High-strength Concrete Shear Wall Research Articles

Experimental study on horizontal low-cycle loading of high-strength concrete medium high shear wall with cold-formed steel braces

This study presents the findings from experimental tests conducted on four medium-high shear walls with a shear span ratio of 1.8. The focus of the study is to investigate the effect of different types of cold-formed steel diagonal braces on the seismic performance of the shear walls. The specimens were subjected to horizontal low-cycle loading to observe their failure behavior, including cracking load, ultimate displacement, yield load, and ultimate load. Additionally, a comparative analysis of the stress distribution in the cold-formed steel braces, braces with different steel ratios but of the same type, and braces with the same steel ratio but of different types, was conducted. The research findings indicated that the inclusion of an appropriate amount of cold-formed steel braces with an appropriate steel ratio significantly improved the ultimate displacement and shear stiffness of the structures. The cold-formed steel braces effectively restrained crack development and prevent structural collapse after failure. However, it was observed that the lattice-type braces failed to confine the internal concrete to form a compressed concrete strut capable of resisting both shear and bending moment simultaneously. The addition of cold-formed steel braces was found to be advantageous in improving the shear stiffness of the specimens. In particular, the cold-formed angle steel braces in SRHCW-2 were more effective in enhancing the shear stiffness compared to the lattice-type cold-formed steel braces in SRHCW-3. Moreover, an increase in the steel brace ratio on top of the lattice-type cold-formed steel braces in SRHCW-3, as observed in SRHCW-4, contributed to a certain improvement in the structural shear stiffness.

Experimental investigation of post-fire seismic behavior of reinforced high-strength concrete shear walls

Reinforced high-strength concrete shear walls (RHSCSWs) are widely used for lateral load-resisting systems in tall buildings. Due to the high possibility of explosive spalling of high-strength concrete under high temperature, the structural performance of high-strength concrete shear wall may be greatly reduced after fire, which should be paid attention to by the engineering community. In this study, the post-fire seismic performance of RHSCSWs was investigated. Twelve RHSCSW specimens were fabricated and tested under an ISO-834 standard fire. Thereafter, 10 of these specimens were subjected to an in-plane cyclic load to evaluate their post-fire seismic performance. The remaining two specimens were subjected to concentric axial loads because they were severely damaged by explosive concrete spalling in the fire. The investigated parameters of the specimens included the concrete strength, fire exposure condition (one-side or four sides), fire duration, aspect ratio, axial load ratio, surface mortar layer, and strengthening technique (i.e., whether an X-shaped steel brace was installed). Their fire and post-fire structural performances were carefully assessed. The concrete walls with a cube compressive strength of 75.8 MPa were prone to explosive spalling in fire, whereas the concrete walls with a cube compressive strength of 60.3 MPa were not. Moreover, concrete shear walls with surface mortar layers were more likely to experience explosive spalling in fire than walls without such layers. With increasing axial load ratio, the horizontal load-bearing capacities of the shear walls after the fire first increased and then decreased, with the critical value being in the range 0.2–0.25. The specimens damaged by explosive spalling retained considerable axial load-bearing capacities (i.e., 69 % of the sectional concrete compression-bearing capacity of the unfired wall).

Experimental study on the seismic performance of short shear walls comprising cold-formed steel and high-strength reinforced concrete with concealed bracing

Abstract This study investigates the seismic performance of a composite structure comprising cold-formed steel and high-strength concrete. Four short shear walls composed of cold-formed steel and high-strength concrete, namely, one specimen without diagonal bracing, one with angle-steel bracing, and two with lattice bracing, were designed for testing their low cyclic loading. The cracking load, ultimate displacement, maximum horizontal bearing capacity, failure process, hysteretic curve, and skeleton curve of the four specimens were obtained during the test. The results showed that the use of cold-formed steel-concealed bracing in the high-strength concrete short shear wall can effectively change the failure mode of the wall into bending shear failure with good ductility. An analysis of the energy dissipation of the four specimens revealed that the energy dissipation capacity and ductility of high-strength concrete short shear wall with cold-formed steel concealed bracing were improved, indicating that the use of cold-formed steel concealed bracing greatly improved the total energy dissipation capacity of high-strength concrete short shear wall. The calculated shear bearing capacity in the diagonal section of the wall with concealed bracing was compared with the measured one. Considering specifications, a formula for calculating the shear capacity in the oblique section of short shear wall with concealed bracing was proposed.

The effects of steel fibers and boundary elements on the seismic behavior of high-strength concrete shear walls

Six shear walls using high-strength concrete and high-strength steels were studied by conducting cyclic load tests, including two reinforced concrete shear walls, and four composite walls reinforced by concrete-filled steel tubes (CFSTs). The effects of steel fibers and boundary element forms on the cyclic behavior of the walls were investigated. Research founds that the steel fiber reinforced specimens showed lighter damage degree, lower deformation capacity, and lower proportion of shear deformation than the non-fiber reinforced specimens. Among the three types of specimens with different boundary elements, steel fibers had the greatest influence on the composite walls with concrete-encased CFST columns in boundary zone. Compared the two types of composite walls reinforced by CFSTs which were designed by the principle of “equal vertical bearing capacity of the boundary elements”, the walls with outer CFST columns showed better energy dissipation capacity than the walls with concrete-encased CFST columns. Finally, considering the stress characteristics and the constraint effect of boundary elements of different kinds of shear walls, the simplified calculation model of load-carrying capacity and the finite element analysis model were established and verified.

Predicting nominal shear capacity of reinforced concrete wall in building by metaheuristics-optimized machine learning

Reinforced concrete shear walls are used in many structural systems to resist earthquake loading. In recent earthquakes, shear wall buildings have tended to perform well. Modern building codes include provisions concerning shear capacity, which are recognized for their effectiveness. Studies have demonstrated that the American Concrete Institute (ACI) 318-19 provision uses a low safety factor and does not cover high-strength concrete shear walls whereas the Eurocode 8 provision is overly conservative. A rational method for predicting shear wall capacity could be used as an alternative to the simplified provision in the codes. Nevertheless, the use of rational methods may present some difficulties for structural engineers because they require an iterative calculation to determine the peak strengths of shear walls. Accordingly, an appropriate data-driven machine learning scheme that accurately determines shear capacity is needed. Three experimental cases that involve various input variables are adopted herein to train single models and ensemble models. Numerical analytics show that the best result is achieved by using extreme gradient boosting (XGBoost), which involves conventional parameters and synthetic parameters that are inspired by the ACI shear wall strength equation. Subsequently, two metaheuristic optimization algorithms are used to fine-tune the hyperparameters of the generally recognized XGBoost. Two proposed metaheuristically hybrid models, jellyfish search (JS)-XGBoost and symbiotic organisms search (SOS)-XGBoost, outperform the ACI provision equation and grid search optimization (GSO)-XGBoost in the literature in predicting the nominal capacity of reinforced concrete shear walls in buildings. Metaheuristics-optimized machine learning models can be used to improve building safety, simplify a cumbersome shear capacity calculation process, and reduce material costs. The systematic approach that is utilized herein also serves as a general framework for quantifying the performance of various mechanical models and empirical formulas that are used in design standards.

Seismic behavior of steel fiber reinforced high strength concrete shear walls with different embedded steel configurations

Four steel fiber reinforced high strength concrete shear walls with different embedded steel configurations were conducted under quasi-static tests, to investigate the influences of the diagonal steel bar bracings in the wall web, the embedded steel tubes in the boundary zone, and the concealed steel truss on the seismic behavior of the proposed shear walls. Furthermore, the finite element modelling and the parametric analysis were conducted and verified against the test results. Research shows that both the reinforcement bracings and the channel steel bracings restrained the development of cracks and decreased the crack widths, especially the channel steel bracings, which showed a more remarkable effect on alleviating the damage of the wall. The two types of the concealed bracings could slow down the stiffness degradation rate, and enhance the plastic deformation capacity of the shear walls. The finite element analysis indicated that a reasonable axial load ratio was conductive to exert the cyclic behavior of the concealed bracings. For the steel truss reinforced concrete walls, the increase of the cross sectional ratio of steel tubes within a reasonable range could improve the co-working performance for the wall panel and the boundary columns.

Experiment and numerical analysis on seismic performance of resilient shear walls using high strength recycled aggregate concrete

In this paper, ultra-high strength bars (UHSB) was innovatively applied to the high-strength recycled aggregate concrete (RAC) shear walls to achieve resilient performance. In order to explore the resilient and seismic performance of the shear wall, five specimens with shear span ratio of 2.2 were tested under cyclic loading. The variables also included the type of longitudinal reinforcement in boundary elements, the presence of anti-corrosion coating in UHSB and the replacement ratio of recycled coarse aggregate (RCA). The results showed that the use of UHSB in the boundary elements significantly improved secondary stiffness and reduced the residual displacement and residual crack width of the shear walls. The anti-corrosion coating decreased bond strength between UHSB and RAC, but it had negligible effect on the seismic and resilient performance of the specimens before 2% drift ratio. Increasing replacement ratio of RCA slightly decreased the lateral force of the specimens under the same drift ratio, but the walls represented satisfactory resilient performance. In addition, finite element models were established in ABAQUS, and the effect of UHSB bond performance, the strength of longitudinal reinforcement with anti-corrosion coating, and the substitution rate of UHSB were analyzed. The results showed that the numerical analysis results were in good agreement with experiment results.

An Experimental Study on the Seismic Performance of High-Strength Composite Shear Walls

In order to study the seismic performance of high-strength concrete composite shear walls with embedded steel strips, four tests for high-strength concrete composite shear walls with embedded steel strips (SPRCW-1 to SPRCW-4) were constructed and tested. Based on the test results, a discussion is provided in the present study on the hysteresis curve, backbone curves, and strain of steel plate and distributed reinforcement of high-strength concrete mid-rise and high-rise composite shear walls with embedded steel strips under different steel ratios and different steel strip positions. The test results reveal that in high-strength composite shear walls with embedded steel strips, the ductility of the test specimen can be effectively improved when the ratio of the steel strip reaches a certain level. In parallel, when the embedded steel strip is placed on both sides of the walls, the steel strip can function better. The ultimate displacement is better than when the steel strip is placed in the middle of the walls, and can effectively improve the seismic performance of the walls. The scheme with embedded steel strips is more convenient and economical for construction, which is suitable for popularization and application in middle-high buildings in highly seismic regions.

Seismic Behavior of Steel-Fiber-Reinforced High-Strength Concrete Shear Wall with CFST Columns: Experimental Investigation

To improve the seismic behavior of shear walls, a new composite shear wall composed of a steel-fiber-reinforced high-strength concrete (SFRHC) web and two square concrete-filled steel tube (CFST) columns, namely a steel-fiber-reinforced concrete shear wall with CFST columns, is proposed in this paper. Therefore, the main purpose of this paper is to present an experimental investigation of the seismic behavior of the SFRHC shear wall with CFST columns. Pseudo-static tests were carried out on seven composite shear walls, and the seismic performance of the shear walls was studied and quantified in terms of the aspects of energy consumption, ductility and stiffness degradation. Furthermore, the experimental results indicated that adding steel fiber can effectively restrain the crack propagation of composite shear walls and further help to improve the ductility and energy dissipation capacity of composite shear walls and delay the degradation of their lateral stiffness and force. Moreover, the seismic behavior of the SFRHC shear wall with CFST columns was obviously superior to that of the conventionally reinforced shear wall, in terms of load-bearing capacity, ductility, stiffness and energy dissipation capacity, because of the confinement effect of the CFST columns on the web. Finally, the preliminary study demonstrated that the composite shear wall has good potential to be used in regions with high seismic risk.

Cyclic behavior of high-strength concrete shear walls with high-strength reinforcements and boundary CFST columns

The reinforced concrete shear wall with boundary concrete-filled steel tube (CFST) columns features high lateral strength and seismic ductility. Combining the use of high-strength concrete and high-strength reinforcements for this kind of composite shear wall has attracted widespread attention recently. To investigate the cyclic performance of high-strength concrete shear walls with high-strength steel bars and boundary CFST columns, five specimens with varying concrete strengths, steel tube types, steel fiber ratios, and strengthening measures using bottom steel plates were tested under constant axial loading combined with lateral cyclic loading. The test failure modes and the measured components of the flexural and shear displacements indicated flexural-dominated failure patterns for all the shear walls, where the shear connectors ensured a reliable connection between the boundary CFST columns and the wall web. Although the high-strength concrete and high-strength reinforcements functioned well together, the reasonable material strength matching between concrete and steel bars and the stiffness matching between wall web and boundary elements should also be considered in design. The incorporated steel fibers alleviated damage to the wall web and enhanced the wall's flexural deformation capacity. The addition of bottom double-skin steel plates to both sides of the wall web effectively increased the lateral strength, deformability, and reparability of a composite wall made of non-fiber-reinforced concrete. An analytical model was developed to evaluate the load-bearing capacity and verified by comparing the model predictions against test results.

Seismic behavior of steel fiber-reinforced high-strength concrete mid-rise shear walls with high-strength steel rebar

To investigate the seismic behavior of shear walls with high-strength materials, cyclical quasi-static tests on five half-scale shear walls with an aspect ratio of 1.5 were carried out, including four conventional reinforced concrete walls and one composite wall. The steel fiber-reinforced concrete shear wall with HRB 600 MPa reinforcement located completely in the boundary element and in the wall web was taken as the reference specimen. The presence of steel fibers, the strength of wall web rebar, and the presence of high-strength reinforcement diagonal bracing (X configuration) were selected as major test parameters for the other three conventional walls. The results reveal that the high-strength concrete (HSC) shear wall with high-strength steel rebar (HSSR) showed stable hysteresis performance, and all specimens had acceptable crack widths and residual deformations before a lateral drift of 1%, except for the nonfiber-reinforced concrete specimen. The addition of steel fibers can reduce the crack width, limit the shear crack development, and increase the flexibility deformation, thus improving the deformation capacity of the specimens. Using HRB 600 MPa reinforcement instead of HRB 400 MPa reinforcement as wall web rebar can significantly reduce the residual deformation. The specimen with high-strength reinforcement diagonal bracing in the wall web and the composite shear wall with a built-in steel truss not only had desirable repairability after a large earthquake but also showed much higher energy consumption capacity under a strong earthquake. Finally, based on the experimental and theoretical analysis, a simple method for calculating the lateral strength was established, and the predicted results showed good agreement with the test data.

Elasto-plastic Analysis of High-strength Concrete Shear Wall with Boundary Columns Using Fiber Model

In this study, an experimental study and numerical calculations using fiber model were conducted for four high-strength concrete shear walls with boundary columns under low cyclic load. The boundary column and shear wall were divided into fiber elements, and PERFORM-3D finite element analysis software was used to carry out push-over analysis on the test specimens. The results show that the finite element analysis results were in good agreement with the experimental results. The proposed analysis method could perform elasto-plastic analysis on the high-strength concrete shear wall with boundary columns without distinguishing the categories of frame column and shear wall. The seismic performance of high-strength concrete shear wall with boundary columns was analyzed using the following parameters: axis compression ratio, height to width ratio, ratio of vertical reinforcement, and ratio of longitudinal reinforcement in the boundary column. The results show that the increase in the axial compression ratio causes the bearing capacity of the shear wall to increase at first and then to decrease and causes the ductility to decrease. The increase in the height to width ratio causes the bearing capacity of the shear wall to decrease and its ductility to increase. The ratio of vertical reinforcement was found to have little effect on the bearing capacity and ductility. The increase in the ratio of longitudinal reinforcement in boundary column resulted in a significant increase in the bearing capacity and caused the ductility to decrease at first and then to slowly increase.

Hysteretic behavior of high-strength concrete shear walls with high-strength steel bars: Experimental study and modelling

To study the cyclic behavior of high-strength concrete shear wall with high-strength steel bars, five shear wall specimens with a shear-to-span ratio of 2.2 were fabricated and tested subjected to constant axial load and horizontal cyclic load. The effects of the axial force ratio, the strength of distributing steel bars, the presence or absence of steel fibers, and the properties with or without wrapped steel plates on the hysteretic behavior of shear walls were analyzed. The results show that the combination of concrete with C80 grade and steel bars with HRB600 grade was a reasonable strength matching way. Increasing the strength of distributing steel bars in the wall delayed the development of cracks and reduced the residual deformation. The addition of steel fibers reduced the crack widths and improved the elastic-plastic deformation capacity. Moreover, adding wrapped steel plate at the bottom of wall effectively improved the bearing capacity, deformation capacity, and reparability of the shear wall. Finally, a restoring force model established on the basis of experiment and theoretical analysis agreed well with the test hysteresis curves.

EXPERIMENTAL STUDY ON SEISMIC BEHAVIOR AND SHEAR STRENGTH CALCULATION OF HIGH DUCTILE CONCRETE LOW-RISE SHEAR WALL

The usage of high ductile concrete (HDC) in low-rise shear walls was proposed to improve their seismic behavior. The effects of axial load ratio, the amount of horizontal reinforcement and steel plate on failure patterns, ductility and energy dissipation capacity of shear walls were studied by quasi-static tests of five shear walls with the shear span ratio of 1.0. The results showed that the deformability of the HDC low-rise shear walls is significantly improved compared with the high-strength concrete low-rise shear walls. The energy dissipation capacity and deformability of shear walls are improved with the increase of the axial load ratio and the decrease of the spacing of horizontal reinforcement. The collaborative work between HDC and steel plate improves the shear capacity and energy dissipation capacity of the low-rise shear walls. A formula for calculating the shear capacity of the HDC low-rise shear walls is proposed based on the softened strut-and-tie model, and the calculation values agree well with the test data.

Research on hysteretic behaviour of high-strength concrete shear wall plate for steel tube in building construction

For the problem of insufficient analysis of the hysteretic behaviour of the traditional concrete shear wall, the research method of hysteretic behaviour of high-strength concrete shear wall for steel tube in building construction is proposed in paper. Based on the OpenSee platform, the displacement of the base was recorded by the displacement metre installed on the base, and the load displacement curve is plotted, and the shear bearing capacity of the model was analysed. The failure modes, axial compression ratio and concrete strength parameters of the specimens were studied to obtain the following conclusions. Higher the axial compression ratio and the wall shaft pressure, the higher the load capacity of the specimen. By comparing the hysteretic behaviour of different steel tube high strength concrete shear strength specimens, this paper analyses the performance of steel tube high strength concrete shear wall panels, which provides data and reference for future construction.

Research on hysteretic behaviour of high-strength concrete shear wall plate for steel tube in building construction

For the problem of insufficient analysis of the hysteretic behaviour of the traditional concrete shear wall, the research method of hysteretic behaviour of high-strength concrete shear wall for steel tube in building construction is proposed in paper. Based on the OpenSee platform, the displacement of the base was recorded by the displacement metre installed on the base, and the load displacement curve is plotted, and the shear bearing capacity of the model was analysed. The failure modes, axial compression ratio and concrete strength parameters of the specimens were studied to obtain the following conclusions. Higher the axial compression ratio and the wall shaft pressure, the higher the load capacity of the specimen. By comparing the hysteretic behaviour of different steel tube high strength concrete shear strength specimens, this paper analyses the performance of steel tube high strength concrete shear wall panels, which provides data and reference for future construction.

Mechanical behavior of a steel tube-confined high-strength concrete shear wall under combined tensile and shear loading

The steel tube-reinforced concrete (STRC) shear wall is a type of composite shear wall that consists of a reinforced concrete shear wall embedded into high-strength concrete-filled steel tube (CFST) columns in the boundary element and/or the center of a shear wall. The use of STRC walls has gained popularity in the construction of high-rise buildings because their performance is superior to conventional reinforced concrete (RC) walls. To study the influence of various parameters (i.e., the number of CFSTs embedded in the shear wall, the shear span ratio, the ratio of the vertical reinforcement, the strength of the concrete outside the embedded steel tube, and the initial tensile stress) on the mechanical properties of an STRC composite shear wall under combined tension and shear forces, tensile shear tests were conducted on 9 specimens whose shear span ratios were less than or equal to 1.0. The experimental results demonstrated that the STRC shear wall retained its high shear capacity and its good ductility under a high axial tensile force. Using statistical analyses, a formula to calculate the bearing capacity of an STRC shear wall was proposed. The calculated values are in good agreement with the experimental results.

Experimental study on seismic performance of steel fiber reinforced high strength concrete composite shear walls with different steel fiber volume fractions

The concrete at the bottom corner of the reinforced concrete shear walls is easily crushed to failure under vertical and horizontal loads owing to its low tensile strength. Casting steel fiber reinforced high strength concrete (SFRHSC) in the plastic critical zone at the bottom of the shear walls is expected to improve the seismic performance of these walls for steel fibers can raise the toughness of high strength concrete (HSC). Based on the previously determined mechanical properties of SFRHSC, a type of SFRHSC composite shear wall was developed in this work. SFRHSC and HSC were cast in the lower and upper halves, respectively, and a steel profile was placed in each boundary member of the walls. Nevertheless, the influence of the steel fiber facture volume on seismic performance of the SFRHSC composite shear walls remains unclear. This paper aims to investigate the effect of the steel fiber volume fraction on the non-linear behavior of a SFRHSC composite shear wall. Four SFRHSC composite shear walls with 1/2 scale and shear span ratio of 2.25 were subjected to low cyclical quasi-static testing. Each specimen was tested under cyclically increasing lateral loads and a constant relatively high vertical load until failure. The impact of steel fiber on the seismic performance of composite elements with fiber volume fraction of 0%, 1.0%, 1.5% and 2.0% was evaluated. The results revealed the coordinated working performance of the SFRHSC composite shear wall. The deformation capacity of the SFRHSC composite specimen was higher than that of the HSC composite shear wall and the flexural deformation improved gradually, as the steel fiber prevented cracking of the cement matrix. Crack and damage process were postponed, and damage degree was reduced with increasing steel fiber volume fraction. Furthermore, the energy dissipation ability improved significantly, when a fiber volume fraction of 2.0% was employed.

Seismic behavior of cold-formed steel high-strength foamed concrete shear walls with straw boards

To satisfy the requirements of thermal insulation property and load-bearing capacity of cold-formed steel (CFS) shear walls in mid-high buildings, a new type of CFS shear wall referred to as cold-formed steel high-strength foamed concrete (CSHFC) shear wall with straw boards on both sides is proposed in this study. Straw board is an one-way slab consisting of horizontally distributed natural straw fibers and has excellent thermal property. High-strength foamed concrete (HFC) is a new type of lightweight foamed concrete with high compressive strength. Seven full-scale specimens with different configurations were conducted under reversed cyclic loading to assess the failure mode, load-bearing capacity, ductility, lateral stiffness and energy dissipation. The test parameters include HFC strength grade, aspect ratio, stud section type and opening of the specimens. Compressive bearing capacity of the HFC and restrictive effect of the HFC on the studs and screw connections significantly improved the wall's shear strength and lateral stiffness. Together with bond-slip behavior between the HFC and the studs, HFC cracking and straw boards cracking, these makes the walls exhibit better ductility and energy absorption. The failure mode typically includes local buckling of the studs, inclined cracking of the HFC and straw boards and relative slippage between the stud webs and the HFC. Enhancing HFC strength grade and increasing studs' section area could effectively improve the seismic behavior, whereas increasing walls' length could improve shear capacity and lateral stiffness. Comparison of the results between CSHFC shear walls and traditional CFS shear walls shown that the seismic performance of the CSHFC shear walls was much higher than those of traditional CFS shear walls.

Seismic tests of RC shear walls confined with high-strength rectangular spiral reinforcement

In order to improve the deformation capacity of the high-strength concrete shear wall, five high-strength concrete shear wall specimens confined with high-strength rectangular spiral reinforcement (HRSR) possessing different parameters, were designed in this paper. One specimen was only adopted high-strength rectangular spiral hoops in embedded columns, the rest of the four specimens were used high-strength rectangular spiral hoops in embedded columns, and high-strength spiral horizontal distribution reinforcement were used in the wall body. Pseudo-static test were carried out on high-strength concrete shear wall specimens confined with HRSR, to study the influence of the factors of longitudinal reinforcement ratio, hoop reinforcement form and the spiral stirrups outer the wall on the failure modes, failure mechanism, ductility, hysteresis characteristics, stiffness degradation and energy dissipation capacity of the shear wall. Results showed that using HRSR as hoops and transverse reinforcements could restrain concrete, slow load carrying capacity degeneration, improve the load carrying capacity and ductility of shear walls; under the vertical force, seismic performance of the RC shear wall with high axial compression ratio can be significantly improved through plastic hinge area or the whole body of the shear wall equipped with outer HRSR.