexities for the architectural design process. In particular, the introduction of material variation reconfigures the design space. Through the precise specification...... of their stiffness, it is possible to control and pre-calibrate the bending behaviour of a composite element. This material capacity challenges architecture’s existing methods for design, specification and prediction. In this paper, we demonstrate how architects might connect the designed nature of composites...... with the design of bending-active structures, through computational strategies. We report three built structures that develop architecturally oriented design methods for bending-active systems using composite materials. These projects demonstrate the application and limits of the introduction of advanced...
Bending elastic moduli of lipid bilayers : modulation by solutes
Duwe, H.P.; Kaes, J.; Sackmann, E.
1990-01-01
We present high precision measurements of the bending elastic moduli for bilayers of a variety of different lipids and of modifications of the flexural rigidity by solutes. The measurements are based on the Fourier analysis of thermally excited membrane undulations (vesicle shape fluctuations) using a recently developed dynamic image processing method. Measurements of the bending modulus as a function of the undulation wave vector provide information on the limitation of the excitations by th...
An Analysis of Elasto-Plastic Bending of Rectangular Plate
Matsuda, Hiroshi; Sakiyama, Takeshi
1988-01-01
In this paper, a discrete method for analyzing the problem of elasto-plastic bending of a rectangular plate is proposed. The solutions for partial differential equation of rectangular plate are obtained in discrete forms by applying numerical integnltion. An incremental variable elasticity procedure has been used for the clasta-plastic analysis of the rectangular plate. As the applications of the proposed method, clasta-plastic bending of rectangular plate with four types of boundary conditio...
Stress Analysis of a Secondary-Bending Specimen
1993-11-01
Control Office Ansett Airlines of Australia, Library 0 Qantas Airways Limited Hawker de Havilland Aust Pty Ltd, Victoria, Library Hawker de Havilland...MELBOURNE, VICTORIA Technical Note 58 STRESS ANALYSIS OF A SECONDARY-BENDING SPECIMEN 0 by R.L. EVANS M. HELLER Approved for public release C) COMMONWEALTH...AND TECHNOLOGY ORGANISATION AERONAUTICAL RESEARCH LABORATORY Technical Note 58 0 STRESS ANALYSIS OF A SECONDARY-BENDING SPECIMEN by R.L. EVANS 0 M
NUMERICAL SIMULATION FOR LASER BENDING OF SHEET METAL
1998-01-01
The new flexible forming technique of sheet metal-laser bending process is numerically simulated by using finite element method of large elastic-plastic deformation. The temperature fields and stress-strain distribution in deformation area are calculated, forming process is described and relationship between bend angle and width of sheet is discussed. It is shown that the calculated values are in good accordance with the experiments.
Localized bending fatigue behavior of high-strength steel monostrands
Winkler, Jan; Fischer, Gregor; Georgakis, Christos T.
2012-01-01
In this paper, the localized bending fatigue behavior of pretensioned high strength steel monostrands is investigated. Furthermore, a new methodology using an optical photogrammetry system, which can quantify surface deformations on the strand is presented. The system allows measurement of the st......In this paper, the localized bending fatigue behavior of pretensioned high strength steel monostrands is investigated. Furthermore, a new methodology using an optical photogrammetry system, which can quantify surface deformations on the strand is presented. The system allows measurement...
A cylindrical standing wave ultrasonic motor using bending vibration transducer.
Liu, Yingxiang; Chen, Weishan; Liu, Junkao; Shi, Shengjun
2011-07-01
A cylindrical standing wave ultrasonic motor using bending vibration transducer was proposed in this paper. The proposed stator contains a cylinder and a bending vibration transducer. The two combining sites between the cylinder and the transducer locate at the adjacent wave loops of bending vibration of the transducer and have a distance that equal to the half wave length of bending standing wave excited in the cylinder. Thus, the bending mode of the cylinder can be excited by the bending vibration of the transducer. Two circular cone type rotors are pressed in contact to the end rims of the teeth, and the preload between the rotors and stator is accomplished by a spring and nut system. The working principle of the proposed motor was analyzed. The motion trajectories of teeth were deduced. The stator was designed and analyzed with FEM. A prototype motor was fabricated and measured. Typical output of the prototype is no-load speed of 165rpm and maximum torque of 0.45Nm at an exciting voltage of 200V(rms).
Tunable characteristics of bending resonance frequency in magnetoelectric laminated composites
Chen Lei; Li Ping; Wen Yu-Mei; Zhu Yong
2013-01-01
As the magnetoelectric (ME) effect in piezoelectric/magnetostrictive laminated composites is mediated by mechanical deformation,the ME effect is significantly enhanced in the vicinity of resonance frequency.The bending resonance frequency (fr) of bilayered Terfenol-D/PZT (MP) laminated composites is studied,and our analysis predicts that (i) the bending resonance frequency of an MP laminated composite can be tuned by an applied dc magnetic bias (Hdc) due to the △E effect; (ii) the bending resonance frequency of the MP laminated composite can be controlled by incorporating FeCuNbSiB layers with different thicknesses.The experimental results show that with Hdc increasing from 0Oe (1 Oe=79.5775 A/m)to 700 Oe,the bending resonance frequency can be shifted in a range of 32.68 kHz ≤ fr ≤ 33.96 kHz.In addition,with the thickness of the FeCuNbSiB layer increasing from 0 μm to 90 μm,the bending resonance frequency of the MP laminated composite gradually increases from 33.66 kHz to 39.18 kHz.This study offers a method of adjusting the strength of dc magnetic bias or the thicknesses of the FeCuNbSiB layer to tune the bending resonance frequency for ME composite,which plays a guiding role in the ME composite design for real applications.
Dey, Litan; Barbhuiya, Abdul Karim; Biswas, Piya
2017-04-01
Unsteadiness of the vertical velocity profile and secondary flow in open channel bends poses serious problems in hydraulic engineering design. Insertion of vertical submerged vanes in the channel bend at an optimum angle with the tangential component of flow can minimize the unsteadiness and generation of secondary flow resulting in the reduction of scour depth at the outer bank. A series of experiments were conducted in a 180° bend laboratory channel to study flow erosion and effective ness of the submerged vane in reducing scour depth. The average approach to flow velocity at 0.20 m flow depth above the lowest initial bed level was 25 cm/s. An Acoustic Doppler Velocimeter (ADV) was used to measure the three-dimensional time-averaged velocity components at different azimuthal sections on stabilized nonscoured beds without vane. Scour bed profile without vanes shows that bank erosion in a 180° parabolic-shaped bed channel occurs mostly at the zone from bend angles 120° to 140°. Vanes were installed at angles of 10°, 15°, 20°, 30°, and 40° to the tangential flow component maintaining a spacingof 75 cm distance from one vane to another. Experimental results show that a 15° vane angle produces best result in reducing outer bank scour in a parabolic-shaped channel. The data presented in this paper can also be used for validating three-dimensional turbulence models for simulating flows in a curved channel.
Results of new petrologic and remote sensing studies in the Big Bend region
Benker, Stevan Christian
The initial section of this manuscript involves the South Rim Formation, a series of 32.2-32 Ma comenditic quartz trachytic-rhyolitic volcanics and associated intrusives, erupted and was emplaced in Big Bend National Park, Texas. Magmatic parameters have only been interpreted for one of the two diverse petrogenetic suites comprising this formation. Here, new mineralogic data for the South Rim Formation rocks are presented. Magmatic parameters interpreted from these data assist in deciphering lithospheric characteristics during the mid-Tertiary. Results indicate low temperatures (debated timing of tectonic transition (Laramide compression to Basin and Range extension) and onset of the southern Rio Grande Rift during the mid-Tertiary. The A-type and peralkaline characteristics of the South Rim Formation and other pre-31 Ma magmatism in Trans-Pecos Texas, in addition to evidence implying earlier Rio Grande Rift onset in Colorado and New Mexico, promotes a near-neutral to transtensional setting in Trans-Pecos Texas by 32 Ma. This idea sharply contrasts with interpretations of tectonic compression and arc-related magmatism until 31 Ma as suggested by some authors. However, evidence discussed cannot preclude a pre-36 Ma proposed by other authors. The later section of this manuscript involves research in the Big Bend area using Google Earth. At present there is high interest in using Google Earth in a variety of scientific investigations. However, program developers have disclosed limited information concerning the program and its accuracy. While some authors have attempted to independently constrain the accuracy of Google Earth, their results have potentially lost validity through time due to technological advances and updates to imagery archives. For this reason we attempt to constrain more current horizontal and vertical position accuracies for the Big Bend region of West Texas. In Google Earth a series of 268 data points were virtually traced along various early
Liu, C. L.; Kirchengast, G.; Zhang, K. F.; Norman, R.; Li, Y.; Zhang, S. C.; Carter, B.; Fritzer, J.; Schwaerz, M.; Choy, S. L.; Wu, S. Q.; Tan, Z. X.
2013-09-01
Global Navigation Satellite System (GNSS) radio occultation (RO) is an innovative meteorological remote sensing technique for measuring atmospheric parameters such as refractivity, temperature, water vapour and pressure for the improvement of numerical weather prediction (NWP) and global climate monitoring (GCM). GNSS RO has many unique characteristics including global coverage, long-term stability of observations, as well as high accuracy and high vertical resolution of the derived atmospheric profiles. One of the main error sources in GNSS RO observations that significantly affect the accuracy of the derived atmospheric parameters in the stratosphere is the ionospheric error. In order to mitigate the effect of this error, the linear ionospheric correction approach for dual-frequency GNSS RO observations is commonly used. However, the residual ionospheric errors (RIEs) can be still significant, especially when large ionospheric disturbances occur and prevail such as during the periods of active space weather. In this study, the RIEs were investigated under different local time, propagation direction and solar activity conditions and their effects on RO bending angles are characterised using end-to-end simulations. A three-step simulation study was designed to investigate the characteristics of the RIEs through comparing the bending angles with and without the effects of the RIEs. This research forms an important step forward in improving the accuracy of the atmospheric profiles derived from the GNSS RO technique.
Simulation experiments for hot-leg U-bend two-phase flow phenomena
Ishii, M.; Hsu, J.T.; Tucholke, D.; Lambert, G.; Kataoka, I.
1986-01-01
In order to study the two-phase natural circulation and flow termination during a small break loss of coolant accident in LWR, simulation experiments have been performed. Based on the two-phase flow scaling criteria developed under this program, an adiabatic hot leg U-bend simulation loop using nitrogen gas and water and a Freon 113 boiling and condensation loop were built. The nitrogen-water system has been used to isolate key hydrodynamic phenomena from heat transfer problems, whereas the Freon loop has been used to study the effect of phase changes and fluid properties. Various tests were carried out to establish the basic mechanism of the flow termination and reestablishment as well as to obtain essential information on scale effects of parameters such as the loop frictional resistance, thermal center, U-bend curvature and inlet geometry. In addition to the above experimental study, a preliminary modeling study has been carried out for two-phase flow in a large vertical pipe at relatively low gas fluxes typical of natural circulation conditions.
Nowroozi, B N; Brainerd, E L
2012-10-07
Unlike mammalian, disc-shaped intervertebral joints (IVJs), the IVJs in fishes are biconid structures, filled with fluid and thought to act as hydrostatic hinge joints during swimming. However, it remains unclear which IVJ structures are dominant in mechanical resistance to forces in fishes, and whether variation in these tissues might impact the function of the vertebral column along its length. Here, we measured the dynamic mechanical behaviour of IVJs from striped bass, Morone saxatilis. During lateral bending, angular stiffness was significantly lower in the caudal and cervical regions, relative to the abdominal region. The neutral zone, defined as the range of motion (ROM) at bending moments less than 0.001 Nm, was longer in the caudal relative to the abdominal IVJs. Hysteresis was 30-40% in all regions, suggesting that IVJs may play a role in energy dissipation during swimming. Cutting the vertical septum had no statistically significant effect, but cutting the encapsulating tissues caused a sharp decline in angular stiffness and a substantial increase in ROM and hysteresis. We conclude that stiffness decreases and ROM increases from cranial to caudal in striped bass, and that the encapsulating tissues play a prominent role in mechanical variation along the length of the vertebral column.
Milanese, A
2013-01-01
This note provides several analyses of the combined function bending magnets of the SESAME storage ring. The objective is to develop tools to couple the magnetic design to the linear optics specifications. Such tools can be used to carry out a 3D field optimization, at the design phase and following magnetic measurements, in particular in order to fine tune the end shims on the poles. The analyses take as input field maps on the midplane, which are then processed in different ways to obtain linear transfer matrices for the optics, in the horizontal and vertical planes. Some peculiarities of this kind of magnet are also highlighted, for example, the slight variation of gradient along the arc. For convenience, the relative codes and scripts are included in the appendix.
Esteban Dörries
2016-03-01
Full Text Available La introducción de la metodología GPS en aplicaciones topográficas y geodésicas pone en notoria evidencia la clásica separación de sistemas de referencia en horizontal y vertical. Con GPS el posicionamiento es tridimensional, pero el concepto de altura difiere del clásico. Si se desea utilizar la información altimétrica debe contemplarse la ondulación del geoide.
Wu, Ming-Wei, E-mail: mwwu@ntut.edu.tw; Lai, Pang-Hsin
2016-03-21
Selective laser melting (SLM) is a versatile additive manufacturing process for fabricating solid or porous metallic materials with complicated three-dimensional shapes. SLM Ti alloys, particularly Ti-6Al-4V, and other alloys have been manufactured and analyzed in numerous studies. However, the high anisotropy of the microstructures and inconsistent mechanical properties of SLM materials have been extensively reported, and these disadvantages could prohibit its widespread use. To clarify how to alleviate the anisotropic behaviors of SLM materials, the main objective of this study was to evaluate the influences of hot isostatic pressing (HIP) on the microstructure, densification, bending strength, impact toughness, and fracture behavior of the as-built Ti-6Al-4V alloy. The results showed that the vertical and horizontal building directions obviously affect the bending and impact properties of as-built alloys. The transverse rupture strength (TRS) and impact energy of the horizontally-built alloy were respectively found to be 48% and 100% higher than those of the vertically-built one. In the vertically-built alloy, disc-shaped building defects, identified by X-ray computed tomography (CT) and microscopy, obviously reduce the effective load-bearing cross-section and deteriorate the bending and impact performances. After HIP at 1000 °C/150 MPa, the α′-martensite structure in the as-built alloy is transformed into an α+β lamellar one, and the disc-shaped building defects are evidently eliminated. As a result, the impact energies of as-built vertical and horizontal specimens are improved by 28 J (560%) and 19 J (190%), respectively, and the TRS of the as-built vertical alloy is raised by 550 MPa (37%). Consequently, the discrepancies in TRS and impact energy between the HIPed vertical and horizontal specimens are merely 3% and 14%, respectively, and the anisotropic behaviors of the SLM Ti-6Al-4V alloy are thus substantially lessened.
Safdar, Shakeel; Li, Lin; Sheikh, M. A.; Zhu Liu
2007-09-01
Laser forming has received considerable attention in recent years. Within laser forming, tube bending is an important industrial activity, with applications in critical engineering systems like micro-machines, heat exchangers, hydraulic systems, boilers, etc. Laser tube bending utilizes the thermal stresses generated during laser scanning to achieve the desired bends. The parameters to control the process are usually laser power, beam diameter, scanning velocity and number of scans. Recently axial scanning has been used for tube bending instead of commonly used circumferential scans. However the comparison between the scanning schemes has involved dissimilar laser beam geometries with circular beam used for circumferential scanning and a rectangular beam for the axial scan. Thermal stresses generated during laser scanning are strongly dependent upon laser beam geometry and scanning direction and hence it is difficult to isolate the contribution made by these two variables. It has recently been established at the Corrosion and Protection Centre, University of Manchester, that corrosion properties of material during laser forming are affected by the number of laser passes. Depending on the material, the corrosion behaviour is either adversely or favourably affected by number of passes. Thus it is of great importance to know how different scanning schemes would affect laser tube bending. Moreover, any scanning scheme which results in greater bending angle would eliminate the need for higher number of passes, making the process faster. However, it is not only the bending angle which is critical, distortions in other planes are also extremely important. Depending on the use of the final product, unwanted distortions may be the final selection criteria. This paper investigates the effect of scanning direction on laser tube bending. Finite-element modelling has been used for the study of the process with some results also validated by experiments.
覆膜竹胶模板在现浇箱梁施工中的应用%Application of Coated Bamboo Rubber Template in Situ Box Girder Construction
王培国
2012-01-01
The materials of coated bamboo rubber template is light, its processing and demolition is convenient, and it is easy to operate. So it is widely used in the external and internal model construction of situ box girder. This paper, combined with the actual situ box girder construction, discussed characteristics, scope, process, operation points of coated bamboo rubber template in more detail, for the reference in construction.%覆膜竹肢模板具有材质轻、加工及安拆方便、操作简便特点,广泛用于现浇箱梁外、内模施工,本文结合现浇箱粱施工实际,对覆膜竹胶模板的特点、适用范围、工艺流程、操作要点进行了较为详细的论述,以供施工参考.
杨绿峰; 周月娥; 曾有凤
2013-01-01
当前箱型梁剪力滞效应分析的一维离散有限元法对剪力滞函数的处理存在局限性,而且剪力滞系数难以准确反映翼缘截面剪力滞效应及其变化规律.为此,利用箱梁附加挠度代替剪力滞函数建立箱梁翼缘的纵向位移函数,并根据能量变分原理建立控制微分方程并识别了其中的待定参数.以箱梁挠度、附加挠度及其一阶导数作为单元节点位移参数,提出了箱型梁剪力滞效应分析的一维离散有限元法,给出了箱梁的自然边界条件和强迫边界条件.基于箱梁挠度和附加挠度定义了新的剪力滞系数,分析了不同支撑条件对箱型梁剪力滞效应的影响.算例分析证明了该方法的有效性,且具有较高的计算精度；与传统的基于应力的剪力滞系数相比,基于挠度的剪力滞系数能够更加准确地反映箱型梁截面的剪力滞效应及其分布规律.%The shear-lag function in one-dimensional finite element method for box-girders has no definite physical interpretation, and moreover the shear-lag coefficient can not reflect correctly the shear-lag effect and its variation along the axis of box girder. In order to circumvent these problems, the additional deflection function instead of the shear-lag function is incorporated in the longitudinal displacement of the flange of the box girder. The variational principle is employed to identify the undetermined constants in the longitudinal displacement function. Furthermore, the deflection, additional deflection and their first derivatives are adopted as nodal displacement parameters in the discreted finite elements of box-girder, leading to one-dimensional finite element method for the shear-lag effect of box girders. A new shear-lag coefficient is defined in terms of the deflection of the box-girder, based on which the shear-lag effect on box girders is analysed with different boundary conditions considered. Examples show that the shear
大跨径梁桥长期挠度的控制技术研究%Control Technology of Long-term Deflection for Long-span Girder Bridge
黄新哲
2011-01-01
This paper analyzed the development of large-span girder bridge, based on the problems of long-term deflection in large-span girder bridge, put forward the causes of long-term deflection and control measures by an example of a bridge, to provide reference for the relevant project officers.%文章就大跨梁桥发展概况进行了剖析,针对大跨梁桥长期挠度的问题现象,以某大桥为例提出了长期挠度成因及控制措施新途径,以供相关工程人员参考.
方志; 刘明; 郑辉
2015-01-01
In order to study the mechanical behavior of prestressed reactive powder concrete (RPC) box girders ,the flexural behavior tests of two prestressed RPC box girders were carried out .T he force characteristic of RPC box girders and the influence of transverse prestressing force to its flexural performance were studied .The results show that the prestressed RPC box girders display a good deformation capacity ,with a maximal deflection of 1/50 of its span .The crack width and the short‐time stiffness of the RPC box girders can be calculated according to the formula in Technical Specif ication for Fiber Reinforced Concrete Structures (CECS 38 :2004) , with a coefficient of 0 .4 and 0 .2 considering influence from steel fiber , respectively . The transverse prestressing force in the top plate of RPC box girders has little influence on the flexural bearing capacity , but the force can make a more uniform strain distribution of the compressive concrete so as to reduce the shear‐lag effect and increase the ductility of the specimen .By applying a transverse prestressing force of 2 .95 M Pa (only 3 .1% of the RPC prism compressive strength of 94 MPa) at the top plate ,the effective distribution width of box girder increases by 10% ,and ductility index of specimen increases by 3% .The calculated formula to evaluate the cracking moment and the ultimate moment of a prestressed RPC box girders is proposed and verified by the experimental results .%为研究预应力活性粉末混凝土（RPC ）箱梁的正截面受力性能，进行了2片预应力RPC箱梁的抗弯性能试验，研究了RPC箱梁的受力变形特征以及顶板横向预应力对其抗弯性能的影响。结果表明：预应力RPC箱梁具有良好的变形能力，其极限变形可超过跨径的1／50；RPC箱梁正常使用阶段的裂缝宽度和短期刚度可参照《纤维混凝土结构技术规程》（CECS 38：2004）的相应公式计算，其中的钢纤维影响系数可分别取为0
孙宗磊
2012-01-01
结合哈大客运专线沈大段桥梁非标准跨度的特点,从适用、景观、施工控制等方面介绍哈大客运专线变跨结合梁的设计过程,对结合梁外形选择、结构断面选择、施工方案以及计算方法进行了详细介绍.%In view of the characteristics of the bridge with non-standard span on Shenyang-Dalian section of Harbin-Dalian Passenger Dedicated Line, this paper introduces the design process of the composite girder with non-standard span on Harbin - Dalian Passenger Dedicated Line in terms of applicability,landscape and construction control, and explains in detail the selection of girder profile, structural cross-section, construction scheme and calculation method.
A vertical rift in Saturn's inner C ring
Nicholson, Philip D.; Hedman, Matthew M.
2016-11-01
In 1988 Rosen and Lissauer identified an unusual wavelike feature in Saturn's inner C ring as a bending wave driven by a nodal resonance with Titan (Science 241, 690). This is sometimes referred to as the - 1 : 0 resonance since it occurs where the local nodal regression rate is approximately equal to -nT , where nT = 22 .577∘d-1 is Titan's orbital mean motion. We have used a series of 44 stellar occultation profiles of this wave observed by the Cassini VIMS instrument to test their hypothesis. We find that, as predicted, this wave is an outward-propagating m = 1 spiral with a leading orientation and a retrograde pattern speed approximately equal to -nT . But the most intriguing feature associated with the wave is a narrow gap that lies ∼7 km outside the resonance. This gap varies noticeably in width and is seen in roughly 3/4 of the occultation profiles, appearing to rotate with the wave in a retrograde direction. We have developed a simple kinematical model that accounts for the observations and consists of a continuous but very narrow gap (radial width ≃ 0.6 km), the edges of which are vertically distorted by the propagating bending wave as it crosses the region. Differences in viewing geometry then largely account for the apparent width variations. We find vertical amplitudes of 3.8 km for the inner edge and 1.2 km for the outer edge in 2008, with nodes misaligned by ∼110°. Moreover, both edges of the gap are slightly eccentric, with pericenters aligned with Titan, suggesting that the eccentricities are forced by the nearby Titan apsidal resonance. We hypothesize that the gap forms because the local slopes in the bending wave become so great that nonlinear effects result in the physical disruption of the ring within its first wavelength, beyond which point the wave re-establishes itself with a reduced amplitude.
张胜
2016-01-01
某预应力连续箱梁桥运营15年后，箱梁内外出现了较多的裂缝、钢筋锈蚀和台后填土沉降等病害，已影响桥梁结构的正常使用和安全。根据该桥的质量检测报告，提出了箱梁顶板采用增厚钢筋混凝土、箱室顶板内表面采用粘贴钢板和碳纤维相结合以及箱梁腹板粘贴钢板的加固方法。通过理论计算和荷载试验对加固后的桥梁承载力进行了验算和检测，结果表明，结构承载力和刚度都有明显地提高，能保证桥梁的正常使用。%A prestressed continuous box girder bridge appeared various diseases in fifteen years, for instance, cracks of the inside and outside surface of the box girder, steel corrosion and the obvious settlement of filling at back abutment. The disease has affected the normal use and safety of the bridge structure. Based on the testing reports of the bridge, a feasible strengthening method is put forward: The roof of box girder is strengthened by the thick reinforced concrete;The top plate of the box is strengthened by steel plate and carbon fiber, and box girder webs is strengthened by steel plate. The carrying capacity of the reinforced bridge is checked by the theoretical calculation and the load test. The results show that the bearing capacity and stiffness of the structure are obviously improved and can meet the requirements of normal use.
Prediction of Vertical-Plane Wave Loading and Ship Responses in High Seas
Wang, Zhaohui; Xia, Jinzhu; Jensen, Jørgen Juncher
2000-01-01
The non-linearities in wave- and slamming-induced rigid-body motions and structural responses of ships such as heave, pitch and vertical bending moments are consistently investigated based on a rational time-domain strip method. A hydrodynamic model for predicting sectional green water force.......From the rather extensive computations and comparisons, it is found that non-linear effects are significant in head and bow waes in the motion-wave resonant region for both heave and pitch motions, bow accelerations and vertical bending moments for two container ships considered, whereas not significant...... for a VLCC. The non-linearities in motions and structural loads of conventional monohull ships seem well predicted by the present non-linear strip theory....
赵志强; 姚成
2012-01-01
According to the application of the combined support structure with the anti-sliding pile and lattice girder in the slope treatment, the paper points out the idea of considering the deformation coordination of the anchor cable, the anti-sliding pile and the lattice girder, adopts the finite element software., ABAQUS to undertake the simulation, and concludes the deformation coordination design methods with the anti-sliding pile, the lattice girder and the anchor cable can enhance the slope consolidation effect after the comparative analysis of the results.%针对边坡治理中应用的支护结构——抗滑桩与格构梁联合支护，在设计方法上提出了考虑锚索、抗滑桩、格构梁三者变形协调的思想；利用有限元软件ABAQUS模拟，通过计算结果对比分析，得到了考虑抗滑桩、格构梁以及桩上锚索三者变形协调的设计方法更有利于边坡加固效果的结论。
折线形腹板钢梁的局部承压性能有限元分析%The finite element analysis on folded web steel girder under patch loading
庄晖; 黄炳生
2012-01-01
The steel beams with folded webs are produced by substituting the folded webs for flat webs, this is a kind of the steel girders with corrugation webs. And such products have superior load-carrying capacity and favorable economic advantages. At present,studies on the behavior of the steel girders under patch loading are scarce at home and abroad. So this paper presents the finite element analysis on folded wed steel girders under patch loading. Observe the failure of the models and the factors that influence the ultimate capacity. Prepare for the text success.%折线形腹板钢梁是将传统钢梁中的平腹板用折线形钢板来代替,是波纹腹板钢梁的一种.该钢梁具有较高的承载力及良好的经济优势.目前,在国内外仅对梯形腹板钢梁的局部承压性能有少量研究.本文作者采用有限元方法对折线形腹板钢梁局部承压性能进行研究,了解其在实际试验中可能发生的破坏模式和各因素对其局部承压力性能的影响,并为今后试验作准备.
展之芳
2014-01-01
In steel structure project, fabrication process of steel box girder is complex, so it is difficult to control welding deformation. This paper introduced the fabrication process of steel box girder for RP gantry in nuclear power station from the material, assembly, welding and correction. The fabrication process ensures the overall geometry of box girder, and guarantees the effective control of welding deformation and welding quality, achieves a certain economic benefits.%钢结构工程中，箱形钢梁制作工艺复杂，焊接变形控制困难。通过从下料、组装、焊接、矫正等方面详细介绍了核电站RP龙门架箱形钢结构梁的制作工艺过程，该过程保证了箱形钢梁的整体几何尺寸，同时又保证了焊接质量并有效控制了焊接变形，取得了一定经济效益。
王志峰
2015-01-01
Combining with urban rail transit steel structure shelter with variable section box girder as an example,the paper studies construction quality control and limited hoisting construction of steel structure shelter with elevated platform arc variable-section box girder,and solves difficul-ties occurring in quality control and field limitation hoisting process of variable section box girder installation,which has accumulated experience for similar engineering.%结合某市城市轨道交通变截面箱梁钢结构雨篷施工实例，对高架站变截面箱梁钢结构雨篷制作质量控制及场地受限吊装施工展开了技术研究，解决了变截面箱形梁制作安装过程中质量控制及场地受限时吊装过程中的难题，为其他类似工程积累了经验。
杨鹏健
2015-01-01
结合350km/h高速铁路常用跨度无砟轨道单线简支箱梁通用参考图设计，介绍该箱梁在梁高、桥面宽度、二期恒载、支座横向中心距、梁端构造等方面的受力分析以及从景观性、经济性方面阐述腹板斜率、外轮廓圆弧倒角等细部构造，并通过计算分析选定合理值。%Based on the General Reference Drawing for Simple Supported Box Girder with Common Span on Balastless Single Track for 350 km/h High Speed Railways, this paper focuses on the analysis of stresses with respect to girder height, bridge deck width, secondary dead load, transverse center distance of bearing, girder end structure, and web slope and arc chamfering of outer contour and other micro structures are illustrated in terms of outlook and economy. Furthermore, reasonable values for these parameters are determined through calculation.
申杨凡; 续琦峰; 杨斌; 王绍全; 郭凯强; 王艳琪; 贾艳敏
2015-01-01
为了分析并对比钢箱梁与钢桁架人行天桥的力学性能，建立了两者的ANSYS有限元计算模型，通过静力分析，得出钢桁架人行天桥的承载力更大，通过动力特性分析，钢桁架人行天桥较钢箱梁人行天桥更易产生扭转，且钢箱梁的自振频率较钢桁架的自振频率要大。%In order to analyze and contrast the steel box girder and steel truss pedestrian bridge mechanical properties,the ANSYS finite element calculation model is established,by static analysis,we can draw the steel truss of pedestrian bridge bearing capacity is larger,through the analy-sis of the dynamic characteristics of the pedestrian steel truss bridge with steel box girder footbridge reverse easier to be produced,and the natural frequency of vibration of the steel box girders for bigger than the natural frequency of vibration of steel truss.
Improving bending stress in spur gears using asymmetric gears and shape optimization
Pedersen, Niels Leergaard
2010-01-01
Bending stress plays a significant role in gear design wherein its magnitude is controlled by the nominal bending stress and the stress concentration due to the geometrical shape. The bending stress is indirectly related to shape changes made to the cutting tool. This work shows that the bending...
Mismatch between the PSB and CPS due to the present vertical recombination scheme
Jansson, A
1997-01-01
The production of the nominal LHC beam will deamand optimum emittance preservation between individual machines in the injection chain. The edge effects at the entry and exit of the bending magnets used for the vertical recombination of the four PS booster rings to the level of the CPS results in a small uncompensated, and for each ring different, mismatch. We present recent measurements of the mismatch done in the PSB measurement line.
Flexible Dye-Sensitized Solar Cell Based on Vertical ZnO Nanowire Arrays
Chu Sheng
2011-01-01
Full Text Available Abstract Flexible dye-sensitized solar cells are fabricated using vertically aligned ZnO nanowire arrays that are transferred onto ITO-coated poly(ethylene terephthalate substrates using a simple peel-off process. The solar cells demonstrate an energy conversion efficiency of 0.44% with good bending tolerance. This technique paves a new route for building large-scale cost-effective flexible photovoltaic and optoelectronic devices.
A rational fraction polynomials model to study vertical dynamic wheel-rail interaction
Correa García, Nekane; García Vadillo, Ernesto; Santamaría Manrique, Javier; Gómez López, Josu
2012-01-01
This paper presents a model designed to study vertical interactions between wheel and rail when the wheel moves over a rail welding. The model focuses on the spatial domain, and is drawn up in a simple fashion from track receptances. The paper obtains the receptances from a full track model in the frequency domain already developed by the authors, which includes deformation of the rail section and propagation of bending, elongation and torsional waves along an infinite track. Transformation b...
Research on High Speed Maglev Transrapid Girder-on-Bridge System%高速磁浮桥上梁轨道系统方案研究
成广伟
2012-01-01
针对高速磁浮交通新项目前期选线中主要采用的高架线路方案开展了相关工程化应用研究,并介绍了针对高速磁浮高架线路轨道系统方案的优化研究进展.研究立足于优化磁浮系统布置、提高安全疏散效率、节约用地、提高环境保护水平等原则,明确了桥上梁轨道系统方案及相关系统设备布置,提出了结合桥上梁形式的安全疏散逃生方案.通过动模型试验与有限元仿真分析方法,研究了磁浮列车通过桥上梁结构时的空气动力学性能,表明磁浮列车的高速通过空气动力学性能符合要求;结合上海磁浮示范线进行了桥上梁方案的在线模拟展示和降噪性能测试,结果表明,结合声屏障,可将磁浮列车高速气动噪声降低最高13 dB(A).研究结论在相关工程方案中得到了应用,可为类似高速交通系统工程提供参考.%The construction application study on the elevated structure proposed in the new high speed rnaglev transportation line and the advances on the high speed maglev transrapid girder-on-bridge system are introduced in this paper. New practical elevated guideway system is designed based on the principles of optimization of the maglev system arrangement, high escape efficiency, economic use of land and better environment protection, etc. One new guideway system type is provided together with the system arrangement, and one new escape system is provided which can be used in the girder on bridge maglev system. With model test and simulation analysis, the aerodynamic effect of this structure when maglev trains passing was examined, and the test results show that the aerodynamic effect when maglev vehicle passing by is acceptable. This girder on bridge system was presented on the Shanghai maglev demonstration line, and the noise reduction effect was tested. Test results show that noise can be reduced to 13 dB( A) with the barrier screen fixed. Conclusions introduced in this paper
Observation of picometer vertical emittance with a vertical undulator.
Wootton, K P; Boland, M J; Dowd, R; Tan, Y-R E; Cowie, B C C; Papaphilippou, Y; Taylor, G N; Rassool, R P
2012-11-09
Using a vertical undulator, picometer vertical electron beam emittances have been observed at the Australian Synchrotron storage ring. An APPLE-II type undulator was phased to produce a horizontal magnetic field, which creates a synchrotron radiation field that is very sensitive to the vertical electron beam emittance. The measured ratios of undulator spectral peak heights are evaluated by fitting to simulations of the apparatus. With this apparatus immediately available at most existing electron and positron storage rings, we find this to be an appropriate and novel vertical emittance diagnostic.
Direct Observation of Ultralow Vertical Emittance using a Vertical Undulator
Wootton, Kent
2015-09-17
In recent work, the first quantitative measurements of electron beam vertical emittance using a vertical undulator were presented, with particular emphasis given to ultralow vertical emittances [K. P. Wootton, et al., Phys. Rev. ST Accel. Beams, 17, 112802 (2014)]. Using this apparatus, a geometric vertical emittance of 0.9 ± 0.3 pm rad has been observed. A critical analysis is given of measurement approaches that were attempted, with particular emphasis on systematic and statistical uncertainties. The method used is explained, compared to other techniques and the applicability of these results to other scenarios discussed.
Advances and Trends on Tube Bending Forming Technologies
YANG He; LI Heng; ZHANG Zhiyong; ZHAN Mei; LIU Jing; LI Guangjun
2012-01-01
As one kind of key components with enormous quantities and diversities,the bent tube parts satisfy the increasing needs for lightweight and high-strength product from both materials and structure aspects.The bent tubes have been widely used in many high-end industries such as aviation,aerospaee,shipbuilding,automobile,energy and health care.The tube bending has become one of the key manufacturing technologies for lightweight product forming.Via the analysis of bending characteristics and multiple defects,advances on exploring the common issues in tube bending are summarized regarding wrinkling instability at the intrados,wall thinning (cracking) at the extrados,springback phenomenon,cross-section deformation,forming limit and process/tooling design/optimization.Some currently developed bending techniques are reviewed in terms of their advantages and limitations.Finally,in view of the urgent requirements of high-performance complex bent tube components with difficult-to-deform and lightweight materials in aviation and aerospace fields,the development trends and corresponding challenges are presented for realizing the precise and high-efficiency tube bending deformation.
Hysteresis of the resonance frequency of magnetostrictive bending cantilevers
Löffler, Michael; Kremer, Ramona; Sutor, Alexander; Lerch, Reinhard
2015-05-01
Magnetostrictive bending cantilevers are applicable for wirelessly measuring physical quantities such as pressure and strain. Exploiting the ΔE-effect, the resonance frequency of the cantilevers is shifted because of a change in the magnetic biasing field. The biasing field, in turn, depends on the applied pressure or strain, respectively. With a view to the application as a reliable sensor, maximum sensitivity but minimum hysteresis in the biasing field/resonance frequency dependence is preferred. In this contribution, monomorph bending cantilevers fabricated using magnetostrictive Fe49Co49V2 and Metglas 2605SA1 are investigated regarding their applicability for future sensors. For this purpose, the biasing field-dependent polarization of the magnetostrictive materials and bending of the cantilevers are determined. Furthermore, a setup to magnetically bias the cantilevers and determine the bending resonance frequency is presented. Here, the resonance frequency is identified by measuring the impulse response employing a laser Doppler vibrometer. The measurement results reveal that cantilevers made of Fe49Co49V2 possess a distinct hysteretic behaviour at low magnetic biasing field magnitudes. This is ascribed to the polarization and bending hysteresis. Cantilevers fabricated using Metglas 2605SA1 feature a lower resonance frequency shift compared to cantilevers with Fe49Co49V2, which would result in a lower sensitivity of the sensor. However, their resonance frequency hysteresis is almost negligible.
Investigation of span-chordwise bending anisotropy of honeybee forewings
JianGuo Ning
2017-05-01
Full Text Available In this study, the spanwise and chordwise bending stiffness EI of honeybee forewings were measured by a cantilevered bending test. The test results indicate that the spanwise EI of the forewing is two orders of magnitude larger than the chordwise EI. Three structural aspects result in this span-chordwise bending anisotropy: the distribution of resilin patches, the corrugation along the span and the leading edge vein of the venation. It was found that flexion lines formed by resilin patches revealed through fluorescence microscopy promoted the chordwise bending of the forewing during flapping flight. Furthermore, the corrugation of the wing and leading edge veins of the venation, revealed by micro-computed tomography, determines the relatively greater spanwise EI of the forewing. The span-chordwise anisotropy exerts positive structural and aerodynamic influences on the wing. In summary, this study potentially assists researchers in understanding the bending characteristics of insect wings and might be an important reference for the design and manufacture of bio-inspired wings for flapping micro aerial vehicles.
Bending moment of galvanized iron glass fiber sandwich panel
Gurustal Somnath Swamy
2016-05-01
Full Text Available The main objective of this project is to prepare a laminated with Galvanized iron thickness fractions, fiber volume fractions and orientation in the layers of GF were fabricated by hand lay-up method and evaluated for their bending moment properties of the sandwich panel using universal testing machine. This paper theoretically calculates the bending behavior of sandwich panel. The recent need to develop a new range of materials has resulted in the development of high performance lightweight composites with excellent properties. Metal– composite systems consist of alternating layers of metal and fiber-reinforced polymer composites which are bonded by an adhesive. Sandwich beams were tested under Air Bending. Stress-strain and stress-displacement were recorded by using AIMIL UTM. The beam face sheets exhibited a softening non-linearity on the bending side. Experimental results were in good agreement with predictions from simple models. On an overall basis, the sandwich panel exhibited better bending moment performance than the monolithic galvanized iron
Photomechanical Energy Conversion of Photoresponsive Fibers Exhibiting Bending Behavior
Kazuya Nakata
2012-01-01
Full Text Available Photoresponsive fibers based on poly(acrylamide (PAA with methylene blue (MB dye were prepared. All semicircular fibers show bending towards the direction of the flat surface of the fiber when illuminated. The fibers recover their initial shape when the illumination stops. The fiber is heated upon illumination and cooled to room temperature once the illumination is stopped. The fiber also is sensitive to humidity, showing bending behavior towards the direction of the flat surface of the fiber upon changing the humidity. The mechanical energy of the PAA/MB fiber is approximately 0.6 mN for the bending direction when it is illuminated. A possible mechanism for the bending behavior is as follow: (1 the fiber is heated upon illumination because of the photothermal effect, (2 the fiber loses water molecules, (3 the fiber shrinks; bending towards the direction of the flat surface of the fiber occurs because of a difference in the shrinkage for the flat surface and the other side of the fiber. Finally, we demonstrated that a PP ball (1.5 mg can be moved by the mechanical energy produced by the changing shape of the fiber upon illumination.
Curvature optical fiber sensor by using bend enhanced method
Jianrong ZHANG; Hairong LIU; Xinkun WU
2009-01-01
Deflection curvature measurement can offer a number of advantages compared with the well-established strain measurement alternative. It is able to measure thin structure; fiber has no resistance with force, which leads to a high precision. There are many kinds of curvature gauges with different operation principles. A low-cost curvature optical fiber sensor using bend enhanced method to improve its curvature measurement sensitivity was devel-oped in recent years. This sensor can distinguish between convex bending and concave bending and has a good linearity in measuring large curvature deformation. Whisper gallery ray theory and Monte Carlo simulation are new achievements by computer experiment. The operation mechanism of this curvature optical fiber sensor is presented based on light scattering theory. The attenuation is ascribed to the transmission mode changing by the curvature of the fiber, which affects the attenuation of the surface scattering. The mathematical model of relationship among light loss, bending curvature, surface roughness, and parameters of the fiber's configuration is also presented. We design different kinds of shapes of sensitive zones; each zone has different parameters. Through detecting their output optical attenuations in different curvatures and fitting the results by exponential decaying functions, the proposed model is demonstrated by experimental results. Also, we compare the experi-mental results with the theoretical analysis and discuss the sensitivity dependence on bending direction.
Are "uncharacteristic" earthquakes spatially linked to strike-slip restraining bends?
Mann, P.
2011-12-01
, the Haiti earthquake of 2010 showed similar "uncharacteristic" elements: the large M 7.2 shock generated high intensity ground shaking on a previously unknown subsurface thrust fault, produced extensive slope failures, produced a broad pattern of vertical uplift extending several kilometers north of the main EPGF trace - but did not produce clear surface rupture on land or along the seafloor. This talk links the elements of "uncharacteristic" ruptures to their generation at strike-slip restraining bends. Key restraining bend elements for the nucleation of "uncharacteristic" ruptures include a broader and more diffuse area of strain accumulation, the presence of propagating, blind thrust faults commonly parallel with but off axis of the main topographic bend, and broad areas of tectonic uplift above the blind thrust faults. Bend faults tend to remain unrecognized because their recurrence intervals are much longer than the adjacent straight segments of the strike-slip fault.
Experimental Modal Anlysis of Pedestrian Steel Box Girder Bridge%人行钢箱梁桥模态试验研究
申杨凡; 杨斌; 何钰龙; 郭凯强; 续琦峰; 王艳琪; 贾艳敏
2016-01-01
为了了解人行钢桥的自振特性，运用东华测试系统对某人行钢箱梁桥进行模态测试，得到桥梁的动力特性参数，并将试验测得的固有频率、模态振型与 ANSYS 有限元模型中的模态数据进行对比分析。分析结果表明：该人行钢箱梁桥的基频的试验值与理论值的误差为3.8％，行人的附加模态质量是对试验产生误差的原因之一，但对结构基频的影响不大，这也就证明了采用峰值拾取法处理时域数据是合理的，同时结合模态判定准则所得模态数据也是可信的，通过该模态测试系统可有效地测得模态参数（固有频率、模态振型及阻尼比）。%In order to study the natural vibration characteristics of the pedestrian bridge steel,a pedestrian steel box girder bridge’s model experiment is carried out with Donghua Test System to get the dynamic characteristics of bridge,and comparing Natural frequency and mode shapes with modal data a-nalysis of ANSYS finite element model.The analysis results indicate that the error between the fundamen-tal frequency experiment value and the theoretical value of the pedestrian steel box girder bridge is 3.8%.And the additional modal mass of pedestrian is one of the reasons why the experiment have error,it’s in-fluence is little.What proved that using the Peak Picking Method to manipulation time domain data is rea-sonable.At the same time,the modal date that obtained by combining with the modal criterion is credi-ble.That modal parameters(natural frequency,modal vibration mode and damping ratio)can be measured effectively by the modal testing system.
王元清; 刘莉媛; 丁大益; 石永久; 完海鹰
2012-01-01
In order to study the in-plane stability performance of the arc axis both ends hinged curved box-girders, numerical method theory was carried out using finite element software ABAQUS. Two-dimensional curved girder models were established to simulate the in-plane stability of curved box-girders. Influences of different central angles, different slenderness ratio, and different initial geometric imperfections on the in-plane stability performances of the curved box-girder were considered. The differences and laws of the numerical solution and classic theoretical solution of the elastic buckling factor were gained. Effects on the stability factor and regularization slenderness ratio of the initial geometric imperfections were given, and the form of axial load-moment curve was calculated as well. The design formulae for calculating the in-plane stability of arc axis curved box-girders can provide theoretical basis and suggestions for the future design.%为研究两端铰接圆弧轴线箱形截面曲梁的平面内整体稳定性能,采用数值方法对其进行了理论研究,采用ABAQUS有限元软件建立了二维的曲梁模型,模拟曲梁的平面内稳定问题.研究了不同圆心角、不同长细比,以及不同大小的初始几何缺陷对圆弧轴线箱形截面曲梁平面内稳定性能的影响,得到了弹性屈曲系数的数值解与经典理论解的差异和规律,给出了初始几何缺陷对稳定系数和正则化长细比关系曲线的影响,并且计算得到了该形式曲梁的轴力-弯矩关系曲线.提出的圆弧轴线箱形截面曲梁平面内稳定的设计公式可为今后的设计提供理论依据和建议.
Coupled resonator vertical cavity laser
Choquette, K.D.; Chow, W.W.; Hou, H.Q.; Geib, K.M.; Hammons, B.E.
1998-01-01
The monolithic integration of coupled resonators within a vertical cavity laser opens up new possibilities due to the unique ability to tailor the interaction between the cavities. The authors report the first electrically injected coupled resonator vertical-cavity laser diode and demonstrate novel characteristics arising from the cavity coupling, including methods for external modulation of the laser. A coupled mode theory is used model the output modulation of the coupled resonator vertical cavity laser.
Chen, X.; Le, T.; Ewing, D.; Ching, C. Y.
2016-12-01
The mass transfer to turbulent flow through back-to-back pipe bends arranged in a 180° configuration with different lengths of pipe between the bends was measured using a dissolving gypsum test section in water. The measurements were performed for bends with a radius of curvature of 1.5 times the pipe diameter ( D) at a Reynolds numbers of 70,000 and Schmidt number of 1280. The maximum mass transfer in the bends decreased from approximately 1.8 times the mass transfer in the upstream pipe when there was no separation distance between the bends to 1.7 times when there was a 1 D or 5 D length of pipe between the bends. The location of the maximum mass transfer was on the inner sidewall downstream of the second bend when there was no separation distance between the bends. This location changed to the inner wall at the beginning of the second bend when there was a 1 D long pipe between the bends, and to the inner sidewall at the end of the first bend when there was a 5 D long pipe between the bends.
Photomechanical Bending of Azobenzene-Based Photochromic Molecular Fibers
Riku Matsui
2013-03-01
Full Text Available Microfibers composed of azobenzene-based photochromic amorphous molecular materials, namely low molecular-mass photochromic materials with a glass-forming property, could be fabricated. These fibers were found to exhibit mechanical bending motion upon irradiation with a laser beam. In addition, the bending direction could be controlled by altering the polarization direction of the irradiated light without changing the position of the light source or the wavelength of the light. In-situ fluorescence observation of mass transport induced at the surface of the fiber doped with CdSe quantum dots suggested that the bending motions were related with the photoinduced mass transport taking place near the irradiated surface of the fiber.
Flow resistance of ice slurry in bends and elbow pipes
Niezgoda-Żelasko, B.; Żelasko, J.
2014-08-01
The present paper covers the flow of ice slurry made of a 10.6% ethanol solution through small-radius bends and elbow pipes. The paper presents the results of experimental research on the flow resistances of Bingham-fluid ice slurry in bends and elbows. The research, performed for three pipe diameters and a relative bend radius of 1<=D/di<=2, has made it possible to take into consideration the influence of friction resistances as well the of the flow geometry on the total local resistance coefficients. The study attempts to make the local resistance coefficient dependent on the Dean number defined for a generalized Reynolds number according to Metzner-Reade
Platonic scattering cancellation for bending waves in a thin plate
Farhat, Mohamed
2014-04-10
We propose an ultra-thin elastic cloak to control the scattering of bending waves in isotropic heterogeneous thin plates. The cloak design makes use of the scattering cancellation technique applied, for the first time, to the biharmonic operator describing the propagation of bending waves in thin plates. We first analyze scattering from hard and soft cylindrical objects in the quasistatic limit, then we prove that the scattering of bending waves from an object in the near and far-field regions can be suppressed significantly by covering it with a suitably designed coating. Beyond camouflaging, these findings may have potential applications in protection of buildings from earthquakes and isolating structures from vibrations in the motor vehicle industry.
Segmental Bridges under Combined Torsion, Bending and Shear
黄真; 刘西拉
2003-01-01
Segmental bridges with unbonded prestressed tendons have some advantages, such as the weather independence and the corrosion protection of prestressing tendons. This paper analyzed the behavior of a prestressed segmental bridge with unbonded tendons under combined loading of torsion, bending and shear. According to the experiment research, a modified skew bending model was developed to calculate the bearing capacity of segmental bridges subjected to combined bending, shear and torsion. The finite element method was used to investigate the deflection behaviors of such structure, also to check the theoretical model. The theoretical and FEM research resuits were compared favorably with the test results from Technical University of Braunschweig, Germany. Finally, suggestion for the design and construction of segmental bridges with external prestressing was made.
Longitudinal-bending mode micromotor using multilayer piezoelectric actuator.
Yao, K; Koc, B; Uchino, K
2001-07-01
Longitudinal-bending mode ultrasonic motors with a diameter of 3 mm were fabricated using stacked multilayer piezoelectric actuators, which were self-developed from hard lead zirconate titanate (PZT) ceramic. A bending vibration was converted from a longitudinal vibration with a longitudinal-bending coupler. The motors could be bidirectionally operated by changing driving frequency. Their starting and braking torque were analyzed based on the transient velocity response. With a load of moment of inertia 2.5 x 10(-7) kgm2, the motor showed a maximum starting torque of 127.5 microNm. The braking torque proved to be a constant independent on the motor's driving conditions and was roughly equivalent to the maximum starting torque achievable with our micromotors.
Strain localization and damage development in 2060 alloy during bending
Xiao Jin; Bao-qin Fu; Cheng-lu Zhang; Wei Liu
2015-01-01
The microstructure evolution and damage development of the third-generation Al–Li alloy 2060 (T8) were studied using in situ bending tests. Specimens were loaded with a series of punches of different radii, and the microstructure evolution was studied by scanning electron microscopy, electron backscatter diffraction, and digital image correlation (DIC) methods. The evolution of the microscopic fracture strain distribution and microstructure in 2060 alloy during bending was characterized, where the dispersion distribution of precipitates was recorded by backscattered electron imaging and later inputted into a DIC system for strain calculations. The experimental results showed that strain localization in the free surface of bent specimens induced damage to the microstructure. The region of crack initiation lies on the free surface with maximum strain, and the shear crack propagates along the macro-shear band in the early stages of bending. Crack propagation in the later stages was interpreted on the basis of the conventional mechanism of ductile fracture.
Bend-twist coupling potential of wind turbine blades
Fedorov, Vladimir; Berggreen, Christian
2014-01-01
In the present study an evaluation of the potential for bend-twist coupling effects in wind turbine blades is addressed. A method for evaluation of the coupling magnitude based on the results of finite element modeling and full-field displacement measurements obtained by experiments is developed...... and tested on small-scale coupled composite beams. In the proposed method the coupling coefficient for a generic beam is introduced based on the Euler-Bernoulli beam formulation. By applying the developed method for analysis of a commercial wind turbine blade structure it is demonstrated that a bend......-twist coupling magnitude of up to 0.2 is feasible to achieve in the baseline blade structure made of glass-fiber reinforced plastics. Further, by substituting the glass-fibers with carbon-fibers the coupling effect can be increased to 0.4. Additionally, the effect of introduction of bend-twist coupling...
Demonstration of acoustic waveguiding and tight bending in phononic crystals
Ghasemi Baboly, M.; Raza, A.; Brady, J.; Reinke, C. M.; Leseman, Z. C.; El-Kady, I.
2016-10-01
The systematic design, fabrication, and characterization of an isolated, single-mode, 90° bend phononic crystal (PnC) waveguide are presented. A PnC consisting of a 2D square array of circular air holes in an aluminum substrate is used, and waveguides are created by introducing a line defect in the PnC lattice. A high transmission coefficient is observed (-1 dB) for the straight sections of the waveguide, and an overall 2.3 dB transmission loss is observed (a transmission coefficient of 76%) for the 90° bend. Further optimization of the structure may yield higher transmission efficiencies. This manuscript shows the complete design process for an engineered 90° bend PnC waveguide from inception to experimental demonstration.
Elastocapillary instability under partial wetting conditions: bending versus buckling
Andreotti, Bruno; Das, Siddhartha; Snoeijer, Jacco H
2011-01-01
The elastocapillary instability of a flexible plate plunged in a liquid bath is analysed theoretically. We show that the plate can bend due to two separate destabilizing mechanisms, when the liquid is partially wetting the solid. For contact angles $\\theta_e > \\pi/2$, the capillary forces acting tangential to the surface are compressing the plate and can induce a classical buckling instability. However, a second mechanism appears due to capillary forces normal to surface. These induce a destabilizing torque that tends to bend the plate for any value of the contact angle $\\theta_e > 0$. We denote these mechanisms as "buckling" and "bending" respectively and identify the two corresponding dimensionless parameters that govern the elastocapillary stability. The onset of instability is determined analytically and the different bifurcation scenarios are worked out for experimentally relevant conditions.
Trade Liberalisation and Vertical Integration
Bache, Peter Arendorf; Laugesen, Anders
-good producers face decisions on exporting, vertical integration of intermediate-input production, and whether the intermediate-input production should be offshored to a low-wage country. We find that the fractions of final-good producers that pursue either vertical integration, offshoring, or exporting are all...... increasing when intermediate-input or final-goods trade is liberalised and when the fixed cost of vertical integration is reduced. At the same time, one observes firms that shift away from either vertical integration, offshoring, or exporting. Further, we provide guidance for testing the open...
Vertical allometry: fact or fiction?
Mahmood, Iftekhar; Boxenbaum, Harold
2014-04-01
In pharmacokinetics, vertical allometry is referred to the clearance of a drug when the predicted human clearance is substantially higher than the observed human clearance. Vertical allometry was initially reported for diazepam based on a 33-fold higher human predicted clearance than the observed human clearance. In recent years, it has been found that many other drugs besides diazepam, can be classified as drugs which exhibit vertical allometry. Over the years, many questions regarding vertical allometry have been raised. For example, (1) How to define and identify the vertical allometry? (2) How much difference should be between predicted and observed human clearance values before a drug could be declared 'a drug which follows vertical allometry'? (3) If somehow one can identify vertical allometry from animal data, how this information can be used for reasonably accurate prediction of clearance in humans? This report attempts to answer the aforementioned questions. The concept of vertical allometry at this time remains complex and obscure but with more extensive works one can have better understanding of 'vertical allometry'. Published by Elsevier Inc.
Modulated liquid-crystal phases induced by polarity: Twist-bend, splay-bend, and blue phases
Selinger, Jonathan; Shamid, Shaikh; Allender, David
2014-03-01
Nematic liquid crystals exhibit flexoelectric couplings between polar order and gradients in the director field. When the couplings become strong enough, the uniform nematic phase can become unstable to the formation of a modulated polar phase. The question is then: What is the structure of the modulated polar phase? Classic work by Meyer and further studies by Dozov predicted two possible structures, known as twist-bend and splay-bend. One of these predictions, the twist-bend phase, has recently been identified in experiments on bent-core liquid crystals. Here, we investigate modulated polar phases through a combination of Landau theory and lattice simulations. We find a range of possibilities, including the twist-bend and splay-bend phases as well as polar blue phases, with 2D or 3D modulations of the director field and the polar order. We compare these polar blue phases with chiral blue phases, and discuss opportunities for observing them experimentally. Supported by NSF DMR-1106014.
Sasidharan, Sumesh; Arunachalam, Veerappan; Subramaniam, Shanmugam [Dept. of Mechanical Engineering, National Institute of Technology, Tiruchirappalli (India)
2017-02-15
Finite-element analysis based on elastic-perfectly plastic material was conducted to examine the influence of structural deformations on collapse loads of circumferential through-wall critically cracked 90 .deg. pipe bends undergoing in-plane closing bending and internal pressure. The critical crack is defined for a through-wall circumferential crack at the extrados with a subtended angle below which there is no weakening effect on collapse moment of elbows subjected to in-plane closing bending. Elliptical and semioval cross sections were postulated at the bend regions and compared. Twice-elastic-slope method was utilized to obtain the collapse loads. Structural deformations, namely, ovality and thinning, were each varied from 0% to 20% in steps of 5% and the normalized internal pressure was varied from 0.2 to 0.6. Results indicate that elliptic cross sections were suitable for pipe ratios 5 and 10, whereas for pipe ratio 20, semioval cross sections gave satisfactory solutions. The effect of ovality on collapse loads is significant, although it cancelled out at a certain value of applied internal pressure. Thinning had a negligible effect on collapse loads of bends with crack geometries considered.
Bending of the looping heart: differential growth revisited.
Shi, Yunfei; Yao, Jiang; Xu, Gang; Taber, Larry A
2014-08-01
In the early embryo, the primitive heart tube (HT) undergoes the morphogenetic process of c-looping as it bends and twists into a c-shaped tube. Despite intensive study for nearly a century, the physical forces that drive looping remain poorly understood. This is especially true for the bending component, which is the focus of this paper. For decades, experimental measurements of mitotic rates had seemingly eliminated differential growth as the cause of HT bending, as it has commonly been thought that the heart grows almost exclusively via hyperplasia before birth and hypertrophy after birth. Recently published data, however, suggests that hypertrophic growth may play a role in looping. To test this idea, we developed finite-element models that include regionally measured changes in myocardial volume over the HT. First, models based on idealized cylindrical geometry were used to simulate the bending process in isolated hearts, which bend without the complicating effects of external loads. With the number of free parameters in the model reduced to the extent possible, stress and strain distributions were compared to those measured in embryonic chick hearts that were isolated and cultured for 24 h. The results show that differential growth alone yields results that agree reasonably well with the trends in our data, but adding active changes in myocardial cell shape provides closer quantitative agreement with stress measurements. Next, the estimated parameters were extrapolated to a model based on realistic 3D geometry reconstructed from images of an actual chick heart. This model yields similar results and captures quite well the basic morphology of the looped heart. Overall, our study suggests that differential hypertrophic growth in the myocardium (MY) is the primary cause of the bending component of c-looping, with other mechanisms possibly playing lesser roles.
李小珍; 张迅; 刘全民; 张志俊; 李亚东
2013-01-01
以32 m单线和双线单室混凝土简支箱梁为对象,通过噪声试验、结构有限元和声学有限元分析,研究箱梁结构噪声的声辐射特性、峰值频率产生的原因及评价方法.结果表明:列车通过桥梁时,离箱梁表面较远处的噪声级起伏不大,可采用稳态算法简化分析；混凝土箱梁的结构噪声主要分布在250 Hz以下,且随频率的增加而迅速衰减,因此理论预测时可将250 Hz作为截止频率；单线和双线箱梁的2个噪声峰值频率分别为63和160 Hz,以及50和315 Hz,二者均在第1个峰值频率处达到最大声压级,且此峰值频率处的噪声具有明显的有调性；不同箱室尺寸箱梁的结构噪声声辐射差异较大,车速并不是噪声的第一决定因素；混凝土箱梁结构噪声的峰值频率出现在声辐射效率和振动响应均较大处,因此应避免结构振动模态和空腔声学模态重合而导致空腔共鸣引起的噪声被放大；建议修订铁路噪声相关规范时,考虑混凝土箱梁低频结构噪声的危害.%Based on the study objects of single-and double-track simply-supported concrete box-girders with only one cell and a span of 32 m,this paper investigated the sound radiation characteristics of structure-borne noise,reasons leading to peak frequency and evaluation methods by field measurements,structural and acoustical finite element analysis.The results show that:during a train runs across bridge,the noise far away from the box-girder surface fluctuates slightly,which means that simplified steady-state acoustic analysis is feasible; structure-borne noise from concrete box-girder dominates in the frequency lower than 250 Hz and decreases rapidly with increasing frequency,accordingly,250 Hz can be regarded as the upper limiting frequency for theoretical prediction; the two frequencies of peak noise of single-and doubletrack box-girder are 63 and 160 Hz,as well as 50 and 315 Hz,respectively,and the noise reaches
杨勇; 周现伟; 薛建阳; 霍旭东
2012-01-01
In order to study the fatigue behaviour of the steel plate-concrete composite-deck composite girders under the fatigue load, constant-amplitude fatigue tests of six specimens of the steel plate-concrete composite-deck composite beam were carried out and static loading experiments of two specimens were conducted. The influence of the main factors including the upper and lower limits of fatigue load and the stress amplitude on the failure modes and the fatigue damage extent of composite girders under fatigue load were focused on. The dynamic deflection, strains of concrete and steel plates, strains of steel beam, residual deflection and residual bearing capacity were measured and analyzed. From the tests results, the fatigue life-spans of the composite girders specimens were directly related with their stress amplitudes, but the upper and lower limits of fatigue load had little effect. With regard to the fatigue failure modes of the composite girders specimens, positive moment composite girders were all failed due to collapse of the steel beam and crush of concrete of compressive zone, but not to the negative moment of composite girders, as a result of steel-beam buckling under static tests after fatigue tests. This paper were very helpful for this type of compsite girders design.%为研究带钢板-混凝土组合桥面板的组合梁在疲劳荷载下的受力性能，对2个试件进行静力试验研究，并对6个试件进行等幅疲劳试验研究。疲劳试验试件按承受正弯矩和承受负弯矩两组类型试件分别考虑，在各组试件中均主要考察疲劳荷载上、下限值及疲劳荷载幅值等因素对带钢板-混凝土组合桥面板组合梁的疲劳破坏模式及疲劳累积损伤的影响。疲劳试验过程中对组合梁试件在各主要循环加载次数下的动挠度、残余挠度、混凝土应变、底部钢板应变、试件钢梁应变及试件受弯刚度进行试验测量和分析。疲劳试验结果表明：正
Proteomic Analysis of Fruit Bending in Cucumber (Cucumis sativus L.)
WANG Li-li; ZHANG Peng; QIN Zhi-wei; ZHOU Xiu-yan
2014-01-01
In cucumber, fruit shape is an important quality criterion, and fruit bending is known to limit growth, yield, and taste. To investigate the post-transcriptional changes that regulate fruit bending and to better understand the underlying molecular mechanisms, we generated a proteomic proifle of the abdomen and back of cucumber bending fruit. Two-dimensional gel electrophoresis (2-DE) allowed the detection of approximately 900 distinct protein spots in each gel, 32 of which were differentially expressed in the abdomen and back of bending cucumber fruit. Ten of the differentially expressed proteins were analyzed using matrix-assisted laser ionization time of lfight mass spectrometry (MALDI-TOF/MS). A search of primary databases showed that the identiifed proteins are involved in various metabolic processes and cellular responses, including photosynthesis metabolism, energy metabolism, defense and stress response, and regulation. The identiifed proteins included large subunits of ribulose-1,5-bisphosphate carboxylase/oxygenase, which are involved in photosynthesis and photorespiratory metabolism, and isocitrate dehydrogenase, which is involved in the tricarboxylic acid cycle. It is possible that imbalances in catabolic and anabolic processes directly affect the bending of cucumber fruit. The predicted function of the cobalamin-independent methionine synthase isozyme is closely related to ethylene biosynthesis; fruit bending may be regulated by ethylene, or by ethylene signaling crosstalk during fruit development. The 14-3-3 protein is usually considered to be a regulation-related protein, which plays a role in regulating cell hyperplasia, cell differentiation during growth, and apoptosis during senescence. Involvement of guanosine triphosphate (GTP)-binding proteins in signal transmission is known to regulate the development of cells in cucumber fruits and to play a role in fruit shape variation. Patterns of protein expression showed high repeatability. We hypothesize
Enhanced resolution of long-period grating bend sensor
Glavind, Lars; Gao, S; Cook, K
2013-01-01
We present an optical fiber bend sensor with enhanced resolution based on the principle of a Mach-Zehnder interferometer in transmission. The sensor is based on two identical Long-Period Gratings separated by approximately 100 mm in a D-shaped single-mode optical fiber. The sensor provides a narr...... resonance bandwidth compared to a typical resonance from a Long-Period Grating. The sensor was recoated with low refractive index polyimide and embedded on a fiber-glass base plate before it was characterized as a bending sensor....
Bending Mechanical Behavior of Polyester Matrix Reinforced with Fique Fiber
Altoé, Giulio Rodrigues; Netto, Pedro Amoy; Barcelos, Mariana; Gomes, André; Margem, Frederico Muylaert; Monteiro, Sergio Neves
Environmentally correct composites, made from natural fibers, are among the most investigated and applied today. In this paper, we investigate the mechanical behavior of polyester matrix composites reinforced with continuous fique fibers, through bending tensile tests. Specimens containing 0, 10, 20 and 30% in volume of fique fiber were aligned along the entire length of a mold to create plates of these composites, those plates were cut following the ASTM standard to obtained bending tests specimens. The test was conducted in a Instron Machine and the fractured specimens were analyzed by SEM, the results showed the increase in the materials tensile properties with the increase of fiber amount.
Quasimolecular Dynamic Simulation for Bending Fracture of Laminar Composite Materials
无
2001-01-01
Recently, quasimolecular dynamics has been successfully used to simulate the deformation characteristics of actual size solid materials. In quasimolecular dynamics, which is an attempt to bridge the gap between atomistic and continuum simulations, molecules are aggregated into large units, called quasimolecules, to evaluate large scale material behavior. In this paper, a 2-dimensional numerical simulation using quasimolecular dynamics was performed to investigate laminar composite material fractures and crack propagation behavior in the uniform bending of laminar composite materials. It was verified that under bending deformation laminar composite materials deform quite differently from homogeneous materials
Elastostatic bending of a bimaterial plate with a circular interface
Ogbonna, Nkem
2015-08-01
The elastostatic bending of an arbitrarily loaded bimaterial plate with a circular interface is analysed. It is shown that the deflections in the composite solid are directly related to the deflection in the corresponding homogeneous material by integral and differential operators. It is further shown that, by a simple transformation of elastic constants, the Airy stress function induced in the composite by a stretching singularity can be deduced from the deflection induced by a bending singularity. This result is significant for reduction of mathematical labour and for systematic construction of solutions for more complex structures with circular geometry.
Effects of rim thickness on spur gear bending stress
Bibel, G. D.; Reddy, S. K.; Savage, M.; Handschuh, R. F.
1991-01-01
Thin rim gears find application in high-power, light-weight aircraft transmissions. Bending stresses in thin rim spur gear tooth fillets and root areas differ from the stresses in solid gears due to rim deformations. Rim thickness is a significant design parameter for these gears. To study this parameter, a finite element analysis was conducted on a segment of a thin rim gear. The rim thickness was varied and the location and magnitude of the maximum bending stresses reported. Design limits are discussed and compared with the results of other researchers.
Origin of bending in uncoated microcantilever - Surface topography?
Lakshmoji, K.; Prabakar, K.; Tripura Sundari, S., E-mail: sundari@igcar.gov.in; Jayapandian, J.; Tyagi, A. K.; Sundar, C. S. [Materials Science Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603102 (India)
2014-01-27
We provide direct experimental evidence to show that difference in surface topography on opposite sides of an uncoated microcantilever induces bending, upon exposure to water molecules. Examination on opposite sides of the microcantilever by atomic force microscopy reveals the presence of localized surface features on one side, which renders the induced stress non-uniform. Further, the root mean square inclination angle characterizing the surface topography shows a difference of 73° between the opposite sides. The absence of deflection in another uncoated microcantilever having similar surface topography confirms that in former microcantilever bending is indeed induced by differences in surface topography.
Flagella bending affects macroscopic properties of bacterial suspensions
Potomkin, M.; Tournus, M.; Berlyand, L. V.; Aranson, I. S.
2017-05-01
To survive in harsh conditions, motile bacteria swim in complex environments and respond to the surrounding flow. Here, we develop a mathematical model describing how flagella bending affects macroscopic properties of bacterial suspensions. First, we show how the flagella bending contributes to the decrease in the effective viscosity observed in dilute suspension. Our results do not impose tumbling (random reorientation) as was previously done to explain the viscosity reduction. Second, we demonstrate how a bacterium escapes from wall entrapment due to the self-induced buckling of flagella. Our results shed light on the role of flexible bacterial flagella in interactions of bacteria with shear flow and walls or obstacles.
Koshelev, Irina; Huang, Rong; Graber, Timothy; Meron, Mati; Muir, J. Lewis; Lavender, William; Battaile, Kevin; Mulichak, Anne M.; Keefe, Lisa J.; (IIT); (UC)
2009-09-02
The IMCA-CAT bending-magnet beamline was upgraded with a collimating mirror in order to achieve the energy resolution required to conduct high-quality multi- and single-wavelength anomalous diffraction (MAD/SAD) experiments without sacrificing beamline flux throughput. Following the upgrade, the bending-magnet beamline achieves a flux of 8 x 10{sup 11} photons s{sup -1} at 1 {angstrom} wavelength, at a beamline aperture of 1.5 mrad (horizontal) x 86 {mu}rad (vertical), with energy resolution (limited mostly by the intrinsic resolution of the monochromator optics) {delta}E/E = 1.5 x 10{sup -4} (at 10 kV). The beamline operates in a dynamic range of 7.5-17.5 keV and delivers to the sample focused beam of size (FWHM) 240 {micro}m (horizontally) x 160 {micro}m (vertically). The performance of the 17-BM beamline optics and its deviation from ideally shaped optics is evaluated in the context of the requirements imposed by the needs of protein crystallography experiments. An assessment of flux losses is given in relation to the (geometric) properties of major beamline components.
Koshelev, Irina; Huang, Rong; Graber, Timothy; Meron, Mati; Muir, J Lewis; Lavender, William; Battaile, Kevin; Mulichak, Anne M; Keefe, Lisa J
2009-09-01
The IMCA-CAT bending-magnet beamline was upgraded with a collimating mirror in order to achieve the energy resolution required to conduct high-quality multi- and single-wavelength anomalous diffraction (MAD/SAD) experiments without sacrificing beamline flux throughput. Following the upgrade, the bending-magnet beamline achieves a flux of 8 x 10(11) photons s(-1) at 1 A wavelength, at a beamline aperture of 1.5 mrad (horizontal) x 86 microrad (vertical), with energy resolution (limited mostly by the intrinsic resolution of the monochromator optics) deltaE/E = 1.5 x 10(-4) (at 10 kV). The beamline operates in a dynamic range of 7.5-17.5 keV and delivers to the sample focused beam of size (FWHM) 240 microm (horizontally) x 160 microm (vertically). The performance of the 17-BM beamline optics and its deviation from ideally shaped optics is evaluated in the context of the requirements imposed by the needs of protein crystallography experiments. An assessment of flux losses is given in relation to the (geometric) properties of major beamline components.
Robert W. Fausett
2014-01-01
Full Text Available As part of an investigation on the performance of integral abutment bridges, a single-span, integral abutment, prestressed concrete girder bridge near Perry, Utah was instrumented for live-load testing. The live-load test included driving trucks at 2.24 m/s (5 mph along predetermined load paths and measuring the corresponding strain and deflection. The measured data was used to validate a finite-element model (FEM of the bridge. The model showed that the integral abutments were behaving as 94% of a fixed-fixed support. Live-load distribution factors were obtained using this validated model and compared to those calculated in accordance to recommended procedures provided in the AASHTO LRFD Bridge Design Specifications (2010. The results indicated that if the bridge was considered simply supported, the AASHTO LRFD Specification distribution factors were conservative (in comparison to the FEM results. These conservative distribution factors, along with the initial simply supported design assumption resulted in a very conservative bridge design. In addition, a parametric study was conducted by modifying various bridge properties of the validated bridge model, one at a time, in order to investigate the influence that individual changes in span length, deck thickness, edge distance, skew, and fixity had on live-load distribution. The results showed that the bridge properties with the largest influence on bridge live-load distribution were fixity, skew, and changes in edge distance.
The Layout Optimization of Main and Secondary Girder Floor System%主次梁楼盖体系的布置优化
楼世雄; 朱杰江; 张磊
2016-01-01
In this paper, the layout of main and secondary girder roof system has been optimized by the composition of the floor optimization program.The structure model and internal force analysis are made by calling ETABS software, the optimization for the secondary beam number, the section size of main and secondary beam and the floor thickness is made by LINGO software, which are both under the Visual Basic (.NET 4.0) plat-form, and through this program, the optimal floor layout is achieved.%编制楼盖优化程序，对主次梁楼盖体系进行布置优化。在Visual Basic （．NET 4．0）平台下调用ETABS进行建模和内力分析，调用LINGO优化求解器对次梁数量、主次梁截面尺寸以及楼板厚度进行优化，得到楼盖最优布置。
Application of TMD in Large Span Steel Box Girder Footbridge%TMD在大跨径钢箱梁人行桥上的应用分析
苑翔
2013-01-01
This paper introduces the Tuned Mass Damper (TMD) composition and operation principle of the structure, comparison of advantages and disadvantages of TMD and other control of steel box girder footbridge vibration methods, and combined with the Mianyang No.1 bridge footbridge of Sichuan Province as an example, through the use of text and graph-table combination method, describes vividly the practical application of TMD in large span footbridge.% 介绍了质量调谐阻尼器(TMD)的结构组成以及工作原理，比较了TMD与其它控制钢箱梁人行桥振动方法的优缺点，并结合四川省绵阳市一号桥人行桥为工程实例，通过采用文字与图、表相结合的方式，形象地阐述了TMD在大跨径人行桥中的实际应用。
斜拉桥主梁应变监测分析%Girder Strain Analysis of a Cable-stayed Bridge
邵平
2012-01-01
The health monitoring system of the bridge maintenance management is an important means to ensure the safety operation. To grasp the working condition, strain analysis is necessary. With practical engineering of a bridge in Xinmi, appling finite-element analysis software of MIDAS/Civil to establish the space model, we analysis the stress of the girder in the construction stage and compare the academic value and the practical value. The conclusion will provide a reference to the same bridges.%基于健康监测系统的桥梁养护管理是保证其安全运营的重要手段.而对监测数据进行分析以把握结构的工作状态是一个必须环节.结合新密某桥梁的工程实践,运用有限元软件建立主梁有限元空间模型,模拟分析施工阶段主梁应力,并对应力理论值和实测值进行对比与分析.结论将为同类桥梁应力监测提供参考.
Bending-induced mode non-degeneracy and coupling in chalcogenide negative curvature fibers.
Wei, Chengli; Menyuk, Curtis R; Hu, Jonathan
2016-05-30
We study bend loss in chalcogenide negative curvature fibers with different polarizations, different tube wall thicknesses, and different bend directions relative to the mode polarization. The coupling between the core mode and tube modes induces bend loss peaks in the two non-degenerate modes at the same bend radius. There is as much as a factor of 28 difference between the losses of the two polarization modes. The fiber with a larger tube wall thickness, corresponding to a smaller inner tube diameter, can sustain a smaller bend radius. The bend loss is sensitive to the bend direction when coupling occurs between the core mode and tube modes. A bend loss of 0.2 dB/m at a bend radius of 16 cm, corresponding to 0.2 dB/turn, can be achieved in a chalcogenide negative curvature fiber.
The School Library Vertical File.
Smallwood, Carol
1990-01-01
Discusses the maintenance of vertical files in the school library. Topics covered include circulation, weeding, using materials for special displays, acquiring materials, policies on advertising and controversial issues, cross-references, subject headings, introducing students to vertical files, beginning a collection, and preservation. (MES)
Thin-walled aluminum alloy tube NC precision bending based on finite element simulation
GU Rui-jie; YANG He; ZHAN Mei; LI Heng
2006-01-01
Elongation and springback are the bottleneck problems of thin-walled aluminum alloy tube NC precision bending. So thin-walled aluminum alloy tube NC precision bending based on finite element simulation is put forward. The finite element model of thin-walled aluminum alloy tube NC bending is established based on the DYNAFORM platform. The process of thin-walled aluminum alloy tube NC precision bending is simulated with the model and the elongation and springback of tube bending can be is put forward and the computing equations of bending angle, bending radius, blanking length and initial bending section based on elongation and springback angle are derived. The bending angle, bending radius, blanking length and initial bending section of tube bending can be gained with these equations based on the elongation and springback angle from the simulation. The study can be used to control the quality of thin-walled aluminum alloy tube NC bending so that precision bending without redundance can be realized.
汤任基; 汤昕燕
2001-01-01
Using the single crack solution and the regular solution of plane harmonic function, the problem of Saint-Venant bending of a cracked cylinder by a transverse force was reduced to solving two sets of integral equations and its general solution was then obtained. Based on the obtained solution, a method to calculate the bending center and the stress intensity factors of the cracked cylinger whose cross-section is not thin-walled, but of small torsion rigidity is proposed. Some numerical examples are given.
Electrical Emissions from Concrete under Three-point Bending Tests
LIU Qingping; SUN Mingqing; LI Zhuoqiu; LI Guoqiang
2005-01-01
Electrical emission(EM) signals, which are generated from the concrete specimens under three-point bending tests, were conducted. It is shown that electrical emission phenomena are related to cracking of the specimens, cohesive failure, contact-separation etc. The simultaneous appearance of electric emission signals and visible cracks during the flexure loading of beams was also observed.
Secondary flow in sharp open-channel bends
Blanckaert, K.; De Vriend, H.J.
2004-01-01
Secondary currents are a characteristic feature of flow in open-channel bends. Besides the classical helical motion (centre-region cell), a weaker and smaller counter-rotating circulation cell (outer-bank cell) is often observed near the outer bank, which is believed to play an important role in ban
Photoacoustic elastic bending in thin film—Substrate system
Todorović, D. M., E-mail: dmtodor@imsi.bg.ac.rs [Institute for Multidisciplinary Research, University of Belgrade, P.O. Box 33, 11030 Belgrade (Serbia); Rabasović, M. D.; Markushev, D. D. [Institute of Physics, University of Belgrade, Pregrevica 118, 11080 Belgrade-Zemun (Serbia)
2013-12-07
Theoretical model for optically excited two-layer elastic plate, which includes plasmaelastic, thermoelastic, and thermodiffusion mechanisms, is given in order to study the dependence of the photoacoustic (PA) elastic bending signal on the optical, thermal, and elastic properties of thin film—substrate system. Thin film-semiconductor sample (in our case Silicon) is modeled by simultaneous analysis of the plasma, thermal, and elastic wave equations. Multireflection effects in thin film are included in theoretical model and analyzed. Relations for the amplitude and phase of electronic and thermal elastic bending in the optically excited two-layer mechanically-supported circular plate are derived. Theoretical analysis of the thermodiffusion, plasmaelastic, and thermoelastic effects in a sample-gas-microphone photoacoustic detection configuration is given. Two normalization procedures of the photoacoustic elastic bending signal in function of the modulation frequency of the optical excitation are established. Given theoretical model can be used for various photoacoustic detection configurations, for example, in the study of optical, thermal, and elastic properties of the dielectric-semiconductor or metal-semiconductor structure, etc., Theoretical analysis shows that it is possible to develop new noncontact and nondestructive experimental method—PA elastic bending method for thin film study, with possibility to obtain the optical, thermal, and elastic parameters of the film thinner than 1 μm.
A Novel Rotary Piezoelectric Motor Using First Bending Hybrid Transducers
Yingxiang Liu
2015-08-01
Full Text Available We report a novel rotary piezoelectric motor using bending transducers in this work. Three transducers are used to drive a disk-shaped rotor together by the elliptical movements of their driving tips; these motions are produced by the hybrid of two first bending vibration modes. The proposed piezoelectric transducer has a simple structure as it only contains an aluminum alloy beam and four pieces of PZT plates. Symmetrical structure is the only necessary condition in the design process as it will ensure the resonance frequencies of the two orthogonal first bending modes are equal. Transducers with first bending resonance frequency of about 53 kHz were fabricated and assembled into a rotary motor. The proposed motor exhibits good performance on speed and torque control. Under a working frequency of 53.2 kHz, the maximum no-load speed and the maximum torque of the prototype are tested to be 53.3 rpm and of 27 mN·m.
Optimization of bandwidth in 60^o photonic crystal waveguide bends
Xing, P. F.; Borel, Peter Ingo; Frandsen, Lars Hagedorn;
2005-01-01
A systematic scheme utilizing 2D and 3D finite-difference time-domain calculations to design 60^o photonic crystal waveguide bends is presented. The method results in an improved transmission bandwidth from 70 to 160 nm in 2D simulations, and from 50 to 100 nm in 3D simulations. The design...
Tidal bending of glaciers: a linear viscoelastic approach
Reeh, Niels; Christensen, Erik Lintz; Mayer, Christoph
2003-01-01
glaciers are in the range 0.9-3 GPa. It has therefore been suggested that the elastic-beam model with a single value of E approximate to 1 GPa adequately describes tidal bending of glaciers.In contrast, laboratory experiments with ice give E =93 GPa, i.e. 3-10 times higher than the glacier-derived values...
Varmebesparelser ved løbende bygningsrenovering frem til 2050
Wittchen, Kim Bjarne; Kragh, Jesper
Som noget relativt nyt er der i bygningsreglementet indført krav til efterisolering af bygningsdele i forbindelse med den løbende renovering, som fx udskiftning af en tagbelægning. Hvor meget påvirker det netto-varmeforbruget frem til 2050, hvis der fortsættes med de gældende regler, og hvilken e...
Water-rich bending faults at the Middle America Trench
Naif, Samer; Key, Kerry; Constable, Steven; Evans, Rob L.
2015-09-01
The portion of the Central American margin that encompasses Nicaragua is considered to represent an end-member system where multiple lines of evidence point to a substantial flux of subducted fluids. The seafloor spreading fabric of the incoming Cocos plate is oriented parallel to the trench such that flexural bending at the outer rise optimally reactivates a dense network of normal faults that extend several kilometers into the upper mantle. Bending faults are thought to provide fluid pathways that lead to serpentinization of the upper mantle. While geophysical anomalies detected beneath the outer rise have been interpreted as broad crustal and upper mantle hydration, no observational evidence exists to confirm that bending faults behave as fluid pathways. Here we use seafloor electromagnetic data collected across the Middle America Trench (MAT) offshore of Nicaragua to create a comprehensive electrical resistivity image that illuminates the infiltration of seawater along bending faults. We quantify porosity from the resistivity with Archie's law and find that our estimates for the abyssal plain oceanic crust are in good agreement with independent observations. As the Cocos crust traverses the outer rise, the porosity of the dikes and gabbros progressively increase from 2.7% and 0.7% to 4.8% and 1.7%, peaking within 20 km of the trench axis. We conclude that the intrusive crust subducts twice as much pore water as previously thought, significantly raising the flux of fluid to the seismogenic zone and the mantle wedge.
Finite element analysis of damage in pipeline bends
Swart, A.E.; Karamanos, S.A.; Scarpas, A.; Blaauwendraad, J.
2010-01-01
The present paper describes a numerical formulation for the analysis of damage in steel pipeline bends. In particular, the numerical implementation of Gurson plasticity model is described in the framework of a special element, referred to as “tube element”. This is a three-node element, which simula
Predicting bending stiffness of randomly oriented hybrid panels
Laura Moya; William T.Y. Tze; Jerrold E. Winandy
2010-01-01
This study was conducted to develop a simple model to predict the bending modulus of elasticity (MOE) of randomly oriented hybrid panels. The modeling process involved three modules: the behavior of a single layer was computed by applying micromechanics equations, layer properties were adjusted for densification effects, and the entire panel was modeled as a three-...
A Second Look at Brian Simon's "Bending the Rules"
Cox, Sue
2016-01-01
In this article the author revisits an important book: Brian Simon's "Bending the Rules: the Baker reform of education." Written by a key figure in the history of the journal FORUM as well as in the history of education, Simon's book documented the features of the Education Reform Bill of 1987 (the precursor to the Education Reform Act…
Band bending and electrical transport at chemically modified silicon surfaces
Lopinski, Greg; Ward, Tim; Hul'Ko, Oleksa; Boukherroub, Rabah
2002-03-01
High resolution electron energy loss spectroscopy (HREELS) and electrical transport measurements have been used to investigate how various chemical modifications give rise to band bending and alter the conductivity of Si(111) surfaces. HREELS is a sensitive probe of band bending through observations of the low frequency free carrier plasmon mode. For hydrogen terminated surfaces, prepared by the standard etch in ammonium flouride, HREELS measurements on both n and n+ substrates are consistent with nearly flat bands. Chlorination of these surfaces results in substantial upward band bending due to the strong electron withdrawing nature of the chlorine, driving the surface into inversion. The presence of this inversion layer on high resistivity n-type samples is observed through a substantial enhancement of the surface conductivity (relative to the H-terminated surface), as well as through broadening of the quasi-elastic peak in the HREELS measurements. We have also begun to examine organically modified silicon surfaces, prepared by various wet chemical reactions with the H-terminated surface. Decyl modified Si(111) surfaces are seen to exhibit a small degree of band bending, attributed to extrinsic defect states cause by a small degree of oxidation accompanying the modification reaction. The prospects of using conductivity as an in-situ monitor of the rate of these reactions will be discussed.
The Clinch Bend Regional Industrial Site and economic development opportunities
NONE
1995-12-31
This effort focuses initially on the Clinch Bend site. Other sites and developable tracts of land are identified with the assistance of communities in proximity to Oak Ridge, the State of Tennessee, and others, and compared with the projected site requirements for large industrial facilities.
A COMBINED HYBRID FINITE ELEMENT METHOD FOR PLATE BENDING PROBLEMS
Tian-xiao Zhou; Xiao-ping Xie
2003-01-01
In this paper, a combined hybrid method is applied to finite element discretization ofplate bending problems. It is shown that the resultant schemes are stabilized, i.e., theconvergence of the schemes is independent of inf-sup conditions and any other patch test.Based on this, two new series of plate elements are proposed.