Study on Seismic Behavior of Recycled Concrete Energy-efficient Homes Structure Wall

Directory of Open Access Journals (Sweden)

Dong Lan

2016-01-01

Full Text Available The main point is to study the seismic behavior of the lattice type recycled concrete energy saving wall under low-cyclic loading,to provide the basis for the seismic performance of application of recycled concrete lattice wall in energy-saving residential structure. Design two walls with the same structure measures, include Lattice type recycled concrete wall and natural concrete wall, they are tested under low-cycle repetitive loading, compared failure mode and seismic performance in different reinforcement conditions of side column. The bearing capacity and ductility of recycled aggregate concrete are better than natural aggregate concrete, The stiffness degradation curves and the skeleton curves of the walls are basically the same, both of them have better seismic energy dissipation capacity. Lattice type concrete wall is good at seismic performance, recycled aggregate concrete is good at plastic deformation ability, it is advantageous to seismic energy dissipation of wall, it can be applied in energy efficient residential structure wall.

Damage Detection In Laboratory Concrete Beams

DEFF Research Database (Denmark)

Brincker, Rune; Andersen, Palle; Kirkegaard, Poul Henning

1995-01-01

The aim of the investigation reported in this paper is to clarify to what extent damages in reinforced concrete can be detected by estimating changes in the vibrational properties. A series of damages were introduced by applying static load cycles of increasing magnitude to two concrete beams...

Damage Detection in Laboratory Concrete Beams

DEFF Research Database (Denmark)

Brincker, Rune; Andersen, P.; Kirkegaard, Poul Henning

The aim of the investigation reported in this paper is to clarify to what extent damages in reinforced concrete can be detected by estimating changes in the vibrational properties. A series of damages were introduced by applying static load cycles of increasing magnitude to two concrete beams...

FEM investigation of concrete silos damaged and reinforced externally with CFRP

Science.gov (United States)

Kermiche, Sihem; Boussaid, Ouzine; Redjel, Bachir; Amirat, Abdelaziz

2018-03-01

The present work investigates the reinforcement of concrete wheat-grain silos under initial damage. The reinforcement is achieved by mounting bands of carbon fiber reinforced polymer (CFRP) on the external walls of the silo. 4 modes of reinforcement are adapted according to the width of the band, the gap between two bands, the height of reinforcement and the number of layers achieved through banding. Analytical analyses were conducted using the Reimbert method and the Eurocode 1 Part 4 method, as well as numerically through the finite element software Abaqus. Results show that the normal pressure reaches a peak value when approaching the silo hopper. Initial damage in a concrete silo was first determined using a 3D geometrical model, while the damage analyses were conducted to optimize the CFRP reinforcement by mounting 2 CFRP bands close together above and below the cylinder-hopper joint. Increasing the number of banding layers could produce better performance as the damage was slightly decreased from 0.161 to 0.152 for 1 and 4 layers respectively.

Modeling damage in concrete pavements and bridges.

Science.gov (United States)

2010-09-01

This project focused on micromechanical modeling of damage in concrete under general, multi-axial loading. A : continuum-level, three-dimensional constitutive model based on micromechanics was developed. The model : accounts for damage in concrete by...

Spalling of concrete walls under blast load

International Nuclear Information System (INIS)

Kot, C.A.

1977-01-01

A common effect of the detonation of explosives in close proximity of concrete shield walls is the spalling (scabbing) of the back face of the wall. Spalling is caused by the free surface reflection of the shock wave induced in the wall by high pressure air blast and occurs whenever the dynamic tensile rupture strength is exceeded. While a complex process, reasonable analytical spall estimates can be obtained for brittle materials with low tensile strengths, such as concrete, by assuming elastic material behavior and instantaneous spall formation. Specifically, the spall thicknesses and velocities for both normal and oblique incidence of the shock wave on the back face of the wall are calculated. The complex exponential decay wave forms of the air blast are locally approximated by simple power law expressions. Variations of blast wave strength with distance to the wall, charge weight and angle of incidence are taken into consideration. The shock wave decay in the wall is also accounted for by assuming elastic wave propagation. For explosions close-in to the wall, where the reflected blast wave pressures are sufficiently high, multiple spall layers are formed. Successive spall layers are of increasing thickness, at the same time the spall velocities decrease. The spall predictions based on elastic theory are in overall agreement with experimntal results and provide a rapid means of estimating spalling trends of concrete walls subjected to air blast. (Auth.)

Experimental Study of Damage Evolution in Circular Stirrup-Confined Concrete.

Science.gov (United States)

Li, Zuohua; Peng, Zhihan; Teng, Jun; Wang, Ying

2016-04-08

This paper presents an experimental study on circular stirrup-confined concrete specimens under uniaxial and monotonic load. The effects of stirrup volume ratio, stirrup yield strength and concrete strength on damage evolution of stirrup-confined concrete were investigated. The experimental results showed that the strength and ductility of concrete are improved by appropriate arrangement of the stirrup confinement. Firstly, the concrete damage evolution can be relatively restrained with the increase of the stirrup volume ratio. Secondly, higher stirrup yield strength usually causes larger confining pressures and slower concrete damage evolution. In contrast, higher concrete strength leads to higher brittleness, which accelerates the concrete damage evolution. A plastic strain expression is obtained through curve fitting, and a damage evolution equation for circular stirrup-confined concrete is proposed by introducing a confinement factor ( C ) based on the experimental data. The comparison results demonstrate that the proposed damage evolution model can accurately describe the experimental results.

Experimental Study of Damage Evolution in Circular Stirrup-Confined Concrete

Science.gov (United States)

Li, Zuohua; Peng, Zhihan; Teng, Jun; Wang, Ying

2016-01-01

This paper presents an experimental study on circular stirrup-confined concrete specimens under uniaxial and monotonic load. The effects of stirrup volume ratio, stirrup yield strength and concrete strength on damage evolution of stirrup-confined concrete were investigated. The experimental results showed that the strength and ductility of concrete are improved by appropriate arrangement of the stirrup confinement. Firstly, the concrete damage evolution can be relatively restrained with the increase of the stirrup volume ratio. Secondly, higher stirrup yield strength usually causes larger confining pressures and slower concrete damage evolution. In contrast, higher concrete strength leads to higher brittleness, which accelerates the concrete damage evolution. A plastic strain expression is obtained through curve fitting, and a damage evolution equation for circular stirrup-confined concrete is proposed by introducing a confinement factor (C) based on the experimental data. The comparison results demonstrate that the proposed damage evolution model can accurately describe the experimental results. PMID:28773402

Effectiveness of Horizontal Rebar on Concrete Block Retaining Wall Strength

OpenAIRE

Krishpersad Manohar; Rikhi Ramkissoon

2016-01-01

The effectiveness of including a horizontal rebar compared to only a vertical rebar in concrete filled core interlocking concrete block retaining wall sections was investigated with respect to the horizontal retaining force. Experimental results for three specimens of interlocking blocks with vertical rebar and concrete filled cores showed an average horizontal retaining force of 24546 N ± 5.7% at an average wall deflection of 13.3 mm. Experimental results for three wall specimens of interloc...

Modeling of Corrosion-induced Concrete Damage

DEFF Research Database (Denmark)

Thybo, Anna Emilie A.; Michel, Alexander; Stang, Henrik

2013-01-01

In the present paper a finite element model is introduced to simulate corrosion-induced damage in concrete. The model takes into account the penetration of corrosion products into the concrete as well as non-uniform formation of corrosion products around the reinforcement. To ac-count for the non...... of corrosion products affects both the time-to cover cracking and the crack width at the concrete surface.......In the present paper a finite element model is introduced to simulate corrosion-induced damage in concrete. The model takes into account the penetration of corrosion products into the concrete as well as non-uniform formation of corrosion products around the reinforcement. To ac-count for the non......-uniform formation of corrosion products at the concrete/reinforcement interface, a deterministic approach is used. The model gives good estimates of both deformations in the con-crete/reinforcement interface and crack width when compared to experimental data. Further, it is shown that non-uniform deposition...

Dismantling system of concrete thermal shielding walls

International Nuclear Information System (INIS)

Machida, Nobuhiro; Saiki, Yoshikuni; Ono, Yorimasa; Tokioka, Masatake; Ogino, Nobuyuki.

1985-01-01

Purpose: To enable safety and efficient dismantling of concrete thermal shielding walls in nuclear reactors. Method: Concrete thermal shielding walls are cut and dismantled into dismantled blocks by a plasma cutting tool while sealing the top opening of bioshielding structures. The dismantled blocks are gripped and conveyed. The cutting tool is remote-handled while monitoring on a television receiver. Slugs and dusts produced by cutting are removed to recover. Since the dismantling work is carried out while sealing the working circumstance and by the remote control of the cutting tool, the operators' safety can be secured. Further, since the thermal sealing walls are cut and dismantled into blocks, dismantling work can be done efficiently. (Moriyama, K.)

Seismic Behaviour of Composite Steel Fibre Reinforced Concrete Shear Walls

Science.gov (United States)

Boita, Ioana-Emanuela; Dan, Daniel; Stoian, Valeriu

2017-10-01

In this paper is presented an experimental study conducted at the “Politehnica” University of Timisoara, Romania. This study provides results from a comprehensive experimental investigation on the behaviour of composite steel fibre reinforced concrete shear walls (CSFRCW) with partially or totally encased profiles. Two experimental composite steel fibre reinforced concrete walls (CSFRCW) and, as a reference specimen, a typical reinforced concrete shear wall (RCW), (without structural reinforcement), were fabricated and tested under constant vertical load and quasi-static reversed cyclic lateral loads, in displacement control. The tests were performed until failure. The tested specimens were designed as 1:3 scale steel-concrete composite elements, representing a three storeys and one bay element from the base of a lateral resisting system made by shear walls. Configuration/arrangement of steel profiles in cross section were varied within the specimens. The main objective of this research consisted in identifying innovative solutions for composite steel-concrete shear walls with enhanced performance, as steel fibre reinforced concrete which was used in order to replace traditional reinforced concrete. A first conclusion was that replacing traditional reinforcement with steel fibre changes the failure mode of the elements, as from a flexural mode, in case of element RCW, to a shear failure mode for CSFRCW. The maximum lateral force had almost similar values but test results indicated an improvement in cracking response, and a decrease in ductility. The addition of steel fibres in the concrete mixture can lead to an increase of the initial cracking force, and can change the sudden opening of a crack in a more stable process.

The Backscattering of Gamma Radiation from Spherical Concrete Walls

Energy Technology Data Exchange (ETDEWEB)

Leimdoerfer, M

1962-12-15

The Monte Carlo technique has been applied to investigate the effect of wall curvature on the backscattering properties of concrete. The wall was considered infinitely thick and the source radiation was normally incident. Monte Carlo calculations were only performed at 1 MeV source energy but an analytical formula was derived to facilitate extrapolations to other energies as well as materials. The results show that for practical purposes the plane wall albedo is a sufficient, and conservative, approximation, 90 % of its value being reached at a concrete wall radius of about 100 cm for source energies up to 10 MeV.

Breakwaters with Vertical and Inclined Concrete Walls

DEFF Research Database (Denmark)

Burcharth, Hans Falk

Following the PIANC PTC II working group on Analyses of Rubble Mound Breakwaters it was, in 1991, decided to form Working Group (WG) n° 28 on "Breakwaters with vertical and inclined concrete walls" The scope of the work was to achieve a better understanding of the overall safety aspects in the de......Following the PIANC PTC II working group on Analyses of Rubble Mound Breakwaters it was, in 1991, decided to form Working Group (WG) n° 28 on "Breakwaters with vertical and inclined concrete walls" The scope of the work was to achieve a better understanding of the overall safety aspects...

Evaluation and rehabilitation of corrosion damaged reinforced concrete structures

International Nuclear Information System (INIS)

Paul, I.S.

1999-01-01

For the last two decades, rehabilitation of corrosion damaged concrete structures has been one of the most important challenges faced by the construction industry throughout the world. The extent of the damage is significant in cold climates and also in hot and humid climates. In both cases, the corrosion is invariably initiated by ingress of salts into the concrete either from de-icing salts used on roads, or from salt-laden air, soils or ground water. However, there is a contrast in sites of distress in the two climatic regions mentioned above. In cold climates, where de-icing salts are used, the damage is generally to superstructures and is therefore visible, but in hot, humid coastal regions damage is primarily in the substructures and may not be so clearly apparent. This paper presents the corrosion mechanism in concrete deterioration, the methods of evaluation of the damaged structures, and rehabilitation strategies. A case history of a concrete rehabilitation project is included together with some lessons learned in rehabilitation of corrosion damaged structures. Recommendations are made for maintenance of concrete structures and a warning is issued that salt run-off from roads in cold climates may cause distress in below ground concrete structures, similar to structures in hot and humid climates with saline groundwater and soils. (author)

Injection technologies for the repair of damaged concrete structures

CERN Document Server

Panasyuk, V V; Sylovanyuk, V P

2014-01-01

This book analyzes the most important achievements in science and engineering practice concerning operational factors that cause damage to concrete and reinforced concrete structures. It includes methods for assessing their strength and service life, especially those that are based on modern concepts of the fracture mechanics of materials. It also includes basic approaches to the prediction of the remaining service life for long-term operational structures. Much attention is paid to injection technologies for restoring the serviceability of damaged concrete and reinforced concrete structures. In particular, technologies for remedying holes, cracks, corrosion damages etc. The books contains sample cases in which the above technologies have been used to restore structural integrity and extend the reliable service life of concrete and reinforced concrete constructions, especially NPPs, underground railways, bridges, seaports and historical relics.

Revision of Sustainable Criteria of Concrete Walls for Earthquake-Resistant Housing

Directory of Open Access Journals (Sweden)

Alcocer S.M.

2012-10-01

Full Text Available The seismic performance of low-rise housing has been noticeably inadequate during the most recent earthquakes occurred in Latin American countries. Moreover, the literature review revealed that some traditional techniques do not contribute to building sustainable housing. In the last decade, construction of concrete walls housing has become a preferred choice because of the speed of construction and availability of materials in most of these countries. Aimed at improving seismic design methods for this type of construction, an extensive analytical and experimental program was carried out. The experimental program included quasi-static and shaking-table tests of 47 walls with different height-to-length ratios and walls with openings. Variables studied were type of concrete, web steel ratio and type of web reinforcement. The paper presents and discusses the main results of the research program and evaluates the technical and environmental feasibility for using concrete walls for sustainable and earthquake-resistant housing. Performance of concrete walls housing is assessed in terms of key environmental and earthquake-resistant requirements. It was found that concrete wall housing is not only safe under earthquakes and easily adaptable to climate, but also it stimulates environmental conservation and promotes reducing the costs of construction, operation and maintenance.

Experimental, numerical, and analytical studies on the seismic response of steel-plate concrete (SC) composite shear walls

Science.gov (United States)

Epackachi, Siamak

The seismic performance of rectangular steel-plate concrete (SC) composite shear walls is assessed for application to buildings and mission-critical infrastructure. The SC walls considered in this study were composed of two steel faceplates and infill concrete. The steel faceplates were connected together and to the infill concrete using tie rods and headed studs, respectively. The research focused on the in-plane behavior of flexure- and flexure-shear-critical SC walls. An experimental program was executed in the NEES laboratory at the University at Buffalo and was followed by numerical and analytical studies. In the experimental program, four large-size specimens were tested under displacement-controlled cyclic loading. The design variables considered in the testing program included wall thickness, reinforcement ratio, and slenderness ratio. The aspect ratio (height-to-length) of the four walls was 1.0. Each SC wall was installed on top of a re-usable foundation block. A bolted baseplate to RC foundation connection was used for all four walls. The walls were identified to be flexure- and flexure-shear critical. The progression of damage in the four walls was identical, namely, cracking and crushing of the infill concrete at the toes of the walls, outward buckling and yielding of the steel faceplates near the base of the wall, and tearing of the faceplates at their junctions with the baseplate. A robust finite element model was developed in LS-DYNA for nonlinear cyclic analysis of the flexure- and flexure-shear-critical SC walls. The DYNA model was validated using the results of the cyclic tests of the four SC walls. The validated and benchmarked models were then used to conduct a parametric study, which investigated the effects of wall aspect ratio, reinforcement ratio, wall thickness, and uniaxial concrete compressive strength on the in-plane response of SC walls. Simplified analytical models, suitable for preliminary analysis and design of SC walls, were

Analysis of prestressed concrete wall segments

International Nuclear Information System (INIS)

Koziak, B.D.P.; Murray, D.W.

1979-06-01

An iterative numerical technique for analysing the biaxial response of reinforced and prestressed concrete wall segments subject to combinations of prestressing, creep, temperature and live loads is presented. Two concrete constitutive relations are available for this analysis. The first is a uniaxially bilinear model with a tension cut-off. The second is a nonlinear biaxial relation incorporating equivalent uniaxial strains to remove the Poissons's ratio effect under biaxial loading. Predictions from both the bilinear and nonlinear model are compared with observations from experimental wall segments tested in tension. The nonlinear model results are shown to be close to those of the test segments, while the bilinear results are good up to cracking. Further comparisons are made between the nonlinear analysis using constant membrane force-moment ratios, constant membrane force-curvature ratios, and a nonlinear finite difference analysis of a test containment structure. Neither nonlinear analysis could predict the reponse of every wall segment within the structure, but the constant membrane force-moment analysis provided lower bound results. (author)

Concrete Flow in Diaphragm Wall Panels : A Full-Scale In-Situ Test

NARCIS (Netherlands)

Van Dalen, J.H.; Bosch, J.W.; Broere, W.

2015-01-01

Flow processes, taking place during the concreting of diaphragm wall panels (D-wall panels), are of great importance for the quality of the wall. During this phase, the bentonite, present in the excavated trench, should be completely replaced by concrete in a controlled way. In literature several

Local Impact Simulation of SC Wall Structures using Aircraft Engine Projectile

International Nuclear Information System (INIS)

Chung, Chulhun; Lee, Jungwhee; Lee, Hanjoo; Jung, Raeyoung; Hyun, Changhun

2013-01-01

SC wall structure developed for nuclear power plant buildings consists of plain concrete and two steel plates on both surface of the concrete, while RC structure consists of re bar and concrete. SC structure has higher scabbing resistance than RC structure due to the action of steel plate on the rear side of impact. Therefore SC structure is known as more effective structure from the viewpoint of aircraft crash than RC structure. However, most of the recent researches and experiments about local impact damage deal with RC structures, and the effect of re bar and steel plate is not considered reasonably. Although Walter et al. and Make-work et al. suggested a formula for evaluating perforation depth of steel plate covered RC walls, most of the previous researches about SC structure are focused on perforation and scabbing due to the impact of hard projectile, rather than soft projectile such as an aircraft. In this research a soft projectile, i. e. aircraft engine, is utilized for impact simulation of RC and SC walls. To evaluate local damage of SC wall structures, parametric study with the variables of wall thickness and steel ratio of the cover plate is performed, and the results are compared with those of RC structures. Since scabbing was prevented by the steel plates, penetration mode of damage was observed in SC walls while scabbing damage was occurred in RC walls. It is confirmed that the rear steel plate not only contains concrete debris, but also reduces the internal damage of the concrete walls. Penetration depth of SC walls did not largely vary due to the increasing steel ratio, and similar results to RC walls were observed when the wall thickness is larger than a certain value since the impact resistance of SC wall is mainly governed by the thickness of concrete part. Therefore, it is expected that similar level of impact resistance to RC structure can be produced with the minimum thickness of steel plates of SC structure. According to these results, SC

The assessment of bond strength between heat damaged concrete and high strength fibre reinforced concrete

Science.gov (United States)

Zahid, M. Z. A. Mohd; Muhamad, K.

2017-09-01

The aim of this study is to assess the bond strength between heat damaged concrete and high strength fibre reinforced concrete (HPFRC). Firstly, this paper presents the various steps taken to prepare the HPFRC with self-compacting property. The minimum targeted slump flow is 600 mm and minimum targeted compressive strength is 80 MPa. The key mix variables considered are such as type of superplasticizer, water cement ratio and silica fume content. Then, the bond strength between the heat damaged concrete with HPFRC was examined. The experimental parameters are heating temperature, surface treatment technique and curing method and the results show that, all experimental parameters are significantly affected the bond strength between heat damaged concrete and HPFRC.

Soft impact testing of a wall-floor-wall reinforced concrete structure

Energy Technology Data Exchange (ETDEWEB)

Vepsä, Ari, E-mail: ari.vepsa@vtt.fi; Calonius, Kim; Saarenheimo, Arja; Aatola, Seppo; Halonen, Matti

2017-01-15

Highlights: • A wall-floor-wall reinforced concrete structure was built. • The structure was subjected to three almost identical soft impact tests. • Response was measured with accelerometers, displacement sensors and strain gauges. • Modal tests was also carried out with the same structure in different conditions. • The results are meant to be used for validation of computational methods and models. - Abstract: Assessing the safety of the reactor building of a nuclear power plant against the crash of an airplane calls for valid computational tools such as finite element models and material constitutive models. Validation of such tools and models in turn calls for reliable and relevant experimental data. The problem is that such data is scarcely available. One of the aspects of such a crash is vibrations that are generated by the impact. These vibrations tend to propagate from the impact point to the internal parts of the building. If strong enough, these vibrations may cause malfunction of the safety-critical equipment inside the building. To enable validation of computational models for this type of behaviour, we have conducted a series of three tests with a wall-floor-wall reinforced concrete structure under soft impact loading. The response of the structure was measured with accelerometers, displacement sensors and strain gauges. In addition to impact tests, the structure was subjected to modal tests under different conditions. The tests yielded a wealth of useful data for validation of computational models and better understanding about shock induced vibration physics especially in reinforced concrete structures.

Experimental study on the leakage of gas through cracked concrete walls

International Nuclear Information System (INIS)

Suzuki, T.; Takiguchi, K.; Hotta, H.; Kojima, N.; Fukuhara, M.; Kimura, K.

1989-01-01

The air-tightness of concrete walls is important for nuclear-related facilities. A concrete wall has very high probabilities of developing cracks due to shrinkage, seismic forces or other factors. It is therefore essential to be able to predict the amount of gas which will leak through a cracked concrete wall. In the previous paper published in SmiRT-9, the experimental equation on the gas leakage through a single crack occurred in concrete was presented based on two-dimensional Poiseuille's flow. In this paper, the experimental results were examined again considering the compressibility of gas, and new equation is presented. The experiments which were similar to ones in the previous paper were carried out on several kinds of concrete using several kinds of gases, and the effects of the kinds of gaseous body, particle size of aggregates and shape of aggregates were examined

Construction of concrete hot cells; requirements for shielding windows for concrete walls with different densities

International Nuclear Information System (INIS)

1987-10-01

The shielding windows form part of the basic equipment of hot cells for remote handling, as defined in standard DIN 25 420 part 1. The draft standard in hand is intended to specify the design and manufacture requirements, especially with regard to main dimensions, sight quality, shielding effects, and radiation resistance. The standard refers to three types of shielding window with surface area design (product of density and wall thickness) corresponding to concrete walls of the densities 2.4, 3.4, and 4.0 g/cm 3 . The windows fit to three types of concrete of common usage, and the design is made for Co-60 radiation, with attenuation factors of about 10 4 , 10 6 , or 10 7 . For concrete walls with densities between these data, a shielding window suitable to the next higher density data is to be chosen. (orig./HP) [de

Simulation of reinforced concrete short shear wall subjected to cyclic loading

International Nuclear Information System (INIS)

Parulekar, Y.M.; Reddy, G.R.; Vaze, K.K.; Pegon, P.; Wenzel, H.

2014-01-01

Highlights: • Prediction of the capacity of squat shear wall using tests and analysis. • Modification of model of concrete in the softening part. • Pushover analysis using softened truss theory and FE analysis is performed. • Modified concrete model gives reasonable accurate peak load and displacement. • The ductility, ultimate load and also crack pattern can be accurately predicted. - Abstract: This paper addresses the strength and deformation capacity of stiff squat shear wall subjected to monotonic and pseudo-static cyclic loading using experiments and analysis. Reinforced concrete squat shear walls offer great potential for lateral load resistance and the failure mode of these shear walls is brittle shear mode. Shear strength of these shear walls depend strongly on softening of concrete struts in principal compression direction due to principal tension in other direction. In this work simulation of the behavior of a squat shear wall is accurately predicted by finite element modeling by incorporating the appropriate softening model in the program. Modification of model of concrete in the softening part is suggested and reduction factor given by Vecchio et al. (1994) is used in the model. The accuracy of modeling is confirmed by comparing the simulated response with experimental one. The crack pattern generated from the 3D model is compared with that obtained from experiments. The load deflection for monotonic loads is also obtained using softened truss theory and compared with experimental one

Thermal Insulating Concrete Wall Panel Design for Sustainable Built Environment

Science.gov (United States)

Zhou, Ao; Wong, Kwun-Wah

2014-01-01

Air-conditioning system plays a significant role in providing users a thermally comfortable indoor environment, which is a necessity in modern buildings. In order to save the vast energy consumed by air-conditioning system, the building envelopes in envelope-load dominated buildings should be well designed such that the unwanted heat gain and loss with environment can be minimized. In this paper, a new design of concrete wall panel that enhances thermal insulation of buildings by adding a gypsum layer inside concrete is presented. Experiments have been conducted for monitoring the temperature variation in both proposed sandwich wall panel and conventional concrete wall panel under a heat radiation source. For further understanding the thermal effect of such sandwich wall panel design from building scale, two three-story building models adopting different wall panel designs are constructed for evaluating the temperature distribution of entire buildings using finite element method. Both the experimental and simulation results have shown that the gypsum layer improves the thermal insulation performance by retarding the heat transfer across the building envelopes. PMID:25177718

Acoustic emission diagnosis of concrete-piles damaged by earthquakes

International Nuclear Information System (INIS)

Shiotami, Tomoki; Sakaino, Norio; Ohtsu, Masayasu; Shigeishi, Mitsuhiro

1997-01-01

Earthquakes often impose unexpected damage on structures. Concerning the soundness of the structure, the upper portion is easily estimated by visual observation, while the lower portion located in deep underground is difficult to be estimated. Thus there exist few effective methods to investigate underground structures. In this paper, a new inspection technique for damage evaluation of concrete-piles utilizing acoustic emission (AE) is proposed, and is verified by a series of experiments. Firstly, such basic characteristics as the attenuation and effective wave-guides for detecting AE underground, are examined through laboratory tests. Secondary, fracture tests of full-scale prefabricated concrete piles are conducted, and the characteristics of the AE are examined. Finally, actual concrete-piles attacked by the 1995 Great Hanshin Earthquake are investigated. Results confirm that the estimated damages by the proposed method are in good agreement with actual damaged locations. Thus, the method is very effective for the diagnosis of the concrete-piles.

The Shrinkage Cracking Behavior in Reinforced Reactive Powder Concrete Walls

Directory of Open Access Journals (Sweden)

Samir A. Al-Mashhadi

2017-07-01

Full Text Available In this study, the reduced scale wall models were used (they are believed to resemble as much as possible the field conditions to study the shrinkage behavior of reactive powder concrete (RPC base restrained walls. Six base restrained RPC walls were casted in different length/height ratios of two ratios of steel fiber by volume in Summer. These walls were restrained by reinforced concrete bases to provide the continuous base restraint to the walls. The mechanical properties of reactive powder concrete investigated were; compressive strength between (75.3 – 140.1 MPa, splitting tensile strength between (5.7 – 13.9 MPa, flexural tensile strength (7.7 – 24.5 MPa, and static modulus of elasticity (32.7 – 47.1GPa. Based on the observations of this work, it was found that the cracks did not develop in the reduced scale of the reactive powder concrete (RPC walls restrained from movement at their bases for different L/H ratios (2, 5, and 10 and for two ratio of steel fiber (1% & 2% during 90 days period of drying conditions. Moreover, the shrinkage values increase toward the edges. Based on the results of this work, the increase in the maximum shrinkage values of walls with 1% steel fiber were (29%, 28%, 28% of the maximum shrinkage values of walls with 2% steel fiber of length/height ratios of (2, 5, and 10 respectively. The experimental observation in beam specimens showed that the free shrinkage, tensile strain capacity and elastic tensile strain capacity (at date of cracking of beams with 1% steel fiber were higher than the beams with 2% steel fiber by about (24%, (45% and (42% respectively

Frost damage of concrete subject to confinement

DEFF Research Database (Denmark)

Hasholt, Marianne Tange

2016-01-01

When internal frost damage is observed in real concrete structures, the usual pattern is cracks with a preferred orientation parallel to the exposed surface. When exposing concrete with poor frost resistance to a standardised freeze/thaw test in the laboratory, the orientations of the resulting...

Seismic behavior of reinforced concrete shear walls

International Nuclear Information System (INIS)

Wang, F.; Gantenbein, F.

1989-01-01

Reinforced concrete shear walls have an important contribution to building stiffness. So, it is necessary to know their behavior under seismic loads. The ultimate behavior study of shear walls subjected to dynamic loadings includes: - a description of the nonlinear global model based on cyclic static tests, - nonlinear time history calculations for various forcing functions. The comparison of linear and nonlinear results shows important margins related to the ductility when the bandwidth of the forcing function is narrow and centred on the wall natural frequency

Analytical Study on the Beyond Design Seismic Capacity of Reinforced Concrete Shear Walls

Energy Technology Data Exchange (ETDEWEB)

Nugroho, Tino Sawaldi Adi [Korea Advanced Institute of Science and Technology, Daejeon (Korea, Republic of); Chi, Ho-Seok [Korea Institute of Nuclear Safety, Daejeon (Korea, Republic of)

2015-10-15

The OECD-NEA has organized an international benchmarking program to better understand this critical issue. The benchmark program provides test specimen geometry, test setup, material properties, loading conditions, recorded measures, and observations of the test specimens. The main objective of this research is to assess the beyond design seismic capacity of the reinforced concrete shear walls tested at the European Laboratory for Structural Assessment between 1997 and 1998 through participation in the OECD-NEA benchmark program. In this study, assessing the beyond design seismic capacity of reinforced concrete shear walls is performed analytically by comparing numerical results with experimental results. The seismic shear capacity of the reinforced concrete shear wall was predicted reasonably well using ABAQUS program. However, the proper calibration of the concrete material model was necessary for better prediction of the behavior of the reinforced concrete shear walls since the response was influenced significantly by the material constitutive model.

Diurnal thermal analysis of microencapsulated PCM-concrete composite walls

International Nuclear Information System (INIS)

Thiele, Alexander M.; Sant, Gaurav; Pilon, Laurent

2015-01-01

Highlights: • Transient heat conduction across microencapsulated PCM-concrete walls was simulated. • Equivalent homogeneous wall with effective thermal properties was rigorously derived. • Adding PCM to the wall increases daily energy savings and delays peak thermal load. • Energy savings is maximum when PCM melting temperature equals indoor temperature. • Energy savings are limited in extreme climates but time delay can be large. - Abstract: This paper examines the benefits of adding microencapsulated phase change material (PCM) to concrete used in building envelopes to reduce energy consumption and costs. First, it establishes that the time-dependent thermal behavior of microencapsulated PCM-concrete composite walls can be accurately predicted by an equivalent homogeneous wall with appropriate effective thermal properties. The results demonstrate that adding microencapsulated PCM to concrete resulted in a reduction and a time-shift in the maximum heat flux through the composite wall subjected to diurnal sinusoidal outdoor temperature and solar radiation heat flux. The effects of the PCM volume fraction, latent heat of fusion, phase change temperature and temperature window, and outdoor temperature were evaluated. Several design rules were established including (i) increasing the PCM volume fraction and/or enthalpy of phase change increased the energy flux reduction and the time delay, (ii) the energy flux reduction was maximized when the PCM phase change temperature was close to the desired indoor temperature, (iii) the optimum phase change temperature to maximize the time delay increased with increasing average outdoor temperature, (iv) in extremely hot or cold climates, the thermal load could be delayed even though the reduction in daily energy flux was small, and (v) the choice of phase change temperature window had little effect on the energy flux reduction and on the time delay. This analysis can serve as a framework to design PCM composite walls

Experimental determination of damping factors for walls of masonry and reinforced concrete

International Nuclear Information System (INIS)

Buttman, P.

1983-01-01

'Damping' is a fundamental parameter for the determination of the internal force with a given acceleration response spectrum when designing and dimensioning masonry and reinforced concrete walls for the loading case earthquake. The actual dampings of masonry and reinforced concrete walls are determined on a scale of 1:1 by means of a horizontal excitation at a chosen test setup. The test specimen have the dimensions b/h/d=100/200/11,5 cm and 24 cm. The horizontal and sinusoidal excitation of the test specimen is effected by a dynamic oscillating excitation with a maximum power of 20 kN. The evaluation of the measurements shows that the assumed damping values of 4% for the operating basis earthquake are realistic. In case of amplitudes corresponding to the loadings of the safe shutdown earthquake, however, dampings of 11% for reinforced concrete walls and of 24% for masonry walls were determined. This real damping behavior of reinforced concrete and masonry walls was documented by means of measurements, films and pictures. (orig.)

Seismic fragility of RC shear walls in nuclear power plant Part 1: Characterization of uncertainty in concrete constitutive model

International Nuclear Information System (INIS)

Syed, Sammiuddin; Gupta, Abhinav

2015-01-01

Highlights: • A framework is proposed for seismic fragility assessment of Reinforced Concrete structures. • Experimentally validated finite element models are used to conduct nonlinear simulations. • Critical parameters in concrete constitutive model are identified to conduct nonlinear simulations. • Uncertainties in model parameters of concrete damage plasticity model is characterized. • Closed form expressions are used to compute the damage variables and plasticity. - Abstract: This two part manuscript proposes a framework for seismic fragility assessment of reinforced concrete structures in nuclear energy facilities. The novelty of the proposed approach lies in the characterization of uncertainties in the parameters of the material constitutive model. Concrete constitutive models that comprehensively address different damage states such as tensile cracking, compression failure, stiffness degradation, and recovery of degraded stiffness due to closing of previously formed cracks under dynamic loading are generally defined in terms of a large number of variables to characterize the plasticity and damage at material level. Over the past several years, many different studies have been presented on evaluation of fragility for reinforced concrete structures using nonlinear time history simulations. However, almost all of these studies do not consider uncertainties in the parameters of a comprehensive constitutive model. Part-I of this two-part manuscript presents a study that is used to identify uncertainties associated with the critical parameters in nonlinear concrete damage plasticity model proposed by Lubliner et al. (1989. Int. J. Solids Struct., 25(3), 299) and later modified by Lee and Fenves (1998a. J. Eng. Mech., ASCE, 124(8), 892) and Lee and Fenves (1998b. Earthquake Eng. Struct. Dyn., 27(9), 937) for the purpose of seismic fragility assessment. The limitations in implementation of the damage plasticity model within a finite element framework and

Seismic fragility of RC shear walls in nuclear power plant Part 1: Characterization of uncertainty in concrete constitutive model

Energy Technology Data Exchange (ETDEWEB)

Syed, Sammiuddin [Department of Civil, Construction, and Environmental Engineering, North Carolina State University, 426 Mann Hall, Campus Box 7908, Raleigh, NC 27695-7908 (United States); Gupta, Abhinav, E-mail: agupta1@ncsu.edu [Department of Civil, Construction, and Environmental Engineering, North Carolina State University, 413 Mann Hall, Campus Box 7908, Raleigh, NC 27695-7908 (United States)

2015-12-15

Highlights: • A framework is proposed for seismic fragility assessment of Reinforced Concrete structures. • Experimentally validated finite element models are used to conduct nonlinear simulations. • Critical parameters in concrete constitutive model are identified to conduct nonlinear simulations. • Uncertainties in model parameters of concrete damage plasticity model is characterized. • Closed form expressions are used to compute the damage variables and plasticity. - Abstract: This two part manuscript proposes a framework for seismic fragility assessment of reinforced concrete structures in nuclear energy facilities. The novelty of the proposed approach lies in the characterization of uncertainties in the parameters of the material constitutive model. Concrete constitutive models that comprehensively address different damage states such as tensile cracking, compression failure, stiffness degradation, and recovery of degraded stiffness due to closing of previously formed cracks under dynamic loading are generally defined in terms of a large number of variables to characterize the plasticity and damage at material level. Over the past several years, many different studies have been presented on evaluation of fragility for reinforced concrete structures using nonlinear time history simulations. However, almost all of these studies do not consider uncertainties in the parameters of a comprehensive constitutive model. Part-I of this two-part manuscript presents a study that is used to identify uncertainties associated with the critical parameters in nonlinear concrete damage plasticity model proposed by Lubliner et al. (1989. Int. J. Solids Struct., 25(3), 299) and later modified by Lee and Fenves (1998a. J. Eng. Mech., ASCE, 124(8), 892) and Lee and Fenves (1998b. Earthquake Eng. Struct. Dyn., 27(9), 937) for the purpose of seismic fragility assessment. The limitations in implementation of the damage plasticity model within a finite element framework and

Concrete damage diagnosed using the non-classical nonlinear acoustic method

International Nuclear Information System (INIS)

Dao, Zhou; Xiao-Zhou, Liu; Xiu-Fen, Gong; E, Nazarov V; Li, Ma

2009-01-01

It is known that the strength of concrete is seriously affected by damage and cracking. In this paper, six concrete samples under different damage levels are studied. The experimental results show a linear dependence of the resonance frequency shift on strain amplitude at the fundamental frequency, and approximate quadratic dependence of the amplitudes of the second and third harmonics on strain amplitude at the fundamental frequency as well. In addition, the amplitude of the third harmonics is shown to increase with the increase of damage level, which is even higher than that of the second harmonics in samples with higher damage levels. These are three properties of non-classical nonlinear acoustics. The nonlinear parameters increase from 10 6 to 10 8 with damage level, and are more sensitive to the damage level of the concrete than the linear parameters obtained by using traditional acoustics methods. So, this method based on non-classical nonlinear acoustics may provide a better means of non-destructive testing (NDT) of concrete and other porous materials

Non-Destructive Detection of Rebar Buried in a Reinforced Concrete Wall with Wireless Passive SAW Sensor

Science.gov (United States)

Fan, Yanping; Ji, Xiaojun; Cai, Ping; Lu, Qianhui

2013-01-01

In order to reduce the damage to the old reinforced concrete walls and work out the best construction scheme during the renovation of old buildings, it is often required to detect the position of rebar buried in concrete walls. In this paper, we propose a non-destructive method to detect the buried rebar by self-inductive sensor combined with surface acoustic wave resonator (SAWR). The proposed method has the advantages of wireless, passive and convenient operations. In our new design, the sensing element of self-inductance coil was made as a component of SAWR matching network. The distribution of rebar could be measured according to the system resonant frequency, using a signal demodulation device set. The depth of buried rebar and the deviation of output resonant frequency from inherent frequency of SAWR have an inverse relation. Finally, the validity of the method was verified in theoretical calculation and simulation.

Evaluation of Tritium Behavior in the Epoxy Painted Concrete Wall of ITER Hot Cell

International Nuclear Information System (INIS)

Nakamura, Hirofumi; Hayashi, Takumi; Kobayashi, Kazuhiro; Nishi, Masataka

2005-01-01

Tritium behavior released in the ITER hot cell has been investigated numerically using a combined analytical methods of a tritium transport analysis in the multi-layer wall (concrete and epoxy paint) with the one dimensional diffusion model and a tritium concentration analysis in the hot cell with the complete mixing model by the ventilation. As the results, it is revealed that tritium concentration decay and permeation issues are not serious problem in a viewpoint of safety, since it is expected that tritium concentration in the hot cell decrease rapidly within several days just after removing the tritium release source, and tritium permeation through the epoxy painted concrete wall will be negligible as long as the averaged realistic diffusion coefficient is ensured in the concrete wall. It is also revealed that the epoxy paint on the concrete wall prevents the tritium inventory increase in the concrete wall greatly (two orders of magnitudes), but still, the inventory in the wall is estimated to reach about 0.1 PBq for 20 years operation

Experimental report of precast prestressed concrete shear wall. Precast prestressed concrete taishinheki no jikken hokoku

Energy Technology Data Exchange (ETDEWEB)

Takada, K.; Komura, M.; Sakata, H.; Senoo, M. (Fudo Building Research Co. Ltd., Tokyo (Japan))

1993-07-30

The present report outlines the multi-story precast prestressed concrete earthquake-proof wall (PC shear wall system). The PC shear wall is a precast wall which internally contains the columns and beams as a unit. Therefore, the present system integrates the walls, columns and beams without beam-framing installation for the intermediate stories. It can simplify the concreting in site and ease the construction of building. For the system development, experiment was made on the deformation, sliding, yield strength and destruction state of the shear wall. Used were four types of test unit which are different in both reinforcement and connection methods. The test force was given by a hydraulically drawing jack. In the experiment, the four types were compared in destruction state, relation between load and deformation, yield strength, and strain of main column reinforcing bars and wall connection reinforcing bars. PC shear wall system-based design was studied from the experimental result. The shear wall in which there occurred both bending and shearing deformations was modeled by changing to a brace unit. Divided into bending deformation and shearing deformation, the deformation was calculated, which concluded that the shearing deformation dominates in the present system. 15 figs., 4 tabs.

Experimental and numerical investigations of higher mode effects on seismic inelastic response of reinforced concrete shear walls

Science.gov (United States)

Ghorbanirenani, Iman

) methods using the shake table feedback signals as input. Good agreement was generally obtained between numerical and experimental results. Both computer programs were able to predict the natural frequency of the walls in the undamaged and damaged conditions. Both modeling techniques could predict that the maximum bending moment at the base of the walls reached the actual wall moment capacity. The inelastic response and the dual plastic hinge behaviour of the walls could be adequately reproduced using the fibre element and finite element analysis programs. The fibre element method is a good alternative in terms of computing time. It produces reasonable results in comparison with the finite element method, although particular attention needs to be given to the selection of the damping ratios. The different parametric analyses performed in this thesis showed that, for both models, adding a small amount of global viscous damping in combination with a refined reinforced concrete hysteretic model could predict better the seismic behaviour of the tested structures. For the VecTor2 program, a viscous damping of 1% led to reasonable results for the studied RC walls. For the OpenSees program, 2% damping resulted in a good match between test and predictions for the 100% EQ test on the initially undamaged wall. When increasing the earthquake intensities, the damping had to be reduced between 1.5% and 1% to achieve good results for a damaged wall with elongated vibration periods. According to the experimental results and numerical analyses on reinforced concrete shear walls subjected to ground motions from Eastern North America earthquakes, there is a high possibility of having a second plastic hinge forming in the upper part of walls in addition to the one assumed in design at the base. This second hinge could dissipate the earthquake energy more effectively and decrease the force demand on the wall. A dual plastic hinge design approach in which the structures become plastic in the

Research Status on Bonding Behavior of Prefabricated Concrete Shear Wall

Science.gov (United States)

Wang, Donghui; Liu, Xudong; Wang, Sheng; Li, Shanshan

2018-03-01

Prefabricated shear wall structure adapts to the development and requirements of China’s residential industrialization. The key to the prefabricated concrete shear wall structure is the connection between the prefabricated members, where the reliability of the connection of the concrete joint is related to the overall performance and seismic effect of the structure. In this paper, the microstructures of the joint surface and shear properties are analysed, and the formula for calculating the shear strength of the joint is obtained.

Shield design of concrete wall between decay tank room and primary pump room in TRIGA facility

International Nuclear Information System (INIS)

Khan, M. J. H.; Rahman, M.; Haque, A.; Zulquarnain, A.; Ahmed, F. U.; Bhuiyan, S. I.

2007-01-01

The objective of this study is to recommend the radiation protection design parameters from the shielding point of view for concrete wall between the decay tank room and the primary pump room in TRIGA Mark-II research reactor facility. The shield design for this concrete wall has been performed with the help of Point-kernel Shielding Code Micro-Shield 5.05 and this design was also validated based on the measured dose rate values with Radiation Survey Meter (G-M Counter) considering the ICRP-60 (1990) recommendations for occupational dose rate limit (10 μSv/hr). The recommended shield design parameters are: (i) thickness of 114.3 cm Ilmenite-Magnetite Concrete (IMC) or 129.54 cm Ordinary Reinforced Concrete (ORC) for concrete wall A (ii) thickness of 66.04 cm Ilmenite-Magnetite Concrete (IMC) or 78.74 cm Ordinary Reinforced Concrete (ORC) for concrete wall B and (iii) door thickness of 3.175 cm Mild Steel (MS) on the entrance of decay tank room. In shielding efficiency analysis, the use of I-M concrete in the design of this concrete wall shows that it reduced the dose rate by a factor of at least 3.52 times approximately compared to ordinary reinforced concrete

Tension tests of concrete containment wall elements

International Nuclear Information System (INIS)

Schultz, D.M.; Julien, J.T.; Russel, H.G.

1984-01-01

Tension tests of concrete containment wall elements were conducted as part of a three-phase research program sponsored by the Electric Power Research Institute (EPRI). The objective of the EPRI experimental/analytical program is twofold. The first objective is to provide the utility industry with a test-verified analytical method for making realistic estimates of actual capacities of reinforced and prestressed concrete containments under internal over-pressurization from postulated degraded core accidents. The second objective is to determine qualitative and quantitative leak rate characteristics of typical containment cross-sections with and without penetrations. This paper covers the experimental portion to the EPRI program. The testing program for Phase 1 included eight large-scale specimens representing elements from the wall of a containment. Each specimen was 60-in (1525-mm) square, 24-in (610-mm) thick, and had full-size reinforcing bars. Six specimens were representative of prototypical reinforced concrete containment designs. The remaining two specimens represented prototypical prestressed containment designs. Various reinforcement configurations and loading arrangements resulted in data that permit comparisons of the effects of controlled variables on cracking and subsequent concrete/reinforcement/liner interaction in containment elements. Subtle differences, due to variations in reinforcement patterns and load applications among the eight specimens, are being used to benchmark the codes being developed in the analytical portion of the EPRI program. Phases 2 and 3 of the test program will examine leak rate characteristics and failure mechanisms at penetrations and structural discontinuities. (orig.)

Finite element modeling of tornado missile impact on reinforced concrete wall panels

International Nuclear Information System (INIS)

Zhang, Y.; Vallabhan, C.V.G.; McDonald, J.R.

1993-01-01

This paper describes a finite element model for the impact of large tornado-generated missiles with reinforced concrete wall panels. The analysis predicts the dynamic response of a wall panel when impacted by a missile with a large contact area such as an automobile. Quadratic finite elements are used to discretize the domain of the wall panel. Fundamental assumptions are based on the Mindlin and the related Reinsser plate theories. An 'embedded' model is employed to account for the reinforcing bars. The nonlinear behavior of concrete and steel bars are analyzed by means of time-dependent constitutive relationships. A model is proposed to describe the initial and subsequent yield surfaces of concrete material, which avoids underestimation of the effect of high hydrostatic stresses on the yielding behavior of concrete. Ottosen's four-parameter failure criterion is used to define the failure surface of concrete. A crack monitoring algorithm accounts for post-cracking and post-crushing behavior of concrete. Explicit time step integration of nonlinear dynamic equations are carried out using the finite element discretization of a concrete wall panel. As a practical application of the analysis technique, the contact failure pressure for a particular panel geometry can be calculated. The contact failure pressure and the elapsed time to failure after missile contact define a rectangular or triangular impulse loading to produce failure of the panel. Since automobile crashes are known to produce triangular impulse loads, the two pulses (failure and impact) can be compared to determine if a particular impact will fail the panels. Thus, a particular concrete panel can be analyzed to determine if it will fail under a postulated missile impact

Post-cracking behavior of blocks, prisms, and small concrete walls reinforced with plant fiber

Directory of Open Access Journals (Sweden)

I. I. Soto

Full Text Available Structural masonry using concrete blocks promotes the rationalization of construction projects, lowering the final cost of a building through the elimination of forms and the reduction of the consumption of reinforcement bars. Moreover, production of a block containing a combination of concrete and vegetable fiber sisal results in a unit with properties such as mechanical strength, stiffness, flexibility, ability to absorb energy, and post-cracking behavior that are comparable to those of a block produced with plain concrete. Herein are reported the results of a study on the post-cracking behavior of blocks, prisms, and small walls reinforced with sisal fibers (lengths of 20 mm and 40 mm added at volume fractions of 0.5% and 1%. Tests were performed to characterize the fibers and blocks and to determine the compressive strength of the units, prisms, and small walls. The deformation modulus of the elements was calculated and the stress-strain curves were plotted to gain a better understanding of the values obtained. The compression test results for the small walls reinforced with fibers were similar to those of the reference walls and better than the blocks and prisms with added fibers, which had resistances lower than those of the corresponding conventional materials. All elements prepared with the addition of sisal exhibited an increase in the deformation capacity (conferred by the fibers, which was observed in the stress-strain curves. The failure mode of the reference elements was characterized by an abrupt fracture, whereas the reinforced elements underwent ductile breakage. This result was because of the presence of the fibers, which remained attached to the faces of the cracks via adhesion to the cement matrix, thus preventing loss of continuity in the material. Therefore, the cement/plant fiber composites are advantageous in terms of their ductility and ability to resist further damage after cracking.

Non destructive measurement for the penetration of contamination inside concrete walls

International Nuclear Information System (INIS)

Rottner, B.

1998-01-01

The scope of this work is to determine the penetration depth of the contamination inside materials like concrete, only using external measurements, avoiding for instance to drill holes in the concrete wall. When dismantling NPP, concrete represents a significant part of the amount of waste. It is then interesting to segregate concrete into different types of waste: ordinary waste, very low level active waste,... This method makes it possible to generate a three dimensional map of the contamination in a concrete wall; this map car be used to adapt the dismantling scenario, and the tools, in order to: - first: decontaminate the wall by scraping the identified contaminated parts, which generates a small quantity of active waste; - second: break down the wall using non nuclear specific methods, generating a large quantity of ordinary waste. The method is based on spectrometric measurements, using two types of information: - the peak to peak ratios for a single radio-nuclide; - the ratio of the peak surface to the baseline enhancement under the peak. Both ratios vary with the penetration depth of the contamination, but rot in the same way. Therefore, the information which is used, will preferably depends on the depth. The correlation of the two ratios to the penetration depth is computed, using two specific calculation codes. One computes the sensitivity of the detector to the direct rays and the other computes the spectrum shape. (author)

Review of Repair Materials for Fire-Damaged Reinforced Concrete Structures

Science.gov (United States)

Zahid, MZA Mohd; Abu Bakar, BH; Nazri, FM; Ahmad, MM; Muhamad, K.

2018-03-01

Reinforced concrete (RC) structures perform well during fire and may be repaired after the fire incident because their low heat conductivity prevents the loss or degradation of mechanical strength of the concrete core and internal reinforcing steel. When an RC structure is heated to more than 500 °C, mechanical properties such as compressive strength, stiffness, and tensile strength start to degrade and deformations occur. Although the fire-exposed RC structure shows no visible damage, its residual strength decreases compared with that in the pre-fire state. Upon thorough assessment, the fire-damaged RC structure can be repaired or strengthened, instead of subjecting to partial or total demolition followed by reconstruction. The structure can be repaired using several materials, such as carbon fiber-reinforced polymer, glass fiber-reinforced polymer, normal strength concrete, fiber-reinforced concrete, ferrocement, epoxy resin mortar, and high-performance concrete. Selecting an appropriate repair material that must be compatible with the substrate or base material is a vital step to ensure successful repair. This paper reviews existing repair materials and factors affecting their performance. Of the materials considered, ultra-high-performance fiber-reinforced concrete (UHPFRC) exhibits huge potential for repairing fire-damaged RC structures but lack of information available. Hence, further studies must be performed to assess the potential of UHPFRC in rehabilitating fire-damaged RC structures.

Damage Analysis and Evaluation of High Strength Concrete Frame Based on Deformation-Energy Damage Model

Directory of Open Access Journals (Sweden)

Huang-bin Lin

2015-01-01

Full Text Available A new method of characterizing the damage of high strength concrete structures is presented, which is based on the deformation energy double parameters damage model and incorporates both of the main forms of damage by earthquakes: first time damage beyond destruction and energy consumption. Firstly, test data of high strength reinforced concrete (RC columns were evaluated. Then, the relationship between stiffness degradation, strength degradation, and ductility performance was obtained. And an expression for damage in terms of model parameters was determined, as well as the critical input data for the restoring force model to be used in analytical damage evaluation. Experimentally, the unloading stiffness was found to be related to the cycle number. Then, a correction for this changing was applied to better describe the unloading phenomenon and compensate for the shortcomings of structure elastic-plastic time history analysis. The above algorithm was embedded into an IDARC program. Finally, a case study of high strength RC multistory frames was presented. Under various seismic wave inputs, the structural damages were predicted. The damage model and correction algorithm of stiffness unloading were proved to be suitable and applicable in engineering design and damage evaluation of a high strength concrete structure.

Coda Wave Interferometry Method Applied in Structural Monitoring to Assess Damage Evolution in Masonry and Concrete Structures

International Nuclear Information System (INIS)

Masera, D; Bocca, P; Grazzini, A

2011-01-01

In this experimental program the main goal is to monitor the damage evolution in masonry and concrete structures by Acoustic Emission (AE) signal analysis applying a well-know seismic method. For this reason the concept of the coda wave interferometry is applied to AE signal recorded during the tests. Acoustic Emission (AE) are very effective non-destructive techniques applied to identify micro and macro-defects and their temporal evolution in several materials. This technique permits to estimate the velocity of ultrasound waves propagation and the amount of energy released during fracture propagation to obtain information on the criticality of the ongoing process. By means of AE monitoring, an experimental analysis on a set of reinforced masonry walls under variable amplitude loading and strengthening reinforced concrete (RC) beams under monotonic static load has been carried out. In the reinforced masonry wall, cyclic fatigue stress has been applied to accelerate the static creep and to forecast the corresponding creep behaviour of masonry under static long-time loading. During the tests, the evaluation of fracture growth is monitored by coda wave interferometry which represents a novel approach in structural monitoring based on AE relative change velocity of coda signal. In general, the sensitivity of coda waves has been used to estimate velocity changes in fault zones, in volcanoes, in a mining environment, and in ultrasound experiments. This method uses multiple scattered waves, which travelled through the material along numerous paths, to infer tiny temporal changes in the wave velocity. The applied method has the potential to be used as a 'damage-gauge' for monitoring velocity changes as a sign of damage evolution into masonry and concrete structures.

Coda Wave Interferometry Method Applied in Structural Monitoring to Assess Damage Evolution in Masonry and Concrete Structures

Energy Technology Data Exchange (ETDEWEB)

Masera, D; Bocca, P; Grazzini, A, E-mail: davide.masera@polito.it [Department of Structural and Geotechnical Engineering - Politecnico di Torino, corso Duca degli Abruzzi 24, 10129 Turin (Italy)

2011-07-19

In this experimental program the main goal is to monitor the damage evolution in masonry and concrete structures by Acoustic Emission (AE) signal analysis applying a well-know seismic method. For this reason the concept of the coda wave interferometry is applied to AE signal recorded during the tests. Acoustic Emission (AE) are very effective non-destructive techniques applied to identify micro and macro-defects and their temporal evolution in several materials. This technique permits to estimate the velocity of ultrasound waves propagation and the amount of energy released during fracture propagation to obtain information on the criticality of the ongoing process. By means of AE monitoring, an experimental analysis on a set of reinforced masonry walls under variable amplitude loading and strengthening reinforced concrete (RC) beams under monotonic static load has been carried out. In the reinforced masonry wall, cyclic fatigue stress has been applied to accelerate the static creep and to forecast the corresponding creep behaviour of masonry under static long-time loading. During the tests, the evaluation of fracture growth is monitored by coda wave interferometry which represents a novel approach in structural monitoring based on AE relative change velocity of coda signal. In general, the sensitivity of coda waves has been used to estimate velocity changes in fault zones, in volcanoes, in a mining environment, and in ultrasound experiments. This method uses multiple scattered waves, which travelled through the material along numerous paths, to infer tiny temporal changes in the wave velocity. The applied method has the potential to be used as a 'damage-gauge' for monitoring velocity changes as a sign of damage evolution into masonry and concrete structures.

Fragility assessment method of Concrete Wall Subjected to Impact Loading

International Nuclear Information System (INIS)

Hahm, Daegi; Shin, Sang Shup; Choi, In-Kil

2014-01-01

These studies have been aimed to verify and ensure the safety of the targeted walls and structures especially in the viewpoint of the deterministic approach. However, recently, the regulation and the assessment of the safety of the nuclear power plants (NPPs) against to an aircraft impact are strongly encouraged to adopt a probabilistic approach, i.e., the probabilistic risk assessment of an aircraft impact. In Korea, research to develop aircraft impact risk quantification technology was initiated in 2012 by Korea Atomic Energy Research Institute (KAERI). In this paper, for the one example of the probabilistic safety assessment approach, a method to estimate the failure probability and fragility of concrete wall subjected to impact loading caused by missiles or engine parts of aircrafts will be introduced. This method and the corresponding results will be used for the total technical roadmap and the procedure to assess the aircraft impact risk (Fig.1). A method and corresponding results of the estimation of the failure probability and fragility for a concrete wall subjected to impact loadings caused by missiles or engine parts of aircrafts was introduced. The detailed information of the target concrete wall in NPP, and the example aircraft engine model is considered safeguard information (SGI), and is not contained in this paper

Smeared crack modelling approach for corrosion-induced concrete damage

DEFF Research Database (Denmark)

Thybo, Anna Emilie Anusha; Michel, Alexander; Stang, Henrik

2017-01-01

In this paper a smeared crack modelling approach is used to simulate corrosion-induced damage in reinforced concrete. The presented modelling approach utilizes a thermal analogy to mimic the expansive nature of solid corrosion products, while taking into account the penetration of corrosion...... products into the surrounding concrete, non-uniform precipitation of corrosion products, and creep. To demonstrate the applicability of the presented modelling approach, numerical predictions in terms of corrosion-induced deformations as well as formation and propagation of micro- and macrocracks were......-induced damage phenomena in reinforced concrete. Moreover, good agreements were also found between experimental and numerical data for corrosion-induced deformations along the circumference of the reinforcement....

Structural pounding of concrete frame structure with masonry infill wall under seismic loading

Science.gov (United States)

Ismail, Rozaina; Hasnan, Mohd Hafizudin; Shamsudin, Nurhanis

2017-10-01

Structural pounding is additional problem than the other harmful damage that may occurs due to the earthquake vibrations. A lot of study has been made by past researcher but most of them did not include the walls. The infill masonry walls are rarely involved analysis of structural systems but it does contribute to earthquake response of the structures. In this research, a comparison between adjacent building of 10-storey and 7-storey concrete frame structure without of masonry infill walls and the same dynamic properties of buildings. The diagonal strut approach is adopted for modeling masonry infill walls. This research also focused on finding critical building separation in order to prevent the adjacent structures from pounding. LUSAS FEA v14.03 software has been used for modeling analyzing the behavior of structures due to seismic loading and the displacement each floor of the building has been taken in order to determine the critical separation distance between the buildings. From the analysis that has been done, it is found that masonry infill walls do affect the structures behavior under seismic load. Structures without masonry infill walls needs more distance between the structures to prevent structural pounding due to higher displacement of the buildings when it sways under seismic load compared to structures with masonry infill walls. This shows that contribution of masonry infill walls to the analysis of structures cannot be neglected.

Strengthening and repairing of damaged concrete beams

International Nuclear Information System (INIS)

Mahmoud, M.K.; Ebrahiem, G.T.A.; Hassanein, S.A.

2005-01-01

The main part in this investigation is concerned with the advanced techniques of retrofitting damaged reinforced concrete (RC) beams. Glass fiber reinforced plastics (GFRP) were employed for this purpose. The aim of this paper is to investigate the advantage of using glass fiber .reinforced plastics (GFRP) to retrofit and repair damaged reinforced concrete beams. In this investigation, concrete beam specimens were preloaded up to the 60%, 70% arid 80% of their ultimate load capacity. The damaged beams were then repaired with one layer of FRP composite wraps and re-tested. Plastic reinforced by glass fibers 20% fiber volume fractions and with various fiber arrangement unidirectional, bi-directional and chopped were also considered. Four points bending test was adopted. The bending tests were performed on fourteen RC beams in addition to a two control, all of them were (225 30 15) cm in dimensions, and with a typical reinforcement details. Test results were indicative of the merit of using GFRP, as the ultimate loads were almost restored and the modes of failure were of ductile nature. Even more an increase in the ultimate bearing capacity was recorded for some of the retrofitted beams. The effects of the previously mentioned parameters on the cracking pattern and failure mode were reported and thoroughly discussed

Application of a Reinforced Self-Compacting Concrete Jacket in Damaged Reinforced Concrete Beams under Monotonic and Repeated Loading

Directory of Open Access Journals (Sweden)

Constantin E. Chalioris

2013-01-01

Full Text Available This paper presents the findings of an experimental study on the application of a reinforced self-compacting concrete jacketing technique in damaged reinforced concrete beams. Test results of 12 specimens subjected to monotonic loading up to failure or under repeated loading steps prior to total failure are included. First, 6 beams were designed to be shear dominated, constructed by commonly used concrete, were initially tested, damaged, and failed in a brittle manner. Afterwards, the shear-damaged beams were retrofitted using a self-compacting concrete U-formed jacket that consisted of small diameter steel bars and U-formed stirrups in order to increase their shear resistance and potentially to alter their initially observed shear response to a more ductile one. The jacketed beams were retested under the same loading. Test results indicated that the application of reinforced self-compacting concrete jacketing in damaged reinforced concrete beams is a promising rehabilitation technique. All the jacketed beams showed enhanced overall structural response and 35% to 50% increased load bearing capacities. The ultimate shear load of the jacketed beams varied from 39.7 to 42.0 kN, whereas the capacity of the original beams was approximately 30% lower. Further, all the retrofitted specimens exhibited typical flexural response with high values of deflection ductility.

Perforation of a concrete slab by a missile: finite element approach

International Nuclear Information System (INIS)

Jamet, P.; Berriaud, C.; Millard, A.; Nahas, G.; Yuritzin, T.

1983-08-01

A specific concrete model has been developed to investigate the problem of concrete walls perforation by a missile: three types of damage are accounted for: traction damage, shear damage, hydrostatic pressure damage. In order to investigate the validity of this concrete model in simple compressive conditions, tests are performed in following configuration: microconcrete used in perforation tests is cast in a cylindrical mould 100 mm diameter, 50 mm wall thickness made of very strong steel. The concrete height is 400 mm. A silver layer is put on the inner face to decrease the friction coefficient. The load is transmitted to the contrete by means of a metal piston. A quasi static test is first performed using a hydraulic testing machine. A second one is then impacted by a 32 kg mass dropping from 19 meters. In both cases the displacement and the forces are recorded for comparison with calculation

Local damage to reinforced concrete structures caused by impact of aircraft engine missiles. Pt. 1

International Nuclear Information System (INIS)

Sugano, T.; Tsubota, H.; Kasai, Y.; Koshika, N.; Ohnuma, H.; Von Riesemann, W.A.; Bickel, D.C.; Parks, M.B.

1993-01-01

Structural damage induced by an aircraft crashing into a reinforced concrete structure includes local damage caused by the deformable engines, and global damage caused by the entire aircraft. Local damage to the target may consist of spalling of concrete from its front face together with missile penetration into it, scabbing of concrete from its rear face, and perforation of missile through it. Until now, local damage to concrete structures has been mainly evaluated by rigid missile impact tests. Past research work regarding local damage caused by impact of deformable missiles has been limited. This paper presents the results of a series of impact tests of small-, intermediate-, and full-scale engine models into reinforced concrete panels. The purpose of the tests was to determine the local damage to a reinforced concrete structure caused by the impact of a deformable aircraft engine. (orig.)

Cyclic behavior of low rise concrete shear walls containing recycled coarse and fine aggregates

NARCIS (Netherlands)

Qiao, Qiyun; Cao, Wanlin; Qian, Zhiwei; Li, Xiangyu; Zhang, Wenwen; Liu, Wenchao

2017-01-01

In this study, the cyclic behaviors of low rise concrete shear walls using recycled coarse or fine aggregates were investigated. Eight low rise Recycled Aggregates Concrete (RAC) shear wall specimens were designed and tested under a cyclic loading. The following parameters were varied:

Thermal Response Of An Aerated Concrete Wall With Micro-Encapsulated Phase Change Material

Science.gov (United States)

Halúzová, Dušana

2015-06-01

For many years Phase Change Materials (PCM) have attracted attention due to their ability to store large amounts of thermal energy. This property makes them a candidate for the use of passive heat storage. In many applications, they are used to avoid the overheating of the temperature of an indoor environment. This paper describes the behavior of phase change materials that are inbuilt in aerated concrete blocks. Two building samples of an aerated concrete wall were measured in laboratory equipment called "twin-boxes". The first box consists of a traditional aerated concrete wall; the second one has additional PCM micro-encapsulated in the wall. The heat flux through the wall was measured and compared to simulation results modeled in the ESP-r program. This experimental measurement provides a foundation for a model that can be used to analyze further building constructions.

Effect of a mechanical damage on permeability and moisture diffusivity of concrete

International Nuclear Information System (INIS)

Picandet, V.

2001-12-01

The effect of a mechanical damage on transfer parameters of concrete is an original point of view on the coupling between damage and durability. The studied transfer parameters, permeability and moisture diffusivity, allow to characterize the transport ability of a porous media to convey gases or water (liquid and vapour). The theoretical framework of the measurement of these parameters and its applications to concrete is pointed out. The experimental studies are carried on three types of concrete: ordinary concrete, high performance concrete, and high performance steel fiber reinforced concrete. Two kinds of damage are considered and generated in samples: - A continuous damage of the medium, obtained by cyclic uniaxial loading. It is characterized by a loss of stiffness and results in a diffuse microcracking.- A discrete or localised damage, obtained by a diametrical compression of cylindrical specimens. It is characterized by the presence of identifiable and measurable cracks. Measurements of gas permeability are taken using a constant head, Cembureau type, permeameter. For cracked samples, the procedure and analysis of the results are changed in order to make the evaluation of their gas and water permeability. The simple imbibition and positive head imbibition are the disturbances of the moisture equilibrium, which allow the evaluation of the material diffusivity. The local moisture contents of the specimen are measured using a gamma-ray attenuation method. The analysis of profiles using Boltzmann's transformation leads to the moisture diffusivity and then to the water permeability coefficients. Measurements of gas and water permeability are compared in both cases of considered damage. In the first case, a damage - permeability relationship dependent on the fluid of percolation but valid for all concrete types studied could be worked out. (author)

Analysis of factors influencing fire damage to concrete using nonlinear resonance vibration method

Energy Technology Data Exchange (ETDEWEB)

Park, Gang Kyu; Park, Sun Jong; Kwak, Hyo Gyoung [Civil and Environmental Engineering, Korea Advanced Institute of Science and Technology, KAIST, Daejeon (Korea, Republic of); Yim, Hong Jae [Dept. of Construction and Disaster Prevention Engineering, Kyungpook National University, Sangju (Korea, Republic of)

2015-04-15

In this study, the effects of different mix proportions and fire scenarios (exposure temperatures and post-fire-curing periods) on fire-damaged concrete were analyzed using a nonlinear resonance vibration method based on nonlinear acoustics. The hysteretic nonlinearity parameter was obtained, which can sensitively reflect the damage level of fire-damaged concrete. In addition, a splitting tensile strength test was performed on each fire-damaged specimen to evaluate the residual property. Using the results, a prediction model for estimating the residual strength of fire-damaged concrete was proposed on the basis of the correlation between the hysteretic nonlinearity parameter and the ratio of splitting tensile strength.

Radiation Damage In Reactor Cavity Concrete

Energy Technology Data Exchange (ETDEWEB)

Field, Kevin G [ORNL; Le Pape, Yann [ORNL; Naus, Dan J [ORNL; Remec, Igor [ORNL; Busby, Jeremy T [ORNL; Rosseel, Thomas M [ORNL; Wall, Dr. James Joseph [Electric Power Research Institute (EPRI)

2015-01-01

License renewal up to 60 years and the possibility of subsequent license renewal to 80 years has established a renewed focus on long-term aging of nuclear generating stations materials, and recently, on concrete. Large irreplaceable sections of most nuclear generating stations include concrete. The Expanded Materials Degradation Analysis (EMDA), jointly performed by the Department of Energy, the Nuclear Regulatory Commission and Industry, identified the urgent need to develop a consistent knowledge base on irradiation effects in concrete. Much of the historical mechanical performance data of irradiated concrete does not accurately reflect typical radiation conditions in NPPs or conditions out to 60 or 80 years of radiation exposure. To address these potential gaps in the knowledge base, The Electric Power Research Institute and Oak Ridge National Laboratory are working to disposition radiation damage as a degradation mechanism. This paper outlines the research program within this pathway including: (i) defining the upper bound of the neutron and gamma dose levels expected in the biological shield concrete for extended operation (80 years of operation and beyond), (ii) determining the effects of neutron and gamma irradiation as well as extended time at temperature on concrete, (iii) evaluating opportunities to irradiate prototypical concrete under accelerated neutron and gamma dose levels to establish a conservative bound and share data obtained from different flux, temperature, and fluence levels, (iv) evaluating opportunities to harvest and test irradiated concrete from international NPPs, (v) developing cooperative test programs to improve confidence in the results from the various concretes and research reactors, (vi) furthering the understanding of the effects of radiation on concrete (see companion paper) and (vii) establishing an international collaborative research and information exchange effort to leverage capabilities and knowledge.

Limit load analysis of thick-walled concrete structures

International Nuclear Information System (INIS)

Argyris, J.H.; Faust, G.; Willam, K.J.

1975-01-01

The paper illustrates the interaction of constitutive modeling and finite element solution techniques for limit load prediction of concrete structures. On the constitutive side, an engineering model of concrete fracture is developed in which the Mohr-Coulomb criterion is augmented by tension cut-off to describe incipient failure. Upon intersection with the stress path the failure surface collapses for brittle behaviour according to one of three softening rules, no-tension, no-cohesion, and no-friction. The stress transfer accompanying the energy dissipation during local failure is modelled by several fracture rules which are examined with regard to ultimate load prediction. On the numerical side the effect of finite element idealization is studied first as far as ultimate load convergence is concerned. Subsequently, incremental tangential and initial load techniques are compared together with the effect of step size. Limit load analyses of a thick-walled concrete ring and a lined concrete reactor closure conclude the paper with examples from practical engineering. (orig.) [de

Anisotropic damage and dynamic behavior of reinforced concrete structures until failure

International Nuclear Information System (INIS)

Chambart, M.

2009-09-01

Dynamic loadings such as impact on reinforced concrete structures lead to degradations and structural failures significantly different to the ones observed for quasi-static loadings. Local effects (spalling, compaction...) and global mechanisms (bending, shear, perforation...) are experimentally observed. Wave propagation due to dynamics loadings can lead to failure in tension in a part of a structure or a component previously in compression. Induced damage anisotropy in concrete is partly responsible for the dissymmetry of behavior between tension and compression. Concrete anisotropy can be modelled by means of a second order damage tensor. In the damage model considered, damage growth is governed by the positive extensions. The model, written in the thermodynamics framework, is robust and is able to compute efficiently Reinforced Concrete (RC) structures. The initial anisotropic model is here extended to dynamics by introducing a viscosity law to govern dynamic damage evolution. The strain rate effect observed experimentally in tension (strength increases with strain rate) is reproduced. In compression no strain rate is introduced since inertial forces seem sufficient to reproduce the strength enhancement in dynamics. One also focuses on regularization issues. For high strain rates the solution is regularized since the characteristic time introduced indirectly defines an internal length and since the damage rate is bounded by a maximum damage rate parameter (visco/delay damage law). This visco/delay regularization is efficient at large strain rates, otherwise, the delay in damage evolution is too small to let damage grow in a wide enough zone. For quasi-static or low speed dynamic cases, the regularization is gained by means of classical non-local damage. For intermediary loading rates where both the strain rate effect and the non-local regularization are needed, a non-local delay-damage model is written (and used in 3D computations). The example of a dynamic

Quantitative study on crack of meso-damage and fracture concrete ...

Indian Academy of Sciences (India)

lysis of the meso-fracture process of concrete materials is performed. ... the result of the accumulation and development of damage and cracks at the meso-level. ... characteristics of concrete under uniaxial compression used fractal theory, and ...

Nondestructive analysis of alkali-silica reaction damage in concrete slabs using shear waves

Science.gov (United States)

Khazanovich, Lev; Freeseman, Katelyn; Salles, Lucio; Clayton, Dwight

2018-04-01

Alkali-silica reaction (ASR) is the chemical reaction that occurs in concrete. It is caused by the interaction of alkalis in Portland cement and silica in aggregates and results in microcracks within the material. This type of damage has been the focus of nondestructive evaluation efforts in recent history, but no work was done on in-situ structures or large-scale samples. To address these limitations, an ultrasonic linear array device, MIRA, was utilized for this research. An experimental investigation was performed on four slabs with various levels of alkali-silica reaction at the Electric Power Research Institute (EPRI) [1]. One-period impulses with a target of 50kHz center frequency were selected in this study. We propose the use of the Hilbert Transform Indicator (HTI) for quantification of ASR damage [2]. A higher HTI value would be indicative of damaged concrete, while a low value represents sound concrete. In general, values below 90 are regarded as an indicator of sound concrete while values above 100 indicate the presence of damage [3]. The ability of the HTI values to distinguish between areas of damaged concrete was evident via the production of color intensity maps. The maps show that the control specimen, was in good condition, while other slabs exhibited higher levels of damage as indicated by the HTI values. It should be noted that extreme damage conditions were not present in any of the slabs. Evaluation of migration-based reconstructions can give a qualitative characterization of large scale or excessive subsurface damage. However, for detection of stochastic damage mechanisms such as freeze-thaw damage, evaluation of the individual time-history data can provide additional information. A comparison of the spatially diverse measurements on several concrete slabs with varying freeze-thaw damage levels is given in this study. Signal characterization scans of different levels of freeze-thaw damage at various transducer spacing is investigated. The

Cyclic Behavior of Low Rise Concrete Shear Walls Containing Recycled Coarse and Fine Aggregates.

Science.gov (United States)

Qiao, Qiyun; Cao, Wanlin; Qian, Zhiwei; Li, Xiangyu; Zhang, Wenwen; Liu, Wenchao

2017-12-07

In this study, the cyclic behaviors of low rise concrete shear walls using recycled coarse or fine aggregates were investigated. Eight low rise Recycled Aggregates Concrete (RAC) shear wall specimens were designed and tested under a cyclic loading. The following parameters were varied: replacement percentages of recycled coarse or fine aggregates, reinforcement ratio, axial force ratio and X-shaped rebars brace. The failure characteristics, hysteretic behavior, strength and deformation capacity, strain characteristics and stiffness were studied. Test results showed that the using of the Recycled Coarse Aggregates (RCA) and its replacement ratio had almost no influence on the mechanical behavior of the shear wall; however, the using of Recycled Fine Aggregates (RFA) had a certain influence on the ductility of the shear wall. When the reinforcement ratio increased, the strength and ductility also increased. By increasing the axial force ratio, the strength increased but the ductility decreased significantly. The encased brace had a significant effect on enhancing the RAC shear walls. The experimental maximum strengths were evaluated with existing design codes, it was indicated that the strength evaluation of the low rise RAC shear walls can follow the existing design codes of the conventional concrete shear walls.

Stiffness of reinforced concrete walls resisting in-place shear -- Tier 2: Aging and durability of concrete used in nuclear power plants. Final report

International Nuclear Information System (INIS)

Monteiro, P.J.M.; Moehle, J.P.

1995-12-01

Reinforced concrete walls are commonly used in power-plant construction to resist earthquake effects. Determination of wall stiffness is of particular importance for establishing design forces on attached equipment. Available experimental data indicate differences between the measured and calculated stiffness of walls in cases where concrete mechanical properties are well defined. Additional data indicate that in-situ concrete mechanical properties may differ significantly from those specified in design. The work summarized in this report was undertaken to investigate the mechanical properties of concrete considering aging and deterioration. Existing data on mechanical properties of concrete are evaluated, and new tests are carried out on concrete cylinders batched for nuclear power plants and stored under controlled conditions for up to twenty years. It is concluded that concretes batched for nuclear power plants commonly have 28-day strength that exceeds the design value by at least 1000 psi. Under curing conditions representative of those in the interior of thick concrete elements, strength gain with time can be estimated conservatively using the expression proposed by ACI Committee 209, with strengths at 25 years being approximately 1.3 times the 28-day strength. Young's modulus can be estimated using the expression given by ACI Committee 318. Variabilities in mechanical properties are identified. A review of concrete durability identified the main causes and results of concrete deterioration that are relevant for the class of concretes and structures commonly used in nuclear power plants. Prospects for identifying the occurrence and predicting the extent of deterioration are discussed

Electrical impedance tomography-based sensing skin for quantitative imaging of damage in concrete

International Nuclear Information System (INIS)

Hallaji, Milad; Pour-Ghaz, Mohammad; Seppänen, Aku

2014-01-01

This paper outlines the development of a large-area sensing skin for damage detection in concrete structures. The developed sensing skin consists of a thin layer of electrically conductive copper paint that is applied to the surface of the concrete. Cracking of the concrete substrate results in the rupture of the sensing skin, decreasing its electrical conductivity locally. The decrease in conductivity is detected with electrical impedance tomography (EIT) imaging. In previous works, electrically based sensing skins have provided only qualitative information on the damage on the substrate surface. In this paper, we study whether quantitative imaging of the damage is possible. We utilize application-specific models and computational methods in the image reconstruction, including a total variation (TV) prior model for the damage and an approximate correction of the modeling errors caused by the inhomogeneity of the painted sensing skin. The developed damage detection method is tested experimentally by applying the sensing skin to polymeric substrates and a reinforced concrete beam under four-point bending. In all test cases, the EIT-based sensing skin provides quantitative information on cracks and/or other damages on the substrate surface: featuring a very low conductivity in the damage locations, and a reliable indication of the lengths and shapes of the cracks. The results strongly support the applicability of the painted EIT-based sensing skin for damage detection in reinforced concrete elements and other substrates. (paper)

Effect of shear connectors on local buckling and composite action in steel concrete composite walls

International Nuclear Information System (INIS)

Zhang, Kai; Varma, Amit H.; Malushte, Sanjeev R.; Gallocher, Stewart

2014-01-01

Steel concrete composite (SC) walls are being used for the third generation nuclear power plants, and also being considered for small modular reactors. SC walls consist of thick concrete walls with exterior steel faceplates serving as reinforcement. These steel faceplates are anchored to the concrete infill using shear connectors, for example, headed steel studs. The steel faceplate thickness (t p ) and yield stress (F y ), and the shear connector spacing (s), stiffness (k s ), and strength (Q n ) determine: (a) the level of composite action between the steel plates and the concrete infill, (b) the development length of steel faceplates, and (c) the local buckling of the steel faceplates. Thus, the shear connectors have a significant influence on the behavior of composite SC walls, and should be designed accordingly. This paper presents the effects of shear connector design on the level of composite action and development length of steel faceplates in SC walls. The maximum steel plate slenderness, i.e., ratio of shear connector spacing-to-plate thickness (s/t p ) ratio to prevent local buckling before yielding is also developed based on the existing experimental database and additional numerical analysis

Effect of shear connectors on local buckling and composite action in steel concrete composite walls

Energy Technology Data Exchange (ETDEWEB)

Zhang, Kai, E-mail: kai-zh@purdue.edu [School of Civil Engineering, Purdue University, West Lafayette, IN (United States); Varma, Amit H., E-mail: ahvarma@purdue.edu [School of Civil Engineering, Purdue University, West Lafayette, IN (United States); Malushte, Sanjeev R., E-mail: smalusht@bechtel.com [Bechtel Power Corporation, Frederick, MD (United States); Gallocher, Stewart, E-mail: stewart.gallocher@steelbricks.com [Modular Walling Systems Ltd., Glasgow (United Kingdom)

2014-04-01

Steel concrete composite (SC) walls are being used for the third generation nuclear power plants, and also being considered for small modular reactors. SC walls consist of thick concrete walls with exterior steel faceplates serving as reinforcement. These steel faceplates are anchored to the concrete infill using shear connectors, for example, headed steel studs. The steel faceplate thickness (t{sub p}) and yield stress (F{sub y}), and the shear connector spacing (s), stiffness (k{sub s}), and strength (Q{sub n}) determine: (a) the level of composite action between the steel plates and the concrete infill, (b) the development length of steel faceplates, and (c) the local buckling of the steel faceplates. Thus, the shear connectors have a significant influence on the behavior of composite SC walls, and should be designed accordingly. This paper presents the effects of shear connector design on the level of composite action and development length of steel faceplates in SC walls. The maximum steel plate slenderness, i.e., ratio of shear connector spacing-to-plate thickness (s/t{sub p}) ratio to prevent local buckling before yielding is also developed based on the existing experimental database and additional numerical analysis.

Tritium contamination of concrete walls and floors in tritium-handling laboratory

International Nuclear Information System (INIS)

Kawano, T.; Kuroyanagi, M.; Tabei, T.

2006-01-01

relation between surface contamination obtained with the smear method and inner contamination obtained with the direct-immersion method. The results revealed that surface contamination did not correspond to inner contamination. This means that contamination of the concrete walls and floors themselves cannot be evaluated from data on surface contamination. We also evaluated the dependence of tritium contamination in concrete walls and floors on depth. Maximum contamination was frequently found inside walls and floors. It could be inferred that tritium existed in the chemical form of hydrogen molecules (tritium gas) that crept into deeper locations within concrete walls or floors, changed its form to water through an isotope exchange reaction, and remained there. (authors)

The Backscattering of Gamma Radiation from Plane Concrete Walls

Energy Technology Data Exchange (ETDEWEB)

Leimdoerfer, M

1962-12-15

Monte Carlo calculations have been performed for source energies from 1 to 10 MeV, and normally incident radiation, showing that 90 % of the infinite-barrier energy flux albedo is reached with a 40 cm concrete wall. The spectrum of backscattered energy flux is presented for the above sources and wall thicknesses ranging from 5 to 50 cm, An analytical expression, based on a single-scattering approximation, is shown to produce good fits to the Monte Carlo results.

Cyclic Behavior of Low Rise Concrete Shear Walls Containing Recycled Coarse and Fine Aggregates

Directory of Open Access Journals (Sweden)

Qiyun Qiao

2017-12-01

Full Text Available In this study, the cyclic behaviors of low rise concrete shear walls using recycled coarse or fine aggregates were investigated. Eight low rise Recycled Aggregates Concrete (RAC shear wall specimens were designed and tested under a cyclic loading. The following parameters were varied: replacement percentages of recycled coarse or fine aggregates, reinforcement ratio, axial force ratio and X-shaped rebars brace. The failure characteristics, hysteretic behavior, strength and deformation capacity, strain characteristics and stiffness were studied. Test results showed that the using of the Recycled Coarse Aggregates (RCA and its replacement ratio had almost no influence on the mechanical behavior of the shear wall; however, the using of Recycled Fine Aggregates (RFA had a certain influence on the ductility of the shear wall. When the reinforcement ratio increased, the strength and ductility also increased. By increasing the axial force ratio, the strength increased but the ductility decreased significantly. The encased brace had a significant effect on enhancing the RAC shear walls. The experimental maximum strengths were evaluated with existing design codes, it was indicated that the strength evaluation of the low rise RAC shear walls can follow the existing design codes of the conventional concrete shear walls.

Nitrate Diffusional Releases from the Saltstone Facility, Vault 2, with Respect to Different Concrete Wall Thicknesses

International Nuclear Information System (INIS)

ROBERT, HIERGESELL

2005-01-01

To assist the Saltstone Vault 2 Design Team, an investigation was conducted to evaluate the effectiveness of alternative concrete wall thicknesses in limiting nitrate diffusion away from the planned facility. While the current design calls for 18-inch concrete walls, alternative thicknesses of 12-in, 8-in, and 6-in were evaluated using a simplified 1-D numerical model. To serve as a guide for Saltstone Vault 2 conceptual design, the results of this investigation were applied to Saltstone Vault 4 to determine what the hypothetical limits would be for concrete wall thicknesses thinner than the planned 18-inches. This was accomplished by adjusting the Vault 4 Limits, based on the increased nitrate diffusion rates through the thinner concrete walls, such that the 100-m well limit of 44 mg/L of nitrate as nitrate was not exceeded. The implication of these preliminary results is that as thinner vault walls are implemented there is a larger release of nitrate, thus necessitating optimal vault placement to minimize the number of vaults placed along a single groundwater flow path leading to the discharge zone

Damage modelling in concrete subject to sulfate attack

Directory of Open Access Journals (Sweden)

N. Cefis

2014-07-01

Full Text Available In this paper, we consider the mechanical effect of the sulfate attack on concrete. The durability analysis of concrete structures in contact to external sulfate solutions requires the definition of a proper diffusion-reaction model, for the computation of the varying sulfate concentration and of the consequent ettringite formation, coupled to a mechanical model for the prediction of swelling and material degradation. In this work, we make use of a two-ions formulation of the reactive-diffusion problem and we propose a bi-phase chemo-elastic damage model aimed to simulate the mechanical response of concrete and apt to be used in structural analyses.

Chloride Transport in OPC Concrete Subjected to the Freeze and Thaw Damage

Directory of Open Access Journals (Sweden)

Ki Yong Ann

2017-01-01

Full Text Available To predict the durability of a concrete structure under the coupling degradation consisting of the frosting and chloride attack, microstructural analysis of the concrete pore structure should be accompanied. In this study, the correlation between the pore structure and chloride migration for OPC concrete was evaluated at the different cement content in the concrete mix accounting for 300, 350, and 400 kg/m3 at 0.45 of a free water cement ratio. The influence of frosting damage on the rate of chloride transport was assessed by testing with concrete specimens subjected to a rapid freezing and thawing cyclic environment. As a result, it was found that chloride transport was accelerated by frost damage, which was more influential at the lower cement content. The microscopic examination of the pore structure showed that the freezing environment increased the volume of the large capillary pore in the concrete matrix.

A Coupled Plastic Damage Model for Concrete considering the Effect of Damage on Plastic Flow

OpenAIRE

Zhou, Feng; Cheng, Guangxu

2015-01-01

A coupled plastic damage model with two damage scalars is proposed to describe the nonlinear features of concrete. The constitutive formulations are developed by assuming that damage can be represented effectively in the material compliance tensor. Damage evolution law and plastic damage coupling are described using the framework of irreversible thermodynamics. The plasticity part is developed without using the effective stress concept. A plastic yield function based on the true stress is ado...

Digital laminography assessment of the damage in concrete exposed to freezing temperatures

KAUST Repository

Wakimoto, Kentaro

2008-10-01

The research explores the possibility of using digital laminography as a non-destructive inspection X-ray method to image the damage existing in concrete exposed to low temperatures. Freezing-thawing and scaling tests were performed and digital laminography was used to determine the degree of damage existing inside the concrete samples. First, digital laminography was performed on the concrete sample and then a visual inspection was done by slicing the sample after it was vacuum-impregnated with epoxy in order to compare the differences in crack width. © 2008 Elsevier Ltd. All rights reserved.

Digital laminography assessment of the damage in concrete exposed to freezing temperatures

KAUST Repository

Wakimoto, Kentaro; Blunt, Joshua; Carlos, Cruz; Monteiro, Paulo J.M.; Ostertag, Claudia P.; Albert, Richard

2008-01-01

The research explores the possibility of using digital laminography as a non-destructive inspection X-ray method to image the damage existing in concrete exposed to low temperatures. Freezing-thawing and scaling tests were performed and digital laminography was used to determine the degree of damage existing inside the concrete samples. First, digital laminography was performed on the concrete sample and then a visual inspection was done by slicing the sample after it was vacuum-impregnated with epoxy in order to compare the differences in crack width. © 2008 Elsevier Ltd. All rights reserved.

Influence of Freeze-Thaw Damage on the Steel Corrosion and Bond-Slip Behavior in the Reinforced Concrete

Directory of Open Access Journals (Sweden)

Fangzhi Zhu

2016-01-01

Full Text Available This paper mainly studies the behavior of steel corrosion in various reinforced concrete under freeze-thaw environment. The influence of thickness of concrete cover is also discussed. Additionally, the bond-slip behavior of the reinforced concrete after suffering the freeze-thaw damage and steel corrosion has also be presented. The results show that the freeze-thaw damage aggravates the steel corrosion in concrete, and the results become more obvious in the concrete after suffering serious freeze-thaw damage. Compared with the ordinary concrete, both air entrained concrete and waterproofing concrete possess better resistance to steel corrosion under the same freeze-thaw environment. Moreover, increasing the thicknesses of concrete cover is also an effective method of improving the resistance to steel corrosion. The bond-slip behavior of reinforced concrete with corroded steel decreases with the increase of freeze-thaw damage, especially for the concrete that suffered high freeze-thaw cycles. Moreover, there exists a good correlation between the parameters of bond-slip and freeze-thaw cycles. The steel corrosion and bond-slip behavior of reinforced concrete should be considered serious under freeze-thaw cycles environment, which significantly impact the durability and safety of concrete structure.

Effect of Post-Fire Curing on the Residual Mechanical Properties of Fire-Damaged Self-Compacting Concrete

NARCIS (Netherlands)

Mirmomeni, M.; Heidarpour, A.; Schlangen, H.E.J.G.; Smith, S; Saouma, V.; Bolander, J.; Landis, E.

2016-01-01

Concrete is recognized for being a fire-resistant construction material. At elevated temperatures concrete can, however, undergo considerable damage such as strength degradation, cracking, and explosive spalling. In recent decades, reuse of fire-damaged concrete structures by means of developing

The Neural Correlates of Abstract and Concrete Words: Evidence from Brain-Damaged Patients

Directory of Open Access Journals (Sweden)

Giorgia Martello

2013-08-01

Full Text Available Neuropsychological and activation studies on the neural correlates of abstract and concrete words have produced contrasting results. The present study explores the anatomical substrates of abstract/concrete words in 22 brain-damaged patients with a single vascular lesion either in the right or left hemisphere. One hundred and twenty (60 concrete and 60 abstract noun triplets were used for a semantic similarity judgment task. We found a significant interaction in word type × group since left temporal brain-damaged patients performed significantly better with concrete than abstract words. Lesion mapping of patients with predominant temporal damage showed that the left superior and middle temporal gyri and the insula were the areas of major overlapping, while the anterior portion of the left temporal lobe was generally spared. Errors on abstract words mainly concerned (although at a non-significant level semantically associate targets, while in the case of concrete words, coordinate targets were significantly more impaired than associate ones. Our results suggest that the left superior and middle temporal gyri and the insula are crucial regions in processing abstract words. They also confirm the hypothesis of a semantic similarity vs. associative organization of concrete and abstract concepts.

The Heat Transfer Coefficient of Recycled Concrete Bricks Combination with EPS Insulation Board Wall

Directory of Open Access Journals (Sweden)

Jianhua Li

2015-01-01

Full Text Available Four tectonic forms samples were conducted to test their heat transfer coefficients. By analyzing and comparing the test values and theoretical values of the heat transfer coefficient, a corrected-value calculation method for determining the heat transfer coefficient was proposed; the proposed method was proved to be reasonably correct. The results indicated that the recycled concrete brick wall heat transfer coefficient is higher than that of the clay brick wall, the heat transfer coefficient of recycled concrete brick wall could be effectively reduced when combined with the EPS insulation board, and the sandwich insulation type was better than that of external thermal insulation type.

Sensitivity of PZT Impedance Sensors for Damage Detection of Concrete Structures.

Science.gov (United States)

Yang, Yaowen; Hu, Yuhang; Lu, Yong

2008-01-21

Piezoelectric ceramic Lead Zirconate Titanate (PZT) based electro-mechanicalimpedance (EMI) technique for structural health monitoring (SHM) has been successfullyapplied to various engineering systems. However, fundamental research work on thesensitivity of the PZT impedance sensors for damage detection is still in need. In thetraditional EMI method, the PZT electro-mechanical (EM) admittance (inverse of theimpedance) is used as damage indicator, which is difficult to specify the effect of damage onstructural properties. This paper uses the structural mechanical impedance (SMI) extractedfrom the PZT EM admittance signature as the damage indicator. A comparison study on thesensitivity of the EM admittance and the structural mechanical impedance to the damages ina concrete structure is conducted. Results show that the SMI is more sensitive to the damagethan the EM admittance thus a better indicator for damage detection. Furthermore, this paperproposes a dynamic system consisting of a number of single-degree-of-freedom elementswith mass, spring and damper components to model the SMI. A genetic algorithm isemployed to search for the optimal value of the unknown parameters in the dynamic system.An experiment is carried out on a two-storey concrete frame subjected to base vibrations thatsimulate earthquake. A number of PZT sensors are regularly arrayed and bonded to the framestructure to acquire PZT EM admittance signatures. The relationship between the damageindex and the distance of the PZT sensor from the damage is studied. Consequently, thesensitivity of the PZT sensors is discussed and their sensing region in concrete is derived.

Structural damages of L'Aquila (Italy earthquake

Directory of Open Access Journals (Sweden)

H. Kaplan

2010-03-01

Full Text Available On 6 April 2009 an earthquake of magnitude 6.3 occurred in L'Aquila city, Italy. In the city center and surrounding villages many masonry and reinforced concrete (RC buildings were heavily damaged or collapsed. After the earthquake, the inspection carried out in the region provided relevant results concerning the quality of the materials, method of construction and the performance of the structures. The region was initially inhabited in the 13th century and has many historic structures. The main structural materials are unreinforced masonry (URM composed of rubble stone, brick, and hollow clay tile. Masonry units suffered the worst damage. Wood flooring systems and corrugated steel roofs are common in URM buildings. Moreover, unconfined gable walls, excessive wall thicknesses without connection with each other are among the most common deficiencies of poorly constructed masonry structures. These walls caused an increase in earthquake loads. The quality of the materials and the construction were not in accordance with the standards. On the other hand, several modern, non-ductile concrete frame buildings have collapsed. Poor concrete quality and poor reinforcement detailing caused damage in reinforced concrete structures. Furthermore, many structural deficiencies such as non-ductile detailing, strong beams-weak columns and were commonly observed. In this paper, reasons why the buildings were damaged in the 6 April 2009 earthquake in L'Aquila, Italy are given. Some suggestions are made to prevent such disasters in the future.

Damage detection of simply supported reinforced concrete beam by S transform

Science.gov (United States)

Liu, Ning; Xi, Jiaxin; Zhang, Xuebing; Liu, Zhenzhou

2017-08-01

Signal processing is the key component of vibration-based structural damage detection. The S transform is variable window of short time Fourier transform (STFT) or an extension of wavelet transform (WT). The goal of using S transform is to extract subtle changes in the vibration signals in order to detect and quantify the damage in the structure. This paper presents the concentrated load is applied to the simply supported reinforced concrete beam and adopting the stepwise loading method, the vibration signals of each loading and unloading state is obtained by using the hammer impact. Then the vibration data of the reinforced concrete beam pre-damage and post-damage is analysed by S transform. Experimental result shows the potential ability of S transform in identifying peak energy changes and multiple reflections with different loading force state.

Research works on contamination transfers through cracked concrete walls

International Nuclear Information System (INIS)

Gelain, T.; Vendel, J.

2006-01-01

This study takes place within the framework of nuclear facilities containment assessment. The objectives are to determine gaseous and two-phase flow laws, aerosol deposition correlations into crack network, further to accidental situation (e.g. seism) and the real crack network characteristics considering the cracks as two infinite parallel plates. At first, we performed air flow experiments on three concrete walls (128 cm in width, 75 cm in height and 10 cm in thickness), cracked by shear stresses. Using 'aeraulic' crack network characteristics, the results are in good agreement with the Poiseuille law in laminar flow, but in the case of transition flow it has been necessary to determine a specific correlation for the friction factor. Then, we performed aerosol deposition experiments with one of the previous concrete walls to determine global aerosol deposition model in a crack network. Using these previous experiments and an experiment consisting in calculating the crack network volume by measuring transfer time, we could determine the real crack network characteristics in a good agreement with characteristics calculated by a structural mechanical code for our experimental configuration. (authors)

Pseudo-dynamic tests on masonry residential buildings seismically retrofitted by precast steel reinforced concrete walls

Science.gov (United States)

Li, Wenfeng; Wang, Tao; Chen, Xi; Zhong, Xiang; Pan, Peng

2017-07-01

A retrofitting technology using precast steel reinforced concrete (PSRC) panels is developed to improve the seismic performance of old masonry buildings. The PSRC panels are built up as an external PSRC wall system surrounding the existing masonry building. The PSRC walls are well connected to the existing masonry building, which provides enough confinement to effectively improve the ductility, strength, and stiffenss of old masonry structures. The PSRC panels are prefabricated in a factory, significantly reducing the situ work and associated construction time. To demonstrate the feasibility and mechanical effectivenss of the proposed retrofitting system, a full-scale five-story specimen was constructed. The retrofitting process was completed within five weeks with very limited indoor operation. The specimen was then tested in the lateral direction, which could potentially suffer sigifnicant damage in a large earthquake. The technical feasibility, construction workability, and seismic performance were thoroughly demonstrated by a full-scale specimen construction and pseudo-dynamic tests.

Research Status on Reinforcement Connection Form of Precast Concrete Shear Wall Structure

Science.gov (United States)

Zhang, Zhuangnan; Zhang, Yan

2018-03-01

With the rapid development of Chinese economy and the speeding up the process of urbanization, housing industrialization has been paid more and more attention. And the fabricated structure has been widely used in China. The key of precast concrete shear wall structure is the connection of precast components. The reinforcement connection can directly affect the entirety performance and seismic behavior of the structure. Different reinforcement connections have a great impact on the overall behavior of the structure. By studying the characteristics of the reinforcement connection forms used in the vertical connection and horizontal connection of precast concrete shear wall, it can provide reference for the research and development of the reinforcement connection forms in the future.

Application of Nonlinear Elastic Resonance Spectroscopy For Damage Detection In Concrete: An Interesting Story

Energy Technology Data Exchange (ETDEWEB)

Byers, Loren W. [Los Alamos National Laboratory; Ten Cate, James A. [Los Alamos National Laboratory; Johnson, Paul A. [Los Alamos National Laboratory

2012-06-28

Nonlinear resonance ultrasound spectroscopy experiments conducted on concrete cores, one chemically and mechanically damaged by alkali-silica reactivity, and one undamaged, show that this material displays highly nonlinear wave behavior, similar to many other damaged materials. They find that the damaged sample responds more nonlinearly, manifested by a larger resonant peak and modulus shift as a function of strain amplitude. The nonlinear response indicates that there is a hysteretic influence in the stress-strain equation of state. Further, as in some other materials, slow dynamics are present. The nonlinear response they observe in concrete is an extremely sensitive indicator of damage. Ultimately, nonlinear wave methods applied to concrete may be used to guide mixing, curing, or other production techniques, in order to develop materials with particular desired qualities such as enhanced strength or chemical resistance, and to be used for damage inspection.

Application Problems of Anchor Dowels in Reinforced Concrete Shear Wall and Frame Connections

OpenAIRE

Musa H. Arslan

2016-01-01

Strengthening of the existing seismically deficient reinforced concrete (RC) buildings is an important issue in earthquake prone regions. Addition of RC shear wall as infill or external walls into the structural system has been a commonly preferred strengthening technique since the Big Erzincan Earthquake occurred in Turkey, 1992. The newly added rigid infill walls act primarily as shear walls and relieve the non-ductile existing frames from being subjected to large shear demands providing th...

Seismic performance evaluation of an infilled rocking wall frame structure through quasi-static cyclic testing

Science.gov (United States)

Pan, Peng; Wu, Shoujun; Wang, Haishen; Nie, Xin

2018-04-01

Earthquake investigations have illustrated that even code-compliant reinforced concrete frames may suffer from soft-story mechanism. This damage mode results in poor ductility and limited energy dissipation. Continuous components offer alternatives that may avoid such failures. A novel infilled rocking wall frame system is proposed that takes advantage of continuous component and rocking characteristics. Previous studies have investigated similar systems that combine a reinforced concrete frame and a wall with rocking behavior used. However, a large-scale experimental study of a reinforced concrete frame combined with a rocking wall has not been reported. In this study, a seismic performance evaluation of the newly proposed infilled rocking wall frame structure was conducted through quasi-static cyclic testing. Critical joints were designed and verified. Numerical models were established and calibrated to estimate frame shear forces. The results evaluation demonstrate that an infilled rocking wall frame can effectively avoid soft-story mechanisms. Capacity and initial stiffness are greatly improved and self-centering behavior is achieved with the help of the infilled rocking wall. Drift distribution becomes more uniform with height. Concrete cracks and damage occurs in desired areas. The infilled rocking wall frame offers a promising approach to achieving seismic resilience.

Wireless and embedded carbon nanotube networks for damage detection in concrete structures

International Nuclear Information System (INIS)

Saafi, Mohamed

2009-01-01

Concrete structures undergo an uncontrollable damage process manifesting in the form of cracks due to the coupling of fatigue loading and environmental effects. In order to achieve long-term durability and performance, continuous health monitoring systems are needed to make critical decisions regarding operation, maintenance and repairs. Recent advances in nanostructured materials such as carbon nanotubes have opened the door for new smart and advanced sensing materials that could effectively be used in health monitoring of structures where wireless and real time sensing could provide information on damage development. In this paper, carbon nanotube networks were embedded into a cement matrix to develop an in situ wireless and embedded sensor for damage detection in concrete structures. By wirelessly measuring the change in the electrical resistance of the carbon nanotube networks, the progress of damage can be detected and monitored. As a proof of concept, wireless cement-carbon nanotube sensors were embedded into concrete beams and subjected to monotonic and cyclic loading to evaluate the effect of damage on their response. Experimental results showed that the wireless response of the embedded nanotube sensors changes due to the formation of cracks during loading. In addition, the nanotube sensors were able to detect the initiation of damage at an early stage of loading.

Wireless and embedded carbon nanotube networks for damage detection in concrete structures

Science.gov (United States)

Saafi, Mohamed

2009-09-01

Concrete structures undergo an uncontrollable damage process manifesting in the form of cracks due to the coupling of fatigue loading and environmental effects. In order to achieve long-term durability and performance, continuous health monitoring systems are needed to make critical decisions regarding operation, maintenance and repairs. Recent advances in nanostructured materials such as carbon nanotubes have opened the door for new smart and advanced sensing materials that could effectively be used in health monitoring of structures where wireless and real time sensing could provide information on damage development. In this paper, carbon nanotube networks were embedded into a cement matrix to develop an in situ wireless and embedded sensor for damage detection in concrete structures. By wirelessly measuring the change in the electrical resistance of the carbon nanotube networks, the progress of damage can be detected and monitored. As a proof of concept, wireless cement-carbon nanotube sensors were embedded into concrete beams and subjected to monotonic and cyclic loading to evaluate the effect of damage on their response. Experimental results showed that the wireless response of the embedded nanotube sensors changes due to the formation of cracks during loading. In addition, the nanotube sensors were able to detect the initiation of damage at an early stage of loading.

Electromagnetic Shielding Characteristics of Eco-Friendly Foamed Concrete Wall

Directory of Open Access Journals (Sweden)

Sung-Sil Cho

2017-01-01

Full Text Available The electromagnetic shielding characteristics according to the material composition of foamed concrete, which was manufactured to reduce environmental pollution and to economically apply it in actual building walls, were researched herein. Industrial by-products such as ladle furnace slag (LFS, gypsum, and blast furnace slag (BFS were added to manufacture foamed concrete with enhanced functionalities such as lightweight, heat insulation, and sound insulation. The electrical characteristics such as permittivity and loss tangent according to the foam and BFS content were calculated and measured. Free space measurement was used to measure the electromagnetic shielding characteristics of the actually manufactured foamed concrete. It was confirmed that electromagnetic signals were better blocked when the foam content was low and the BFS content was high in the measured frequency bands (1–8 GHz and that approximately 90% of the electromagnetic signals were blocked over 4 GHz.

Performance of Screen Grid Insulating Concrete Form Walls under Combined In-Plane Vertical and Lateral Loads

KAUST Repository

Abdel Mooty, Mohamed

2010-12-01

Insulating Concrete Forms (ICF) walls generally comprise two layers of Expanded Polystyrene (EPS), steel reinforcement is placed in the center between the two layers and concrete is poured to fill the gap between those two layers. ICF\\'s have many advantages over traditional methods of wall construction such as reduced construction time, noise reduction, strength enhancement, energy efficiency, and compatibility with any inside or outside surface finish. The focus of this study is the Screen Grid ICF wall system consisting of a number of beams and columns forming a concrete mesh. The performance of ICF wall systems under lateral loads simulating seismic effect is experimentally evaluated in this paper. This work addresses the effect of the different design parameters on the wall behavior under seismic simulated loads. This includes different steel reinforcement ratio, various reinforcement distribution, wall aspect ratios, different openings sizes for windows and doors, as well as different spacing of the grid elements of the screen grid wall. Ten full scale wall specimens were tested where the effects of the various parameters on wall behavior in terms of lateral load capacity, lateral displacement, and modes of failure are presented. The test results are stored to be used for further analysis and calibration of numerical models developed for this study. © (2011) Trans Tech Publications.

Experimental Study on the Hygrothermal Behavior of a Coated Sprayed Hemp Concrete Wall

Directory of Open Access Journals (Sweden)

Anthony Magueresse

2013-01-01

Full Text Available Hemp concrete is a sustainable lightweight concrete that became popular in the field of building construction because of its thermal and environmental properties. However; available experimental data on its hygrothermal behavior are rather scarce in the literature. This paper describes the design of a large-scale experiment developed to investigate the hygrothermal behavior of hemp concrete cast around a timber frame through a spraying process; and then coated with lime-based plaster. The equipment is composed of two climatic chambers surrounding the tested wall. The experiment consists of maintaining the indoor climate at constant values and applying incremental steps of temperature; relative humidity or vapor pressure in the outdoor chamber. Temperature and relative humidity of the room air and on various depths inside the wall are continuously registered during the experiments and evaporation phenomena are observed. The influence of the plaster on the hygrothermal behavior of hemp concrete is investigated. Moreover; a comparison of experimental temperatures with numerical results obtained from a purely conductive thermal model is proposed. Comparing the model with the measured data gave satisfactory agreement.

Impact of Thin-Walled Projectiles with Concrete Targets

Directory of Open Access Journals (Sweden)

Rayment E. Moxley

1995-01-01

Full Text Available An experimental program to determine the response of thin-walled steel projectiles to the impact with concrete targets was recently conducted. The projectiles were fired against 41-MPa concrete targets at an impact velocity of 290 m/s. This article contains an outline of the experimental program, an examination of the results of a typical test, and predictions of projectile deformation by classical shell theory and computational simulation. Classical shell analysis of the projectile indicated that the predicted impact loads would result in circumferential buckling. A computational simulation of a test was conducted with an impact/penetration model created by linking a rigid-body penetration trajectory code with a general-purpose finite element code. Scientific visualization of the resulting data revealed that circumferential buckling was induced by the impact conditions considered.

Concrete as secondary containment for interior wall embedded waste lines

International Nuclear Information System (INIS)

Porter, C.L.

1993-01-01

Throughout the Department of Energy (DOE) complex are numerous facilities that handle hazardous waste solutions. Secondary containment of tank systems and their ancillary piping is a major concern for existing facilities. The Idaho Division of Environmental Quality was petitioned in 1990 for an Equivalent Device determination regarding secondary containment of waste lines embedded in interior concrete walls. The petition was granted, however it expires in 1996. To address the secondary containment issue, additional studies were undertaken. One study verified the hypothesis that an interior wall pipe leak would follow the path of least resistance through the naturally occurring void found below a rigidly supported pipe and pass into an adjacent room where detection could occur, before any significant deterioration of the concrete takes place. Other tests demonstrated that with acidic waste solutions rebar and cold joints are not an accelerated path to the environment. The results from these latest studies confirm that the subject configuration meets all the requirements of secondary containment

Assessment of seismic design response factors of concrete wall buildings

Science.gov (United States)

Mwafy, Aman

2011-03-01

To verify the seismic design response factors of high-rise buildings, five reference structures, varying in height from 20- to 60-stories, were selected and designed according to modern design codes to represent a wide range of concrete wall structures. Verified fiber-based analytical models for inelastic simulation were developed, considering the geometric nonlinearity and material inelasticity of the structural members. The ground motion uncertainty was accounted for by employing 20 earthquake records representing two seismic scenarios, consistent with the latest understanding of the tectonic setting and seismicity of the selected reference region (UAE). A large number of Inelastic Pushover Analyses (IPAs) and Incremental Dynamic Collapse Analyses (IDCAs) were deployed for the reference structures to estimate the seismic design response factors. It is concluded that the factors adopted by the design code are adequately conservative. The results of this systematic assessment of seismic design response factors apply to a wide variety of contemporary concrete wall buildings with various characteristics.

Damage Detection in Railway Prestressed Concrete Sleepers using Acoustic Emission

Science.gov (United States)

Clark, A.; Kaewunruen, S.; Janeliukstis, R.; Papaelias, M.

2017-10-01

Prestressed concrete sleepers (or railroad ties) are safety-critical elements in railway tracks that distribute the wheel loads from the rails to the track support system. Over a period of time, the concrete sleepers age and deteriorate in addition to experiencing various types of static and dynamic loading conditions, which are attributable to train operations. In many cases, structural cracks can develop within the sleepers due to high intensity impact loads or due to poor track maintenance. Often, cracks of sleepers develop and present at the midspan due to excessive negative bending. These cracks can cause broken sleepers and sometimes called ‘center bound’ problem in railway lines. This paper is the world first to present an application of non-destructive acoustic emission technology for damage detection in railway concrete sleepers. It presents experimental investigations in order to detect center-bound cracks in railway prestressed concrete sleepers. Experimental laboratory testing involves three-point bending tests of four concrete sleepers. Three-point bending tests correspond to a real failure mode, when the loads are not transferred uniformly to the ballast support. It is observed that AE sensing provides an accurate means for detecting the location and magnitude of cracks in sleepers. Sensor location criticality is also highlighted in the paper to demonstrate the reliability-based damage detection of the sleepers.

The Vibration Based Fatigue Damage Assessment of Steel and Steel Fiber Reinforced Concrete (SFRC Composite Girder

Directory of Open Access Journals (Sweden)

Xu Chen

2015-01-01

Full Text Available The steel-concrete composite girder has been usually applied in the bridge and building structures, mostly consisting of concrete slab, steel girder, and shear connector. The current fatigue damage assessment for the composite girder is largely based on the strain values and concrete crack features, which is time consuming and not stable. Hence the vibration-based fatigue damage assessment has been considered in this study. In detail, a steel-steel fiber reinforced concrete (SFRC composite girder was tested. The steel fiber reinforced concrete is usually considered for dealing with the concrete cracks in engineering practice. The composite girder was 3.3m long and 0.45m high. The fatigue load and impact excitation were applied on the specimen sequentially. According to the test results, the concrete crack development and global stiffness degradation during the fatigue test were relatively slow due to the favourable performance of SFRC in tension. But on the other hand, the vibration features varied significantly during the fatigue damage development. Generally, it confirmed the feasibility of executing fatigue damage assessment of composite bridge based on vibration method.

Experimental evaluation of the prevention methods for the interface between masonry infill walls and concrete columns

Directory of Open Access Journals (Sweden)

A. P. Tramontin

Full Text Available Cracks that form at the interfaces between masonry structures are common uncontrolled occurrences in buildings. Numerous methods have been proposed by the construction industry to address this problem. Cracks continuously form in the joints between concrete columns and masonry infill walls. In this study, the most common methods for preventing these types of cracks were evaluated in laboratory experiments. Column masonry models were constructed using different types of joints between concrete columns and masonry infill walls, such as steel bars and steel mesh. The efficiency of each type of joint method was evaluated by performing direct tensile tests (pullout tests on the models and monitoring the evolution of the crack opening in the joint between the column and wall, as a function of load applied to the model. The results from this study indicate that the model composed of "electrowelded wire mesh without steel angles" is the best model for controlling cracking in the joints between concrete columns and masonry infill walls.

Axial Compression Behavior of a New Type of Prefabricated Concrete Sandwich Wall Panel

Science.gov (United States)

Qun, Xie; Shuai, Wang; Chun, Liu

2018-03-01

A novel type of prefabricated concrete sandwich wall panel which could be used as a load-bearing structural element in buildings has been presented in this paper. Compared with the traditional sandwich panels, there are several typical characteristics for this wall system, including core columns confined by spiral stirrup along the cross-section of panel with 600mm spacing, precast foamed concrete block between two structural layers as internal insulation part, and a three-dimensional (3D) steel wire skeleton in each layer which is composed of two vertical steel wire meshes connected by horizontally short steel bar. All steel segments in the panel are automatically prefabricated in factory and then are assembled to form steel system in site. In order to investigate the structural behavior of this wall panel, two full-scale panels have been experimentally studied under axial compressive load. The test results show that the wall panel presents good load-bearing capacity and integral stiffness without out-of-plane flexural failure. Compared to the panel with planar steel wire mesh in concrete layer, the panel with 3D steel wire skeleton presents higher strength and better rigidity even in the condition of same steel ratio in panels which verifies that the 3D steel skeleton could greatly enhance the structural behavior of sandwich panel.

Investigation into the behaviour of concrete anchored diaphragm walls under earthquake condition

International Nuclear Information System (INIS)

Saba, H. R.; Rahaii, A. R.

2003-01-01

Diaphragm walls are frequently used in civil Engineering projects. Considering the variety and important volume of consumed materials (concrete, anchors and soil), one of the important factors for design and construction of these walls, are their behaviour under different executive, and loading conditions. In this paper, various models of concrete diaphragms with different number of anchors and soil parameters under static and dynamic loading have been investigated using finite element method with nonlinear models. Results including the internal forces in diaphragm walls, variation of forces in the anchors, shape of the sliding surface and variation of pressure in soil are obtained and compared. An experimental tool with suitable measurement systems for determining the pressure and internal forces was designed and realised. Also with similitude and dimensional analyses, diaphragms with different number of anchors were built and set on the shaking table test and experimented under different accelograms. Finally results of nonlinear dynamic analysis were compared with experimental results

The moisture conditions of nuclear reactor concrete containment walls - an example for a BWR reactor

Energy Technology Data Exchange (ETDEWEB)

Nilsson, L.O.; Johansson, P. [Lund Institute of Technology, Laboratory of Building Materials, PO Box 118, 221 00 Lund (Sweden)

2006-07-01

A method is presented on how to quantify the moisture conditions of nuclear concrete containment walls. The method is based on first quantifying the boundary conditions at the outer and inner surfaces and then describing the moisture fixation and moisture transport within the concrete wall. The temperature and humidity conditions of the outdoor air and of the air close to the wall surfaces are monitored for a period of time and the vapour contents in the different points are compared. From the differences between the vapour contents the sources of moisture are identified and quantified. The previous and future climatic conditions are then predicted. An example is given for the conditions in the containment walls at Barsebaeck nuclear power plant, where moisture measurements have been performed in situ and on samples taken from the walls. (authors)

Preliminary Study on Evaluation of Impact Resistance Performance of Fiber Reinforced Concrete Walls

International Nuclear Information System (INIS)

Jin, Byeong Moo; Lee, Yun Seok; Kim, Young Jin; Jeon, Se Jin

2012-01-01

As the safety assessments of nuclear power plants for the hypothetical large civil aircraft crash should be made mandatory, studies on large aircraft-nuclear power plant impact analyses and assessments studies are actively in progress. For the safety assessment of nuclear power plants against large civil aircraft crash, it is practically impossible to conduct full-scale experiments. Therefore, analysis using general purpose numerical analysis program accompanied by scale model experiments and element experiments has been adopted for the safety assessment. The safety of nuclear power plants against large civil aircraft crash is able to be accomplished by enhancement of the impact resistance performance, such as increasing the wall thickness, increasing the strength of concrete and using the fiber reinforced concrete which is able to be acquired by relatively simple process of adding fibers to a concrete mix without significant change of design and construction. A research for the enhancement of impact resistance performance depending upon design parameters for fiber reinforced concrete, such as type of fibers and application rate, is in progress. In this study, before the safety assessment of nuclear power plants against large civil aircraft crash, we assess the impact resistance performance of concrete wall depending upon type of fibers and impact velocity of objects

Preliminary Study on Evaluation of Impact Resistance Performance of Fiber Reinforced Concrete Walls

Energy Technology Data Exchange (ETDEWEB)

Jin, Byeong Moo; Lee, Yun Seok; Kim, Young Jin [Daewoo E and C Co. Ltd., Suwon (Korea, Republic of); Jeon, Se Jin [Ajou University, Suwon (Korea, Republic of)

2012-05-15

As the safety assessments of nuclear power plants for the hypothetical large civil aircraft crash should be made mandatory, studies on large aircraft-nuclear power plant impact analyses and assessments studies are actively in progress. For the safety assessment of nuclear power plants against large civil aircraft crash, it is practically impossible to conduct full-scale experiments. Therefore, analysis using general purpose numerical analysis program accompanied by scale model experiments and element experiments has been adopted for the safety assessment. The safety of nuclear power plants against large civil aircraft crash is able to be accomplished by enhancement of the impact resistance performance, such as increasing the wall thickness, increasing the strength of concrete and using the fiber reinforced concrete which is able to be acquired by relatively simple process of adding fibers to a concrete mix without significant change of design and construction. A research for the enhancement of impact resistance performance depending upon design parameters for fiber reinforced concrete, such as type of fibers and application rate, is in progress. In this study, before the safety assessment of nuclear power plants against large civil aircraft crash, we assess the impact resistance performance of concrete wall depending upon type of fibers and impact velocity of objects

Hysteretic evaluation of seismic performance of normal and fiber reinforced concrete shear walls

International Nuclear Information System (INIS)

Choun, Young Sun; Hahm, Dae Gi

2012-01-01

The use of fibers in concrete or cement composites can enhance the performance of structural elements. Fibers have been used for a cement mixture to increase the toughness and tensile strength, and to improve the cracking and deformation characteristics. The addition of fibers into concrete can improve the ductility and increase the seismic resistance of concrete structures. The application of fibers to earthquake-resistant concrete structures has a major research topic. A recent study shows that an excellent seismic performance can be obtained in shear critical members constructed with high performance fiber reinforced cement composites. To increase the seismic performance of safety related concrete structures in nuclear power plants, fibers can be used. This study investigated the effect of fibers on the hysteretic behavior of a reinforced concrete (RC) shear wall by cyclic tests

Hysteretic evaluation of seismic performance of normal and fiber reinforced concrete shear walls

Energy Technology Data Exchange (ETDEWEB)

Choun, Young Sun; Hahm, Dae Gi [KAERI, Daejeon (Korea, Republic of)

2012-10-15

The use of fibers in concrete or cement composites can enhance the performance of structural elements. Fibers have been used for a cement mixture to increase the toughness and tensile strength, and to improve the cracking and deformation characteristics. The addition of fibers into concrete can improve the ductility and increase the seismic resistance of concrete structures. The application of fibers to earthquake-resistant concrete structures has a major research topic. A recent study shows that an excellent seismic performance can be obtained in shear critical members constructed with high performance fiber reinforced cement composites. To increase the seismic performance of safety related concrete structures in nuclear power plants, fibers can be used. This study investigated the effect of fibers on the hysteretic behavior of a reinforced concrete (RC) shear wall by cyclic tests.

Improving Thermal Insulation Properties for Prefabricated Wall Components Made Of Lightweight Aggregate Concrete with Open Structure

Science.gov (United States)

Abramski, Marcin

2017-10-01

Porous concrete is commonly used in civil engineering due to its good thermal insulation properties in comparison with normal concrete and high compression strength in comparison with other building materials. Reducing of the concrete density can be obviously obtained by using lightweight aggregate (e.g. pumice). The concrete density can be further minimized by using specially graded coarse aggregate and little-to-no fine aggregates. In this way a large number of air voids arise. The aggregate particles are coated by a cement paste and bonded together with it just in contact points. Such an extremely porous concrete, called ‘lightweight aggregate concrete with open structure’ (LAC), is used in some German plants to produce prefabricated wall components. They are used mainly in hall buildings, e.g. supermarkets. The need of improving thermal insulation properties was an inspiration for the prefabrication plant managers, engineers and a scientific staff of the Technical University of Kaiserslautern / Germany to realise an interesting project. Its aim was to reduce the heat transfer coefficient for the wall components. Three different wall structure types were designed and compared in full-scale laboratory tests with originally produced wall components in terms of load-carrying capacity and stiffness. The load was applied perpendicularly to the wall plane. As the components are not originally used for load-bearing walls, but for curtain walls only, the wind load is the main load for them. The wall components were tested in horizontal position and the load was applied vertically. Totally twelve wall components 8.00 × 2.00 × 0.25m (three for every series) were produced in the prefabrication plant and tested in the University of Kaiserslautern laboratory. The designed and tested components differed from each other in the amount of expanded polystyrene (EPS), which was placed in the plant inside the wall structure. The minimal amount of it was designed in the

Development of fusion first-wall radiation damage facilities

International Nuclear Information System (INIS)

McElroy, R.J.; Atkins, T.

1986-11-01

The report describes work performed on the development of fusion-reactor first-wall simulation facilities on the Variable Energy Cyclotron, at Harwell, United Kingdom. Two irradiation facilities have been constructed: i) a device for helium and hydrogen filling up to 1000 ppm for post-irradiation mechanical properties studies, and ii) a helium implantation and damage facility for simultaneous injection of helium and radiation damage into a specimen under stress. These facilities are now fully commissioned and are available for investigations of first-wall radiation damage and for intercorrelation of fission- and fusion -reactor materials behaviour. (U.K.)

Seismic damage assessment of reinforced concrete containment structures

International Nuclear Information System (INIS)

Cho, HoHyun; Koh, Hyun-Moo; Hyun, Chang-Hun; Kim, Moon-Soo; Shin, Hyun Mock

2003-01-01

This paper presents a procedure for assessing seismic damage of concrete containment structures using the nonlinear time-history numerical analysis. For this purpose, two kinds of damage index are introduced at finite element and structural levels. Nonlinear finite element analysis for the containment structure applies PSC shell elements using a layered approach leading to damage indices at finite element and structural levels, which are then used to assess the seismic damage of the containment structure. As an example of such seismic damage assessment, seismic damages of the containment structure of Wolsong I nuclear power plant in Korea are evaluated against 30 artificial earthquakes generated with a wide range of PGA according to US NRC regulatory guide 1.60. Structural responses and corresponding damage index according to the level of PGA and nonlinearity are investigated. It is also shown that the containment structure behaves elastically for earthquakes corresponding to or lower than DBE. (author)

Nonlinear seismic analysis of a thick-walled concrete canyon structure

International Nuclear Information System (INIS)

Winkel, B.V.; Wagenblast, G.R.

1989-01-01

Conventional linear seismic analyses of a thick-walled lightly reinforced concrete structure were found to grossly underestimate its seismic capacity. Reasonable estimates of the seismic capacity were obtained by performing approximate nonlinear spectrum analyses along with static collapse evaluations. A nonlinear time history analyses is planned as the final verification of seismic adequacy

Behavior of Equipment Support Beam Joint Directly Connected to A Steel-plate Concrete(SC) Wall

International Nuclear Information System (INIS)

Kim, K. S.; Kwon, K. J.

2008-01-01

To decrease the time for building nuclear power plants, a modular construction method, 'Steel-plate Concrete(SC)', has been investigated for over a decade. To construct a SC wall, a pair of steel plates are placed in parallel similar to a form-work in conventional reinforced concrete (RC) structures, and concrete is filled between the steel plates. Instead of removing the steel plates after the concrete has cured, the steel plates serve as components of the structural member. The exposed steel plate of SC structures serves as the base plate for the equipment support, and the headed studs welded to the steel plates are used as anchor bolts. Then, a support beam can be directly welded to the surface of the steel plate in any preferred position. In this study, we discuss the behavior and evaluation method of the equipment support joint directly connected to exposed steel plate of SC wall

Documentation for Calculations of Standard Fire Resistance of Slabs and Walls of Concrete with Expanded Clay Aggregate

DEFF Research Database (Denmark)

Hertz, Kristian Dahl

A number of full-scale tests are made in order to document calculation methods for fire-exposed slabs and walls derived during a previous project on fire exposed light-weight aggregate concrete constructions. The calculation methods are derived, and thus have a logical connection with the calcula......A number of full-scale tests are made in order to document calculation methods for fire-exposed slabs and walls derived during a previous project on fire exposed light-weight aggregate concrete constructions. The calculation methods are derived, and thus have a logical connection...... with the calculation methods used for other load cases. In addition the methods are shown to be valid for heavy concrete constructions by cooperation with tests for beams and columns, and a few slabs and walls. The two test series phase 1 and 2 of this report can therefore be seen as a necessary supplement to show...... that the methods are applicable for slabs and walls of light weight aggregate concrete. It is shown that the temperatures for standard fire exposed cross sections can be calculated, that the ultimate moment capacity can be calculated for slabs, and that the anchorage capacity and the shear tension capacity can...

Response and Damage Assessment of Reinforced Concrete Frames subject to Earthquakes

DEFF Research Database (Denmark)

Skjærbæk, Poul

When civil engineering structures made of reinforced concrete (RC) such as some types of apartment buildings, hospitals, office buildings, bridges etc. are subjected to sufficiently high dynamic loads it is well known that some kind of damage will occur in the structure. The damage introduced in ...

Heat Conductivity Resistance of Concrete Wall Panel by Water Flowing in Different Orientations of Internal PVC pipe

Science.gov (United States)

Umi, N. N.; Norazman, M. N.; Daud, N. M.; Yusof, M. A.; Yahya, M. A.; Othman, M.

2018-04-01

Green building technology and sustainability development is current focus in the world nowadays. In Malaysia and most tropical countries the maximum temperature recorded typically at 35°C. Air-conditioning system has become a necessity in occupied buildings, thereby increasing the cost of electric consumption. The aim of this study is to find out the solution in minimizing heat transfer from the external environment and intentions towards going green. In this study, the experimental work includes testing three types of concrete wall panels. The main heat intervention material in this research is 2 inch diameter Polyvinyl Chloride (PVC) pipe embedded at the center of the concrete wall panel, while the EPS foam beads were added to the cement content in the concrete mix forming the outer layer of the wall panel. Water from the rainwater harvesting system is regulated in the PVC pipe to intervene with the heat conductivity through the wall panel. Results from the experimental works show that the internal surface temperature of these heat resistance wall panels is to 3□C lower than control wall panel from plain interlocking bricks.

Evaluation of the Strength Variation of Normal and Lightweight Self-Compacting Concrete in Full Scale Walls

DEFF Research Database (Denmark)

Hosseinali, M.; Ranjbar, M. M.; Rezvani, S. M.

2011-01-01

-destructive testing. Self-compacting concrete (SCC) and lightweight self-compacting concrete (LWSCC) with different admixtures were tested and compared with normal concrete (NC). The results were also compared with results for standard cubic samples. The results demonstrate the effect of concrete type on the in situ......The strength of cast concrete along the height and length of large structural members might vary due to inadequate compaction, segregation, bleeding, head pressure, and material type. The distribution of strength within a series of full scale reinforced concrete walls was examined using non...

Acoustic emission of fire damaged fiber reinforced concrete

Science.gov (United States)

Mpalaskas, A. C.; Matikas, T. E.; Aggelis, D. G.

2016-04-01

The mechanical behavior of a fiber-reinforced concrete after extensive thermal damage is studied in this paper. Undulated steel fibers have been used for reinforcement. After being exposed to direct fire action at the temperature of 850°C, specimens were subjected to bending and compression in order to determine the loss of strength and stiffness in comparison to intact specimens and between the two types. The fire damage was assessed using nondestructive evaluation techniques, specifically ultrasonic pulse velocity (UPV) and acoustic emission (AE). Apart from the strong, well known, correlation of UPV to strength (both bending and compressive), AE parameters based mainly on the frequency and duration of the emitted signals after cracking events showed a similar or, in certain cases, better correlation with the mechanical parameters and temperature. This demonstrates the sensitivity of AE to the fracture incidents which eventually lead to failure of the material and it is encouraging for potential in-situ use of the technique, where it could provide indices with additional characterization capability concerning the mechanical performance of concrete after it subjected to fire.

Development of a Nondestructive Impulse Device and Damage Model for Unreinforced Concrete

Directory of Open Access Journals (Sweden)

Shane D. Boone

2012-01-01

Full Text Available Unconstrained compression waves were measured using a newly developed, nondestructive, short impulse excitation device developed for long-term structural health monitoring. The measurements, using this innovative device, were used to determine the variation in the first longitudinal modal frequency as a function of loading magnitude and loading cycles to failure of various concrete mixes. Longitudinal frequency and cumulative energy variations were found to be a function of concrete compressive strength. These results imply that higher-strength concrete more easily absorbs energy and restricts the growth of microcracks. Based on the results, a new damage model is proposed that was shown to correlate with measured values to within 7%. This proposed model was found to have a closer correlation than Miner’s hypothesis and damage index models from other reviewed research.

Proof-of-concept experimental study of damage detection of concrete piles using embedded piezoceramic transducers

International Nuclear Information System (INIS)

Wang, R L; Gu, H; Song, G; Mo, Y L

2013-01-01

This paper presents a proof-of-concept experimental study of an innovative active-sensing approach for damage detection of concrete piles by using embedded piezoceramic transducers. In the proposed active-sensing approach, one piezoceramic transducer is used as an actuator to generate a stress wave to propagate through the concrete pile and the other distributed piezoceramic transducers are used as sensors to detect the wave response. Cracks or damage inside the concrete structure act as stress relief in the wave propagation path. The amplitude of the wave and the transmission energy will decrease due to the existence of cracks or damage. Experiments were performed on two bored piles instrumented with embedded piezoceramic transducers. The experimental results demonstrate the effectiveness of the proposed approach for pile damage detection. (fast track communication)

Potentialities of infrared thermography to assess damage in bonding between concrete and GFRP

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M. M. CALDEIRA

Full Text Available This paper demonstrates the application of the active infrared thermography to detect damage in bonding between concrete and glass fiber reinforced polymer (GFRP. Specimens of concrete and mortar with GFRP externally bonded were prepared and at their interfaces were inserted polystyrene discs to simulate damages. The samples were divided into two groups. In group 1, one sample was correctly bonded by a GFRP plate to the concrete, but in the other three were inserted polystyrene discs which had different diameters to simulate damages in bonding. In group 2, all of the samples contained identical polystyrene discs at their interfaces, but the total thickness of each specimen was different, because the objective was to evaluate the ability of the camera to capture the simulated damage in depth. The experimental procedure was divided into two stages. In the first stage, four types of heating were used to heat samples of group 1: incandescent lamp, kiln, blended lamp and fan heater. Thus, it was possible to detect the damage and to observe its format and length. It was noticed that the infrared images are different depending on the heat source incident on the specimen. Therefore, group 2 was tested only for the more efficient heating (incandescent lamp. In the second stage, the infrared equipment was tested. Some of the parameters that must be inserted in the camera were varied in order to understand their influence on image formation. The results show the effectiveness of infrared thermography to assess adherence in GFRP/concrete interface. In the present work, the best results were obtained when the image is captured towards GFRP/concrete and using incandescent lamp. It was observed that the image and measured temperature suffer significant distortion when a false value was inserted for the parameter emissivity.

Load-carrying capacity of lightly reinforced, prefabricated walls of lightweight aggregate concrete with open structure

DEFF Research Database (Denmark)

Goltermann, Per

2009-01-01

The paper presents and evaluates the results of a coordinated testing of prefabricated, lightly reinforced walls of lightweight aggregate concrete with open structure. The coordinated testing covers all wall productions in Denmark and will therefore provide a representative assessment...

High-Temperature Performance and Multiscale Damage Mechanisms of Hollow Cellulose Fiber-Reinforced Concrete

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Liping Guo

2016-01-01

Full Text Available Spalling resistance properties and their damage mechanisms under high temperatures are studied in hollow cellulose fiber-reinforced concrete (CFRC used in tunnel structures. Measurements of mass loss, relative dynamic elastic modulus, compressive strength, and splitting tensile strength of CFRC held under high temperatures (300, 600, 800, and 1050°C for periods of 2.5, 4, and 5.5 h were carried out. The damage mechanism was analyzed using scanning electron microscopy, mercury intrusion porosimetry, thermal analysis, and X-ray diffraction phase analysis. The results demonstrate that cellulose fiber can reduce the performance loss of concrete at high temperatures; the effect of holding time on the performance is more noticeable below 600°C. After exposure to high temperatures, the performance of ordinary concrete deteriorates faster and spalls at 700–800°C; in contrast, cellulose fiber melts at a higher temperature, leaving a series of channels in the matrix that facilitate the release of the steam pressure inside the CFRC. Hollow cellulose fibers can thereby slow the damage caused by internal stress and improve the spalling resistance of concrete under high temperatures.

Rheological-dynamical continuum damage model for concrete under uniaxial compression and its experimental verification

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Milašinović Dragan D.

2015-01-01

Full Text Available A new analytical model for the prediction of concrete response under uniaxial compression and its experimental verification is presented in this paper. The proposed approach, referred to as the rheological-dynamical continuum damage model, combines rheological-dynamical analogy and damage mechanics. Within the framework of this approach the key continuum parameters such as the creep coefficient, Poisson’s ratio and damage variable are functionally related. The critical values of the creep coefficient and damage variable under peak stress are used to describe the failure mode of the concrete cylinder. The ultimate strain is determined in the post-peak regime only, using the secant stress-strain relation from damage mechanics. The post-peak branch is used for the energy analysis. Experimental data for five concrete compositions were obtained during the examination presented herein. The principal difference between compressive failure and tensile fracture is that there is a residual stress in the specimens, which is a consequence of uniformly accelerated motion of load during the examination of compressive strength. The critical interpenetration displacements and crushing energy are obtained theoretically based on the concept of global failure analysis. [Projekat Ministarstva nauke Republike Srbije, br. ON 174027: Computational Mechanics in Structural Engineering i br. TR 36017: Utilization of by-products and recycled waste materials in concrete composites for sustainable construction development in Serbia: Investigation and environmental assessment of possible applications

A preliminary study on the local impact behavior of Steel-plate Concrete walls

International Nuclear Information System (INIS)

Kim, Kap-sun; Moon, Il-hwan; Choi, Hyung-jin; Nam, Deok-woo

2017-01-01

International regulations for nuclear power plants strictly prescribe the design requirements for local impact loads, such as aircraft engine impact, and internal and external missile impact. However, the local impact characteristics of Steel-plate Concrete (SC) walls are not easy to evaluate precisely because the dynamic impact behavior of SC walls which include external steel plate, internal concrete, tie-bars, and studs, is so complex. In this study, dynamic impact characteristics of SC walls subjected to local missile impact load are investigated via actual high-speed impact test and numerical simulation. Three velocity checkout tests and four SC wall tests were performed at the Energetic Materials Research and Testing Center (EMRTC) site in the USA. Initial and residual velocity of the missile, strain and acceleration of the back plate, local failure mode (penetration, bulging, splitting and perforation) and deformation size, etc. were measured to study the local behavior of the specimen using high speed cameras and various other instrumentation devices. In addition, a more advanced and applicable numerical simulation method using the finite element (FE) method is proposed and verified by the experimental results. Finally, the experimental results are compared with the local failure evaluation formula for SC walls recently proposed, and future research directions for the development of a refined design method for SC walls are reviewed.

Effects of the air–steam mixture on the permeability of damaged concrete

Energy Technology Data Exchange (ETDEWEB)

Medjigbodo, Sonagnon [LUNAM Université, Institut de Recherche en Génie Civil et Mécanique (GeM UMR CNRS 6183), Centrale Nantes, 1 rue de la Noe, BP 92101, F-44321 CEDEX 3 Nantes (France); Darquennes, Aveline [LMT/ENS Cachan/CNRS UMR 8535/UPMC/PRES Université Sud Paris, Cachan (France); Aubernon, Corentin [LUNAM Université, Institut de Recherche en Génie Civil et Mécanique (GeM UMR CNRS 6183), Centrale Nantes, 1 rue de la Noe, BP 92101, F-44321 CEDEX 3 Nantes (France); Khelidj, Abdelhafid [LUNAM Université, Institut de Recherche en Génie Civil et Mécanique (GeM UMR CNRS 6183), IUT de Saint Nazaire, 58 rue Michel Ange, BP 420 Heinlex, F-44600 Saint-Nazaire (France); Loukili, Ahmed, E-mail: ahmed.loukili@ec-nantes.fr [LUNAM Université, Institut de Recherche en Génie Civil et Mécanique (GeM UMR CNRS 6183), Centrale Nantes, 1 rue de la Noe, BP 92101, F-44321 CEDEX 3 Nantes (France)

2013-12-15

Massive concrete structures such as the containments of nuclear power plant must maintain their tightness at any circumstances to prevent the escape of radioactive fission products into the environment. In the event of an accident like a Loss of Coolant Accident (LOCA), the concrete wall is submitted to both hydric and mechanical loadings. A new experimental device reproducing these extreme conditions (water vapor transfer, 140 °C and 5 bars) is developed in the GeM Laboratory to determine the effect of the saturation degree, the mechanical loading and the flowing fluid type on the concrete transfer properties. The experimental tests show that the previous parameters significantly affect the concrete permeability and the gas leakage rate. Their evolution as a function of the mechanical loading is characterized by two phases that are directly related to concrete microstructure and crack development.

Distribution of residual long-lived radioactivity in the inner concrete walls of a compact medical cyclotron vault room.

Science.gov (United States)

Fujibuchi, Toshioh; Nohtomi, Akihiro; Baba, Shingo; Sasaki, Masayuki; Komiya, Isao; Umedzu, Yoshiyuki; Honda, Hiroshi

2015-01-01

Compact medical cyclotrons have been set up to generate the nuclides necessary for positron emission tomography. In accelerator facilities, neutrons activate the concrete used to construct the vault room; this activation increases with the use of an accelerator. The activation causes a substantial radioactive waste management problem when facilities are decommissioned. In the present study, several concrete cores from the walls, ceiling and floor of a compact medical cyclotron vault room were samples 2 years after the termination of operations, and the radioactivity concentrations of radionuclides were estimated. Cylindrical concrete cores 5 cm in diameter and 10 cm in length were bored from the concrete wall, ceiling and floor. Core boring was performed at 18 points. The gamma-ray spectrum of each sample was measured using a high-purity germanium detector. The degree of activation of the concrete in the cyclotron vault room was analyzed, and the range and tendency toward activation in the vault room were examined. (60)Co and (152)Eu were identified by gamma-ray spectrometry of the concrete samples. (152)Eu and (60)Co are produced principally from the stable isotopes of europium and cobalt by neutron capture reactions. The radioactivity concentration did not vary much between the surface of the concrete and at a depth of 10 cm. Although the radioactivity concentration near the target was higher than the clearance level for radioactive waste indicated in IAEA RS-G-1.7, the mean radioactivity concentration in the walls and floor was lower than the clearance level. The radioactivity concentration of the inner concrete wall of the medical cyclotron vault room was not uniform. The areas exceeding the clearance level were in the vicinity of the target, but most of the building did not exceed the clearance levels.

A gradient enhanced plasticity-damage microplane model for concrete

Science.gov (United States)

Zreid, Imadeddin; Kaliske, Michael

2018-03-01

Computational modeling of concrete poses two main types of challenges. The first is the mathematical description of local response for such a heterogeneous material under all stress states, and the second is the stability and efficiency of the numerical implementation in finite element codes. The paper at hand presents a comprehensive approach addressing both issues. Adopting the microplane theory, a combined plasticity-damage model is formulated and regularized by an implicit gradient enhancement. The plasticity part introduces a new microplane smooth 3-surface cap yield function, which provides a stable numerical solution within an implicit finite element algorithm. The damage part utilizes a split, which can describe the transition of loading between tension and compression. Regularization of the model by the implicit gradient approach eliminates the mesh sensitivity and numerical instabilities. Identification methods for model parameters are proposed and several numerical examples of plain and reinforced concrete are carried out for illustration.

Maintenance and Durability of the Concrete External Layer of Curtain Walls in Prefabricated Technological Poznan Large Panel System

Science.gov (United States)

Jasiczak, Józef; Girus, Krzysztof

2017-10-01

The issue of usability and durability of large-panel building constructed several decades ago is a subject of an in-depth analysis of many domestic and foreign investments. When considering the durability of specific large-panel system, one should consider, among others, the process of making external walls. The long-term and direct impact of weather conditions on the external layer of curtain walls is significant for the durability of large-panel buildings. For the needs of the presented paper, in 2016, the survey of cracks and a series of other tests of large-panel façade, residential building constructed in 1986, in Poland, in the PLP process system - Rataje was executed. Several hundred large-size, triple-layer curtain-wall slab with a 6-cm, concrete exterior cladding layer anchored using pins and hangers with the load-bearing layer, a 9-cm insulation layer made of mineral wool, and a 21-cm structural layer were surveyed. Significant deviations in thicknesses of particular wall layers were proven. Other significant damages and defects of external layers were found. At the second stage, many tests, both nondestructive and destructive, were conducted. They involved determining mechanical properties of an external layer. The concrete thickness was measured using with a type N Schmidt sclerometer and core samples were taken from this layer in order to mark concrete’s compressive strength. The range of carbonation (by phenolphthalein method) and the actual location and condition of reinforcement were estimated using a ferromagnetic device to determine the condition of the external layer. The diagnosis conducted in such a manner was the verification of necessary repair of the walls and their thermal efficiency improvement while ensuring safe conditions of their operation and modern functional and utility requirements. It should be also emphasized that the method of diagnosing the external walls presented in this paper may be popularized when evaluating such

Experimental studies on local damage of reinforced concrete structures by the impact of deformable missiles-Part 1

International Nuclear Information System (INIS)

Muto, K.; Tachikawa, H.; Sugano, T.; Tsubota, H.; Kobayshi, H.; Kasai, Y.; Koshika, N.; Tsujimoto, T.

1989-01-01

Structural damage induced by an accidental aircraft crash into a reinforced concrete structure includes local damage caused by the engine, the rigid portion of the aircraft, and the global elasto-plastic structural response caused by the entire aircraft. Local damage consists of spalling of concrete from the front face of the target together with missile penetration into the target, scabbing of concrete from the rear face of the target and perforation of the missile through the target. The engine is a soft missile that deforms during impact. An experimental research program has been planned and executed to establish a rational evaluation method of the local damage by the deformable engine missiles

Experimental study of the leakage rate through cracked reinforced concrete wall elements for defining the functional failure criteria of containment buildings

International Nuclear Information System (INIS)

Choun, Young Sun; Cho, Nam So

2004-01-01

Containment buildings in nuclear power plants should maintain their structural safety as well as their functional integrity during an operation period. To maintain the functional integrity, the wall and dome of the containment buildings have to maintain their air tightness under extreme loading conditions such as earthquakes, missile impact, and severe accidents. For evaluating the functional failure of containments, it is important to predict the leak amount through cracked concrete walls. The leakage through concrete cracks has been studied since 1972. Buss examined the flow rate of air through a pre-existing crack in a slab under air pressure. Rizkalla el al. initiated an experimental study for the leakage of prestressed concrete building segments under uniaxial and biaxial loadings to simulate the loading condition of containment buildings under an internal pressure. Recently, Salmon el al. initiated an experimental program for determining the leak rates in typical reinforced concrete shear walls subjected to beyond design basis earthquakes. This study investigates the cracking behavior of reinforced concrete containment wall elements under a uniaxial tension and addresses the outline of the leakage test for unlined containment wall elements

Evaluation and considerations about fundamental periods of damaged reinforced concrete buildings

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R. Ditommaso

2013-07-01

Full Text Available The aim of this paper is an empirical estimation of the fundamental period of reinforced concrete buildings and its variation due to structural and non-structural damage. The 2009 L'Aquila earthquake has highlighted the mismatch between experimental data and code provisions value not only for undamaged buildings but also for the damaged ones. The 6 April 2009 L'Aquila earthquake provided the first opportunity in Italy to estimate the fundamental period of reinforced concrete (RC buildings after a strong seismic sequence. A total of 68 buildings with different characteristics, such as age, height and damage level, have been investigated by performing ambient vibration measurements that provided their fundamental translational period. Four different damage levels were considered according with the definitions by EMS 98 (European Macroseismic Scale, trying to regroup the estimated fundamental periods versus building heights according to damage. The fundamental period of RC buildings estimated for low damage level is equal to the previous relationship obtained in Italy and Europe for undamaged buildings, well below code provisions. When damage levels are higher, the fundamental periods increase, but again with values much lower than those provided by codes. Finally, the authors suggest a possible update of the code formula for the simplified estimation of the fundamental period of vibration for existing RC buildings, taking into account also the inelastic behaviour.

Experimental investigation of the relation between damage at the concrete-steel interface and initiation of reinforcement corrosion in plain and fibre reinforced concrete

DEFF Research Database (Denmark)

Michel, Alexander; Solgaard, Anders Ole Stubbe; Pease, Bradley Justin

2013-01-01

Cracks in covering concrete are known to hasten initiation of steel corrosion in reinforced concrete structures. To minimise the impact of cracks on the deterioration of reinforced concrete structures, current approaches in (inter)national design codes often limit the concrete surface crack width....... Recent investigations however, indicate that the concrete-reinforcement interfacial condition is a more fundamental criterion related to reinforcement corrosion. This work investigates the relation between macroscopic damage at the concrete-steel interface and corrosion initiation of reinforcement...... embedded in plain and fibre reinforced concrete. Comparisons of experimental and numerical results indicate a strong correlation between corrosion initiation and interfacial condition....

AUTOMATIC THICKNESS AND VOLUME ESTIMATION OF SPRAYED CONCRETE ON ANCHORED RETAINING WALLS FROM TERRESTRIAL LIDAR DATA

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J. Martínez-Sánchez

2016-06-01

Full Text Available When ground conditions are weak, particularly in free formed tunnel linings or retaining walls, sprayed concrete can be applied on the exposed surfaces immediately after excavation for shotcreting rock outcrops. In these situations, shotcrete is normally applied conjointly with rock bolts and mesh, thereby supporting the loose material that causes many of the small ground falls. On the other hand, contractors want to determine the thickness and volume of sprayed concrete for both technical and economic reasons: to guarantee their structural strength but also, to not deliver excess material that they will not be paid for. In this paper, we first introduce a terrestrial LiDAR-based method for the automatic detection of rock bolts, as typically used in anchored retaining walls. These ground support elements are segmented based on their geometry and they will serve as control points for the co-registration of two successive scans, before and after shotcreting. Then we compare both point clouds to estimate the sprayed concrete thickness and the expending volume on the wall. This novel methodology is demonstrated on repeated scan data from a retaining wall in the city of Vigo (Spain, resulting in a rock bolts detection rate of 91%, that permits to obtain a detailed information of the thickness and calculate a total volume of 3597 litres of concrete. These results have verified the effectiveness of the developed approach by increasing productivity and improving previous empirical proposals for real time thickness estimation.

Automatic Thickness and Volume Estimation of Sprayed Concrete on Anchored Retaining Walls from Terrestrial LIDAR Data

Science.gov (United States)

Martínez-Sánchez, J.; Puente, I.; GonzálezJorge, H.; Riveiro, B.; Arias, P.

2016-06-01

When ground conditions are weak, particularly in free formed tunnel linings or retaining walls, sprayed concrete can be applied on the exposed surfaces immediately after excavation for shotcreting rock outcrops. In these situations, shotcrete is normally applied conjointly with rock bolts and mesh, thereby supporting the loose material that causes many of the small ground falls. On the other hand, contractors want to determine the thickness and volume of sprayed concrete for both technical and economic reasons: to guarantee their structural strength but also, to not deliver excess material that they will not be paid for. In this paper, we first introduce a terrestrial LiDAR-based method for the automatic detection of rock bolts, as typically used in anchored retaining walls. These ground support elements are segmented based on their geometry and they will serve as control points for the co-registration of two successive scans, before and after shotcreting. Then we compare both point clouds to estimate the sprayed concrete thickness and the expending volume on the wall. This novel methodology is demonstrated on repeated scan data from a retaining wall in the city of Vigo (Spain), resulting in a rock bolts detection rate of 91%, that permits to obtain a detailed information of the thickness and calculate a total volume of 3597 litres of concrete. These results have verified the effectiveness of the developed approach by increasing productivity and improving previous empirical proposals for real time thickness estimation.

Damage Evaluation of Concrete Column under Impact Load Using a Piezoelectric-Based EMI Technique.

Science.gov (United States)

Fan, Shuli; Zhao, Shaoyu; Qi, Baoxin; Kong, Qingzhao

2018-05-17

One of the major causes of damage to column-supported concrete structures, such as bridges and highways, are collisions from moving vehicles, such as cars and ships. It is essential to quantify the collision damage of the column so that appropriate actions can be taken to prevent catastrophic events. A widely used method to assess structural damage is through the root-mean-square deviation (RMSD) damage index established by the collected data; however, the RMSD index does not truly provide quantitative information about the structure. Conversely, the damage volume ratio that can only be obtained via simulation provides better detail about the level of damage in a structure. Furthermore, as simulation can also provide the RMSD index relating to that particular damage volume ratio, the empirically obtained RMSD index can thus be related to the structural damage degree through comparison of the empirically obtained RMSD index to numerically-obtained RMSD. Thus, this paper presents a novel method in which the impact-induced damage to a structure is simulated in order to obtain the relationship between the damage volume ratio to the RMSD index, and the relationship can be used to predict the true damage degree by comparison to the empirical RMSD index. In this paper, the collision damage of a bridge column by moving vehicles was simulated by using a concrete beam model subjected to continuous impact loadings by a freefalling steel ball. The variation in admittance signals measured by the surface attached lead zirconate titanate (PZT) patches was used to establish the RMSD index. The results demonstrate that the RMSD index and the damage ratio of concrete have a linear relationship for the particular simulation model.

Modeling of Cyclic Strength for the Asphalt Concrete Considering Damage Accumulation

Directory of Open Access Journals (Sweden)

Alibai Iskakbayev

2017-12-01

Full Text Available The expression is obtained for determination of cyclic tensile strength for asphalt concrete, which considers damage accumulation and history of loading, using the long-term strength curve for asphalt concrete obtained according to the test results of more than 110 samples to failure at stresses from 0.05 to 0.31 MPa and by introduction of damage kernel in this paper. Cyclic strength depends on the stress, parameters of long-term strength, frequency of loading, durations of loading and relax periods, and ratio of loading period to the long-term strength. Evaluation of accuracy for the obtained expression for the cyclic strength has been performed by comparison with the results of a series for experimental tests of asphalt concrete samples at a temperature of 22 °С and cyclic loading conditions. The stress is 0.31 MPa, and the durations of loading and relax periods are 5 and 60 s, respectively. Calculations performed with the obtained expressions at real road conditions (the stress is 0.31 MPa, and the durations of loading and relax periods are 0.1 and 9.9 s respectively showed the possibility of its use for the prediction of fatigue (multicyclic strength of an asphalt concrete pavement for a highway.

Damage assessment for seismic response of recycled concrete filled steel tube columns

Science.gov (United States)

Huang, Yijie; Xiao, Jianzhuang; Shen, Luming

2016-09-01

A model for evaluating structural damage of recycled aggregate concrete filled steel tube (RCFST) columns under seismic effects is proposed in this paper. The proposed model takes the lateral deformation and the effect of repeated cyclic loading into account. Available test results were collected and utilized to calibrate the parameters of the proposed model. A seismic test for six RCFST columns was also performed to validate the proposed damage assessment model. The main test parameters were the recycled coarse aggregate (RCA) replacement percentage and the bond-slip property. The test results indicated that the seismic performance of the RCFST member depends on the RCA contents and their damage index increases as the RCA replacement percentage increases. It is also indicated that the damage degree of RCFST changes with the variation of the RCA replacement percentage. Finally, comparisons between the RCA contents, lateral deformation ratio and damage degree were implemented. It is suggested that an improvement procedure should be implemented in order to compensate for the performance difference between the RCFST and normal concrete filled steel tubes (CFST).

Numerical investigation of the leakage behaviour of reinforced concrete walls

International Nuclear Information System (INIS)

Christoph Niklasch; Laurent Coudert; Gregory Heinfling; Chantal Hervouet; Benoit Masson; Nico Herrmann; Lothar Stempniewski

2005-01-01

Full text of publication follows: For the verification of nuclear power plant safety, the leakage behaviour of the containment walls is of decisive importance. Extreme temperatures well over the water boiling temperature accompanied by high internal pressures can occur during an severe accident. In case of cracks through the entire thickness of the containment wall, an air-steam-water mixture may be released. In order to improve the knowledge of the leakage behaviour through cracks during such abnormal occurrences an experimental setup was developed at IfMB and several tests with different parameters were performed. The details of the experimental facility and the performed tests will be described in a separate paper. To improve the understanding of the behaviour of the tested wall elements during the tests numerical simulations of the performed leakage experiments are necessary. Reliable numerical tools provide a basis for the transfer of the leakage behaviour from the tested specimens to the behaviour of whole containment structures. To address the task of developing tools for the numerical simulation of the leakage behaviour of reinforced containment structures, EDF and IfMB decided to cooperate. During this cooperation two different numerical approaches had been made basing on existing tools and models of EDF and IfMB. In the following sections a short overview about the two different models will be given. For the numerical investigation of the leakage phenomena IfMB used the commercial Finite-Element- Program ADINA with ADINA's capability to solve coupled fluid-structure-interaction (FSI) problems. For the investigation of the moving of the specimen and the change of the crack profiles during the tests, it is important to take into account the heating of the specimen by the fluid flowing through the cracks. This is done by an iterative calculation of the fluid model and the structural model of the specimen. The thermo-dynamic boundary conditions representing

Long-Term Bending Creep Behavior of Thin-Walled CFRP Tendon Pretensioned Spun Concrete Poles

Directory of Open Access Journals (Sweden)

Giovanni P. Terrasi

2014-07-01

Full Text Available This paper discusses the long-term behavior of a series of highly-loaded, spun concrete pole specimens prestressed with carbon fiber-reinforced polymer (CFRP tendons, which were subjected to outdoor four-point bending creep tests since 1996 in the frame of collaboration with the Swiss precast concrete producer, SACAC (Società Anonima Cementi Armati Centrifugati. The 2 m span cylindrical beams studied are models for lighting poles produced for the last 10 years and sold on the European market. Five thin-walled pole specimens were investigated (diameter: 100 mm; wall-thickness: 25–27 mm. All specimens were produced in a pretensioning and spinning technique and were prestressed by pultruded CFRP tendons. Initially, two reference pole specimens were tested in quasi-static four-point bending to determine the short-term failure moment and to model the short-term flexural behavior. Then, three pole specimens were loaded to different bending creep moments: while the lowest loaded specimen was initially uncracked, the second specimen was loaded with 50% of the short-term bending failure moment and exhibited cracking immediately after load introduction. The highest loaded pole specimen sustained a bending moment of 72% of the short-term bending failure moment for 16.5 years before failing in July 2013, due to the bond failure of the tendons, which led to local crushing of the high-performance spun concrete (HPSC. Besides this, long-term monitoring of the creep tests has shown a limited time- and temperature-dependent increase of the deflections over the years, mainly due to the creep of the concrete. A concrete creep-based model allowed for the calculation of the long-term bending curvatures with reasonable accuracy. Furthermore, the pole specimens showed crack patterns that were stable over time and minimal slippage of the tendons with respect to the pole’s end-faces for the two lower load levels. The latter proves the successful and durable

Contribution to the numerical study of concrete behaviour and of reinforced concrete structures submitted to coupled thermal and mechanical solicitations: a damageable thermo-elasto-plastic approach

International Nuclear Information System (INIS)

Nechnech, W.

2000-12-01

The aim of this research is the development of an Finite Element model for the analysis of reinforced concrete structures under thermal, mechanical loadings or any combination of them. An available synthesis of results on the concrete behavior under thermal solicitation is exposed. The different behavior of concrete that can be founded notably in thermo-mechanical analysis (Damage, unilateral phenomenon, thermo-mechanical interaction,...) are underlined. The various families of modeling are analyzed thereafter while underlining the important aspects of the behavior that each one can re-transcribe. A new thermo-plastic damage model for plain concrete subjected to combined thermal and cyclic loading is developed using the concept of plastic-work-hardening and stiffness degradation in continuum damage mechanics. Two damage variables are used: the first one for mechanical action and the second one for thermal action. Further, thermo-mechanical interaction strains have been introduced to describe the influence of mechanical loading on the physical process of thermal expansion of concrete. The constitutive relations for elastoplastic responses are decoupled from the degradation damage responses by using the effective stress concept. This method provides advantages in the numerical implementation. A simple and thermodynamically consistent scalar degradation model is introduced to simulate the effect of damage on elastic stiffness and its recovery during crack opening and closing. Efficient computational algorithms for the proposed model are subsequently explored and performance of this model is demonstrated with numerical examples. (author)

Earthquake Resilient Bridge Columns Utilizing Damage Resistant Hybrid Fiber Reinforced Concrete

OpenAIRE

Trono, William Dean

2014-01-01

Modern reinforced concrete bridges are designed to avoid collapse and to prevent loss of life during earthquakes. To meet these objectives, bridge columns are typically detailed to form ductile plastic hinges when large displacements occur. California seismic design criteria acknowledges that damage such as concrete cover spalling and reinforcing bar yielding may occur in columns during a design-level earthquake. The seismic resilience of bridge columns can be improved through the use of a da...

Experimental Study on the Seismic Performance of Recycled Concrete Brick Walls Embedded with Vertical Reinforcement.

Science.gov (United States)

Cao, Wanlin; Zhang, Yongbo; Dong, Hongying; Zhou, Zhongyi; Qiao, Qiyun

2014-08-19

Recycled concrete brick (RCB) is manufactured by recycled aggregate processed from discarded concrete blocks arising from the demolishing of existing buildings. This paper presents research on the seismic performance of RCB masonry walls to assess the applicability of RCB for use in rural low-rise constructions. The seismic performance of a masonry wall is closely related to the vertical load applied to the wall. Thus, the compressive performance of RCB masonry was investigated firstly by constructing and testing eighteen RCB masonry compressive specimens with different mortar strengths. The load-bearing capacity, deformation and failure characteristic were analyzed, as well. Then, a quasi-static test was carried out to study the seismic behavior of RCB walls by eight RCB masonry walls subjected to an axial compressive load and a reversed cyclic lateral load. Based on the test results, equations for predicting the compressive strength of RCB masonry and the lateral ultimate strength of an RCB masonry wall were proposed. Experimental values were found to be in good agreement with the predicted values. Meanwhile, finite element analysis (FEA) and parametric analysis of the RCB walls were carried out using ABAQUS software. The elastic-plastic deformation characteristics and the lateral load-displacement relations were studied.

Experimental Study on the Seismic Performance of Recycled Concrete Brick Walls Embedded with Vertical Reinforcement

Directory of Open Access Journals (Sweden)

Wanlin Cao

2014-08-01

Full Text Available Recycled concrete brick (RCB is manufactured by recycled aggregate processed from discarded concrete blocks arising from the demolishing of existing buildings. This paper presents research on the seismic performance of RCB masonry walls to assess the applicability of RCB for use in rural low-rise constructions. The seismic performance of a masonry wall is closely related to the vertical load applied to the wall. Thus, the compressive performance of RCB masonry was investigated firstly by constructing and testing eighteen RCB masonry compressive specimens with different mortar strengths. The load-bearing capacity, deformation and failure characteristic were analyzed, as well. Then, a quasi-static test was carried out to study the seismic behavior of RCB walls by eight RCB masonry walls subjected to an axial compressive load and a reversed cyclic lateral load. Based on the test results, equations for predicting the compressive strength of RCB masonry and the lateral ultimate strength of an RCB masonry wall were proposed. Experimental values were found to be in good agreement with the predicted values. Meanwhile, finite element analysis (FEA and parametric analysis of the RCB walls were carried out using ABAQUS software. The elastic-plastic deformation characteristics and the lateral load-displacement relations were studied.

Experimental Study on the Seismic Performance of Recycled Concrete Brick Walls Embedded with Vertical Reinforcement

Science.gov (United States)

Cao, Wanlin; Zhang, Yongbo; Dong, Hongying; Zhou, Zhongyi; Qiao, Qiyun

2014-01-01

Recycled concrete brick (RCB) is manufactured by recycled aggregate processed from discarded concrete blocks arising from the demolishing of existing buildings. This paper presents research on the seismic performance of RCB masonry walls to assess the applicability of RCB for use in rural low-rise constructions. The seismic performance of a masonry wall is closely related to the vertical load applied to the wall. Thus, the compressive performance of RCB masonry was investigated firstly by constructing and testing eighteen RCB masonry compressive specimens with different mortar strengths. The load-bearing capacity, deformation and failure characteristic were analyzed, as well. Then, a quasi-static test was carried out to study the seismic behavior of RCB walls by eight RCB masonry walls subjected to an axial compressive load and a reversed cyclic lateral load. Based on the test results, equations for predicting the compressive strength of RCB masonry and the lateral ultimate strength of an RCB masonry wall were proposed. Experimental values were found to be in good agreement with the predicted values. Meanwhile, finite element analysis (FEA) and parametric analysis of the RCB walls were carried out using ABAQUS software. The elastic-plastic deformation characteristics and the lateral load-displacement relations were studied. PMID:28788170

Sensitization of the analytical methods for photoneutron calculations to the wall concrete composition in radiation therapy

International Nuclear Information System (INIS)

Ghiasi, Hosein; Mesbahi, Asghar

2012-01-01

The effect of wall material on photoneutron production in radiation therapy rooms was studied using Monte Carlo (MC) simulations. An analytical formula was proposed to take into account the concrete composition in photoneutron dose calculations. Using the MCNPX MC code, the 18 MV photon beam of the Varian Clinac 2100 and a typical treatment room with concrete compositions according to report No. 144 of National Council of Radiation Protection (NCRP) were simulated. Number of room produced photoneutrons per Gray of X-ray at the isocenter was determined for different types of concrete and named as “Q W ”. This new factor was inserted in the used formula for photoneutron fluence calculations at the inner entrance of maze. The photoneutron fluence was calculated using new proposed formula at the inner entrance of maze for all studied concretes. The difference between conventional and proposed equations varied from 11% to 46% for studied concretes. It was found that room produced photoneutrons could be significant for high density concretes. Additionally, applying the new proposed formula can consider the effect of wall material composition on the photoneutron production in high energy radiation therapy rooms. Further studies to confirm the accuracy of newly developed method is recommended.

Nonlinear Modeling of Autoclaved Aerated Concrete Masonry Wall Strengthened using Ferrocement Sandwich Structure

KAUST Repository

M., Abdel-Mooty; M., El-Kashef; E., Fahmy; M., Abou-Zeid; M., Haroun

2011-01-01

Autoclaved Aerated Concrete (AAC) block are used mainly as non-load-bearing walls that provide heat insulation. This results in considerable saving in cooling energy particularly in hot desert environment with large variation of daily and seasonal

The Neural Correlates of Abstract and Concrete Words: Evidence from Brain-Damaged Patients

OpenAIRE

Papagno, Costanza; Martello, Giorgia; Mattavelli, Giulia

2013-01-01

Neuropsychological and activation studies on the neural correlates of abstract and concrete words have produced contrasting results. The present study explores the anatomical substrates of abstract/concrete words in 22 brain-damaged patients with a single vascular lesion either in the right or left hemisphere. One hundred and twenty (60 concrete and 60 abstract) noun triplets were used for a semantic similarity judgment task. We found a significant interaction in word type × group since left ...

Design for whipping pipe impact on reinforced concrete panels

International Nuclear Information System (INIS)

Chen, C.C.; Gurbuz, O.

1984-01-01

This paper describes determination of local and overall effects on reinforced concrete panels due to whipping pipe impact in postulated pipe break events. Local damage includes the prediction of minimum concrete panel thickness required to prevent spalling from the back face of the target reinforced concrete panels. Evaluation of overall effect deals with the ductility ratio calculation for the target reinforced concrete panels. Design curves for determining the minimum panel thickness and the minimum reinforcement of reinforced concrete panels are presented in this paper for some cases commonly encountered in nuclear applications. The methodology and the results provided can be used to determine if an existing reinforced concrete wall is capable of resisting the whipping pipe impact, and consequently, if pipe whip restraints can be eliminated

Anisotropic 3D delay-damage model to simulate concrete structures

OpenAIRE

Gatuingt , Fabrice; Desmorat , Rodrigue; Chambart , Marion; Combescure , Didier; Guilbaud , Daniel

2008-01-01

International audience; High dynamic loadings lead to material degradation and structural failure. This is even more the case for concrete structures where the parts initially in compression break in ten- sion due to waves propagation and reflection. The dissymmetry of the material behavior plays a major role in such cases, dissymmetry mainly due to damage induced anisotropy. Loading induced damage is most often anisotropic and one proposes here to take advantage of such a feature to build a ...

Relationship between permeability and damage in concretes at high temperature

International Nuclear Information System (INIS)

Dal Pont, St.

2004-09-01

Due to its technical and economical advantages, concrete is nowadays the most used building material in civil engineering. Even if its use is known since nearly two centuries, its behavior has not been yet completely explained due to the complexity of its porous microstructure. This fact is quite evident under particular conditions such as, by instance, during an elevation of temperature. This condition can mainly occur in two cases: due to a casualty (e.g. a fire) or in normal use conditions (e.g. storage of nuclear rejects). This work aims at contributing to the study of the phenomena that can be observed in concrete exposed to high temperatures and, in particular, focuses on the study of the evolution of intrinsic permeability. The characterisation of permeability (which is hardly measurable in hot conditions) is necessary for describing and modelling transport phenomena which occur in porous media. An experimental study has been made in collaboration with the CEA. A real-scale hollow cylinder has been instrumented with gauges for studying the evolution of temperature and gas pressure fields inside concrete. Later, the cylinder has been then numerically modelled by means of a thermo-hydro-chemical (THC) and a thermo-hydro-chemo-mechanical (THCM) model. The THC model, implemented by means of the finite volume method, has allowed a first, qualitative study of the behaviour of concrete submitted to high temperature. This model, which, for sake of simplicity, has neglected all mechanical effects, has allowed the description of the main phenomena occurring inside concrete: mass transport, phase changes, microstructure evolution. Later, the modelling has been completed by means of the THCM model using the Hitecosp code, implemented by means of the finite element method at the university of Padua. This code allows a very complete description of the phenomena occurring inside concrete and takes into consideration the mechanical behavior of concrete by means of an

Study of the ruining behaviour of a structure with reinforced concrete carrying walls

International Nuclear Information System (INIS)

Manas, B.

1998-06-01

Nuclear facility buildings must be constructed with the respect of para-seismic rules. These rules are defined according to the most probable seismic risk estimated for the sites. This study concerns the ruining behaviour of a structure made of reinforced concrete walls. In a first part, a preliminary study on reinforced concrete is performed with the Castem 2000 finite elements code. This study emphasizes the non-linear phenomena that take place inside the material, such as the cracking of concrete and the plasticization of steels. In a second part, predictive calculations were performed on a U-shape structure. This structure was submitted to earthquakes of various magnitudes and the response of the structure was analyzed and interpreted. (J.S.)

Fire resistance of a steel plate reinforced concrete bearing wall

International Nuclear Information System (INIS)

Kodaira, Akio; Kanchi, Masaki; Fujinaka, Hideo; Akita, Shodo; Ozaki, Masahiko

2003-01-01

Samples from a steel plate reinforced concrete bearing wall composed of concrete slab sandwiched between studded steel plates, were subjected to loaded fire resistance tests. There were two types of specimens: some were 1800 mm high while the rest were 3000 mm high ; thickness and width were the same for all specimens, at 200 mm and 800 mm, respectively. Under constant load conditions, one side of each specimen was heated along the standard fire-temperature curve. The results enabled us to approximate the relationship between the ratio of working load to concrete strength N/(Ac x c σ b) and the fire resistance time (t: minutes), as equation (1) for the 1800 mm - high specimen, and equation (2) for the 3000 mm - high specimen. N/(Ac x c σ b) = 2.21 x (1/t) 0.323 (1), .N/(Ac x c σ b) 2.30 x (1/t) 0.378 (2) In addition, the temperature of the unheated side of the specimens was 100degC at 240 minutes of continuous heating, clearly indicating that there was sufficient heat insulation. (author)

Application of one-sided stress wave velocity measurement technique to evaluate freeze-thaw damage in concrete

International Nuclear Information System (INIS)

Lee, Joon Hyun; Park, Won Su

1998-01-01

It is well recognized that damage resulting from freeze-thaw cycles is a serious problems causing deterioration and degradation of concrete. In general, freeze-thaw cycles change the microstructure of the concrete ultimately leading to internal stresses and cracking. In this study, a new method for one-sided stress wave velocity measurement has been applied to evaluate freeze-thaw damage in concrete by monitoring the velocity change of longitudinal and surface waves. The freeze-thaw damage was induced in a 400 x 150 x 100 mm concrete specimen in accordance with ASTM C666 using s commercial testing apparatus. A cycle consisted of a variation of the temperature from -14 to 4 degrees Celsius. A cycle takes 4-5 hours with approximately equal times devoted to freezing-thawing. Measurement of longitudinal and surface wave velocities based on one-sided stress wave velocity measurement technique was made every 5 freeze-thaw cycle. The variation of longitudinal and surface wave velocities due to increasing freeze-thaw damage is demonstrated and compared to determine which one is more effective to monitor freeze-thaw cyclic damage progress. The variation in longitudinal wave velocity measured by one-sided technique is also compared with that measured by the conventional through transmission technique.

Analysis and design of column reinforced masonry and concrete walls

International Nuclear Information System (INIS)

Doyle, J.M.; Roy, S.B.; Fang, S.J.

1983-01-01

Fundamental frequencies, maximum moments and maximum shear forces are determined as a function of the governing parameters, for several different boundary conditions. The quantities are obtained for uniform panels, for walls with openings typical of doorways and other penetrations, and for panels having a region of degraded stiffness. In addition to the internal forces and moment due to out-of-plane action, the stresses due to in-plane loading are also found. From the results curves are constructed which allow for easy computation of flexural frequency, and bending moments and shears due to dynamic loads normal to the wall. Furthermore, based on the studies of panels with geometric or material discontinuities, corrections to results for uniform panels are found which can be used if openings or weakened areas exist in the wall. Several conclusions are presented concerning effects on behavior due to varied column location, critical stiffness ratio for columns to be effective, and the effect of openings on overall behavior. A number of design recommendations are presented. While the motivation for the study came from the need to design masonry walls, the analysis results are applicable to solid concrete walls reinforced by vertical columns. (orig./HP)

Guide to diagnosis and appraisal of AAR damage to concrete in structures

CERN Document Server

Rooij, Mario; Wood, Jonathan

2013-01-01

This book describes procedures and methodologies used predominantly to obtain a diagnosis of damaged concrete possibly caused by Alkali-Aggregate Reaction (AAR). It has two primary objectives, namely firstly to identify the presence of AAR reaction, and whether or not the reaction is the primary or contributory cause of damage in the concrete; and secondly, to establish its intensity (severity) in various members of a structure. It includes aspects such as field inspection of the structure, sampling, petrographic examination of core samples, and supplementary tests and analyses on cores, such as mechanical tests and chemical analysis. Evaluation of test data for prognosis, consequences and appraisal will be more fully set out in AAR-6.2.

A coupled mechanical and chemical damage model for concrete affected by alkali–silica reaction

Energy Technology Data Exchange (ETDEWEB)

Pignatelli, Rossella, E-mail: rossellapignatelli@gmail.com [Department of Civil and Environmental Engineering, Politecnico di Milano, Piazza L. da Vinci 32, 20133 Milano (Italy); Lombardi Ingegneria S.r.l., Via Giotto 36, 20145 Milano (Italy); Comi, Claudia, E-mail: comi@stru.polimi.it [Department of Civil and Environmental Engineering, Politecnico di Milano, Piazza L. da Vinci 32, 20133 Milano (Italy); Monteiro, Paulo J.M., E-mail: monteiro@ce.berkeley.edu [Department of Civil and Environmental Engineering, University of California, Berkeley, CA 94720 (United States)

2013-11-15

To model the complex degradation phenomena occurring in concrete affected by alkali–silica reaction (ASR), we formulate a poro-mechanical model with two isotropic internal variables: the chemical and the mechanical damage. The chemical damage, related to the evolution of the reaction, is caused by the pressure generated by the expanding ASR gel on the solid concrete skeleton. The mechanical damage describes the strength and stiffness degradation induced by the external loads. As suggested by experimental results, degradation due to ASR is considered to be localized around reactive sites. The effect of the degree of saturation and of the temperature on the reaction development is also modeled. The chemical damage evolution is calibrated using the value of the gel pressure estimated by applying the electrical diffuse double-layer theory to experimental values of the surface charge density in ASR gel specimens reported in the literature. The chemo-damage model is first validated by simulating expansion tests on reactive specimens and beams; the coupled chemo-mechanical damage model is then employed to simulate compression and flexure tests results also taken from the literature. -- Highlights: •Concrete degradation due to ASR in variable environmental conditions is modeled. •Two isotropic internal variables – chemical and mechanical damage – are introduced. •The value of the swelling pressure is estimated by the diffuse double layer theory. •A simplified scheme is proposed to relate macro- and microscopic properties. •The chemo-mechanical damage model is validated by simulating tests in literature.

Stripping demolition of concrete by applying electric current through reinforcing bars

International Nuclear Information System (INIS)

Nakagawa, Wahei; Kumegawa, Sadatsune

1995-01-01

The presence of reinforcing bars in reinforced concrete structures is an obstruction hindering the smooth progress of demolition works. The electric heating method is, on the other hand, a demolition technique of unique concept since it adopts the bars to help the demolition of reinforced concrete structures. This technique has the following advantages for demolition: 1) the more densely a structure is reinforced with bars, the greater is the effect of the electric heating, 2) demolition after heating produces little dust, and 3) electric heating of reinforcing bars causes no damage to the portions of concrete not subjected to electric current. The present paper describes the procedures and results of a series of experiments we conducted to verify the efficiency of the electric heating method. In this method, a low-voltage high-current is run through reinforcing bars existing in a concrete structure, inducing intense heat in the bars which in its turn brings about cracks in the surrounding concrete mass, facilitating secondary demolition by hammer picks or other means. The experiments were performed on full-scale biological shield wall mock-ups of a BWR and a small nuclear reactor. The experiments revealed that these excellent features of the electric heating method are worth utilizing in stripping demolition of radioactivated regions of biological shield walls in nuclear power plants. The electric heating method is currently being adopted and shows effective results in partial demolition works in diaphragm wall shafts where starting/arriving holes are to be fixed for shield machines without damaging surrounding portions. (author)

Using ultrasonic attenuation for assessing the fatigue damage of concrete

International Nuclear Information System (INIS)

Suaris, W.; Fernando, V.

1987-01-01

The results from cyclic loading tests indicate that damage accumulation as measured by pulse attenuation during cyclic loading is not linear, particularly during the initial cycles. The crack growth results obtained may be used for ascertaining the extent of damage in a in-situ structure using the following procedure: The ultrasonic waveforms obtained from a damaged region can first be compared with that obtained from the same region initially to yield a damage coefficient. Then the calibration charts obtained from laboratory specimens may be used to predict the extent of damage due to cyclic loading. The proposed method can also easily be extended to predict the deterioration due to shrinkage, creep and other environmental effects as long as their effect is to produce cracking in the concrete. (orig./HP)

Damage detection in concrete structures with smart piezoceramic transducers

Science.gov (United States)

Naidu, Akshay S. K.; Bhalla, Suresh

2003-10-01

Detection of damages and progressive deterioration in structures is a critical issue. Visual inspections are tedious and unreliable. Incipient damages are often not discernible by low frequency dynamic response and other NDE techniques. Smart piezoelectric ceramic (PZT) transducers are emerging as an effective alternative in health monitoring of structures. The electro-mechanical impedance method employs the self-actuating and sensing characteristics of the PZT, without having to use actuators and sensors separately. When excited by an ac source, the PZT transducers bonded to the host structure activates the higher modes of vibration locally. Changes in the admittance response of the transducer serves as an indicator of damage around the transducer. In this paper, the effectiveness of PZT transducers for characterizing damages in concrete, in terms of the damage extent and location, is experimentally examined. The root mean square deviation (RMSD) index, adopted to quantify the changes in the admittance signatures, correlates with the damage extent. The damages on the surface that is not mounted by the PZT are also discernible. An array of transducers proves effective in detecting the damaged zone. The progressive incipient crack can be detected much before it actually becomes visible to the naked eye.

An overview of an experimental program for testing large reinforced concrete shear walls

International Nuclear Information System (INIS)

Farrar, C.R.; Bennett, J.G.

1989-01-01

The Seismic Category I Structures Program is being carried out at the Los Alamos National Laboratory under sponsorship of the US Nuclear Regulatory Commission (NRC), Office of Nuclear Regulatory Research. In the class of structure being investigated, the primary lateral load-resisting structural element is the reinforced concrete shear wall. Previous results from microconcrete models indicated that these structures responded to seismic excitations with initial frequencies that were reduced by factors of 2 or more over those calculated based on an uncracked cross-section strength-of-materials approach. Furthermore, though the structures themselves were shown to have sufficient reserve margins, the equipment and piping are designed to response spectra that are based on uncracked cross-sectional member properties, and these spectra may not be inappropriate for actual building responses. The current phase of the program is aimed at verification of these conclusions using conventional concrete structures to demonstrate that previous microconcrete results can be scaled to prototype structures. A new configuration of a shear wall structure was designed and tested to investigate the analytical-experimental differences observed during the previous model testing. Shear wall height-to-length aspect ratios were to vary from 1 to 0.25. Percentage steel ratios were to vary from 0.25% to 0.6% by area, in both horizontal and vertical directions. The test structures are shown in Fig. 1. TRG-1 and -2 were constructed with microconcrete. TRG-3, -4, -5, and -6 were constructed with conventional (19-mm aggregate) concrete. 11 refs., 4 figs

SEISMIC PERFORMANCE OF A PRECAST REINFORCED CONCRETE WALL WITH CUT-OUT OPENING RETROFITTED USING CARBON FIBRE STRIPS

Directory of Open Access Journals (Sweden)

Fofiu M.

2015-05-01

Full Text Available The Precast Reinforced Concrete Wall Panel (PRCWP presented in this paper is part of an experimental study regarding the seismic performance of precast reinforced concrete wall panels, strengthening strategies and investigation on the weakening induced by modifying the opening in these elements due to architectural demands, change of function of buildings or other reasons. The element presented is 1:1.2 scale typical Reinforced Concrete Wall Panel with a window opening used in Romania, in which the opening was changed to a door opening due to comfort considerations. The specimen was subjected to cyclic loading with the lateral loads being applied in displacement control of 0.1% drift ratio. This simulates the shear behaviour of the element. After testing the unstrengthen element we proceed to retrofit it using Carbon Fibre Strips anchored with Carbon Fibre Mash. The purpose of the paper is to present the strengthening strategy and restore the initial load bearing capacity of the element or even increase it. The experimental results of strengthen and unstrengthen specimens will be presented.

Application of petrographic examination techniques to the assessment of fire-damaged concrete and masonry structures

International Nuclear Information System (INIS)

Ingham, Jeremy P.

2009-01-01

The number of building fires has doubled over the last 50 years. There has never been a greater need for structures to be assessed for fire damage to ensure safety and enable appropriate repairs to be planned. Fortunately, even after a severe fire, concrete and masonry structures are generally capable of being repaired rather than demolished. By allowing direct examination of microcracking and mineralogical changes, petrographic examination has become widely used to determine the depth of fire damage for reinforced concrete elements. Petrographic examination can also be applied to fire-damaged masonry structures built of materials such as stone, brick and mortar. Petrography can ensure accurate detection of damaged geomaterials, which provides cost savings during building repair and increased safety reassurance. This paper comprises a review of the role of petrography in fire damage assessments, drawing on a range of actual fire damage investigations.

PRE-CAST WALL PRODUCTS MADE FROM LIGHTWEIGHT CONCRETE FOR ENCLOSING STRUCTURES OF BUILDINGS

Directory of Open Access Journals (Sweden)

M. R. Hadgiev

2014-01-01

Full Text Available The paper is devoted to the actual problem waste dismantling of buildings and structures in the form of brick waste with reception the secondary fine and coarse aggregate and concrete based on them for the manufacture of small-piece wall products. 

Carbon Nanofiber Cement Sensors to Detect Strain and Damage of Concrete Specimens Under Compression.

Science.gov (United States)

Galao, Oscar; Baeza, F Javier; Zornoza, Emilio; Garcés, Pedro

2017-11-24

Cement composites with nano-additions have been vastly studied for their functional applications, such as strain and damage sensing. The capacity of a carbon nanofiber (CNF) cement paste has already been tested. However, this study is focused on the use of CNF cement composites as sensors in regular concrete samples. Different measuring techniques and humidity conditions of CNF samples were tested to optimize the strain and damage sensing of this material. In the strain sensing tests (for compressive stresses up to 10 MPa), the response depends on the maximum stress applied. The material was more sensitive at higher loads. Furthermore, the actual load time history did not influence the electrical response, and similar curves were obtained for different test configurations. On the other hand, damage sensing tests proved the capability of CNF cement composites to measure the strain level of concrete samples, even for loads close to the material's strength. Some problems were detected in the strain transmission between sensor and concrete specimens, which will require specific calibration of each sensor one attached to the structure.

Design basis and requirements for 241-SY Modular Exhauster concrete pad and retaining wall

International Nuclear Information System (INIS)

Kriskovich, J.R.

1994-01-01

The purpose of this document is to serve as the design and functional requirements for a concrete pad for the new 241-SY Modular Exhauster and for a retaining wall to be built near the new ventilation systems

HEAT INSULATING LIME DRY MORTARS FOR FINISHING OF WALLS MADE OF FOAM CONCRETE

Directory of Open Access Journals (Sweden)

Loganina Valentina Ivanovna

2016-05-01

Full Text Available Different aerated mortars are used for pargeting of walls made of aerated concrete. Though the regulatory documents don’t specify the dependence of plaster density from the density grade of gas-concrete blocks. In case of facing of gas-concrete blocks with the grade D500 using plaster mortars with the density 1400…1600 km/m3 there occurs a dismatch in the values of thermal insulation and vapor permeability of the plaster and base. The authors suggest using dry mortars for finishing of gas-concrete block of the grades D500 и D600, which allow obtaining facing thermal insulating coatings. The efficiency of using four different high-porous additives in the lime dry mortar was compared. They were: hollow glass microspheres, aluminosilicate ash microspheres, expanded vermiculite sand, expanded pearlitic sand. The high efficiency of hollow glass microspheres in heat insulating finishing mortars compared to other fillers is proved.

Modification of Concrete Damaged Plasticity model. Part II: Formulation and numerical tests

Directory of Open Access Journals (Sweden)

Kamińska Inez

2017-01-01

Full Text Available A refined model for elastoplastic damaged material is formulated based on the plastic potential introduced in Part I [1]. Considered model is an extension of Concrete Damaged Plasticity material implemented in Abaqus [2]. In the paper the stiffness tensor for elastoplastic damaged behaviour is derived. In order to validate the model, computations for the uniaxial tests are performed. Response of the model for various cases of parameter’s choice is shown and compared to the response of the CDP model.

Preventive measures against concrete damage to ASR in the Netherlands current state-of-affairs

NARCIS (Netherlands)

Heijnen, W.M.M.; Larbi, J.A.

1999-01-01

In CUR-Recommendation 38, various vital measures that need to be taken during design of new concrete-mixtures in order to prevent damage due to ASR in the concrete have been outlined. The most important of these measures are: - the use of blast furnace slag cement (with a high slag content: ≥50% by

Investigation on impact resistance of steel plate reinforced concrete barriers against aircraft impact. Pt.3: Analyses of full-scale aircraft impact

International Nuclear Information System (INIS)

Jun Mizuno; Norihide Koshika; Eiichi Tanaka; Atsushi Suzuki; Yoshinori Mihara; Isao Nishimura

2005-01-01

Steel plate reinforced concrete (SC) walls and slabs are structural members in which the rebars of reinforced concrete are replaced by steel plates. Steel plate reinforced concrete structures are more attractive structural design alternatives to reinforced concrete structures, especially with thick, heavily reinforced walls and slabs such as nuclear structures, because they enable a much shorter construction period, greater earthquake resistant and more cost effectiveness. Experimental and analytical studies performed by the authors have also shown that SC structures are much more effective in mitigating damage against scaled aircraft models , as described in Parts 1 and 2 of this study. The objective of Part 3 was to determine the protective capability of SC walls and roofs against a full-scale aircraft impact by conducting numerical experiments to investigate the fracture behaviors and limit thicknesses of SC panels and to examine the effectiveness of SC panels in detail under design conditions. Furthermore, a simplified method is proposed for evaluating the localized damage induced by a full-scale engine impact. (authors)

SCF analysis of a pressurized vessel-nozzle intersection with wall thinning damage

International Nuclear Information System (INIS)

Qadir, M.; Redekop, D.

2009-01-01

A three-dimensional finite element analysis is carried out of a pressurized vessel-nozzle intersection (tee joint), with wall thinning damage. A convergence-validation study is first carried out for undamaged intersections, in which comparisons are made with previously published work for the stress concentration factor (SCF), and good agreement is observed. A study is then carried out for specific tee joints to examine the effect on the SCF of varying the extent of the wall thinning damage. Finally, a parametric study is conducted in which the SCF is computed for a wide range of tee joints, initially considered undamaged, and then with wall thinning damage.

Damage detection monitoring applications in self-healing concrete structures using embedded piezoelectric transducers and recovery

International Nuclear Information System (INIS)

Karaiskos, G; Tsangouri, E; Aggelis, D G; Van Hemelrijck, D; Deraemaeker, A

2015-01-01

The ageing, operational and ambient loadings have a great impact in the operational and maintenance cost of concrete structures. Their service life prolongation is of utmost importance and this can be efficiently achieved by using reliable and low-cost monitoring and self-healing techniques. In the present study, the ultrasonic pulse velocity (UPV) method using embedded small-size and low-cost piezoelectric PZT (lead zirconate titanate) ceramic transducers in concrete with self-healing properties is implemented for monitoring not only the setting and hardening phases of concrete since casting time, but also for the detection of damage initiation, propagation and recovery of integrity after healing. A couple of small-scale notched unreinforced concrete beams are subjected to mode-I fracture through three-point bending tests. After a 24-hour healing agent curing period, the beams are reloaded using the same loading scenario. The results demonstrate the excellent performance of the proposed monitoring technique during the hydration, damage generation and recovery periods. (paper)

Evaluation of moisture damage in asphalt concrete with CRM motorcycle tire waste passing #50 sieve size

Science.gov (United States)

Siswanto, Henri; Supriyanto, Bambang; Pranoto, Pranoto; Chandra, Pria Rizky; Hakim, Arief Rahman

2017-09-01

The objective of this experimental research is to evaluate moisture damage in Asphalt Concrete (AC) with Crumb Rubber Modified (CRM) motorcycle tire waste passing #50 and retaining #100 sieve size. Two gradations were used in this research, the first gradation is usual for asphalt concrete base (ACB) and the second gradation is for asphalt concrete wearing course (ACWC). Marshall testing apparatus was used for testing the Marshall specimens. Seven levels of CRM content were used, namely 0%, 0.5%, 1%, 1.5%, 3%, 4.5% and 6% by weight of mixtures. Retained stability represent the level of moisture damage of AC pavement. The result indicates that addition CRM to the AC mixture increases their the stability to a maximum value and subsequent addition decrease the stability. The addition CRM to AC decreases their moisture damage susceptibility. AC with 1% CRM is the best asphalt-CRM mix.

Development and Evaluation of Cement-Based Materials for Repair of Corrosion-Damaged Reinforced Concrete Slabs

OpenAIRE

Liu, Rongtang; Olek, J.

2001-01-01

In this study, the results of an extensive laboratory investigation conducted to evaluate the properties of concrete mixes used as patching materials to repair reinforced concrete slabs damaged by corrosion are reported. Seven special concrete mixes containing various combinations of chemical or mineral admixtures were developed and used as a patching material to improve the durability of the repaired slabs. Physical and mechanical properties of these mixes, such as compressive strength, stat...

The evaluation of distributed damage in concrete based on sinusoidal modeling of the ultrasonic response.

Science.gov (United States)

Sepehrinezhad, Alireza; Toufigh, Vahab

2018-05-25

Ultrasonic wave attenuation is an effective descriptor of distributed damage in inhomogeneous materials. Methods developed to measure wave attenuation have the potential to provide an in-site evaluation of existing concrete structures insofar as they are accurate and time-efficient. In this study, material classification and distributed damage evaluation were investigated based on the sinusoidal modeling of the response from the through-transmission ultrasonic tests on polymer concrete specimens. The response signal was modeled as single or the sum of damping sinusoids. Due to the inhomogeneous nature of concrete materials, model parameters may vary from one specimen to another. Therefore, these parameters are not known in advance and should be estimated while the response signal is being received. The modeling procedure used in this study involves a data-adaptive algorithm to estimate the parameters online. Data-adaptive algorithms are used due to a lack of knowledge of the model parameters. The damping factor was estimated as a descriptor of the distributed damage. The results were compared in two different cases as follows: (1) constant excitation frequency with varying concrete mixtures and (2) constant mixture with varying excitation frequencies. The specimens were also loaded up to their ultimate compressive strength to investigate the effect of distributed damage in the response signal. The results of the estimation indicated that the damping was highly sensitive to the change in material inhomogeneity, even in comparable mixtures. In addition to the proposed method, three methods were employed to compare the results based on their accuracy in the classification of materials and the evaluation of the distributed damage. It is shown that the estimated damping factor is not only sensitive to damage in the final stages of loading, but it is also applicable in evaluating micro damages in the earlier stages providing a reliable descriptor of damage. In addition

Experimental investigation and analysis of damage evolution in concrete under high-cyclic fatigue loadings

International Nuclear Information System (INIS)

Thiele, Marc

2016-01-01

The main objective of this thesis is the fatigue behavior of concrete under high-cycle compressive loadings. Current knowledge about fatigue behavior of concrete is still incomplete. This concerns especially the process of fatigue which is preceding the fatigue failure. The leak of knowledge about fatigue behavior is opposed to the steady growing importance of this topic within the practice in civil engineering. Therefore, within this thesis a systematic and comprehensive investigation of the process of fatigue itself was done. This contributes to the better understanding of the progression of damage and the corresponding processes within the material. The experimental investigation consisted mainly of experiments with constant amplitude loadings in compression with cylindrical specimen made of normal strength concrete. Two differed load levels were used which resulted in numbers of cycles to failure of 10 6 and 10 7 as well as 10 3 and 10 4 . The experiments were done in combination with different types of nondestructive and destructive testing methods like strain measuring, deformation of surface, ultrasonic signals, acoustic emissions, optical microscopy and also scattering electron microscopy. To access some parameters of influence in relation to the fatigue behavior additional creep tests and also several tests with different scales of specimen were done. The fatigue process of concrete is determined as an evolution of damage that starts from the beginning of the loading process. This evolution has manifold and different influences on the different material properties of concrete. In this relation a major finding was that fatigue related damage leads to a transformation of the complete stress-strain-relationship. This relationship is also subjected to an evolution process. Due to the authors observations it could not be determined that the investigated changes in macroscopic material behavior are caused by a development of micro cracks within the material

An Experimental Investigation On Minimum Compressive Strength Of Early Age Concrete To Prevent Frost Damage For Nuclear Power Plant Structures In Cold Climates

International Nuclear Information System (INIS)

Koh, Kyungtaek; Kim, Dogyeum; Park, Chunjin; Ryu, Gumsung; Park, Jungjun; Lee, Janghwa

2013-01-01

Concrete undergoing early frost damage in cold weather will experience significant loss of not only strength, but also of permeability and durability. Accordingly, concrete codes like ACI-306R prescribe a minimum compressive strength and duration of curing to prevent frost damage at an early age and secure the quality of concrete. Such minimum compressive strength and duration of curing are mostly defined based on the strength development of concrete. However, concrete subjected to frost damage at early age may not show a consistent relationship between its strength and durability. Especially, since durability of concrete is of utmost importance in nuclear power plant structures, this relationship should be imperatively clarified. Therefore, this study verifies the feasibility of the minimum compressive strength specified in the codes like ACI-306R by evaluating the strength development and the durability preventing the frost damage of early age concrete for nuclear power plant. The results indicate that the value of 5 MPa specified by the concrete standards like ACI-306R as the minimum compressive strength to prevent the early frost damage is reasonable in terms of the strength development, but seems to be inappropriate in the viewpoint of the resistance to chloride ion penetration and freeze-thaw. Consequently, it is recommended to propose a minimum compressive strength preventing early frost damage in terms of not only the strength development, but also in terms of the durability to secure the quality of concrete for nuclear power plants in cold climates

An Experimental Investigation On Minimum Compressive Strength Of Early Age Concrete To Prevent Frost Damage For Nuclear Power Plant Structures In Cold Climates

Energy Technology Data Exchange (ETDEWEB)

Koh, Kyungtaek; Kim, Dogyeum; Park, Chunjin; Ryu, Gumsung; Park, Jungjun; Lee, Janghwa [Korea Institute Construction Technology, Goyang (Korea, Republic of)

2013-06-15

Concrete undergoing early frost damage in cold weather will experience significant loss of not only strength, but also of permeability and durability. Accordingly, concrete codes like ACI-306R prescribe a minimum compressive strength and duration of curing to prevent frost damage at an early age and secure the quality of concrete. Such minimum compressive strength and duration of curing are mostly defined based on the strength development of concrete. However, concrete subjected to frost damage at early age may not show a consistent relationship between its strength and durability. Especially, since durability of concrete is of utmost importance in nuclear power plant structures, this relationship should be imperatively clarified. Therefore, this study verifies the feasibility of the minimum compressive strength specified in the codes like ACI-306R by evaluating the strength development and the durability preventing the frost damage of early age concrete for nuclear power plant. The results indicate that the value of 5 MPa specified by the concrete standards like ACI-306R as the minimum compressive strength to prevent the early frost damage is reasonable in terms of the strength development, but seems to be inappropriate in the viewpoint of the resistance to chloride ion penetration and freeze-thaw. Consequently, it is recommended to propose a minimum compressive strength preventing early frost damage in terms of not only the strength development, but also in terms of the durability to secure the quality of concrete for nuclear power plants in cold climates.

The influence of the damaged reinforcing bars on the stress-strain state of the rein-forced concrete beams

Directory of Open Access Journals (Sweden)

Zenoviy Blikharskyy

2017-04-01

Full Text Available The article is devoted to the overall view of experimental research of reinforced concrete beams with the simultaneous influence of the corrosion environment and loading. The tests have been carried out upon the reinforced concrete specimens considering the corrosion in the acid environment, namely 10 % H2SO4 that have been taken as a model of the aggressive environment. The beams are with span equalling to 1,9m with different series of tensile armature, concrete compressive strength and different length of impact of corrosion (continuous and local. The influence of simultaneous action of the aggressive environment and loading on strength of reinforced-concrete beams has been described. For a detailed study of the effect of individual components there was suggested additional experimental modelling of the only tensile armature damage without concrete damage. It will investigate the influence of this factor irrespective of the concrete.

Experimental investigation of the relation between damage at the concrete-steel interface and initiation of reinforcement corrosion in plain and fibre reinforced concrete

International Nuclear Information System (INIS)

Michel, A.; Solgaard, A.O.S.; Pease, B.J.; Geiker, M.R.; Stang, H.; Olesen, J.F.

2013-01-01

Highlights: •Cracked plain and steel fibre reinforced concrete flexural beams were investigated. •“Instrumented rebars” provided location- and time-dependent corrosion measurements. •Interfacial condition can be used as a reliable indicator to quantify the risk of corrosion. •Simulated interfacial conditions are in very good agreement with all experimental observations. -- Abstract: Cracks in covering concrete are known to hasten initiation of steel corrosion in reinforced concrete structures. To minimise the impact of cracks on the deterioration of reinforced concrete structures, current approaches in (inter)national design codes often limit the concrete surface crack width. Recent investigations however, indicate that the concrete-reinforcement interfacial condition is a more fundamental criterion related to reinforcement corrosion. This work investigates the relation between macroscopic damage at the concrete-steel interface and corrosion initiation of reinforcement embedded in plain and fibre reinforced concrete. Comparisons of experimental and numerical results indicate a strong correlation between corrosion initiation and interfacial condition

Salt stress causes cell wall damage in yeast cells lacking mitochondrial DNA.

Science.gov (United States)

Gao, Qiuqiang; Liou, Liang-Chun; Ren, Qun; Bao, Xiaoming; Zhang, Zhaojie

2014-03-03

The yeast cell wall plays an important role in maintaining cell morphology, cell integrity and response to environmental stresses. Here, we report that salt stress causes cell wall damage in yeast cells lacking mitochondrial DNA (ρ 0 ). Upon salt treatment, the cell wall is thickened, broken and becomes more sensitive to the cell wall-perturbing agent sodium dodecyl sulfate (SDS). Also, SCW11 mRNA levels are elevated in ρ 0 cells. Deletion of SCW11 significantly decreases the sensitivity of ρ 0 cells to SDS after salt treatment, while overexpression of SCW11 results in higher sensitivity. In addition, salt stress in ρ 0 cells induces high levels of reactive oxygen species (ROS), which further damages the cell wall, causing cells to become more sensitive towards the cell wall-perturbing agent.

Modal Identification and Damage Detection on a Concrete Highway Bridge by Frequency Domain Decomposition

DEFF Research Database (Denmark)

Brincker, Rune; Andersen, P.; Zhang, L.

2002-01-01

As a part of a research project co-founded by the European Community, a series of 15 damage tests were performed on a prestressed concrete highway bridge in Switzerland. The ambient response of the bridge was recorded for each damage case. A dense array of instruments allowed the identification...

Modal Identification and Damage Detection on a Concrete Highway Bridge by Frequency Domain Decomposition

DEFF Research Database (Denmark)

Brincker, Rune; Andersen, Palle; Zhang, Lingmi

2007-01-01

As a part of a research project co-founded by the European Community, a series of 15 damage tests were performed on a prestressed concrete highway bridge in Switzerland. The ambient response of the bridge was recorded for each damage case. A dense array of instruments allowed the identification...

Emergency repair of severely damaged reinforced concrete columns using active confinement with shape memory alloys

International Nuclear Information System (INIS)

Shin, Moochul; Andrawes, Bassem

2011-01-01

This experimental study focuses on investigating the feasibility of utilizing spirals made of shape memory alloys (SMAs) to conduct emergency repair on severely damaged reinforced concrete (RC) columns. The thermally triggered shape memory feature of SMAs is sought in this study, to apply active confinement pressure on the column's damaged region. Two severely damaged 1/3-scale RC columns are repaired using the proposed technique and tested under a quasi-static lateral cyclic load. The repair of each column is conducted in less than 15 h, and the columns are tested 24 h after the starting of the repair process. The experimental results show that the new repair technique is successful in either fully restoring the as-built lateral strength, stiffness, and flexural ductility of the columns or making them even better. The efficacy of the proposed repair technique is mainly attributed to the ability of the SMA spirals to apply and maintain active confining pressure on the damaged region of the columns, which increases the strength of the already damaged concrete and delays its damage

Mid-infrared pulsed laser ablation of the arterial wall. Mechanical origin of "acoustic" wall damage and its effect on wall healing

NARCIS (Netherlands)

van Erven, L.; van Leeuwen, T. G.; Post, M. J.; van der Veen, M. J.; Velema, E.; Borst, C.

1992-01-01

Pulsed mid-infrared lasers are an alternative to excimer lasers for transluminal angioplasty. The mid-infrared lasers, however, were reported to produce "acoustic" wall damage that might impair the immediate and long-term results. To study the immediate and long-term effects on the arterial wall,

Nonlinear Modeling of Autoclaved Aerated Concrete Masonry Wall Strengthened using Ferrocement Sandwich Structure

KAUST Repository

M., Abdel-Mooty

2011-01-01

Autoclaved Aerated Concrete (AAC) block are used mainly as non-load-bearing walls that provide heat insulation. This results in considerable saving in cooling energy particularly in hot desert environment with large variation of daily and seasonal temperatures. However, due to the relatively low strength there use load bearing walls is limited to single storey and low-rise construction. A system to enhance the strength of the AAC masonry wall in resisting both inplane vertical and combined vertical and lateral loads using ferrocement technology is proposed in this research. The proposed system significantly enhances the load carrying capacity and stiffness of the AAC wall without affecting its insulation characteristics. Ferrocement is made of cement mortar reinforced with closely spaced wire mesh. Full scale wall specimens with height of 2100mm and width of 1820mm were tested with different configuration of ferrocement. A finite elementmodel is developed and verified against the experimentalwork. The results of the finite element model correlates well with the experimental results.

Reliability assessment and probability based design of reinforced concrete containments and shear walls

International Nuclear Information System (INIS)

Hwang, H.; Reich, M.; Ellingwood, B.; Shinozuka, M.

1986-03-01

This report summarizes work completed under the program entitled, ''Probability-Based Load Combinations for Design of Category I Structures.'' Under this program, the probabilistic models for various static and dynamic loads were formulated. The randomness and uncertainties in material strengths and structural resistance were established. Several limit states of concrete containments and shear walls were identified and analytically formulated. Furthermore, the reliability analysis methods for estimating limit state probabilities were established. These reliability analysis methods can be used to evaluate the safety levels of nuclear structures under various combinations of static and dynamic loads. They can also be used to generate analytically the fragility data for PRA studies. In addition to the development of reliability analysis methods, probability-based design criteria for concrete containments and shear wall structures have also been developed. The proposed design criteria are in the load and resistance factor design (LRFD) format. The load and resistance factors are determined for several limit states and target limit state probabilities. Thus, the proposed design criteria are risk-consistent and have a well-established rationale. 73 refs., 18 figs., 16 tabs

Structural health and dynamic behavior of residential buildings: field challenges in the rehab of damaged reinforced concrete

Directory of Open Access Journals (Sweden)

Chalhoub M. S.

2014-01-01

Full Text Available Reinforced concrete buildings require special consideration under dynamic excitations due to their anisotropic material properties. Strain compatibility equations are used in concrete analysis and design with assumptions about the stress and strain field across member section and member length. However, these assumptions fall short of describing real life behavior when concrete elements deteriorate, age or undergo cyclic loading. This paper addresses the structural health of reinforced concrete buildings and proposes an analytical model to account for concrete damage through loss of bond. The proposed model relates steel loading that causes bond distress to design parameters such as development length and bar properties, and therefore could be complemented by field measurement. The paper proposes a diagnosis method and discusses the sustainability of the structure by assisting in a simplistic decision rule as to whether to perform minor fixes, major rehabilitation, or disposal. Emphasis is placed on the difference between reversible and irreversible effects of cyclic loading on structural behaviour, and draws a distinction between damage to the girder and damage to the column in the overall structural system. The model is compared to empirical results to address field challenges faced when the structure is subjected to severe conditions in its ambient environment, or to unusual loading. Deterioration in concrete causes alteration in its composite behavior with the reinforcing steel. This affects the fundamental period of the structure, and its response to seismic loading.

Automobile impact forces on concrete wall panels. Technical report

International Nuclear Information System (INIS)

Chiapetta, R.L.; Pang, E.C.

1982-06-01

The objective of this study was to develop force-time impact signature data for use in the design or evaluation of nuclear power plant structures subject to tornado-borne automotive vehicle impact. The approach was based on the use of analytical vehicle models to calculate imact forces. To assess the significance of vehicle/structure interaction for head-on impact force-histories, a lumped-mass model of a reinforced concrete wall panel was coupled to a one-dimensional vehicle model for numerous panel design configurations within the range of practical interest. Vehicle-structure interaction was found to have relatively little effect on the force histories

Mesoscopic Numerical Computation of Compressive Strength and Damage Mechanism of Rubber Concrete

Directory of Open Access Journals (Sweden)

Z. H. Xie

2015-01-01

Full Text Available Evaluations of both macroscopic and mesoscopic strengths of materials have been the topic of a great deal of recent research. This paper presents the results of a study, based on the Walraven equation of the production of a mesoscopic random aggregate structure containing various rubber contents and aggregate sizes. On a mesoscopic scale, the damage mechanism in the rubber concrete and the effects of the rubber content and aggregate-mortar interface on the rubber concrete’s compressive resistance property were studied. The results indicate that the random aggregate structural model very closely approximates the experimental results in terms of the fracture distribution and damage characteristics under uniaxial compression. The aggregate-mortar interface mechanical properties have a substantial impact on the test sample’s strength and fracture distribution. As the rubber content increases, the compressive strength and elastic modulus of the test sample decrease proportionally. This paper presents graphics of the entire process from fracture propagation to structural failure of the test piece by means of the mesoscopic finite-element method, which provides a theoretical reference for studying the damage mechanism in rubber concrete and performing parametric calculations.

Contribution to the study of fluids transfers within a concrete wall: application to the case of a containment wall subjected to air tightness tests conditions and to accidental situation conditions

International Nuclear Information System (INIS)

Billard, Y.

2003-01-01

The correlation between the leak rate of a containment wall of nuclear power plants reactor buildings measured during periodic airtightness tests and the leak rate during a Loss Of Coolant Accident (LOCA) is a fundamental element in the security analysis of reactor building. The aim of this work is to contribute to the study of the transfers of fluids induced by these two types of loading in the case of a concrete wall integrating inhomogeneities and singularities capable to exist within the containment wall. In a first experimental phase, the development of a test rig allowing to work with concrete specimens having the same height as the thickness of containment wall of future nuclear power plant (1.3 m) permits to develop concrete compositions representative of these high air permeability zones. Their characterization is focused on the types of gaseous flow being able to exist within these high diffuse permeability concretes and on the structuring of their porous network. This step is completed by water vapour sorption measurements and by mercury porosimetry tests in the case of a concrete qualified according a leak flow criterion. In a second experimental phase, this concrete is subjected to air tightness tests conditions and to an accidental situation of LOCA type (141 deg C, effective humid air pressure equal to 4,2 bar) always with a thickness of 1.3 m. The analysis of pressure and temperature fields and the water content distributions is performed by an appropriate instrumentation which also permits the study of kinetics of the mass flux (both gaseous and liquid) crossing to the extrados of the wall. The numerical investigation is carried out with the Thermal-Hydro-Mechanic of non-saturated porous media model, recently implemented in Code Aster (developed by EDF). This model allows to consider all the fluid phases in presence. From a interpretation work of experimental data according to hypotheses of the model, notably towards the particular aspects bound up

Assessment of Mechanical Properties and Damage of High Performance Concrete Subjected to Magnesium Sulfate Environment

Directory of Open Access Journals (Sweden)

Sheng Cang

2017-01-01

Full Text Available Sulfate attack is one of the most important problems affecting concrete structures, especially magnesium sulfate attack. This paper presents an investigation on the mechanical properties and damage evolution of high performance concrete (HPC with different contents of fly ash exposure to magnesium sulfate environment. The microstructure, porosity, mass loss, dimensional variation, compressive strength, and splitting tensile strength of HPC were investigated at various erosion times up to 392 days. The ultrasonic pulse velocity (UPV propagation in HPC at different erosion time was determined by using ultrasonic testing technique. A relationship between damage and UPV of HPC was derived according to damage mechanics, and a correlation between the damage of HPC and erosion time was obtained eventually. The results indicated that (1 the average increasing amplitude of porosity for HPCs was 34.01% before and after exposure to magnesium sulfate solution; (2 the damage evolution of HPCs under sulfate attack could be described by an exponential fitting; (3 HPC containing 20% fly ash had the strongest resistance to magnesium sulfate attack.

Improved design of special boundary elements for T-shaped reinforced concrete walls

Science.gov (United States)

Ji, Xiaodong; Liu, Dan; Qian, Jiaru

2017-01-01

This study examines the design provisions of the Chinese GB 50011-2010 code for seismic design of buildings for the special boundary elements of T-shaped reinforced concrete walls and proposes an improved design method. Comparison of the design provisions of the GB 50011-2010 code and those of the American code ACI 318-14 indicates a possible deficiency in the T-shaped wall design provisions in GB 50011-2010. A case study of a typical T-shaped wall designed in accordance with GB 50011-2010 also indicates the insufficient extent of the boundary element at the non-flange end and overly conservative design of the flange end boundary element. Improved designs for special boundary elements of T-shaped walls are developed using a displacement-based method. The proposed design formulas produce a longer boundary element at the non-flange end and a shorter boundary element at the flange end, relative to those of the GB 50011-2010 provisions. Extensive numerical analysis indicates that T-shaped walls designed using the proposed formulas develop inelastic drift of 0.01 for both cases of the flange in compression and in tension.

Concrete Walls Crumble as Tunnel TI8 Breaks Through

CERN Multimedia

2001-01-01

On Wednesday, October 3rd, the excitement in the tunnels deep beneath CERN was high as an exuberant crowd watched the second and last transfer tunnel (TI8) from the SPS break through to the LHC. The Director-General with the Mayors of Meyrin and Prévessin at the breakthrough point. The area where the break through was to occur did not look particularly special, just a concrete wall with bright orange paint sprayed in the centre. But the austere surroundings quickly faded from importance as a tremendous ruckus filled the corridor. Just minutes later the first pieces of the wall started popping off. The suspense in the room grew and eventually the spinning drill became readily visible to the entire crowd.... and that's when the real noise started, the noise of applause! 'This is the second time I have seen this happen but it is always moving because it shows our steps forward.' said Prof. Luciano Maiani. Technicians, physicists, and engineers chatted excitedly as the tunnel team climbed through...

Concrete model for finite element analysis of structures subjected to severe damages

International Nuclear Information System (INIS)

Jamet, Ph.; Millard, A.; Hoffmann, A.; Nahas, G.; Barbe, B.

1984-01-01

A specific concrete model has been developed, in order to perform mechanical analysis of civil engineering structures, when subjected to accidental loadings, leading to severe damages. Its formulation is based on the physical mechanisms, which have been observed on laboratory specimens. The model has been implemented into the CASTEM finite element system, and the case of a concrete slab perforation by a rigid missile has been considered. The qualitative behaviour of the structure is well predicted by the model. Comparison between numerical and experimental results is also performed, using two main curves: missile velocity versus penetration depth; reaction forces versus time. (Author) [pt

Cracked reinforced concrete walls of chimneys, silos and cooling towers as result of using formworks

Directory of Open Access Journals (Sweden)

Maj Marek

2018-01-01

Full Text Available There are presented in this paper some problems connected with reinforced concrete shell objects operation in the aggressive environment and built in method of formworks. Reinforced concrete chimneys, cooling towers, silos and other shells were built for decades. Durability of cracked shells are one of the most important parameters during process of designing, construction and exploitation of shells. Some reasons of appearance of horizontal and vertical cracks as temperature, pressure of stored material, live loads e.g. dynamic character of wind, moisture, influence of construction joints, thermal insulation, chemistry active environmental etc. reduce the carrying capacity of the walls. Formworks, as is occurred recently, are the reason for technological joints with leaking connection, imperfections of flexible formworks slabs and as result can initiate cracks. Cracked surface of this constructions causes decreasing capacity and lower the state of reliability. Horizontal, vertical cracks can caused corrosion of concrete and steel bars, decreasing stiffness of contraction, increasing of deflection and carbonation of concrete cover. Local and global imperfactions of concrete shells are increasing according to greater number of cracks...

RESTORING A DAMAGED 16-YEAR -OLD INSULATING POLYMER CONCRETE DIKE OVERLAY: REPAIR MATERIALS AND TECHNOLOGIES.

Energy Technology Data Exchange (ETDEWEB)

SUGAMA,T.

2007-01-01

The objective of this program was to design and formulate organic polymer-based material systems suitable for repairing and restoring the overlay panels of insulating lightweight polymer concrete (ILPC) from the concrete floor and slope wall of a dike at KeySpan liquefied natural gas (LNG) facility in Greenpoint, Brooklyn, NY, just over sixteen years ago. It also included undertaking a small-scale field demonstration to ensure that the commercial repairing technologies were applicable to the designed and formulated materials.

Durability of thin-walled concrete structures

International Nuclear Information System (INIS)

Salomon, M.; Gallias, J.L.

1991-01-01

The aim of the present document is to draw up a survey of knowledge of the problems of ageing of reinforced concrete shell structure atmospheric coolers. The exposure conditions are particularly favourable to the induction and development of degradation which, because of the thinness of the reinforced concrete can compromise the stability and the durability of coolers. The study will be axed on the link between the specific characteristics of coolers from the point of view of operation, design and environment, also the durability of reinforced concrete. The set of factors exerting their influence on the reinforced concrete of the shell structure (condensates, rain water, temperature and humidity gradients, dynamic loads, weathering, etc.) is particularly complex. The principal degradation reactions involved are classified according to the chemical and physical action on concrete and on the reinforcement. Particular emphasis is placed on the analysis of degradation processes and the influence of the characteristics of the materials and of the medium. The aim is to determine the mechanisms which present the greatest risk for coolers. The interaction between the degradation to concrete and the change in mechanical characteristics is also studied [fr

Experimental evaluation of the interaction between strength concrete block walls under vertical loads

Directory of Open Access Journals (Sweden)

L. O. CASTRO

Full Text Available Abstract This paper aims to evaluate the interaction between structural masonry walls made of high performance concrete blocks, under vertical loads. Two H-shaped flanged wall series, all full scale and using direct bond, have been analyzed experimentally. In one series, three flanged-walls were built with the central wall (web supported and, in the other one, three specimens were built without any support at the central web. The load was applied on the central wall and vertical displacements were measured by means of displacement transducers located at eighteen points in the wall-assemblages. The results showed that the estimated load values for the flanges were close to those supported by the walls without central support, where 100% of the load transfer to the flanges occur. The average transfer load rate calculated based on the deformation ratio in the upper and lower section of the flanged-walls, with the central web support, were 37.65% and 77.30%, respectively, showing that there is load transfer from the central wall (web toward the flanges, particularly in the lower part of the flanged walls. Thus, there is indication that the distribution of vertical loads may be considered for projects of buildings for service load, such as in the method of isolated walls group. For estimation of the failure load, the method that considers the walls acting independently showed better results, due to the fact that failure started at the top of the central wall, where there is no effect of load distribution from the adjacent walls.

Finite element elasto-plastic analysis of thin walled structures of reinforced concrete as applied to reactor facilities

International Nuclear Information System (INIS)

Fujita, F.; Tsuboi, Y.

1981-01-01

The authors developed a new program of elasto-plastic analysis of reinforced concrete shells, in which the simplest model of shell element and an orthotropic constitutive relation are adopted, and verified its validity with reference to the results of model experiments of containers and box-wall structures with various loading conditions. For the two-dimensional stress-strain relationship of concrete, an orthotropic nonlinear formula proposed by one of the authors was adopted. For concrete, the octahedral shear failure and tension cut-off criteria were also imposed. The Kirchhoff-Love's assumptions were assumed to be valid for the whole range of the analysis and the layered approach of elasto-plastic stiffness evaluation. Derivation of the shell element is outlined with examination of its accuracy in elastic range and the assumption of elasto-plastic material property and the procedure of nonlinear analysis are described. As examples, the method is applied to the analysis of a cylindrical container and a box-wall structure. Comparison of the computed results with the corresponding experimental data indicates the applicability of the proposed method. (orig./HP)

Substructure hybrid testing of reinforced concrete shear wall structure using a domain overlapping technique

Science.gov (United States)

Zhang, Yu; Pan, Peng; Gong, Runhua; Wang, Tao; Xue, Weichen

2017-10-01

An online hybrid test was carried out on a 40-story 120-m high concrete shear wall structure. The structure was divided into two substructures whereby a physical model of the bottom three stories was tested in the laboratory and the upper 37 stories were simulated numerically using ABAQUS. An overlapping domain method was employed for the bottom three stories to ensure the validity of the boundary conditions of the superstructure. Mixed control was adopted in the test. Displacement control was used to apply the horizontal displacement, while two controlled force actuators were applied to simulate the overturning moment, which is very large and cannot be ignored in the substructure hybrid test of high-rise buildings. A series of tests with earthquake sources of sequentially increasing intensities were carried out. The test results indicate that the proposed hybrid test method is a solution to reproduce the seismic response of high-rise concrete shear wall buildings. The seismic performance of the tested precast high-rise building satisfies the requirements of the Chinese seismic design code.

First wall material damage induced by fusion-fission neutron environment

Energy Technology Data Exchange (ETDEWEB)

Khripunov, Vladimir, E-mail: Khripunov_VI@nrcki.ru

2016-11-01

Highlights: • The highest damage and gas production rates are experienced within the first wall materials of a hybrid fusion-fission system. • About ∼2 times higher dpa and 4–5 higher He appm are expected compared to the values distinctive for a pure fusion system at the same DT-neutron wall loading. • The specific nuclear heating may be increased by a factor of ∼8–9 due to fusion and fission neutrons radiation capture in metal components of the first wall. - Abstract: Neutronic performance and inventory analyses were conducted to quantify the damage and gas production rates in candidate materials when used in a fusion-fission hybrid system first wall (FW). The structural materials considered are austenitic SS, Cu-alloy and V- alloys. Plasma facing materials included Be, and CFC composite and W. It is shown that the highest damage rates and gas particles production in materials are experienced within the FW region of a hybrid similar to a pure fusion system. They are greatly influenced by a combined neutron energy spectrum formed by the two-component fusion-fission neutron source in front of the FW and in a subcritical fission blanket behind. These characteristics are non-linear functions of the fission neutron source intensity. Atomic displacement damage production rate in the FW materials of a subcritical system (at the safe subcriticality limit of ∼0.95 and the neutron multiplication factor of ∼20) is almost ∼2 times higher compared to the values distinctive for a pure fusion system at the same 14 MeV neutron FW loading. Both hydrogen (H) and helium (He) gas production rates are practically on the same level except of about ∼4–5 times higher He-production in austenitic and reduced activation ferritic martensitic steels. A proper simulation of the damage environment in hybrid systems is required to evaluate the expected material performance and the structural component residence times.

Deflection Prediction of No-Fines Lightweight Concrete Wall Using Neural Network Caused Dynamic Loads

Directory of Open Access Journals (Sweden)

Ridho Bayuaji

2018-04-01

Full Text Available No-fines lightweight concrete wall with horizontal reinforcement refers to an alternative material for wall construction with an aim of improving the wall quality towards horizontal loads. This study is focused on artificial neural network (ANN application to predicting the deflection deformation caused by dynamic loads. The ANN method is able to capture the complex interactions among input/output variables in a system without any knowledge of interaction nature and without any explicit assumption to model form. This paper explains the existing data research, data selection and process of ANN modelling training process and validation. The results of this research show that the deformation can be predicted more accurately, simply and quickly due to the alternating horizontal loads.

Frost induced damages within porous materials - from concrete technology to fuel cells technique

Science.gov (United States)

Palecki, Susanne; Gorelkov, Stanislav; Wartmann, Jens; Heinzel, Angelika

2017-12-01

Porous media like concrete or layers of membrane electrode assemblies (MEA) within fuel cells are affected by a cyclic frost exposure due to different damage mechanisms which could lead to essential degradation of the material. In general, frost damages can only occur in case of a specific material moisture content. In fuel cells, residual water is generally available after shut down inside the membrane i.e. the gas diffusion layer (GDL). During subsequent freezing, this could cause various damage phenomena such as frost heaves and delamination effects of the membrane electrode assembly, which depends on the location of pore water and on the pore structure itself. Porous materials possess a pore structure that could range over several orders of magnitudes with different properties and freezing behaviour of the pore water. Latter can be divided into macroscopic, structured and pre-structured water, influenced by surface interactions. Therefore below 0 °C different water modifications can coexist in a wide temperature range, so that during frost exposure a high amount of unfrozen and moveable water inside the pore system is still available. This induces transport mechanisms and shrinkage effects. The physical basics are similar for porous media. While the freezing behaviour of concrete has been studied over decades of years, in order to enhance the durability, the know-how about the influence of a frost attack on fuel cell systems is not fully understood to date. On the basis of frost damage models for concrete structures, an approach to describe the impact of cyclic freezing and thawing on membrane electrode assemblies has been developed within this research work. Major aim is beyond a better understanding of the frost induced mechanisms, the standardization of a suitable test procedure for the assessment of different MEA materials under such kind of attack. Within this contribution first results will be introduced.

Nonlinear analysis of pre-stressed concrete containment vessel (PCCV) using the damage plasticity model

Energy Technology Data Exchange (ETDEWEB)

Shokoohfar, Ahmad; Rahai, Alireza, E-mail: rahai@aut.ac.ir

2016-03-15

Highlights: • This paper describes nonlinear analyses of a 1:4 scale model of a (PCCV). • Coupled temp-disp. analysis and concrete damage plasticity are considered. • Temperature has limited effects on correct failure mode estimation. • Higher pre-stressing forces have limited effects on ultimate radial displacements. • Anchorage details of liner plates leads to prediction of correct failure mode. - Abstract: This paper describes the nonlinear analyses of a 1:4 scale model of a pre-stressed concrete containment vessel (PCCV). The analyses are performed under pressure and high temperature effects with considering anchorage details of liner plate. The temperature-time history of the model test is considered as an input boundary condition in the coupled temp-displacement analysis. The constitutive model developed by Chang and Mander (1994) is adopted in the model as the basis for the concrete stress–strain relation. To trace the crack pattern of the PCCV concrete faces, the concrete damage plasticity model is applied. This study includes the results of the thermal and mechanical behaviors of the PCCV subject to temperature loading and internal pressure at the same time. The test results are compared with the analysis results. The analysis results show that the temperature has little impact on the ultimate pressure capacity of the PCCV. To simulate the exact failure mode of the PCCV, the anchorage details of the liner plates around openings should be maintained in the analytical models. Also the failure mode of the PCCV structure hasn’t influenced by hoop tendons pre-stressing force variations.

Seismic response of reinforced concrete frames at different damage levels

Science.gov (United States)

Morales-González, Merangeli; Vidot-Vega, Aidcer L.

2017-03-01

Performance-based seismic engineering is focused on the definition of limit states to represent different levels of damage, which can be described by material strains, drifts, displacements or even changes in dissipating properties and stiffness of the structure. This study presents a research plan to evaluate the behavior of reinforced concrete (RC) moment resistant frames at different performance levels established by the ASCE 41-06 seismic rehabilitation code. Sixteen RC plane moment frames with different span-to-depth ratios and three 3D RC frames were analyzed to evaluate their seismic behavior at different damage levels established by the ASCE 41-06. For each span-to-depth ratio, four different beam longitudinal reinforcement steel ratios were used that varied from 0.85 to 2.5% for the 2D frames. Nonlinear time history analyses of the frames were performed using scaled ground motions. The impact of different span-to-depth and reinforcement ratios on the damage levels was evaluated. Material strains, rotations and seismic hysteretic energy changes at different damage levels were studied.

A compression and shear loading test of concrete filled steel bearing wall

International Nuclear Information System (INIS)

Akiyama, Hiroshi; Sekimoto, Hisashi; Fukihara, Masaaki; Nakanishi, Kazuo; Hara, Kiyoshi.

1991-01-01

Concrete-filled steel bearing walls called SC structure which are the composite structure of concrete and steel plates have larger load-carrying capacity and higher ductility as compared with conventional RC structures, and their construction method enables the rationalization of construction procedures at sites and the shortening of construction period. Accordingly, the SC structures have become to be applied to the inner concrete structures of PWR nuclear power plants, and subsequently, it is planned to apply them to the auxiliary buildings of nuclear power plants. The purpose of this study is to establish a rational design method for the SC structures which can be applied to the auxiliary buildings of nuclear power plants. In this study, the buckling strength of surface plates and the ultimate strength of the SC structure were evaluated with the results of the compression and shear tests which have been carried out. The outline of the study and the tests, the results of the compression test and the shear test and their evaluation are reported. Stud bolts were effective for preventing the buckling of surface plates. The occurrence of buckling can be predicted analytically. (K.I.)

A coupled thermo-hydro-mechanical-damage model for concrete subjected to moderate temperatures

Energy Technology Data Exchange (ETDEWEB)

Bary, B.; Carpentier, O. [CEA Saclay, DEN/DPC/SCCME/LECBA, F-91191 Gif Sur Yvette, (France); Ranc, G. [CEA VALRHO, DEN/DTEC/L2EC/LCEC, F-30207 Bagnols Sur Ceze, (France); Durand, S. [CEA Saclay, DEN/DM2S/SEMT/LM2S, F-91191 Gif Sur Yvette, (France)

2008-07-01

This study focuses on the concrete behavior subjected to moderate temperatures, with a particular emphasis on the transient thermo-hydric stage. A simplified coupled thermo-hydro-mechanical model is developed with the assumption that the gaseous phase is composed uniquely of vapor. Estimations of the mechanical parameters, Biot coefficient and permeability as a function of damage and saturation degree are provided by applying effective-medium approximation schemes. The isotherm adsorption curves are supposed to depend upon both temperature and crack-induced porosity. The effects of damage and parameters linked to transfer (in particular the adsorption curves) on the concrete structure response in the transient phase of heating are then investigated and evaluated. To this aim, the model is applied to the simulation of concrete cylinders with height and diameter of 0.80 m subjected to heating rates of 0.1 and 10 degrees C/min up to 160 degrees C. The numerical results are analyzed, commented and compared with experimental ones in terms of water mass loss, temperatures and gas pressures evolutions. A numerical study indicates that some parameters have a greater influence on the results than others, and that certain coupling terms in the mass conservation equation of water may be neglected. (authors)

Local and Modal Damage Indicators for Reinforced Concrete Shear Frames Subject to Earthquakes

DEFF Research Database (Denmark)

Köylüoglu, H. U.; Nielsen, Søren R. K.; Abbott, J.

Local, modal and overall damage indicators for reinforced concrete shear frames subject to seismic excitation are defined and studied. Each storey of the shear frame is represented by a Clough and Johnston hysteretic oscillator with degrading elastic fraction of the restoring force. The local max...

Experimental Studies on the Behavior of a Newly-Developed Type of Self-Insulating Concrete Masonry Shear Wall under in-Plane Cyclic Loading

Directory of Open Access Journals (Sweden)

Abu-Bakre Abdelmoneim Elamin Mohamad

2017-04-01

Full Text Available This study aimed to investigate the inelastic behavior of a newly-developed type of self-insulating concrete masonry shear wall (SCMSW under in-plane cyclic loading. The new masonry system was made from concrete blocks with special configurations to provide a stronger bond between units than ordinary concrete masonry units. A total of six fully-grouted SCMSWs were prepared with different heights (1.59 to 5.78 m and different vertical steel configurations. The developed masonry walls were tested under in-plane cyclic loading and different constant axial load ratios. In addition, the relationship between the amount of axial loading, the amount of the flexural reinforcement and the wall aspect ratios and the nonlinear hysteretic response of the SCMSW was evaluated. The results showed that the lateral load capacity of SCMSW increases with the amount of applied axial load and the amount of vertical reinforcement. However, the lateral load capacity decreases as the wall aspect ratio increases. The existence of the boundary elements at the SCMSW ends increases the ductility and the lateral load capacity. Generally, the SCMSW exhibited predominantly flexural behavior. These results agreed with those reported in previous research for walls constructed with ordinary units.

Automated crack detection in conductive smart-concrete structures using a resistor mesh model

Science.gov (United States)

Downey, Austin; D'Alessandro, Antonella; Ubertini, Filippo; Laflamme, Simon

2018-03-01

Various nondestructive evaluation techniques are currently used to automatically detect and monitor cracks in concrete infrastructure. However, these methods often lack the scalability and cost-effectiveness over large geometries. A solution is the use of self-sensing carbon-doped cementitious materials. These self-sensing materials are capable of providing a measurable change in electrical output that can be related to their damage state. Previous work by the authors showed that a resistor mesh model could be used to track damage in structural components fabricated from electrically conductive concrete, where damage was located through the identification of high resistance value resistors in a resistor mesh model. In this work, an automated damage detection strategy that works through placing high value resistors into the previously developed resistor mesh model using a sequential Monte Carlo method is introduced. Here, high value resistors are used to mimic the internal condition of damaged cementitious specimens. The proposed automated damage detection method is experimentally validated using a 500 × 500 × 50 mm3 reinforced cement paste plate doped with multi-walled carbon nanotubes exposed to 100 identical impact tests. Results demonstrate that the proposed Monte Carlo method is capable of detecting and localizing the most prominent damage in a structure, demonstrating that automated damage detection in smart-concrete structures is a promising strategy for real-time structural health monitoring of civil infrastructure.

A 3D Lattice Modelling Study of Drying Shrinkage Damage in Concrete Repair Systems

Directory of Open Access Journals (Sweden)

Mladena Luković

2016-07-01

Full Text Available Differential shrinkage between repair material and concrete substrate is considered to be the main cause of premature failure of repair systems. The magnitude of induced stresses depends on many factors, for example the degree of restraint, moisture gradients caused by curing and drying conditions, type of repair material, etc. Numerical simulations combined with experimental observations can be of great use when determining the influence of these parameters on the performance of repair systems. In this work, a lattice type model was used to simulate first the moisture transport inside a repair system and then the resulting damage as a function of time. 3D simulations were performed, and damage patterns were qualitatively verified with experimental results and cracking tendencies in different brittle and ductile materials. The influence of substrate surface preparation, bond strength between the two materials, and thickness of the repair material were investigated. Benefits of using a specially tailored fibre reinforced material, namely strain hardening cementitious composite (SHCC, for controlling the damage development due to drying shrinkage in concrete repairs was also examined.

Clinical evaluation of extraperitoneal colostomy without damaging the muscle layer of the abdominal wall.

Science.gov (United States)

Dong, L-R; Zhu, Y-M; Xu, Q; Cao, C-X; Zhang, B-Z

2012-01-01

This study investigated whether extraperitoneal colostomy without damaging the muscle layer of the abdominal wall is an improved surgical procedure compared with conventional sigmoid colostomy in patients undergoing abdominoperineal resection. Patients with rectal cancer undergoing abdominoperineal resection were selected and randomly divided into two groups: the study group received extraperitoneal colostomy without damaging the muscle layer of the abdominal wall and the control group received conventional colostomy. Clinical data from both groups were analysed. A total of 128 patients were included: 66 received extraperitoneal colostomy without damaging the muscle layer of the abdominal wall and 62 received conventional colostomy. Significant differences between the two groups were found in relation to colostomy operating time, defaecation sensation, bowel control and overall stoma-related complications. Duration of postoperative hospital stay was also significantly different between the study groups. Extraperitoneal colostomy without damaging the muscle layer of the abdominal wall was found to be an improved procedure compared with conventional sigmoid colostomy in abdominoperineal resection, and may reduce colostomy-related complications, shorten operating time and postoperative hospital stay, and potentially improve patients' quality of life.

Cost optimization of load carrying thin-walled precast high performance concrete sandwich panels

DEFF Research Database (Denmark)

Hodicky, Kamil; Hansen, Sanne; Hulin, Thomas

2015-01-01

and HPCSP’s geometrical parameters as well as on material cost function in the HPCSP design. Cost functions are presented for High Performance Concrete (HPC), insulation layer, reinforcement and include labour-related costs. The present study reports the economic data corresponding to specific manufacturing......The paper describes a procedure to find the structurally and thermally efficient design of load-carrying thin-walled precast High Performance Concrete Sandwich Panels (HPCSP) with an optimal economical solution. A systematic optimization approach is based on the selection of material’s performances....... The solution of the optimization problem is performed in the computer package software Matlab® with SQPlab package and integrates the processes of HPCSP design, quantity take-off and cost estimation. The proposed optimization process outcomes in complex HPCSP design proposals to achieve minimum cost of HPCSP....

Measures to prevent concrete damage due to alkali-silica reaction in the Netherlands: Current state-of-affairs

NARCIS (Netherlands)

Heijnen, W.M.M.; Larbi, J.A.

1999-01-01

In CUR-Recommendation 38, various vital measures that need to be taken during design of new concrete-mixtures in order to prevent damage due to ASR in the concrete have been outlined. The most important of these measures are: • the use of blast furnace slag cement (with a high slag content: 50 % by

Numerical Analysis of Carbon Fiber Reinforced Plastic (CFRP Shear Walls and Steel Strips under Cyclic Loads Using Finite Element Method

Directory of Open Access Journals (Sweden)

N. Askarizadeh

2017-12-01

Full Text Available Reinforced concrete shear walls are the main elements of resistance against lateral loads in reinforced concrete structures. These walls should not only provide sufficient resistance but also provide sufficient ductility in order to avoid brittle fracture, particularly under strong seismic loads. However, many reinforced concrete shear walls need to be stabilized and reinforced due to various reasons such as changes in requirements of seismic regulations, weaknesses in design and execution, passage of time, damaging environmental factors, patch of rebar in plastic hinges and in some cases failures and weaknesses caused by previous earthquakes or explosion loads. Recently, Fiber Reinforced Polymer (FRP components have been extensively and successfully used in seismic improvement. This study reinforces FRP reinforced concrete shear walls and steel strips. CFRP and steel strips are evaluated by different yield and ultimate strength. Numerical and experimental studies are done on walls with scale 1/2. These walls are exposed to cyclic loading. Hysteresis curves of force, drift and strain of FRP strips are reviewed in order to compare results of numerical work and laboratory results. Both numerical and laboratory results show that CFRP and steel strips increase resistance, capacity and ductility of the structure.

The Application of Buckling Reinforced Bracing and Shear Wall in Retrofitting of Existing Concrete Building

Directory of Open Access Journals (Sweden)

Mahdi Izadi

2015-06-01

Full Text Available Vulnerable buildings and their rehabilitation are important problems for earthquake regions. In recent decades the goal of building rehabilitation and strengthening has gained different rehabilitation systems. However, most of these strengthening techniques disturb the occupants, who must vacate the building during renovation. Several retrofitting techniques such as addition masonry infill wall, application of buckling restrained braces and local modification of components has been studied in order to improve the overall seismic performance of such buildings. In response to many of the practical issues and economic considerations, engineers use often convergent unbuckling steel bracing frames as the lateral load resisting system during an earthquake.This kind of bracings increases the hardness and strength of concrete structures.The aim of the present study is the evaluation and comparison of seismic performance and retrofitting of an existing 7-storeys concrete structure with buckling restrained bracings and shear walls by nonlinear static procedure (NSP and accordance with cod-361. The results show that the buckling restrained bracing, decreased drift to acceptable levels and Structure behaves on the life safety of performance level.

Study of the effect of hard projectiles impacting reinforced concrete walls

International Nuclear Information System (INIS)

Berriaud, C.; Sokolovsky, A.

1977-01-01

Among the risks examined in the framework of nuclear safety in France, quite unlikely events are examined as constituting a safety cover. This type of event includes the possible impact of aircrafts, or rotor splinters. Research on the limit strength of a wall under the impact of a hard projectile presently gives incentive results. First, a good agreement appears between works performed in parallel directions by EDF and CEA. Secondly, the special field of aerial projectiles is much better known as it was with previous formulations. Third, such research highly contributes to the knowledge of the mechanical strength of reinforced concrete structures [fr

Preventive measures against concrete damage to ASR in the Netherlands current state-of-affairs

OpenAIRE

Heijnen, W.M.M.; Larbi, J.A.

1999-01-01

In CUR-Recommendation 38, various vital measures that need to be taken during design of new concrete-mixtures in order to prevent damage due to ASR in the concrete have been outlined. The most important of these measures are: - the use of blast furnace slag cement (with a high slag content: ≥50% by mass of cement as slag); - or the use of portland fly ash cement (containing at least 25% by mass of cement as fly ash). If one of these cement types is used, then the potential reactivity of the a...

Influence of rock spalling on concrete lining in shaft sinking at the Horonobe Underground Research Laboratory

International Nuclear Information System (INIS)

Tsusaka, Kimikazu; Inagaki, Daisuke; Nago, Makito; Koike, Masashi; Matsubara, Makoto; Sugawara, Kentaro

2013-01-01

A shaft is the shortest way to access the deep underground. In shaft sinking through large-scale faults or under low competence factor, spalling of shaft walls is likely to occur. Although earlier studies indicated that rock spalling is an undesirable phenomenon that threatens safety in excavation work and causes delay in construction schedule, there have been few studies which discussed damage to concrete lining induced by spalling. Japan Atomic Energy Agency has been constructing three shafts (one for ventilation and the others for access) to a depth of 500 m in the Horonobe Underground Research Laboratory. During the construction of the Ventilation Shaft (4.5 m diameter) below a depth of 250 m, rock spalling occurred at several depths and an open crack developed in the concrete lining installed just above the location of the rock spalling. In this study, the geometry of the shaft wall was measured using a three-dimensional laser scanner. Numerical analysis was also conducted to estimate changes in stress distribution and deformation induced by rock spalling in both the concrete lining and the surrounding rock. As a result, it was clarified that rock spalling induced a vertical tensile stress in the concrete lining. Especially, the tensile stress in a concrete lining was likely to exceed the tensile strength of the concrete lining when it developed more than 100 cm into the wall rock. (author)

Local damage to Ultra High Performance Concrete structures caused by an impact of aircraft engine missiles

International Nuclear Information System (INIS)

Riedel, Werner; Noeldgen, Markus; Strassburger, Elmar; Thoma, Klaus; Fehling, Ekkehard

2010-01-01

Research highlights: → Experimental series on UHPC panels subjected to aircraft engine impact. → Improved ballistic limit of fiber reinforced UHPC in comparison to conventional R/C. → Detailed investigation of failure mechanisms of fiber reinforced UHPC panel. - Abstract: The impact of an aircraft engine missile causes high stresses, deformations and a severe local damage to conventional reinforced concrete. As a consequence the design of R/C protective structural elements results in components with rather large dimensions. Fiber reinforced Ultra High Performance Concrete (UHPC) is a concrete based material which combines ultra high strength, high packing density and an improved ductility with a significantly increased energy dissipation capacity due to the addition of fiber reinforcement. With those attributes the material is potentially suitable for improved protective structural elements with a reduced need for material resources. The presented paper reports on an experimental series of scaled aircraft engine impact tests with reinforced UHPC panels. The investigations are focused on the material behavior and the damage intensity in comparison to conventional concrete. The fundamental work of is taken as reference for the evaluation of the results. The impactor model of a Phantom F4 GE-J79 engine developed and validated by Sugano et al. is used as defined in the original work. In order to achieve best comparability, the experimental configuration and method are adapted for the UHPC experiments. With 'penetration', 'scabbing' and 'perforation' all relevant damage modes defined in are investigated so that a full set of results are provided for a representative UHPC structural configuration.

State of the art and further development of reinforced concrete wall cells for nuclear power plant construction

International Nuclear Information System (INIS)

Uhlemann, E.; Wartenberg, J.

1985-01-01

Reinforced concrete wall cells have been developed for nuclear power plant construction by the USSR and GDR. In this article, a new type of these cells, which will be used for constructing auxiliary equipment of the Stendal nuclear power plant, is described

Parametric analysis of AAR influent factors on thin-walled columns

Directory of Open Access Journals (Sweden)

E. L. Madureira

Full Text Available ABSTRACTThe chemical reaction involving the alkalis of the cement and some minerals of the concrete aggregates, the Alkali-Aggregate Reaction or, simply, the AAR, promotes swelling and material damages. Despite the development stage of the researches on this pathology effects, its solution modeling still lacks refinement. The numerical simulation is an important resource for the structural damages evaluation due to AAR, and their repairs. The aim of this work is the numerical simulation of concrete thin-walled columns, affected by the AAR, from the finite element approximation on an orthotropic nonlinear framework, and a thermodynamic model designed to the assessment of the AAR swelling, with highlight on the compressive stress, the reinforcement and the temperature influences on the phenomenon. The obtained results revealed that the AAR induced the concrete strength decrease and the consequent reduction in preventive safety margin to the material failure, being more precocious at higher temperatures.

Dynamic behavior of radiant cooling system based on capillary tubes in walls made of high performance concrete

DEFF Research Database (Denmark)

Mikeska, Tomás; Svendsen, Svend

2015-01-01

elements made of high performance concrete. The influence of the radiant cooling system on the indoor climate of the test room in terms of the air, surface and operative temperatures and velocities was investigated.The results show that the temperature of the room air can be kept in a comfortable range...... using cooling water for the radiant cooling system with a temperature only about 4K lower than the temperature of the room air. The relatively high speed reaction of the designed system is a result of the slim construction of the sandwich wall elements made of high performance concrete. (C) 2015...... the small amount of fresh air required by standards to provide a healthy indoor environment.This paper reports on experimental analyses evaluating the dynamic behavior of a test room equipped with a radiant cooling system composed of plastic capillary tubes integrated into the inner layer of sandwich wall...

Damage Detection of a Concrete Column Subject to Blast Loads Using Embedded Piezoceramic Transducers.

Science.gov (United States)

Xu, Kai; Deng, Qingshan; Cai, Lujun; Ho, Siuchun; Song, Gangbing

2018-04-28

Some of the most severe structural loadings come in the form of blast loads, which may be caused by severe accidents or even terrorist activities. Most commonly after exposure to explosive forces, a structure will suffer from different degrees of damage, and even progress towards a state of collapse. Therefore, damage detection of a structure subject to explosive loads is of importance. This paper proposes a new approach to damage detection of a concrete column structure subjected to blast loads using embedded piezoceramic smart aggregates (SAs). Since the sensors are embedded in the structure, the proposed active-sensing based approach is more sensitive to internal or through cracks than surface damage. In the active sensing approach, the embedded SAs act as actuators and sensors, that can respectively generate and detect stress waves. If the stress wave propagates across a crack, the energy of the wave attenuates, and the reduction of the energy compared to the healthy baseline is indicative of a damage. With a damage index matrix constructed by signals obtained from an array of SAs, cracks caused by blast loads can be detected throughout the structure. Conventional sensing methods such as the measurement of dynamic strain and acceleration were included in the experiment. Since columns are critical elements needed to prevent structural collapse, knowledge of their integrity and damage conditions is essential for safety after exposure to blast loads. In this research, a concrete column with embedded SAs was chosen as the specimen, and a series of explosive tests were conducted on the column. Experimental results reveal that surface damages, though appear severe, cause minor changes in the damage index, and through cracks result in significant increase of the damage index, demonstrating the effectiveness of the active sensing, enabled by embedded SAs, in damage monitoring of the column under blast loads, and thus providing a reliable indication of structural

In-Plane Strengthening Effect of Prefabricated Concrete Walls on Masonry Structures: Shaking Table Test

OpenAIRE

Li, Weiwei; Liu, Weiqing; Wang, Shuguang; Du, Dongsheng

2017-01-01

The improvement effect of a new strengthening strategy on dynamic action of masonry structure, by installing prefabricated concrete walls on the outer facades, is validated by shaking table test presented in this paper. We carried out dynamic tests of two geometrically identical five-story reduced scaled models, including an unstrengthened and a strengthened masonry model. The experimental analysis encompasses seismic performances such as cracking patterns, failure mechanisms, amplification f...

Critical Study of Corrosion Damaged Concrete Structures

OpenAIRE

Sallehuddin Shah Ayop; John Cairns

2013-01-01

Corrosion of steel reinforcement in concrete is one of the major problems with respect to the durability of reinforced concrete structures. The degradation of the structure strength due to reinforcement corrosion decreases its design life. This paper presents the literature study on the influence of the corrosion on concrete structure starting from the mechanism of the corrosion until the deterioration stage and the structural effects of corrosion on concrete structures.

Thermo-mechanical simulations of early-age concrete cracking with durability predictions

Science.gov (United States)

Havlásek, Petr; Šmilauer, Vít; Hájková, Karolina; Baquerizo, Luis

2017-09-01

Concrete performance is strongly affected by mix design, thermal boundary conditions, its evolving mechanical properties, and internal/external restraints with consequences to possible cracking with impaired durability. Thermo-mechanical simulations are able to capture those relevant phenomena and boundary conditions for predicting temperature, strains, stresses or cracking in reinforced concrete structures. In this paper, we propose a weakly coupled thermo-mechanical model for early age concrete with an affinity-based hydration model for thermal part, taking into account concrete mix design, cement type and thermal boundary conditions. The mechanical part uses B3/B4 model for concrete creep and shrinkage with isotropic damage model for cracking, able to predict a crack width. All models have been implemented in an open-source OOFEM software package. Validations of thermo-mechanical simulations will be presented on several massive concrete structures, showing excellent temperature predictions. Likewise, strain validation demonstrates good predictions on a restrained reinforced concrete wall and concrete beam. Durability predictions stem from induction time of reinforcement corrosion, caused by carbonation and/or chloride ingress influenced by crack width. Reinforcement corrosion in concrete struts of a bridge will serve for validation.

Study of the early age cracking of concrete massive structures: effect of the temperature decrease rate, steel reinforcement and construction joints

International Nuclear Information System (INIS)

Briffaut, M.

2010-01-01

At early-age, massive concrete structures (ex. nuclear power plant) are submitted to strains due to the hydration reaction. If they are restrained, crossing cracks can occurs. This cracking may increase significantly the concrete wall permeability. The objectives of this work was to characterize the early age concrete behavior (thermal and endogenous shrinkage, basic and thermal transient creep, mechanical characteristic evolution) as well as develop a new device to study the early age cracking of a concrete structure submitted to restrained shrinkage. The experimental campaign achieved with this new device (called thermal active ring test) and the numerical analysis of the test thanks to finite element simulations allows us to evaluate the coupling between creep and damage, to identify the tensile strength decrease due to construction joints and to quantify the effect of reinforcement on the concrete behaviour. Moreover, with this device, permeability measurements have been performed on a cracked specimen. Finally, numerical simulations of massive structures highlight the influence of boundary conditions for restrained shrinkage and the influence of the coupling between creep and damage on the damage pattern. (author)

Damaged Concrete Viaduct in an Italian Highway: Concrete Characterization and Possible Strengthening Techniques by FRP Applications in Comparison

Science.gov (United States)

Tittarelli, Francesca; Ruello, Maria Letizia; Capuani, Domenico; Aprile, Alessandra

2017-10-01

The “Fornello” viaduct in the Italian Orte-Ravenna highway (E45) is seriously damaged. In this paper, the concrete of the reinforced slab has been widely characterized to evaluate the level of damage and to identify the causes of degradation. No-destructive tests, as those based on ultrasonic waves, as well as chemical, physical and mechanical destructive tests have been carried out on specimens drawn from deteriorated and not deteriorated zones of the R/C bridge decks. Into the slab thickness, the concentration distribution of main anions has been quantified by ion chromatography. Porosimetry tests have been carried out to detect the resistance to freeze-thaw cycles of cement paste. Possible strengthening techniques by FRP applications have been compared.

Experimental Investigations on Effect of Damage on Vibration Characteristics of a Reinforced Concrete Beam

Science.gov (United States)

Srinivas, V.; Jeyasehar, C. Antony; Ramanjaneyulu, K.; Sasmal, Saptarshi

2012-02-01

Need for developing efficient non-destructive damage assessment procedures for civil engineering structures is growing rapidly towards structural health assessment and management of existing structures. Damage assessment of structures by monitoring changes in the dynamic properties or response of the structure has received considerable attention in recent years. In the present study, damage assessment studies have been carried out on a reinforced concrete beam by evaluating the changes in vibration characteristics with the changes in damage levels. Structural damage is introduced by static load applied through a hydraulic jack. After each stage of damage, vibration testing is performed and system parameters were evaluated from the measured acceleration and displacement responses. Reduction in fundamental frequencies in first three modes is observed for different levels of damage. It is found that a consistent decrease in fundamental frequency with increase in damage magnitude is noted. The beam is numerically simulated and found that the vibration characteristics obtained from the measured data are in close agreement with the numerical data.

Local damage to reinforced concrete structures caused by impact of aircraft engine missiles. Pt. 2

International Nuclear Information System (INIS)

Sugano, T.; Tsubota, H.; Kasai, Y.; Koshika, N.; Itoh, C.; Shirai, K.; Von Riesemann, W.A.; Bickel, D.C.; Parks, M.B.

1993-01-01

Three sets of impact tests, small-, intermediate-, and full-scale tests, have been executed to determine local damage to reinforced concrete structures caused by the impact of aircraft engine missiles. The results of the test program showed that (1) the use of the similarity law is appropriate, (2) suitable empirical formulas exist for predicting the local damage caused by rigid missiles, (3) reduction factors may be used for evaluating the reduction in local damage due to the deformability of the engines, (4) the reinforcement ratio has no effect on local damage, and (5) the test results could be adequately predicted using nonlinear response analysis. (orig.)

Multi-axial model of anisotropic damage: numerical management of failure and application to the ruin of reinforced concrete structures under impact

International Nuclear Information System (INIS)

Leroux, A.

2012-01-01

The objective of this research thesis is to develop the most precise possible numeric modelling of reinforced concrete behaviour with application to the design of structures of protection of nuclear plants against violent dynamic loadings (explosions, impacts). After a discussion of existing models, of their benefits and weaknesses, a multi-axial model of anisotropic damage is proposed and implemented with the finite element method. A new procedure of failure management is also proposed which allows the induced anisotropic damage to be taken into account. Impact tests on concrete beams and concrete cubes with longitudinal steel have been performed in order to validate the model [fr

Mineralogical and chemical assessment of concrete damaged by the oxidation of sulfide-bearing aggregates: Importance of thaumasite formation on reaction mechanisms

Energy Technology Data Exchange (ETDEWEB)

Rodrigues, A. [Centre de Recherche sur les Infrastructures en Beton (CRIB), Universite Laval, 1065 ave de la Medecine, Quebec, QC, Canada G1V 0A6 (Canada); Duchesne, J., E-mail: josee.duchesne@ggl.ulaval.ca [Centre de Recherche sur les Infrastructures en Beton (CRIB), Universite Laval, 1065 ave de la Medecine, Quebec, QC, Canada G1V 0A6 (Canada); Fournier, B. [Centre de Recherche sur les Infrastructures en Beton (CRIB), Universite Laval, 1065 ave de la Medecine, Quebec, QC, Canada G1V 0A6 (Canada); Durand, B. [Institut de recherche d' Hydro-Quebec (IREQ), 1740 boul. Lionel-Boulet, Varennes, QC, Canada J3X 1S1 (Canada); Rivard, P. [Universite de Sherbrooke, Sherbrooke, QC, Canada J1K 2R1 (Canada); Shehata, M. [Ryerson University, 350 Victoria Street, Toronto, ON, Canada M5B 2K3 (Canada)

2012-10-15

Damages in concrete containing sulfide-bearing aggregates were recently observed in the Trois-Rivieres area (Quebec, Canada), characterized by rapid deterioration within 3 to 5 years after construction. A petrographic examination of concrete core samples was carried out using a combination of tools including: stereomicroscopic evaluation, polarized light microscopy, scanning electron microscopy, X-ray diffraction and electron microprobe analysis. The aggregate used to produce concrete was an intrusive igneous rock with different metamorphism degrees and various proportions of sulfide minerals. In the rock, sulfide minerals were often surrounded by a thin layer of carbonate minerals (siderite). Secondary reaction products observed in the damaged concrete include 'rust' mineral forms (e.g. ferric oxyhydroxides such as goethite, limonite (FeO (OH) nH{sub 2}O) and ferrihydrite), gypsum, ettringite and thaumasite. In the presence of water and oxygen, pyrrhotite oxidizes to form iron oxyhydroxides and sulphuric acid. The acid then reacts with the phases of the cement paste/aggregate and provokes the formation of sulfate minerals. Understanding both mechanisms, oxidation and internal sulfate attack, is important to be able to duplicate the damaging reaction in laboratory conditions, thus allowing the development of a performance test for evaluating the potential for deleterious expansion in concrete associated with sulfide-bearing aggregates.

Mineralogical and chemical assessment of concrete damaged by the oxidation of sulfide-bearing aggregates: Importance of thaumasite formation on reaction mechanisms

International Nuclear Information System (INIS)

Rodrigues, A.; Duchesne, J.; Fournier, B.; Durand, B.; Rivard, P.; Shehata, M.

2012-01-01

Damages in concrete containing sulfide-bearing aggregates were recently observed in the Trois-Rivières area (Quebec, Canada), characterized by rapid deterioration within 3 to 5 years after construction. A petrographic examination of concrete core samples was carried out using a combination of tools including: stereomicroscopic evaluation, polarized light microscopy, scanning electron microscopy, X-ray diffraction and electron microprobe analysis. The aggregate used to produce concrete was an intrusive igneous rock with different metamorphism degrees and various proportions of sulfide minerals. In the rock, sulfide minerals were often surrounded by a thin layer of carbonate minerals (siderite). Secondary reaction products observed in the damaged concrete include “rust” mineral forms (e.g. ferric oxyhydroxides such as goethite, limonite (FeO (OH) nH 2 O) and ferrihydrite), gypsum, ettringite and thaumasite. In the presence of water and oxygen, pyrrhotite oxidizes to form iron oxyhydroxides and sulphuric acid. The acid then reacts with the phases of the cement paste/aggregate and provokes the formation of sulfate minerals. Understanding both mechanisms, oxidation and internal sulfate attack, is important to be able to duplicate the damaging reaction in laboratory conditions, thus allowing the development of a performance test for evaluating the potential for deleterious expansion in concrete associated with sulfide-bearing aggregates.

Fissuring-chemical damaging on transfers in concrete

International Nuclear Information System (INIS)

Tognazzi, C.

1998-01-01

Concrete is a material often use in the nuclear wastes disposal. The safety analysis of a long time wastes disposal with concrete requires to verify the concrete behaviour in water. As concretes generally have cracks, it is necessary to study the crack propagation influence on chemical degradation. In this paper, the author presents diffusion tests on fissured and/or chemical aged cement. The chemical degradation of the material leads to a supplementary porosity by the hydrates decalcification and increases its diffusivity. The cracking impact is less important and can be experimentally concealed. (A.L.B.)

Interfacial damage identification of steel and concrete composite beams based on piezoceramic wave method.

Science.gov (United States)

Yan, Shi; Dai, Yong; Zhao, Putian; Liu, Weiling

2018-01-01

Steel-concrete composite structures are playing an increasingly important role in economic construction because of a series of advantages of great stiffness, good seismic performance, steel material saving, cost efficiency, convenient construction, etc. However, in service process, due to the long-term effects of environmental impacts and dynamic loading, interfaces of a composite structure might generate debonding cracks, relative slips or separations, and so on, lowering the composite effect of the composite structure. In this paper, the piezoceramics (PZT) are used as transducers to perform experiments on interface debonding slips and separations of composite beams, respectively, aimed at proposing an interface damage identification model and a relevant damage detection innovation method based on PZT wave technology. One part of various PZT patches was embedded in concrete as "smart aggregates," and another part of the PZT patches was pasted on the surface of the steel beam flange, forming a sensor array. A push-out test for four specimens was carried out and experimental results showed that, under the action of the external loading, the received signal amplitudes will increasingly decrease with increase of debonding slips along the interface. The proposed signal energy-based interface damage detection algorithm is highly efficient in surface state evaluations of composite beams.

Concrete Materials with Ultra-High Damage Resistance and Self- Sensing Capacity for Extended Nuclear Fuel Storage Systems

Energy Technology Data Exchange (ETDEWEB)

Li, Mo [Univ. of California, Irvine, CA (United States); Nakshatrala, Kalyana [Univ. of Houston, TX (United States); William, Kasper [Univ. of Houston, TX (United States); Xi, Yungping [Univ. of Colorado, Boulder, CO (United States)

2017-02-08

The objective of this project is to develop a new class of multifunctional concrete materials (MSCs) for extended spent nuclear fuel (SNF) storage systems, which combine ultra-high damage resistance through strain-hardening behavior with distributed multi-dimensional damage self-sensing capacity. The beauty of multifunctional concrete materials is two-fold: First, it serves as a major material component for the SNF pool, dry cask shielding and foundation pad with greatly improved resistance to cracking, reinforcement corrosion, and other common deterioration mechanisms under service conditions, and prevention from fracture failure under extreme events (e.g. impact, earthquake). This will be achieved by designing multiple levels of protection mechanisms into the material (i.e., ultrahigh ductility that provides thousands of times greater fracture energy than concrete and normal fiber reinforced concrete; intrinsic cracking control, electrochemical properties modification, reduced chemical and radionuclide transport properties, and crack-healing properties). Second, it offers capacity for distributed and direct sensing of cracking, strain, and corrosion wherever the material is located. This will be achieved by establishing the changes in electrical properties due to mechanical and electrochemical stimulus. The project will combine nano-, micro- and composite technologies, computational mechanics, durability characterization, and structural health monitoring methods, to realize new MSCs for very long-term (greater than 120 years) SNF storage systems.

Condition Assessment for Wastewater Pipes: Method for Assessing Cracking and Surface Damage of Concrete Pipes

OpenAIRE

Hauge, Petter

2013-01-01

The objective of the Master Thesis has been to provide an improved method for condition assessment, which will give a better correlation between Condition class and actual Condition of concrete pipes with cracking and/or surface damages. Additionally improvement of the characterization of cracking (SR) and surface (KO) damages was a sub goal.Based on the findings described in my Thesis and my Specialization Project (Hauge 2012), I recommend that the Norwegian condition assessment method based...

Shake-table testing of a self-centering precast reinforced concrete frame with shear walls

Science.gov (United States)

Lu, Xilin; Yang, Boya; Zhao, Bin

2018-04-01

The seismic performance of a self-centering precast reinforced concrete (RC) frame with shear walls was investigated in this paper. The lateral force resistance was provided by self-centering precast RC shear walls (SPCW), which utilize a combination of unbonded prestressed post-tensioned (PT) tendons and mild steel reinforcing bars for flexural resistance across base joints. The structures concentrated deformations at the bottom joints and the unbonded PT tendons provided the self-centering restoring force. A 1/3-scale model of a five-story self-centering RC frame with shear walls was designed and tested on a shake-table under a series of bi-directional earthquake excitations with increasing intensity. The acceleration response, roof displacement, inter-story drifts, residual drifts, shear force ratios, hysteresis curves, and local behaviour of the test specimen were analysed and evaluated. The results demonstrated that seismic performance of the test specimen was satisfactory in the plane of the shear wall; however, the structure sustained inter-story drift levels up to 2.45%. Negligible residual drifts were recorded after all applied earthquake excitations. Based on the shake-table test results, it is feasible to apply and popularize a self-centering precast RC frame with shear walls as a structural system in seismic regions.

Damage location and quantification of a pretensioned concrete beam using stochastic subspace identification

Science.gov (United States)

Cancelli, Alessandro; Micheli, Laura; Laflamme, Simon; Alipour, Alice; Sritharan, Sri; Ubertini, Filippo

2017-04-01

Stochastic subspace identification (SSID) is a first-order linear system identification technique enabling modal analysis through the time domain. Research in the field of structural health monitoring has demonstrated that SSID can be used to successfully retrieve modal properties, including modal damping ratios, using output-only measurements. In this paper, the utilization of SSID for indirectly retrieving structures' stiffness matrix was investigated, through the study of a simply supported reinforced concrete beam subjected to dynamic loads. Hence, by introducing a physical model of the structure, a second-order identification method is achieved. The reconstruction is based on system condensation methods, which enables calculation of reduced order stiffness, damping, and mass matrices for the structural system. The methods compute the reduced order matrices directly from the modal properties, obtained through the use of SSID. Lastly, the reduced properties of the system are used to reconstruct the stiffness matrix of the beam. The proposed approach is first verified through numerical simulations and then validated using experimental data obtained from a full-scale reinforced concrete beam that experienced progressive damage. Results show that the SSID technique can be used to diagnose, locate, and quantify damage through the reconstruction of the stiffness matrix.

Retrofitting of Reinforced Concrete Beams using Reactive Powder Concrete (RPC)

Science.gov (United States)

Karthik, S.; Sundaravadivelu, Karthik

2017-07-01

Strengthening of existing damaged structures is one of the leading studies in civil engineering. The purpose of retrofitting is to structurally treat the member with an aim to restore the structure to its original strength. The focus of this project is to study the behaviour of damaged Reinforced Concrete beam retrofitted with Reactive Powder Concrete (RPC) Overlay. Reinforced concrete beams of length 1200 mm, width 100 mm and depth 200 mm were casted with M30 grade of concrete in the laboratory and cured for 28 days. One beam is taken as control and are tested under two point loading to find out ultimate load. Remaining beams are subjected to 90 % ultimate load of control beams. The partially damaged beams are retrofitted with Reactive Powder Concrete Overlay at the full tension face of the beam and side overlay depends upon the respectable retrofitting techniques with 10 mm and 20 mm thick layer to find optimum. Materials like steel fibres are added to enhance the ductility by eliminating coarse particle for homogeneity of the structure. Finally, the modes of failure for retrofitted beams are analysed experimentally under two point loading & compared the results with Control beam.

Determining the Surfactant Consistent with Concrete in order to Achieve the Maximum Possible Dispersion of Multi walled Carbon Nano tubes in Keeping the Plain Concrete Properties

International Nuclear Information System (INIS)

Adresi, M.; Hassani, A.; Javadian, S.; Tulliani, J. M.

2016-01-01

A new surfactant combination compatible with concrete formulation is proposed to avoid unwanted air bubbles created during mixing process in the absence of a defoamer and to achieve the uniform and the maximum possible dispersion of multi walled carbon nano tubes (MWCNTs) in water and subsequently in concrete. To achieve this goal, three steps have been defined: (1) concrete was made with different types and amount of surfactants containing a constant amount of MWCNTs (0.05 wt%) and the air bubbles were eliminated with a proper defoamer. (2) Finding a compatible surfactant with concrete compositions and eliminating unwanted air bubbles in the absence of a common defoamer are of fundamental importance to significantly increase concrete mechanical properties. In this step, the results showed that the poly carboxylate super plasticizer (SP-C) (as a compatible surfactant) dispersed MWCNTs worse than SDS/DTAB but unwanted air bubbles were removed, so the defoamer can be omitted in the mixing process. (3) To solve the problem, a new compatible surfactant composition was developed and different ratios of surfactants were tested and evaluated by means of performance criteria mentioned above. The results showed that the new surfactant composition (SDS and SP-C) can disperse MWCNTs around 24% more efficiently than the other surfactant compositions.

Dynamic Impact Analyses and Tests of Concrete Overpacks - 13638

Energy Technology Data Exchange (ETDEWEB)

Lee, Sanghoon; Cho, Sang-Soon; Kim, Ki-Young; Jeon, Je-Eon; Seo, Ki-Seog [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

2013-07-01

Concrete cask is an option for spent nuclear fuel interim storage which is prevailingly used in US. A concrete cask usually consists of metallic canister which confines the spent nuclear fuel and concrete overpack. When the overpack undergoes a severe missile impact which might be caused by a tornado or an aircraft crash, it should sustain acceptable level of structural integrity so that its radiation shielding capability and the retrievability of canister are maintained. Missile impact against a concrete overpack involves two damage modes, local damage and global damage. Local damage of concrete is usually evaluated by empirical formulas while the global damage is evaluated by finite element analysis. In many cases, those two damage modes are evaluated separately. In this research, a series of numerical simulations are performed using finite element analysis to evaluate the global damage of concrete overpack as well as its local damage under high speed missile impact. We consider two types of concrete overpack, one with steel in-cased concrete without reinforcement and the other with partially-confined reinforced concrete. The numerical simulation results are compared with test results and it is shown that appropriate modeling of material failure is crucial in this analysis and the results are highly dependent on the choice of failure parameters. (authors)

Dynamic Impact Analyses and Tests of Concrete Overpacks - 13638

International Nuclear Information System (INIS)

Lee, Sanghoon; Cho, Sang-Soon; Kim, Ki-Young; Jeon, Je-Eon; Seo, Ki-Seog

2013-01-01

Concrete cask is an option for spent nuclear fuel interim storage which is prevailingly used in US. A concrete cask usually consists of metallic canister which confines the spent nuclear fuel and concrete overpack. When the overpack undergoes a severe missile impact which might be caused by a tornado or an aircraft crash, it should sustain acceptable level of structural integrity so that its radiation shielding capability and the retrievability of canister are maintained. Missile impact against a concrete overpack involves two damage modes, local damage and global damage. Local damage of concrete is usually evaluated by empirical formulas while the global damage is evaluated by finite element analysis. In many cases, those two damage modes are evaluated separately. In this research, a series of numerical simulations are performed using finite element analysis to evaluate the global damage of concrete overpack as well as its local damage under high speed missile impact. We consider two types of concrete overpack, one with steel in-cased concrete without reinforcement and the other with partially-confined reinforced concrete. The numerical simulation results are compared with test results and it is shown that appropriate modeling of material failure is crucial in this analysis and the results are highly dependent on the choice of failure parameters. (authors)

Floors number influence on the instability parameter of reinforced concrete wall- or core-braced buildings

Directory of Open Access Journals (Sweden)

R. J. Ellwanger

Full Text Available This work aims to investigate the floors number influence on the instability parameter limit α1 of buildings braced by reinforced concrete walls and/or cores. Initially, it is showed how the Beck and König discrete and continuous models are utilized in order to define when a second order analysis is needed. The treatment given to this subject by the Brazilian code for concrete structures design (NBR 6118 is also presented. It follows a detailed analytical study that led to the derivation of equations for the limit α1 as functions of the floors number; a series of examples is presented to check their accuracy. Results are analyzed, showing the precision degree achieved and topics for continuity of research in this field are indicated.

Large-scale experiment with laying shielding concrete at Dukovany nuclear power plant

International Nuclear Information System (INIS)

Hoenig, A.; Svoboda, R.; Rosa, J.

1984-01-01

In some places the concrete walls of the biological shielding are so thin that it is not possible to control the density of the deposited concrete. An experiment was therefore carried out which was to demonstrate that concrete may be deposited by sinking through concrete tubes or by a concrete pump from a height of 8 metres. Two test walls A and B were concreted using the non-standardized method and the third wall was used as the standard. The following tests were conducted on the two non-standardized walls: test of miscibility of extra-heavy concrete, ultrasonic test of homogeneity, and samples were taken for tests of density. Density was determined radiometrically using a narrow gamma beam. Statistical evaluation of the results showed that the homogeneity of density of the concrete was the best in the standard wall, in walls A and B the variation coefficient did not exceed 8 per mille. An exception was made to the rule and concrete with a max. 16 mm grain size was deposited from the height of 8 m on condition of strict observance of production technology. (J.P.)

Performance of Damaged Soil-Concrete Wraparound Dam Sections under Dynamic Loading

Energy Technology Data Exchange (ETDEWEB)

Kanarska, Y; Lomov, I; Glascoe, L; Morris, J; Antoun, T; Hall, R; Woodson, S; Fortune, J; Hynes, M E

2009-09-28

Predicting seismic or shock loading damage of the soil-concrete interface where an embankment wraparound dam provides support to the end monoliths in a concrete gravity dam is an inherently challenging three-dimensional coupled problem. We wish to predict formation and growth of a crack between the soil and concrete with a sustained flow of water. Further, we seek to better understand all critical phenomenology of this type of problem such as the potential mitigating and stabilizing role of upstream and downstream filter zone and shell materials. This collaborative research effort will ultimately determine whether advances in computational platforms, constitutive soil models (advances in representing particulates, tension, flow, and hydraulic erosion), and physical testing (advances in centrifuge and flume testing) can be applied successfully to solve this complex problem. Our focus is (1) to develop and validate high fidelity numerical models to investigate crack formation, soil erosion, transport of materials, and stability as part of the erosion process, and deposition within interface cracks; and (2) to investigate the performance of the filter zone materials if an extreme loading event such as an earthquake or shock damages the wraparound section. Our numerical tools include both continuum and discrete approaches. The continuum approach is based on the drift-flux multiphase model where a fluid and a solid are represented as interpenetrating continua and can account for turbulent flow characteristics, particle lift forces due to shear flow, particle collisions, and gravity settling. The discrete particle approach is also applied and is useful when deriving constitutive laws and parameterizations of soil behavior. Different experimental validation studies are under consideration for model validation and calibration. Several case studies for different crack sizes and orientations, particle sizes and environmental hydraulic conditions may be required to confirm

Numerical Derivation of Iso-Damaged Curve for a Reinforced Concrete Beam Subjected to Blast Loading

Directory of Open Access Journals (Sweden)

Temsah Yehya

2018-01-01

Full Text Available Many engineering facilities are severely damaged by blast loading. Therefore, many manufacturers of sensitive, breakable, and deformed structures (such as facades of glass buildings carry out studies and set standards for these installations to withstand shock waves caused by explosions. Structural engineers also use these standards in their designs for various structural elements by following the ISO Damage Carve, which links pressure and Impulse. As all the points below this curve means that the structure is safe and will not exceed the degree of damage based on the various assumptions made. This research aims to derive the Iso-Damage curve of a reinforced concrete beam exposed to blast wave. An advanced volumetric finite element program (ABAQUS will be used to perform the derivation.

Local behavior of reinforced concrete slabs to aircraft engine projectile impact

International Nuclear Information System (INIS)

Yoo, Hyeon Kyeong; Choi, Hyun; Chung, Chul Hun; Lee, Jung Whee; Kim, Sang Yun

2011-01-01

Structural safety evaluation of nuclear power plant considers two distinct types of structural failure, local failure and global failure. In the local failure evaluation, considered projectiles can be divided as internal and external projectile according to the impact location, and they also can be divided as rigid and soft projectile according to the deformation level after impact. Frequently considered projectiles are aircraft engine, tornado, and turbine projectile. When the speed and weight of the projectiles are considered, the most influential projectile is aircraft engine, which is one of the soft projectiles. Sugano et al. performed impact test using an engine model projectile, which is derived from GE-J79 engine and concentrated mass-spring model idealization. Kojima and Sugano et al. demonstrated from their experiments that steel liner on the rear side of the concrete wall reduces impact induced damage and suppresses debris scattering. Chung et al. performed comparison study of various formulae suggested for local damage evaluation using previously performed numerous local impact test results. Also, they validated a methodology of numerical analysis for impact simulation using LS-DYNA. Previously suggested formulae and research results do not consider the effect of liner plate or curved shape of the containment building walls on the local damage. In this research, flat wall and curved wall are individually modeled using the same curvature of nuclear power plants, and the effects of curvature and liner plates on the local damage are analytically investigated

Evaluation of the damage of cell wall and cell membrane for various extracellular polymeric substance extractions of activated sludge.

Science.gov (United States)

Guo, Xuesong; Liu, Junxin; Xiao, Benyi

2014-10-20

Extracellular polymeric substances (EPS) are susceptible to contamination by intracellular substances released during the extraction of EPS owing to the damage caused to microbial cell structures. The damage to cell walls and cell membranes in nine EPS extraction processes of activated sludge was evaluated in this study. The extraction of EPS (including proteins, carbohydrates and DNA) was the highest using the NaOH extraction method and the lowest using formaldehyde extraction. All nine EPS extraction methods in this study resulted in cell wall and membrane damage. The damage to cell walls, evaluated by 2-keto-3-deoxyoctonate (KDO) and N-acetylglucosamine content changes in extracted EPS, was the most significant in the NaOH extraction process. Formaldehyde extraction showed a similar extent of damage to cell walls to those detected in the control method (centrifugation), while those in the formaldehyde-NaOH and cation exchange resin extractions were slightly higher than those detected in the control. N-acetylglucosamine was more suitable than KDO for the evaluation of cell wall damage in the EPS extraction of activated sludge. The damage to cell membranes was characterized by two fluorochromes (propidium iodide and FITC Annexin V) with flow cytometry (FCM) measurement. The highest proportion of membrane-damaged cells was detected in NaOH extraction (26.54% of total cells) while membrane-damaged cells comprised 8.19% of total cells in the control. Copyright © 2014 Elsevier B.V. All rights reserved.

Non-linear analysis of the behaviour of a thin and squat reinforced concrete wall on a seismic table

International Nuclear Information System (INIS)

Mazars, J.; Ghavamian, S.; Ile, N.; Reynouard, J.M.

1998-01-01

This work concerns the modeling and analysis of the seismic behaviour of a thin reinforced concrete wall using an experiment performed by the NUPEC (Nuclear Power Engineering Corporation) Japanese organisation with the Tadotsu seismic table. The wall with a height/width ratio close to 1, has its extremities stiffened and its base embedded. The wall, loaded on its top with a 122 t weight, is submitted to several seismic levels up to its collapse. A non-linear seismic analysis and different 2-D and 3-D finite elements modeling were used to simulate the behaviour of the structure submitted to a strong dynamic shear. The results presented in this paper belong to the ''Seismic Shear Wall Standard Problem'' benchmark jointly organized the NUPEC and OECD organizations. (J.S.)

Aggregate-cement paste transition zone properties affecting the salt-frost damage of high-performance concretes

International Nuclear Information System (INIS)

Cwirzen, Andrzej; Penttala, Vesa

2005-01-01

The influence of the cement paste-aggregate interfacial transition zone (ITZ) on the frost durability of high-performance silica fume concrete (HPSFC) has been studied. Investigation was carried out on eight non-air-entrained concretes having water-to-binder (W/B) ratios of 0.3, 0.35 and 0.42 and different additions of condensed silica fume. Studies on the microstructure and composition of the cement paste have been made by means of environmental scanning electron microscope (ESEM)-BSE, ESEM-EDX and mercury intrusion porosimetry (MIP) analysis. The results showed that the transition zone initiates and accelerates damaging mechanisms by enhancing movement of the pore solution within the concrete during freezing and thawing cycles. Cracks filled with ettringite were primarily formed in the ITZ. The test concretes having good frost-deicing salt durability featured a narrow transition zone and a decreased Ca/Si atomic ratio in the transition zone compared to the bulk cement paste. Moderate additions of silica fume seemed to densify the microstructure of the ITZ

Optimization process for thin-walled high performance concrete sandwich panels

DEFF Research Database (Denmark)

Hodicky, Kamil; Hulin, Thomas; Schmidt, Jacob Wittrup

2014-01-01

with the specifications of the design constrains and variables. The tool integrates the processes of HPCSP design, quantity take-off and cost estimation into a single system that would provide different costs for different HPCSP designs. The proposed multi-objective optimisation scheme results into derivation of basic......A Nearly zero energy buildings are to become a requirement as part of the European energy policy. There are many ways of designing nearly zero energy buildings, but there is a lack of knowledge on optimization processes in the sense of structurally and thermally efficient design with an optimal...... economical solution. The present paper aims to provide multi-objective optimisation procedure addressed to structural precast thin-walled High Performance Concrete Sandwich Panels (HPCSP). The research aim is concerned with developing a tool that considers the cost of HPCSP materials along...

Contribution of the Acoustic Emission technique in the understanding and the modelling of the coupling between creep and damage in concrete

International Nuclear Information System (INIS)

Saliba, J.

2012-01-01

In order to design reliable concrete structures, prediction of long term behaviour of concrete is important. In fact, creep deformation can cause mechanical deterioration and cracking, stress redistribution, loss in prestressed members and rarely ruin the structure. The aim of this research is to have a better understanding of the interaction between creep and crack growth in concrete. An experimental investigation on the fracture properties of concrete beams submitted to creep bending tests with high levels of sustained load is reported. The influence of creep on residual capacity and fracture energy of concrete is studied. In parallel, the acoustic emission technique (AE) was used to monitor crack development. The results give wealth information on damage evolution and show a decrease in the width of the fracture process zone (FPZ) characterizing a more brittle behaviour for beams subjected to creep. The AE shows that this may be due to the development of microcracking detected under creep. Based on those experimental results, a mesoscopic numerical study was proposed by coupling a damage model based on the micro-plan theory and a viscoelastic creep model defined by several Kelvin-voigt chains. The numerical results on concrete specimens in tension and in bending confirm the development of microcracks during creep at the mortar-aggregate interface. (author)

Penetration analysis of projectile with inclined concrete target

Directory of Open Access Journals (Sweden)

Kim S.B.

2015-01-01

Full Text Available This paper presents numerical analysis result of projectile penetration with concrete target. We applied dynamic material properties of 4340 steels, aluminium and explosive for projectile body. Dynamic material properties were measured with static tensile testing machine and Hopkinson pressure bar tests. Moreover, we used three concrete damage models included in LS-DYNA 3D, such as SOIL_CONCRETE, CSCM (cap model with smooth interaction and CONCRETE_DAMAGE (K&C concrete models. Strain rate effect for concrete material is important to predict the fracture deformation and shape of concrete, and penetration depth for projectiles. CONCRETE_DAMAGE model with strain rate effect also applied to penetration analysis. Analysis result with CSCM model shows good agreement with penetration experimental data. The projectile trace and fracture shapes of concrete target were compared with experimental data.

Penetration analysis of projectile with inclined concrete target

Science.gov (United States)

Kim, S. B.; Kim, H. W.; Yoo, Y. H.

2015-09-01

This paper presents numerical analysis result of projectile penetration with concrete target. We applied dynamic material properties of 4340 steels, aluminium and explosive for projectile body. Dynamic material properties were measured with static tensile testing machine and Hopkinson pressure bar tests. Moreover, we used three concrete damage models included in LS-DYNA 3D, such as SOIL_CONCRETE, CSCM (cap model with smooth interaction) and CONCRETE_DAMAGE (K&C concrete) models. Strain rate effect for concrete material is important to predict the fracture deformation and shape of concrete, and penetration depth for projectiles. CONCRETE_DAMAGE model with strain rate effect also applied to penetration analysis. Analysis result with CSCM model shows good agreement with penetration experimental data. The projectile trace and fracture shapes of concrete target were compared with experimental data.

Maintenance and preservation of concrete structures. Report 3: Abrasion-erosion resistance of concrete

Science.gov (United States)

Liu, T. C.

1980-07-01

This report describes a laboratory test program on abrasion-erosion resistance of concrete, including the development of a new underwater abrasion-erosion test method. This program was designed to evaluate the relative abrasion-erosion resistance of various materials considered for use in the repair of erosion-damaged concrete structures. The test program encompassed three concrete types (conventional concrete, fiber-reinforced concrete, and polymer concrete); seven aggregate types (limestone, chert, trap rock, quartzite, granite, siliceous gravel, and slag); three principal water-cement rations (0.72, 0.54, and 0.40); and six types of surface treatment (vacuum, polyurethane coating, acrylic mortar coating, epoxy mortar coating, furan resin mortar coating, and iron aggregate topping). A total of 114 specimens made from 41 batches of concrete was tested. Based on the test data obtained, a comprehensive evaluation of the effects of various parameters on the abrasion-erosion resistance of concrete was presented. Materials suitable for use in the repair of erosion-damaged concrete structures were recommended. Additional work to correlate the reported findings with field performance was formulated.

Evaluation of the Influence of Wind-Driven Rain on Moisture in Cellular Concrete Wall Boards

Directory of Open Access Journals (Sweden)

Alsabry A.

2017-08-01

Full Text Available The non-stationary moisture level of a cellular concrete wall board in a heated utility building located in the northern part of the town of Brest (Belarus, depending on the climatic influence, was assessed in this work. The results were obtained both in a calculation experiment and a physical test. It was observed that the main reason for the high moisture levels in cellular concrete is wind-driven rain intensifying the process of free capillary moisture transfer. A comparative analysis of the results of the physical test and the calculation experiment showed that the THSS software elaborated by the authors was able to predict the actual moisture levels of the shielding structure under study accurately enough when precise data concerning the thermal and physical characteristics of the materials as well as the occurring climatic influences were submitted.

Evaluation of the Influence of Wind-Driven Rain on Moisture in Cellular Concrete Wall Boards

Science.gov (United States)

Alsabry, A.; Nikitsin, V. I.; Kofanov, V. A.; Backiel-Brzozowska, B.

2017-08-01

The non-stationary moisture level of a cellular concrete wall board in a heated utility building located in the northern part of the town of Brest (Belarus), depending on the climatic influence, was assessed in this work. The results were obtained both in a calculation experiment and a physical test. It was observed that the main reason for the high moisture levels in cellular concrete is wind-driven rain intensifying the process of free capillary moisture transfer. A comparative analysis of the results of the physical test and the calculation experiment showed that the THSS software elaborated by the authors was able to predict the actual moisture levels of the shielding structure under study accurately enough when precise data concerning the thermal and physical characteristics of the materials as well as the occurring climatic influences were submitted.

Experimental assessment of borehole wall drilling damage in basaltic rocks

International Nuclear Information System (INIS)

Fuenkajorn, K.; Daemen, J.J.K.

1986-06-01

Ring tension tests, permeability tests, and microscopic fracture studies have been performed to investigate the borehole damage induced at low confining pressure by three drilling techniques (diamond, percussion and rotary). Specimens are drilled with three hole sizes (38, 76, and 102 mm diameter) in Pomona basalt and Grande basaltic andesite. The damaged zone is characterized in terms of fractures and fracture patterns around the hole, and in terms of tensile strength reduction of the rock around the holes. Experimental results show that the thickness of the damaged zone around the hole ranges from 0.0 to 1.7 mm. A larger drill bit induces more wall damage than does a smaller one. Different drilling techniques show different damage characteristics (intensity and distribution). Damage characteristics are governed not only by drilling parameters (bit size, weight on bit, rotational speed, diamond radius, and energy), but also by properties of the rock. The weaker rock tends to show more intense damage than does the stronger one. Cracks within grains or cleavage fractures are predominant in slightly coarser grained rock (larger than 0.5 mm grain size) while intergranular cracks are predominant in very fine grained rock (smaller than 0.01 mm grain size). The damaged zones play no significant role in the flow path around a borehole plug

Study of waterline corrosion on the carbon steel liner cast in concrete at the condensation pool. I. Literature review II. Study of the risk for waterline corrosion on the steel liner cast in concrete at the cylinder wall at Barsebaeck 1

International Nuclear Information System (INIS)

Sederholm, Bror; Kalinowski, Mariusz; Eistrat, Kaija

2009-02-01

The reactor containment in Swedish BWR-type nuclear power plants consists of an inner cylinder-shaped container of stainless steel, with an outer liner of carbon steel about 300 mm from the stainless steel container, both cast in concrete. If water leaks from the inner stainless steel container into the concrete, the risk of corrosion on the carbon steel liner may be increased by the presence of a waterline, and voids in the concrete at the metal surface. The first part of the report is a survey of published information regarding waterline corrosion and the effect of wholly or partly liquid-filled voids at a steel surface cast in concrete. The second part is a report on the investigations of the corrosion status of the steel liner on the inside of the reactor containment at the Barsebaeckverket 1 plant and of the laboratory investigations of the concrete samples that were taken from the reactor containment wall. The waterline corrosion effect is caused by local differences in environmental factors at the water/air border, primarily the supply of oxygen (air), which allows corrosion cells similar to galvanic cells to be set up. On a vertical, partly immersed steel structure the corrosion rate largely varies with the supply of oxygen, with the highest corrosion rate at or immediately above the waterline, where the supply of both oxygen (air) and electrolyte is good. The relative corrosion rates around the waterline may be modified by the action of various concentration cells. Waterline effects due to aeration cells or other concentration cells have been shown to increase the risk for corrosion damage locally, even when the overall corrosion rate does not increase, since corrosion is concentrated to a smaller area and may have a more localised character. Waterline conditions can also develop at a cast-in metal surface inside partly water-filled voids in the concrete. Voids as such at a concrete/metal interface, leaving metal without adhering concrete, have also been

Investigation of radial shear in the wall-base juncture of a 1:4 scale prestressed concrete containment vessel model

Energy Technology Data Exchange (ETDEWEB)

Dameron, R.A.; Rashid, Y.R. [ANATECH Corp., San Diego, CA (United States); Luk, V.K.; Hessheimer, M.F. [Sandia National Labs., Albuquerque, NM (United States)

1998-04-01

Construction of a prestressed concrete containment vessel (PCCV) model is underway as part of a cooperative containment research program at Sandia National Laboratories. The work is co-sponsored by the Nuclear Power Engineering Corporation (NUPEC) of Japan and US Nuclear Regulatory Commission (NRC). Preliminary analyses of the Sandia 1:4 Scale PCCV Model have determined axisymmetric global behavior and have estimated the potential for failure in several areas, including the wall-base juncture and near penetrations. Though the liner tearing failure mode has been emphasized, the assumption of a liner tearing failure mode is largely based on experience with reinforced concrete containments. For the PCCV, the potential for shear failure at or near the liner tearing pressure may be considerable and requires detailed investigation. This paper examines the behavior of the PCCV in the region most susceptible to a radial shear failure, the wall-basemat juncture region. Prediction of shear failure in concrete structures is a difficult goal, both experimentally and analytically. As a structure begins to deform under an applied system of forces that produce shear, other deformation modes such as bending and tension/compression begin to influence the response. Analytically, difficulties lie in characterizing the decrease in shear stiffness and shear stress and in predicting the associated transfer of stress to reinforcement as cracks become wider and more extensive. This paper examines existing methods for representing concrete shear response and existing criteria for predicting shear failure, and it discusses application of these methods and criteria to the study of the 1:4 scale PCCV.

Investigation of radial shear in the wall-base juncture of a 1:4 scale prestressed concrete containment vessel model

International Nuclear Information System (INIS)

Dameron, R.A.; Rashid, Y.R.; Luk, V.K.; Hessheimer, M.F.

1998-04-01

Construction of a prestressed concrete containment vessel (PCCV) model is underway as part of a cooperative containment research program at Sandia National Laboratories. The work is co-sponsored by the Nuclear Power Engineering Corporation (NUPEC) of Japan and US Nuclear Regulatory Commission (NRC). Preliminary analyses of the Sandia 1:4 Scale PCCV Model have determined axisymmetric global behavior and have estimated the potential for failure in several areas, including the wall-base juncture and near penetrations. Though the liner tearing failure mode has been emphasized, the assumption of a liner tearing failure mode is largely based on experience with reinforced concrete containments. For the PCCV, the potential for shear failure at or near the liner tearing pressure may be considerable and requires detailed investigation. This paper examines the behavior of the PCCV in the region most susceptible to a radial shear failure, the wall-basemat juncture region. Prediction of shear failure in concrete structures is a difficult goal, both experimentally and analytically. As a structure begins to deform under an applied system of forces that produce shear, other deformation modes such as bending and tension/compression begin to influence the response. Analytically, difficulties lie in characterizing the decrease in shear stiffness and shear stress and in predicting the associated transfer of stress to reinforcement as cracks become wider and more extensive. This paper examines existing methods for representing concrete shear response and existing criteria for predicting shear failure, and it discusses application of these methods and criteria to the study of the 1:4 scale PCCV

Design and testing of corrosion damaged prestressed concrete joists: the Pescara Benchmark

International Nuclear Information System (INIS)

Di Evangelista, A; De Leonardis, A; Valente, C; Zuccarino, L

2011-01-01

An experimental campaign named the Pescara benchmark and devoted to study the dynamic behaviour of corroded p.c. joists has been conducted. The steel corrosion reduces the area of the reinforcement and causes cracking of concrete so that r/c members are subjected to loss of strength and stiffness. It is of interest to evaluate the corrosion level at which the damage can be detected through signal processing procedures and how close such level is to the r/c member safety limits. Joists of current industrial production having different steel to concrete ratios are tested in different laboratory conditions. Dynamic tests involve either free vibrations and forced vibrations due to a moving mass simulating actual traffic loads in railway bridges. The paper discusses the rationale of the tests including the set up of the artificial corrosion, the static characterization of the joist and the dynamic tests in the different stages of corrosion experienced.

Concrete structures

CERN Document Server

Setareh, Mehdi

2017-01-01

This revised, fully updated second edition covers the analysis, design, and construction of reinforced concrete structures from a real-world perspective. It examines different reinforced concrete elements such as slabs, beams, columns, foundations, basement and retaining walls and pre-stressed concrete incorporating the most up-to-date edition of the American Concrete Institute Code (ACI 318-14) requirements for the design of concrete structures. It includes a chapter on metric system in reinforced concrete design and construction. A new chapter on the design of formworks has been added which is of great value to students in the construction engineering programs along with practicing engineers and architects. This second edition also includes a new appendix with color images illustrating various concrete construction practices, and well-designed buildings. The ACI 318-14 constitutes the most extensive reorganization of the code in the past 40 years. References to the various sections of the ACI 318-14 are pro...

A constitutive model for concrete under dynamic loading

International Nuclear Information System (INIS)

Suaris, W.; Shah, S.P.

1983-01-01

A continuous damage theory for the quasistatic and dynamic behaviour of concrete is presented. The continuous damage theory is rational choice for use in predicing the dynamic behaviour of concrete as the strain-rate effects that have been observed for concrete can to a large extent be attributed to the rate-sensitivity of the microcracking process. A vectorial representation is adopted for the damage to account for the planar nature of the microcracks in concrete. Damage is treated as an internal state variable influencing the free energy of the material and the constitutive equations and the damage evolution equations are derived consistently using thermodynamic considerations. The developed constitutive model is then calibrated by using test results in flexure and compression over a range of strain-rates. The constitutive model is also shown to be capable of predicting certain other experimentally observed characteristics of the dynamic response of concrete. (orig./HP)

Experimental studies on local damage of reinforced concrete structures by the impact deformable missiles-Part 2

International Nuclear Information System (INIS)

Esashi, Y.; Ohnuma, H.; Ito, C.; Shirai, K.

1989-01-01

In order to establish a rational method of determining the local damage to reinforced concrete structures due to the impact of aircraft engine missiles, three types of impact tests with different scales have been planned and executed. In this paper, results and discussion of the intermediate-scale tests are presented

Homogenised constitutive model dedicated to reinforced concrete plates subjected to seismic solicitations

International Nuclear Information System (INIS)

Combescure, Christelle

2013-01-01

Safety reassessments are periodically performed on the EDF nuclear power plants and the recent seismic reassessments leaded to the necessity of taking into account the non-linear behaviour of materials when modeling and simulating industrial structures of these power plants under seismic solicitations. A large proportion of these infrastructures is composed of reinforced concrete buildings, including reinforced concrete slabs and walls, and literature seems to be poor on plate modeling dedicated to seismic applications for this material. As for the few existing models dedicated to these specific applications, they present either a lack of dissipation energy in the material behaviour, or no micromechanical approach that justifies the parameters needed to properly describe the model. In order to provide a constitutive model which better represents the reinforced concrete plate behaviour under seismic loadings and whose parameters are easier to identify for the civil engineer, a constitutive model dedicated to reinforced concrete plates under seismic solicitations is proposed: the DHRC (Dissipative Homogenised Reinforced Concrete) model. Justified by a periodic homogenisation approach, this model includes two dissipative phenomena: damage of concrete matrix and internal sliding at the interface between steel rebar and surrounding concrete. An original coupling term between damage and sliding, resulting from the homogenisation process, induces a better representation of energy dissipation during the material degradation. The model parameters are identified from the geometric characteristics of the plate and a restricted number of material characteristics, allowing a very simple use of the model. Numerical validations of the DHRC model are presented, showing good agreement with experimental behaviour. A one dimensional simplification of the DHRC model is proposed, allowing the representation of reinforced concrete bars and simplified models of rods and wire mesh

Shrinkage deformation of cement foam concrete

Science.gov (United States)

Kudyakov, A. I.; Steshenko, A. B.

2015-01-01

The article presents the results of research of dispersion-reinforced cement foam concrete with chrysotile asbestos fibers. The goal was to study the patterns of influence of chrysotile asbestos fibers on drying shrinkage deformation of cement foam concrete of natural hardening. The chrysotile asbestos fiber contains cylindrical fiber shaped particles with a diameter of 0.55 micron to 8 microns, which are composed of nanostructures of the same form with diameters up to 55 nm and length up to 22 microns. Taking into account the wall thickness, effective reinforcement can be achieved only by microtube foam materials, the so- called carbon nanotubes, the dimensions of which are of power less that the wall pore diameter. The presence of not reinforced foam concrete pores with perforated walls causes a decrease in its strength, decreases the mechanical properties of the investigated material and increases its shrinkage. The microstructure investigation results have shown that introduction of chrysotile asbestos fibers in an amount of 2 % by weight of cement provides the finely porous foam concrete structure with more uniform size closed pores, which are uniformly distributed over the volume. This reduces the shrinkage deformation of foam concrete by 50%.

Partition wall structure in spent fuel storage pool and construction method for the partition wall

International Nuclear Information System (INIS)

Izawa, Masaaki

1998-01-01

A partitioning wall for forming cask pits as radiation shielding regions by partitioning inside of a spent fuel storage pool is prepared by covering both surface of a concrete body by shielding metal plates. The metal plate comprises opposed plate units integrated by welding while sandwiching a metal frame as a reinforcing material for the concrete body, the lower end of the units is connected to a floor of a pool by fastening members, and concrete is set while using the metal plate of the units as a frame to form the concrete body. The shielding metal plate has a double walled structure formed by welding a lining plate disposed on the outer surface of the partition wall and a shield plate disposed to the inner side. Then the term for construction can be shortened, and the capacity for storing spent fuels can be increased. (N.H.)

Experimental testing of post-tensioned concrete girders instrumented with optical fibre gratings

Science.gov (United States)

Matthys, S.; Taerwe, L.

2005-05-01

The integration of optical fibre strain sensors in concrete structures in order to measure deformations has proven to be successful in several applications. Examples of monitored structures by the Magnel Laboratory for Concrete Research are a concrete girder bridge over the Ring Canal by Ghent, a Quay wall at the Ring Canal and a trough girder containing a railway track of a bridge [1,2]. Based on a joint research project the feasibility of integrating Bragg grating sensors in concrete in order to statically and dynamically monitor 17.6 m long prestressed concrete girders has been investigated. During the project 3 post-tensioned concrete girders were tested, submitting them to static and dynamic loading conditions and monitoring the structural behavior with several types of measuring devices, including accelerometers, Bragg gratings, Fabry-Perot gratings, deformeters, crack microscopes, etc. The obtained test results demonstrate the feasibility of optical strain sensors for both static and dynamic measurements. Though it was demonstrated, in the case of dynamic monitoring, that optical strain measurements can be used to directly measure the modal strains, the project also demonstrated that for prestressed concrete the variation in dynamic parameters was insufficient for adequate dynamic monitoring and related damage diagnostics.

Microstructural Analysis on the NPP Concrete under Initial Frost Damage

International Nuclear Information System (INIS)

Koh, Kyung Teak; Park, Chun Jin; Kim, Si Hwan; Ryu, Gum Sung

2012-01-01

The concrete should secure the quality over certain standard regardless of construction location and period. Especially, because the fly ash (FA) is used in nuclear power plant concrete as a concrete substitute by 20%, the concrete using FA is hugely influenced according to temperature and humidity in terms of constructability, strength and durability due to the material properties. Accordingly, when building the nuclear power plant under various environmental conditions, it's important to secure the concrete quality equally through applying an appropriate curing method to control temperature and humidity. Although various according to concrete materials and mixture, the concrete-freezing temperature is usually known as about -0.5∼-3.0 .deg. C. In case the concrete is frozen early under the condition that the strength has not been sufficiently developed yet, because the volume expansion caused by the frozen free moisture inside concrete results in the relaxation and destruction of structure, the strength, watertightness and durability of the concrete get lower drastically even after being hardened. Accordingly, this study tried to review the quality of nuclear power plant concrete under early freezing through measuring strength, SEM and XRD after making the concrete frozen over certain standard in the early curing with targeting the nuclear power plant (NPP) concrete replaced with FA 20%

Development of probabilistic fatigue curve for asphalt concrete based on viscoelastic continuum damage mechanics

Directory of Open Access Journals (Sweden)

Himanshu Sharma

2016-07-01

Full Text Available Due to its roots in fundamental thermodynamic framework, continuum damage approach is popular for modeling asphalt concrete behavior. Currently used continuum damage models use mixture averaged values for model parameters and assume deterministic damage process. On the other hand, significant scatter is found in fatigue data generated even under extremely controlled laboratory testing conditions. Thus, currently used continuum damage models fail to account the scatter observed in fatigue data. This paper illustrates a novel approach for probabilistic fatigue life prediction based on viscoelastic continuum damage approach. Several specimens were tested for their viscoelastic properties and damage properties under uniaxial mode of loading. The data thus generated were analyzed using viscoelastic continuum damage mechanics principles to predict fatigue life. Weibull (2 parameter, 3 parameter and lognormal distributions were fit to fatigue life predicted using viscoelastic continuum damage approach. It was observed that fatigue damage could be best-described using Weibull distribution when compared to lognormal distribution. Due to its flexibility, 3-parameter Weibull distribution was found to fit better than 2-parameter Weibull distribution. Further, significant differences were found between probabilistic fatigue curves developed in this research and traditional deterministic fatigue curve. The proposed methodology combines advantages of continuum damage mechanics as well as probabilistic approaches. These probabilistic fatigue curves can be conveniently used for reliability based pavement design. Keywords: Probabilistic fatigue curve, Continuum damage mechanics, Weibull distribution, Lognormal distribution

Comparative performance of various smart aggregates during strength gain and damage states of concrete

International Nuclear Information System (INIS)

Saravanan, T Jothi; Balamonica, K; Priya, C Bharathi; Gopalakrishnan, N; Reddy, A Likhith

2015-01-01

Information regarding the early strength gain of fresh concrete determines the time for the removal of form work and the transfer of pre-stressing forces for pre-stressed concrete. An ultrasonic based non-destructive evaluation of early strength gain may not work for concrete in fluid and semi-solid phases. A possible alternative is a lead zirconate titanate (PZT)-based smart aggregate embedded in concrete, which can evaluate the micro-structural and rheological properties right from the fluid phase. A set of five smart aggregates embedded in a concrete cube were investigated for their suitability to evaluate electromechanical impedance (EMI) signatures. Cubes were loaded to failure and the EMI during progressive strength loss under compressive loads was studied. To show the generalized applicability of this, experimental results for the performance of typical smart aggregates on a larger specimen, namely a concrete beam, are also discussed. Different statistical metrics were examined computationally on a three peak admittance curve with a parametric variation of stiffness, damping and simple scaling. The root mean square deviation (RMSD), mean absolute percentage deviation (MAPD), cross correlation (CC) and modified cross correlation (MCC) were investigated, in addition to the rate of change of the RMSD. Variations between the reference and modified states were studied. Both stiffness and mass gains occur for the smart aggregates, resulting in an increase or decrease of frequency and amplitude peaks due to progressive C-S-H gel formation. The trend of increasing stiffness and the consequent rightward shift of the resonant peaks and decrease of damping, with the consequent upward shift of amplitudes that happens during curing and strength gain, was observed to be reversed during the application of damaging loads. (paper)

RILEM recommendations for the prevention of damage by alkali-aggregate reactions in new concrete structures state-of-the-art report of the RILEM technical committee 219-ACS

CERN Document Server

Sims, Ian

2016-01-01

This book contains the full set of RILEM Recommendations which have been produced to enable engineers, specifiers and testing houses to design and produce concrete which will not suffer damage arising from alkali reactions in the concrete. There are five recommended test methods for aggregates (designated AAR-1 to AAR-5), and an overall recommendation which describes how these should be used to enable a comprehensive aggregate assessment (AAR-0). Additionally, there are two Recommended International Specifications for concrete (AAR-7.1 & 7.2) and a Preliminary International Specification for dams and other hydro structures (AAR-7.3), which describe how the aggregate assessment can be combined with other measures in the design of the concrete to produce a concrete with a minimised risk of developing damage from alkali-aggregate reactions.

In-Plane Strengthening Effect of Prefabricated Concrete Walls on Masonry Structures: Shaking Table Test

Directory of Open Access Journals (Sweden)

Weiwei Li

2017-01-01

Full Text Available The improvement effect of a new strengthening strategy on dynamic action of masonry structure, by installing prefabricated concrete walls on the outer facades, is validated by shaking table test presented in this paper. We carried out dynamic tests of two geometrically identical five-story reduced scaled models, including an unstrengthened and a strengthened masonry model. The experimental analysis encompasses seismic performances such as cracking patterns, failure mechanisms, amplification factors of acceleration, and displacements. The results show that the strengthened masonry structure shows much more excellent seismic capacity when compared with the unstrengthened one.

Energy conservation and recycling of wall and concrete may give large environmental profits in the construction industry. Environment taken seriously

International Nuclear Information System (INIS)

Nestvold, Veslemoey

2000-01-01

The article reviews some results from the 5 year project ''Oekobygg'', started in 1998, which studies energy conservation and recycling of wall and concrete in the construction industry. Reduction of the waste amounts, industrial recycling and ''smart housing'' are discussed. Recycling will result in the largest environmental benefits

Test of workability of concrete for PCCV

International Nuclear Information System (INIS)

Fujii, Tadayoshi; Nagase, Tetsuo; Yoshimori, Yoshinari

1987-01-01

The construction of the prestressed concrete containment vessel (PCCV) for Tsuruga No.2 plant of Japan Atomic Power Co. is the first case in Japan, and since the concrete having high strength and low slump is placed, the test of concrete placing by taking out a part of a full size test wall and the test of workability regarding the vibration compacting of concrete using a vibrator were carried out beforehand, and the results were reflected to the actual construction works. In this report, the workability test on the concrete is described. As difficulty is expected in the actual placing of the concrete having high strength and low slump, for the purpose of confirming the property of placing of the concrete in the cylindrical wall, and obtaining the basic data for the management of the actual concrete works and the quality control, the concrete placing test was carried out. At the time of concrete placing, the compacting of concrete is important, therefore, the basic data on the effect that the type, diameter, vibrating time and vibration propagation range of vibrators exert on the compacting of concrete were obtained, and reflected to the actual compacting. The purpose, testing method, results and the reflection to the actual works of these tests are reported. (Kako, I.)

Analysis and optimization of the heat-insulating light concrete hollow brick walls design by the finite element method

International Nuclear Information System (INIS)

Coz Diaz, J.J. del; Garcia Nieto, P.J.; Betegon Biempica, C.; Prendes Gero, M.B.

2007-01-01

Department of Public Works, owners and building proprietors are demanding high-capacity heat-insulating exterior masonry components specifically for further energy savings. For housing and industrial structures there is also a great interest in light building materials with good physical material behaviour, with respect to an energy conscious and ecological design, which fulfils all strength and serviceability requirements. The major variables influencing the thermal conductivity of masonry materials are illustrated in this work by taking blocks made from no-fine lightweight concrete and different mortar properties. The finite element method (FEM) is used for finding accurate solutions of the heat transfer equation for five different light concrete hollow brick walls. Mathematically, the non-linearity is due to the radiation boundary condition inside the inner recesses of the bricks. The conduction and convection phenomena are taking into account in this study for three different values of the mortar conductivity and three different values for the bricks. Optimization of the walls is carried out from the finite element analysis of five hollow brick geometries by means of the mass overall thermal efficiency and the equivalent thermal conductivity. Finally, conclusions of this work are exposed

Analysis and optimization of the heat-insulating light concrete hollow brick walls design by the finite element method

Energy Technology Data Exchange (ETDEWEB)

Coz Diaz, J.J. del; Betegon Biempica, C.; Prendes Gero, M.B. [Edificio Departamental Viesques, No 7, 33204 Gijon (Asturias) (Spain); Garcia Nieto, P.J. [Departamento de Matematicas, Facultad de Ciencias, C/Calvo Sotelo s/n, 33007 Oviedo (Asturias) (Spain)

2007-06-15

Department of Public Works, owners and building proprietors are demanding high-capacity heat-insulating exterior masonry components specifically for further energy savings. For housing and industrial structures there is also a great interest in light building materials with good physical material behaviour, with respect to an energy conscious and ecological design, which fulfils all strength and serviceability requirements. The major variables influencing the thermal conductivity of masonry materials are illustrated in this work by taking blocks made from no-fine lightweight concrete and different mortar properties. The finite element method (FEM) is used for finding accurate solutions of the heat transfer equation for five different light concrete hollow brick walls. Mathematically, the non-linearity is due to the radiation boundary condition inside the inner recesses of the bricks. The conduction and convection phenomena are taking into account in this study for three different values of the mortar conductivity and three different values for the bricks. Optimization of the walls is carried out from the finite element analysis of five hollow brick geometries by means of the mass overall thermal efficiency and the equivalent thermal conductivity. Finally, conclusions of this work are exposed. (author)

STRUCTURAL SOLUTIONS AND SPECIAL FEATURES OF THE THERMAL PROTECTION ANALYSIS OF EXTERIOR WALLS OF BUILDINGS MADE OF AUTOCLAVED GAS-CONCRETE BLOCKS

Directory of Open Access Journals (Sweden)

Bedov Anatolij Ivanovich

2012-10-01

Full Text Available Relevant structural solutions, physical and mechanical characteristics, coefficients of thermal conductivity for exterior masonry walls made of autoclaved gas-concrete blocks are provided in the article. If a single-layer wall is under consideration, an autoclaved gas-concrete block is capable of performing the two principal functions of a shell structure, including the function of thermal protection and the bearing function. The functions are performed simultaneously. Therefore, the application of the above masonry material means the design development and erection of exterior walls of residential buildings noteworthy for their thermal efficiency. In the event of frameless structures, the height of the residential building in question may be up to 5 stories, while the use of a monolithic or a ready-made frame makes it possible to build high-rise buildings, and the number of stories is not limited in this case. If the average block density is equal to 400…500 kilograms per cubic meter, the designed wall thickness is to be equal to 400 mm. Its thermal resistance may be lower than the one set in the event of the per-element design of the thermal protection (Rreq = 3.41 м2 C/Watt, in Ufa, although it will meet the requirements of the applicable regulations if per-unit power consumption rate is considered.

Coupling creep and damage in concrete under high sustained loading: Experimental investigation on bending beams and application of Acoustic Emission technique

Directory of Open Access Journals (Sweden)

Grondin F.

2010-06-01

Full Text Available Creep and damage in concrete govern the long-term deformability of concrete. Thus, it is important to understand the interaction between creep and damage in order to design reliable civil engineering structures subjected to high level loading during a long time. Many investigations have been performed on the influence of concrete mixture, the effect of the bond between the matrix and the aggregates, temperature, aging and the size effect on the cracking mechanism and fracture parameters of concrete. But there is a lack of results on the influence of the creep loading history. In the present paper, an experimental investigation on the fracture properties of concrete beams submitted to three point bending tests with high levels of sustained load that deals with creep is reported. The results aim first to investigate the ranges of variation of the time response due to creep damage coupled effects under constant load and secondly to evaluate the residual capacity after creep. For this purpose a series of tests were carried out on geometrically similar specimens of size 100x200x800mm with notch to depth ratio of 0.2 in all the test specimens. The exchange of moisture was prevented and beams were subjected to a constant load of 70% and 90% of the maximum capacity. Three point bending test were realized on specimen at the age of 28 days to determine the characteristics of concrete and the maximum load so we could load the specimens in creep. Threepoint bend creep tests were performed on frames placed in a climate controlled chamber [1]. Then after four months of loading, the beams subjected to creep were removed from the creep frames and then immediately subjected to three-point bending test loading up to failure with a constant loading rate as per RILEM-FMC 50 recommendations. The residual capacity on the notched beams and the evolution of the characteristics of concrete due to the basic creep was considered. The results show that sustained loading

Coupling creep and damage in concrete under high sustained loading: Experimental investigation on bending beams and application of Acoustic Emission technique

Science.gov (United States)

Saliba, J.; Loukili, A.; Grondin, F.

2010-06-01

Creep and damage in concrete govern the long-term deformability of concrete. Thus, it is important to understand the interaction between creep and damage in order to design reliable civil engineering structures subjected to high level loading during a long time. Many investigations have been performed on the influence of concrete mixture, the effect of the bond between the matrix and the aggregates, temperature, aging and the size effect on the cracking mechanism and fracture parameters of concrete. But there is a lack of results on the influence of the creep loading history. In the present paper, an experimental investigation on the fracture properties of concrete beams submitted to three point bending tests with high levels of sustained load that deals with creep is reported. The results aim first to investigate the ranges of variation of the time response due to creep damage coupled effects under constant load and secondly to evaluate the residual capacity after creep. For this purpose a series of tests were carried out on geometrically similar specimens of size 100x200x800mm with notch to depth ratio of 0.2 in all the test specimens. The exchange of moisture was prevented and beams were subjected to a constant load of 70% and 90% of the maximum capacity. Three point bending test were realized on specimen at the age of 28 days to determine the characteristics of concrete and the maximum load so we could load the specimens in creep. Threepoint bend creep tests were performed on frames placed in a climate controlled chamber [1]. Then after four months of loading, the beams subjected to creep were removed from the creep frames and then immediately subjected to three-point bending test loading up to failure with a constant loading rate as per RILEM-FMC 50 recommendations. The residual capacity on the notched beams and the evolution of the characteristics of concrete due to the basic creep was considered. The results show that sustained loading had a strengthening

A coupled carbonation-rust formation mechanical damage model for steel corrosion in reinforced concrete

International Nuclear Information System (INIS)

Nguyen, Huyen; Bary, B.; L'Hostis, Valerie; DeLarrard, T.

2014-01-01

This paper aims at presenting a strategy to simulate the corrosion of steel reinforcement due to carbonation of concrete in atmospheric environment. We propose a model coupling drying, carbonation, diffusion of oxygen, formation of rust and mechanics to describe these phenomena. The rust layer is assumed to be composed of two sub-layers with different elastic modulus. An unstable layer with a low modulus (from 0.1 to 5 GPa) is located next to the transformed medium, and another more stable one with a higher modulus (from 100 to 150 GPa) at the interface with steel reinforcement. This model is applied to a numerical meso-structure composed of 4 phases: mortar matrix, randomly distributed aggregates, steel rebar and rust layers to underline the effect of aggregates on damage initiation and corresponding crack pattern of concrete cover. (authors)

29 CFR 1926.704 - Requirements for precast concrete.

Science.gov (United States)

2010-07-01

... 29 Labor 8 2010-07-01 2010-07-01 false Requirements for precast concrete. 1926.704 Section 1926..., DEPARTMENT OF LABOR (CONTINUED) SAFETY AND HEALTH REGULATIONS FOR CONSTRUCTION Concrete and Masonry Construction § 1926.704 Requirements for precast concrete. (a) Precast concrete wall units, structural framing...

Damage of first wall materials in fusion reactors under nonstationary thermal effects

International Nuclear Information System (INIS)

Maslaev, S.A.; Platonov, Yu.M.; Pimenov, V.N.

1991-01-01

The temperature distribution in the first wall of a fusion reactor was calculated for nonstationary thermal effects of the type of plasma destruction or the flow of 'running electrons' taking into account the melting of the surface layer of the material. The thickness of the resultant damaged layer in which thermal stresses were higher than the tensile strength of the material is estimated. The results were obtained for corrosion-resisting steel, aluminium and vanadium. Flowing down of the molten layer of the material of the first wall is calculated. (author)

Steel plates and concrete filled composite shear walls related nuclear structural engineering: Experimental study for out-of-plane cyclic loading

International Nuclear Information System (INIS)

Li, Xiaohu; Li, Xiaojun

2017-01-01

Based on the program of CAP1400 nuclear structural engineering, the out-of-plane seismic behavior of steel plate and concrete infill composite shear walls (SCW) was investigated. 6 1/5 scaled specimens were conducted which consist of 5 SCW specimens and 1 reinforced concrete (RC) specimen. The specimens were tested under out-of-plane cyclic loading. The effect of the thickness of steel plate, vertical load and the strength grade of concrete on the out-of-plane seismic behavior of SCW were analyzed. The results show that the thickness of steel plate and vertical load have great influence on the ultimate bearing capacity and lateral stiffness, however, the influence of the strength grade of concrete was little within a certain range. SCW is presented to have a better ultimate capacity and lateral stiffness but have worse ductility in failure stage than that of RC. Based on the experiment, the cracking load of concrete infill SCW was analyzed in theory. The modified calculation formula of the cracking load was made, the calculated results showed good agreement with the test results. The formula can be used as the practical design for the design of cracking loads.

Steel plates and concrete filled composite shear walls related nuclear structural engineering: Experimental study for out-of-plane cyclic loading

Energy Technology Data Exchange (ETDEWEB)

Li, Xiaohu [The College of Architecture and Civil Engineering, Beijing University of Technology, Beijing 100124 (China); Li, Xiaojun, E-mail: beerli@vip.sina.com [The College of Architecture and Civil Engineering, Beijing University of Technology, Beijing 100124 (China); Institute of Geophysics, China Earthquake Administration, Beijing 100081 (China)

2017-04-15

Based on the program of CAP1400 nuclear structural engineering, the out-of-plane seismic behavior of steel plate and concrete infill composite shear walls (SCW) was investigated. 6 1/5 scaled specimens were conducted which consist of 5 SCW specimens and 1 reinforced concrete (RC) specimen. The specimens were tested under out-of-plane cyclic loading. The effect of the thickness of steel plate, vertical load and the strength grade of concrete on the out-of-plane seismic behavior of SCW were analyzed. The results show that the thickness of steel plate and vertical load have great influence on the ultimate bearing capacity and lateral stiffness, however, the influence of the strength grade of concrete was little within a certain range. SCW is presented to have a better ultimate capacity and lateral stiffness but have worse ductility in failure stage than that of RC. Based on the experiment, the cracking load of concrete infill SCW was analyzed in theory. The modified calculation formula of the cracking load was made, the calculated results showed good agreement with the test results. The formula can be used as the practical design for the design of cracking loads.

Application of a clay-slag geopolymer matrix for repairing damaged concrete: Laboratory and industrial-scale experiments

Czech Academy of Sciences Publication Activity Database

Perná, Ivana; Hanzlíček, Tomáš; Boura, P.; Lučaník, A.

2017-01-01

Roč. 59, č. 10 (2017), s. 929-937 ISSN 0025-5300 Institutional support: RVO:67985891 Keywords : blast-furnace slag * geopolymer * scanning electron microscopy (SEM) * damaged concrete repair * long-term monitoring Subject RIV: JJ - Other Materials OBOR OECD: Composites (including laminates, reinforced plastics, cermets, combined natural and synthetic fibre fabrics Impact factor: 0.418, year: 2016

Analysis of a damaged and repaired pre-stressed concrete bridge girder by vehicle impact and effectiveness of repair procedure

OpenAIRE

Domínguez Mayans, Félix

2014-01-01

This thesis aims to study the structural consequences of the damages produced by vehicle impact in a pres-stressed concrete bridge girder and the repair procedure in a real case-study damaged after the bridge was opened to service. From the analysis of the situation of the beam and its damage state, a study of the repair actions carried out on this beam has been analyzed in order to determine the efficiency of the repair and if other alternatives are possible or more efficient. A stat...

Seismic Retrofitting: Reinforced Concrete (RC shear wall versus Reinforcement of RC element by Carbon Fiber Reinforced Polymer (CFRP using PUSHOVER analysis

Directory of Open Access Journals (Sweden)

Yahya RIYAD

2016-12-01

Full Text Available Seismic retrofitting of constructions vulnerable to earthquakes is a current problem of great political and social relevance. During the last sixty years, moderate to severe earthquakes have occurred in Morocco (specifically in Agadir 1960 and Hoceima 2004. Such events have clearly shown the vulnerability of the building stock in particular and of the built environment in general. Hence, it is very much essential to retrofit the vulnerable building to cope up for the next damaging earthquake. In this paper, the focus will be on a comparative study between two techniques of seismic retrofitting, the first one is a reinforcement using carbon fiber reinforced polymer (CFRP applied to RC elements by bonding , and the second one is a reinforcement with a shear wall. For this study, we will use a non-linear static analysis -also known as Pushover analysis - on a reinforced concrete structure consisting of beams and columns, and composed from eight storey with a gross area of 240 m², designed conforming to the Moroccan Seismic code[1].

Compare the difference of architecture design in Hong Kong and Penang – Exterior wall

Directory of Open Access Journals (Sweden)

Liu Wen Tao

2015-12-01

Full Text Available This research focuses on the exterior wall of architecture design of Hong Kong and Penang, it also analyzes how light pollution affects human life. As we know, Hong Kong prefers to use steel to build skyscrapers and middle or high rise buildings. However, Penang prefers to use concrete to do the construction. So, there are some advantages and disadvantages between the glass curtain wall and concrete wall in Hong Kong and Penang. The researcher used 400 samples to determine effect of the glass curtain wall and concrete wall on human life in Hong Kong and Penang separately. The result is light pollution created by glass curtain wall in Hong Kong is a serious problem to residents’ life. The glass curtain wall seriously glaze people’s eyes who drive or walk on the street. Thus, many car accidents were caused by this problem. The concrete wall is more often contaminated by fungus and difficult to clean. But, concrete wall is more natural and green for humans. Therefore, from the sustainable aspect that concrete is more healthy for humans, the previous researchers suggest that if the exterior wall is a mixture of both glass curtain and concrete it will not cause light pollution and will be easily involved in the natural environment.

Calculation on cosmic-ray muon exposure rate in non-walled concrete buildings

International Nuclear Information System (INIS)

Fujitaka, Kazunobu; Abe, Siro

1984-01-01

Computer simulations on the exposure indoors from cosmic ray muons were practiced in the framework of non-scattering and non-cascade assumptions. The model buildings were two-dimensional, rectangular, and were made of a normal concrete. A stratified structure was assumed in each building, where no mezzanine was considered. Walls were not taken into account yet. The distributions of the exposure rates in 26-story buildings were illustrated in contour maps for various sets of parameters. All of them gave basically archlike patterns. Analyses of the results showed that the exposure rate is affected most largely by the floor board thickness. The ceiling height would be an insignificant factor for short buildings. The min/max ratio of the muon exposure rate in a moderate size building was estimated to be more than 0.7. (author)

Effect of the selected seismic energy dissipation capacity on the materials quantity for reinforced concrete walls

Directory of Open Access Journals (Sweden)

José Miguel Benjumea Royero

2017-02-01

Full Text Available Context: Regarding their design of reinforced concrete structural walls, the Colombian seismic design building code allows the engineer to select one of the three seismic energy dissipation capacity (ordinary, moderate, and special depending on the seismic hazard of the site. Despite this, it is a common practice to choose the minor requirement for the site because it is thought that selecting a higher requirement will lead to larger structural materials amounts and, therefore, cost increments.  Method: In this work, an analytical study was performed in order to determine the effect of the selected energy dissipation capacity on the quantity of materials and ductility displacement capacity of R/C walls. The study was done for a region with low seismic hazard, mainly because this permitted to explore and compare the use of the three seismic energy dissipations capacities. The effect of different parameters such as the wall total height and thickness, the tributary loaded area, and the minimum volumetric steel ratio were studied. Results: The total amount of steel required for the walls with moderate and special energy dissipation capacity corresponds, on average, to 77% and 89%, respectively, of the quantity required for walls with minimum capacity. Conclusions: it is possible to achieve reductions in the total steel required weight when adopting either moderated or special seismic energy dissipation instead of the minimum capacity.  Additionally, a significant increment in the seismic ductility displacements capacity of the wall was obtained.

Use of response envelopes for seismic margin assessment of reinforced concrete walls and slabs

Energy Technology Data Exchange (ETDEWEB)

Ile, Nicolas; Frau, Alberto, E-mail: alberto.frau@cea.fr

2017-04-01

Highlights: • Proposal of a method for application of the elliptical envelope to RC shell elements. • Proposal of new algorithms for the seismic margin evaluation for RC shell elements. • Verification of a RC wall 3D structure, using the proposed assessment approach. - Abstract: Seismic safety evaluations of existing nuclear facilities are usually based on the assumption of structural linearity. For the design basis earthquake (DBE), it is reasonable to apply a conventional evaluation of the seismic safety of building structures and carry out a linear elastic analysis to assess the load effects on structural elements. Estimating the seismic capacity of a structural element requires an estimation of the critical combination of responses acting in this structural element and compare this combination with the capacity of the element. By exploiting the response-spectrum-based procedure for predicting the response envelopes in linear structures formulated by Menun and Der Kiureghian (2000a), algorithms are developed for the seismic margin assessment of reinforced concrete shell finite elements. These algorithms facilitate the comparison of the response-spectrum-based envelopes to prescribed capacity surfaces for the purpose of assessing the safety margin of this kind of structures. The practical application of elliptical response envelopes in case of shell finite elements is based on the use of layer models such as those developed by Marti (1990), which transfer the generalized stress field to three layers under the assumption that the two outer layers carry membrane forces and the internal layer carries only the out-of-plane shears. The utility of the assessment approach is discussed with reference to a case study of a 3D structure made of reinforced concrete walls.

Use of response envelopes for seismic margin assessment of reinforced concrete walls and slabs

International Nuclear Information System (INIS)

Ile, Nicolas; Frau, Alberto

2017-01-01

Highlights: • Proposal of a method for application of the elliptical envelope to RC shell elements. • Proposal of new algorithms for the seismic margin evaluation for RC shell elements. • Verification of a RC wall 3D structure, using the proposed assessment approach. - Abstract: Seismic safety evaluations of existing nuclear facilities are usually based on the assumption of structural linearity. For the design basis earthquake (DBE), it is reasonable to apply a conventional evaluation of the seismic safety of building structures and carry out a linear elastic analysis to assess the load effects on structural elements. Estimating the seismic capacity of a structural element requires an estimation of the critical combination of responses acting in this structural element and compare this combination with the capacity of the element. By exploiting the response-spectrum-based procedure for predicting the response envelopes in linear structures formulated by Menun and Der Kiureghian (2000a), algorithms are developed for the seismic margin assessment of reinforced concrete shell finite elements. These algorithms facilitate the comparison of the response-spectrum-based envelopes to prescribed capacity surfaces for the purpose of assessing the safety margin of this kind of structures. The practical application of elliptical response envelopes in case of shell finite elements is based on the use of layer models such as those developed by Marti (1990), which transfer the generalized stress field to three layers under the assumption that the two outer layers carry membrane forces and the internal layer carries only the out-of-plane shears. The utility of the assessment approach is discussed with reference to a case study of a 3D structure made of reinforced concrete walls.

Selection of exterior wall using advantageousness comparison; Ulkoseinaen valinta elinkaariedullisuuden perusteella

Energy Technology Data Exchange (ETDEWEB)

Saari, A.; Vesa, M.

2001-07-01

The objective of the study was to clarify the advantageousness of six chosen exterior wall solutions and at the same time to produce the procedure the measurement of the advantageousness. The examined wall types were: (1) brick wall, (2) brick-wool-concrete wall, (2b) brick-wool-concrete wall (not plastered), (3) brick-wool-wood wall, (4) precast concrete wall, and (5) plaster-wool-concrete wall. The analysis was made to a residential construction project which is built in a frame municipality of the metropolitan area. Here the life cycle costs, environmental burdens, and other factors (the aesthetic character, image, a comfort and easy maintenance) have an affect to the advantageousness of exterior wall. The averages of appreciation of the seven members of the supervising body of this study were used as the weights of the aforementioned value factors in the comparison. The result of the analysis was that the unplastered brick-wool-concrete wall had the equal life cycle costs as the precast concrete wall (an annual cost FIM 70 per apartment floor area). They were superior in relation to other examined wall types. In turn the brick wall had the highest life cycle costs (an annual cost nearly FIM 200 per apartment floor area) from the examined wall solutions on the advantageousness measuring straightforwardly likewise. It was chosen for an examination time period for 50 years. Likewise the brick wall was the distinctly weakest solution eco-economically, irrespective of, how costs and environmental factors are weighted. The brick wall was both the most expensive and unecological from the examined exterior wall types. It had a weak ecological qualities because considerably more building material than to other examined wall types. Also it's thermal insulation capacity was the weakest. But if in the decision-making also the aesthetic character, image, the effect on the comfort, and easy maintenance of the exterior wall indeed are included in addition to the eco

Evolution of the Stability Work from Classic Retaining Walls to Mechanically Stabilized Earth Walls

Directory of Open Access Journals (Sweden)

Anghel Stanciu

2008-01-01

Full Text Available For the consolidation of soil mass and the construction of the stability works for roads infrastructure it was studied the evolution of these kinds of works from classical retaining walls - common concrete retaining walls, to the utilization in our days of the modern and competitive methods - mechanically stabilized earth walls. Like type of execution the variety of the reinforced soil is given by the utilization of different types of reinforcing inclusions (steel strips, geosynthetics, geogrids or facing (precast concrete panels, dry cast modular blocks, metal sheets and plates, gabions, and wrapped sheets of geosynthetics.

A new model for anisotropic damage in concrete and its application to the prediction of failure of some containment vessel

International Nuclear Information System (INIS)

Badel, P.-B.; Godard, V.; Leblond, J.-B.

2005-01-01

The aim of this paper is to propose a new model for damage in concrete structures which incorporates such complex features as damage anisotropy and asymmetry between tension and compression, while being expressed in a format well suited for numerical applications and involving a limited number of material parameters which can be determined from standard experiments. A crude version of the model involving a single tonsorial internal variable representing damage in tension, and a single material parameter, is presented first. The predictions of this simple model are satisfactory in simple tension, but not so in simple compression. As a remedy, various refinements are then introduced in a second version of the model involving an additional tonsorial or scalar internal variable representing damage in compression, and five additional material parameters. An example of determination of the model parameters using experimental stress-strain curves in simple tension and compression, plus failure envelopes in biaxial tension/compression, is presented next. The model is finally applied to the numerical prediction of the failure of some containment vessel subjected to some large internal pressure, with a comparison with calculations based on a simpler isotropic variant of the model using a single scalar damage variable. The results illustrate the relevance of models incorporating both asymmetry between tension and compression and anisotropy of damage for simulations of industrial concrete structures. (authors)

Drilling-induced borehole-wall damage at spent fuel test-climax

International Nuclear Information System (INIS)

Weed, H.C.; Durham, W.B.

1982-12-01

Microcracks in a sample of quartz monzonite from the Spent Fuel Test-Climax were measured by means of a scanning electron microscope in order to estimate the background level of damage near the borehole-wall. It appears that the hammer-drilling operation used to create the borehole has caused some microfracturing in a region 10 to 30 mm wide around the borehole. Beyond 30 mm, the level of microfracturing cannot be distinguished from background

Modeling and conduct of turbine missile concrete impact experiments

International Nuclear Information System (INIS)

Woodfin, R.L.

1981-01-01

The overall objective of the subject experiments was to provide full scale data on the response of reinforced concrete containment walls to impact and penetration by postulated turbine-produced missiles. These data can be used to validate analytical or scale modeling methods and to assess the applicability of current design formulas to penetration by large, irregularly shaped missiles. These data and results will be used in providing more realistic estimates of turbine missile damage probability in nuclear power plants with a non-peninsula arrangement. This paper describes the derivation of the test matrix and the method of conducting the experiments. (orig./HP)

Flow conditions of fresh mortar and concrete in different pipes

International Nuclear Information System (INIS)

Jacobsen, Stefan; Haugan, Lars; Hammer, Tor Arne; Kalogiannidis, Evangelos

2009-01-01

The variation in fresh concrete flow rate over the pipe cross section was investigated on differently coloured and highly flowable concrete mixes flowing through pipes of different materials (rubber, steel, acryl). First, uncoloured (gray) concrete was poured through the pipe and the pipe blocked. Similar but coloured (black) concrete was then poured into the pipe filled with gray concrete, flowing after the gray concrete for a while before being blocked and hardened. The advance of the colouring along the pipe wall (showing boundary flow rate) was observed on the moulded concrete surface appearing after removing the pipe from the hardened concrete. The shapes of the interfaces between uncoloured and coloured concrete (showing variation of flow rate over the pipe cross section) were observed on sawn surfaces of concrete half cylinders cut along the length axes of the concrete-filled pipe. Flow profiles over the pipe cross section were clearly seen with maximum flow rates near the centre of the pipe and low flow rate at the pipe wall (typically rubber pipe with reference concrete without silica fume and/or stabilizers). More plug-shaped profiles, with long slip layers and less variation of flow rate over the cross section, were also seen (typically in smooth acrylic pipes). Flow rate, amount of concrete sticking to the wall after flow and SEM-images of pipe surface roughness were observed, illustrating the problem of testing full scale pumping.

Composite Behavior of a Novel Insulated Concrete Sandwich Wall Panel Reinforced with GFRP Shear Grids: Effects of Insulation Types.

Science.gov (United States)

Kim, JunHee; You, Young-Chan

2015-03-03

A full-scale experimental program was used in this study to investigate the structural behavior of novel insulated concrete sandwich wall panels (SWPs) reinforced with grid-type glass-fiber-reinforced polymer (GFRP) shear connectors. Two kinds of insulation-expanded polystyrene (EPS) and extruded polystyrene (XPS) with 100 mm thickness were incased between the two concrete wythes to meet the increasing demand for the insulation performance of building envelope. One to four GFRP shear grids were used to examine the degree of composite action of the two concrete wythes. Ten specimens of SWPs were tested under displacement control subjected to four-point concentrated loads. The test results showed that the SWPs reinforced with GFRP grids as shear connectors developed a high degree of composite action resulting in high flexural strength. The specimens with EPS foam exhibited an enhanced load-displacement behavior compared with the specimens with XPS because of the relatively stronger bond between insulation and concrete. In addition, the ultimate strength of the test results was compared to the analytical prediction with the mechanical properties of only GRFP grids. The specimens with EPS insulation presented higher strength-based composite action than the ones with XPS insulation.

Innovative technology summary report: Concrete grinder

International Nuclear Information System (INIS)

1998-09-01

The Flex concrete grinder is a lightweight, hand-held concrete and coating removal system used for decontaminating or stripping concrete surfaces. The US Department of Energy has successfully demonstrated it for decontaminating walls and floors for free release surveys prior to demolition work. The grinder is an electric-powered tool with a vacuum port for dust extraction and a diamond grinding wheel. The grinder is suitable for flat or slightly curved surfaces and results in a smooth surface, which makes release surveys more reliable. The grinder is lightweight and produces very little vibration, thus reducing worker fatigue. The grinder is more efficient than traditional baseline, tools at removing contamination from concrete surfaces (more than four times faster than hand-held pneumatic scabbling and scaling tools). Grinder consumables (i.e., replacement diamond grinding wheel) are more expensive than the replacement carbide parts for the scaler and scabbler. However, operating costs are outweighed by the lower purchase price of the grinder (50% of the price of the baseline scaler and 8% of the price of the baseline scabbler). Overall, the concrete grinder is an attractive alternative to traditional scabbling and scaling pneumatic tools. To this end, in July 1998, the outer rod room exposed walls of the Safe Storage Enclosure (SSE), an area measuring approximately 150 m 2 , may be decontaminated with the hand-held grinder. This concrete grinder technology was demonstrated for the first time at the DOE's Hanford Site. Decontamination of a sample room walls was performed at the C Reactor to free release the walls prior to demolition. The demonstration was conducted by onsite D and D workers, who were instructed by the vendor prior to and during the demonstration

Static and dynamic testing of a damaged post tensioned concrete beam

Directory of Open Access Journals (Sweden)

Limongelli M.P.

2015-01-01

Full Text Available In this paper are reported the results of an experimental campaign carried out on a post tensioned concrete beam with the aim of investigating the possibility to detect early warning signs of deterioration basing on static and/or dynamic tests. The beam was tested in several configurations aimed to reproduce several different phases of the ‘life’ of the beam: the original undamaged state, increasing loss of tension in the post tensioning cables, a strengthening intervention carried out by means of a second tension cable, formation of further cracks on the strengthened beam. Responses of the beam were measured by an extensive set of instruments consisting of accelerometers, inclinometers, displacement transducers, strain gauges and optical fibres. The paper discusses the tests program and the dynamic characterization of the beam in the different damage scenarios. The modal properties of the beam in the different phases were recovered basing on the responses recorded on the beam during sine-sweep and impact hammer tests. The variation of the first modal frequency was studied to investigate the sensitivity of this parameter to both the cracking of the concrete section and the tension in the cables and also to compare results given by different types of experimental tests.

Comparison of Thermal Stability of Dry High-strength Concrete and Wet High-strength Concrete

Science.gov (United States)

Musorina, Tatiana; Katcay, Aleksandr; Selezneva, Anna; Kamskov, Victor

2018-03-01

High-strength concrete is a modern material, which occupies it`s own niche on the construction material market. It is applicable in a large-scale high-rise construction, particularly an underground construction is a frequently used solution for a space saving. Usually underground structure is related to a wet usage environment. Though not all properties of the high-strength concrete are investigated to the full extent. Under adverse climatic conditions of the Russian Federation one of the most important properties for constructional materials is a thermal capacity. Therefore, the main purpose of the paper is to compare a thermal capacity of the high-strength concrete in humid conditions and a thermal capacity of the high-strength concrete in dry operational condition. During the study dependency between thermal capacity and design wall thickness and ambient humidity has to be proven with two experiments. As a result the theoretical relation between thermal capacity characteristic - thermal inertia and wall thickness and ambient humidity was confirmed by the experimental data. The thermal capacity of a building is in direct ratio to the construction thickness. It follows from the experiments and calculations that wet high-strength concrete has less thermal stability.

Experimental assessment and numerical modeling of the nonlinear behavior of the masonry shear walls under in-plane cyclic loading considering the brickwork-setting effect

Directory of Open Access Journals (Sweden)

Amir Hossein Karimi

2017-08-01

Full Text Available In this article, the main purpose is nonlinear analysis of the cyclic behavior of the masonry shear walls including brickwork setting using finite element method. Three different brickwork-settings including running bond style, herringbone style and Zarbi style (herreh style were investigated. To this end, the walls (in dimension of 195×1500×1720 mm were tested in the laboratory and then were simulated using macro modeling method by Abaqus software, and their hysteretic curves was drawn. The concrete damaged plasticity criteria in the Abaqus software is a model used in this research.In this method, the main failure mechanisms of fracture are cracking in tension and crushing in compression. The macro modeling method was used for numerical assessment of the masonry walls. After numerical modeling and drawing hysteretic curves and contrasting them with laboratory results, it was proven that the concrete damaged plasticity model, which is behavioral model for simulating concrete material, can be used for modeling masonry materials under seismic loading. However, this model cannot be used to simulate pinching effect in hysteretic curve drawn from seismic loading. The envelope curve resulted from the numerical analysis of all three brickwork layouts had a good agreement with the results of the laboratory tests, but in Hysteretic curve of Herringbone style and Zarbi style the pinching effect did not match experimental results

Prestressing of reinforcing bars in concrete slabs due to concrete expansion induced by Alkali-Silica Reaction

DEFF Research Database (Denmark)

Gustenhoff Hansen, Søren; Antonio Barbosa, Ricardo; Hoang, Linh Cao

2017-01-01

Alkali-silica reactions (ASR) in concrete bridges have been a major concern worldwide for many decades. In Denmark, several bridges are severely damaged due to ASR and over 600 bridges have the potential to develop ASR in the future. The majority of these bridges are slab-bridges. Despite the many...... cases, experimental research on structural safety and residual load carrying capacity of ASR-damaged bridges is limited. As ASR causes severe cracks in the concrete, which may affect the concrete compressive and tensile strength, concerns have been directed towards the residual shear capacity. Yet...

Axial compression behavior of concrete masonry wallettes strengthened with cement mortar overlays

Directory of Open Access Journals (Sweden)

F. L. De Oliveira

Full Text Available This paper presents the results of a series of axial compression tests on concrete block wallettes coated with cement mortar overlays. Different types of mortars and combinations with steel welded meshes and fibers were tested. The experimental results were discussed based on different theoretical approaches: analytical and Finite Element Method models. The main conclusions are: a the application of mortar overlays increases the wall strength, but not in a uniform manner; b the strengthening efficiency of wallettes loaded in axial compression is not proportional to the overlay mortar strength because it can be affected by the failure mechanisms of the wall; c steel mesh reinforced overlays in combination with high strength mortar show better efficiency, because the steel mesh mitigates the damage effects in the block wall and in the overlays themselves; d simplified theoretical methods of analysis as described in this paper can give satisfactory predictions of masonry wall behavior up to a certain level.

DEPENDENCIES TO DETERMINE THE MEASURE OF DAMAGE AND CALCULATION OF RESIDUAL LIFE OF REINFORCED CONCRETE SUPERSTRUCTURE, EXPOSED TO SALT CORROSION

OpenAIRE

SAATOVA NODIRA ZIYAYEVNA

2016-01-01

In this paper we consider the current method of determining the measure of damage of concrete and reinforcement. The proposed dependence measures of damage, convenient for use in predicting the life of structures superstructures.The practical method of calculation determination of residual resource of the exploited superstructures developed. The main source of data for calculating the residual life are the parameters defined by the technical diagnosis.

Application of the Hybrid Simulation Method for the Full-Scale Precast Reinforced Concrete Shear Wall Structure

Directory of Open Access Journals (Sweden)

Zaixian Chen

2018-02-01

Full Text Available The hybrid simulation (HS testing method combines physical test and numerical simulation, and provides a viable alternative to evaluate the structural seismic performance. Most studies focused on the accuracy, stability and reliability of the HS method in the small-scale tests. It is a challenge to evaluate the seismic performance of a twelve-story pre-cast reinforced concrete shear-wall structure using this HS method which takes the full-scale bottom three-story structural model as the physical substructure and the elastic non-linear model as the numerical substructure. This paper employs an equivalent force control (EFC method with implicit integration algorithm to deal with the numerical integration of the equation of motion (EOM and the control of the loading device. Because of the arrangement of the test model, an elastic non-linear numerical model is used to simulate the numerical substructure. And non-subdivision strategy for the displacement inflection point of numerical substructure is used to easily realize the simulation of the numerical substructure and thus reduce the measured error. The parameters of the EFC method are calculated basing on analytical and numerical studies and used to the actual full-scale HS test. Finally, the accuracy and feasibility of the EFC-based HS method is verified experimentally through the substructure HS tests of the pre-cast reinforced concrete shear-wall structure model. And the testing results of the descending stage can be conveniently obtained from the EFC-based HS method.

Leakage tests of wall segments of reactor containments

International Nuclear Information System (INIS)

Rizkalla, S.H.; Simmonds, S.H.; MacGregor, J.G.

1979-10-01

Two prestressed concrete wall segments simulating portions of containment walls were loaded by axial tensile forces to cause cracking of the concrete. At each load increment air pressure was applied in steps up to 21 psi to one side of the segment and the rate of leakage of air through the cracked concrete section was measured. A theoretical equation for the flow of air through concrete cracks is developed and the results from one leakage test are used to determine the dimensionless constant required for this equation. (author)

Monitoring water loss form fresh concrete

DEFF Research Database (Denmark)

Jensen, Ole Mejlhede

2006-01-01

Desiccation of concrete before or during setting may lead to detrimental plastic shrinkage cracking in the concrete surface zone. Cracking due to plastic shrinkage is a major technological problem for any concrete, however, modern high-performance concretes are especially susceptible to this...... determination of the evaporation loss from hardening concrete and thus better possibility for preventing curing problems, including detrimental crack damage due to plastic shrinkage....

The Influence of Infill Wall Topology and Seismic Characteristics on the Response and Damage Distribution in Frame Structures

Directory of Open Access Journals (Sweden)

Nikos Nanos

2013-01-01

Full Text Available This paper identifies the effects of infill wall existence and arrangement in the seismic response of frame structures utilising the global structural damage index after Park/Ang (GDIPA and the maximum interstorey drift ratio (MISDR to express structural seismic response. Five different infill wall topologies of a 10-storey frame structure have been selected and analysed presenting an improved damage distribution model for infill wall bearing frames, hence promoting the use of nonstructural elements as a means of improving frame structural seismic behaviour and highlighting important aspects of structural response, demonstrating the suitability of such element implementation beyond their intended architectural scope.

Analysis and seismic tests of composite shear walls with CFST columns and steel plate deep beams

Science.gov (United States)

Dong, Hongying; Cao, Wanlin; Wu, Haipeng; Zhang, Jianwei; Xu, Fangfang

2013-12-01

A composite shear wall concept based on concrete filled steel tube (CFST) columns and steel plate (SP) deep beams is proposed and examined in this study. The new wall is composed of three different energy dissipation elements: CFST columns; SP deep beams; and reinforced concrete (RC) strips. The RC strips are intended to allow the core structural elements — the CFST columns and SP deep beams — to work as a single structure to consume energy. Six specimens of different configurations were tested under cyclic loading. The resulting data are analyzed herein. In addition, numerical simulations of the stress and damage processes for each specimen were carried out, and simulations were completed for a range of location and span-height ratio variations for the SP beams. The simulations show good agreement with the test results. The core structure exhibits a ductile yielding mechanism characteristic of strong column-weak beam structures, hysteretic curves are plump and the composite shear wall exhibits several seismic defense lines. The deformation of the shear wall specimens with encased CFST column and SP deep beam design appears to be closer to that of entire shear walls. Establishing optimal design parameters for the configuration of SP deep beams is pivotal to the best seismic behavior of the wall. The new composite shear wall is therefore suitable for use in the seismic design of building structures.

Finite element analysis of degraded concrete structures - Workshop proceedings

International Nuclear Information System (INIS)

1999-09-01

This workshop is related to the finite element analysis of degraded concrete structures. It is composed of three sessions. The first session (which title is: the use of finite element analysis in safety assessments) comprises six papers which titles are: Historical Development of Concrete Finite Element Modeling for Safety Evaluation of Accident-Challenged and Aging Concrete Structures; Experience with Finite Element Methods for Safety Assessments in Switzerland; Stress State Analysis of the Ignalina NPP Confinement System; Prestressed Containment: Behaviour when Concrete Cracking is Modelled; Application of FEA for Design and Support of NPP Containment in Russia; Verification Problems of Nuclear Installations Safety Software of Strength Analysis (NISS SA). The second session (title: concrete containment structures under accident loads) comprises seven papers which titles are: Two Application Examples of Concrete Containment Structures under Accident Load Conditions Using Finite Element Analysis; What Kind of Prediction for Leak rates for Nuclear Power Plant Containments in Accidental Conditions; Influence of Different Hypotheses Used in Numerical Models for Concrete At Elevated Temperatures on the Predicted Behaviour of NPP Core Catchers Under Severe Accident Conditions; Observations on the Constitutive Modeling of Concrete Under Multi-Axial States at Elevated Temperatures; Analyses of a Reinforced Concrete Containment with Liner Corrosion Damage; Program of Containment Concrete Control During Operation for the Temelin Nuclear Power Plant; Static Limit Load of a Deteriorated Hyperbolic Cooling Tower. The third session (concrete structures under extreme environmental load) comprised five papers which titles are: Shear Transfer Mechanism of RC Plates After Cracking; Seismic Back Calculation of an Auxiliary Building of the Nuclear Power Plant Muehleberg, Switzerland; Seismic Behaviour of Slightly Reinforced Shear Wall Structures; FE Analysis of Degraded Concrete

Shaking Table Tests of Reinforced Concrete Frames

DEFF Research Database (Denmark)

Skjærbæk, P. S.; Kirkegaard, Poul Henning; Nielsen, Søren R.K.

-varying systems and to verify various methods for damage assessment of reinforced concrete structures from soft motion measurements. In this study the maximum softening concept will be evaluated. In the paper the assessment obtained by this method is compared to visual damage assessment. The structures considered...... vector ARMA model is suitable for modal identification of degrading reinforced concrete structures and the maximum softening damage index calculated from the obtained identification provides a valuable tool for assessment of the damage state of the structure....

Numerical analysis on seismic behavior of reinforced concrete beam to concrete filled steel tubular column connections with ring-beam

Energy Technology Data Exchange (ETDEWEB)

Zhao, Yi., E-mail: zhaoyi091218@163.com [School of Civil and Architectural Engineering, Zhongyuan University of Technology,Zhengzhou 450000 (China); Xu, Li. Hua. [School of Civil Engineering, Wuhan University, No.8, Donghu Road, WuHan 430072 (China)

2016-06-08

This paper presents numerical study of the seismic behavior of reinforced concrete beam to concrete filled steel tube column connections with ring-beam. The material stress-strain relations, element type and boundary condition are selected, which are consistent with actual situation. Then the seismic behavior of this type of joint are researched by ABAQUS, and finite element analyses are conducted under cyclic loading. Its parameters are discussed including thickness of steel tubular column wall, sectional dimension of the ring-beam and strength of the core concrete. The results show that the ultimate capacity of the connections is improved with sectional dimension of the ring-beam increased. In the meanwhile, the influence on skeleton curve of the joints is slight of which included thickness of steel tubular column wall and strength of the core concrete.

Probabilistic Analysis of Structural Member from Recycled Aggregate Concrete

Science.gov (United States)

Broukalová, I.; Šeps, K.

2017-09-01

The paper aims at the topic of sustainable building concerning recycling of waste rubble concrete from demolition. Considering demands of maximising recycled aggregate use and minimising of cement consumption, composite from recycled concrete aggregate was proposed. The objective of the presented investigations was to verify feasibility of the recycled aggregate cement based fibre reinforced composite in a structural member. Reliability of wall from recycled aggregate fibre reinforced composite was assessed in a probabilistic analysis of a load-bearing capacity of the wall. The applicability of recycled aggregate fibre reinforced concrete in structural applications was demonstrated. The outcomes refer to issue of high scatter of material parameters of recycled aggregate concretes.

Ageing management of nuclear power plant concrete structures - Overview and suggested research topics

International Nuclear Information System (INIS)

Naus, J.

2009-01-01

Nuclear power plant concrete structures are described and their operating experience noted. Primary considerations related to management of their ageing are noted and an indication of their status provided: degradation mechanisms, damage models, and material performance; assessment and remediation (i.e., component selection, in-service inspection, non-destructive examinations, and remedial actions); and estimation of performance at present or some future point in time (i.e., application of structural reliability theory to the design and optimisation of in-service inspection/maintenance strategies, and determination of the effects of degradation on plant risk). Several activities are identified that provide background information and data on areas of concern with respect to non-destructive examination of nuclear power plant concrete structures: inspection of thick-walled, heavily-reinforced sections; basemat; and inaccessible areas of the containment metallic pressure boundary. Topics are noted where additional research would be of benefit to ageing management of nuclear power plant concrete structures. (author)

Damping characteristics of reinforced concrete structures

International Nuclear Information System (INIS)

Hisano, M.; Nagashima, I.; Kawamura, S.

1987-01-01

Reinforced concrete structures in a nuclear power plant are not permitted to go far into the inelasticity generally, even when subjected to strong ground motion. Therefore it is important to evaluate the damping appropriately in linear and after cracking stage before yielding in the dynamic response analysis. Next three dampings are considered of reinforced concrete structures. 1) Internal damping in linear range material damping of concrete without cracks;2) Hysteretic damping in inelastic range material hysteretic damping of concrete due to cracking and yielding;3) Damping due to the energy dissipation into the ground. Among these damping material damping affects dynamic response of a nuclear power plant on hard rock site where damping due to energy dissipation into the ground is scarcely expected. However material damping in linear and slightly nonlinear range have only been assumed without enough experimental data. In this paper such damping is investigated experimentally by the shaking table tests of reinforced concrete box-walls which modeled roughly the outer wall structure of a P.W.R. type nuclear power plant

Slipforming of reinforced concrete shield building

International Nuclear Information System (INIS)

Hsieh, M.C.; King, J.R.

1982-01-01

The unique design and construction features of slipforming the heavily reinforced concrete cylindrical shield walls at the Satsop nuclear plant in Washington, D.C. site are presented. The shield walls were designed in compliance with seismic requirements which resulted in the need for reinforcing steel averaging 326 kg/m/sup 3/. A 7.6 m high, three-deck moving platform was designed to permit easy installation of the reinforcing steel, embedments, and blockouts, and to facilitate concrete placement and finishing. Two circular box trusses, one on each side of the shield wall, were used in combination with a spider truss to meet both the tolerance and strength requirements for the slipform assembly

Evaluation of tritiated water retention capacity of fusion reactor concrete building

International Nuclear Information System (INIS)

Numata, S.; Fujii, Y.; Okamoto, M.

1992-01-01

In this paper the diffusion of tritiated water vapor into concrete walls is studied to evaluate tritiated water retention capacity of a fusion reactor concrete building. Using a model of the tritiated water diffusion determined form experimental results, depth profiles of tritiated water in concrete are calculated in the case of being exposed to air containing tritiated water vapor during the normal operational condition of a fusion reactor. A 0.5-m-thick concrete is sufficient for reactor hall walls from a viewpoint of the tritium containment

A Method of Assembling Wall or Floor Elements

DEFF Research Database (Denmark)

2002-01-01

The invention relates to a method of constructing, at the site of use, a building wall (1) or a building floor (1) using a plurality of prefabricated concrete or lightweight concrete plate-shaped wall of floor elements (10), in particular cast elements, which have a front side and a rear side...

Seismic Performance of Precast Polystyrene RC Walls

Directory of Open Access Journals (Sweden)

Wibowo Ari

2017-01-01

Full Text Available Precast concrete structure such as precast wall is a concept that is growing rapidly these days. However, the earthquake resistance is believed to be one of its drawbacks. Additionally, the large weight of solid elements also increase the building weight significantly which consequently increase the earthquake base shear force as well. Therefore, investigation on the seismic performance of precast concrete wall has been carried out. Three RC wall specimens using wire mesh reinforcement and EPS (Extended Polystyrene System panel have been tested. This wall was designed as a structural wall that was capable in sustaining lateral loads (in-plane yet were lightweight to reduce the total weight of the building. Parameter observed was the ratio of height to width (aspect ratio of wall of 1.0, 1.5 and 2.0 respectively with the aim to study the behaviour of brittle to ductile transition of the wall. Incremental static load tests were conducted until reaching peak load and then followed by displacement control until failure. Several data were measured at every stage of loading comprising lateral load-displacement behaviour, ultimate strength and collapse mechanism. The outcomes showed that precast concrete walls with a steel wire and EPS panel filler provided considerably good resistance against lateral load.

Using structural damage statistics to derive macroseismic intensity within the Kathmandu valley for the 2015 M7.8 Gorkha, Nepal earthquake

Science.gov (United States)

McGowan, S. M.; Jaiswal, K. S.; Wald, D. J.

2017-09-01

We make and analyze structural damage observations from within the Kathmandu valley following the 2015 M7.8 Gorkha, Nepal earthquake to derive macroseismic intensities at several locations including some located near ground motion recording sites. The macroseismic intensity estimates supplement the limited strong ground motion data in order to characterize the damage statistics. This augmentation allows for direct comparisons between ground motion amplitudes and structural damage characteristics and ultimately produces a more constrained ground shaking hazard map for the Gorkha earthquake. For systematic assessments, we focused on damage to three specific building categories: (a) low/mid-rise reinforced concrete frames with infill brick walls, (b) unreinforced brick masonry bearing walls with reinforced concrete slabs, and (c) unreinforced brick masonry bearing walls with partial timber framing. Evaluating dozens of photos of each construction type, assigning each building in the study sample to a European Macroseismic Scale (EMS)-98 Vulnerability Class based upon its structural characteristics, and then individually assigning an EMS-98 Damage Grade to each building allows a statistically derived estimate of macroseismic intensity for each of nine study areas in and around the Kathmandu valley. This analysis concludes that EMS-98 macroseismic intensities for the study areas from the Gorkha mainshock typically were in the VII-IX range. The intensity assignment process described is more rigorous than the informal approach of assigning intensities based upon anecdotal media or first-person accounts of felt-reports, shaking, and their interpretation of damage. Detailed EMS-98 macroseismic assessments in urban areas are critical for quantifying relations between shaking and damage as well as for calibrating loss estimates. We show that the macroseismic assignments made herein result in fatality estimates consistent with the overall and district-wide reported values.

Non-linear thermal analysis of light concrete hollow brick walls by the finite element method and experimental validation

International Nuclear Information System (INIS)

Diaz del Coz, J.J.; Nieto, P.J. Garcia; Rodriguez, A. Martin; Martinez-Luengas, A. Lozano; Biempica, C. Betegon

2006-01-01

The finite element method (FEM) is applied to the non-linear complex heat transfer analysis of light concrete hollow brick walls. The non-linearity is due to the radiation boundary condition inside the inner holes of the bricks. The conduction and convection phenomena are taking into account in this study for three different values of the conductivity mortar and two values for the brick. Finally, the numerical and experimental results are compared and a good agreement is shown

Non-linear thermal analysis of light concrete hollow brick walls by the finite element method and experimental validation

Energy Technology Data Exchange (ETDEWEB)

Del Coz Diaz, J.J.; Rodriguez, A. Martin; Martinez-Luengas, A. Lozano; Biempica, C. Betegon [Department of Construction, University of Oviedo, Edificio Departamental Viesques No 7, Dpcho. 7.1.02 Campus de Viesques, 33204 Gijon, Asturias (Spain); Nieto, P.J. Garcia [Departamento de Matematicas, Facultad de Ciencias, C/Calvo Sotelo s/n, 33007 Oviedo, Asturias (Spain)

2006-06-15

The finite element method (FEM) is applied to the non-linear complex heat transfer analysis of light concrete hollow brick walls. The non-linearity is due to the radiation boundary condition inside the inner holes of the bricks. The conduction and convection phenomena are taking into account in this study for three different values of the conductivity mortar and two values for the brick. Finally, the numerical and experimental results are compared and a good agreement is shown. [Author].

Non-linear thermal analysis of light concrete hollow brick walls by the finite element method and experimental validation

Energy Technology Data Exchange (ETDEWEB)

Diaz del Coz, J.J. [Department of Construction, University of Oviedo, Edificio Departamental Viesques No 7, Dpcho. 7.1.02 Campus de Viesques, 33204 Gijon, Asturias (Spain)]. E-mail: juanjo@constru.uniovi.es; Nieto, P.J. Garcia [Departamento de Matematicas, Facultad de Ciencias, C/Calvo Sotelo s/n, 33007 Oviedo, Asturias (Spain); Rodriguez, A. Martin [Department of Construction, University of Oviedo, Edificio Departamental Viesques No 7, Dpcho. 7.1.02 Campus de Viesques, 33204 Gijon, Asturias (Spain); Martinez-Luengas, A. Lozano [Department of Construction, University of Oviedo, Edificio Departamental Viesques No 7, Dpcho. 7.1.02 Campus de Viesques, 33204 Gijon, Asturias (Spain); Biempica, C. Betegon [Department of Construction, University of Oviedo, Edificio Departamental Viesques No 7, Dpcho. 7.1.02 Campus de Viesques, 33204 Gijon, Asturias (Spain)

2006-06-15

The finite element method (FEM) is applied to the non-linear complex heat transfer analysis of light concrete hollow brick walls. The non-linearity is due to the radiation boundary condition inside the inner holes of the bricks. The conduction and convection phenomena are taking into account in this study for three different values of the conductivity mortar and two values for the brick. Finally, the numerical and experimental results are compared and a good agreement is shown.

Structural performance of new thin-walled concrete sandwich panel system reinforced with bfrp shear connectors

DEFF Research Database (Denmark)

Hodicky, Kamil; Hulin, Thomas; Schmidt, Jacob Wittrup

2013-01-01

This paper presents a new thin-walled concrete sandwich panel system reinforced with basalt fiber-reinforced plastic (BFRP) with optimum structural performances and a high thermal resistance developed by Connovate and Technical University of Denmark. The shear connecting system made of a BFRP grid...... is described and provides information on the structural design with its advantages. Experimental and numerical investigations of the BFRP connecting systems were performed. The experimental program included testing of small scale specimens by applying shear (push-off) loading and semi-full scale specimens...... on finite element modelling showed that the developed panel system meets the objectives of the research and is expected to have promising future....

Ultrasonic imaging in concrete

International Nuclear Information System (INIS)

Ribay, G.; Paris, O.; Rambach, J.M.

2009-01-01

The third and final protection barrier confining nuclear reactors is usually a concrete containment structure. Monitoring the structural integrity of these barriers is critical in ensuring the safety of nuclear power plants. The Institute for Radiological Protection and Nuclear Safety (IRSN) in France in collaboration with the French Atomic commission (CEA/LIST) has developed an ultrasonic phased-array technique capable of inspecting thick concrete walls. The non-destructive method is dedicated to detect cracks and bulk defects. Given the thickness of the structure (1.2 m) undergoing inspection and the heterogeneity of the concrete, the optimal frequency lies in the 50-300 kHz range. At these frequencies, the ultrasonic beam profiles are widespread (non-directive) with poor signal-to-noise ratio. Previous studies have shown the potential of using phased-array techniques (i.e., beam focusing and beam steering) in order to improve detection resolution and sizing accuracy. In this paper we present experimental studies performed with array up to 16 transducers working at 200 kHz. Experiments are carried out on representative concrete blocks containing artificial defects. One is a reinforced mock-up representative of the first reinforcing mesh of wall containment. Experimental results show that in spite of the reinforcement, artificial defects deep as half a meter can be detected. Reconstructed images resulting from phased array acquisitions on an artificial crack embedded in a concrete block are also presented and discussed. The presented method allows detecting oriented defects in concrete with improved signal to noise ratio and sensibility. A simulation model of the interaction of ultrasound with a heterogeneous medium like concrete is briefly commented. (authors)

Potential of waste tires as aggregates in concrete | Mutuku | Journal ...

African Journals Online (AJOL)

Potential use of this kind of concrete includes nonstructural purposes such as lightweight concrete walls and blocks, building facades and crash barriers. Keywords: concrete aggregates, rubber chips, rubberized concrete, used tires, waste recycling. Journal of Civil Engineering Research and Practice Vol. 3(1) 2006: 75-84 ...

Self-sensing concrete with nanomaterials

OpenAIRE

Chen, Z.; Ding, Y.; Torgal, Fernando Pacheco; Zhang, Y.

2013-01-01

Conductive concrete containing nano carbon black (NCB) and carbon fibre (CF) to enable the self-diagnosis of strain and damage was studied. The effect of NCB and CF on workability, mechanical properties and fractional change in resistance (FCR) in fresh and hardened concrete was analysed. The relationship between the FCR, the strain of initial geometrical neutral axis (IGNA) and the degree of beam damage was established. The results showed that the relationship between the FCR and the IGNA st...

Nonlinear analysis of reinforced concrete structures using software package abaqus

Directory of Open Access Journals (Sweden)

Marković Nemanja

2014-01-01

Full Text Available Reinforced concrete (AB is characterized by huge inhomogeneity resulting from the material characteristics of the concrete, then, quasi-brittle behavior during failure. These and other phenomena require the introduction of material nonlinearity in the modeling of reinforced concrete structures. This paper presents the modeling reinforced concrete in the software package ABAQUS. A brief theoretical overview is presented of methods such as: Concrete Damage Plasticity (CDP, Smeared Concrete Cracking (CSC, Cap Plasticity (CP and Drucker-Prager model (DPM. We performed a nonlinear analysis of two-storey reinforced concrete frame by applying CDP method for modeling material nonlinearity of concrete. We have analyzed damage zones, crack propagation and loading-deflection ratio.

Performance of Lightweight Natural-Fiber Reinforced Concrete

Directory of Open Access Journals (Sweden)

Hardjasaputra Harianto

2017-01-01

Full Text Available Concrete, the most common construction material, has negligible tension capacity. However, a reinforcement material such as natural fibers, can be used to improve the tensile properties of concrete. This paper presents experiments conducted on Super Lightweight Concrete mixed with coconut fibers (SLNFRC. Coconut fibers are regarded as one of the toughest natural fibers to strengthen concrete. Coconut fiber reinforced composites have been considered as a sustainable construction material because the fibers are derived from waste. These wastes, which are available in large quantities in Asia, have to be extracted from the husk of coconut fruits and must pass a mechanical process before being added to a concrete mixture. The Super Lightweight Concrete was made by mixing concrete paste with foam agent that can reduce the overall weight of concrete up to 60% with compressive strength up to 6 MPa. The Super Lightweight Concrete is intended to be used for non-structural walls, as alternative conventional construction materials such as brick walls. The influence of coconut fibers content in increasing the flexural tensile strength of Super Lightweight Concrete was studied in this research. The fiber content studied include 0%, 0.1%, 0.175%, and 0.25% by weight of cement content. Sixteen specimens of SLNFRC mini beams of 60 mm x 60 mm x 300 mm were tested to failure to investigate their flexural strengths. The optimum percent fibers yielding higher tensile strength was found to be 0.175%

Experimental study of sodium fires on concrete based on the sodium-concrete reaction and its consequences: study of the behavior of various concretes under metallic sheaths

International Nuclear Information System (INIS)

Berlin; Colome, J.; Malet, J.C.

The problem created by the violent reaction between hot sodium and concrete has only recently been recognized. Its importance was evidenced during experiments in which the sodium-barium oxide concrete reactions led to violent explosions. SESR approached this question during its experimental programs Cassandre and Lucifer. The Cassandre 01 experiment demonstrated the sodium-ordinary concrete reaction, where sodium was burned directly in a concrete vat. The consequences of this fire, pulverization of sodium particles, explosions and deterioration of the concrete led to consideration of protecting the concrete. Among possible shieldings sheath metal appeared to be the safest solution. The Cassandre 08, Lucifer 01 and Lucifer 04 experiments were used to study the behavior of various qualities of concrete protected from fire by a metal wall. The results show that a metal cladding efficiently protects concrete from sodium leaks

Impact Analyses and Tests of Concrete Overpacks of Spent Nuclear Fuel Storage Casks

Energy Technology Data Exchange (ETDEWEB)

Lee, Sanghoon; Cho, Sangsoon; Jeon, Jeeon; Kim, Kiyoung; Seo, Kiseog [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

2014-02-15

A concrete cask is an option for spent nuclear fuel interim storage. A concrete cask usually consists of a metallic canister which confines the spent nuclear fuel assemblies and a concrete overpack. When the overpack undergoes a missile impact, which might be caused by a tornado or an aircraft crash, it should sustain an acceptable level of structural integrity so that its radiation shielding capability and the retrievability of the canister are maintained. A missile impact against a concrete overpack produces two damage modes, local damage and global damage. In conventional approaches, those two damage modes are decoupled and evaluated separately. The local damage of concrete is usually evaluated by empirical formulas, while the global damage is evaluated by finite element analysis. However, this decoupled approach may lead to a very conservative estimation of both damages. In this research, finite element analysis with material failure models and element erosion is applied to the evaluation of local and global damage of concrete overpacks under high speed missile impacts. Two types of concrete overpacks with different configurations are considered. The numerical simulation results are compared with test results, and it is shown that the finite element analysis predicts both local and global damage qualitatively well, but the quantitative accuracy of the results are highly dependent on the fine-tuning of material and failure parameters.

Impact Analyses and Tests of Concrete Overpacks of Spent Nuclear Fuel Storage Casks

International Nuclear Information System (INIS)

Lee, Sanghoon; Cho, Sangsoon; Jeon, Jeeon; Kim, Kiyoung; Seo, Kiseog

2014-01-01

A concrete cask is an option for spent nuclear fuel interim storage. A concrete cask usually consists of a metallic canister which confines the spent nuclear fuel assemblies and a concrete overpack. When the overpack undergoes a missile impact, which might be caused by a tornado or an aircraft crash, it should sustain an acceptable level of structural integrity so that its radiation shielding capability and the retrievability of the canister are maintained. A missile impact against a concrete overpack produces two damage modes, local damage and global damage. In conventional approaches, those two damage modes are decoupled and evaluated separately. The local damage of concrete is usually evaluated by empirical formulas, while the global damage is evaluated by finite element analysis. However, this decoupled approach may lead to a very conservative estimation of both damages. In this research, finite element analysis with material failure models and element erosion is applied to the evaluation of local and global damage of concrete overpacks under high speed missile impacts. Two types of concrete overpacks with different configurations are considered. The numerical simulation results are compared with test results, and it is shown that the finite element analysis predicts both local and global damage qualitatively well, but the quantitative accuracy of the results are highly dependent on the fine-tuning of material and failure parameters

Performance of Engineered Cementitious Composites for Concrete Repairs

NARCIS (Netherlands)

Zhou, J.

2011-01-01

Background and goals of this thesis The concrete repair, rehabilitation and retrofitting industry grows rapidly, driven by deterioration of, damage to and defects in concrete structures. However, it is well known that to achieve durable concrete repairs is very difficult. The failure of concrete

A new concept of precast concrete retaining wall: from laboratory model to the in-situ tests

Science.gov (United States)

Bui, T. T.; Tran, H. V.; Limam, A.; Bost, M.; Bui, Q. B.; Robit, P.

2018-04-01

A new concept for the soil nail walls is here proposed and validated through experimental and numerical approaches. This process, based on the use of precast elements that are easier to install, is cheaper and more aesthetic than the classical methods, but the main advantage is reducing the cement consumption which conducts to divided carbon footprint by three. In order to characterize the structural capacity of this new process, this article present an investigation on two in-situ representative walls, one in shotcrete which is the old way of construction, and the other, consisting the precast reinforced concrete slabs, which is the new process. We thus have a demonstrator on a real scale, and perfectly representative, since the constructive modes, as well as the mechanical, thermal, and hydric loadings are the real ones associated with the environment in situ. Substantial instrumentation has been realized over a long period (nearly 2 years), enabling to follow the evolution of the displacements of each wall and the efforts in the anchor nails. To determine the bearing capacity of the constituent element of the precast nail wall, an experimental study coupled with a numerical simulation has been conducted in the laboratory on a single precast slab. This study allows the evaluation of the load associated to crack initiation and the bearing capacity associated to the ultimate state, at the scale of the constituent elements. Finally, in order to evaluate the behaviour of the two concepts of nail walls in the case of extreme solicitation, a dynamic loading induced by an explosion has been conducted on the site.

Integrated modelling of corrosion-induced deterioration in rein-forced concrete structures

DEFF Research Database (Denmark)

Michel, Alexander; Geiker, M.R.; Stang, Henrik

2013-01-01

at the reinforcement surface, a FEM based me-chanical model was used to simulate corrosion-induced concrete damage. Both FEM models were fully coupled, i.e. information, such as corrosion current density, dam-age state of concrete cover, etc., were constantly exchanged between the models. To demonstrate the potential......An integrated finite element based modelling approach is presented, which allows for fully coupled simulation of reinforcement corrosion and corrosion-induced concrete damage. While a finite element method (FEM) based corrosion model was used to describe electrochemical processes...... use of the modelling approach, a numerical example is presented which illustrates full coupling of formation of corrosion cells, propagation of corrosion, and subsequent development of corrosion-induced concrete damage....

Concrete pavement mixture design and analysis (MDA) : assessment of air void system requirements for durable concrete.

Science.gov (United States)

2012-06-01

Concrete will suffer frost damage when saturated and subjected to freezing temperatures. Frost-durable concrete can be produced if a : specialized surfactant, also known as an air-entraining admixture (AEA), is added during mixing to stabilize micros...

Nuclear radiation and the properties of concrete

International Nuclear Information System (INIS)

Kaplan, M.F.

1983-08-01

Concrete is used for structures in which the concrete is exposed to nuclear radiation. Exposure to nuclear radiation may affect the properties of concrete. The report mentions the types of nuclear radiation while radiation damage in concrete is discussed. Attention is also given to the effects of neutron and gamma radiation on compressive and tensile strength of concrete. Finally radiation shielding, the attenuation of nuclear radiation and the value of concrete as a shielding material is discussed

The Evaluation of Damage Effects on MgO Added Concrete with Slag Cement Exposed to Calcium Chloride Deicing Salt

Science.gov (United States)

Jang, Jae-Kyeong; Kim, Hong-Gi; Kim, Jun-Hyeong

2018-01-01

Concrete systems exposed to deicers are damaged in physical and chemical ways. In mitigating the damage from CaCl2 deicers, the usage of ground slag cement and MgO are investigated. Ordinary Portland cement (OPC) and slag cement are used in different proportions as the binding material, and MgO in doses of 0%, 5%, 7%, and 10% are added to the systems. After 28 days of water-curing, the specimens are immersed in 30% CaCl2 solution by mass for 180 days. Compressive strength test, carbonation test, chloride penetration test, chloride content test, XRD analysis, and SEM-EDAX analysis are conducted to evaluate the damage effects of the deicing solution. Up to 28 days, plain specimens with increasing MgO show a decrease in compressive strength, an increase in carbonation resistance, and a decrease in chloride penetration resistance, whereas the S30- and S50- specimens show a slight increase in compressive strength, an increase in carbonation resistance, and a slight increase in chloride penetration resistance. After 180 days of immersion in deicing solution, specimens with MgO retain their compressive strength longer and show improved durability. Furthermore, the addition of MgO to concrete systems with slag cement induces the formation of magnesium silicate hydrate (M-S-H) phases. PMID:29758008

The Evaluation of Damage Effects on MgO Added Concrete with Slag Cement Exposed to Calcium Chloride Deicing Salt.

Science.gov (United States)

Jang, Jae-Kyeong; Kim, Hong-Gi; Kim, Jun-Hyeong; Ryou, Jae-Suk

2018-05-14

Concrete systems exposed to deicers are damaged in physical and chemical ways. In mitigating the damage from CaCl₂ deicers, the usage of ground slag cement and MgO are investigated. Ordinary Portland cement (OPC) and slag cement are used in different proportions as the binding material, and MgO in doses of 0%, 5%, 7%, and 10% are added to the systems. After 28 days of water-curing, the specimens are immersed in 30% CaCl₂ solution by mass for 180 days. Compressive strength test, carbonation test, chloride penetration test, chloride content test, XRD analysis, and SEM-EDAX analysis are conducted to evaluate the damage effects of the deicing solution. Up to 28 days, plain specimens with increasing MgO show a decrease in compressive strength, an increase in carbonation resistance, and a decrease in chloride penetration resistance, whereas the S30- and S50- specimens show a slight increase in compressive strength, an increase in carbonation resistance, and a slight increase in chloride penetration resistance. After 180 days of immersion in deicing solution, specimens with MgO retain their compressive strength longer and show improved durability. Furthermore, the addition of MgO to concrete systems with slag cement induces the formation of magnesium silicate hydrate (M-S-H) phases.

Composite steel panels for tornado missile barrier walls. Topical report

International Nuclear Information System (INIS)

1975-10-01

A composite steel panel wall system is defined as a wall system with concrete fill sandwiched between two steel layers such that no concrete surface is exposed on the interior or the exterior wall surface. Three full scale missile tests were conducted on two specific composite wall systems. The results of the full scale tests were in good agreement with the finalized theory. The theory is presented, and the acceptance of the theory for design calculations is discussed

Severe ASR damaged concrete bridges

DEFF Research Database (Denmark)

Antonio Barbosa, Ricardo; Gustenhoff Hansen, Søren

2015-01-01

Technical University of Denmark (DTU) and University of Southern Denmark (SDU) have conducted several full-scale experiments with severe ASR deteriorated bridges. This paper presents few and preliminary results from both the shear tests and the measuring of the material properties. The shear test...... show that the shear capacity is almost unaffected of ASR despite significant reduction in compressive concrete strength. Furthermore, measurements show a significant tensile reinforcement strain developed due to ASR expansion....

Characterization of Impact Damage in Ultra-High Performance Concrete Using Spatially Correlated Nanoindentation/SEM/EDX

Science.gov (United States)

Moser, R. D.; Allison, P. G.; Chandler, M. Q.

2013-12-01

Little work has been done to study the fundamental material behaviors and failure mechanisms of cement-based materials including ordinary Portland cement concrete and ultra-high performance concretes (UHPCs) under high strain impact and penetration loads at lower length scales. These high strain rate loadings have many possible effects on UHPCs at the microscale and nanoscale, including alterations in the hydration state and bonding present in phases such as calcium silicate hydrate, in addition to fracture and debonding. In this work, the possible chemical and physical changes in UHPCs subjected to high strain rate impact and penetration loads were investigated using a novel technique wherein nanoindentation measurements were spatially correlated with images using scanning electron microscopy and chemical composition using energy dispersive x-ray microanalysis. Results indicate that impact degrades both the elastic modulus and indentation hardness of UHPCs, and in particular hydrated phases, with damage likely occurring due to microfracturing and debonding.

An effective simplified model of composite compression struts for partially-restrained steel frame with reinforced concrete infill walls

Science.gov (United States)

Sun, Guohua; Chuang-Sheng, Walter Yang; Gu, Qiang; DesRoches, Reginald

2018-04-01

To resolve the issue regarding inaccurate prediction of the hysteretic behavior by micro-based numerical analysis for partially-restrained (PR) steel frames with solid reinforced concrete (RC) infill walls, an innovative simplified model of composite compression struts is proposed on the basis of experimental observation on the cracking distribution, load transferring mechanism, and failure modes of RC infill walls filled in PR steel frame. The proposed composite compression struts model for the solid RC infill walls is composed of α inclined struts and main diagonal struts. The α inclined struts are used to reflect the part of the lateral force resisted by shear connectors along the frame-wall interface, while the main diagonal struts are introduced to take into account the rest of the lateral force transferred along the diagonal direction due to the complicated interaction between the steel frame and RC infill walls. This study derives appropriate formulas for the effective widths of the α inclined strut and main diagonal strut, respectively. An example of PR steel frame with RC infill walls simulating simulated by the composite inclined compression struts model is illustrated. The maximum lateral strength and the hysteresis curve shape obtained from the proposed composite strut model are in good agreement with those from the test results, and the backbone curve of a PR steel frame with RC infill walls can be predicted precisely when the inter-story drift is within 1%. This simplified model can also predict the structural stiffness and the equivalent viscous damping ratio well when the inter-story drift ratio exceeds 0.5%.

Steel-concrete bond model for the simulation of reinforced concrete structures

International Nuclear Information System (INIS)

Mang, Chetra

2015-01-01

Reinforced concrete structure behavior can be extremely complex in the case of exceeding the cracking threshold. The composite characteristics of reinforced concrete structure should be finely presented especially in the distribution stress zone between steel-concrete at their interface. In order to compute the industrial structures, a perfect relation hypothesis between steel and concrete is supposed in which the complex phenomenon of the two-material relation is not taken into account. On the other hand, this perfect relation is unable to predict the significant disorders, the repartition, and the distribution of the cracks, which is directly linked to the steel. In literature, several numerical methods are proposed in order to finely study the concrete-steel bond behavior, but these methods give many difficulties in computing complex structures in 3D. With the results obtained in the thesis framework of Torre-Casanova (2012), the new concrete-steel bond model has been developed to improve performances (iteration numbers and computational time) and the representation (cyclic behavior) of the initial one. The new model has been verified with analytical solution of steel-concrete tie and validated with the experimental results. The new model is equally tested with the structural scale to compute the shear wall behavior in the French national project (CEOS.fr) under monotonic load. Because of the numerical difficulty in post-processing the crack opening in the complex crack formation, a new crack opening method is also developed. This method consists of using the discontinuity of relative displacement to detect the crack position or using the slip sign change between concrete-steel. The simulation-experiment comparison gives validation of not only the new concrete-steel bond model but also the new crack post-processing method. Finally, the cyclic behavior of the bond law with the non-reduced envelope is adopted and integrated in the new bond model in order to take

Analyses of Concrete Structures Exposed to Fire

DEFF Research Database (Denmark)

Hertz, Kristian

The text book contains the data and methods necessary for fire safety design of concrete constructions. The methods relate to standard fire as well as to any time of any other fire course.Material data are presented for concretes exposed to fire, and calculation methods are given for the ultimate...... bending capacity of beams and slabs, the ultimate shear capacity of beams, for the instability of columns and walls and for the deflection of prestressed and non-prestressed beams, slabs, walls and columns.All methods have been derived and compared to tests by Kristian Hertz....

Early age damage quantification of actively restrained concrete using inverse analysis

Science.gov (United States)

Albanna, Ali

Early-age cracking can be a significant problem in concrete pavements, floors, and bridge decks. Cracking occurs when the volumetric changes associated with drying, hydration, and temperature reduction are prevented. Good knowledge about the characteristics of early age concrete is necessary to achieve reliable crack control. Volumetric changes due to shrinkage depend on the type of concrete and its components. It has been found that light weight aggregates can work as internal reservoir to supply the concrete matrix with water that is needed during the early age; this process is called internal curing. Also fibers can give more ductility to the concrete and produce less shrinkage. There is a need to better understand the effects of early age uniaxial restraint on long term concrete mechanical performance. In this study, two types of concrete were studied (high performance fiber reinforced concrete and ordinary concrete) under actively restrained loading conditions to assess the effect on the long term fracture toughness and energy. Single edge notched specimens having dimensions of 250 mm x 150 mm x 75 mm and a notch to depth ratio of 0.33 were caste and used in both direct tension and three point bending. The direct tension tests were carried out on a direct tension loading frame constructed in house that was supplied with two mechanical jacks and load cell.

Analysis of elasto-plasticity of a reinforced framework. Report 4. Framework reinforced by a wing wall made of post-placed concrete; Hokyo honegumi no dansosei kaiseki. 4. Atouchi sodekabe ni yoru hokyo honegumi

Energy Technology Data Exchange (ETDEWEB)

Takahashi, H. [Japan Testing Center for Construction Materials, Tokyo (Japan); Shimizu, Y. [Tokyo Institute of Technology, Tokyo (Japan)

1995-09-01

An elasto-plasticity stress analysis was performed on reinforcement using a wing wall made of post-placed concrete as an anti-earthquake reinforcement method for ferro-concrete structures. The analytical values were compared with experimental values, and discussions were given on reasonability of the analytic method. Wing walls made of post-placed concrete were inserted into a three-layered single-spanned model of a reinforced framework made of reinforced mortar (the wing walls being three kinds comprising 1/4 span portion in the first layer, and 1/4 portions in the first and second layers). With the columns loaded and retained with an axial force of 3 tf, a horizontal force was applied from one direction under an assumption that the force forms a uniform distribution. The analysis model was permuted with a wire material having one nodal point and three degrees of freedom as has been reported in the previous paper. The model was divided into the wing wall and the column, and the wing wall portion was permuted into a brace having pins at both ends so that the brace has the withstand strength equivalent to that of the wing wall. A tri-linear type or a bi-linear type was hypothesized for restoring force characteristics of each portion. According to the analytical result, the analytical values agreed relatively well with the experimental values in the load-deformation relationship and fracture conditions, verifying the reasonability of the analytical hypothesis. 5 refs., 5 figs., 3 tabs.

anisotropic crack modelling of reinforced concrete structures with an enhanced kinematics: application to bidimensional elements under cyclic loading

International Nuclear Information System (INIS)

Kishta, Ejona

2016-01-01

Civil engineering buildings, massive and unique, are mostly made of reinforced or prestressed concrete. Sustainability, tightness and safety are the major pillars of a building's performance. Cracking is a major phenomenon which impacts the buildings' behaviour under different loadings in terms of sustainability and structural capacity. Development of numerical models which describe accurately the response of quasi-brittle materials under complex loading remains an important research topic for the scientific community. The objective of this work is the development of a numerical model which represents explicitly cracking of reinforced concrete structures. Concrete and reinforced concrete degradation process, characterised by the appearance of several anisotropic crack families, is described by means of an anisotropic damage model accounting for oriented crack families. The kinematics of this model is enriched with a displacement jump in order to reproduce the development of cracks in the material during loading. This displacement jump is identified as the crack opening. The developed model is validated on simulations of plain concrete structures exhibiting model as well as mixed-mode failure. The performances of the enriched model are shown by the simulation of reinforced concrete structures such as a shear wall submitted to cyclic loading. (author) [fr

Freeze/thaw phenomena in concrete at low temperatures

DEFF Research Database (Denmark)

Johannesson, Björn

2007-01-01

Freeze/thaw damage in concrete is by general practice concluded to be a problem that can be avoided by using air-entraining agents to develop an air bubble structure in the hardened concrete together with the use of a relatively low water to cement ratio in mix. This fact is true for inner damage...

Cast-in-place concrete walls: thermal comfort evaluation of one-storey housing in São Paulo State

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H. M. Sacht

Full Text Available This paper presents a proposal of thermal performance evaluation of a one-storey housing typology (TI24A executed by CDHU - Companhia de Desenvolvimento Habitacional e Urbano do Estado de São Paulo, considering the use of cast-in-place monolithic panels of concrete, with different thicknesses panels (8, 10 and 12 cm and density between 1600 and 2400 kg/m³. In this study, the specific purpose was discussing the influence of the characteristic of concrete walls on the housing thermal performance without slab. Was defined of first parameters of study (definition of the one-storey housing typology, survey about housing users behavior and cities choose and executed computational simulation (winter and summer, for four São Paulo State cities (São Paulo, São Carlos, Santos e Presidente Prudente, with the software Arquitrop 3.0 in a one-storey housing. Was observed that in winter and summer the typologies analyzed, the panels thickness variation had more influence about results than different concrete densities. The minimum level of thermal performance (M in winter has been granted for some cities, with exception of Santos. In summer one of São Paulo city’s typology was attended the minimum level of thermal performance in agreement with standard “NBR 15575 Residential buildings up to five storied - Performance, Part 1: General requirements”.

Local impact effects on concrete target due to missile: An empirical and numerical approach

International Nuclear Information System (INIS)

Ranjan, Rajiv; Banerjee, Sauvik; Singh, R.K.; Banerji, Pradipta

2014-01-01

Highlights: • Local impact effect of hard missile on reinforced concrete targets has been studied. • Review of empirical formulation for predicting local response carried out. • Numerical simulation of experimental test of Kojima (1991) carried out. • Divergence of FE results with those obtained using emperical formulations. • Close match of numerical simulation results with experimental data. - Abstract: Concrete containment walls and internal concrete barrier walls of a Nuclear Power Plant safety related structures are often required to be designed for externally and internally generated missiles. Potential missiles include external extreme wind generated missiles, aircraft crash and internal accident generated missiles such as impact due to turbine blade failure and steel pipe missiles resulting from pipe break. The objective of the present paper is to compare local missile impact effects on reinforced concrete target using available empirical formulations with those obtained using LS-DYNA numerical simulation. The use of numerical simulations for capturing the transient structural response has become increasingly used for structural design against impact loads. They overcome the limits of applicability of the empirical formulae and also provide information on stress and deformation fields, which may be used to improve the resistance of the concrete. Finite element (FE) analyses of an experimental impact problem reported by Kojima (1991) are carried out that are able to capture the missile impact effects; in terms of local and global damage. The continuous surface cap model has been used for modelling concrete behaviour. A range of missile velocity has been considered to simulate local missile impact phenomenon and modes of failure and to capture the concrete response from elastic to plastic fracture. A comparison is then made between the empirical formulations, numerical simulation results, and available experimental results of slab impact tests

Self-healing of polymer modified concrete

Directory of Open Access Journals (Sweden)

Abd_Elmoaty M. Abd_Elmoaty

2011-06-01

Full Text Available Self healing phenomenon of concrete has been observed in traditional, fibrous, self compacting concrete. This phenomenon occurred mainly due to the presence of unhydrated cement particles in the presence of water. Mechanism of polymer in concrete depends on creating a layer and net of polymer around cement particles which enhances the properties of polymer modified concrete. This mechanism may affect the self healing of this type of concrete. This work aims to study the presence of the self healing phenomenon in polymer modified concrete and the related parameters. An experimental investigation on self healing of polymer modified concrete was undertaken. In this research work, effect of polymer type, polymer dose, cement content, cement type, w/cm ratio and age of damage were studied. The healing process extended up to 60 days. Ultrasonic pulse velocity measurements were used to evaluate the healing process. Results indicated that, the self healing phenomenon existed in polymer modified concrete as in traditional concrete. The increase of polymer dose increases the healing degree at the same healing time. This increase depends on polymer type. Also, the decrease of w/cm ratio reduces the self healing degree while the use of Type V Portland cement improves the self healing process compared with Type I Portland cement. Cement content has an insignificant effect on healing process for both concrete with and without polymer. In addition, the increase of damage age decreases the efficiency of self healing process.

Stripping demolition of reinforced concrete by electric heating method

International Nuclear Information System (INIS)

Nakagawa, Wahei; Nishita, Kiwamu; Kasai, Yoshio

1993-01-01

The present paper describes the procedures and results of a series of experiments the authors conducted to verify the efficiency of the electric heating method, previously proposed for so-called stripping demolition by applying electric current through reinforcing bars. In this method, a low voltage high current is run from one end to the other of a reinforcing bar or bars existing in a concrete structure, inducing intense heat in the bar(s) which in its turn brings about cracks in the surrounding concrete mass, facilitating secondary demolition by hammer picks or other means. The experiments were performed on full-scale biological shield wall mock-ups of a BWR and a small reactor. The results of the experiments are summarized as follows. (1) When electric current is applied through reinforcing bars, the bond between concrete and bars is loosened, and cracks start from one bar and progress toward other bars. Under appropriate conditions, the cracks in concrete run from the contact surface at one bar all the way to its the contact surface on another bar. (2) Cracks appear and grow only between two electrodes between which current is applied, not extending out of the area thus defined. (3) The concrete in the region closer to a current-bearing bar is intensely heated, whereas the concrete far from the bars remains nearly unheated. (4) Concrete walls after electric heating of bars disintegrates, if demolished with hammers, with the covering concrete are removed from the remaining portion of the structure together with heated bars, in shapes of flakes. (5) The reinforced concrete collapses in massive pieces of concrete, without generating much dust as is the case with the demolition of a concrete structure not heated by electricity. Results of the experiments show that the electric heating method is worth applying also to the demolition of nuclear power plants where concrete in the radioactivated surface region of shield walls needs to be stripped off in flakes

Monitoring localized cracks on under pressure concrete nuclear containment wall using linear and nonlinear ultrasonic coda wave interferometry

Science.gov (United States)

Legland, J.-B.; Abraham, O.; Durand, O.; Henault, J.-M.

2018-04-01

Civil engineering is constantly demanding new methods for evaluation and non-destructive testing (NDT), particularly to prevent and monitor serious damage to concrete structures. Tn this work, experimental results are presented on the detection and characterization of cracks using nonlinear modulation of coda waves interferometry (NCWT) [1]. This method consists in mixing high-amplitude low-frequency acoustic waves with multi-scattered probe waves (coda) and analyzing their effects by interferometry. Unlike the classic method of coda analysis (CWT), the NCWT does not require the recording of a coda as a reference before damage to the structure. Tn the framework of the PTA-ENDE project, a 1/3 model of a preconstrained concrete containment (EDF VeRCoRs mock-up) is placed under pressure to study the leakage of the structure. During this evaluation protocol, specific areas are monitored by the NCWT (during 5 days, which correspond to the protocol of nuclear power plant pressurization under maintenance test). The acoustic nonlinear response due to the high amplitude of the acoustic modulation gives pertinent information about the elastic and dissipative nonlinearities of the concrete. Tts effective level is evaluated by two nonlinear observables extracted from the interferometry. The increase of nonlinearities is in agreement with the creation of a crack with a network of microcracks located at its base; however, a change in the dynamics of the evolution of the nonlinearities may indicate the opening of a through crack. Tn addition, as during the experimental campaign, reference codas have been recorded. We used CWT to follow the stress evolution and the gas leaks ratio of the structure. Both CWT and NCWT results are presented in this paper.

Ionizing radiation damage in Micrococcus radiodurans cell wall: release of polysaccharide

International Nuclear Information System (INIS)

Mitchel, R.E.J.

1976-01-01

Sublethal 60 Co γ-irradiation of the bacterium Micrococcus radiodurans in aqueous suspension results in a loss of up to 6 percent of its cellular dry weight and 30 percent of its wet weight. In the process some specific cell wall polysaccharides, including a polymer of glucose and N-acylated glucosamine, are released into the surrounding medium. These polysaccharides appear to originate from a hydrophobic site in the middle, lipid-rich, cell wall layer. The damage to this layer which results in the release of these and other polymers may be due to a disruption of this hydrophobic site. The polysaccharide containing glucose and N-acylated glucosamine exists as a high molecular weight polymer in unirradiated cells, but irradiation causes some degradation prior to release. In a free state this polysaccharide is considerably less sensitive to radiolytic degradation than in a bound state. Free radicals generated from surrounding water by ionizing radiation initiate the release, hydroxyl radicals being the most important species. Oxygen protects the cell wall against loss of the polysaccharides, apparently by a mechanism which does not depend on the ability of O 2 to scavenge hydrogen atoms and aqueous electrons

Experimental study of a foam concrete based on local Tunisian materials

Directory of Open Access Journals (Sweden)

Ellouze Dorra

2018-01-01

Full Text Available The building sector in Tunisia is very energy-intensive, the largest share of energy consumption comes from factories of building materials namely brick and cement plants. This work is part of the reduction of the energy bill in the building envelope. Indeed, the foam concrete can be walls in single or double wall with better insulating power. This paper presents an experimental study on the technical problems related to the formulation and manufacture of a new cellular concrete in Tunisia, called "foam" concrete, from Tunisian local materials. Indeed, six varieties of sand of different provenance and grain size will be analyzed, the "good" sand is the one that is best suited for the manufacture of foam concrete. Two clean, fine-grained (0/2mm rolled grain sands were retained. Then four foam concretes were formulated using each time a single type of sand and varying the density namely 0.8 and 1. These four formulations were tested mechanically and thermally. The results found showed that compressive strengths do not exceed 1.5 MPa at 28 days. Thus, the foam concrete can be used only as a filling concrete in non-load bearing elements such as partition walls. The guarded hot plate method was used to determine the thermal conductivities of the four foamed concretes studied. A low thermal conductivity was found of the order of 0.22 W/m°K which prove the insulating power of foam concrete.

Method of constructing shielding wall

International Nuclear Information System (INIS)

Nagao, Tetsuya.

1990-01-01

For instance, surfaces of lead particles each formed into a sphere of about 0.5 to 0.3 mm grain size are coated with a coating material of a synthetic resin comprising a polymeric material such as teflon. Subsequently, the floated lead particle are kneaded with concrete materials and then poured into a molding die by way of a hose. After coagulation, the molding die is removed to complete shielding walls in which lead particles are scattered substantially at an equal distance. In this way, since the lead particles are mixed into the shielding walls, shielding effects can be improved by so much as the lead particles are mixed, thereby enabling to reduce the thickness of the shielding walls. Further, since the lead particles are coated with the coating material, the lead particles are insulated from the concrete materials, thereby enabling to prevent the corrosion of the lead particles. Furthermore, since the lead particles and the concrete materials can be transported with ease, operation labors can be reduced. (T.M.)

Diaphragm walling for Sizewell B sets records

International Nuclear Information System (INIS)

Anon.

1988-01-01

The first phase of construction of the Sizewell-B nuclear reactor has been completed. This was the building of a diaphragm wall around the site. It is one of the largest and deepest diaphragm walls to be installed in Europe. The site can be pumped dry of groundwater and the foundations constructed in the dry. The specifications of the wall and its construction, using two Hydrofraise excavation rigs, are described. The excavated material is brought up as a slurry and the (bentonite) slurry is cleaned and desanded. Most of the wall has been formed using a plastic concrete but reinforced concrete has been used for some stretches. The diaphragm wall, which is 1258m long and 55m deep on average, was built in 19 weeks. (U.K.)

Funciones de vulnerabilidad calculadas para edificaciones en muros de hormigón reforzado Calculated seismic vulnerability functions for building in walls of reinforced concrete

Directory of Open Access Journals (Sweden)

Esperanza Maldonado Rondón

2010-04-01

Full Text Available En este documento se presenta una metodología que valora el nivel de daño que pueden alcanzar las edificaciones correspondientes al sistema estructural de muros de hormigón reforzado. El modelo estima un índice de vulnerabilidad calculado en función de las características de la estructura que más influyen en su comportamiento sísmico, y lo relaciona con un índice de daño, que a su vez depende de la acción del movimiento sísmico. El modelo estima diferentes grados de vulnerabilidad, y por consiguiente, define distintos niveles de daño ante una misma acción. La relación de la vulnerabilidad con el daño se materializa mediante una forma continua con las funciones de vulnerabilidad. El modelo se construyó sobre una muestra de edificaciones reales e hipotéticas las cuales representan las características más relevantes de las edificaciones de este tipo en el medio colombiano.This document contains a methodology to assess the level of damage that buildings with reinforced concrete wall structural system may reach. The model estimates a vulnerability rate calculated in function of structure characteristics that most influent a seismic behaviour, and relates this value to a damage rate, which, in turn, depends on the action of seismic movements. The model estimates different levels of vulnerability and, consequently, defines different damages produced the same action. The vulnerability / damage ratio is materialized to vulnerability function in a continuous manner. The model was constructed on a sample of real and hypothetical buildings representing the most relevant characteristics of this type of buildings in Colombia.

Analysis of large concrete storage tank under seismic response

Energy Technology Data Exchange (ETDEWEB)

Le, Jingyuan; Cui, Hongcheng; He, Qiang; Ju, Jinsan [China Agricultural University, Beijing (China); You, Xiaochuan [Tsinghua University, Beijing (China)

2015-01-15

This study adopted the finite element software ABAQUS to trace the dynamic response history of large reinforced concrete storage tank during different seismic excitations. The dynamic characteristics and failure modes of the tank's structure were investigated by considering the rebar's effect. Calculation results show that the large concrete storage tank remains in safe working conditions under a seismic acceleration of 55 cm/s{sup 2}. The joint of the concrete wall and dome begins to crack when seismic acceleration reaches 250 cm/s{sup 2}. As the earthquake continues, cracks spread until the top of the wall completely fails and stops working. The maximum displacement of the concrete tank and seismic acceleration are in proportion. Peak displacement and stress of the tank always appear behind the maximum acceleration.

Experimental Investigation into Pull-Out Strength of Foamed Concrete Using Different Types of Screw

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Othuman Mydin M.A.

2014-01-01

Full Text Available This study focuses on the results of the comprehensive strength test to quantify the mechanical properties of the screw’s pullout strength on foamed concrete. Foamed concrete is classified as lightweight concrete that been produced by cement paste or mortar in which air-voids are entrapped in the mortar by a suitable foaming agent. These days, the use of foamed concrete has been recognized in the construction industry as wall blocks, wall panels and also material floor and roof screeds. Hence, the applications of this material should be maximized as it is multi-functional. As we know, the use of screws on the wall or ceiling is common in a building. The objective of this research is to examine and determine the pullout strength of various properties and types of screws in lightweight foamed concrete with various densities that may depict the best result of the pullout strength on foamed concrete. To visualize the different results of pullout strength, screws with and without wall plug will be used as well. The pullout strength will be tested using the Universal Testing Machine where it shall measure the ultimate load of the screws attached to the foamed concrete may resist.

Simple estimating method of damages of concrete gravity dam based on linear dynamic analysis

Energy Technology Data Exchange (ETDEWEB)

Sasaki, T.; Kanenawa, K.; Yamaguchi, Y. [Public Works Research Institute, Tsukuba, Ibaraki (Japan). Hydraulic Engineering Research Group

2004-07-01

Due to the occurrence of large earthquakes like the Kobe Earthquake in 1995, there is a strong need to verify seismic resistance of dams against much larger earthquake motions than those considered in the present design standard in Japan. Problems exist in using nonlinear analysis to evaluate the safety of dams including: that the influence which the set material properties have on the results of nonlinear analysis is large, and that the results of nonlinear analysis differ greatly according to the damage estimation models or analysis programs. This paper reports the evaluation indices based on a linear dynamic analysis method and the characteristics of the progress of cracks in concrete gravity dams with different shapes using a nonlinear dynamic analysis method. The study concludes that if simple linear dynamic analysis is appropriately conducted to estimate tensile stress at potential locations of initiating cracks, the damage due to cracks would be predicted roughly. 4 refs., 1 tab., 13 figs.

Nuclear magnetic resonance analysis of freeze-thaw damage in natural pumice concrete

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