Concrete Shear Research Articles

Buckling Behavior of Steel Plates and Concrete Filled Composite Shear Walls Related Nuclear Power Engineering

Based on the program of nuclear power engineering, the in-plane buckling behavior of Steel plates and concrete filled composite shear wall (SCSW) was investigated. 9 1/5 scaled specimens were conducted under horizontal cyclic load and constant vertical load. The parameters such as the space of studs, the vertical load, the form of connectors, and the thickness of the steel plate were designed to research the affection on the buckling of the steel plate. According to the results of tests, it can be seen that the bulge of the steel plate occurred at about 50mm above the top of the foundation beam. The bulge can be connected as a whole in the specimens with studs only, but not in the specimens with stiffeners. Finite element models were performed to simulate the buckling behavior of the steel plate, and the results were found to be in good agreement with the test results. The buckling stress of the steel plate was calculated by equations based on the measuring data. It was found that they were smaller than that of finite element analysis. The more accurate simulation was needed.

Efficient Simulation of RC Shear Walls in High-Rise Buildings Using a Practical Multi-Cross-Line-Model

ABSTRACT This paper presents a novel model for reinforced concrete (RC) shear walls, named as multi-cross line model (MCLM), combining the concepts of micro- and macro-shear wall models by simulating the stress–strain relationships at the material level using a set of concrete or steel bars, and thereof calculating the resultant stresses. The two-dimensional MCLM jointly with the multilayer shell element can simulate the three-dimensional behaviors of the RC shear walls. The proposed model is validated by using three RC shear wall specimens under cyclic loading conditions. Besides, the huge potential for practical use of this model is also illustrated.

Correlation between shear and normal strength for brittle reinforced concrete member considering internal stress condition of concrete

Formulas used to predict shear strength of reinforced concrete in different standards do not always correspond to each other due to the complexity of the shear transfer mechanism. Currently there is no generally accepted method of shear strength pridiction, however, traditionally, shear strength anticipation of a structural concrete elements is performed differently on members with or without shear reinforcement. These empirical approches tend to predict the shear strength too conservatively; alternatively, shear strength of concrete can be easily predicted by Mohr-Coulomb theory. In case of high-axial load and low shear reinforcement, the strength is likely to be determined by the concrete's shear crack. Therefore, a method to predict the strength of concrete with Mohr-circle has been proposed but the circles crossed the boundary and could not evaluate the strength correctly. Mohr circle can be used for prediction of diagonal tension failure strength but the circle cannot be evaluated. In this paper, Mohr circles were investigated considering all steps of cyclic loading until shear crack occurred. It also investigates a correlation between shear strength and normal strength through recognition of the Mohr-Coulomb failure criteria for each specimen.

Shear strength of joints between reinforced concrete slabs and steel-plate–concrete walls

In the study reported in this paper, the shear friction behaviour of a seismic-resistant joint between in situ reinforced concrete slabs and offsite-manufactured steel-plate–concrete composite shear walls in a nuclear power plant was investigated. The joint shear friction strength and safety factor were evaluated experimentally based on the Korean electric power industry code. It was found that the joint had sufficient shear strength against earthquake loading by installing top and bottom reinforcement in the slab and then extending the reinforcing bars into the wall module. With polytetrafluoroethylene sheets inserted, it was confirmed that the joint had greater shear strength than the design shear strength. In addition, the results indicated that the shear friction strength at the joint was about 300 kN, that the strength resisted by the reinforcement increased in accordance with increasing displacement, and that the bottom reinforcement carried higher shear strength than the top. Specimens with bottom reinforcement were found to have over 40% higher shear strength than specimens without bottom reinforcement. Finite-element analyses for the connections were also performed to verify the structural behaviour and failure modes of the test specimens. It was found that the analytical model expressed the experimental results comparatively well.

Seismic Axial Collapse of Shear Damaged Heavily Reinforced Shear Walls Experiencing Cyclic Tension–Compression Excursions: A Modified Mohr’s Axial Capacity Model

ABSTRACT A special class of reinforced concrete (RC) shear wall is identified with short shear span, attributed to the high coupling degree in the elastic design of tall buildings located in low-to-moderate seismicity regions. The short shear span characteristic precludes plastic hinge formation and increase the susceptibility of shear failure during seismic events. It is noted that shear damage alone does not indicate collapse by default. This paper formulates a Modified Mohr’s Axial Capacity Model associated with out-of-plane buckling, to quantify the residual axial capacity of shear-damaged heavily reinforced walls. The model was benchmarked against four walls previously tested to axial failure.

Effect of Alkali-Silica Reactivity Damage to Tip-Over Impact Performance of Dry Cask Storage Structures

This paper investigates the effect of concrete degradation due to alkali-silica reactivity (ASR) and its effect on the performance of vertical concrete casks in the case of a hypothetical tip-over event. ASR is one of the major problems in certain concrete structures exposed to high relative humidity and temperature. Using the first order kinetic model, the mechanical and environmental effects of degradation are modeled for a dry-cask storage structure under the conditions that ASR is completely extended. Following the degradation, a tip-over impact simulation was performed and compared with that of an intact cask in terms of failure modes, damage patterns, stresses, and accelerations. It was seen that concrete crushing and shear banding are major failure modes in the cask with intact concrete, but in the case of the ASR affected cask, the concrete is fully damaged and a longitudinal crack which separates the cask into two parts propagates through the outerpack.

Behavior of self-compact reinforced concrete deep beams with small shear span to depth ratio

This research is devoted to investigate the experimental and theoretical behavior of deep beams under monotonic two points loading. An experimental program examining six RC deep beams is carried out. The investigated parameters include shear span to depth ratio varying from 1.0 to 0.276. A comparative study is conducted in this paper by using finite element software ANSYS. The experimental and numerical results show that concrete strength and shear span to depth ratio are the two most important parameters in controlling the behavior of RC deep beams. Comparison of experimental results was made with corresponding predicted values using the Strut and Tie procedure presented ACI 318M-11Code and with other procedures mentioned in the literature. It was found that the Strut and Tie procedure presented in ACI 318M-11Code give conservative results as compared with the experimental tested results. The results showed reliability of analysis in predicting deep beams behavior in terms of failure load, failure mode as well as crack propagation.

Deflection calculation method on GFRP-concrete-steel composite beam

A calculation method was presented to calculate the deflection of GFRP-concrete-steel beams with full or partial shear connections. First, the sectional analysis method was improved by considering concrete nonlinearity and shear connection stiffness variation along the beam direction. Then the equivalent slip strain was used to take into consideration of variable crosssections. Experiments and nonlinear finite element analysis were performed to validate the calculation method. The experimental results showed the deflection of composite beams could be accurately predicted by using the theoretical model or the finite element simulation. Furthermore, more finite element models were established to verify the accuracy of the theoretical model, which included different GFRP plates and different numbers of shear connectors. The theoretical results agreed well with the numerical results. In addition, parametric studies using theoretical method were also performed to find out the effect of parameters on the deflection. Based on the parametric studies, a simplified calculation formula of GFRP-concrete-steel composite beam was exhibited. In general, the calculation method could provide a more accurate theoretical result without complex finite element simulation, and serve for the further study of continuous GFRP-concrete-steel composite beams.

Experimental Study on the Shear Performance of Shallow Hinge Joints for Prefabricated Hollow Slab Bridges

To investigate whether shallow hinge joint fracture was caused by shear stress or flexural stress, during the demolition and reconstruction of Xiaojiang River bridge, two original girders were collected and shipped to the lab, and the shallow hinge joint between the two girders was rebuilt. Tests were performed to investigate the cracking load, failure mode, and force transmission performance of the hollow slab girder and shallow hinge joint under vehicle load. The test result shows that under eccentric load, when the load increases to 365 kN, the midspan bottom slab of the testing girder starts to fracture; as the load increases to 560 kN, the roof slab of the testing girder starts to fracture; the hinge joint has a maximum horizontal opening of 0.153 mm and vertical relative displacement of 0.201 mm; during the entire test loading process, the shallow hinge joint structure does not develop fracture and shear failure; and the shallow hinge structure demonstrates excellent shear stress transmission performance. In addition, based on hinge slab theory, the hinge joint internal force under vehicle load was calculated. Based on ACI 318‐05 specification, CAN/CSA‐S6‐00, and JTG D61‐2005, the hinge joint shear bearing capacity was calculated. Hinge joint stress resistances calculated from the three specifications all exceed the internal force. Among them, the calculation results from ACI 318‐05 and CAN/CSA‐S6‐00 are similar, while the result from JTG D61‐2005 specification significantly exceeds the internal force, which is mainly because the designed concrete direct shear strength fvd in the Chinese specification does not consider factors such as bonding surface coarseness, concrete pouring sequence, and material properties. Theoretical calculations and tests show that the actual failure mode of the shallow hinge joint in prefabricated hollow slab girder bridges is not caused by shear stress.

Breakout shear strength of cast-in-place anchors using shaking table tests

The concrete breakout shear strength of stirrup-reinforced cast-in-place anchors during earthquakes was experimentally evaluated. Uncracked and cracked concrete specimens were manufactured using M36 anchors reinforced with D10 stirrups (spacing, 100 mm; edge distance, 180 mm). Shaking table tests were performed to assess the dynamic strength of the reinforced anchors using the Northridge seismic wave. The experimental results showed that the dynamic shear resistance was slightly higher than the static shear resistance due to the strain rate effect of the material. In addition, Etag 001, which is based on the resistance of concrete, and ACI 318, which accounts for the resistance of concrete or steel reinforcement to evaluate the strength of the reinforced anchors, yielded conservative values for the static and dynamic shear strengths of the stirrup-reinforced anchors. An appropriate method that can account for both concrete and stirrup resistance to evaluate the design shear strength of stirrup-reinforced anchors under earthquakes is proposed.

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

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.

Study on Experiment of Concrete Strength with Numerical Simulation

The limit state of bearing capacity of concrete and collapse state is discussed by the overload method of finite element limit analysis and finite difference software FLAC3D. Firstly, the shear strength of concrete with different strength grade is verified through the numerical limit analysis. Besides, a new method to judge the failure of concrete by calculating the concrete limit shear strain increment value is proposed. In addition, the collapse surface position and shape is simulated and the result is compared with the actual state of the destruction. The finite element limits analysis method have been tried to applied in concrete in this paper.

Nonlinear modelling and seismic behaviour of precast concrete structures with steel shear walls

A new structural system consisting of precast concrete frames and steel shear walls (SSW's) is introduced and studied numerically in this paper. Two different models, first using ''exact'' FEM and second using approximate equivalent strip model (ESM), are utilized for analysis of such a system with nonlinear static (pushover) procedure. In the FEM model use is made of shell elements while the ESM benefits from simple links that replace the wall panels in the model and are oriented such that they work in tension. Because of good agreement observed between the results of the models in smaller structures, for taller buildings only the ESM approach is followed where computationally applying the FEM approach is impractical. The lateral behaviour of the systems under consideration is investigated with regard to parameters such as number of stories and beam-column connection type. As a result, the ductility, overstrength and response modification factors are calculated for this new structural system as quantities required for their practical design.

Analytical performance evaluation of modified inclined studs for steel plate concrete wall subjected to cyclic loads

An analytical study was conducted to investigate the effect of the shape and spacing of modified inclined studs used as shear connector between concrete and steel plate on the cyclic behavior of steel plate concrete (SC) shear wall. 9 different analysis cases were adopted to determine the optimized shape and spacing of stud. As the results, the skeleton curves were obtained from the load-displacement hysteresis curves, and the ultimate and yielding strengths were increased as the spacing of studs decrease. In addition, the strength of inclined studs is shown to be bigger compared to that of conventional studs. The damping ratios increased as the decrease of stiffness ratio. Finally, with decreasing the spacing distance of studs, the cumulative dissipated energy was increased and the seismic performance was improved.

저층형 철근콘크리트 전단벽의 전단강도 평가를 위한 스트럿-타이 모델

The previous strut-and-tie models (STMs) to evaluate the shear strength of squat shear walls with aspect ratio less than 2.0 do not consider the axial load transfer of concrete strut and individual shear transfer contribution of horizontal and vertical shear reinforcing bars in the web. To overcome the limitation of the existing models, a simple STM was established based on the crack band theory of concrete fracture mechanics. The equivalent effective width of concrete strut having a stress relief strip was determined from the neutral axis depth and effective factor of concrete strength. The shear transfer mechanism of shear reinforcement at the extended crack band zone was calculated from an internally statically indeterminate truss system. The shear transfer capacity of concrete strut and shear reinforcement was then driven using the energy equilibrium in the stress relief strip and crack band zone. The shear strength predictions of squat shear walls evaluated from the current models are in better agreement with 150 test results than those determined from STMs proposed by Siao and Hwang et al. Furthermore, the proposed STM gives consistent agreement with the observed trend of the shear strength of shear walls against different parameters.

Displacement ductility ratio-based flexural design approach of reinforced concrete slender shear walls

Displacement ductility ratio-based flexural design approach of reinforced concrete slender shear walls

Satisfactory margin of safety against shear failure of lightweight reinforced concrete beams: 3D finite element modeling

In concrete structures a satisfactory margin of safety should be ensured against shear failure that might occur under the forces that act upon the structure during its lifetime. Therefore, knowledge of the design and construction guidelines for shear of normal and high strength Lightweight Concrete (LWC) beams is desirable to better understand the structural design and performance of LWC beams. Thus, research is required to address and investigate the contribution of concrete compressive strength, shear span to depth ratio, tensile reinforcement ratio, and shear stirrups spacing as well as the failure mechanisms in situation of using LWC beams. As a result, this paper presents Nonlinear Finite Element Analysis (NLFEA) results of reinforced LWC beams because of the main benefits of NLFEA by providing substantial savings in the cost, time, and effort compared with the fabrication and experimental testing of structure elements as well as the ability to change any parameter of interest and the capability of demonstrating any interesting behavior at any load value and at any location in the system. After reasonable validation of NLFEA with the experimental test results, the NLFEA was expanded to provide a parametric study of fourteen hundred LWC beams that correlates the ultimate shear stress to studied parameters. Results indicated that the lower bound was for the beams with shear span to depth ratio, concrete compressive strength, and tensile reinforcement ratio of 5, 27.5 MPa, and 0.71%, respectively, and the upper bound was for the beams with shear span to depth ratio, concrete compressive strength, and tensile reinforcement ratio of 1, 68.8 MPa, and 2.21%, respectively. In addition, the performance of simulated models was investigated in terms of ultimate load capacity, ductility and energy absorption. Finally, a new parametric model is introduced in this paper to compute the shear strength of reinforced LWC beams without stirrups. The proposed equation was compared with numerous previous analytical models and founded that some models to be in a good agreement.

Development for twin shear damage constitutive model of concrete

The concrete material constitutive model has limitations at present stage. Mazars concrete damage equation obtained by uniaxial test was extended to the triaxial state based on Yu Maohong Twin Shear constitutive model and the concept of damage plane. Material stiffness damage degradation impact on the yield process of concrete yield plane was considered. This article developed a concrete Twin Shear damage constitutive model in FLAC3D environment. The model is simple and easy to practical engineering applications, and the model has high accuracy. Thereby, this paper tries to explore a new damage constitutive model for concrete.

Effect of hybrid fibres on the shear and durability behaviour of high performance concrete

An attempt has been made to investigate the effect of hybrid fibres on the shear strength and behaviour of high performance concrete (HPC). A total of 24 reinforced concrete beams of size 100 × 150 × 1,200 mm were cast and tested under two–point loading. No shear reinforcement was provided in the shear span to ensure shear failure. The main variables considered were the volume fraction of: 1) crimped steel fibres viz. 0.5% and 1.0%; 2) polypropylene fibres viz. 0.1%, 0.15% and 0.2%. Test results indicate that addition of fibres in hybrid form significantly improves the first crack load (about 48%) and ultimate shear strength (about 37%). Prior to the beam testing, the basic mechanical properties and durability characteristics of hybrid fibre reinforced high performance concrete (HFRHPC) were also evaluated. The material test results showed that the HFRHPC has excellent performance in terms of mechanical and durability properties.

Evaluation of Minimum Stirrups Ratio in Reinforced Concrete Flexural Members

The minimum web reinforcement specified by many codes of practice is intend to maintain adequate reserve strength and ductility. So, reasonable value of minimum stirrup ratio in reinforced concrete flexural members is a noteworthy problem, which is to prevent members occur inclined tension brittle failure in shear design. Especially in seismic design, in order to ensure the structural members to achieve ‘strong shear weak bending’ the condition, reasonably determine the minimum stirrup stirrup ratio is a key component to ensure ductile failure occurs. Analogy to determine the principles flexural members minimum reinforcement ratio, combined with European norms to determine the principles of the minimum rate of stirrup, an expression has been proposed in non-seismic reinforced concrete beam shear design with considering the ratio of shear span. The minimum shear reinforcement predicted by the proposed expression makes the required minimum stirrup ratio have been harmonized in shear design of both cases which in general flexural members and under concentrated load members.