Grouted Pile and Its Bearing Capacity
无
2000-01-01
The grouting method applied in bored pile is an improvement to the conventional bored pile. Load tests have proved that grouting under the bored pile tip is an effective method to enhance the bearing capacity of the pile and to reduce the pile settlement. In this paper, the grouting technology is described and pile-load test results are discussed. In order to put the grouting method into design practice, the authors analyze the working mechanism of soil compaction. And, based on the theory of cavities expansion in soil mass, approximate formulae are proposed for estimating the bearing capacity of the grouted pile. The theoretical prediction agrees well with the load test results.
Load-Bearing Capacity of Roof Trusses
Sørensen, John Dalsgaard; Damkilde, Lars; Munch-Andersen, J.
2004-01-01
structural systems such as roof trusses are established and statistical characteristics of the load bearing capacity are determined. The results show that there is a significant increase in the characteristic (nominal) value and a reduction in the coefficient of variation (COV) for typical loads such as...
Bearing capacity of mixed soil model
Mehdi Khodashenas Pelkoo
2009-01-01
Full Text Available The main objective of this research is improvement of red soil with addition of construction materials. This method could provide a scientific way to create a soil foundation with sufficient stability against geo-technical problems or instabilities. Laboratory tests have been conducted to assess the behavior of red soil, when amended with different types of gravels, soils and sand under compacted conditions with Optimum Moisture Content (OMC. Safe bearing capacity of all models, have been calculated to identify best and worst soil mixed model.
Load bearing capacity of degraded nuclear piping
Integrity assessment of piping components with postulated cracks is important for safe and reliable operation of power plants. While various equations and methods are available for prediction of the load bearing capacity of pipes and elbows, it is very important to choose the correct equation and method whose predictions are consistent, safe but not too conservative with respect to the experimental results. Towards this goal, a comprehensive Component Integrity Assessment Program was initiated under a joint MPA-BARC collaborative program where a large number of austenitic and ferritic pipes and elbows of nominal diameter of 50-400 mm with various crack configurations and sizes were tested. These test results along with results of previous tests were analysed with various available limit load equations present and also with the R6 method. Based on the comparison of these test results and predictions, the correct equation and method are recommended to reliably predict the load bearing capacity of flawed pipes and elbows reliably. (authors)
Lightweight Aggregate Concrete Beams. Load-bearing Capacity
Larsen, Henning; Goltermann, Per; Ingholt, N.U.
1997-01-01
This paper deals with the load-bearing capacity of reinforced beams made of lightweight aggregate concrete with open structure and documents formulas for the moment capacity as well as the shear force capacity.......This paper deals with the load-bearing capacity of reinforced beams made of lightweight aggregate concrete with open structure and documents formulas for the moment capacity as well as the shear force capacity....
Lightweight Aggregate Concrete Components. Load-bearing Capacity
Larsen, Henning; Ingholt, N.U.; Goltermann, Per
1996-01-01
The project presented here deals with the load-bearing capacity of reinforced beams made of lightweight aggregate concrete with open structure and documents expressions for the moment capacity as well as the shear force capacity......The project presented here deals with the load-bearing capacity of reinforced beams made of lightweight aggregate concrete with open structure and documents expressions for the moment capacity as well as the shear force capacity...
24 CFR 3285.202 - Soil classifications and bearing capacity.
2010-04-01
... 24 Housing and Urban Development 5 2010-04-01 2010-04-01 false Soil classifications and bearing... Soil classifications and bearing capacity. The soil classification and bearing capacity of the soil must be determined before the foundation is constructed and anchored. The soil classification...
The Influence of Time on Bearing Capacity of Driven Piles
Jensen, J. Lysebjerg; Augustesen, A.; Sørensen, Carsten S.
2004-01-01
In Danish engineering practice, one of the ways to determine the ultimate bearing capacity of an axially loaded pile is by means of geostatic formulas. In the equation describing the contribution from the shaft friction to the total bearing capacity for piles located entirely or partly in clay, a...
Seismic ultimate bearing capacity of strip footings on slope
无
2007-01-01
The influence of earthquake forces on ultimate bearing capacity of foundations on sloping ground was studied. A solution to seismic ultimate bearing capacity of strip footings on slope was obtained by utilizing pseudo-static analysis method and taking the effect of intermediate principal stress into consideration. Based on limit equilibrium theory, the formulae for computing static bearing capacity factors, Nq, Nc, Nγ, and dynamic bearing capacity factors, Nqd, Ncd, Nγd, which are associated with surcharge, cohesion and self-weight of soils respectively, were presented. A great number of analysis calculations were carried out to obtain the relationship curves of the static and dynamic bearing capacity factors versus various calculation parameters. The curves can serve as the practical engineering design. The calculation results also show that when the values of horizontal and vertical seismic coefficients are 0.2, the dynamic bearing capacity factors Nqd, Ncd and Nγd, in which the effects of intermediate principal stress are taken into consideration, increase by 4%-42%, 3%-27% and 34%-57%, respectively.
Bearing capacity analysis using the method of characteristics
Jian-Ping Sun; Zhi-Ye Zhao; Yi-Pik Cheng
2013-01-01
Using the method of characteristics,the bearing capacity for a strip footing is analyzed.The method of characteristics leads to an exact true limit load when the calculations of the three terms in the bearing capacity formula are consistent with one collapse mechanism and the soil satisfies the associated flow rule.At the same time,the method of characteristics avoids the assumption of arbitrary slip surfaces,and produces zones within which equilibrium and plastic yield are simultaneously satisfied for given boundary stresses.The exact solution without superposition approximation can still be expressed by Terzaghi's equation of bearing capacity,in which the bearing capacity factor Nyλ is dependent on the dimensionless parameterλand the friction angle φ.The influence of groundwater on the bearing capacity of the shallow strip footing is considered,which indicates that when the groundwater effect is taken into account,the error induced by the superposition approximation can be reduced as compared with dry soil condition.The results are presented in the form of charts which give the modified value (yλcw/Nyλc) of bearing capacity factor.Finally,an approximated analytical expression,which provides results in close agreement with those obtained by numerical analysis in this paper,has been suggested for practical application purposes.
Bearing Capacity of Foundations subjected to Impact Loads
Ibsen, Lars Bo; Jakobsen, Kim Parsberg
1996-01-01
In the design process for foundations, the bearing capacity calculations are normally restricted to monotonic loads. Even in cases where the impact load is of significance the dynamic aspects are neglected by use of a traditional deterministic ultimate limit state analysis. Nevertheless it is common knowledge that the soil under suchcircumstances normally will produce a reaction, which exceed the static capacity. A new model, which takes these significant properties into account is presented.
Bearing capacity evaluation of rubblized concrete pavements
González, M.
2009-03-01
Full Text Available The paper presents the findings of a research work performed on a real scale concrete pavement project where Rubblizing technology was used for its structural rehabilitation. Rubblizing may be defined as a fracture technique in which a concrete pavement slab is transformed in a granular base with a very high Modulus. This technique, fractures the concrete slab in angular pieces by using a concentrated dynamic load of low amplitude and high frequency. The research work was based on field study on the rehabilitation of 5 km motorway. The structural evaluations where made, before, during and after one year construction. Measurements and site evaluation where made by using DCP, Light Weight Deflectometer and FWD (on top of asphalt layer and excavating inside pits. The structural capacity of the Rubblized layer was evaluated through theoretical analysis. Because of the anisotropic properties of the Rubblized layer the results are presented using AASHTO structural layer coefficient. The structural layer coefficients recommended are between the range of 0.25 and 0.30 for concrete slabs with thickness grater than 220 mm.El trabajo presenta los resultados de un estudio a escala real de la capacidad estructural de un firme de hormigón rehabilitado utilizando la técnica de Rubblizing. La técnica de Rubblizing ha sido traducida como el pulverizado del firme de hormigón pero, es más bien un efecto combinado de trituración y fracturación de la losa de hormigón en todo su espesor para convertir esta en una base granular de alto módulo. Esta tecnica fractura la losa de hormigón en trozos angulares y entrelazados empleando una carga dinámica concentrada, de baja amplitud y alta frecuencia. La investigación se basó en el estudio de la rehabilitación de 5 km de autopista. Los estudios de la capacidad estructural fueron realizados durante, al término y un año después de la construcción. Para las mediciones y evaluaciones de terreno se utilizó, el
Bearing Capacity of Foundations subjected to Impact Loads
Ibsen, Lars Bo; Jakobsen, Kim Parsberg
1996-01-01
In the design process for foundations, the bearing capacity calculations are normally restricted to monotonic loads. Even in cases where the impact load is of significance the dynamic aspects are neglected by use of a traditional deterministic ultimate limit state analysis. Nevertheless it is...
Soil bearing capacity under dynamic conditions for the ALWR systems
The present work is a part of the studies carried out by ENEL DSR-VDN and ISMES on ALWR systems. From a geotechnical point of view the soil bearing capacity in dynamic stress conditions is of particular interest for the development of the ALWR project. In fact the possible Italian sites are not rocky sites but generally of alluvial kind. This work is a continuation of a previous paper. Here we show the results of the finite element soil-structure analysis and the subsequent bearing capacity analysis with reference to four geotechnical profiles that represent the lower and upper bound of the Italian variability range of data. Some comments are made on the codes of practice, of interest to Italy, the safety factor concept and the possible use of other calculation methods in addition to classical ones. (author)
Bearing Capacity of Mixed Pile with Stiffness Core
YUE Jianwei; JIANG Xinliang; LING Guangrong
2006-01-01
To study load transfer mechanism and bearing capacity of a mixed pile with stiffness core (MPSC), which is formed by inserting a precast reinforced concrete pile (PRCP), in-situ tests involving MPSCs with different lengths, diameters, water cement ratios and PRCPs, cement mixed piles, and drilling hole piles, were carried out.Limit bearing capacities, load-settlement curves and stress distribution of MPSCs and mixed piles were obtained.The load transfer between cement soil and PRCP was analyzed by finite element method (FEM).Test results and FEM analysis show that an MPSC has fully utilized the big friction from a cement mixed pile and the high compressive strength from a PRCP which transfers outer top load into the inner cement soil, and that inserting a PRCP into a mixed pile changes the stress distribution of a mixed pile and improves frictional resistance between a mixed pile and soil.The length and the section area on PRCP of an MPSC both have an optimum value.Adopting MPSC is effective in improving the bearing capacity of soft soil ground.
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.
Bearing Capacity of the Working Platform with Kinematic Method
Białek Katarzyna
2015-03-01
Full Text Available Bearing capacity of the working platform for heavy tracks was analysed using Distinct Layout Optimization (DLO method. The platform layer constructed from cohesionless soils is resting on weak cohesive subgrade. Different thickness of the platform, its effective angle of internal friction and undrained shear strength of the soft soil were taken into consideration. Kinematic method permits different failure mechanisms to be analyzed. Margin of safety for a given load and subsoil conditions was determined using two approaches: increasing the load or decreasing the shear strength up to failure. The results were compared with solution proposed in BRE recommendations.
Cable bolt bearing capacity - an in situ parametric study
Souček, Kamil; Waclawik, Petr; Koníček, Petr; Ptáček, Jiří; Hastíková, Alice; Kukutsch, Radovan
Montreal, Quebec: ISRM, 2015. ISBN 978-1-926872-25-4. [International Symposium on Rock Mechanics /13./. Montreal, Quebec (CA), 10.05.2015-13.05.2015] R&D Projects: GA MŠk ED2.1.00/03.0082; GA MŠk(CZ) LO1406; GA MV VG20102014034 Institutional support: RVO:68145535 Keywords : cable bolt * Cable-Resin-Rock system (CRR system) * bolt borehole ratio * system stiffness * bearing capacity Subject RIV: JQ - Machines ; Tools http://www.isrm2015.com/
Bearing Capacity Analysis Using Meshless Local Petrov-Galerkin Method
Mužík Juraj
2014-05-01
Full Text Available The paper deals with use of the meshless method for soil bearing capacity analysis. There are many formulations of the meshless methods. The article presents the Meshless Local Petrov-Galerkin method (MLPG - local weak formulation of the equilibrium equations. The main difference between meshless methods and the conventional finite element method (FEM is that meshless shape functions are constructed using randomly scattered set of points without any relation between points. The Heaviside step function is test function used in the meshless implementation presented in the article. Heaviside test function makes weak formulation integral very simple, because only body integral in governing equation is due a body force.
Zhao Feng
2015-01-01
Full Text Available The slurry wall bored grouting has some defects. The pile-base post grouting technique can efficiently make up these defects and greatly improve the bearing capacity. Based on the pile-base post grouting technique and its process analysis, this paper carries out a detailed analysis about the improvement of mechanism of bearing capacity and mechanism of spherical expansion by the use of pile-base post grouting technique, as well as the estimation method of the bearing capacity of pile-base post grouting pile, which has a certain reference value for theoretical research and technical application of the technique.
Zhao Feng
2015-01-01
The slurry wall bored grouting has some defects. The pile-base post grouting technique can efficiently make up these defects and greatly improve the bearing capacity. Based on the pile-base post grouting technique and its process analysis, this paper carries out a detailed analysis about the improvement of mechanism of bearing capacity and mechanism of spherical expansion by the use of pile-base post grouting technique, as well as the estimation method of the bearing capacity of pile-base pos...
Effect of lobe profile on the load capacity of 2-lobe journal bearing
Stanislaw; STRZELECKI
2001-01-01
The rotors of turbogenerators operate in 2-lobe journal bearings. These bearings can bedesigned with the same or different profile of upper and bottom lobe, e.g. the upper lobe has cylin-drical and bottom one the offset profile. Shaping the bearing profile this way allows the variation ofstatic and dynamic characteristics of bearing. The static characteristics consist among others theload capacity of bearing which is very important parameter. The paper introduces the results ofcalculations of load capacity of 2-lobe journal bearing characterised by different profiles of upperand bottom lobe. The laminar, adiabatic oil flow in the bearing lubricating gap, parallel orientationof journal and bearing axis as well as the static equilibrium position of journal have been assumed.
Sun Chao
2015-09-01
Full Text Available The regional land safety evaluation indicator system is built based on the land comprehensive bearing capacity in the study and the primary and secondary relationship of the land safety obstacle factors of Mengshan tourist area and influence degree of various obstacle factors on land safety are determined, so as to provide reference for sustainable utilization of land in Mengshan tourist area. The results indicate that: (i The land comprehensive bearing capacity of Mengshan tourist area is at the safety state. Where, the social bearing capacity is at the weak safety state, which is the most critical factor influencing the land bearing capacity of Mengshan tourist area. (ii The traveling and living ratio, the output values of the secondary industry and the tertiary industry of the unit construction land and the land utilization intensity are the key factors influencing the regional safety level.
Regressive approach for predicting bearing capacity of bored piles from cone penetration test data
Iyad S. Alkroosh
2015-10-01
Full Text Available In this study, the least square support vector machine (LSSVM algorithm was applied to predicting the bearing capacity of bored piles embedded in sand and mixed soils. Pile geometry and cone penetration test (CPT results were used as input variables for prediction of pile bearing capacity. The data used were collected from the existing literature and consisted of 50 case records. The application of LSSVM was carried out by dividing the data into three sets: a training set for learning the problem and obtaining a relationship between input variables and pile bearing capacity, and testing and validation sets for evaluation of the predictive and generalization ability of the obtained relationship. The predictions of pile bearing capacity by LSSVM were evaluated by comparing with experimental data and with those by traditional CPT-based methods and the gene expression programming (GEP model. It was found that the LSSVM performs well with coefficient of determination, mean, and standard deviation equivalent to 0.99, 1.03, and 0.08, respectively, for the testing set, and 1, 1.04, and 0.11, respectively, for the validation set. The low values of the calculated mean squared error and mean absolute error indicated that the LSSVM was accurate in predicting the pile bearing capacity. The results of comparison also showed that the proposed algorithm predicted the pile bearing capacity more accurately than the traditional methods including the GEP model.
Evaluation of Bearing Capacity of Strip Footing Using Random Layers Concept
Kawa Marek
2015-09-01
Full Text Available The paper deals with evaluation of bearing capacity of strip foundation on random purely cohesive soil. The approach proposed combines random field theory in the form of random layers with classical limit analysis and Monte Carlo simulation. For given realization of random the bearing capacity of strip footing is evaluated by employing the kinematic approach of yield design theory. The results in the form of histograms for both bearing capacity of footing as well as optimal depth of failure mechanism are obtained for different thickness of random layers. For zero and infinite thickness of random layer the values of depth of failure mechanism as well as bearing capacity assessment are derived in a closed form. Finally based on a sequence of Monte Carlo simulations the bearing capacity of strip footing corresponding to a certain probability of failure is estimated. While the mean value of the foundation bearing capacity increases with the thickness of the random layers, the ultimate load corresponding to a certain probability of failure appears to be a decreasing function of random layers thickness.
Pieczynska-Kozlowska, Joanna
2014-05-01
One of a geotechnical problem in the area of Wroclaw is an anthropogenic embankment layer delaying to the depth of 4-5m, arising as a result of historical incidents. In such a case an assumption of bearing capacity of strip footing might be difficult. The standard solution is to use a deep foundation or foundation soil replacement. However both methods generate significant costs. In the present paper the authors focused their attention on the influence of anthropogenic embankment variability on bearing capacity. Soil parameters were defined on the basis of CPT test and modeled as 2D anisotropic random fields and the assumption of bearing capacity were made according deterministic finite element methods. Many repeated of the different realizations of random fields lead to stable expected value of bearing capacity. The algorithm used to estimate the bearing capacity of strip footing was the random finite element method (e.g. [1]). In traditional approach of bearing capacity the formula proposed by [2] is taken into account. qf = c'Nc + qNq + 0.5γBN- γ (1) where: qf is the ultimate bearing stress, cis the cohesion, qis the overburden load due to foundation embedment, γ is the soil unit weight, Bis the footing width, and Nc, Nq and Nγ are the bearing capacity factors. The method of evaluation the bearing capacity of strip footing based on finite element method incorporate five parameters: Young's modulus (E), Poisson's ratio (ν), dilation angle (ψ), cohesion (c), and friction angle (φ). In the present study E, ν and ψ are held constant while c and φ are randomized. Although the Young's modulus does not affect the bearing capacity it governs the initial elastic response of the soil. Plastic stress redistribution is accomplished using a viscoplastic algorithm merge with an elastic perfectly plastic (Mohr - Coulomb) failure criterion. In this paper a typical finite element mesh was assumed with 8-node elements consist in 50 columns and 20 rows. Footings width B
Analysis of bearing capacity of CA corner wall in AP1000 nuclear power plant
Background: The module construction technology is widely used in the AP1000 nuclear power plant. The CA structural module in the containment building is important for the safety of the nuclear power plant, the corner wall of the CA structural is critical under load, so it is important to do research on bearing capacity of CA corner wall. Purpose: Finite element analysis model of the CA comer wall is conducted in the ABAQUS software to study the bearing capacity and the stress/strain state of the CA comer' wall under different load cases. Methods: Finite element analysis model considering the material nonlinearity, contact nonlinearity and geometric nonlinearity conducted in the ABAQUS software is used for the analysis of the CA corner wall. Results: The ultimate bearing capacities of the CA comer wall in different loads are studied, and the study also gets the load-displacement curves. The bearing capacities of CA corner wall under different axial loads are also studied in this paper. The influence of ultimate bearing capacities of CA comer wall is founded out if the steel and concrete work together. Conclusions: When the CA corner wall subjects to the bending load, the failure part of the CA corner wall is the corner core concrete. When the CA corner wall subjects to the shear load, the failure part of the CA corner wall is the straight module wall. The axial load has notable influence on the capacity of CA corner wall. (authors)
Dynamic load testing on the bearing capacity of prestressed tubular concrete piles in soft ground
Yu, Chuang; Liu, Songyu
2008-11-01
Dynamic load testing (DLT) is a high strain test method for assessing pile performance. The shaft capacity of a driven PTC (prestressed tubular concrete) pile in marine soft ground will vary with time after installation. The DLT method has been successfully transferred to the testing of prestressed pipe piles in marine soft clay of Lianyungang area in China. DLT is investigated to determine the ultimate bearing capacity of single pile at different period after pile installation. The ultimate bearing capacity of single pile was founded to increase more than 70% during the inventing 3 months, which demonstrate the time effect of rigid pile bearing capacity in marine soft ground. Furthermore, the skin friction and axial force along the pile shaft are presented as well, which present the load transfer mechanism of pipe pile in soft clay. It shows the economy and efficiency of DLT method compared to static load testing method.
THE CAPACITY OF INTERNATIONAL ORGANIZATIONS TO BEAR INTERNATIONAL RESPONSIBILITY
Ovidiu-Emilian IVANESCU
2015-01-01
The status of international personality is not exclusively reserved for states. In modern days, the international organizations have legal international personality and also have the capacity to be internationally responsible for their conduct. Some particularities of the legal personality of international organizations are decisive in determining their international responsibility. The study will establish the connection between the foundations of the personality and responsibility of an int...
THE CAPACITY OF INTERNATIONAL ORGANIZATIONS TO BEAR INTERNATIONAL RESPONSIBILITY
Ovidiu-Emilian IVANESCU
2015-07-01
Full Text Available The status of international personality is not exclusively reserved for states. In modern days, the international organizations have legal international personality and also have the capacity to be internationally responsible for their conduct. Some particularities of the legal personality of international organizations are decisive in determining their international responsibility. The study will establish the connection between the foundations of the personality and responsibility of an international organization. It will be also analysed the situation of third parties in establishing the responsibility of an international organization.
Experimental Study on Post Grouting Bearing Capacity of Large Diameter Bored Piles
Wang Duanduan
2015-01-01
Full Text Available Post grouting can improve the inherent defects such as the formation of the mud cake at pile side and the sediment at pile end in the process of bored pile construction. Thus post grouting has been widely used in Engineering. The purpose of this paper is to research the influences of post grouting to pile bearing capacity more systematically and intuitively. Combined with the static load test of four test piles in Weihe River Bridge test area of new airport highway in Xi’an, the bearing capacity and settlement of routine piles and post grouting piles are comparatively analyzed. The test results show that under the same geological condition, post grouting can improve the properties of pile tip and pile shaft soil of bored piles significantly, enhance the ultimate resistance, improve the ultimate bearing capacity and reduce the pile tip settlement. Then post grouting can aim to optimize pile foundation.
Determining the bearing capacity of soil foundation reinforced by geogrid
E.S. Kolosov
2012-06-01
Full Text Available The article deals with improving the construction properties of soils due to their reinforcement by geosynthetics, namely the geogrid. Geosynthetics have been widely used in the construction of extended objects: the mound of roads and railways, dams, retaining walls.The article includes a description of the possible destruction of reinforced soil base under load. It is established that the soil reinforcement by geogrids prevents adhesive failure (slip.The definition of carrying capacity of geogrid reinforced foundation is considered in terms of spatial task for the case when the ratio of base length to its width is not more than 5. The solution presented in the form of the equilibrium conditions of active and passive earth pressure.The coefficient of geogrid space work for water-saturated silt and fine sands is derivered. The optimal size and depth of geogrid inception are determined.
Experimental Study on Post Grouting Bearing Capacity of Large Diameter Bored Piles
Wang Duanduan; Wang Longfei; Zhang Lipeng
2015-01-01
Post grouting can improve the inherent defects such as the formation of the mud cake at pile side and the sediment at pile end in the process of bored pile construction. Thus post grouting has been widely used in Engineering. The purpose of this paper is to research the influences of post grouting to pile bearing capacity more systematically and intuitively. Combined with the static load test of four test piles in Weihe River Bridge test area of new airport highway in Xi’an, the bearing capac...
Empirical Model Evaluation of Sedimentary Residual Soil Bearing Capacity from Surface Wave Method
Sri Atmaja Rosyidi
2010-10-01
Full Text Available Bearing capacity of the subgrade layers has significant influence on the performance of the overall pavement structure. In this study, the Spectral Analysis of Surface Wave (SASW method was used for assessing the stiffness of pavement subgrade layer. The SASW method employed was based on the Rayleigh-wave propagation. Using the phase difference data of Rayleigh waves, the experimental dispersion curve of phase velocity was obtained. Consequently, inversion process was conducted to obtain the shear wave velocity and the dynamic modulus of the pavement structure. The results showed that some empirical models of the shear wave velocity and the dyamic elastic modulus versus soil bearing capacity of the California bearing ratio (CBR and dynamic cone penetrometer (DCP were derived. Good agreement was also found between these empirical models compared to that of previous studies
Krabbenhøft, Sven; Damkilde, Lars; Krabbenhøft, Kristian
2012-01-01
Lower-bound calculations based on the finite element method are used to determine the bearing capacity of a strip foundation subjected to a vertical, eccentric load on cohesionless soil with varying surcharges. The soil is assumed perfectly plastic following the Mohr-Coulomb failure criterion. Th...
The Bearing Capacity of Strip Footings in Cohesionless Soil Subject to Eccentric and Inclined Loads
Krabbenhøft, Sven; Damkilde, Lars; Krabbenhøft, Kristian
2014-01-01
the Mohr-Coulomb failure criterion. The results are reported as graphs showing the bearing capacity as a function of the friction angle, the eccentricity, inclination and the surcharge. The results have been compared with the Eurocode 7 and for smaller eccentricities, except in the case of no...
Bearing Capacity Analyses for the Great Belt East Bridge Anchor Blocks
Sørensen, Carsten Steen; Clausen, Carl J. Frimann; Andersen, Henrik
1993-01-01
This paper presents a comparison between different methods of bearing capacity analyses: Upper Bound Method. Limit Equilibrium Analysis and Finite Element Analysis. For the Great Belt East Bridge anchor blocks it was concluded that these methods of calculation agree within 5%. However, for cases...
Influence of Reel Lay on Residual Stress and Ultimate Bearing Capacity of Pipe
Liao, Hongqian; Wang, Liquan
Reel lay is a fast and cost-effective way to install subsea pipelines. During reel lay, pipe's repeated plastic bending produces residual stress, which has influence on pipe's ultimate bearing capacity. First, the deformation of pipe in reel lay is analyzed, and the cyclic bending stages are simplified for convenience of theoretical research. Based on the finite element method (FEM), the Ramberg-Osgood model is adopted to describe material's mechanical property with kinematic hardening rule, and five bending stages are simulated. Further, the influence of material parameters and geometry parameters on pipe's residual stress is studied. Finally, the effect of residual stress on pipe's external pressure bearing capacity and tensile capacity is analyzed. Some important conclusions can be drawn: (1) the influence of diameter-thick ratio on residual stress is small, and material parameters' effect on the residual stress is large; (2) the influence of residual stress on pipe's external pressure bearing capacity is small, but its influence on tensile capacity is large.
ZHAO Jianhua; LIANG Yingna; GAO Dianrong
2014-01-01
Durning the design process of hydrostatic rotary worktable, the processing and assembly tolerance, (the offset of worktable and the gap of the oil film’s thickness) is ignored. But it will cause that the real bearing of oil pocket deviates from the initial design value, and then the performance of rotary worktable will be reduced significantly. Up to now, no effort is found toward the research of influence of the processing and assembly tolerance on the performance of the rotary worktable. So the hydrostatic oil film is assumed as the elastomer in this paper, and then the bearing capacity of the oil pocket is studied with and without the mass offset of the worktable by taking an expression between the bearing capacity and the oil film’s thickness of the oil pocket as the deform compatibility equation. The influence of the processing tolerance of the oil sealing belt’s gap on the bearing capacity of the oil pocket is analyzed. In the light of the liquid hydrostatic worktable of Gantry Moving Milling Center using on the scene, the oil pocket’s pressure of the worktable is tested using Rotary Worktable Test System under the circumstance of the mass offset of the worktable and the gap tolerance of the oil sealing belt, and then the equivalent offset of worktable, the average pressure of the oil pocket and the actual thickness of the oil film are analyzed respectively. The test results show that the bearing capacity component of the oil pocket caused by G is consistent, and the component caused by M is relative to the position of the oil pocket. When the oil sealing belt’s gap is larger than the theoretical value, the bearing capacity of the oil pocket is smaller than the others;whereas the bearing capacity of the oil pocket is larger than the others. The maximum and minimum equivalent offsets are 0.256 4 mm and 0.047 5 mm, respectively, and the average oil pocket pressure varies from 0.345 MPa to 0.460 MPa, the maximum and minimum value of the actual oil film
无
2007-01-01
Seismic bearing capacity factors of a strip footing placed on soil slope were determined with both associated and nonassociated flow rules. Quasi-static representation of earthquake effects using a seismic coefficient concept was adopted for seismic bearing capacity calculations. A multi-wedge translational failure mechanism was used to obtain the seismic bearing capacity factors for different seismic coefficients and various inclined angles. Employing the associated flow rule, numerical results were compared with the published solutions. For bearing capacity factors related to cohesion and equivalent surcharge load, the maximum difference approximates 0.1%. However, the difference of bearing capacity factor related to unit weight is larger. With the two flow rules, the seismic bearing capacity factors were presented in the form of design charts for practical use. The results show that seismic bearing capacity factors related to the cohesion, the equivalent surcharge load and the unit weight increase greatly as the dilatancy angle increases, and that the nonassociated flow rule has important influences on the seismic bearing capacity.
Krabbenhøft, Sven; Damkilde, Lars; Krabbenhøft, Kristian
The calculation of the bearing capacity of a strip foundation located on the edge of or near a slope is commonly based on the well-known bearing capacity equation applying so called slope factors, and expressions for these factors have been proposed by amongst others Brinch Hansen and Vesic. Thes...
Connectivity strategies to enhance the capacity of weight-bearing networks
The connectivity properties of a weight-bearing network are exploited to enhance its capacity. We study a 2D network of sites where the weight-bearing capacity of a given site depends on the capacities of the sites connected to it in the layers above. The network consists of clusters, viz., a set of sites connected with each other with the largest such collection of sites being denoted as the maximal cluster. New connections are made between sites in successive layers using two distinct strategies. The key element of our strategies consists of adding as many disjoint clusters as possible to the sites on the trunk T of the maximal cluster. In the first strategy the reconnections start from the last layer upwards and stop when no new sites are added. In the second case, the reconnections start from the top layer and go all the way down to the last layer. The new networks can bear much higher weights than the original networks and have much lower failure rates. The first strategy leads to a greater enhancement of stability, whereas the second leads to a greater enhancement of capacity compared to the original networks. The original network used here is a typical example of the branching hierarchical class. However, the application of strategies similar to ours can yield useful results in other types of networks as well
The effect of manufacturing tolerances on the load carrying capacity of large diameter bearings
Starvin M S; Manisekar K
2015-09-01
This paper deals with simplified 3D finite element (FE) analysis on the effect of manufacturing tolerances on the load carrying capacity of large diameter bearings based on Hertz theory. The nonlinear connector elements are used to model the rolling elements. This model enables us to evaluate the contact load on the rolling elements with relatively reduced calculation time. FE study has been carried out by allocating tolerance on balls and raceways using Monte Carlo simulation technique. The variation in dimension on balls is taken as per IS 2898-1976. A coding has been developed and employed for Monte Carlo simulation. Using the results of Monte Carlo simulation, tolerance has been assigned to the elements of large diameter bearing. From the results of finite element analysis, it is identified that analysis of large diameter bearing with tolerance on ball and raceway will lead to safe design.
Seismic bearing capacity of strip footings on rock masses using the Hoek–Brown failure criterion
Amin Keshavarz
2016-04-01
Full Text Available In this paper, the bearing capacity of strip footings on rock masses has been studied in the seismic case. The stress characteristics or slip line method was used for analysis. The problem was analyzed in the plane strain condition using the Hoek–Brown failure criterion. First, the equilibrium equations along the stress characteristics were obtained and the rock failure criterion was applied. Then, the equations were solved using the finite difference method. A computer code has been provided for analysis. Given the footing and rock parameters, the code can calculate the stress characteristics network and obtain the stress distribution under the footing. The seismic effects have been applied as the horizontal and vertical pseudo-static coefficients. The results of this paper are very close to those of the other studies. The seismic bearing capacity of weightless rock masses can be obtained using the proposed equations and graphs without calculating the whole stress characteristics network.
Static Indentation Load Capacity of the Superelastic 60NiTi for Rolling Element Bearings
DellaCorte, Christopher; Moore, Lewis E., III; Clifton, Joshua S.
2012-01-01
The nickel-rich, binary nickel-titanium alloys, such as 60NiTi (60Ni-40Ti by wt%), are emerging as viable materials for use in mechanical components like rolling element bearings and gears. 60NiTi is a superelastic material that simultaneously exhibits high hardness and a relatively low elastic modulus (approx.100 GPa). These properties result in the potential to endure extremely high indentation loads such as those encountered in bearings, gears and other mechanical components. In such applications, quantifying the load that results in permanent deformation that can affect component performance and life is important. In this paper, the static load capacity is measured by conducting indentation experiments in which 12.7 mm diameter balls made from the ceramic Si3N4 are pressed into highly polished, hardened 60NiTi flat plates. Hertz stress calculations are used to estimate contact stress. The results show that the 60NiTi surface can withstand an approximately 3400 kN load before significant denting (>0.6 microns deep) occurs. This load capacity is approximately twice that of high performance bearing steels suggesting that the potential exists to make highly resilient bearings and components from such materials.
Seismic bearing capacity of strip footings on rock masses using the Hoek–Brown failure criterion
Amin Keshavarz; Abdoreza Fazeli; Siavosh Sadeghi
2016-01-01
In this paper, the bearing capacity of strip footings on rock masses has been studied in the seismic case. The stress characteristics or slip line method was used for analysis. The problem was analyzed in the plane strain condition using the Hoek–Brown failure criterion. First, the equilibrium equations along the stress characteristics were obtained and the rock failure criterion was applied. Then, the equations were solved using the finite difference method. A computer code has been provided...
Static and dynamic bearing capacity of strip footings, under variable repeated loading
ARVIN, Mohammad Reza; ASKARI, Faradjollah; Farzaneh, Orang
2012-01-01
The problem of bearing capacity of strip footings is one of the basic and classical problems of geotechnical engineering. Footings under variable repeated loads are vulnerable to collapse due to accumulation of plastic strains or inadaptation. Unlike common limit state methods, the shakedown method can be applied to investigate the behavior of structures subjected to loads varying and repeating in time. In the present study, shakedown theory is employed to determine the static and dy...
Bearing Capacity of Spatially Random Cohesive Soil Using Numerical Limit Analyses
Kasama, Kiyonobu; Whittle, Andrew
2007-01-01
This paper describes a probabilistic study of the two dimensional bearing capacity of a vertically loaded strip footing on spatially random, cohesive soil using Numerical Limit Analyses (NLA‐CD). The analyses uses a Cholesky Decomposition (CD) technique with mid‐point discretization to represent the spatial variation in undrained shear strength within finite element meshes for both upper and lower bound analyses, and assumes an isotropic correlation length. Monte Carlo simulations are then us...
Evaluation of safe bearing capacity of soil foundation by using numerical analysis method
Abdoullah Namdar
2014-10-01
Full Text Available The soil mechanic laboratory results help in accurate soil foundation design and enhancement failure mitigation. The mixing soil design has been used in many geotechnical engineering for soil improvement. In this paper, several types of soil foundations have been made from mixed soil. The bearing capacity of soil foundations by using mixed soil parameters and change footing dimensions have been calculated. 180 footings, placed on 15 soil foundation types have been designed. It is assumed the underground water has not effect to bearing capacity of soil foundation. The results of numerical analysis and mixed soils technique have been combined. The numerical analysis has supported mixed soil design, and introduced an appropriate result for soil foundation design. The effects of mixed soil on depth and width of footing have been compared. The mixed soil design influenced numerical analysis result, and economically, soil foundation design helps to select the appropriate dimensions of footings. The result of numerical analysis supports geotechnical and structural engineering codes, predicts structural stability with different age, natural hazard and prevention as well as it is useful in understanding safe bearing capacity of soil foundation behavior.
The influence of selecting the correlation model on soil parameters and bearing capacity
Pieczynska-Kozlowska, Joanna M.
2016-04-01
Consideration of soil spatial variability in the geotechnical design is still marginalized. The design process is based on taking the average parameters, which often results the oversize of geotechnical constructions. This procedure works until there are no geotechnical design problems. In most cases, geotechnical constructions represent a small percentage of the total investment so effects lacking developed of optimization procedures. If the optimization is needed requires the most accurate mapping of the soil. The basic background for statistical interpretation of soil spatially variables are Cone Penetration Tests, which represents variable nature of the soil with depth. Assuming the soil structure as a spatially random variable can be applied by description based on random fields. Field parameters are the probability distribution and correlation model dependent of a scale of fluctuation estimated from CPT. The main goal of this study is to contribute to the understanding on how the choice of correlation model affects random soil properties and for example shallow foundation bearing capacity. The study is particularly focused on scale of fluctuation as related to the reduction of bearing capacity. Scale of fluctuation were estimated using two effective methods: Vanmarcke and Rice. Soil properties were analyzed from 12 Cone Penetration Tests distributed throughout the regions of Świebodzice (Lower Silesia, Poland). While the project was developed in hilly terrain the macrolevelling were taken involving the displacement of native soil mass to form a working platform for shallow foundation. The construction of embankment has been tested by cone resistance tests to determine the parameters for the design. The procedure adopted to this study include the modeling soil variability from the CPT results and calculate the bearing capacity of shallow foundation using random finite element method and different correlation models. The aim of study was to answer questions
无
2005-01-01
The famous physicist made for his scholars this riddle. A fellow encountered a bear in a wasteland. There was nobody else there. Both were frightened and ran away. Fellow to the north, bear to the west. Suddenly the fellow stopped, aimed his gun to the south and shot the bear. What colour was the bear?
Hertzian Load-bearing Capacity of Hybrid and Nano-hybrid Resin Composites Stored Dry and Wet
Farmani S; Orandi S; Sookhakiyan M; Mese A
2016-01-01
Statement of Problem: Hertzian indentation test has been proven to be an efficient and reliable alternative upon Vickers hardness test. This method has been used to test dental ceramics, amalgams, glass ionomers and luting cements.There is limited published information about the load-bearing capacity of resin composites using Hertizian indentation test. Objectives: To investigate the load-bearing capacity of hybrid and nano-hybrid resin composites stored dry or wet up to 30 days, using ...
Tamrazyan Ashot Georgievich
2012-01-01
Accurate and adequate description of external influences and of the bearing capacity of the structural material requires the employment of the probability theory methods. In this regard, the characteristic that describes the probability of failure-free operation is required. The characteristic of reliability means that the maximum stress caused by the action of the load will not exceed the bearing capacity. In this paper, the author presents a solution to the problem of calculation of str...
Bearing Capacity of Footings on Thin Layer of Sand on Soft Cohesive Soil
Philipsen, J.; Sørensen, Carsten S.
have been presented. These methods often give widely different results. Therefore, in the light of the numerical calculations, the analytical and empirical calculation methods have been evaluated and compared. The calculations have been carried out based on results from well documented and well......This paper contains the results of some numerical calculations performed with the aim to determine the bearing capacities of footings placed on a thin layer of sand underlain by soft cohesive soil. During the last 30-35 years different analytical and empirical calculation methods for this situation...
Ældre betonbroers bæreevne (Load bearing capacity of old concrete bridges)
Nielsen, Anders
1999-01-01
Two old bridges have been analysed in connection with their demolition. The first one is a pedestrian bridge, the Gefion bridge, from 1894. This is the first bridge of reinforced concrete in Denmark. Here the creep in the concrete severely have changed the way in which the load on the bridge was ...... carried. - The other is a motor way bridge from 1939, which were reinforced 1991 with external steel plates on the areas of shear on the beams. Four beams were carried to our laboratory and load tested. The steel plates have doubled the load bearing capacity of the beams....
VIS-NIR, SWIR and LWIR Imagery for Estimation of Ground Bearing Capacity.
Fernández, Roemi; Montes, Héctor; Salinas, Carlota
2015-01-01
Ground bearing capacity has become a relevant concept for site-specific management that aims to protect soil from the compaction and the rutting produced by the indiscriminate use of agricultural and forestry machines. Nevertheless, commonly known techniques for its estimation are cumbersome and time-consuming. In order to alleviate these difficulties, this paper introduces an innovative sensory system based on Visible-Near InfraRed (VIS-NIR), Short-Wave InfraRed (SWIR) and Long-Wave InfraRed (LWIR) imagery and a sequential algorithm that combines a registration procedure, a multi-class SVM classifier, a K-means clustering and a linear regression for estimating the ground bearing capacity. To evaluate the feasibility and capabilities of the presented approach, several experimental tests were carried out in a sandy-loam terrain. The proposed solution offers notable benefits such as its non-invasiveness to the soil, its spatial coverage without the need for exhaustive manual measurements and its real time operation. Therefore, it can be very useful in decision making processes that tend to reduce ground damage during agricultural and forestry operations. PMID:26083227
VIS-NIR, SWIR and LWIR Imagery for Estimation of Ground Bearing Capacity
Roemi Fernández
2015-06-01
Full Text Available Ground bearing capacity has become a relevant concept for site-specific management that aims to protect soil from the compaction and the rutting produced by the indiscriminate use of agricultural and forestry machines. Nevertheless, commonly known techniques for its estimation are cumbersome and time-consuming. In order to alleviate these difficulties, this paper introduces an innovative sensory system based on Visible-Near InfraRed (VIS-NIR, Short-Wave InfraRed (SWIR and Long-Wave InfraRed (LWIR imagery and a sequential algorithm that combines a registration procedure, a multi-class SVM classifier, a K-means clustering and a linear regression for estimating the ground bearing capacity. To evaluate the feasibility and capabilities of the presented approach, several experimental tests were carried out in a sandy-loam terrain. The proposed solution offers notable benefits such as its non-invasiveness to the soil, its spatial coverage without the need for exhaustive manual measurements and its real time operation. Therefore, it can be very useful in decision making processes that tend to reduce ground damage during agricultural and forestry operations.
Love Sharma
2015-08-01
Full Text Available This research was performed to investigate the effect of bearing capacity of strip footing on geogrid reinforced sand overlay on stabilized expansive soil (i.e. double layer soil system and check the different parameters contributing to their performance using laboratory model tank tests. The parameters investigated in this study include H/B (thickness of top sandy layer to width of footing u/B (location of the 1st layer of reinforcement to width of footing, h/B (vertical spacing between consecutive geogrid layers to width of footing, b/B (length of the geogrid layer to width of footing. The effect of different H/B ratios and geogrid reinforcement N values on the bearing capacity ration (BCR and settlement reduction ratio (SRR were also investigated. The results show that bearing capacity increases significantly with increasing the H/B ratio as well as number of geogrid layers. The bearing capacity for the soil increases with an average of 12.35% using H/B equal to0.5 and the bearing capacity increases with an average of 35.76%, 75.56% & 230.83% while using H/B equal to 1.0, 1.5 & 2.0. It also found that the use of sandy layers over flyash mixed clayey soil has a considerable effect on the bearing capacity characteristics and the use of geogrid layers in the granular overlay has remarkable effect on Bearing capacity ratio (BCR & Settlement reduction ratio (SRR.
Effect of Embedment on the Vertical Bearing Capacity of Bucket Foundations in Clay
Barari, Amin; Ibsen, Lars Bo
2011-01-01
To evaluate the undrained behaviour of bucket foundations installed on Yoldia clay, 100 tests on bucket foundations subject to vertical and moment loadings were conducted at Aalborg university geotechnical centre. Bucket foundations are tubular steel foundations that are installed by sealing the...... top and applying suction inside the bucket. The hydrostatic pressure difference and the deadweight cause the bucket to penetrate the soil. In the present study, results of an experimental study addressing the effect of embedment (skirt length to the diameter) on the undrained bearing capacity of...... bucket foundations under vertical loading are reported. The field tests have been accompanied by the finite element numerical simulations in order to provide better understanding of influential parameters on the behavior of bucket foundations....
Guo, Ke; Wang, Li-qun
2015-12-01
Based on the evaluation index system established for measuring the resource environmental bearing capacity (REBC), this paper measured the REBC of Beijing-Tianjin-Hebei region by applying the state space model and analyzed their driving factors by using the Tobit model. The results showed that the REBC of Beijing-Tianjin-Hebei region was in the available state and at the rising stage as well during 2000-2012. The social economic growth had great pressure on the resources and environment. The bearing ratios of the REBCs of Beijing, Tianjin and Hebei all presented a U curve and located at low levels, which meant that there was high REBC potential in these regions. Both of the permanent population and the urban residents 'Engel' s coefficient were the influence factors of the REBC of Beijing-Tianjin-Hebei region. The population problem was likely to become the bottleneck to restrict the regional social and economic development, and also threaten the resources and environment. The specific driving factors of the REBC were different in Beijing, Tianjin and Hebei. For example, energy consumption per unit of GDP only had significant impact on Tianjin. At last, the paper proposed that the three regions should complement each other in resources and environment, social development, and economic structure, also the REBC should be taken a reference in decision and policy making. PMID:27112024
Zhang, Yongfang; Wu, Peng; Guo, Bo; Lü, Yanjun; Liu, Fuxi; Yu, Yingtian
2015-01-01
The instability of the rotor dynamic system supported by oil journal bearing is encountered frequently, such as the half-speed whirl of the rotor, which is caused by oil film lubricant with nonlinearity. Currently, more attention is paid to the physical characteristics of oil film due to an oil-lubricated journal bearing being the important supporting component of the bearing-rotor systems and its nonlinear nature. In order to analyze the lubrication characteristics of journal bearings efficiently and save computational efforts, an approximate solution of nonlinear oil film forces of a finite length turbulent journal bearing with couple stress flow is proposed based on Sommerfeld and Ocvirk numbers. Reynolds equation in lubrication of a finite length turbulent journal bearing is solved based on multi-parametric principle. Load-carrying capacity of nonlinear oil film is obtained, and the results obtained by different methods are compared. The validation of the proposed method is verified, meanwhile, the relationships of load-carrying capacity versus eccentricity ratio and width-to-diameter ratio under turbulent and couple stress working conditions are analyzed. The numerical results show that both couple stress flow and eccentricity ratio have obvious influence on oil film pressure distribution, and the proposed method approximates the load-carrying capacity of turbulent journal bearings efficiently with various width-to-diameter ratios. This research proposes an approximate solution of oil film load-carrying capacity of turbulent journal bearings with different width-to-diameter ratios, which are suitable for high eccentricity ratios and heavy loads.
ZHANG Yongfang; WU Peng; GUO Bo; L Yanjun; LIU Fuxi; YU Yingtian
2015-01-01
The instability of the rotor dynamic system supported by oil journal bearing is encountered frequently, such as the half-speed whirl of the rotor, which is caused by oil film lubricant with nonlinearity. Currently, more attention is paid to the physical characteristics of oil film due to an oil-lubricated journal bearing being the important supporting component of the bearing-rotor systems and its nonlinear nature. In order to analyze the lubrication characteristics of journal bearings efficiently and save computational efforts, an approximate solution of nonlinear oil film forces of a finite length turbulent journal bearing with couple stress flow is proposed based on Sommerfeld and Ocvirk numbers. Reynolds equation in lubrication of a finite length turbulent journal bearing is solved based on multi-parametric principle. Load-carrying capacity of nonlinear oil film is obtained, and the results obtained by different methods are compared. The validation of the proposed method is verified, meanwhile, the relationships of load-carrying capacity versus eccentricity ratio and width-to-diameter ratio under turbulent and couple stress working conditions are analyzed. The numerical results show that both couple stress flow and eccentricity ratio have obvious influence on oil film pressure distribution, and the proposed method approximates the load-carrying capacity of turbulent journal bearings efficiently with various width-to-diameter ratios. This research proposes an approximate solution of oil film load-carrying capacity of turbulent journal bearings with different width-to-diameter ratios, which are suitable for high eccentricity ratios and heavy loads.
Agergaard, Frederik Ancker; Ingeman-Nielsen, Thomas
The bearing capacity of frozen soils is high, compared to non-frozen soils of same composition. Projected climatic warming in the Arctic will increase the soil temperature, thus affecting the bearing capacity and the deformation properties. Western Greenland temperatures are projected to increase...... from the Western Greenland towns of Sisimiut and Ilulissat respectively. Tests reveal undrained shear strengths ranging from 409 kPa to 940 kPa, where low temperatures and low excess ice content yield higher strengths. Normalized strengths are used for establishing a trend for the strength decrease...
Agergaard, Frederik Ancker; Ingeman-Nielsen, Thomas
2012-01-01
The bearing capacity of frozen soils is high, compared to non-frozen soils of same composition. Projected climatic warming in the Arctic will increase the soil temperature, thus affecting the bearing capacity and the deformation properties. Western Greenland temperatures are projected to increase...... excess ice free samples. Unfrozen water contents are seen to be directly inversely proportional to the undrained shear strength when both are normalized, which may reduce costs for establishing reliable soil strength parameters. It is suggested that a relation to deformation parameters are investigated...
Tamrazyan Ashot Georgievich
2012-10-01
Full Text Available Accurate and adequate description of external influences and of the bearing capacity of the structural material requires the employment of the probability theory methods. In this regard, the characteristic that describes the probability of failure-free operation is required. The characteristic of reliability means that the maximum stress caused by the action of the load will not exceed the bearing capacity. In this paper, the author presents a solution to the problem of calculation of structures, namely, the identification of reliability of pre-set design parameters, in particular, cross-sectional dimensions. If the load distribution pattern is available, employment of the regularities of distributed functions make it possible to find the pattern of distribution of maximum stresses over the structure. Similarly, we can proceed to the design of structures of pre-set rigidity, reliability and stability in the case of regular load distribution. We consider the element of design (a monolithic concrete slab, maximum stress S which depends linearly on load q. Within a pre-set period of time, the probability will not exceed the values according to the Poisson law. The analysis demonstrates that the variability of the bearing capacity produces a stronger effect on relative sizes of cross sections of a slab than the variability of loads. It is therefore particularly important to reduce the coefficient of variation of the load capacity. One of the methods contemplates the truncation of the bearing capacity distribution by pre-culling the construction material.
The vast depression in the east Tom-Kolyvan folded zone (West Siberia) has been identified by the geophysical data. The well which uncovered 4000 m deep profile of the Jurassic and Paleozoic deposits has been drilled. The relevance of the research is the oil/gas-bearing capacity evaluation of the discovered depression in this West Siberia area
Esteruelas, Núria Fandos; Huber, Nikolaus; Evans, Alina L; Zedrosser, Andreas; Cattet, Marc; Palomares, Francisco; Angel, Martine; Swenson, Jon E; Arnemo, Jon M
2016-04-01
Brown bears (Ursus arctos) are often captured and handled for research and management purposes. Although the techniques used are potentially stressful for the animals and might have detrimental and long-lasting consequences, it is difficult to assess their physiological impact. Here we report the use of the leukocyte coping capacity (LCC) technique to quantify the acute stress of capture and handling in brown bears in Scandinavia. In April and May 2012 and 2013, we collected venous blood samples and recorded a range of physiological variables to evaluate the effects of capture and the added impact of surgical implantation or removal of transmitters and sensors. We studied 24 brown bears, including 19 that had abdominal surgery. We found 1) LCC values following capture were lower in solitary bears than in bears in family groups suggesting capture caused relatively more stress in solitary bears, 2) ability to cope with handling stress was better (greater LCC values) in bears with good body condition, and 3) LCC values did not appear to be influenced by surgery. Although further evaluation of this technique is required, our preliminary results support the use of the LCC technique as a quantitative measure of stress. PMID:26845299
Load bearing capacity of bone anchored fiber-reinforced composite device.
Ballo, Ahmed Mansour; Lassila, Lippo V; Vallittu, Pekka K; Närhi, Timo O
2007-10-01
The purpose of this study was to evaluate the push-out load-bearing capacity of threaded fiber-reinforced composite (FRC) devices for use as bone-anchored devices. The purpose was also to evaluate the possibility to use bioactive glass (BAG) granules on the experimental FRC devices in terms the mechanical behavior. Three experimental FRC devices (n = 15) were fabricated for the study: (a) threaded device with smooth surface; (b) threaded device with BAG granules (S53P4, Vivoxid Ltd, Turku, Finland) and supplementary retention grooves, and (c) unthreaded device with BAG granules. Threaded titanium devices were used as controls. The FRC devices were prepared from a light-polymerized dimethacrylate resin reinforced with preimpregnated unidirectional and bidirectional E-glass fibers (EverStick, StickTech Ltd, Turku, Finland). Experimental and control devices were embedded into dental plaster to simulate bone before the mechanical push-out test was carried out. ANOVA and Weibull analysis were used for the statistical evaluation. Threaded FRC devices had significantly higher push-out strength than the threaded titanium device (p < .001). The push-out forces exceeding 2,500 N were measured for threaded FRC devices with supplementary grooves and BAG coating. No thread failures were observed in any FRC devices. The unthreaded FRC devices with BAG lost 70% of glass particles during the test, while no BAG particles were lost from threaded FRC devices. It can be concluded that threaded FRC devices can withstand high push-out forces in the dental plaster without a risk of thread failure under physiological load. PMID:17558473
Li-yi ZHANG
2013-07-01
Full Text Available Objective To explore the relationship between the psychological bearing capacity and trait coping style of military chauffeurs, and explore their influencing factors. Methods By random cluster sampling, a total of 390 military drivers (experimental group and 396 military non-drivers (control group were chosen as subjects, and they were investigated with the Military Personnel Resilience Scale (MPRS and Trait Coping Styles Questionnaire (TCSQ. The relationship between the psychological bearing capacity and trait coping style, and the influencing factors were analyzed. Descriptive statistics, independent sample t-test, correlation analysis and multiple stepwise regression analysis were performed by SPSS 17.0 software. Results Compared to the control group, the scores of problem-solving, will power, self-confidence and the total score of MPRS were higher in experimental group (P<0.01 or 0.05. Correlation analysis suggested all the factors of MPRS in the drivers were positively correlated with positive coping style (P<0.01 or 0.05 and negatively correlated with negative coping style (P<0.01; the will power was positively correlated with educational level (P<0.05. Multiple stepwise regression analysis indicated that both the positive and negative coping style were incorporated into the regression equation with problem-solving, will power, interpersonal relationship, self-confidence and total score of MPRS as the dependent variables (P<0.01; negative coping style was incorporated into the regressive equation with family support as the dependent variables (P<0.01 and educational level was incorporated into the regressive equation with will power as the dependent variables (P<0.01. Conclusions The military drivers show a stronger psychological bearing capacity, and the major factor is trait coping style. In addition, educational level may affect the will power, so it may be regarded as a reference on psychological intervention to improve the
Zhu, Aibin; Li, Pei; Zhang, Yefan; Chen, Wei; Yuan, Xiaoyang
2015-04-01
Ultra-high speed machining technology enables high efficiency, high precision and high integrity of machined surface. Previous researches of hybrid bearing rarely consider influences of solid particles in lubricant and ultra-high speed of hybrid bearing, which cannot be ignored under the high speed and micro-space conditions of ultra-high speed water-lubricated hybrid bearing. Considering the impact of solid particles in lubricant, turbulence and temperature viscosity effects of lubricant, the influences of particles on pressure distribution, loading capacity and the temperature rise of the lubricant film with four-step-cavity ultra-high speed water-lubricated hybrid bearing are presented in the paper. The results show that loading capacity of the hybrid bearing can be affected by changing the viscosity of the lubricant, and large particles can improve the bearing loading capacity higher. The impact of water film temperature rise produced by solid particles in lubricant is related with particle diameter and minimum film thickness. Compared with the soft particles, hard particles cause the more increasing of water film temperature rise and loading capacity. When the speed of hybrid bearing increases, the impact of solid particles on hybrid bearing becomes increasingly apparent, especially for ultra-high speed water-lubricated hybrid bearing. This research presents influences of solid particles on the loading capacity and the temperature rise of water film in ultra-high speed hybrid bearings, the research conclusions provide a new method to evaluate the influence of solid particles in lubricant of ultra-high speed water-lubricated hybrid bearing, which is important to performance calculation of ultra-high speed hybrid bearings, design of filtration system, and safe operation of ultra-high speed hybrid bearings.
ZHU Aibin; LI Pei; ZHANG Yefan; CHEN Wei; YUAN Xiaoyang
2015-01-01
Ultra-high speed machining technology enables high efficiency, high precision and high integrity of machined surface. Previous researches of hybrid bearing rarely consider influences of solid particles in lubricant and ultra-high speed of hybrid bearing, which cannot be ignored under the high speed and micro-space conditions of ultra-high speed water-lubricated hybrid bearing. Considering the impact of solid particles in lubricant, turbulence and temperature viscosity effects of lubricant, the influences of particles on pressure distribution, loading capacity and the temperature rise of the lubricant film with four-step-cavity ultra-high speed water-lubricated hybrid bearing are presented in the paper. The results show that loading capacity of the hybrid bearing can be affected by changing the viscosity of the lubricant, and large particles can improve the bearing loading capacity higher. The impact of water film temperature rise produced by solid particles in lubricant is related with particle diameter and minimum film thickness. Compared with the soft particles, hard particles cause the more increasing of water film temperature rise and loading capacity. When the speed of hybrid bearing increases, the impact of solid particles on hybrid bearing becomes increasingly apparent, especially for ultra-high speed water-lubricated hybrid bearing. This research presents influences of solid particles on the loading capacity and the temperature rise of water film in ultra-high speed hybrid bearings, the research conclusions provide a new method to evaluate the influence of solid particles in lubricant of ultra-high speed water-lubricated hybrid bearing, which is important to performance calculation of ultra-high speed hybrid bearings, design of filtration system, and safe operation of ultra-high speed hybrid bearings.
Hertzian Load-bearing Capacity of Hybrid and Nano-hybrid Resin Composites Stored Dry and Wet
Farmani S
2016-03-01
Full Text Available Statement of Problem: Hertzian indentation test has been proven to be an efficient and reliable alternative upon Vickers hardness test. This method has been used to test dental ceramics, amalgams, glass ionomers and luting cements.There is limited published information about the load-bearing capacity of resin composites using Hertizian indentation test. Objectives: To investigate the load-bearing capacity of hybrid and nano-hybrid resin composites stored dry or wet up to 30 days, using Hertzian indentation test. Materials and Methods: Three resin composites were used: two nano-hybrids (Filtek Supreme, and Luna and one hybrid, (Rok. A total of 108 disc-shaped specimens (1mm thick x 10 mm diameter were prepared using polyethylene mould. The specimens of each material were randomly divided into 6 groups of 6 (n=6 and stored at 370C either in distilled water or dry for 1, 7 and 30 days. The specimens were tested using Hertzian jig aligned in the universal testing machine. The specimen was placed on the top of a disc-shaped substrate. The load was applied at the center of each specimen and the load at the first crack was recorded. Data were analyzed by ANOVA, Tukey’sand student’s t-test using SPSS version 18.0. Results: Three-way ANOVA showed a significant interaction between all the factors (p = .0001. The load bearing capacity of almost all materials reduced significantly in the wet condition in comparison with the dry condition (p = .0001. After seven days of immersion in distilled water, Filtek Supreme had significantly lower values than those of Rok and Luna, there was no significant differences between materials in the dry condition. Conclusions:In contrast to dry condition, the load-bearing capacity of specimens stored in distilled water decreased significantly over the 30 days of immersion. The load bearing capacity of nano-hybrid composites tested in this study was shown to be comparable with that of the hybrid composite.
无
2008-01-01
This paper presents two kinematic failure mechanisms of three-dimensional rectangular footing resting on homogeneous undrained clay foundation under uniaxial vertical loading and uniaxial moment loading. The failure mechanism under vertical loading comprises a plane strain Prandtl-type mechanism over the central part of the longer side, and the size of the mechanism gradually reduces at the ends of the longer side and over the shorter side as the corner of rectangular footing is being approached where the direction of soil motion remains normal to each corresponding side respectively. The failure mechanism under moment loading comprises a plane strain scoop sliding mechanism over the central part of the longer side, and the radius of scoop sliding mechanism increases linearly at the ends of the longer side. On the basis of the kinematic failure mechanisms mentioned above, the vertical ultimate bearing capacity and the ultimate bearing capacity against moment or moment ultimate bearing capacity are obtained by use of upper bound limit analysis theory. At the same time, numerical analysis results, Skempton's results and Salgado et al.'s results are compared with this upper bound solution. It shows that the presented failure mechanisms and plastic limit analysis predictions are validated. In order to investigate the behaviors of undrained clay foundation beneath the rectangular footing subjected to the combined loadings, numerical analysis is adopted by virtue of the general-purpose FEM software ABAQUS, where the clay is assumed to obey the Mohr-Coulomb yielding criterion. The failure envelope and the ultimate bearing capacity are achieved by the numerical analysis results with the varying aspect ratios from length L to breadth B of the rectangular footing. The failure mechanisms of rectangular footing which are subjected to the combined vertical loading V and horizontal loading H (Vertical loading V and moment loading M, and horizontal loading H and moment loading M
Determination of Load Bearing Capacity for Spatial Joint with Steel Angle Brackets
Sejkot, P.; Ormarsson, S.; Vessby, J.; Kuklík, P.
2015-11-01
The design of spatial connections in load bearing timber structures with steel angle brackets has insufficient support in the existing design standards. Therefore, research has been necessary to improve this state of the art. In the current paper an experimental study on two designs of angle brackets is presented and the results from full-scale experiments are compared to numerical and analytical computational models.
Wang, Junjun; Pu, Jibin; Zhang, Guangan; Wang, Liping
2013-06-12
Superthick diamond-like carbon (DLC) films [(Six-DLC/Siy-DLC)n/DLC] were deposited on 304 stainless steel substrates by using a plane hollow cathode plasma-enhanced chemical vapor deposition method. The structure was investigated by scanning electron microscopy and transmission electron microscopy. Chemical bonding was examined by Raman, Auger electron, and X-ray photoelectron spectroscopy techniques. Mechanical and tribological properties were evaluated using nanoindentation, scratch, interferometry, and reciprocating-sliding friction testing. The results showed that implantation of a silicon ion into the substrate and the architecture of the tensile stress/compressive stress structure decreased the residual stress to almost 0, resulting in deposition of (Six-DLC/Siy-DLC)n/DLC films with a thickness of more than 50 μm. The hardness of the film ranged from 9 to 23 GPa, and the adhesion strength ranged from 4.6 to 57 N depending on the thickness of the film. Friction coefficients were determined in three tested environments, namely, air, water, and oil. Friction coefficients were typically below 0.24 and as low as 0.02 in a water environment. The as-prepared superthick films also showed an ultrahigh load-bearing capacity, and no failure was detected in the reciprocating wear test with contact pressure higher than 3.2 GPa. Reasons for the ultrahigh load-bearing capacity are proposed in combination with the finite-element method. PMID:23668472
Kawa Marek
2015-12-01
Full Text Available The paper deals with reliability analysis of square footing on soil with strength anisotropy. The strength of the soil has been described with identified anisotropic strength criterion dedicated to geomaterials with layered microstructure. The analysis assumes dip angle α and azimuth angle β which define direction of lamination of the structure to be random variables with given probability density functions. Bearing capacity being a function of these variables is approximated based on results of deterministic simulations obtained for variety of orientations. The weighted regression method by Kaymaz and McMahon within the framework of Response Surface Method is used for the approximation. As a result of analysis, global factor of safety that corresponds to assumed value of probability of failure is determined. The value of the safety factor denotes the ratio between the value of the design load and the mean value of bearing capacity which is needed to reduce the probability of failure to the acceptable level. The procedure of calculating the factor has been presented for two different cases. In the first case, no information about lamination direction of the soil has been provided and thus all the orientations are assumed to be equally probable (uniform distribution. In the second case, statistical information including mean, variance and assumed probability distribution for both α and β angle is known. For the latter case, using results obtained for few different values of mean of angle α, also the influence of strength anisotropy on the value of global factor of safety is shown.
LUAN Mao-tian; FAN Qing-lai
2006-01-01
Presented in this paper is a three-dimensional plastic limit analysis method of bearing capacity of the deeply-embedded large-diameter cylindrical structure in the cross-anisotropic soft ground. The most likely failure mechanism is assumed to be of a composite rupture surface which is composed of an individual wedge in the passive zone or two wedges in both active and passive zones near the mudline, depending on the separation or bonding state at the interface between the cylindrical structure and neighboring soils in the active wedge, and a truncated spherical slip surface at the base of the cylinder when the structure tends to overturn around a point located on the symmetry axis of the structure. The cylindrical structure and soil interaction system under consideration is also numerically analyzed by the finite element method by virtue of the general-purpose FEM software ABAQUS, in which the soil is assumed to obey tie Hill's criterion of yield. Both the failure mechanism assumed and the plastic limit analysis predictions are validated by numerical computations based on FEM. For the K0-consolidated ground of clays typically with anisotropic undrained strength property, it is indicated through a parametric study that limit analysis without consideration of anisotropy of soil overestimates the lateral ultimate bearing capacity of a deeply-embedded cylindrical structure in soft ground in a certain condition.
Improvement of Bearing Capacity in Recycled Aggregates Suitable for Use as Unbound Road Sub-Base
Laura Garach; Mónica López; Francisco Agrela; Javier Ordóñez; Javier Alegre; José Antonio Moya
2015-01-01
Recycled concrete aggregates and mixed recycled aggregates are specified as types of aggregates with lower densities, higher water absorption capacities, and lower mechanical strength than natural aggregates. In this paper, the mechanical behaviour and microstructural properties of natural aggregates, recycled concrete aggregates and mixed recycled aggregates were compared. Different specimens of unbound recycled mixtures demonstrated increased resistance properties. The formation of new ceme...
Improvement of Bearing Capacity in Recycled Aggregates Suitable for Use as Unbound Road Sub-Base
Laura Garach
2015-12-01
Full Text Available Recycled concrete aggregates and mixed recycled aggregates are specified as types of aggregates with lower densities, higher water absorption capacities, and lower mechanical strength than natural aggregates. In this paper, the mechanical behaviour and microstructural properties of natural aggregates, recycled concrete aggregates and mixed recycled aggregates were compared. Different specimens of unbound recycled mixtures demonstrated increased resistance properties. The formation of new cement hydrated particles was observed, and pozzolanic reactions were discovered by electronon microscopy in these novel materials. The properties of recycled concrete aggregates and mixed recycled aggregates suggest that these recycled materials can be used in unbound road layers to improve their mechanical behaviour in the long term.
This paper presents the analysis of the Inner Containment Structure (ICS) of a typical 540 MWe Indian PHWR for the purpose of evaluating its ultimate load bearing capacity (ULBC) under beyond postulated design basis accident (DBA) scenario. The methodology adopted for the non-linear analysis of the prestressed concrete ICS including the various issues, viz. behaviour of concrete under compression and tension, tension stiffening, cracked shear modulus etc. have also been discussed in this paper. The effect of accident temperature on ULBC has been studied and discussed in this paper. This paper also discusses about the study carried out for mesh sensitivity of the finite element (FE) discretization on ULBC of ICS in the non-linear range. Based on the detailed analysis, the factor of safety of the ICS under beyond postulated DBA scenario has been evaluated. (author)
We report a very simple and unique strategy for synthesis of a tertiary amine functionalized high surface area porous organic polymer (POP) PDVTA-1 through the co-polymerization of monomers divinylbenzene (DVB) and triallylamine (TAA) under solvothermal reaction conditions. Two different PDVTA-1 samples have been synthesized by varying the molar ratio of the monomers. The porous polymeric materials have been thoroughly characterized by solid state 13C CP MAS-NMR, FT-IR and UV–vis spectroscopy, N2 sorption, HR TEM and FE SEM to understand its chemical environment, nanostructure, bonding, morphology and related surface properties. PDVTA-1 with higher amine content (DVB/TAA=4.0) showed exceptionally high CO2 uptake capacity of 85.8 wt% (19.5 mmol g−1) at 273 K and 43.69 wt% (9.93 mmol g−1) at 298 K under 3 bar pressure, whereas relatively low amine loaded material (DVB/TAA=7.0) shows uptake capacity of 59.2 wt% (13.45 mmol g−1) at 273 K and 34.36 wt% (7.81 mmol g−1) at 298 K. Highly porous nanostructure together with very high surface area and basicity at the surface due to the presence of abundant basic tertiary amine N-sites in the framework of PDVTA-1 could be responsible for very high CO2 adsorption. - Graphical abstract: Exceptionally high CO2 uptake (85.8 wt % at 273 K) has been observed over a high surface area porous organic polymer PDVTA-1 synthesized through copolymerization of divinylbenzene and triallyl amine. - Highlights: • Designing the synthesis of a new N-rich cross-linked porous organic polymer PDVTA-1. • PDVTA-1 showed mesoporosity with very high surface area of 903 m2 g−1. • High surface area and presence of basic sites facilitates the CO2 uptake. • PDVTA-1 showed exceptionally high CO2 adsorption capacity of 85.8 wt% at 273 K, 3 bar pressure
Analysis of the Ultimate Bearing Capacity of Oil Field Drilling Masts%在役钻机井架极限承载性能分析
韩东颖; 周国强; 李子丰
2005-01-01
In order to improve the safety of drilling operations, this paper presents a new method for forecasting the ultimate bearing capacity of oil field drilling masts. The method is based on a double nonlinear finite element theory and applies a referential stress method for measuring defects and defacements. The lab mast model was analyzed using the proposed method. The relative error, which was less than 5.0% between the forecast results and the destructive experiment values,verified the correctness of this method. It also forecasts the ultimate bearing capacity for a local drilling mast.
Screw anchor used in closure work and its bearing capacity%堵口用螺旋锚及其承载力
汪滨; 洪晓林; 陈基成
2001-01-01
The bearing capacity mechanism and affecting factors of screw anchors are described. Laboratory experiments show that the anti-lifting force and horizontal bearing capacity of screw anchors are higher than those of steel pipes with the same diameter. Modified screw anchors are suitable to the closure work.%分析了螺旋锚的承载机理和影响其承载力的因素.室内试验表明,螺旋锚的抗拔力和水平承载力优于同杆径的钢管.经改进的螺旋锚适用于堵口抢险工程.
Analysis on Bearing Capacity of Tunnel-Type Anchorage of a Long-Span Suspension Bridge
Zhu Yu; Wei Jun; Yang Manjuan; Li Hao; Liu Hongqing
2005-01-01
Due to complicated rock structure and environment, a prototype test for a tunnel-type anchorage is infeasible. Based on the rock mass parameters from tests, a three-dimensional (3D) elasto-plastic analysis was performed to simulate the influence of the construction procedure of Siduhe bridge with tunnel-type anchorage (TTA) in Hubei Province, China. The surrounding rock and concrete anchorage body were simulated by 8 nodes 3D brick elements. The geostatic state of the complex geometric structure was established with initial data. The in-situ concrete casting of the anchorage body and excavation of the rock mass were simulated by tetrahedral shell elements. The results show that the surrounding rock is in an elastic state under the designed cable force. The numerical overloading analysis indicates that the capacity of the surrounding anchorage is 7 times that of the designed cable force. The failure pattern shows that two anchorage bodies would be pulled out in the end. The maximum shear stress appears 10 m before the back anchorage face. The maximum range influenced by the TTA under ultimate loads is about 16 m.
Antonio Higino Frederico Pereira
2015-12-01
Full Text Available ABSTRACT The expansion of the sugarcane industry in Brazil has intensified the mechanization of agriculture and caused effects on the soil physical quality. The purpose of this study was to evaluate the limiting water range and soil bearing capacity of a Latossolo Vermelho distroférrico típico (Rhodic Hapludox under the influence of different tractor-trailers used in mechanical sugarcane harvesting. The experiment was arranged in a randomized block design with five replications. The treatments consisted of green sugarcane harvesting with: harvester without trailer (T1; harvester with two trailers with a capacity of 10 Mg each (T2; harvester with trailer with a capacity of 20 Mg (T3 and harvester and truck with trailer with a capacity of 20 Mg (10 Mg per compartment (T4. The least limiting water range and soil bearing capacity were evaluated. The transport equipment to remove the harvested sugarcane from the field (trailer at harvest decreased the least limiting water range, reducing the structural soil quality. The truck trailer caused the greatest impact on the soil physical properties studied. The soil load bearing capacity was unaffected by the treatments, since the pressure of the harvester (T1 exceeded the pre-consolidation pressure of the soil.
拱撑门架承载力试验及有限元分析%EXPERIMENTS AND FEM ANALYSIS FOR BEARING CAPACITY OF ARCH SUPPORT PORTALFRAME
阎奇武; 黄伟; 杨承惁; 杨棣柔; 陈杰刚
2012-01-01
为确定单榀拱撑内门架承载力,进行拱撑门架和MF1219门架承载力非线性有限元分析和拱撑门架承载力试验。利用ANSYS软件建立拱撑门架模型和MF1219门架模型,进行特征值屈曲分析,得到各计算模型的承载力。拱撑门架立杆低端铰接,在两立杆上端或上横杆拱形加强杆两端对应位置处进行分级竖向加载,进行了8榀拱撑门架承载力试验。选择JGJ 128—2010《建筑施工门式钢管脚手架安全技术规范》中门架承载力公式进行了单榀拱撑门架承载力计算,并对门架承载力有限元分析、试验和公式计算结果进行了比较。建议：拱撑门架宜立杆直接受力,拱撑门架立杆受力承载力可采用JGJ 128—2010中5.2.1-8a计算,拱撑门架上端横杆受力承载力折减系数宜取0.3。%In order to determine the bearing capacity of single arch support inner portalframe,experiments on the bearing capacity of single arch support portalframe and nonlinear FEM analysis of the bearing capacity of single arch support portalframe and single MF1219 portalframe were carried out.Models of single arch support portalframe and single MF1219 portalframe were set up using ANSYS software,their eigenvalue buckling analysis was done,and their bearing capacity was obtained.Loading in grades on top ends of two uprights or the corresponding positions of both ends of the arch strengthened rod of single arch support portalframe,in which low ends of two uprights were articulated,8 single arch support portalframes bearing capacity tests were conducted.Different portalframe bearing capacity formula in JGJ 128—2010 Technical Code of Portal Steel Pipe Scalffold for Building Construction was selected,and the single arch support bearing capacity was calculated.After the results of FEM analysis,experiment and calculation of bearing capacity of single portalframe were contrasted,it was proposed that forces should act on top ends of two uprights
T.V. Nazmeeva
2013-08-01
Full Text Available Nowadays there is steady rising demand for thin-walled light-weight steel structures. But the shortage of relevant standards on their design and use taking into account Russian conditions leads to the current situation when thin-walled light-weight steel structures are used according to the recommended guidelines of thin-walled structures’ producers. The author performed numerical and experimental investigations on general stability and bearing capacity of members of different length which are made of C-shaped profile and C-shaped perforated profile. The main aim of the investigations was to receive a reliable engineering methodology of their calculation. The author developed the testing methodology and designed two test beds С-12 (1200mm/20t and В-50 (2200mm/50t to perform the experimental investigation. Numerical solution for stability of thin-walled member made of C-shaped profile was received during the numerical simulation done in PLM Femap 10.1 Nastran. Subsequently the processing of research results will be continued in order to get the corresponding dependences for development of method for calculating thin-walled members under compression.
DellaCorte, Christopher; Moore, Lewis E., III; Clifton, Joshua S.
2014-01-01
Static load capacity is a critical design parameter for rolling element bearings used in space mechanisms because of the potential for Brinell (surface dent) damage due to shock and vibration loading events during rocket launch. Brinell damage to bearing raceways can lead to torque variations (noise) and reduced bearing life. The growing use of ceramic rolling elements with high stiffness in hybrid bearings exacerbates the situation. A new family of hard yet resilient materials based upon nickel-titanium is emerging to address such bearing challenges. 60NiTi is a superelastic material that simultaneously exhibits high hardness and a relatively low elastic modulus (approx. 100 GigaPascals) and has been shown to endure higher indentation loads than conventional and high performance steel. Indentation load capacity has been reported for relatively large (12.7 millimeters diameter) ceramic (Si3N4) indenter balls pressed against flat plates of 60NiTi. In order to develop damage load threshold criteria applicable to a wide range of bearing designs and sizes, the effects of indenter ball radius and the accuracy of interpolation of the Hertz contact stress relations for 60NiTi must be ascertained. In this paper, results of indentation tests involving ceramic balls ranging from 6.4 to 12.7 mm in diameter and highly polished 60NiTi flat plates are presented. When the resulting dent depth data for all the indenter ball sizes are normalized using the Hertz equations, the data (dent depth versus stress) are comparable. Thus when designing bearings made from 60NiTi, the Hertz stress relations can be applied with relative confidence over a range of rolling element sizes and internal geometries.
HRBF500钢筋混凝土柱轴压试验研究%EXPERIMENT ON BEARING CAPACITY OF REINFORCED CONCRETE COLUMN WITH HRBF500
杨勇新; 赵进阶; 岳清瑞; 廉杰
2009-01-01
对7个配置HRBF500级钢筋混凝土柱进行轴压试验,研究不同混凝土强度、配筋率、长细比等参数下构件的破坏形态、承载力.结果表明,配置HRBF500级钢筋混凝土柱的承载力按照目前规范公式计算是可行的.%The experiment on 7 columns with HRBF500 under axial load was done, whose failure mode and bearing capacity subjected to different parameters such as concrete strength, ratio of reinforcement and slenderness ratio have been studied. The results show that the bearing capacity of reinforced concrete short column with HRBF500 is feasible according to the current code.
大尺寸钢管混凝土柱承载力试验%Bearing Capacity Test of Large Size Concrete Filled Steel Tubular Column
陈彦江; 李勇; 闫维明; 潘迪
2011-01-01
为了探讨大尺寸钢管混凝土柱的初始偏心和开洞插管初始缺陷对其承载力的影响规律,以某钢管混凝土拱桥主拱肋Φ1 200×24 mm钢管为原型,采用1∶2.4,1∶4.8两种几何比例尺分别制作了长径比为3∶1的钢管混凝土柱试件,进行了轴压和偏压试验,并将承载力试验结果与中国现行相关规范的承载力计算结果进行了对比。结果表明：钢管混凝土柱的承载力试验值均大于规范计算值,大尺寸试件和小尺寸试件轴压承载力与规范的比值相差不大,但是大尺寸试件的屈服应力较高,开洞插管的试件由于内插钢管的屈服失效而导致整体试件屈服应力较低;C%In order to study the bearing capacity of large size concrete filled steel tubular（CFST） columns and the influence of initial eccentricity and imperfection of opening hole and insertion pipe on the column,taking a main arch rib Φ1 200×24 mm of a CFST arch bridge as research prototype,authors designed ten CFST column specimens whose draw ratios are 3∶1.According to different scales of 1∶2.4 and 1∶4.8,the axial and eccentric compression tests were carried out,and comparisons on test values and calculated values by several domestic codes for bearing capacity were made.Result shows that test values are all larger than the calculated values for bearing capacity of CFST column,and the ratio of bearing capacity of large size specimen and calculated value is almost same to the ratio of bearing capacity of small size specimen and calculated value.However,yield stress of the large size specimen is larger than that of the small size specimen,and the specimen with opening hole has the smaller yield stress because of the smaller yield stress of the insertion pipe.The calculated values of bearing capacity according to the code CECS 28：90 is closer to the test value,while the safety factor of the bearing capacity calculated by the code DL/T 5085—1999 is the largest
Antonio Higino Frederico Pereira; Antonio Carlos Tadeu Vitorino; Eber Augusto Ferreira do Prado; Anderson Cristian Bergamin; Munir Mauad; Heverton Ponce Arantes
2015-01-01
ABSTRACT The expansion of the sugarcane industry in Brazil has intensified the mechanization of agriculture and caused effects on the soil physical quality. The purpose of this study was to evaluate the limiting water range and soil bearing capacity of a Latossolo Vermelho distroférrico típico (Rhodic Hapludox) under the influence of different tractor-trailers used in mechanical sugarcane harvesting. The experiment was arranged in a randomized block design with five replications. The treatmen...
DITTMER, Marc Philipp; NENSA, Moritz; STIESCH, Meike; KOHORST, Philipp
2013-01-01
Implant-supported screw-retained fixed dental prostheses (FDPs) produced by CAD/ CAM have been introduced in recent years for the rehabilitation of partial or total endentulous jaws. However, there is a lack of data about the long-term mechanical characteristics. Objective The aim of this study was to investigate the failure mode and the influence of extended cyclic mechanical loading on the load-bearing capacity of these frameworks. Material and Methods Ten five-unit FDP frameworks simulating a free-end situation in the mandibular jaw were manufactured according to the I-Bridge®2-concept (I-Bridge®2, Biomain AB, Helsingborg, Sweden) and each was screw-retained on three differently angulated Astra Tech implants (30º buccal angulation/0º angulation/30º lingual angulation). One half of the specimens was tested for static load-bearing capacity without any further treatment (control), whereas the other half underwent five million cycles of mechanical loading with 100 N as the upper load limit (test). All specimens were loaded until failure in a universal testing machine with an occlusal force applied at the pontics. Load-displacement curves were recorded and the failure mode was macro- and microscopically analyzed. The statistical analysis was performed using a t-test (p=0.05). Results All the specimens survived cyclic mechanical loading and no obvious failure could be observed. Due to the cyclic mechanical loading, the load-bearing capacity decreased from 8,496 N±196 N (control) to 7,592 N±901 N (test). The cyclic mechanical loading did not significantly influence the load-bearing capacity (p=0.060). The failure mode was almost identical in all specimens: large deformations of the framework at the implant connection area were obvious. Conclusion The load-bearing capacity of the I-Bridge®2 frameworks is much higher than the clinically relevant occlusal forces, even with considerably angulated implants. However, the performance under functional loading in vivo
Marc Philipp Dittmer
2013-07-01
Full Text Available Implant-supported screw-retained fixed dental prostheses (FDPs produced by CAD/ CAM have been introduced in recent years for the rehabilitation of partial or total endentulous jaws. However, there is a lack of data about the long-term mechanical characteristics. OBJECTIVE: The aim of this study was to investigate the failure mode and the influence of extended cyclic mechanical loading on the load-bearing capacity of these frameworks. MATERIAL AND METHODS: Ten five-unit FDP frameworks simulating a free-end situation in the mandibular jaw were manufactured according to the I-Bridge®2-concept (I-Bridge®2, Biomain AB, Helsingborg, Sweden and each was screw-retained on three differently angulated Astra Tech implants (30º buccal angulation/0º angulation/30º lingual angulation. One half of the specimens was tested for static load-bearing capacity without any further treatment (control, whereas the other half underwent five million cycles of mechanical loading with 100 N as the upper load limit (test. All specimens were loaded until failure in a universal testing machine with an occlusal force applied at the pontics. Load-displacement curves were recorded and the failure mode was macro- and microscopically analyzed. The statistical analysis was performed using a t-test (p=0.05. RESULTS: All the specimens survived cyclic mechanical loading and no obvious failure could be observed. Due to the cyclic mechanical loading, the load-bearing capacity decreased from 8,496 N±196 N (control to 7,592 N±901 N (test. The cyclic mechanical loading did not significantly influence the load-bearing capacity (p=0.060. The failure mode was almost identical in all specimens: large deformations of the framework at the implant connection area were obvious. CONCLUSION: The load-bearing capacity of the I-Bridge®2 frameworks is much higher than the clinically relevant occlusal forces, even with considerably angulated implants. However, the performance under functional
Calculation of Bearing Capacity of Geosynthetic-encased Stone Columns%加筋碎石桩承载力计算
赵明华; 陈庆; 张玲; 马缤辉
2011-01-01
The bearing mechanism of composite foundation of geosynthetic-encased stone columns was analyzed, and several kinds of failure mode of the composite foundation were investigated. In different failure modes, according to the limit equilibrium theory, a calculation formula of the ultimate bearing capacity of single geosynthetic-encased stone column was proposed. Failure mode 1 is mainly controlled by the tensile strength of geogrid sleeve, and failure mode 2 is controlled by the pile-lateral friction of geosynthetic-encased stone column and the end bearing capacity of common stone column before the damage of swelling deformation. The example of calculation indicates that the (1) bearing capacity of geosynthetic-encased stone column has significantly improved than that of common stone column; (2) the reinforcing depth of geosynthetic-encased stone column and the tensile strength of geogrid sleeve have a best combination for the most rational using of geogrid to improve the bearing capacity of the stone columa At last, the geosynthetic-encased stone columns were applied to treatment of weak subgrade of expressway.%分析了加筋碎石桩复合地基的承载机理,探讨了加筋碎石桩复合地基的几种破坏模式.在不同的破坏模式下根据极限平衡理论导出了加筋碎石桩单桩极限承载力计算公式,破坏模式1主要由格栅套筒抗拉强度控制,破坏模式2由加筋段桩体侧摩阻力和非加筋段桩体鼓胀破坏前向上提供的端承力共同控制.实例计算表明,加筋碎石桩的承载力比普通碎石桩的承载力有显著提高,且加筋碎石桩的加筋深度与格栅抗拉强度之间有最优组合,最合理地利用加筋格栅提高碎石桩承载力,最后将加筋碎石桩应用到了高速公路软基处治中.
素混凝土柱极限承载力计算方法%Calculation method of ultimate bearing capacity for plain concrete column
林上顺; 陈宝春
2015-01-01
The tests of ultimate bearing capacity for 19 plain concrete columns were carried out. The reasonable scopes of slenderness and eccentricity of plain concrete columns were proposed. The bearing capacities of test columns were calculated by nonlinear finite element method.A calculation method of ultimate bearing capacity for plain concrete column was presented by theoretical analysis and regression of test data. Calculation result shows that when the slendernesses of test columns are higher than 15 and the eccentricities are 0.3,their failure modes are section tensile failure,which can not play full material performance of compression.When the slendernesses are not higher than 15 and the eccentricities are not higher than 0.3,their failure modes are section compression failure.The mean ratio of calculated values by the finite element method to test values is 0.995,the variance is 0.001 8,so the calculated value fits well with test value,and the finite element method can be used for the parameter analysis of plain concrete column.Based on considering the coupling influence of slenderness and eccentricity on bearing capacity,in the proposed calculation method of ultimate bearing capacity,the mean ratio of calculated values by the proposed method and the finite element method is 0.976,the variance is 0.003,which indicates that the proposed method has high precision and high safety.2 tabs, 17 figs,20 refs.%开展了19根素混凝土柱极限承载力试验，提出了素混凝土柱长细比和偏心率的合理取值范围，采用非线性有限元方法对试验柱承载力进行计算，通过理论分析和试验数据回归，提出了素混凝土柱极限承载力计算方法。计算结果表明：当试验柱长细比大于15与偏心率为0．3时，素混凝土柱的破坏模式为截面受拉破坏，未能充分发挥混凝土以受压为主的材料性能；当试验柱长细比不大于15与偏心率不大于0．3时，其破坏模式为截面受压破
Rosecrance, R. C.; Weinbaum, S. A.; Brown, P. H.
1996-01-01
We examined interrelationships between crop load, nitrogen (N), phosphorus (P), and potassium (K) uptake, and root growth in mature, alternate-bearing pistachio (Pistacia vera L.) trees. Pistachio trees bear heavy (on-year) and light (off-year) fruit crops in alternate years. Uptake and partitioning of N, P, and K among tree parts were determined during (a) spring flush (mid-March to late May), (b) nut fill (late May to early September), and (c) postharvest-leaf senescence (late September to early December). Nutrient uptake occurred primarily during nut fill in both on-year and off-year trees. In on-year trees, N and K uptake increased by 35 and 112%, respectively, during nut fill compared with off-year trees. During this period, nutrients were allocated largely to embryo development in on-year trees and to storage in perennial tissues in off-year trees. Nutrient uptake was negligible between harvest and leaf senescence. Although root growth was reduced during nut fill in on-year trees compared with off-year trees, there was no relationship between root growth and the uptake of N, P or K from the soil. Our data support the hypothesis that sink demand regulates the uptake and distribution of N, P, and K in pistachio trees. PMID:14871788
In power plants numerous dissimilar welds exist between ferritic and austenitic components. The evaluation of the influence of real or postulated flaws to the load bearing and failure behaviour in the area of dissimilar welded joints, e. g. in piping of the primary circuit of nuclear power plants, is an essential part of the safety assessment of these plants. The fracture assessment of dissimilar welds containing flaws is therefore an important issue of structural integrity considerations. During the past decades several assessment procedures for the evaluation of flaws in welds have been developed mainly based on methods originally developed for homogenous materials. The main difficulties in applying these methods are that they are restricted to two different materials and the very limited experimental evaluation especially by component tests. To improve the general understanding of the influence of flaws in piping systems with dissimilar welds and to have a more reliable basis for the assessment of the fracture behaviour, full scale tests on pipes containing a weld between ferritic and austenitic steel have been performed. The test results of these tests are summarised and used for the evaluation of analytical and numerical assessment procedures. (orig.)
Numerical simulation of bearing capacity of the bored pile in soft rock%软岩钻孔灌注桩承载力的数值模拟
高长岭; 李荣峰; 柴建峰
2012-01-01
如何确定软岩地区钻孔灌注桩的承载力是一个复杂而又亟待解决的问题.本文以南京长江三桥软岩钻孔灌注桩为例,利用数值模拟法(FLAC3D模拟分析),模拟南京长江三桥软岩钻孔灌注桩逐级加载后的受力性状,根据得到的桩周土岩的应力场、位移场及破坏区的分布和扩展,确定软岩钻孔灌注桩的极限承载力.将数值模拟结果和自平衡测试结果进行比较,笔者发现两者吻合较好.%A method for determining the bearing capacity of bored piles in soft rock areas has been a complex problem that should be solved urgently. Taking the bored piles in soft rock of the third bridge over the Yangtze River in Nanjing as an example and using the numerical simulation method (FLAC3D simulation analysis), this paper simulated the force behavior of the bored piles in soft rock of the third bridge over the Yangtze River in Nanjing in the case of step stress test. Based on stress field, displacement field and the distribution and expansion of the failure zone obtained in the soil and rock around the pile, the authors determined the ultimate bearing capacity of the bored pile in soft rock. A comparison with the numerical simulation results and the self-balanced load test results shows that the numerical simulation result agrees well with the self-balanced load test result.
Gomes, Ruth; Bhaumik, Asim, E-mail: msab@iacs.res.in
2015-02-15
We report a very simple and unique strategy for synthesis of a tertiary amine functionalized high surface area porous organic polymer (POP) PDVTA-1 through the co-polymerization of monomers divinylbenzene (DVB) and triallylamine (TAA) under solvothermal reaction conditions. Two different PDVTA-1 samples have been synthesized by varying the molar ratio of the monomers. The porous polymeric materials have been thoroughly characterized by solid state {sup 13}C CP MAS-NMR, FT-IR and UV–vis spectroscopy, N{sub 2} sorption, HR TEM and FE SEM to understand its chemical environment, nanostructure, bonding, morphology and related surface properties. PDVTA-1 with higher amine content (DVB/TAA=4.0) showed exceptionally high CO{sub 2} uptake capacity of 85.8 wt% (19.5 mmol g{sup −1}) at 273 K and 43.69 wt% (9.93 mmol g{sup −1}) at 298 K under 3 bar pressure, whereas relatively low amine loaded material (DVB/TAA=7.0) shows uptake capacity of 59.2 wt% (13.45 mmol g{sup −1}) at 273 K and 34.36 wt% (7.81 mmol g{sup −1}) at 298 K. Highly porous nanostructure together with very high surface area and basicity at the surface due to the presence of abundant basic tertiary amine N-sites in the framework of PDVTA-1 could be responsible for very high CO{sub 2} adsorption. - Graphical abstract: Exceptionally high CO2 uptake (85.8 wt % at 273 K) has been observed over a high surface area porous organic polymer PDVTA-1 synthesized through copolymerization of divinylbenzene and triallyl amine. - Highlights: • Designing the synthesis of a new N-rich cross-linked porous organic polymer PDVTA-1. • PDVTA-1 showed mesoporosity with very high surface area of 903 m{sup 2} g{sup −1}. • High surface area and presence of basic sites facilitates the CO{sub 2} uptake. • PDVTA-1 showed exceptionally high CO{sub 2} adsorption capacity of 85.8 wt% at 273 K, 3 bar pressure.
Position Effect of Circumferential Crack Defects on Elbow Pipe Bearing Capacity%周向缺陷位置对弯管承载能力的影响
万晋; 秦超
2016-01-01
Taking elbow pipe as the object of study, the finite element method was adopted to investigate axial stress distribution on the cross section of the elbow pipe and plastic limit load;and the stress distribution there under internal pressure and bending load was summarized, including location of the maximum axial stress and its calculation formulation. Analyzing the position effect of circumferential crack defects on the elbow pipe’ s bearing capacity shows that, as for the elbow pipe with smaller bending radius and bigger diameter-thickness ratio, the circumferential crack defect should be located at the spot of the maximal axial stress so as to deter-mine the elbow’ s bearing capacity and lay the foundation for further study of the plastic ultimate bending mo-ment and improvement of elbow failure assessment.%以弯管为研究对象，采用有限元法对弯管中间横截面应力分布规律和塑性极限载荷进行研究，给出了弯管在内压和弯矩载荷下的应力分布情况，指出了弯矩载荷下弯管中间截面最大轴向应力点位置和计算公式，分析了中间截面上不同位置周向裂纹缺陷对弯管塑性极限弯矩载荷的影响。结果表明，对于弯曲半径比较小，径厚比较大的弯管应将周向裂纹缺陷定位在最大轴向应力点确定弯管弯矩承载能力，为进一步研究弯管塑性极限弯矩，完善弯管失效评定奠定基础。
预应力管桩承载力抗拔系数试验分析%Test and Analysis of Prestressed Pipe Pile Bearing Capacity Pull-out Coefficient
陈捷; 周同和; 王会龙
2015-01-01
通过两组8台现场静载荷试验的成果分析和已有试验成果的比较，研究了采用静压和锤击施工的预应力管桩（采用PHC）在黏土与粉土中的承载力抗拔系数。结果表明，受到桩端阻力与桩侧阻力相互作用的影响，桩端位于承载力较高的砂层时，预应力管桩承载力抗拔系数较小，桩端位于桩端阻力较小的黏土层时，预应力管桩承载力抗拔系数较大。土层抗拔系数受长径比影响较大，长径比大的桩，上部土层抗拔系数可能较大；长径比较小时，下部土层抗拔系数可能较大。研究成果可供建筑抗浮工程优化设计作为参考。%By the analysis of two groups of eight field static load test results and the comparison of existing test results,we studied the bearing capacity uplift coefficient of PHC Piles whose construction adopts hydrostatic pressure and hammering in clay and silt. The results show that bearing capacity of pile resistance coefficient is little when the bearing capacity of pile tip into the higher sand layer,the bearing capacity of pile resistance coefficient is larger when we put the pile end into the clay layer of smaller pile side resistance due to the influence of pile end resistance of pile side resistance. The aspect ratio has a great influence on the bearing capacity uplift coefficient of soil layer. When the aspect ratio is larger,the bearing capacity uplift coefficient of soil upper layer is greater than the pile of little aspect ratio;the bearing capacity uplift coefficient of soil lower layer may be greater than the upper soil layer when the pile has small aspect ratio;The research results can be used for reference by the building anti-floating engineering optimization design.
杨胜慧
2013-01-01
The cast-in-place piles foundation is adopted in the Caohe aqueduct body. There is 0.5 meter of the piles foun-dation entering into the weak weathered rock, the bearing capacity of the piles foundation is calculated according to point bearing pile . The static load test is adopted to check the the bearing capacity of the cast-in-place pile foundation, the test results show that the bearing capacity of pile foundation in Caohe aqueduct meet the design requirements.%漕河渡槽槽身段采用灌注桩基础，桩基进入弱风化岩石0.5m，按纯端承桩计算桩基承载力。采用桩基静载试验检测桩基承载力，试验结果表明，漕河渡槽桩基承载力达到设计要求。
Shear Bearing Capacity of Ultra-High Performance Concrete Shear Wall%超高性能混凝土剪力墙抗剪承载力分析
钟益东; 童小龙; 甘文举
2015-01-01
This paper uses nonlinear finite element analysis upon the basic behavior of Ultra -high performance concrete shear wall subjected to monodirectional lateral load, and studies the effect of axial load ratio, shear span ratio, the ratio of hidden column longitudinal, the volumetric ratio of hidden column and the ratio of web reinforcement on the shear bearing capacity. The research shows that: the bearing capacity of UHPC shear wall is high; the displacement ductility of UHPC shear wall is well. With the increased of axial load ratio, the bearing capacity is first increased and then decreased, the ductility drop significantly, so axial load ratio should be strictly controlled; With the shear span ratio increased, the destruction of morphological change and the bearing capacity increase; With the ratio of hidden column longitudinal increasing, the bearing capacity increase; the volumetric ratio of hidden column, the ratio of web horizontal reinforcement and the ratio of web vertical reinforcement effect on bearing capacity are not very obvious.%对超高性能混凝土UHPC(Ultra-High Performance Concrete)剪力墙在单向水平荷载作用下的受力过程进行了非线性有限元分析。重点分析了轴压比、剪跨比、暗柱纵筋配筋率、暗柱箍筋配箍率、分布钢筋配筋率等因素对UHPC剪力墙抗剪承载力的影响。结果表明： UHPC混凝土剪力墙抗剪承载力高，延性较好，值得在工程领域应用。随着轴压比的增大，承载力先增大后减小，延性大幅下降，应该严格控制轴压比；随着剪跨比增大，破坏形态发生变化，承载力减小；随着暗柱纵筋配筋率的增大，承载力增大；暗柱箍筋体积配箍率及分布钢筋的增大对承载力的影响不很明显。
起重吊钩极限承载力试验%Experimental Study of the Ultimate Bearing Capacity of a Lifting Hook
沈超明; 李旭东; 杨绘峰
2013-01-01
The ultimate bearing capacity and safety factor of a large lifting hook was determined by the methods of model test and finite element simulation in the present paper.First,larger stress points,known as dangerous points,are obtained by the method of finite element and mechanical analysis.The similarity relation between the real object and model of lifting hook under the concentrated force was derived based on the model test theory.Then a hook model at a ratio of 4:1 to the original hook was manufactured for different loading tests.Synchronous measurement of the strain of dangerous points was made by using electric resistance strain gauges to get the load which made the model to yield.Finally,the actual ultimate strength and the safety factor of the lifting hook was obtained according to similarity relation.The test results indicate that the lifting hook is safe at the rated condition with a safety factor 1.14 and the proposed method can efficiently determine the actual ultimate bearing capacity of the large lifting hook for its safety and reliability.%利用模型试验与数值计算相结合的方法,测定了某大型起重吊钩的极限承载力及其安全系数.首先,通过有限元计算及力学分析得出其在额定工况下的应力较大点,即危险点；然后应用模型试验理论推导了静态集中力作用下吊钩实物与模型的相似关系,并对按4∶1的比例制作的吊钩模型进行等量逐级加载试验,同时利用电阻应变法对吊钩模型上危险点的应变进行同步测量,计算得到吊钩模型出现局部屈服时的载荷,从而根据相似关系确定了该起重吊钩的实际极限承载力和安全系数.试验结果表明,该起重吊钩在额定工况下是安全的,其安全系数约为1.14；提出的方法可以有效测定大型吊钩的实际极限承载力,以确保大型起重吊钩的安全可靠.
刘正伟; 冯鑫
2014-01-01
依据相关规范对地下车库或地下室常用的独立基础加防水板的基础形式进行了分析，指出独立基础地基承载力特征值可以用规范规定修正后的数值加防水板所抵抗的净水头压力值作为地基承载力最终的特征值。%This paper analyzed the commonly used independent foundation plus waterproof board foundation to underground garage or basement according to relevant norms, pointed out the independent foundation bearing capacity characteristic value could as the foundation bearing capacity final characteristic value using the value modified by specification plus clear water head pressure value resistance of waterproof board clear water.
张麒蛰; 卓卫东; 范立础
2013-01-01
In order to obtain the axial bearing capacity of a batter pile , the calculation formula for the axially bearing capacity of a batter pile was deduced based on the non-uniform distribution char-acteristics of the friction resistance around the batter pile shaft and the mechanism of pile -soil deformation compatibility .The results calculated by the proposed formula and the method given by the design code of pile were compared to explore the influence of the factors , such as pile inclina-tion, diameter, length and utmost friction resistance around pile shaft , on axial bearing capacity. The calculated results showed that the value of the pile axially bearing capacity calculated by the proposed formula decreased with the increase of pile inclination .For different pile diameters , the pile axially bearing capacity was 7%smaller than that calculated by the code's formula.The shorter of the pile length or the lesser of the utmost friction resistance of the pile was , the smaller bearing capacity calculated by the code's formula was than the values calculated by the proposed formula . Finally , with the increase of the pile length or utmost friction resistance , the value of bearing capaci-ty calculated by this proposed formula was greater than the value calculated by the code's formula. The proposed formula also takes into account of the influence of pile inclination and the mechanism of pile-soil deformation compatibility .It can be a reference to calculate axial bearing capacity of bat-ter piles.%为进一步研究斜桩轴向承载力计算方法，基于斜桩的桩周摩阻力不均匀分布的特性和桩-土受力变形协调的原则，推导了斜桩轴向承载力计算公式，通过对比本文公式与规范公式的计算结果，揭示了桩身倾角、桩径、桩长和桩侧极限摩阻力等因素对斜桩轴向容许承载力的影响规律。结果表明：鉴于规范公式未考虑斜桩桩身倾角对承载力的影响，本文公式计算得
长春新开河流域粘性土地基承载力研究%Study on Bearing Capacity of Changchun Xinkai River Basin of Clay Foundation
刘汉蒙; 孙广利
2015-01-01
长春新开河流域粘性土是近年来工程建设中新遇到的土层。将其视为一般粘性土，按经验方法确定的承载力偏大，影响工程安全。本文采用载荷试验原位测试和室内土工试验方法确定长春新开河流域粘性土的地基承载力。研究了地基承载力特征值与天然孔隙比、液性指数和压缩模量的关系，总结出根据室内土工试验指标压缩模量确定长春新开河流域粘性土地基承载力的经验公式，为今后岩土工程勘察工作提供参考。%Changchun Xinkai river basin soil is encountered in recent years in the construction of soil. Be regarded as common soil, determined by the empirical method of bearing capacity is big, affect the engineering safety. This paper uses the method of test and laboratory soil test load test in situ determination of bearing capacity of Chang-chun Xinkai river basin of cohesive soilfoundation. The value and natural void ratio, liquid index and compression modulus of foundation bearing capacity characteristics of relationship. Summarized according to the experience for-mula to determine bearing capacity of Changchun Xinkai river basin soil compression modulus of soil testindex, pro-vide the reference for the geotechnical engineering survey.
任佳佳; 钱永梅; 尹新生
2012-01-01
通过研究挤扩多盘桩的现有抗拔承载力计算方法，提出利用传统模式来计算挤扩多盘桩的抗拔承载力的不足之处，并根据挤扩多盘桩在竖向拔力作用下的土体的破坏特征和桩的受力机理，提出最新的挤扩多盘桩抗拔承载力的计算模式，为该型桩的设计应用提供可靠的理论依据。%By studying the existing calculation method of pulled out of the bearing capacity of the push-extend multi-under- reamed pile, this article put forward deficiencies of the traditional mode to calculate the bearing capacity of the push-extend multi-under-reamed pile, and according to the push-extend multi-under-reamed pile under vertical pull force the characteristics of the soil destruction and working mechanism of pile, put forward the newest calculation method of pulled out of the bearing capacity of the push-extend multi-under-reamed pile, the reliable theory basis will influence the application of the expansion multiple disk pile.
李红霞; 郭艳芹; 张雷顺
2013-01-01
通过分析叠合与粘贴CFRP复合加固RC简支梁承载力的两大主要影响因素,运用现有计算方法推导得出复合加固RC梁的抗弯承载力计算公式,试验发现:仅粘贴CFRP加固RC梁,虽能有效提高构件承载力,但由于下部受拉储备充足而使上部受压储备相对不足,使构件发生类似超筋梁的脆性破坏,其极限承载力明显低于上部同时有叠合层的RC梁.试验比较发现:所用计算方法得出的计算值与试验值相比偏小,计算公式偏于保守.%Through the analysis of laminated composite of RC beams strengthened with bonded CFRP bearing force of the two major influencing factors, using the existing calculation method of composite strengthening RC beam is derived the formula to calculate the bending bearing capacity, test found that: only paste CFRP strengthened RC beams, can effectively improve the bearing capacity of members, but due to the lower tensile reserves and the upper compression reserve is relatively insufficient, make a component similar over-reinforced beam brittle failure, its ultimate bearing capacity was significantly lower than the upper part while the laminated layer of RC beam. Test comparison showed that:this method calculated value compared with experiment data is small,conservative calculation formula.
单桩竖向抗拔承载力离心模型试验研究%Centrifugal Model Test on the Vertical Uplift Bearing Capacity of Single Pile
任国峰; 徐光明; 顾行文
2012-01-01
To assist the design of pile foundation of an offshore wind farm, centrifuge modeling is performed to determine the uplift bearing capacity of single ultra-long steel pipe-pile of large diameter by which the wind turbine foundation is constituted. Curve of load versus displacement ( Q-S curve) deducted from the results of centrifuge model test are compared with that from prototype uplift capacity test. The effect of loading manner and loading rate on the ultimate uplift bearing capacity is discussed. It is shown by comparison that the value of ultimate uplift bearing capacity of single pile from centrifuge test is greater than that obtained from prototype test. As higher rate usually mobilizes higher strength, a higher loading rate in the centrifuge model test is regarded as the cause of the difference between two test results.%结合某海上风电场桩基工程中的大直径超长钢管桩抗拔承载力研究,利用离心模拟技术,初步推求得出荷载-位移的关系曲线(即Q-S曲线),并与现场抗拔试验成果得出的Q-S曲线进行了比较,分析两者加载方式和加载速率的不同对Q-S曲线的影响.结果发现,上拔力的加载速率较快,求得的单桩抗拔极限承载力偏高.
Bearing capacity calculation of flexural members strengthened with CFRP%粘贴碳纤维加固受弯构件的抗弯承载力计算
张章; 吴锋; 周国然
2015-01-01
The bearing capacity formula of flexural members strengthened with CFRP and the material strength coefficient are proposed in this paper. Combined with experimental data, we obtained the calculation method to improvement coefficient, which can be used to simply calculate the bearing capacity. The bending capacity test of PHC pipe pile strengthened with CFRP was developed. The test results show that the calculation formula for beams strengthened with CFRP also can be used to calculate the bearing capacity of pipe piles strengthened with CFRP.%首先提出碳纤维加固受弯构件承载力计算公式，并提出碳纤维加固材料强度系数，结合收集到的粘贴碳纤维加固梁承载力试验数据，建立碳纤维加固钢筋混凝土梁的抗弯承载力提高系数计算公式，实现粘贴碳纤维加固梁的简化计算。开展了粘贴碳纤维加固预应力高强度混凝土（PHC）管桩抗弯承载力试验。试验结果表明，提出的碳纤维加固梁承载力计算公式也可用于碳纤维加固混凝土管桩承载力的计算。
施卫力; 杨成斌
2015-01-01
Mechanical‐connection bamboo joint pile has been used in different soil conditions and showed significant effect . In this paper , we carried out contrast test analysis of the mechanical connection bamboo pile with the conventional pipe pile in different soil vertical ultimate bearing capacity and anti pulling capacity .. T he results show that the bearing capacity of composite pile mechanical connection in different soil conditions is obviously higher than that of the conventional pipe .%机械连接竹节桩已在不同土质工程中得到应用且效果显著。本文将机械连接竹节桩与传统管桩在不同土质中的竖向极限承载力和抗拔承载力分别进行了对比性试验分析。结果表明，在不同土质情况下机械连接竹节桩的承载力比传统管桩有明显的提高。
杨荣华; 焦俊婷
2015-01-01
The bearing capacity was researched for slender reinforced high strength concrete ( RHC ) columns under eccentric compression loading .Based on the element model of beam -column when considering material nonlinearity and geometric nonlinearity , the computer program was given about nonlinearity analysis for RHC structures .Then main affecting factors were researched , such as slen-derness ratio , relative eccentricity , concrete strength , and longitudinal reinforcement ratio .The influ-encing order of these factors was relative eccentricity , slenderness ratio , longitudinal reinforcement ra-tio , and concrete strength , on the bearing capacity for slender RHC columns under eccentric compres-sion loading.As last, the design formula of the bearing capacity was given for slender RHC columns under eccentric compression loading by using the regression statistics method , this would offer design reference .%基于考虑材料非线性和几何非线性耦合梁柱单元模型，采用编制的钢筋高强混凝土结构非线性数值分析程序，分析钢筋高强混凝土偏压中长柱极限承载力主要影响因素有长细比、相对偏心距、混凝土强度、纵筋配筋率等。研究钢筋高强混凝土偏压中长柱极限承载力对各主要影响因素的敏感性，依次为相对偏心距、长细比、纵筋配筋率和混凝土强度。通过回归给出钢筋高强混凝土偏压中长柱极限承载力的计算公式，为实际工程应用提供计算参考。
田伟; 干钢
2013-01-01
以大型通用软件ANSYS为平台,研究以轴力为主、同时考虑弯矩作用的梭形格构柱的稳定承载能力.通过对不同高度和长细比的梭形格构柱进行非线性稳定计算和参数分析,提出了梭形格构柱稳定承载力的实用计算方法:以弹性特征值为基础计算梭形格构柱的等效长细比,并利用弯矩系数对等效长细比进行修正,得到修正长细比后即可通过查表的方式得到梭形格构柱稳定承载力.%The stability bearing capacity of shuttle-shaped steel lattice columns subject to combined axial force and bending moment is explored through general software ANSYS.Through nonlinear stability analysis and parameter analysis of shuttleshaped steel lattice columns with various heights and slenderness ratios,a practical calculation method is proposed to calculate stability bearing capacity of shuttle-shaped steel lattice columns with bending moment:equal slenderness ratio based on elastic buckling eigenvalues is present; moment ratio is then proposed to modify slenderness ratio,and the ratio can be used to get the stability bearing capacity of shuttle-shaped steel lattice columns through tables.
林巧吟
2009-01-01
The article studies the destroyed form and ultimate status of carbon fiber material strengthened steel reinforced concrete bending members, and puts forward a practical calculation method for the front sectional bending bearing capacity, which can provide the reference for the practical engineering design.%该文对碳纤维材料补强加固钢筋混凝土抗弯构件的破坏形态和极限状态进行了研究,提出了正截面受弯承载力的实用计算方法,可为实际工程设计提供参考.
丁敏; 李密密; 施旭栋; 张鹏; 蒋秀根
2016-01-01
The greenhouse is a kind of agriculture production building facilities. It should bear all kinds of loads, including the loads induced by gravity, improper operation, and live loads, such as wind load and snow load. At the present time, a large number of research studies on greenhouse have focused on illumination, temperature, gas and humidity, whereas there are few researches published on greenhouse structures, especially on greenhouse structure design theory taking the supporting role of covering materials into account. It is necessary to carry out the research on space robustness of greenhouse structure by bringing the design work condition into correspondence with the actual work condition. Then three types of greenhouse including Huabei-type greenhouse, venlo greenhouse and sunlight greenhouse, were chosen to be prototypes, and the numerical simulations on the overall collapse process of single hinged frame, whole frame structure, whole frame structure with plate glass covering, whole frame structure with PC board covering, and whole frame structure with membrane covering under windstorm and snowstorm were carried out by using finite element analysis software ANSYS with consideration of geometric imperfections, material nonlinearity and geometric large deformation. The collapse modes of greenhouse structure and the corresponding load-displacement curves were obtained. The stable bearing capacity and the space robustness of greenhouse structures were analyzed under three typical weather disasters. At the same time their ultimate load coefficient and stable bearing capacity coefficient were provided. The results showed that buckling failure mode happens easily for greenhouse structure under vertical snow load, the whole structure bearing capacity was higher for greenhouse structure under horizontal wind load considering skin effect of covering material. It was due to more compression-flexure members existing in greenhouse structure under vertical snow load than
谢成新
2001-01-01
The shear bearing capacity on the small concrete block wall are analyed by grey system theory as well as the correlation factors.The analysis result shows that the first factor that influences the shear bearing capacity on the concrete block wall is pressure resistance strength of wall f,height and width ratio h/b and normal pressure N,the shear span ratio λ has the least influence.%应用灰色系统理论，对混凝土小型砌块墙体抗剪承载力及其关联因素进行关联度分析。结果表明，对混凝土小型砌块墙体抗剪承载能力影响最大的是砌体抗压强度f，其次是墙体的高宽比h/b、垂直压力N，影响最小的是剪跨比λ。
Load-bearing Capacity Analysis Method for Explosive Bolt on Launch Vehicle%运载火箭爆炸螺栓承载能力分析方法
杨帆; 张希; 章凌; 曾杜娟; 郑卫东
2015-01-01
The transverse unlocking plane of fairing in launch vehicle is usually connected by explosive bolts. The empirical formula used for calculating explosive bolt strength is rash without considering local deformation effect. In this paper, finite-element method was adopted to stimulate the local deformation of explosive bolt which disclosed the mechanism of local deformation of explosive bolt. A method for calculating explosive bolt load-bearing capacity was proposed. By comparing with finite-element calculation results, the revised method can enhance the calculating precision of explosive bolt load-bearing capacity significantly.%运载火箭的整流罩横向解锁面一般采用爆炸螺栓连接,目前针对爆炸螺栓强度计算采用的是经验算法,由于没有考虑局部变形效应往往偏于冒进.采用有限元方法对爆炸螺栓的局部变形进行详细的仿真,揭示了爆炸螺栓结构的局部变形机理,并提出一种计算爆炸螺栓承载能力的方法,通过与有限元计算结果的对比,修正后的方法能够大幅提高爆炸螺栓承载力的计算精度.
李俊华; 赵银海; 唐跃锋; 刘明哲
2012-01-01
进行了5个火灾后型钢混凝土柱轴心压力作用下的试验,研究长细比、混凝土强度对构件破坏形态和剩余承载能力的影响.试验结果表明,火灾后型钢混凝土轴心受压柱在荷载作用下的破坏形态与常温下基本相同,试件破坏时其内部核心型钢依然完好,不会发生局部屈曲现象.混凝土强度和长细比是影响型钢混凝土轴心受压柱火灾后承载能力的两个重要因素,当长细比相差不太大的情况下,混凝土强度高的试件,其火灾后极限承载力相对较高;在混凝土强度大致相当的情况下,随着长细比的增大,火灾后试件的极限承载力降低.利用YB规程和JGJ规程方法,对所有试件常温下的极限承载力进行了计算,结果表明在该文的试验条件下得到的火灾后型钢混凝土轴心受压柱承载能力的试验值与常温下承载力计算结果的比值在62%～71％之间,经历火灾作用后型钢混凝土轴心受压柱承载能力显著降低,火灾后的剩余承载力水平平均为常温下承载力水平的67％.%This paper provided five test data pertaining to the residual load bearing capacity of steel reinforced concrete (SRC) columns after exposure to fire. Two parameters, that is, slenderness ratio and concrete strength are mainly taken into consideration. Test results show that the failure pattern of SRC columns under an axial pressure force after exposure to fire is basically the same with that at room temperature. When the specimens are destroyed, the internal core steels are still fine, having no local buckling phenomena. Concrete strength and the slendemess ratio are two important factors that affect the strength of SRC columns under an axial pressure force after exposure to fire. For the specimens of about the same slenderness ratios, the higher concrete strength they are, the higher ultimate bearing capacity they have. In the condition of roughly the same concrete strength, the ultimate
楚留声; 赵军; 王卫仑; 李明杰
2016-01-01
Based on the idea of partial reinforcement, a method that using steel fiber reinforced concrete in boundary elements of high wall was proposed according to the construction difficulty and complex stress state of boundary elements.Combined with the test results, the applicability of the finite element numerical analysis was verified, and the influences on the lateral bearing capacity of this kind of shear wall from different steel fiber volume ratios and axial load ratio were studied, to which a comparative analysis of accordingly lateral bearing capacity of overall steel fiber reinforced concrete shear wall was then conducted.Results showed that the lateral bearing capacity was best when the steel fiber volume ratio in reinforced concrete of boundary elements was between 1.5% and 2%, with a maximum increase of 45.1%.Compared with the overall steel fiber reinforced concrete shear wall, the high shear wall with steel fiber reinforced concrete only in boundary elements does not reduce excess capacity, while has great economic advantage.%基于“部分增强”的思想，针对剪力墙边缘构件受力复杂、施工困难的特点，提出在高剪力墙边缘构件中采用钢纤维局部增强的方法。结合试验结果，验证了有限元数值分析的适用性，研究了钢纤维体积率和轴压比对钢纤维增强边缘构件混凝土高剪力墙抗侧承载力的影响，并与整体钢纤维混凝土剪力墙相应的抗侧承载力进行对比分析。结果表明：边缘构件钢纤维体积率为1.5％～2％时，对剪力墙承载力增强效果最强，最大提高幅度达45.1％。相对于整体钢纤维混凝土剪力墙，仅边缘构件采用钢纤维增强的剪力墙在未降低过多承载力的情况下，具有较好的经济优势。
A. García Toll
2003-01-01
hydrostatic lubrication.This work presents a calculation method that values the work capacity of bearings under conditions of hydrodynamiclubrication. The procedure is based on the study of DIN 31652 (1983 norm, and the ISO/DIS 7902 norm proposal debatedon October – December 1997 .Key words: Sliding bearings, hydrodynamic lubrication, work capacity.
王丽敏; 宋雄彬
2012-01-01
Because separating column and beam-slab exist certain difficulty, accustomed to utilize unified the strength of floor concrete to pouring in joint construction. If the concrete strength grades of column and beam have large difference, the concrete strength of joint area can＂ t meet the design requirements, bearing capacity of beam- column joint whether or not satisfied the requirements cause the most attention to engineers. In this paper, we take the inspection and appraiser for the bearing capacity of beam-column joint of the hotel as an example, based on consulting some domestic and foreign experience concerning this subject, introducing the concept of ＂ discount strength ＂ of the joint area, to solve the problem of the strength concrete value ,giving more accurate result of bearing capacity of beam-column joint, providing a certain reference action for similar appraisal work.%由于柱与梁板之间的分隔存在一定难度，施工中习惯于在节点区统一采用楼盖的混凝土强度进行浇注，此时若柱、梁的混凝土强度等级相差较大，就将造成节点区混凝土强度达不到设计要求，节点区的承载力是否能满足要求成为工程技术人员最关心的问题。本文以某酒店框架节点承载力检测鉴定为例，在参考国内外相关经验的基础上，引入节点区混凝土“折算强度”的概念，较好地解决了节点区混凝土强度的取值问题，较准确地鉴定了节点的承载能力，为相关类似检测鉴定工作提供了参考。
Menke, John R.; Boeker, Gilbert F.
1976-05-11
1. An improved journal bearing comprising in combination a non-rotatable cylindrical bearing member having a first bearing surface, a rotatable cylindrical bearing member having a confronting second bearing surface having a plurality of bearing elements, a source of lubricant adjacent said bearing elements for supplying lubricant thereto, each bearing element consisting of a pair of elongated relatively shallowly depressed surfaces lying in a cylindrical surface co-axial with the non-depressed surface and diverging from one another in the direction of rotation and obliquely arranged with respect to the axis of rotation of said rotatable member to cause a flow of lubricant longitudinally along said depressed surfaces from their distal ends toward their proximal ends as said bearing members are rotated relative to one another, each depressed surface subtending a radial angle of less than 360.degree., and means for rotating said rotatable bearing member to cause the lubricant to flow across and along said depressed surfaces, the flow of lubricant being impeded by the non-depressed portions of said second bearing surface to cause an increase in the lubricant pressure.
张晓君
2001-01-01
首先选用土工合成材料加筋地基承载力的极限状态方程,对随机变量的概率模型进行了分析,最后结合工程实例,采用优化方法进行了复合地基可靠度的计算.%Firstlythe state equation of bearing capacity of foundation reinforced with geosynthetics was Constructed .Secondlythe probabilistic models of parameters treated as stochastic variables were analyzed. Finallyusing a case historythe reliability of composite foundation was calculated by way of microsoft Excel 2000 solver.
钮鹏; 金春福
2015-01-01
Based on Je(z)ek method for computing the elastic-plastic buckling of the member under axial compressive loads and the bending moments,and considering the initial imperfection,the analytical expressions are derived for calculating the ultimate load of buckling about the neutral axis with the maximum moment of inertia for a square steel tube member with flange outsides wrapped by carbon fibre.Using the elastic-plastic finite element method and the theory of nonlinear buckling,the impact by initial geometric imperfections on the square steel tube member wrapped by carbon fibre is analyzed and the numerical solutions for ultimate bearing capacity are obtained.By comparing with the values of the finite element method (FEM),it shows that the analytical method proposed is valid.The calculation results show that when the value of moment is given,only the ultimate bearing capacity of the member reinforced by the carbon fiber among the three member always keeps a higher figure.When the given moment is small,the ultimate bearing capacity of a bare steel member is higher than that of a steel member reinforced by the carbon fiber with the initial geometric imperfection.When the value of the bending moment increases gradually,the ultimate bearing capacity of the former reduces faster than the latter.%该文利用计算压弯钢构件弹塑性失稳的Je(z)ek法,推导了受轴心压弯外力作用下具有初始几何缺陷且翼缘两侧分别粘贴碳纤维片后的方钢管构件失稳时极限荷载的计算公式.通过采用数值分析法,结合非线性屈曲理论,进行了受初始几何缺陷影响的碳纤维增强方钢管构件的屈曲分析,并得到极限承载力的数值解.将数值分析结果与Je(z)ek法得到的解析解进行比对,可以发现两种计算结果吻合的较好.由计算结果可知,当给定弯矩值时,三种构件当中碳纤维增强后的构件极限承载力始终保持较高数值.给定弯矩较小时,裸钢构件的极限承载
2015-01-01
为了简化施工过程，节约施工成本，阐述了利用通用有限元分析软件对楼板承载力计算的方法，以保证在不加固原有混凝土楼板时，吊机等机械设备可以直接安全可靠的在混凝土楼板上进行行走和吊装构件等工作。%In order to simplify the construction process and save the construction cost,describes the calculation method of bearing capacity of slabs using finite element analysis software,ensure the machines can be directly safety running and lifting components on unreinforced concrete floor.
Schuett, T.; Hoffmann, M.; Schuler, X.; Stumpfrock, L. [Materialpruefungsanstalt (MPA), Univ. Stuttgart, Stuttgart (Germany)
2007-07-01
In power plants numerous dissimilar welds exist between ferritic and austenitic components. The evaluation of the influence of real or postulated flaws to the load bearing and failure behaviour in the area of dissimilar welded joints, e. g. in piping of the primary circuit of nuclear power plants, is an essential part of the safety assessment of these plants. The fracture assessment of dissimilar welds containing flaws is therefore an important issue of structural integrity considerations. During the past decades several assessment procedures for the evaluation of flaws in welds have been developed mainly based on methods originally developed for homogenous materials. The main difficulties in applying these methods are that they are restricted to two different materials and the very limited experimental evaluation especially by component tests. To improve the general understanding of the influence of flaws in piping systems with dissimilar welds and to have a more reliable basis for the assessment of the fracture behaviour, full scale tests on pipes containing a weld between ferritic and austenitic steel have been performed. The test results of these tests are summarised and used for the evaluation of analytical and numerical assessment procedures. (orig.)
轮胎碎片加筋砂土路基承载力试验%Tyre Pieces of Reinforced Sand Subgrade Bearing Capacity Test
李丽华; 刘毅; 肖衡林; 崔飞龙; 任增乐; 高萌
2016-01-01
废旧轮胎碎片与砂土混合使用，可以有效提高路基承载力，减小路基不均匀沉降。为了深入研究废旧轮胎碎片加筋路基工作机理，通过室内模型试验，利用数字照相无标点变形测量系统，结合地基土压力分布和 P－S 曲线，研究了废旧轮胎碎片加筋路基的加筋机理和破坏模式，研究结果表明，轮胎碎片加筋使土体位移场产生了显著的变化，有效的限制了路基浅部土体的水平位移，轮胎碎片含量为5％时，加筋效果较优。%Scrap tire chips mixed with sand,can effectively improve the subgrade bearing capaci﹣ty,reduce differential settlement of subgrade.In order to study fragments of scrap tires working mechanism of reinforced embankment.Through model tests,the use of digital photography without punctuation de﹣formation measurement system.Combined with soil pressure distribution and P -S curve.Study the rein﹣forcement mechanism of scrap tires and debris reinforced embankment failure mode.The results show,tyre pieces of reinforcement to displacement field of soil produced a significant change and effective limits the roadbed shallow soil horizontal displacement.When the tire debris content is 5%,subgrade has the best effect of reinforcement.
郭敏; 申超
2013-01-01
随着风电机组容量的逐渐增大，传统风电机组基础形式已经不能满足使用要求，必须要在传统基础上进行创新。预应力墩基础预应力墩基础作为一种新型基础，在适用范围、安全性能以及建造成本上具有一定优势。该文通过研究预应力墩基础的抗倾覆验算方法，为计算这种新型基础的抗倾覆承载力探索一种快速、合理的方法。%As the gradually increasing of wind turbine capacity, traditional wind turbine foundation type can no longer meet the operating requirements. It is necessary to make innovation based on the traditional foundations. As a new type of wind turbine foundation, the prestressed pier foundation has advantages on the application range, safety performance and construction costs. Tis paper researched and explored a fast and reasonable method for computing the anti-overturning bearing capacity of wind turbine prestressed pier foundation through studying several calculation methods.
灌注桩钢筋笼长度对承载力的影响%The bearing capacity of pile length of reinforcing cage of inlfuence
王东; 马青龙; 王德庆
2015-01-01
The uplift pile for foundation under pulling force is a common practice of engineering. In some deep underground engineering, the bored piles can provide higher pull-out force, reinforced concrete pile and the soil is a good way to combine, make the uplift capacity of pile with good performance. But in actual project, the contractor to save costs, fail to execute the works in accordance with the drawings, to reduce the length of reinforcing cage, brings to the engineering quality hidden trouble.%抗拔桩来承担基础承受的上拔力是工程界常见的做法.在一些较深的地下工程中,钻孔灌注桩能提供较高的抗拔力,钢筋混凝土桩身与土层可以很好地结合 ,使这种桩具有良好的抗拔性能.但在实际工程中,施工方为节约成本,未能按照图纸施工,减少钢筋笼的长度,给工程质量带来隐患.
The vented pressure fed gas journal bearing
Hydrodynamic-type gas journal bearings with stabilising venting slots are often operated hydrostatically during starting-up as a means of 'jacking'. A simplified mathematical treatment of the circumferential gas flows in a vented, pressure-fed journal bearing is used to predict the relationship between load capacity, bearing geometry and gas properties. (author)
刘希月; 杨建军; 王元清
2013-01-01
对脚手架这种临时结构重要性的忽视以及对新型脚手架的性能研究不够,是导致脚手架倒塌事故频发的主要原因之一.为了对新型门式钢管脚手架的承载性能有充分的认识,保证其安全性,保护国家财产和人民生命安全,有必要对新型门式钢管脚手架进行科学的试验研究和理论分析,为其推广提供一定的理论参考.本文在对由两种新型门架(MF0817,MF1017)组成的三步六跨门式钢管脚手架受力性能进行试验研究的基础上,利用钢框架稳定分析理论,考虑半刚性节点作用,修正转角位移方程,对三组不同搭设情况下的脚手架承载力进行稳定理论分析,推出了门式钢管脚手架在不同搭设情况下的立杆计算长度系数的计算公式,分析结果表明立杆杆端约束条件对结果影响较大,可利用转角位移法求得反映脚手架中其他杆件对立杆约束程度的计算长度系数,并将理论分析结果与相应的试验值比较,验证了理论分析方法的正确性.%The neglect of the importance for scaffoldings as temporary structures, and the lack of study for the scaffoldings of new types are the main factors that lead the collapse accidents of scaffoldings have occurred frequently. In order to get full understanding of the bearing capacity of frame scaffolding with steel tubes that are new types and ensure the safety of those new type scaffoldings, it is necessary to conduct research scientifically about them. Based on the experimental study of the three bays-six floors full scale scaffoldings which are composed of two new type portals( MF0817,MF1017) , the paper applied the stability theory of steel frames, modified the slope-deflection equation, considering the effect of semi-rigid joints, conducted theoretical analysis of the bearing capacity of the three frame scaffoldings that are constructed in different conditions, and derived the formulation of the effective length factor of
关宏波; 王清湘
2012-01-01
A total of 15 concrete-filled glass fiber reinforced polymer(GFRP) tubular columns were tested and the specimens were divided into two groups.One group consisted of 6 specimens considering the eccentricity changes,the other consisted of 9 specimens considering the slenderness ratio changes.The test results showed that the eccentricity and slenderness ratio had great influence on mechanical properties of the concrete-filled GFRP tubular columns.With the increase of eccentricity,the destruction configuration of test specimens took place transformation from compression to tension failure gradually,and with the increasing of the slenderness ratio,the failure form of specimens changed from material damage to the instability destruction.The ultimate bearing capacity also decreased with the increasing of the eccentricity and slenderness ratio,but the amplitude of reducing slowed down.Based on the test data statistical regression,the reduction coefficient of the slenderness ratio and eccentricity of composite columns was obtained,and then the bearing capacity calculation formula of the axis pressure long columns and the eccentric-loaded columns was derived.The calculated results were compared with the experimental results,which showed a good agreement.These indicated that the proposed bearing capacity formula of the composite columns had a certain practical significance.%对9根不同长细比和6根不同偏心距的玻璃纤维增强（GFRP）套管钢筋混凝土组合柱进行试验研究。试验结果显示：偏心距和长细比对GFRP套管钢筋混凝土组合柱的力学性能有很大的影响。随着偏心距的增大,试件的破坏形态逐渐由压缩破坏向拉伸破坏转变;随长细比的增大,试件的破坏形态则由材料破坏向失稳破坏过渡。试件的极限承载力亦随偏心距和长细比的增大而降低,但降低的幅度变缓。在试验的基础上,对试验数据进行统计回归,得到GFRP套管钢筋混凝土组合柱的
黄华; 刘伯权; 贺拴海; 吴涛; 潘元
2012-01-01
In order to research the debonding failure of reinforced concrete (RC) beam flexural strengthened with high strength stainless steel wire mesh, the debonding failure in the anchorage area of strengthened beam plategend was taken as research object, Smith-Teng model was revised to calculate the debonding failure of beam strengthened with fiber reinforced plastics(FRP) or bonding steel based on anchorage tests at the plate-end of 8 strengthened RC beams. The calculation model of debonding bearing capacity at the plate-end of beam strengthened with high strength steel wire mesh was established. The debonding failure at the middle part of strengthened beam was taken as research object, the middle part between two nearby flexural cracks of RC beam was regarded as arithmetic element, the stress condition of steel wire mesh was analyzed, and the calculation models of bonding shear stress and debonding normal stress at the middle part of strengthened beam were deduced. The debonding criteria at the middle part of strengthened beam were proposed, and the models were validated. Analysis result indicates that the upper limit of the calculation model of debonding bearing capacity at plate-end equals 0.57, it is in accordance with test result. The difference between the value calculated by the model of debonding bearing capacity at the middle part and test result is approximately3.77%, so the calculation model is feasible. 2 tabs, 5 figs, 16 refs.%为分析高强不锈钢绞线网加固的钢筋混凝土梁抗弯剥离破坏，以加固梁端部锚固区域的剥离破坏为研究对象，以8根钢筋混凝土加固梁端部锚固试验为基础，对计算FRP加目梁和粘贴钢板加固梁端部剥离破坏的Smith和Teng模型进行修正，建立适合高强钢绞线网加固技术的端部剥离承栽力计算模型。以加固梁中部的剥离破坏为研究对象，取加固梁跨中部位两弯曲裂缝之间的部分为计算单元，分析钢绞线网的受力状
周绪红; 李喆; 刘永健; 石宇
2012-01-01
In order to investigate bearing capacity of cold-formed steel built-up columns under axial compression, authors used ANSYS finite element program to analyze the cold-formed steel built-up columns at home and abroad. Compared with experimental results, the validity of the finite element method (FEM) was verified. Furthermore, a detailed parametric study by FEM was carried out to mainly determine the influence of cross-section form, cross-section dimension and slenderness ratio of component for the built-up effect. The simplified calculation method to the bearing capacity of cold-formed steel built-up columns under axial compression was extracted. The analytical results show that with the increase of the slenderness ratio, the built-up effect improves. As for these columns connected with screws through web, when width-thickness ratio of flange is certain, with the increase of width-height ratio of cross-section, the integrity of the built-up web increases, which leads the built-up effect to strengthen. But the influences of different areas of cross-sections are not so obvious.%为了研究冷弯薄壁型钢拼合截面柱的轴压承载力,对各国有关冷弯薄壁型钢拼合截面柱的轴压试验进行了ANSYS有限元模拟分析,有限元计算结果与试验结果吻合良好,从而验证了有限元方法的正确性.采用有限元方法分析了构件截面形式、截面尺寸以及长细比对冷弯薄壁型钢拼合截面柱拼合效应的影响,提出了冷弯薄壁型钢拼合截面柱轴压承载力的简化计算方法.分析结果表明:随着长细比的增大,拼合截面柱的拼合效应随之增大.对于主要通过螺钉将腹板进行拼合的构件,当翼缘宽厚比一定时,随着截面宽高比的增大,腹板拼合的整体性增强,从而使拼合效应增大,而截面面积的改变对拼合效应的影响则不是很明显.
袁伟; 闫澍旺; 赵亮
2011-01-01
The soil around pile foundation in the wharf will suffer from strength reduction under the cycle wave loading conditions, which would further influence the vertical bearing capacity of the pile foundation. Through the indoor dynamic biaxial GDS to simulate' the cycle wave loading and apply these loads to the soil sample of Tianjin port, the strength reduction laws of soil under the dynamic cycle loads in different depths are obtained. Next, with the help of ABAQUS, combining the working loads with cycle wave loading on the pile foundation, the distribution laws of soil dynamic stress around the pile are analyzed. After synthesizing the dynamic biaxial test, the final results are obtained, which show the soil suffered from strength reduction spreads to the depth up to 5 m, the maximum strength reduction rate nearby soil can reach 85.3 % and the vertical bearing capacity of wharf pile foundation reduction rate is 5.73 % .%码头桩基在波浪循环荷载的长期作用下,桩周一定范围的土体会出现强度弱化,进而会一定程度的影响基桩竖向承载力.该文首先通过室内GDS动态三轴仪对天津港码头地基土样作用模拟的波浪循环荷载,研究不同深度土体受到不同幅值的循环动应力荷载作用后其强度的折减规律.然后通过ABAQUS有限元软件计算模拟码头桩基在上部既有结构相互作用的同时,桩身上部受波浪循环荷载,桩周土动应力的分布规律.结合室内动三轴试验结果,计算得到该码头桩基在波浪循环荷载作用下桩周土体弱化的影响深度约为5m,桩周土体的强度折减率最大达到85.3％,码头桩基竖向承载力的折减率为5.73％.
潘元; 黄华; 刘伯权; 付国
2012-01-01
For achieving consensus of views about the flexural behavior of the beams strengthened with reinforced high performance mortar, based on the domestic experimental study on 95 strengthened RC beams, the flexural behavior and failure mechanism of these strengthened beams were analyzed. The formulas of the flexural bearing capacity, the flexural rigidity, and the crack width were proposed, with considering the influence of first load, secondary load, the magnitude of sustained load, quantity and style of the reinforcement, and concrete strength. The calculated values were compared with tested values. The results indicate that the reinforcement included high strength stainless steel strand, reinforcing mesh and steel wire mesh. Their mechanical performances were significantly different, but the flexural behavior and failure mechanism of these beams strengthened with the reinforcement were the same. So the uniform formula could be used to calculate the bearing capacity of these strengthened beams. The calculated values are consistent with that of the experiments and the formula can be used in actual practice.%为统一中国对加筋高性能砂浆加固RC梁抗弯性能的认识，以中国学者所做95根加筋高性能砂浆加固的钢筋混凝土梁抗弯性能试验研究为基础，分析加固粱的受力性能和破坏机理，在此基础上考虑一次受力、二次受力、持载程度、加固筋类型、加固筋数量、混凝土强度等级等因素影响，建立加固梁抗弯承载力计算公式、刚度计算公式和裂缝宽度计算公式，并与试验数据进行了对比。结果表明：该加固技术采用高强钢绞线、钢筋网、钢丝网作为受力材料，虽然三者受力性能存在显著差异，但加固构件力学性能和破坏机理相似，可按统一计算公式进行承载力设计；公式计算值与试验结果符合良好，可用于实际工程计算。
廖贤
2011-01-01
To solve the design problem of the tube joints in the design of steel pipe structure,influences of β（β is ratio of branch pipe diameter and the main pipe diameter）and γ（γ is ratio of main pipe diameter and the main pipe Wall thickness） on ultimate flexural capacity of the X-shaped steel tubular joints were analyzed by establishing a finite element model in finite element programmer of ANSYS for X-shaped steel tubular joints which used a three-dimensional and four-joint elastic-plastic shell 181 elements and ideal elastic-plastic materials.Impact rules of various factors on ultimate flexural bearing capacity of X-shaped steel tubular joints were given.%为解决钢管结构设计中相贯节点设计问题,采用三维四节点弹塑性壳单元shell 181单元和理想弹塑性材料在ANSYS有限元程序中建立X型钢管相贯节点的有限元模型,分析了支管直径与主管直径比β、主管直径与壁厚比γ对X型钢管节点的极限抗弯承载力的影响,并给出各影响因素对X型钢管相贯节点抗弯极限承载力的影响规律.
丁敏; 施旭栋; 李密密; 剧锦三; 蒋秀根
2013-01-01
of film thickness, film span, film pre-tension and load on load-bearing capacity of the single film was analyzed. At the same time, three computation models of solar greenhouse structures, including single hinged arch structure, whole frame structure without film, and whole frame structure with film, were made. The overall failure process and space coefficient of solar greenhouse structure were obtained. The effect of tensioned film on the solar greenhouse structure stability was discussed with parameters such as film thickness, film elastic modulus and film pre-tension changing. The results showed that film dimension and thickness are the main factors affecting its load-bearing properties, and the ratio of film length to film width should also be considered appropriately. Film at 0.2mm thick can prevent disaster caused by extra heavy hail. Tension film was used in favor of wind resistance for solar greenhouse structures, but is not effective for snow resistance. The space coefficient of solar greenhouse structures is least effected by film elastic modulus in all analyzed parameters. The ultimate bearing capacity of the whole frame structure without film is higher than that of the single hinged arch structure under wind and snow loads. The reason is that the stiffness out of plane is enhanced by purelines. Film also plays an important role on improving the ultimate load bearing capacity of greenhouse structures. The fruits are useful to the wind, snow and hail resistant design of solar greenhouse structure covered film.
何素明; 农卫红
2013-01-01
Based on the current status of economic and social water consumption in Guangxi as shown by the water census results,the authors analyze the water use efficiency and the existing problem;discuss the bearing capacity of water resources in Guangxi from the requirements of building a moderately well-off society and implementing the most stringent water resource administration system;and put forward suggestions for supporting economic and so-cial development in Guangxi.%从广西水利普查经济社会用水现状情况，分析用水效率、存在问题；从全面建成小康社会、实行最严格水资源管理制度要求，分析广西水资源承载能力，提出支撑广西经济社会发展的对策与建议。
王凌波; 赵煜
2015-01-01
为分析开裂预应力混凝土箱形桥梁结构开裂后的残余承载力，以裂缝统计特征参数为基础，用单元退化方式模拟正裂缝，用裂缝间的单向受压杆模拟裂缝间的承压效应，采用空间梁单元和三维杆单元分别模拟梁和预应力筋，以单元降温的方式模拟预加力的效应，形成空间刚架模型模拟斜裂缝。基于开裂后混凝土及预应力钢筋的基本假定，建立开裂后结构的计算方法。按照相似高度、开裂区域截面折减、折减自重补偿的原则将相似裂缝进行合并处理，得到裂缝区域的阶梯型折减刚度模型，提出承载能力折减系数计算方法以体现开裂后结构刚度的变化。经实桥算例验证，本文方法可正确判断静定及超静定预应力混凝土结构开裂后承载力的变化程度。%Based on the crack statistic characteristic parameters,the unit degradation mode was utilized to simu-late the fracture of prestressed concrete box bridges and analyze its residual bearing capacity.In the meantime, unidirectional compressive rod,space beam element and cooling unit form were adopted to simulate the effects of pressure among cracks,prestressed tendons and the pre -tension effect,in order to form a space rigid frame model.Based on some basic assumptions of cracked concrete and prestressed steel,the calculation method was established after cracking.Merging similar cracks by the principle of similar height,reduction of cracking area and reduction gravity compensation,the ladder -type stiffness degradation model of crack area was then estab-lished and a capacity reduction calculation method was proposed to reflect the change of the crack stiffness.The real bridge example proves that the method can correctly judge the change of bearing capacity for cracked static determinacy and indeterminacy concrete structures.
Bearing Capacity Assessment on low Volume Roads
Zariņš, A.
2015-11-01
A large part of Latvian road network consists of low traffic volume roads and in particular of roads without hard pavement. Unbounded pavements shows serious problems in the form of rutting and other deformations, which finally lead to weak serviceability and damage of the road structure after intensive exploitation periods. Traditionally, these problems have been associated with heavy goods transport, overloaded vehicles and their impact. To find the specific damaging factors causing road pavement deformations and evaluate their prevention possibilities, and establish conditions that will allow doing it, the study was carried out. The tire pressure has been set as the main factor of load. Two different tire pressures have been used in tests and their impacts were compared. The comparison was done using deflection measurements with LWD together with dielectric constant measurements in a road structure using percometer. Measurements were taken in the upper pavement structure layers at different depths during full-scale loading and in different moisture/temperature conditions. Advisable load intensity and load factors for heavy traffic according to road conditions were set based on the study results.
周佳锦; 王奎华; 龚晓南; 张日红; 严天龙; 许远荣
2014-01-01
The static drill rooted nodular pile is a new type of composite pile foundation which consists of precast nodular pile and the cemented soil along the pile shaft. This kind of composite pile has a good bearing capacity, and the mud pollution will largely be reduced in its construction process. A group of experiments were conducted to provide a comparison between this composite pile and the bored pile. The axial force of the nodular pile was measured by the strain gauges attached on the pile shaft to analyze the distribution of the axial force and the skin friction along the shaft; and then a three-dimensional model was built by using the ABAQUS finite element program to investigate the load transfer mechanism of this composite pile in detail. The results of the field tests and ABAQUS simulation showed that:the bearing capacity of the static drill rooted nodular pile is better than that of the bored pile in soft soil area. The settlement of the composite pile is controlled by the precast pile, and the deformation of the precast pile and the cemented soil can be considered as deformation compatibility. The nodes on the nodular pile play an important role during the load transfer process;and the skin friction of the static drill rooted nodular pile is about 1.05-1.10 times of the skin friction of the bored pile in the same soil layer.%静钻根植竹节桩是由预应力竹节桩和桩周水泥土构成的一种新型组合桩基，该新型桩不仅承载性能较好，而且可以大量减少桩基施工过程中所产生的泥浆污染。通过静钻根植竹节桩和钻孔灌注桩的静荷载对比试验及埋设在竹节桩桩身上的应变计对桩身轴力进行测量，分析了静钻根植竹节桩桩身的轴力分布情况以及侧摩阻力的分布，用有限元软件ABAQUS对静钻根植竹节桩进行三维建模计算，详细地分析这种新型组合桩的荷载传递机制。结合现场试验与模拟计算可以得到：在软土地区，静
陈宗平; 李启良; 张向冈; 薛建阳; 陈宝春
2012-01-01
To study the mechanical behavior of recycled aggregate concrete-filled circular steel tube(RACFCST) columns under eccentric loading,15 specimens with different replacement ratio of recycled coarse aggregate,slenderness ratio and eccentricity were tested under the monotonic static loading.The failure modes were observed,and then the curve of the entire loading process as well as the strain distribution over the cross section were obtained.The influence of varying parameters on the mechanical behavior of RACFCST columns was analyzed,and then the ultimate bearing capacity was calculated using existing theories.It is shown that about the failure process and failure mode RACFCST columns are similar to the eccentrically loaded concrete-filled circular steel tube columns,in which the circular steel tube fails eventually in the drum-like buckling mode.It is found that RACFCST columns have high bearing capacity and good deformation performance,and the influences of eccentricity and slenderness ratio on the mechanical behavior of RACFCST columns are obvious,while the influence of aggregate replacement ratio is comparatively unobvious.%为了研究钢管再生混凝土偏压柱的受力性能,设计15个试件进行静力单调加载试验,考虑了再生粗骨料取代率、长细比和偏心距3个变化参数。观察试件的破坏形态,获取试件受力的全过程曲线,给出截面应变的分布情况,分析各变化参数对钢管再生混凝土偏压柱受力性能的影响,利用相关理论方法计算钢管再生混凝土偏压柱的极限承载能力。研究结果表明：钢管再生混凝土偏压柱与普通钢管混凝土偏压柱的受力过程及破坏形态相似,钢管最终表现为鼓曲破坏;钢管再生混凝土偏压柱具有较高的承载能力和良好的变形性能;偏心距、长细比对钢管再生混凝土偏压柱的受力性能影响显著,而再生粗骨料取代率对其影响不大。
张鹏; 叶黎明; 邓朗妮; 钟鑫
2011-01-01
采用截面等效代换法,对碳纤维板加固受弯钢梁进行了承载力及挠度分析,推导出CFRP板加固受弯钢梁的理论计算公式.为验证公式,进行了5根CFRP板加固钢梁的单调静力试验,并用有限元软件进行模拟分析,将计算结果分别与试验结果和有限元分析结果进行比较后发现:弯矩理论计算值比试验值略小,挠度理论计算值比试验值略大,且都与有限元模拟值相近,说明理论计算安全,计算方法具有良好的适用性.%The method of using one section to exchange another is used to study bearing capacity and deflection analysis of bending steel beams strengthened with carbon fiber-reinforced polymer (CFRP) plates. The theoretical formula of bending steel reinforced beams is worked out. Five reinforced beams are used in the monotonic static experiment for validating the formula. Finite element software is applied to simulate and analyze the strengthened beams. The calculation result is compared with the experiment and finite element simulation results and analyzed. The calculated value is less than experimental value of bending moment while the calculated value is bigger than experimental value of deflection. Both calculated values are approaching to the simulation results. It shows that the calculating is safe and the calculating method has good applicability. The formula can be used as reference in the project of designing steel beams reinforced by CFRP plates.
熊波; 林国昌; 张印桐; 罗锡林; 谭惠丰
2014-01-01
An innovative fabrication method of integrated manufacturing composite truss is developed to improve the geometric accuracy and rods connecting efficiency. Unlike previous research, the rods are connected by bonding composite shell, winding fiber tow and wrapping fabric together with the designed rod fixture. Fabrication process demonstrates good operability and stability of truss manufacture and advanced geometry accuracy of fabrication. Three-point bending test on bending bearing capacity of the truss suggests a high specific bending stiffness with rods connection of high efficiency. In addition, consistent results from a finite element simulation based on a simplified model show its potential in high computational efficiency to evaluate the bending stiffness of the truss.%为提高复合材料桁架成型几何精度和杆件连接效率，提出一种一体化成型的复合材料桁架制备方法，同时设计了杆件固定工装，通过胶接薄壳、缠绕纤维束和包裹织物实现杆件连接，制备过程表明该制备方法操作性强、稳定性好，制备桁架几何精度高；通过3点弯曲实验和有限元仿真分析了桁架的弯曲承载性能。结果表明：杆件连接效率高，桁架比弯曲刚度高；基于简化模型的有限元模拟方法计算效率高，结果可靠，可用于桁架弯曲刚度的表征。
Özcan, Mutlu; Koekoek, Winand; Pekkan, Gurel
2012-08-01
The load-bearing capacity and failure types of indirect inlay-retained fixed dental prostheses (FDP), made of particulate filler composite (PFC) (Estenia) alone or reinforced with E-glass fibers impregnated with various monomers were evaluated. Indirect inlay-retained FDPs were made between first premolars and first molars (N=30, 10/per group). The inlay parts of the specimens were silica coated and silanized and the specimens were cemented with dual-polymerized resin cement under ultrasonic vibrations. The experimental groups were as follows: Group 1: FRC1 (BR-100, UTMA) + PFC; Group 2: FRC2 (everStick C&B, Bis-GMA/PMMA) + PFC; Group 3: PFC only. The specimens were kept in distilled water at 37 °C for one month and then subjected to fracture strength test. No significant difference was found between the Group 1 and Group 2 FDPs (1357±301 N and 1213±316 N, respectively) (p>0.05) (ANOVA). Group 3 (856±299 N) showed significantly lower results than those of FRC reinforced groups (p<0.05). Failure analyses revealed no debonding of any of the FDPs from the inlay cavities. FDPs made of PFC only showed mainly catastrophic fracture of the pontic. In the FRC reinforced groups, predominantly delamination of the veneering was observed. The use of silica coating and silanization in combination with the dual-polymerized resin cement used; under ultrasonic cementation procedure provided sufficient adhesion to withstand static loading forces at the cementation interface, since the failures were predominantly delamination of the veneering in the FRC reinforced groups. PMID:22732482
Bonneau, Dominique; Souchet, Dominique
2014-01-01
This Series provides the necessary elements to the development and validation of numerical prediction models for hydrodynamic bearings. This book describes the rheological models and the equations of lubrication. It also presents the numerical approaches used to solve the above equations by finite differences, finite volumes and finite elements methods.
A hydrostatic bearing for the lower end of the vertical shaft of a sodium pump comprises a support shell encircling the shaft and a bush located between the shell and shaft. Liquid sodium is fed from the pump outlet to the bush/shaft and bush/shell interfaces to provide hydrostatic support. The bush outer surface and the shell inner surface are of complementary part-spherical shape and the bush floats relative to the shaft so that the bush can align itself with the shaft axis. Monitoring of the relative rotational speed of the bush with respect to the shaft (such rotation being induced by the viscous drag forces present) is also performed for the purposes of detecting abnormal operation of the bearing or partial seizure, at least one magnet is rotatable with the bush, and a magnetic sensor provides an output having a frequency related to the speed of the bush. (author)
Tooling Converts Stock Bearings To Custom Bearings
Fleenor, E. N., Jr.
1983-01-01
Technique for reworking stock bearings saves time and produces helicopter-rotor bearings ground more precisely. Split tapered ring at one end of threaded bolt expands to hold inside of inner race bearing assembly; nut, at other end of bolt, adjusts amount of spring tension. Piece of hardware grasps bearing firmly without interfering with grinding operation. Operation produces bearing of higher quality than commercially available bearings.
赵楠; 李正良; 刘红军
2013-01-01
进行了19个长细比λ=30～90的Q420 L220 mm×20 mm角钢试件的轴压试验研究.结果表明:此类构件在长细比λ＞45时,以弯曲失稳破坏为主；长细比λ≤45时,以弯扭失稳为主.研究了现行钢结构规范中防止局部屈曲宽厚比限值公式和计算弯扭失稳的换算长细比取值公式的适用性.采用逆算单元长度法得到了大规格等边角钢的柱子曲线,研究了此类构件与普通规格等边角钢的差异以及肢厚、肢宽和钢材强度等对柱子曲线的影响.提出了高强大规格等边角钢轴压构件的承载力计算方法.并且研究了高强大规格等边角钢两端偏心受压的柱子曲线,给出了长细比修正系数的建议公式.%The axial compression member test was conducted to investigate the stability performance of these members, including nineteen Q420 L220×20 specimens which slenderness ratio(λ) ranged from 30~90. The test results showed that when slendemess is λ > 45, flexural buckling was observed and when slenderness is λ ≤45, local or flexural-torsion or torsion buckling was observed. The applicability of local buckling wide thickness ratio formula and flexural-torsional buckling conversion slenderness ratio formula was researched. By means of inverse calculation segment length method, the column curve of the large size equal angle was got. The comparison with common size angle and parameter analysis was made. Calculation method of bearing capacity of large size equal angle was given. Two ends eccentric compression column curve was also researched, and a suggestion formula of slenderness ratio correction coefficient was given.
渡槽贝雷钢拱架稳定性及承载能力分析%Analysis for Stability and Bearing Capacity of Aqueduct Bailey Steel Arches
钟伟; 肖阳剑
2014-01-01
with some arch aqueduct which arch rings are constructed with suspended Bailey steel arches as background, this paper discloses mechanical behaviors of arches during cast-in-situ of arch rings by analyzing stability and bearing capability of arch structures, and compares changes of stability and bearing capability of arches under different constraints to draw a conclusion that consolidation constraint hinge joint adopts for arches can remarkably improve stability of arches without reduction of bearing capability of arches. This conclusion can provide a reference for design and construction of similar projects in the future.%以悬拼贝雷钢拱架施工拱圈的某拱式渡槽为背景，通过对拱架结构的稳定性及承载能力进行分析，揭示拱圈现浇过程中拱架的力学行为，并对拱架不同约束形式下其稳定性和承载力的变化进行比较，得出拱架采用固结约束较铰接能显著提高拱架稳定性且不降低拱架承载能力的结论，可为以后类似工程设计施工提供参考。
Parker, R. J.; Zaretsky, E. V.; Hanau, H.
1977-01-01
Process consisting of grinding raceways to oversize but original quality condition and installing new oversize balls or bearings restores wornout ball and roller bearings to original quality, thereby doubling their operating life. Evaluations reveal process results in restoration of 90% of replaced bearings at less than 50% of new-bearing costs.
Passive magnetic bearing configurations
Post, Richard F.
2011-01-25
A journal bearing provides vertical and radial stability to a rotor of a passive magnetic bearing system when the rotor is not rotating and when it is rotating. In the passive magnetic bearing system, the rotor has a vertical axis of rotation. Without the journal bearing, the rotor is vertically and radially unstable when stationary, and is vertically stable and radially unstable when rotating.
周明; 王新堂; 王万祯
2013-01-01
The experimental investigation on post-fire mechanical behavior of ten of four sets of unprotected short columns of ceramsite concrete filled steel tubes ( CCFST) was conducted, variation of remaining bearing capacity and failure form of the short columns of CCFST after exposure to fire was discussed for different parameters. Based on the test results, effect of the factors, such as the maximum value of fire temperatures, dimension of cross section of the specimen, slender ratio and concrete mix proportion on the remaining bearing capacities and ductility of CCFST short columns were especially investigated. The results showed that the CCFST short columns after exposure to fire had higher post-fire bearing capacity and better ductility, and there was no descent segment in load-displacement curves of the most of specimens. It was concluded that effect law of the maximum values of response temperature on bearing capacities of CCFST short columns after exposure to fire were related to some key parameters of the specimens, which were mix proportion, slender ratio and dimension of cross section of the specimens. It was shown that the post-fire bearing capacities of the CCFST short columns decreased with increase of water cement ratios of the concrete of the specimens subjected to fire load.%通过对4组10根钢管陶粒混凝土短柱受火后性能的对比试验研究,讨论不同参数的钢管陶粒混凝土短柱受火后的剩余承载力和破坏形态的变化.基于试验结果讨论火灾炉试验保持最高温度、截面尺寸、试件长细比及混凝土配合比等参数对轻骨料钢管混凝土短柱承载力和延性的影响.结果表明,以轻质材料——陶粒为粗骨料制成的钢管混凝土短柱,受火后仍然具有较高的承载力和良好的延性,且火灾后多数试件的荷载-位移曲线并没有出现下降段.最高炉温对钢管陶粒混凝土短柱火灾后承载力的影响程度与试件自身特征参数有关,主要
S. M. Muzakkir & Harish Hirani
2015-01-01
In the present research work the need of a Maintenance Free Bearings (MFB) is established. The paper presents preliminary friction calculations to highlight the ways to achieve maintenance free bearings. The existing technologies of well established maintenance free bearings are described. The hybridization of bearing technologies to achieve low cost maintenance free bearings has been exemplified. Finally a combination of passive magnetic repulsion and hydrodynamics ha...
Schroll, Henning; Andersen, Jan; Kjærgård, Bente
2012-01-01
carrying capacity (SCC) and assimilative carrying capacity (ACC). The act mandates that the latter two aspects must be taken into consideration in the local spatial plans. The present study aimed at developing a background for a national guideline for carrying capacity in Indonesian provinces and districts...... carrying capacity (ACC). The act mandates that the latter two aspects must be taken into consideration in the local spatial plans. The present study aimed at developing a background for a national guideline for carrying capacity in Indonesian provinces and districts/cities. Four different sectors (water...
Piero Iori
2013-04-01
Full Text Available Precompression stress is an important property for assessment of tropical soil structure sustainability and is often determined in laboratory tests. The objective of this study was to compare the load bearing capacity models obtained with controlled moisture in laboratory and those obtained with natural field moistures determined a long one year. The evaluation of soil structural sustainability follows four distinct steps: soil sampling in the field, uniaxial compression test of the samples in the laboratory, determination of precompression stress and estimation of the load bearing capacity models. Laboratory estimates of precompression stress were obtained from moisture controlled in laboratory and from natural moisture determined in a field a long one year. In this process, the soil samples were saturated by capillarity with distilled water in laboratory, and after 48 hours, the samples were air dried to obtain the different moisture contents. Then, the precompression stress was determined for this both conditions. To verify if the load bearing capacity models obtained with controlled moisture in laboratory may represent the load bearing models obtained with natural field moisture, these models were compared using the homogeneity test procedure. It was observed that 75% of field models analyzed were similar to the laboratory models. Thus, due to the similarity on the load-bearing capacity models obtained using natural (field or controlled (laboratory moisture contents, the assessment of the soil structure sustainability can be done using both methods.Pressão de pré-consolidação é uma importante propriedade na avaliação da sustentabilidade estrutural do solo e é determinada em testes de laboratório. Neste estudo, objetivou-se comparar modelos de capacidade de suporte de carga obtidos com umidade controlada em laboratório e com umidade natural de campo ao longo de um ano. A avaliação da sustentabilidade estrutural do solo ocorreu em
侯文崎; 叶梅新
2011-01-01
Aiming at the application of the composite structures in railway bridges, and according to the results of the push-out tests, the load-slip relationship expressions of Φ13 and Φ22 studs in C50 concrete were acquired by nonlinear least-square fit. Through the ultimate bearing capacity experiments of the composite structures with grouped studs, adopting the proposed FEA simulating method, the reduction of the average ultimate bearing capacity and the shear force distribution of the grouped studs were well studied, as well as the relative influencing factors. Research results reveal that the average ultimate bearing capacity of the grouped studs shows quite big reduction compared with a single stud, which is at most 18％. The shear force distribution of the grouped studs presents an evident non-uniformity with a shape of saddle from top to bottom, which is redistributed as the load increasing. When the load is near to the ultimate bearing capacity, the grouped studs tend to bear the even shear force. The stud stiffness and ways of the load transmission are both important influencing factors on the non-uniform shear force distribution of the grouped studs. The bigger the stud stiffness is, the more the average ultimate bearing capacity of grouped studs will be reduced. The ways of load transmission have little influence on the ultimate bearing capacity of the composite structures with the grouped studs, but have important influence on the non-uniform shear force distribution of grouped studs when the load is at a low level, and the influence will be diminished with load increasing. Analytical results of FEA show good agreement with the experimental results, which demonstrates the correctness and the feasibility of the proposed FEA method.%针对我国铁路桥梁中应用钢-混凝土组合结构,根据推出试验结果,采用最小二乘非线性拟合得到C 50混凝土中φ13和φ22栓钉的荷载-滑移关系式.通过群钉组合结构极限承载力试验,
黄玲; 杨鹏辉
2016-01-01
This article is about the evaluation of water resources carrying capacity. From the point of physical scarcity and economic scarcity,we took social,economy,ecology and water composite system into consideration. We es-tablished fuzzy comprehensive evaluation model and grey prediction model,and used MATLAB software to water resources carrying capacity in Shandong Province,and forecast the development trend of water resources carrying capacity in the next fifteen years. The results showed that Shandong province was now in a state of severe water shortage,even worse if not take action Shandong province would step into the stage of excessive water resources shortage.%文章针对水资源承载力的评价，综合社会、经济、生态和水资源的复合系统来构建评价体系，并从物理性和经济性角度分析水资源稀缺状况，建立模糊综合评价模型、灰色预测模型；同时运用Matlab软件求解得出山东省近10年的水资源承载力水平，并预测未来15年水资源承载力的发展趋势，发现山东省现处于重度缺水状态，若不加以治理未来15年将会步入水资源过度短缺阶段。
van Leeuwen, Theo; Caldas-Coulthardt, Carmen
2014-01-01
This paper presents a semiotic analysis of a key cultural artefact, the teddy bear. After introducing the iconography of the teddy bear, it analyses different kinds of stories to show how teddy bears are endowed with meaning in everyday life: stories from children's books, reminiscenses by adults...
陈明; 芦文文; 刘凯
2014-01-01
According to the composite column of double cold-formed thin-walled C steel back to back connected with gusset plate, the test and finite element analysis were carried out to study the stability bearing capacity and failure modes of the specimen under eccentric loading.The elements such as slenderness ratio, gusset plate thickness and gusset plate spacing were discussed , which produced the impacts to composite column ’ s bearing capacity, the relationship between stiffness and axial loading, and the curves of M-φof eccentricity.The results revealed that before the overall instability the local-buckling was occurred, the failure modes were belonging to the in-plane-flexural buckling.The major factors are slenderness ratio, eccentricity and gusset plate spacing which effected the mechanical behavior, while the gusset plate thickness has no obvious impact.In the end, the calculation method of the bearing capacity of the cold-formed thin-walled column was compared with that in“Technical Code of Cold-Formed Thin-Walled Section Steel Structures” ( GB 50018-2002 ) , some suggestions based on the type of composite section column calculation were put forward , and the bearing capacity correction coefficient of the steel composite columns was given .%针对带垫板的双肢背靠背C型钢组合柱，通过试验和有限元模拟分析，研究该类型组合柱在偏心荷载作用下的受力特性，就偏心距、长细比、垫板厚度和间距等参数对组合柱承载力、刚度与轴向荷载的关系和M-φ曲线的影响进行讨论。结果表明：C型钢腹板和受压翼缘在整体失稳之前出现了严重的局部屈曲，组合柱的破坏模式均为弯矩作用平面内的弯曲失稳。长细比、偏心距和垫板间距是影响组合柱受力性能的主要因素，垫板厚度的影响有限。最后与规范GB 50018-2002《冷弯薄壁型钢结构技术规范》规定的柱承载力的计算方法进行对比，对该类组合柱的
谭方; 吴帅; 黄宗芳; 陈哲
2013-01-01
Taking the actual case of Chengdu Panda City Ⅱ as an example,based on the in-situ plate loading tests and numerical analysis results,the reasonable determination method of ground bearing capability was discussed.The overcharge was improved through increasing the numbers of anti-floating anchor,so revised bearing capacity can meet the design requirement.The deformation modulus from the in-situ plate loading tests was used to calculate the settlement.Modified by the experience in Chengdu area,the calculation results agree well with the measured settlements and the average settlement is small.The successful application of shallow foundation is beneficial to apply to similar projects.%以成都熊猫城二期为例,通过原位平板荷载试验,并结合数值分析结果,探讨了合理确定地基承载力的方法,通过增加抗浮锚杆提高超载,修正后的承载力可满足设计要求.用原位试验的变形模量计算建筑物的沉降量,经成都地区经验修正后,接近实测值且平均沉降量较小.天然基础的成功应用可为类似工程提供参考.
A magnetic bearing based on eddy-current repulsion
Nikolajsen, J. L.
1987-01-01
This paper describes a new type of electromagnetic bearing, called the Eddy-Current Bearing, which works by repulsion between fixed AC-electromagnets and a conducting rotor. The following advantages are expected: inherent stability, higher load carrying capacity than DC-electromagnetic bearings, simultaneous radial, angular and thrust support, motoring and generating capability, and backup mode of operation in case of primary power failure. A prototype is under construction.
The shear bear capacity of reactive powder concrete beam with high strength stirrup%配筋活性粉末混凝土梁抗剪承载力
邓宗才; 周冬至; 程舒锴
2014-01-01
为掌握高强箍筋活性粉末混凝土（ reactive powder concrete，RPC）梁的抗剪性能，通过6根T形梁的抗剪试验，获得了抗剪承载力试验值，并将试验值与压力场理论值进行了比较，探讨了压力场理论应用于RP C梁抗剪分析和承载力计算存在的问题，充分考虑斜裂缝截面上钢纤维拉拔阻力的抗剪贡献，对该理论进行了改进。并将剪切试验结果与塑性剪切理论、粘结滑移理论和法国规范等进行了比较，分析现有抗剪理论的适用条件、存在的问题，这些对揭示RP C梁抗剪破坏机理、建立承载力计算理论与设计方法有参考价值。%To grasp the shear strength properties of reactive powder concrete ( RPC) beams with high strength stir-rup, through 6 T-shaped beams test, the shear strength test values were obtained.The test values and the theoreti-cal values of the compression field theory were compared and the questions of applying the compression field theory in the analysis and calculation of shear capacity for RPC beams were also discussed.The modified compression field theory was proposed by considering the shear crack resistance improvement from the contribution of the steel fibers at the diagonal crack during pull out.Results of the shear test were also compared with the plastic shear theory, the interfacial bond shear strength theory and French code specifications.An analysis of problems facing the existing theories and their applications was also conducted.The analysis results and comparison conducted on the different shear capacity theories provided a solid base for future researches on the shear failure mechanism and further devel-opment of shear capacity design models for RPC beams.
Study on Load-Bearing Characteristics of a New Pile Group Foundation for an Offshore Wind Turbine
Ruiqing Lang
2014-01-01
Full Text Available Because offshore wind turbines are high-rise structures, they transfer large horizontal loads and moments to their foundations. One of the keys to designing a foundation is determining the sensitivities and laws affecting its load-bearing capacity. In this study, this procedure was carried out for a new high-rise cap pile group foundation adapted to the loading characteristics of offshore wind turbines. The sensitivities of influential factors affecting the bearing properties were determined using an orthogonal test. Through a combination of numerical simulations and model tests, the effects of the inclination angle, length, diameter, and number of side piles on the vertical bearing capacity, horizontal bearing capacity, and bending bearing capacity were determined. The results indicate that an increase in the inclination angle of the side piles will increase the vertical bearing capacity, horizontal bearing capacity, and bending bearing capacity. An increase in the length of the side piles will increase the vertical bearing capacity and bending bearing capacity. When the length of the side piles is close to the central pile, the increase is more apparent. Finally, increasing the number of piles will increase the horizontal bearing capacity; however, the growth rate is small because of the pile group effect.
Study on load-bearing characteristics of a new pile group foundation for an offshore wind turbine.
Lang, Ruiqing; Liu, Run; Lian, Jijian; Ding, Hongyan
2014-01-01
Because offshore wind turbines are high-rise structures, they transfer large horizontal loads and moments to their foundations. One of the keys to designing a foundation is determining the sensitivities and laws affecting its load-bearing capacity. In this study, this procedure was carried out for a new high-rise cap pile group foundation adapted to the loading characteristics of offshore wind turbines. The sensitivities of influential factors affecting the bearing properties were determined using an orthogonal test. Through a combination of numerical simulations and model tests, the effects of the inclination angle, length, diameter, and number of side piles on the vertical bearing capacity, horizontal bearing capacity, and bending bearing capacity were determined. The results indicate that an increase in the inclination angle of the side piles will increase the vertical bearing capacity, horizontal bearing capacity, and bending bearing capacity. An increase in the length of the side piles will increase the vertical bearing capacity and bending bearing capacity. When the length of the side piles is close to the central pile, the increase is more apparent. Finally, increasing the number of piles will increase the horizontal bearing capacity; however, the growth rate is small because of the pile group effect. PMID:25250375
Novel nano bearings constructed by physical adsorption
Zhang, Yongbin
2015-09-01
The paper proposes a novel nano bearing formed by the physical adsorption of the confined fluid to the solid wall. The bearing is formed between two parallel smooth solid plane walls sliding against one another, where conventional hydrodynamic lubrication theory predicted no lubricating effect. In this bearing, the stationary solid wall is divided into two subzones which respectively have different interaction strengths with the lubricating fluid. It leads to different physical adsorption and slip properties of the lubricating fluid at the stationary solid wall respectively in these two subzones. It was found that a significant load-carrying capacity of the bearing can be generated for low lubricating film thicknesses, because of the strong physical adsorption and non-continuum effects of the lubricating film.
Conceptual Design and Feasibility of Foil Bearings for Rotorcraft Engines: Hot Core Bearings
Howard, Samuel A.
2007-01-01
Recent developments in gas foil bearing technology have led to numerous advanced high-speed rotating system concepts, many of which have become either commercial products or experimental test articles. Examples include oil-free microturbines, motors, generators and turbochargers. The driving forces for integrating gas foil bearings into these high-speed systems are the benefits promised by removing the oil lubrication system. Elimination of the oil system leads to reduced emissions, increased reliability, and decreased maintenance costs. Another benefit is reduced power plant weight. For rotorcraft applications, this would be a major advantage, as every pound removed from the propulsion system results in a payload benefit.. Implementing foil gas bearings throughout a rotorcraft gas turbine engine is an important long-term goal that requires overcoming numerous technological hurdles. Adequate thrust bearing load capacity and potentially large gearbox applied radial loads are among them. However, by replacing the turbine end, or hot section, rolling element bearing with a gas foil bearing many of the above benefits can be realized. To this end, engine manufacturers are beginning to explore the possibilities of hot section gas foil bearings in propulsion engines. This overview presents a logical follow-on activity by analyzing a conceptual rotorcraft engine to determine the feasibility of a foil bearing supported core. Using a combination of rotordynamic analyses and a load capacity model, it is shown to be reasonable to consider a gas foil bearing core section. In addition, system level foil bearing testing capabilities at NASA Glenn Research Center are presented along with analysis work being conducted under NRA Cooperative Agreements.
Ball Bearing Stacking Automation System
Shafeequerrahman S . Ahmed
2013-01-01
Full Text Available This document is an effort to introduce the concept of automation in small scale industries and or small workshops that are involved in the manufacturing of small objects such as nuts, bolts and ball bearing in this case. This an electromechanical system which includes certain mechanical parts that involves one base stand on which one vertical metallic frame is mounted and hinged to this vertical stand is an in humanized effort seems inadequate in this era making necessary the use of Electronics, Computer in the manufacturing processes leading to the concept of Automated Manufacturing System (AMS.The ball bearing stack automation is an effort in this regard. In our project we go for stack automation for any object for example a ball bearing, be that is still a manual system there. It will be microcontroller based project control system equipped with microcontroller 89C51 from any manufacturer like Atmel or Philips. This could have been easily implemented if a PLC could be used for manufacturing the staking unit but I adopted the microcontroller based system so that some more modification in the system can be effected at will as to use the same hardware .Although a very small object i.e. ball bearig or small nut and fixture will be tried to be stacked, the system with more precision and more power handling capacity could be built for various requirements of the industry. For increasing more control capacity, we can use another module of this series. When the bearing is ready, it will be sent for packing. This is sensed by an inductive sensor. The output will be proceeds by PLC and microcontroller card which will be driving the assembly in order to put it into pads or flaps. This project will also count the total number of bearings to be packed and will display it on a LCD for real time reference and a provision is made using a higher level language using hyper terminal of the computer
黎冰; 高玉峰; 沙成明; 童小东
2012-01-01
To accurately determine the maximum pull-out loading capacity of suction caisson foundation in sand, the limit equilibrium method is applied. Based on the mechanical characteristics of suction caisson foundation with horizontal translation, a method for three-dimensional limit equilibrium analysis of maximum pull-out loading capacity of suction caisson foundation in sand is proposed. In the proposed method, the development process of earth pressure and shear resistance with displacement, and the characteristics of different earth pressure and side shear resistance over the caisson cross-section are considered. The earth pressure acting on the caisson is assumed to obey the Winkler model and is not in excess of the limiting earth pressure. The shear resistance between caisson and soil is assumed to be linearly proportional to the relative displacement between them before reaching its ultimate value. Fifteen model tests of suction caisson foundation under horizontal loading in sand are conducted to investigate its pull-out behaviors, and the load-displacement curves are obtained. The calculation results by the proposed method agree well with the experimental results, indicating that the proposed method is accurate and effective. Key w%为了准确确定砂土中吸力式沉箱基础的最大承载力,应用极限平衡法对其进行分析.基于吸力式沉箱基础平动时的受力特点,充分考虑土压力和摩擦力的发挥过程以及沉箱横截面上各点土压力大小的不同,提出了一种计算砂土中吸力式沉箱基础最大承载力的三维极限平衡方法.方法中假定沉箱侧壁土压力满足Winkler模型,但其值不超过水平极限土压力值;假定沉箱侧壁与地基土之间的摩擦力在达到最大值之前与两者之间的相对位移成线性正比关系.开展了15组水平荷载作用下吸力式沉箱基础的模型试验,得到了吸力式沉箱基础的荷载-位移曲线.利用所提方法得到的计
Blome, C.D.; Kuzniar, R.L.
2009-01-01
A bear spray safety program for the U.S. Geological Survey (USGS) was officially initiated by the Firearms Safety Committee to address accident prevention and to promote personnel training in bear spray and its transportation, storage, and use for defense against wild animals. Used as part of a system including firearms, or used alone for those who choose not to carry a firearm, bear spray is recognized as an effective tool that can prevent injury in a wild animal attack.
Optimal Synchronizability of Bearings
Araújo, N. A. M.; Seybold, H.; Baram, R. M.; Herrmann, H. J.; Andrade, J. S.
2013-01-01
Bearings are mechanical dissipative systems that, when perturbed, relax toward a synchronized (bearing) state. Here we find that bearings can be perceived as physical realizations of complex networks of oscillators with asymmetrically weighted couplings. Accordingly, these networks can exhibit optimal synchronization properties through fine tuning of the local interaction strength as a function of node degree [Motter, Zhou, and Kurths, Phys. Rev. E 71, 016116 (2005)]. We show that, in analogy...
Bearing restoration by grinding
Hanau, H.; Parker, R. J.; Zaretsky, E. V.; Chen, S. M.; Bull, H. L.
1976-01-01
A joint program was undertaken by the NASA Lewis Research Center and the Army Aviation Systems Command to restore by grinding those rolling-element bearings which are currently being discarded at aircraft engine and transmission overhaul. Three bearing types were selected from the UH-1 helicopter engine (T-53) and transmission for the pilot program. No bearing failures occurred related to the restoration by grinding process. The risk and cost of a bearing restoration by grinding programs was analyzed. A microeconomic impact analysis was performed.
Nielsen, Nick; Pedersen, Sandra Bleuenn; Sørensen, Jens Ager;
2015-01-01
In this paper, we introduce the EcoBears concept that aims to augment household appliances with functional and aesthetic features to promote their "use'' and "longevity of use'' to prevent their disposal. The EcoBears also aim to support the communication of environmental issues in the home setting....... We present our initial design and implementation of the EcoBears that consist of two bear modules (a mother and her cub). We also present our preliminary concept validations and lessons learned to be considered for future directions....
Experimental evaluation of mechanical property for FPS isolation bearings
The FPS isolation bearings produce the isolation effect by introducing flexibility and energy absorption capability at an interface between the structure and the moving ground. In this system, the structure on FPS bearing behaves as a pendulum of length R, where R is the radius of curvature of the spherical sliding surface. There are two important advantages in friction pendulum systems; The bearings have high vertical load capacity and stability. The properties of flexibility, energy absorption capability and vertical load capacity are not interrelated. In this study, A series of laboratory experiments has been conducted to determine the effect of sliding velocity, bearing pressure, test waveform, and horizontal displacement on the frictional characteristics of FPS isolation bearings. As a result, it is found that frictional coefficient increases with increasing velocity up to a certain value and frictional coefficient drops with increasing pressure
Bearing fatigue investigation 3
Nahm, A. H.; Bamberger, E. N.; Signer, H. R.
1982-01-01
The operating characteristics of large diameter rolling-element bearings in the ultra high speed regimes expected in advanced turbine engines for high performance aircraft were investigated. A high temperature lubricant, DuPont Krytox 143 AC, was evaluated at bearing speeds to 3 million DN. Compared to the results of earlier, similar tests using a MIL-L-23699 (Type II) lubricant, bearings lubricated with the high density Krytox fluid showed significantly higher power requirements. Additionally, short bearing lives were observed when this fluid was used with AISI M50 bearings in an air atmosphere. The primary mode of failure was corrosion initiated surface distress (fatigue) on the raceways. The potential of a case-carburized bearing to sustain a combination of high-tangential and hertzian stresses without experiencing race fracture was also investigated. Limited full scale bearing tests of a 120 mm bore ball bearing at a speed of 25,000 rpm (3 million DN) indicated that a carburized material could sustain spalling fatigue without subsequent propagation to fracture. Planned life tests of the carburized material had to be aborted, however, because of apparent processing-induced material defects.
徐世烺; 尹世平
2012-01-01
The structural performance can be enhanced without increasing the section size of the component when the new composite of textile reinforced concrete （TRC） is applied to strengthen and retrofit existing structures. However, due to the brittle feature of fiber materials, tensile failure would occur if the ultimate tensile strength of textile is reached, which is unsafe for structures. Therefore, for a single rectangular beam, two types of limit failure states of beams strengthened with TRC are presented for different amounts of textile, and for each state, the relationship between the textile ratio and the steel reinforcement ratio is derived. Based on the plane section assumption, calculation methods for the ultimate bearing capacity of the normal section of the component strengthened with TRC in three types of failure mode are also presented, including first load and secondary load. The experimental results show that the first failure mode is unfavorable to the component and the calculated values of ultimate bearing capacity agree well with the experimental values.%采用纤维编织网增强混凝土（TRC）这种新型材料对结构进行修补加固不仅可以改善结构的性能，而且可以几乎不增加结构的截面尺寸。但由于纤维材料的脆性特征，在达到其极限抗拉强度时会发生拉断破坏，这对于结构来说是不安全的。为此，取单筋矩形梁研究，针对不同的纤维编织网的用量给出增强梁的两种界限破坏状态。并给出这两种状态分别对应的配网率与钢筋配筋率之间的关系。然后，基于平截面假定，给出TRC增强受弯构件在三种破坏形态下正截面极限承载能力的计算方法，包括一次受力和二次受力的情况。最后，结合试验数据说明第一种破坏模式的不利性，且采用该方法得到的承载力计算值与试验结果吻合得较好。
Antonello, E.
2009-08-01
Arcturus is the brightest star in Bootes. The ancient Greek name Arktouros means Bear Guard. The star, however, is not close to Ursa Maior (Big She-Bear) and Ursa Minor (Little She-Bear), as the name would suggest. This curious discrepancy could be explained by the star proper motion, assuming the name Bear Guard is a remote cultural heritage. The proper motion analysis could allow us to get an insight also into an ancient myth regarding Ursa Maior. Though we cannot explain scientifically such a myth, some interesting suggestions can be obtained about its possible origin, in the context of the present knowledge of the importance of the cult of the bear both during the Palaeolithic times and for several primitive populations of modern times, as shown by the ethnological studies.
Analysis of Two-Layered Journal Bearing Lubricated with Ferrofluid
Rao T. V. V. L. N.
2014-07-01
Full Text Available The present study investigates the load capacity and friction coefficient for a two-layered journal bearing lubricated with ferrofluid. A modified Reynolds equation for a two-layered ferrofluid is derived using displaced infinitely long wire magnetic field model. Reynolds boundary conditions are used to obtain nondimensional pressure and shear stress expressions. Nondimensional load capacity and coefficient of friction are analyzed under the influence of lubricant layer’s thickness, viscosities, magnetic field intensity and distance ratio parameter. Ferrofluid lubrication under the influence of magnetic field has potential to enhance load carrying capacity and reduce coefficient of friction for two-layered journal bearing.
Asnani, Himanshu; Weissman, Tsachy
2010-01-01
We consider the problem of optimal probing of states of a channel by transmitter and receiver for maximizing rate of reliable communication. The channel is discrete memoryless (DMC) with i.i.d. states. The encoder takes probing actions dependent on the message. It then uses the state information obtained from probing causally or non-causally to generate channel input symbols. The decoder may also take channel probing actions as a function of the observed channel output and use the channel state information thus acquired, along with the channel output, to estimate the message. We refer to the maximum achievable rate for reliable communication for such systems as the 'Probing Capacity'. We characterize this capacity when the encoder and decoder actions are cost constrained. To motivate the problem, we begin by characterizing the trade-off between the capacity and fraction of channel states the encoder is allowed to observe, while the decoder is aware of channel states. In this setting of 'to observe or not to o...
Wardle, F
2015-01-01
Ultra-precision bearings can achieve extreme accuracy of rotation, making them ideal for use in numerous applications across a variety of fields, including hard disk drives, roundness measuring machines and optical scanners. Ultraprecision Bearings provides a detailed review of the different types of bearing and their properties, as well as an analysis of the factors that influence motion error, stiffness and damping. Following an introduction to basic principles of motion error, each chapter of the book is then devoted to the basic principles and properties of a specific type of bearin
Outcomes & Recommendations: • Significant increase needed in the nuclear workforce both to replace soon-to-retire current generation and to staff large numbers of new units planned • Key message, was the importance of an integrated approach to workforce development. • IAEA and other International Organisations were asked to continue to work on Knowledge Management, Networks and E&T activities • IAEA requested to conduct Global Survey of HR needs – survey initiated but only 50% of operating countries (30% of capacity) took part, so results inconclusive
Compliant Foil Journal Bearing Performance at Alternate Pressures and Temperatures
Bruckner, Robert J.; Puleo, Bernadette J.
2008-01-01
An experimental test program has been conducted to determine the highly loaded performance of current generation gas foil bearings at alternate pressures and temperatures. Typically foil bearing performance has been reported at temperatures relevant to turbomachinery applications but only at an ambient pressure of one atmosphere. This dearth of data at alternate pressures has motivated the current test program. Two facilities were used in the test program, the ambient pressure rig and the high pressure rig. The test program utilized a 35 mm diameter by 27 mm long foil journal bearing having an uncoated Inconel X-750 top foil running against a shaft with a PS304 coated journal. Load capacity tests were conducted at 3, 6, 9, 12, 15, 18, and 21 krpm at temperatures from 25 to 500 C and at pressures from 0.1 to 2.5 atmospheres. Results show an increase in load capacity with increased ambient pressure and a reduction in load capacity with increased ambient temperature. Below one-half atmosphere of ambient pressure a dramatic loss of load capacity is experienced. Additional lightly loaded foil bearing performance in nitrogen at 25 C and up to 48 atmospheres of ambient pressure has also been reported. In the lightly loaded region of operation the power loss increases for increasing pressure at a fixed load. Knowledge of foil bearing performance at operating conditions found within potential machine applications will reduce program development risk of future foil bearing supported turbomachines.
Management recommendations: Bear River
US Fish and Wildlife Service, Department of the Interior — This document is a review of land management practices at the Bear River Migratory Bird Refuge, by a land use specialist. Recommendations, time frame and additional...
Basim Ajeel Abass
2015-03-01
Full Text Available In the present work the effect of bearing compliance on the performance of high speed misaligned journal bearing lined with a compliant PTFE liner lubricated with bubbly oil at high speeds has been studied. The effect of induced oil film temperature due to shearing effect has been implemented. Hydrodynamic effect of the complaint bearing and the influence of aerated oil have been examined by the classical thermohydrodynamic lubrication theory modified to include the effect of oil film turbulence and oil film temperature with suitable models for bubbly oil viscosity and density. The effect of liner elastic deformation has been implemented by using Winkler model. The effects of variable density and specific heat on the most importantbearing parameters such as maximum pressure, maximum temperature, bearing load carrying capacity and power losses have been investigated.The results obtained show that the oil film pressure and load carrying capacity increased for the bearing lubricated with bubbly oil of higher aeration level and smaller size of air bubbles. Including the effect of elastic deformation of the bearing liner reduces the oil film pressure, load carrying capacity and frictional power loss for the misaligned bearing working at the same circumstances
Weinberg, Brian (Inventor); Mavroidis, Constantinos (Inventor); Vranish, John M. (Inventor)
2011-01-01
A gear bearing drive provides a compact mechanism that operates as an actuator providing torque and as a joint providing support. The drive includes a gear arrangement integrating an external rotor DC motor within a sun gear. Locking surfaces maintain the components of the drive in alignment and provide support for axial loads and moments. The gear bearing drive has a variety of applications, including as a joint in robotic arms and prosthetic limbs.
Harris, Tedric A
2001-01-01
One of the most well-known experts in the field brings cutting-edge research to practitioners in the new edition of this important reference. Covers the improved mathematical calculations for rolling bearing endurance developed by the American Society of Mechanical Engineers and the Society of Lubrication and Tribology Engineers. Updated with new material on Condition-Based Maintenance, new testing methods, and new bearing materials.
钱佳楠
2005-01-01
@@ As Valentine's Day came closer,every shop was full of colourful gifts such as cookies in the shape of heart, chocolates,Teddy Bears and so on.When I step into a shop on February 14th,I felt most lonely as I was alone.With mv eves fixed on a lovely Teddy Bear, I wished that someone could send me this stuffed toy.
The Bearing Capacity of Circular Footings in Sand
Krabbenhøft, Sven; Clausen, Johan; Damkilde, Lars
2012-01-01
This paper presents the results of a series of triaxial tests with dry sand at confining pressures varying from 1.5 kPa to 100 kPa at relative densities of 0.20, 0.59 and 0.84. The results, which are in reasonable accordance with an equation given by Bolton, show that the friction angle is strong...
Load-bearing capacity of perforated trapezoidal sheeting
Misiek, Thomas; Saal, Helmut
2010-01-01
Thin-walled perforated sheeting is used for sound absorption in buildings. The perforation may extend over the whole surface or only parts of the sheeting, e.g. webs. So far only reduction factors for the in-plane stiffness and the bending stiffness of fully perforated sheets with an equilateral triangular perforation pattern are included in EN 1993-1-3 and EN 1999-1-4. These factors only apply to perforation patterns in form of equilateral triangles, because of the isotropy assumed during de...
Climate Drives Polar Bear Origins
In their provocative analysis of northern bears (“Nuclear genomic sequences reveal that polar bears are an old and distinct bear lineage,” Reports, 20 April, p. 344), F. Hailer et al. use independent nuclear loci to show that polar bears originated during the middle Pleistocene, rather than during t...
Modeling of Tilting-Pad Journal Bearings with Transfer Functions
J. A. Vázquez
2001-01-01
Full Text Available Tilting-pad journal bearings are widely used to promote stability in modern rotating machinery. However, the dynamics associated with pad motion alters this stabilizing capacity depending on the operating speed of the machine and the bearing geometric parameters, particularly the bearing preload. In modeling the dynamics of the entire rotor-bearing system, the rotor is augmented with a model of the bearings. This model may explicitly include the pad degrees of freedom or may implicitly include them by using dynamic matrix reduction methods. The dynamic reduction models may be represented as a set of polynomials in the eigenvalues of the system used to determine stability. All tilting-pad bearings can then be represented by a fixed size matrix with polynomial elements interacting with the rotor. This paper presents a procedure to calculate the coefficients of polynomials for implicit bearing models. The order of the polynomials changes to reflect the number of pads in the bearings. This results in a very compact and computationally efficient method for fully including the dynamics of tilting-pad bearings or other multiple degrees of freedom components that interact with rotors. The fixed size of the dynamic reduction matrices permits the method to be easily incorporated into rotor dynamic stability codes. A recursive algorithm is developed and presented for calculating the coefficients of the polynomials. The method is applied to stability calculations for a model of a typical industrial compressor.
Numerical investigation of cavitation flow in journal bearing geometry
Riedel, M.; Schmidt, M.; Stücke, P.
2013-04-01
The appearance of cavitation is still a problem in technical and industrial applications. Especially in automotive internal combustion engines, hydrodynamic journal bearings are used due to their favourable wearing quality and operating characteristics. Cavitation flows inside the bearings reduces the load capacity and leads to a risk of material damages. Therefore an understanding of the complex flow phenomena inside the bearing is necessary for the design development of hydrodynamic journal bearings. Experimental investigations in the fluid domain of the journal bearing are difficult to realize founded by the small dimensions of the bearing. In the recent years more and more the advantages of the computational fluid dynamics (CFD) are used to investigate the detail of the cavitation flows. The analysis in the paper is carried out in a two-step approach. At first an experimental investigation of journal bearing including cavitation is selected from the literature. The complex numerical model validated with the experimental measured data. In a second step, typically design parameters, such as a groove and feed hole, which are necessary to distribute the oil supply across the gap were added into the model. The paper reflects on the influence of the used design parameters and the variation of the additional supply flow rate through the feed hole regarding to cavitation effects in the bearing. Detailed pictures of the three-dimensional flow structures and the cavitation regions inside the flow film of the bearing are presented.
Numerical investigation of cavitation flow in journal bearing geometry
Stücke P.
2013-04-01
Full Text Available The appearance of cavitation is still a problem in technical and industrial applications. Especially in automotive internal combustion engines, hydrodynamic journal bearings are used due to their favourable wearing quality and operating characteristics. Cavitation flows inside the bearings reduces the load capacity and leads to a risk of material damages. Therefore an understanding of the complex flow phenomena inside the bearing is necessary for the design development of hydrodynamic journal bearings. Experimental investigations in the fluid domain of the journal bearing are difficult to realize founded by the small dimensions of the bearing. In the recent years more and more the advantages of the computational fluid dynamics (CFD are used to investigate the detail of the cavitation flows. The analysis in the paper is carried out in a two-step approach. At first an experimental investigation of journal bearing including cavitation is selected from the literature. The complex numerical model validated with the experimental measured data. In a second step, typically design parameters, such as a groove and feed hole, which are necessary to distribute the oil supply across the gap were added into the model. The paper reflects on the influence of the used design parameters and the variation of the additional supply flow rate through the feed hole regarding to cavitation effects in the bearing. Detailed pictures of the three-dimensional flow structures and the cavitation regions inside the flow film of the bearing are presented.
On The Modeling Of Hybrid Aerostatic - Gas Journal Bearings
Morosi, Stefano; Santos, Ilmar
2010-01-01
compressible fluid film journal bearing. Control forces are generated by injecting pressurized air into the bearing gap through orifices located on the bearing walls. A modified form of the compressible Reynolds equation for active lubrication is derived. By solving this equation, stiffness and damping......Gas journal bearing have been increasingly adopted in modern turbo-machinery applications, as they meet the demands of operation at higher rotational speeds, in clean environment and great efficiency. Due to the fact that gaseous lubricants, typically air, have much lower viscosity than more...... conventional oil bearings, carrying capacity and dynamic characteristics of passive systems are generally poorer. In order to enhance these characteristics, one solution is to employ active control strategies. The present contribution presents a detailed mathematical modeling for active lubrication of a...
Numerical simulation and experimental research on passive hydrodynamic bearing in a blood pump
Han, Qing; Ruan, Xiaodong; Chen, Wenyu; Fu, Xin
2013-09-01
The current research of hydrodynamic bearing in blood pump mainly focuses on the bearing structure design. Compared with the typical plane slider bearing and Rayleigh step bearing, spiral groove bearing has excellent performance in load-carrying capacity. However, the load-carrying capacity would decrease significantly with increasing flow rate in conventional designs. In this paper, the special treatment is made to the upper spiral groove bearing to make sure that both the circulatory flowing and load-carrying capacity are high. Three-dimensional computational fluid dynamics(CFD) models in the space between rotor and shaft are developed by using FLUENT software. Effects of groove number, film height and groove depth on load-carrying capacity of the spiral groove bearings are investigated by orthogonal experiment design. The experimental results show that film height is the most remarkable factor to the load-carrying capacity. The variation tendency of load-carrying capacity reveals that the best combination of geometry is the one with groove number of 8, film height 0.03 mm and groove depth 0.08 mm. The velocity and pressure distributions in spiral groove bearings are also analyzed, and the analysis result shows that the distributions are in conformity with the design of the blood pump based on the principle of hydrodynamic bearing. The displacement of the rotor with the best combination parameters is tested by using laser displacement sensors, the testing result shows that the suspending performance is satisfactory both in axial and radial directions. This research proposes a bearing design method which has sufficient load-carrying capacity to support rotor as an effective passive hydrodynamic bearing.
Vranish, John M. (Inventor)
2010-01-01
A partial gear bearing including an upper half, comprising peak partial teeth, and a lower, or bottom, half, comprising valley partial teeth. The upper half also has an integrated roller section between each of the peak partial teeth with a radius equal to the gear pitch radius of the radially outwardly extending peak partial teeth. Conversely, the lower half has an integrated roller section between each of the valley half teeth with a radius also equal to the gear pitch radius of the peak partial teeth. The valley partial teeth extend radially inwardly from its roller section. The peak and valley partial teeth are exactly out of phase with each other, as are the roller sections of the upper and lower halves. Essentially, the end roller bearing of the typical gear bearing has been integrated into the normal gear tooth pattern.
WORK PRINCIPLE AND CHARACTERISTIC ANALYSES OF HYDROSTATIC BEARING
无
2002-01-01
Aiming at the new characteristic of water hydraulic system, a kind of hydrostatic bearing with a concentric gap damper is introduced. The lubricative film thickness of the hydrostatic bearing possesses inflexibility and the loading capacity is just determined by the geometrical dimension of the piston-slipper subassembly and has no relation with system pressure, viscosity and temperature of water and speed of rotor. Theoretical analyses and the verification of scheme done at the test rig show that the hydrostatic bearing with a concentric gap damper is especially fit for water hydraulic components.
Aber, Gregory S. (Inventor)
2000-01-01
An apparatus is provided for a blood pump bearing system within a pump housing to support long-term highspeed rotation of a rotor with an impeller blade having a plurality of individual magnets disposed thereon to provide a small radial air gap between the magnets and a stator of less than 0.025 inches. The bearing system may be mounted within a flow straightener, diffuser, or other pump element to support the shaft of a pump rotor. The bearing system includes a zirconia shaft having a radiused end. The radiused end has a first radius selected to be about three times greater than the radius of the zirconia shaft. The radiused end of the zirconia shaft engages a flat sapphire endstone. Due to the relative hardness of these materials a flat is quickly produced during break-in on the zirconia radiused end of precisely the size necessary to support thrust loads whereupon wear substantially ceases. Due to the selection of the first radius, the change in shaft end-play during pump break-in is limited to a total desired end-play of less than about 0.010 inches. Radial loads are supported by an olive hole ring jewel that makes near line contact around the circumference of the Ir shaft to support big speed rotation with little friction. The width of olive hole ring jewel is small to allow heat to conduct through to thereby prevent heat build-up in the bearing. A void defined by the bearing elements may fill with blood that then coagulates within the void. The coagulated blood is then conformed to the shape of the bearing surfaces.
Force and stiffness characteristics of superconducting bearing prototype
The radial-axial superconducting bearing prototype was designed, fabricated and tested. The YBaCuO high-temperature superconducting (HTS) monodomain disks diameter 28 mm and thickness of h = 4; 6; 8; 10 mm, capable to trap magnetic field 1 T, were fabricated to be employed in bearing prototype. Force interaction of single field cooled HTS disks with NdFeB magnets depending on disk thickness under 1 mm magnet air gap was studied. It was found that the increase in disk thickness results in reducing radial stiffness and in growing axial one. The results obtained were used for optimization of HTS-PM arrangement, and for developing the bearing design. The designed bearing incorporates a rotor with 7 HTS disks of 4 mm thickness, total mass 90 g, and stator with two pairs of permanent annular magnets of NdFeB. It is established that the force-displacement dependencies of the bearing have three zones: non-hysteresis (elastic) zone with high stiffness up to 560 N/mm; zone of elastic interaction with stiffness 190 N/mm; hysteretic zone with stiffness 150 N/mm in which a rotor residual displacement being observed after unloading. The outer bearing diameter is 130 mm, thickness 30 mm, and mass 1.8 kg. The maximal radial load capacity of the bearing is 190 N at the rotor displacement of 1.3 mm, and the maximal axial load capacity is 85 N at the displacement of 1 mm
Vranish, John M. (Inventor)
2009-01-01
A gearing system using modular gear bearing components. Each component is composed of a core, one or more modules attached to the core and two or more fastening modules rigidly attaching the modules to the core. The modules, which are attached to the core, may consist of gears, rollers or gear bearing components. The core orientation affects the orientation of the modules attached to the core. This is achieved via the keying arrangement of the core and the component modules that attach to the core. Such an arrangement will also facilitate the phase tuning of gear modules with respect to the core and other gear modules attached to the core.
Method to Increase Performance of Foil Bearings Through Passive Thermal Management
Bruckner, Robert
2013-01-01
This invention is a new approach to designing foil bearings to increase their load capacity and improve their reliability through passive thermal management. In the present case, the bearing is designed in such a way as to prevent the carryover of lubricant from the exit of one sector to the inlet of the ensuing sector of the foil bearing. When such passive thermal management techniques are used, bearing load capacity is improved by multiples, and reliability is enhanced when compared to current foil bearings. This concept has recently been tested and validated, and shows that load capacity performance of foil bearings can be improved by a factor of two at relatively low speeds with potentially greater relative improvements at higher speeds. Such improvements in performance with respect to speed are typical of foil bearings. Additionally, operation of these newly conceived bearings shows much more reliability and repeatable performance. This trait can be exploited in machine design to enhance safety, reliability, and overall performance. Finally, lower frictional torque has been demonstrated when operating at lower (non-load capacity) loads, thus providing another improvement above the current state of the art. The objective of the invention is to incorporate features into a foil bearing that both enhance passive thermal management and temperature control, while at the same time improve the hydrodynamic (load capacity) performance of the foil bearing. Foil bearings are unique antifriction devices that can utilize the working fluid of a machine as a lubricant (typically air for turbines and motors, liquids for pumps), and as a coolant to remove excess energy due to frictional heating. The current state of the art of foil bearings utilizes forced cooling of the bearing and shaft, which represents poor efficiency and poor reliability. This invention embodies features that utilize the bearing geometry in such a manner as to both support load and provide an inherent and
Christiansen, Christian Kim; Klit, Peder; Walther, Jens Honore;
2015-01-01
making it prone to cavitation which again affects the load carrying capacity of the bearing. In combustion engines the journal bearing plays a vital role especiallyas main and crosshead bearings transmitting the combustion forces. Those forces vary highly during one combustion cycle which is further...
Development of Flexible Bearing
K.S.Mohanraj
2014-06-01
Full Text Available Elastomeric base isolation systems are proven to be effective in reducing seismic forces transmitted to buildings. However, due to their cost, the use of these devices is currently limited to large and expensive buildings. A fiber reinforced elastomeric isolator utilizes fiber fabric, such as carbon fiber, glass fibre, and etc. as the reinforcement material instead of solid steel plates. The fibre fabric reinforcement is extensible in tension and has no flexural rigidity. Elastomers normally used in the isolator are natural rubber; neoprene, butyl rubber and nit rile rubber etc. These devices were fabricated by binding alternating layers of rubber and fibre mesh. The fibre mesh is used to increase the vertical stiffness of the bearings while maintaining low lateral stiffness. Characterizing the behaviour of a fibre reinforced bearing “shape factor” of the bearing, Poisson’s ratio of the elastomeric material and flexibility of the reinforcing sheets and investigate the effect of reinforcement flexibility on compressive behaviour of elastomeric bearings with different geometrical and material properties. Bonding with fibre reinforcements can increase the stiffness of elastic layers only when the elastic layer is compressed.
On the design and development of a miniature ceramic gimbal bearing
Hanson, Robert A.; Odwyer, Barry; Gordon, Keith M.; Jarvis, Edward W.
1990-01-01
A review is made of a program to develop ceramic gimbal bearings for a miniaturized missile guidance system requiring nonmagnetic properties and higher load capacity than possible with conventional AISI 440C stainless steel bearings. A new gimbal design concept is described which utilizes the compressive strength and nonmagnetic properties of silicon nitride (Si3N4) ceramics for the gimbal bearing. Considerable manufacturing development has occurred in the last 5 years making ceramic bearings a viable option in the gimbal design phase. A preliminary study into the feasibility of the proposed design is summarized. Finite element analysis of the brittle ceramic bearing components under thermal stress and high acceleration loading were conducted to ensure the components will not fail catastrophically in service. Finite element analysis was also used to optimize the adhesive joint design. Bearing torque tests run at various axial loads indicate that the average running torque of ceramic bearings varies with load similarly to that of conventional steel bearings.
Flexure Bearing Reduces Startup Friction
Clingman, W. Dean
1991-01-01
Design concept for ball bearing incorporates small pieces of shim stock, wire spokes like those in bicycle wheels, or other flexing elements to reduce both stiction and friction slope. In flexure bearing, flexing elements placed between outer race of ball bearing and outer ring. Elements flex when ball bearings encounter small frictional-torque "bumps" or even larger ones when bearing balls encounter buildups of grease on inner or outer race. Flexure of elements reduce high friction slopes of "bumps", helping to keep torque between outer ring and inner race low and more nearly constant. Concept intended for bearings in gimbals on laser and/or antenna mirrors.
How Tapered Roller Geometry Determines Bearing Energy Efficiency
Craig Seidelson
2011-01-01
Full Text Available With annual global sales of approximately $5 billion [1], tapered roller bearing consumers increasingly valued energy efficient products [2]. Two of the world’s largest bearing producers, SKF [3] and Timken [4] promoted energy efficient bearings based on their abilities to grind rollers to reduced radial deviation from round (OOR. Bearing designers, however, did not know if roller geometries specified placed limitations on roller roundness. Testing under shop floor conditions at Timken, the researcher discovered a positive linear regression between roller nominal diameter and OOR. The basis for the regression was under geometric roller rounding conditions found to exist when through feed centreless grinding tapered rollers, synchronous regulating wheel vibrations transferred at higher amplitude to larger nominal diameter rollers. This research pointed energy efficient bearing design in a new direction. For example, tapered roller bearing designers typically specified rollers of minimum length to reduce problems associated with rolling contact. Bearings assembled from shorter rollers, to retain the same load capacity, required fewer rollers of larger nominal diameter. This research, however, found all things equal larger nominal diameter rollers suffered from increased OOR. Bearings designed to reduce power losses associated with rotational displacements benefited from employing more, smaller nominal diameter rollers.
Performance of Simple Gas Foil Thrust Bearings in Air
Bruckner, Robert J.
2012-01-01
Foil bearings are self-acting hydrodynamics devices used to support high speed rotating machinery. The advantages that they offer to process fluid lubricated machines include: high rotational speed capability, no auxiliary lubrication system, non-contacting high speed operation, and improved damping as compared to rigid hydrodynamic bearings. NASA has had a sporadic research program in this technology for almost 6 decades. Advances in the technology and understanding of foil journal bearings have enabled several new commercial products in recent years. These products include oil-free turbochargers for both heavy trucks and automobiles, high speed electric motors, microturbines for distributed power generation, and turbojet engines. However, the foil thrust bearing has not received a complimentary level of research and therefore has become the weak link of oil-free turbomachinery. In an effort to both provide machine designers with basic performance parameters and to elucidate the underlying physics of foil thrust bearings, NASA Glenn Research Center has completed an effort to experimentally measure the performance of simple gas foil thrust bearing in air. The database includes simple bump foil supported thrust bearings with full geometry and manufacturing techniques available to the user. Test conditions consist of air at ambient pressure and temperatures up to 500 C and rotational speeds to 55,000 rpm. A complete set of axial load, frictional torque, and rotational speed is presented for two different compliant sub-structures and inter-pad gaps. Data obtained from commercially available foil thrust bearings both with and without active cooling is presented for comparison. A significant observation made possible by this data set is the speed-load capacity characteristic of foil thrust bearings. Whereas for the foil journal bearing the load capacity increases linearly with rotational speed, the foil thrust bearing operates in the hydrodynamic high speed limit. In
Reliability for fluid bearings design
DIOP, Khadim; CHARKI, Abdérafi; CHAMPMARTIN, Stéphane; AMBARI, Abdelhak
2013-01-01
This paper presents a new methodology for evaluating the failure probability of fluid bearings which are sensitive components for the design of machine rotors, mechatronic systems and high precision metrology. The static and dynamic behavior of a fluid bearing depends on several parameters, such as external load, bearing dimensions, supply pressure, quality of the machined surfaces, fluid properties, etc. In this paper, the characteristics of a simple geometry thrust bearing are calculated an...
Reliability of a hydrostatic bearing
CHARKI, Abderafi; DIOP, Khadim; CHAMPMARTIN, Stéphane; AMBARI, Abdelhak
2013-01-01
This paper presents a methodology for evaluating the failure probability of fluid bearings, which are sensitive components for the design of machine rotors, mechatronic systems, and high precision metrology. The static and dynamic behavior of a fluid bearing depends on several parameters, such as external load, bearing dimensions, supply pressure, quality of the machined surfaces, fluid properties, etc. In this paper, the characteristics of a simple geometry hydrostatic bearing are calculated...
Households' Interest-bearing Assets
Ellis Connolly; Fiona Fleming; Jarkko Jääskelä
2012-01-01
Households invest around two-fifths of their financial assets in interest-bearing assets. These assets are predominantly held directly in deposits and also via superannuation and other investment funds. Deposits have grown strongly in recent years, although there has been no growth in interest-bearing securities. Compared with other advanced economies, interest-bearing assets represent a relatively small share of financial assets. For the household sector as a whole, interest-bearing assets a...
Analysis of Two-Layered Journal Bearing Lubricated with Ferrofluid
Rao T. V. V. L. N.; Rani A. M. A.; Nagarajan T.; Hashim F. M.
2014-01-01
The present study investigates the load capacity and friction coefficient for a two-layered journal bearing lubricated with ferrofluid. A modified Reynolds equation for a two-layered ferrofluid is derived using displaced infinitely long wire magnetic field model. Reynolds boundary conditions are used to obtain nondimensional pressure and shear stress expressions. Nondimensional load capacity and coefficient of friction are analyzed under the influence of lubricant layer’s thickness, viscositi...
Miriam Gonçalves Miguel
2005-07-01
Full Text Available A cidade de Londrina, Estado do Paraná, possui um perfil geotécnicoconstituído de uma camada superficial de solo argilo-siltoso, poroso, laterítico e muitas vezes colapsível, que se estende até a profundidade máxima de 12 metros. As estacas utilizadas em obras de pequeno a médio porte se encontram totalmente embutidas nesta camada, sofrendo a influência de seu comportamento laterítico e colapsível. Os métodos clássicos brasileiros de estimativa de capacidade de carga de estacas tornam-se conservadores, frente aos resultados reais, quando aplicados em solos lateríticos e, contra a segurança, quando aplicados em solos colapsíveis, isto é, na condição crítica ao colapso. Este trabalho avalia os coeficientes de ajuste das resistências de ponta e ao atrito lateral para esses métodos, no caso de estacas apiloadas, sendo estes coeficientes obtidos pela retro-análise de resultados de provas de carga estática à compressão, realizadas no Campo Experimental de Engenharia Geotécnica da Universidade Estadual de Londrina.The city of Londrina, Paraná, has a typical geotechnical profile defined by a superficial layer of porous silty clay with maximum depth of about 12 meters, that shows lateritic characteristics, andmany times, collapsibility. Casts in place piles are often used for small buildings in the region and are fully embedded in this soil layer. Therefore, this type of foundation is subjected to the lateritic and occasionally collapsible influence of soil. Brazilian pile bearing capacity methods may yield conservative results when applied to tropical soils, as far as the lateritic origin in concerned. On the other hand, it can be unsafe if collapsibility prevails. This paper evaluates coefficients to adjust both point and lateral resistance of cast in place small diameter piles in the situation described. The work was carried out at the Londrina State University Geotechnical Experimental Site, and back analysis from static
Centrifugally decoupling touchdown bearings
Post, Richard F
2014-06-24
Centrifugally decoupling mechanical bearing systems provide thin tensioned metallic ribbons contained in a support structure. This assembly rotates around a stationary shaft being centered at low speeds by the action of the metal ribbons. Tension springs are connected on one end to the ribbons and on the other end to the support structure. The ribbons pass through slots in the inner ring of the support structure. The spring preloading thus insures contact (or near-contact) between the ribbons and the shaft at rotation speeds below the transition speed. Above this speed, however, the centrifugal force on the ribbons produces a tensile force on them that exceeds the spring tensile force so that the ribbons curve outward, effectively decoupling them from mechanical contact with the shaft. They still remain, however, in position to act as a touchdown bearing in case of abnormally high transverse accelerations.
1993-01-01
The u.s. government bulks large in the nation's financial markets. The huge volume of government-issued and -sponsored debt affects the pricing and volume ofprivate debt and, consequently, resource allocation between competing alternatives. What is often not fully appreciated is the substantial influence the federal government wields overresource allocation through its provisionofcreditandrisk-bearing services to the private economy. Because peopleand firms generally seekto avoid risk, atsomeprice they are willing to pay another party to assume the risk they would otherwise face. Insurance companies are a class of private-sector firms one commonly thinks of as providing these services. As the federal government has expanded its presence in the U.S. economy during this century, it has increasingly developed programs aimed at bearing risks that the private sector either would not take on at any price, or would take on but atapricethoughtto besogreatthatmostpotentialbeneficiarieswouldnotpurchase the coverage. To...
Rotating plug bearing and seal
Wade, Elman E.
1977-01-01
A bearing and seal structure for nuclear reactors utilizing rotating plugs above the nuclear reactor vessel. The structure permits lubrication of bearings and seals of the rotating plugs without risk of the lubricant draining into the reactor vessel below. The structure permits lubrication by utilizing a rotating outer race bearing.
Rotating plug bearing and seal
Disclosed is a bearing and seal structure for nuclear reactors utilizing rotating plugs above the nuclear reactor vessel. The structure permits lubrication of bearings and seals of the rotating plugs without risk of the lubricant draining into the reactor vessel below. The structure permits lubrication by utilizing a rotating outer race bearing. 19 claims, 3 figures
Static characteristic analysis on a hydrodynamic bearing of a hydraulic suspended micropump
A hydraulic suspended micropump was designed based on the conception of double suction impeller. To study the running performance of the micropump, three dimensional simulation of the static characteristic of the hydrodynamic bearing at rated condition was performed. Parameters such as the eccentricity and rotational speed, having effect on the bearing capacity, were analyzed. Results show that the eccentricity and rotational speed have a certain effect on the bearing capacity. The region of the maximum static pressure and the positive pressure changes as the eccentricity increases. The bearing capacity improves as the rotational speed increases. All the results can provide a academic basis for the improvement and application of a hydrodynamic bearing of a micropump
Ian BICKLE
2012-01-01
(Refer to page 186)Answer: Bear Paw sign of Xanthogranulomatous PyelonephritisThe contrast enhanced (portal venous phase)CT of the abdomen showed a global enlargement of the right kidney. There are multiplelow attenuation areas in the renal parenchyma, in a ‘hydronephrotic type manner’, but with no true hydronephrosis. This is due to a renal calculus lying in a contracted pelvis with dilated calyces that contain inflammatory debris. A rim of normal renal tissue enhancesperipherally. The appea...
Bearing Behaviors of Stiffened Deep Cement Mixed Pile
WU Mai; ZHAO Xin
2006-01-01
A series of investigations were conducted to study the bearing capacity and load transfer mechanism of stiffened deep cement mixed (SDCM) pile.Laboratory tests including six specimens were conducted to investigate the frictional resistance between the concrete core and the cementsoil.Two model piles and twenty-four full-scale piles were tested to examine the bearing behavior of single pile.Laboratory and model tests results indicate that the cohesive strength is large enough to ensure the interaction between core pile and the outer cement-soil.The full-scale test results show that the SDCM piles exhibit similar bearing behavior to bored and cast-in-place concrete piles.In general, with the rational composite structure the SDCM piles can transmit the applied load effectively, and due to the addition of the stiffer core, the SDCM piles possess high bearing capacity.Based on the findings of these experimental investigations and theoretical analysis, a practical design method is developed to predict the vertical bearing capacity of SDCM pile.
Study on the seismic performance of a double spherical seismic isolation bearing
Peng Tianbo; Li Jianzhong; Xu Yan; Fan Lichu
2008-01-01
In this paper,the configuration and working mechanism of the recently developed double spherical seismic isolation (DSSI) bearing are introduced in detail.Then,vertical displacement of the DSSI bearing due to sliding on a spherical surface is analyzed.The results from seismic performance testing of the bearing are given,and a numerical analysis of a four span continuous girder bridge is performed.The numerical analysis compares the influence of three different bearing arrangement schemes on the structural seismic response,and the results show that the DSSI bearing is effective in increasing the vertical load bearing capacity,reducing the vertical displacement,and controlling the energy dissipation capacity within a certain range.
Design charts for arbitrarily pivoted, liquid-lubricated flat-sector-pad thrust bearing
Etsion, I.
1977-01-01
A flat, sector-shaped geometry for a liquid-lubricated thrust bearing is analyzed considering both the pitch and roll of the pad. Results are presented in design charts that enable a direct approach to the design of point- and line-pivoted, tilting pad bearings. A comparison is made with the Mitchell bearing approximation and it is found that this approximation always overestimates load capacity.
Bear Creek Project. Final environmental statement
The Bear Creek Project consists of certain mining and milling operations involving uranium ore deposits located in Converse County, Wyoming. Mining of uranium from nine known ore bodies will take place over a period of ten years (estimated); a mill with a nominal capacity of 1000 tons per day of ore will be constructed and operated as long as ore is available. The waste material (tailings) from the mill, also produced at a rate of about 1000 tons per day, will be stored onsite in an impoundment. Environmental impacts and adverse effects are summarized
Vranish, John M. (Inventor)
2009-01-01
A gear bearing having a first gear and a second gear, each having a plurality of teeth. Each gear operates on two non-parallel surfaces of the opposing gear teeth to perform both gear and bearing functions simultaneously. The gears are moving at substantially the same speed at their contact points. The gears may be roller gear bearings or phase-shifted gear bearings, and may be arranged in a planet/sun system or used as a transmission. One preferred embodiment discloses and describes an anti-backlash feature to counter ''dead zones'' in the gear bearing movement.
Numerical analysis of bump foil bearings without nominal radial clearance
LIU Zhan-sheng; XU Huai-jin; ZHANG Guang-hui
2008-01-01
Bump foil bearings without nominal radial clearance were analyzed. An air film thickness model and a bearing theoretical analytical model were developed accounting for air compressibility and foil deformation. To analyze hydrodynamic characteristics of bump foil beatings with different operating eccentricities, the air film thickness equation and Reynolds equation were coupled through pressure and solved by Newton-Raphson Method(NRM) and Finite Difference Method (FDM). The characteristics of an bump foil bearing model were dis-cussed including load carrying capacity, film thickness and pressure distributions. The results of simulation show that bump foil beating without nominal radial clearance can provide better stability and greater load capaci-ty. This numerical analytical method also reveals a good convergence in numerical calculation.
Ultimate Flexural Capacity of Unbounded Prestressed Concrete Pier
Wang Hui-li; Zhang Lin; Qin Si-Feng
2014-01-01
Based on the plastic-hinge method, the influence of different factors on the ultimate flexural capacity is analyzed, including relationship between the ultimate bearing capacity and prestressing tendon area, the regular reinforcement area, the strength of concrete and other influence factors. The results show that, the increase in the area of regular reinforcement and the strength of concrete can enhance the ultimate flexural capacity. Moreover, the ultimate bending moment increases first and...
Simulation of the fluid structure interaction for an aerostatic bearing and a flexible substrate
Olieslagers, R.; Wild, M. de; Melick, S. van; Knaapen, R.
2014-01-01
The fluid structure interaction for an aerostatic bearing and a substrate is solved numerically by a semi-analytical model, programmed in the software package MATLAB. This semi-analytical model uses a fluidic network of resistances and capacities to solve the pressure field in the bearing channel. T
Introgressive hybridization: brown bears as vectors for polar bear alleles.
Hailer, Frank
2015-03-01
The dynamics and consequences of introgression can inform about numerous evolutionary processes. Biologists have therefore long been interested in hybridization. One challenge, however, lies in the identification of nonadmixed genotypes that can serve as a baseline for accurate quantification of admixture. In this issue of Molecular Ecology, Cahill et al. (2015) analyse a genomic data set of 28 polar bears, eight brown bears and one American black bear. Polar bear alleles are found to be introgressed into brown bears not only near a previously identified admixture zone on the Alaskan Admiralty, Baranof and Chichagof (ABC) Islands, but also far into the North American mainland. Elegantly contrasting admixture levels at autosomal and X chromosomal markers, Cahill and colleagues infer that male-biased dispersal has spread these introgressed alleles away from the Late Pleistocene contact zone. Compared to a previous study on the ABC Island population in which an Alaskan brown bear served as a putatively admixture-free reference, Cahill et al. (2015) utilize a newly sequenced Swedish brown bear as admixture baseline. This approach reveals that brown bears have been impacted by introgression from polar bears to a larger extent (up to 8.8% of their genome), than previously known, including the bear that had previously served as admixture baseline. No evidence for introgression of brown bear into polar bear is found, which the authors argue could be a consequence of selection. Besides adding new exciting pieces to the puzzle of polar/brown bear evolutionary history, the study by Cahill and colleagues highlights that wildlife genomics is moving from analysing single genomes towards a landscape genomics approach. PMID:25775930
The Effect of Additives on The Performance of HydrostaticThrust Bearings
Muhammed Abdul Sattar; Albert E. Yousif
2008-01-01
The paper is concerned with, the behavior of the hydrostatic thrust bearings lubricated with liquid-solid lubricants using Einstein viscosity formula, and taking into account the centrifugal force resulting from high speed. Also studied is the effect of the bearing dimensions on the pressure, flow rate, load capacity, shear stress, power consumption and stiffness. The theoretical results show an increase in load capacity by (8.3%) in the presence of solid graphite particles with concentration...
Barth, M.J.
1984-11-01
Two commonly used Extended Kalman Filter tracking algorithms utilize the Relative Cartesian and Modified Polar coordinate systems. This report compares the two algorithms by exercising a destroyer-Submarine (DD/SS) computer simulation. A simple engagement geometry is employed which encompasses the major DD/SS options available. Error statistics are developed by Monte Carlo methods. Results are presented which show that the circular error depends upon the diagonal values of the error covariance matrix. The results also support (but do not establish) that the optimum DD manuevuer is that which minimizes the range while maximizing the bearing rate. 4 refs., 5 figs., 4 tabs.
Self lubricating fluid bearings
The invention concerns self lubricating fluid bearings, which are used in a shaft sealed system extending two regions. These regions contain fluids, which have to be isolated. A first seal is fluid tight for the first region between the carter shaft and the shaft. The second seal is fluid tight between the carter and the shaft, it communicates with the second region. The first fluid region is the environment surrounding the shaft carter. The second fluid region is a part of a nuclear reactor which contains the cooling fluid. The shaft is conceived to drive a reactor circulating and cooling fluid
Superconducting bearings in flywheels
Coombs, T.A.; Campbell, A.M.; Ganney, I.; Lo, W. [Cambridge Univ. (United Kingdom). Interdisciplinary Research Centre in Superconductivity (IRC); Twardowski, T. [International Energy Systems, Chester High Road, Neston, South Wirral (United Kingdom); Dawson, B. [British Nuclear Fuels, Capenhurst, South Wirral (United Kingdom)
1998-05-01
Investigations are being carried out into the use of superconducting magnetic bearings to levitate energy storage flywheels. In a planned program of work, Cambridge University are aiming to produce a practical bearing system for Pirouette(TM). The Pirouette(TM) system is designed to provide 5 kWh of recoverable energy which is currently recoverable at a rate of 5 kW (future revisions will provide up to 50 kW). IES (a British Nuclear Fuels subsidiary) the owners of the Pirouette(TM) machine have supplied Cambridge with a flywheel. This flywheel weighs >40 kg and is being levitated using an Evershed-type arrangement in which the superconductor is being used to stabilize the interaction between two magnets. To date we have demonstrated stable levitation in static and low speed tests in a rig designed for low speeds of rotation in air. A second rig which is currently under construction at BNFL will run in vacuum at speeds of up to 50 (orig.) 5 refs.
Superconducting bearings in flywheels
Investigations are being carried out into the use of superconducting magnetic bearings to levitate energy storage flywheels. In a planned program of work, Cambridge University are aiming to produce a practical bearing system for Pirouette(TM). The Pirouette(TM) system is designed to provide 5 kWh of recoverable energy which is currently recoverable at a rate of 5 kW (future revisions will provide up to 50 kW). IES (a British Nuclear Fuels subsidiary) the owners of the Pirouette(TM) machine have supplied Cambridge with a flywheel. This flywheel weighs >40 kg and is being levitated using an Evershed-type arrangement in which the superconductor is being used to stabilize the interaction between two magnets. To date we have demonstrated stable levitation in static and low speed tests in a rig designed for low speeds of rotation in air. A second rig which is currently under construction at BNFL will run in vacuum at speeds of up to 50 (orig.)
Computational design of rolling bearings
Nguyen-Schäfer, Hung
2016-01-01
This book comprehensively presents the computational design of rolling bearings dealing with many interdisciplinary difficult working fields. They encompass elastohydrodynamics (EHD), Hertzian contact theory, oil-film thickness in elastohydrodynamic lubrication (EHL), bearing dynamics, tribology of surface textures, fatigue failure mechanisms, fatigue lifetimes of rolling bearings and lubricating greases, Weibull distribution, rotor balancing, and airborne noises (NVH) in the rolling bearings. Furthermore, the readers are provided with hands-on essential formulas based on the up-to-date DIN ISO norms and helpful examples for computational design of rolling bearings. The topics are intended for undergraduate and graduate students in mechanical and material engineering, research scientists, and practicing engineers who want to understand the interactions between these working fields and to know how to design the rolling bearings for automotive industry and many other industries.
周旺保; 蒋丽忠
2011-01-01
Based on the equilibrium condition of several sections, the stress-strain relationship of the concrete-filled steel tube under the effect of confinement and the influence of the initial bending and shear, the equilibrium equation of the section was established. At the same time, the numerical method for calculating the elastic-plastic ultimate loads of the concrete-filled tubular laced columns was presented by adopting the Taylor's series as the piecewise interpolation function and the corresponding computer program was compiled. Some axial compressed four-tube concrete-filled steel tubular taced columns were computed using the numerical method and the program, and the results were compared with the calculation results of some existing codes. The calculation formula of slender ratio reduced coefficient was proposed combining numerical calculation results and the slender ratio reduced coefficient model. The calculation results were compared with the numerical calculation results and the test results. The results show that this method is suitable for the elastoplasticity ultimate bearing capacity calculation of the long and short axial compressed columns. The code computational methods are conservative, the computational errors are great, and the computed results in this article agree well with the test results. The rationality of slender ratio reduced coefficient calculation formula has been attested.%采用泰勒级数作为分段插值函数,在考虑多个截面的平衡条件和紧箍效应钢管混凝土应力-应变关系、剪切变形及初弯曲影响的基础上,建立杆件截面的平衡方程,提出四肢缀条轴压钢管混凝士格构柱弹塑性极限承载力数值方法,并编制相应的计算程序.利用提出的计算方法和编制的程序对国内已有轴压四肢钢管混凝土格构柱试件进行计算,并与现有一些规程进行比较.同时,结合数值计算结果及长细比折减系数计算模型,提出长细比折减系数计
付崇建; 郁冰冰; 杨连甲; 曹新生; 张立藩
2007-01-01
of simulated weightlessness on bone marrow stromal cell count and osteogentic capacity of weight bearing bone in rats so as to reveal the mechanism of bone loss.DESIGN : Randomized pairing and controlled study.SETTING: College of Aerospace Medicine and Department of Pathology of Stomatology College, the Fourth Military Medical University of Chinese PLA.MATERIALS: A total of 20 adult healthy male SD rats were selected in this study. At the beginning of experiment, rats based on their body mass were randomly divided into control group and suspension group with 10 in each group. Alkaline phosphatase kit was provided by Beijing Zhongsheng Bioengineering High-technological Company.METHODS: The experiment was carried out in the Department of Pathology, Collage of Stomatology, the Fourth Military Medical University of Chinese PLA from November 1999 to July 2000. Rats were randomly divided into tail suspension group and control group with 10 in each group. Rats in the tail suspension group were given tail suspension for 28 days. Their heads maintained 30° low position, and their hindlimbs freely suspended and were not given weight loading. While, rats in the control group were fed normally. At the end of experiment, bone marrow stromal cells were obtained from femur for primary and transferring cultures.MAIN OUTCOME MEASURES: Cell counting and methylthianolyldiphenyl-tetrazolium bromide (MTT) assay were used to draw growth curve of cells in primary and transferring cultures and to measure activity of alkaline phosphatase and forming quantity of mineralized nodules in vitro.RESULTS : ① Activity of alkaline phosphatase: Activity of alkaline phosphatase of cells in the primary and transferring cultures in the suspension group was lower than that in the control group, and there was significant difference between them (P＜0.05). ② Forming quantity of mineralized nodules: Forming quantity of mineralized nodules in the suspension group was less than that in the control group
Grease lubrication in rolling bearings
Lugt, Piet M
2012-01-01
The definitive book on the science of grease lubrication for roller and needle bearings in industrial and vehicle engineering. Grease Lubrication in Rolling Bearings provides an overview of the existing knowledge on the various aspects of grease lubrication (including lubrication systems) and the state of the art models that exist today. The book reviews the physical and chemical aspects of grease lubrication, primarily directed towards lubrication of rolling bearings. The first part of the book covers grease composition, properties and rheology, including thermal
Della-Corte, Christopher
2012-01-01
Foil gas bearings are a key technology in many commercial and emerging oilfree turbomachinery systems. These bearings are nonlinear and have been difficult to analytically model in terms of performance characteristics such as load capacity, power loss, stiffness, and damping. Previous investigations led to an empirically derived method to estimate load capacity. This method has been a valuable tool in system development. The current work extends this tool concept to include rules for stiffness and damping coefficient estimation. It is expected that these rules will further accelerate the development and deployment of advanced oil-free machines operating on foil gas bearings.
Hydrostatic and hybrid bearing design
Rowe, W B
1983-01-01
Hydrostatic and Hybrid Bearing Design is a 15-chapter book that focuses on the bearing design and testing. This book first describes the application of hydrostatic bearings, as well as the device pressure, flow, force, power, and temperature. Subsequent chapters discuss the load and flow rate of thrust pads; circuit design, flow control, load, and stiffness; and the basis of the design procedures and selection of tolerances. The specific types of bearings, their design, dynamics, and experimental methods and testing are also shown. This book will be very valuable to students of engineering des
Palacios, Patsy; Luecke, Chris; Robinson, Justin
2007-01-01
There are 13 species of fish found in the waters of Bear Lake. Of those 13, 4 are endemic (found only in Bear Lake). The 4 endemics species are Bonneville cisco, Bonneville whitefish, Bear Lake whitefish, and Bear Lake sculpin. Five of the remaining 9 fish species are native to the region, and 4 are exotic introductions. These native fishes are the Bonneville cutthroat trout, Utah sucker, redside shiner, speckled dace and Utah chub. The exotic fishes are lake trout, common carp, yellow p...
Dynamic Analysis of Engine Bearings
H. Hirani
1999-01-01
Full Text Available This paper presents a simple methodology to evaluate the stiffness and damping coefficients of an engine bearing over a load cycle. A rapid technique is used to determine the shaft ‘limit cycle’ under engine dynamic loads. The proposed theoretical model is based on short and long bearing approximations. The results obtained by present approximation are compared with those obtained by numerical method. The influence of thermal effects on the stiffness and damping coefficients is predicted by using a simplified thermal analysis. In order to illustrate the application of the proposed scheme, one engine main bearing and a connecting rod bearing are analysed.
Modeling and Development of RMD Configuration Magnetic Bearing
K.P. Lijesh
2015-06-01
Full Text Available The low load carrying capacity of Passive Magnetic Bearings (PMBs has restricted their use in many industrial applications. The Rotation Magnetized Direction (RMD configuration has emerged as a strong and viable method that is able to substantially enhance the load carrying capacity of passive magnetic bearings. It consists of both radially and axially polarized passive magnets. But the physical realization of a radially polarized magnet is difficult to achieve. In the present work, a RMD structure consisting of aluminum ring and cubical shaped magnets is proposed by developing the radially polarized magnets required for RMD structure. A theoretical model is derived by simulating the cuboid magnets in form of sector magnets by developing equivalent surface area. An experimental setup was designed and developed to conduct experimental verification. The theoretical model is validated by conducting experiments on RMD configuration magnetic bearing and axially magnetized full ring bearing. The comparison of the load carrying capacity by different configuration is performed and results are presented.
Autosizing Control Panel for Needle Bearing
Prof.A.R.Wadhekar,; Ms Jyoti R. Rajput
2016-01-01
A needle roller bearing is a bearing which uses small cylindrical rollers. Bearings are used to reduce friction of any rotating surface. Needle bearings have a large surface in contact with the bearing outer surfaces as compared to ball bearings. There is less added clearance(Diameter of the shaft and the diameter of the bearing are different) so they are much compact. The structure consists of a needle cage which contains the needle rollersthemselves and an outer race (The housin...
Studying fluid squeeze characteristics for aerostatic journal bearing
Abdel-Rahman, Gamal M. [Department of Mathematics, Faculty of Science, Benha University, Benha 13518 (Egypt)], E-mail: gamalm60@yahoo.com
2008-07-01
The Reynolds equation for studying fluid squeeze of aerostatic journal bearing is solved numerically by considering the quasi-steady behavior of the air film. The radial displacement can influence the air film thickness modifying the pressure distribution in the journal-bearing gap. Also, the variations in the seal characteristics with eccentricity, time, squeeze number, length-to-diameter and supply pressure are presented. The numerical results for the squeeze load-carrying capacity are given in a non-dimensional for000.
Symmetric, coherent, Choquet capacities
Kadane, Joseph B.; Wasserman, Larry
1996-01-01
Choquet capacities are a generalization of probability measures that arise in robustness, decision theory and game theory. Many capacities that arise in robustness are symmetric or can be transformed into symmetric capacities. We characterize the extreme points of the set of upper distribution functions corresponding to coherent, symmetric Choquet capacities on [0, 1]. We also show that the set of 2-alternating capacities is a simplex and we give a Choquet representation of this set.
Journal bearings design for a novel revolving vane compressor
Tan, K.M.; Ooi, K.T. [Thermal and Fluids Division, School of Mechanical and Aerospace Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798 (Singapore)
2011-01-15
This paper presents the theoretical details of the journal bearing design for Revolving Vane (RV) rotary type compressor. The mathematical models, force analysis, and the theoretical design analysis for the dynamically loaded journal bearing of the compressor are presented. The variations of the minimum oil film thickness and the maximum film pressure developed are shown and the influences of design parameters, compressor configurations, and operating conditions on the journal bearing performance are described. For an air-conditioning compressor of 1.5 kW cooling capacity, the lowest minimum oil film thickness for lower and upper journal bearings is 6.6 {mu}m and 4.3 {mu}m respectively, when the cylinder is simply supported and the rotor is cantilever-supported. The lowest minimum oil film thickness for the journal bearing, which supports the cylinder, reduces to 4.0 {mu}m if the cantilever-type support is used. Besides that, a short-fat configuration of RV compressor is favorable in the interest of lowering bearing forces. (author)
Superconducting bearings for flywheel applications
Abrahamsen, A.B.
2001-01-01
A literature study on the application of superconducting bearings in energy storage flywheel systems. The physics of magnetic levitation and superconductors are presented in the first part of the report, followed by a discussion of the literature found onthe applications of superconducting bearings in flywheels.
Superconducting bearings for flywheel applications
Abrahamsen, A.B.
2001-01-01
A literature study on the application of superconducting bearings in energy storage flywheel systems. The physics of magnetic levitation and superconductors are presented in the first part of the report, followed by a discussion of the literature found onthe applications of superconducting bearings...
Jentink, F.A.
1898-01-01
The other day I read in a dutch popular periodical a paper dealing with the different species of Bears and their geographical distribution. To my great surprise the Malayan Bear was mentioned from Java: the locality Java being quite new to me I wrote to the author of that paper and asked him some in