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This paper presents large‐scale quasi‐static tests conducted to investigate the seismic behavior of slender T‐shaped walls under a high axial compression force ratio of approximately 0.19. Four specimens were designed per various codes and design methods for comparison. All specimens failed in a flexural mode, characterized by the crushing of concrete and buckling or fracture of boundary longitudinal rebars at the web toe. The specimens designed per the US code ACI 318‐19 provisions and designed using displacement‐based method exhibited satisfactory deformation capacity with an ultimate drift exceeding 2.0%, which validates the effectiveness of the provisions and displacement‐based method for T‐shaped walls under high axial force ratios. However, the specimen designed per the Chinese code GB 50011‐2010 experienced a sudden drop in strength after 1.0% drift in flange‐in‐tension loading, indicating insufficient design of the special boundary element at the web toe and the necessity of improvement of the current Chinese code provisions. The flexural strength of the T‐shaped wall specimens can be accurately estimated using cross‐sectional analysis. Analysis of the test data indicated that the effective stiffness of the T‐shaped RC walls with an axial force ratio of no greater than 0.1 was significantly lower than 0.35EcIg, while that of the T‐shaped walls with an axial force ratio of 0.19 reached 0.5–0.7EcIg. Existing equations did not provide accurate estimate of the effective stiffness of T‐shaped walls. The lateral drift limit formulation developed by Segura and Wallace could reasonably estimate the lateral drift capacities for the T‐shaped RC wall specimens under high axial force ratios. Finally, three conceptually different models, namely the MVLEM‐3D, SFI‐MVLEM‐3D, and multi‐layer shear element models were adopted for the simulation of T‐shaped RC walls. All three models reasonably predicted the flexural strength capacity (mostly less than 15% error) and the effective stiffness (13%–43% error) of the T‐shaped walls. [ABSTRACT FROM AUTHOR]

Steel-plate composite walls comprise a steel plate encased in the middle of a reinforced concrete shear wall [referred to as "composite plate shear walls-concrete encased (C-PSW/CE)"], or a concrete infill sandwiched between two steel faceplates [referred to as "double-skin composite (DSC) walls"]. In this study, two I-shaped C-PSW/CE specimens with a shear-to-span-ratio of 1.2 were experimentally tested to investigate the cyclic in-plane shear behavior of C-PSW/CE used for high-rise buildings. Both wall specimens were identical in geometric dimensions and reinforcement details, with the exception of axial force ratio. The results indicated that shear failure occurred in the two wall specimens due to serious spalling of web concrete, followed by buckling of the embedded steel plate and vertically distributed reinforcements. The increase in axial force ratio from 0.16 to 0.29 resulted in an 11.8% rise in peak strength and a decrease in ultimate shear strain of 27% for C-PSW/CE. A comparison between C-PSW/CE and DSC walls indicated that the latter had a similar peak strength to the former, but clearly improved the ultimate drift. This is because the double faceplates of DSC walls provided a more effective restraint to the infilled concrete and prevented spalling of concrete. Then, this paper developed a refined numerical model to simulate C-PSW/CE and compared the analytical results with the experimental data. Finally, shear strength design formulas specified in Chinese and US codes were verified against a large volume of test data and numerical simulation results. The shear strength of C-PSW/CE was reasonably estimated by the JGJ 3-2010 design formulas (Chinese code), while significantly underestimated by the AISC 341-16 formula (US code) which neglects the shear contribution of reinforced concrete encasement. [ABSTRACT FROM AUTHOR]

In high-rise buildings, reinforced concrete (RC) shear walls, particularly those forming part of coupled wall systems or core wall systems, may be subjected to coupled axial tension and cyclic lateral loads during strong seismic events. A new two-dimensional material model named the "Fixed Angle Model Considering Crack Sliding" (FAM-CS) was proposed for simulating the nonlinear behavior of RC walls subjected to axial tension and cyclic lateral loads. The proposed model was implemented in the OpenSees platform. Nonlinear constitutive models for shear aggregate interlock effects of concrete and dowel action of rebars were incorporated into the proposed model to represent the shear transfer mechanisms along concrete cracks. The proposed model was validated against the test data of six wall specimens subjected to coupled axial tension and cyclic lateral loads. The results indicated that the proposed model reasonably predicted the lateral strength capacity (an average error of 6.2 %) and the residual strength at the maximum drift loading (an average error of 12.3 %) of the specimens. For comparison, three other commonly used models, the Shear-Flexure Interaction Multiple-Vertical-Line-Element-Model, the multi-layer shell element model and the Cyclic Softened Membrane Model were adopted for the simulation of the specimens. Compared with the three existing OpenSees models, the newly implemented material model provided improved predictions of the wall hysteretic behavior with respect to lateral strength capacity, lateral strength degradation, pinching characteristics and cyclic stiffness degradation. In addition, the proposed model reasonably captured the localized failure pattern as well as the energy dissipation characteristics of the test specimens. Finally, a mesh sensitivity study was conducted to assess the robustness of the proposed model. The results revealed that the proposed model was robust regarding the lateral load-drift responses of RC walls, with a mesh size ranging from approximately one to three times the average crack spacing. • A model was proposed for simulating the behavior of RC walls under axial tension-flexure-shear loads. • The aggregate interlock model and dowel action model were extended for both opening and closed cracks. • The proposed model was validated against test data of six RC wall specimens. • The range of mesh sizes for the model was recommended. • Three other models in OpenSees were compared with the proposed model. [ABSTRACT FROM AUTHOR]

Reinforced concrete shear walls may exhibit various failure modes when subjected to combined axial tension-flexure-shear loads. This study developed a theoretical method for predicting the failure mode of RC walls subjected to combined axial tension and cyclic lateral loads, in which the force-displacement response curve was compared to the predicted flexural, shear and sliding strength capacity curves. The formulas for calculating the axial elongation and horizontal crack widths of tensile RC walls were proposed, and the influence of these two aspects was fully considered in the estimation of shear strength and sliding strength degradation. The proposed method was validated against test data of ten RC wall specimens which underwent various failure modes, including flexural, shear, sliding, flexural-sliding, and shear-sliding failure modes. Comparisons between experimental and theoretical results indicated that the proposed method predicted the failure modes and lateral strength with acceptable accuracy. As the proposed method accurately estimated the shear and sliding strength degradation, it provided the insights on the shifting of dominated behaviors (e.g., flexural- or shear-dominated behavior to sliding-dominated behavior). Finally, strength design formulas specified in Chinese, US and European codes were verified against test data. The flexural strength of RC walls was reasonably estimated by the JGJ 3–2010 (Chinese code), ACI 318–19 (US code) and Eurocode 8 (European code) design formulas. Among the three codes, JGJ 3–2010 provided a more reasonable estimate on shear strength of tensile RC walls than the other two codes. • A method was proposed for predicting failure modes of RC walls under tension-flexure-shear loads. • An approach was developed to calculate axial elongation and horizontal crack widths of RC tensile walls. • Axial elongation and crack widths were considered in estimation of lateral strength degradation. • The failure mode prediction method was validated against test data of ten RC wall specimens. [ABSTRACT FROM AUTHOR]

Highlights • Coupled axial tension-flexure tests were conducted on RC slender walls. • Axial tensile force levels influence failure modes of RC slender walls. • Axial tensile forces decrease effective flexural stiffness and strength of walls. • Design equations of flexure strength and stiffness of tensile RC walls are estimated. • The proposed refined model accurately estimates axial elongation of RC walls. Abstract Reinforced concrete (RC) walls in high-rise buildings, in particular wall piers that form part of a coupled or core wall system, may experience coupled axial tension-flexure loading when subjected to lateral demands. The seismic behavior of RC walls with various axial tensile forces was investigated by quasi-static tests on four RC slender walls subjected to the combined tension and flexure loading. The failure modes, strength and deformation capacity, effective flexural stiffness, and design equations are presented. The failure modes included flexural-sliding failure and flexural failure. The effective flexural stiffness and lateral strength of the walls significantly decreased as the axial tensile forces were increased. The ACI 318-14 and ASCE/SEI 41-13 code provisions overestimated the effective flexural stiffness of RC walls subjected to axial tension. Although equations proposed by Paulay & Priestley and Adebar et al. consider the influence of axial forces, they were not able to accurately predict the effective flexural stiffness of the RC wall specimens subjected to tensile forces. Both sectional analysis using XTRACT and JGJ 3-2010 (China) code equations provided accurate estimation of the flexural yield strength of walls. Finally, both a refined model and simplified equation were proposed to estimate the axial elongation for RC slender walls subjected to axial tensile force and cyclic lateral loading. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

• PC walls are used to enhance seismic performance of tensile walls of tall buildings. • Tests were conducted on PC walls under coupled axial forces and cyclic shear loading. • Variable axial tension–compression forces decreased shear strength of PC walls. • Design formulas of shear strength of PC walls are estimated. • The truss idealization method for calculating shear stiffness of PC walls is validated. To prevent adverse impact of axial tensile force on seismic performance of reinforced concrete (RC) walls, bonded prestressed concrete (PC) walls are proposed to use in high-rise buildings. These prestressed strands provide an initial axial compressive load on the walls to balance axial tensile forces induced by strong ground motions. Three low-aspect-ratio PC wall specimens were tested for various loading patterns, including constant axial forces or variable axial forces, combined with cyclic shear loading. The failure modes of wall specimens varied with loading patterns. The variation in axial forces decreased the normalized tensile-shear strength and compressive-shear strength by 20.0% and 11.2%, respectively. The wall specimen undergoing diagonal compression failure had a small ultimate drift ratio of 0.6%, while other two specimens had an ultimate drift ratio no less than 1.2%. The PC wall under axial tensile forces had significantly higher lateral strength and stiffness than a RC wall counterpart, because the prestressed force controlled the development of cracks and prevented the sliding failure. Both the JGJ 3–2010 (China) code formula and ACI 318–19 (U.S.) code formula significantly underestimate the shear strength of PC wall specimens. The ASCE/SEI 43–05 (U.S.) code formula appears to reasonably reflect the resisting mechanisms of PC walls and provides an accurate estimate to the shear strength of wall specimens. The truss idealization method provides a reasonable estimate for the cracked shear stiffness of PC walls under coupled axial tension-shear loading, while underestimates the cracked shear stiffness of PC walls under coupled axial compression-shear loading. [ABSTRACT FROM AUTHOR]

The steel reinforced concrete (SRC) wall consists of structural steel embedded at the boundary elements of a reinforced concrete (RC) wall. The use of SRC walls has gained popularity in the construction of high-rise buildings because of their superior performance over conventional RC walls. This paper presents a series of quasi-static tests used to examine the behavior of SRC walls subjected to high axial force and lateral cyclic loading. The SRC wall specimens showed increased flexural strength and deformation capacity relative to their RC wall counterpart. The flexural strength of SRC walls was found to increase with increasing area ratio of embedded structural steel, while the section type of embedded steel did not affect the wall's strength. The SRC walls under high axial force ratio had an ultimate lateral drift ratio of approximately 1.4%. In addition, a multi-layer shell element model was developed for the SRC walls and was implemented in the OpenSees program. The numerical model was validated through comparison with the test data. The model was able to predict the lateral stiffness, strength and deformation capacities of SRC walls with a reasonable level of accuracy. Finally, a number of issues for the design of SRC walls are discussed, along with a collection and analysis of the test data, including (1) evaluation of flexural strength, (2) calculation of effective flexural stiffness, and (3) inelastic deformation capacity of SRC walls. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

This paper proposed an innovative composite wall, named the steel tube-double plate-concrete composite shear wall, which is suited for use in the lower stories of super high-rise buildings. The seismic behavior of the composite walls was examined through results of an experimental research program where five rectangle-shaped wall specimens with a shear span ratio of 2.5 were tested. The test results indicate that the specimens fail in a flexural mode, characterized by local buckling of boundary steel tubes and steel plates, fracture of steel tubes, and compressive crushing of concrete at the wall base. The extent of concrete filled steel tubular (CFST) boundary elements significantly affects the deformation and energy dissipation capacities of the composite walls. The area ratio of steel plate has a minimal effect on the deformation capacity of the wall specimens. The addition of circular steel tubes embedded in the CFST boundary elements leads to an increase in the lateral load-carrying capacity of the composite walls, but it does not increase the wall's deformation capacity. When the CFST boundary element's extent is 0. 2 times the wall's sectional depth and the designed axial force ratio is 0.45, the wall specimen has a yield drift ratio of over 0. 005 rad and an ultimate drift ratio of 0. 030 rad. In addition, simplified formulas used to calculate the flexure strength of the composite walls were proposed. The evaluated results show good agreement with the test results, with errors no more than 10%. [ABSTRACT FROM AUTHOR]

Reinforced concrete (RC) shear walls are the major lateral load-carrying structural components in high-rise buildings. Under strong earthquake motions, the axial loads of RC walls are not constant axial compression, but may be in tension, resulting in the axial load of RC walls varying from compression to tension. In this study, three RC slender wall specimens (shear-to-span ratio λ = 2.0) were tested to study the effect of the fluctuating range and loading patterns of variable axial forces on their cyclic behavior, including failure modes, hysteretic response, strength and deformation capacity. Test results indicated that the final failure of RC slender walls subjected to variable axial forces was controlled by flexural failure in the compressive-flexural direction. The hysteretic curves of RC slender walls were asymmetric and substantively different from the hysteretic curves of RC slender walls with constant axial loads. The fluctuating range of axial forces had a limited influence on the shape of hysteretic curves, while the loading patterns significantly changed the shape of these hysteretic curves. Under the variable axial forces, the lateral strength and deformation capacity of RC slender walls depended on the fluctuating range of axial forces, while loading patterns had limited influence when the fluctuating range of axial forces kept constant. The loading patterns had a limited influence on the lateral stiffness of RC slender walls, while the increase of fluctuating range of axial forces increased the difference between compressive-flexural and tensile-flexural lateral stiffness. No matter in tensile-flexural or compressive-flexural directions, the assumption that the wall section remains plane after deformation is suitable for RC slender walls under the variable axial forces, and enables reasonable estimations of yielding and peak strength. Finally, a finite element model was developed for predicting the cyclic behavior of RC walls under the variable axial loads. • Experimental tests are conducted on RC walls subjected to variable axial loads. • Variable axial loads change the shape of hysteretic curves of RC walls. • Remaining plane of wall section is suitable for RC walls with variable axial loads. • A FEM model is developed for RC walls under variable axial loads. [ABSTRACT FROM AUTHOR]

Abstract: This paper proposes an innovative composite shear wall, named the steel tube-reinforced concrete (ST-RC) composite wall, with steel tubes embedded at the wall boundary elements and fully anchored within the foundation. This arrangement is supposed to enhance the wall’s seismic performance. A series of quasi-static tests were performed to examine the behavior of the ST-RC walls when subjected to high axial forces and lateral cyclic loads. The area ratios of steel tube and of concrete filled steel tube (CFST) (i.e. the ratios of the cross-sectional areas of steel tubes and of CFSTs over that of the wall boundary element, respectively), axial force ratio, and cross-sectional shape of walls were taken as major test variables. All specimens failed in a flexural mode, characterized by tensile yield of the vertical rebars and steel tubes in the boundary elements and compressive crushing of concrete at the wall bottom. The test results showed that the ST-RC composite walls had larger load-carrying and deformation capacities relative to the RC wall counterpart. The deformation capacity of the rectangular-shaped composite walls increased with an increase in the area ratios of steel tube and of CFST and decreased with an increase in the applied axial force ratio. The barbell-shaped composite wall that was configured with edge columns had much larger deformation and energy dissipation capacities than the rectangular-shaped composite walls. In addition, simplified formulation was proposed to evaluate the lateral load-carrying capacity of the ST-RC composite walls. The evaluated results showed good agreement with the test results, with errors no more than 10%. [Copyright &y& Elsevier]