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A novel biaxial finite-element (FE) model is proposed and validated by a total of 32 reinforced concrete (RC) shear walls with aspect ratio below 1.5. First, a biaxial concrete model package, which was previously developed in ABAQUS software for RC panel tests, is adopted to evaluate its accuracy of simulating RC shear walls. The FE modeling scheme, the biaxial FE model of concrete before and after initial cracking, and the uniaxial FE model of concrete are illustrated. The developed model considers the following five significant features including the concrete compressive softening, tension softening, concrete shear softening, pinching effect, and strength reduction because of lateral cracking. Second, the traditional rebar model without buckling and the longitudinal rebar model considering buckling are also illustrated. Third, the discrete Fréchet distance is adopted to quantify the relative error between FE simulation results and test results. Subsequently, the constitutive model in ABAQUS simulates a total of 32 RC shear walls under axial and lateral forces. The simulated RC shear walls cover a wide range of parameters, including aspect ratio, rebar orientation, reinforcement, and section shape. The FE simulation results are compared with test results including the force versus lateral deformation curves, load-shear displacement curves, and failure modes. According to the comparison, the developed constitutive model shows high accuracy for RC shear walls with aspect ratio below 1.5, including the replication of pinching effect and residual capacity. The developed model overestimated the initial stiffness of some test specimens, which may be attributed to the omission of concrete cracking induced by shrinkage. In general, the overall accuracy of the developed constitutive model is validated. [ABSTRACT FROM AUTHOR]

Four shear-critical RC shear walls were tested under a tension-bending-shear load to replicate seismic behavior of the bottom shear wall in high-rise buildings. The axial tension ratio ranged from 0 to 0.5 and the aspect ratio was 1.06. The shear compression failure mode was observed for each specimen, characterized by the formation of an inclined crack at 45° and direct strut action. The shear displacement was a dominant deformation component throughout the loading history. When the axial tension force increased from 0 to 1,293 kN, the ultimate drift ratio increased from 0.90% to 2.38%, while shear capacity linearly decreased from 1,507 to 895 kN. The load–displacement curve showed a significant pinching effect and strength degradation effect. In addition, this paper reports an innovative experimental method to obtain shear resistance of transverse reinforcement (Vs) based on the plasticity theory and strain measuring result. Test results using this method show that not all horizontal distributed rebar yield simultaneously at the ultimate capacity. The US code-specified shear strength contribution of horizontal distributed rebar was found to be unsafe for each test specimen. Finally, a database of RC shear walls subject to combined tension-bending-shear load was established to evaluate shear strength formulas in design codes. The comparison showed the Chinese code predicted spuriously higher tension-shear capacity, while the US code predicted conservative capacity. Based on the developed database, a simplified design formula is proposed with adequate safety concerns and accuracy. [ABSTRACT FROM AUTHOR]

• Six innovative shear critical composite shear walls without tie bars were tested. • The shear compression failure for each specimen was observed with notable capacity and ductility. • The influence of axial compression ratio and faceplate slenderness ratio was elaborately investigated. • A novel database of 38 composite shear walls was established for shear capacity evaluation. Many skyscrapers have used the Reinforced Concrete (RC) filled Composite Plate Shear Walls (CPSW). Based on in-plane shear tests on six shear-critical CPSW specimens and a RC shear wall specimen, the behavior of CPSW systems with stud or tie bar connectors, various connector spacings, and various axial compression ratios were reported. In the test program, the Concrete Filled Steel Tubes (CFSTs) are applied for each specimen as boundary elements to simulate the engineering design of CPSW in skyscrapers. This paper presents the test observations, the ultimate capacity, the lateral stiffness, the ductility and the energy dissipation results. Based on the test results, the CPSW specimens with CFST boundary element failed in shear compression failure and the reference RC shear wall failed in shear tension failure. The weld fracture was generally found at boundary element (CFST) in the descending branch. Compared to the RC shear wall, the shear capacity of the CPSW systems were enhanced by 104–129%. The difference between CPSW systems with stud connectors and those with tie bars was insignificant in terms of ultimate capacity. Subsequently, a new database including 38 test specimens was established from the aforementioned test program and available literatures. The database results indicate the compressive capacity of infilled concrete is the dominating factor influencing the shear capacity, instead of the yield capacity of steel. In addition, a design formula for the in-plane ultimate capacity of shear-critical CPSW systems is proposed. Comparisons demonstrated that the proposed model was consistent and exhibited a reasonable level of consistency. [ABSTRACT FROM AUTHOR]

• Four innovative flexural critical composite shear walls without tie bars were proposed and tested. • The failure mode, load-displacement relationship and stiffness degradation behavior were investigated. • The proposed systems connected by shear studs exhibited adequate strength and displacement capacity. • The shear force contribution of steel plate was obtained and overstrength ratio was proposed. The reinforced concrete filled composite plate shear walls (CPSW) system employs two steel plates with infilled reinforced concrete. Based on an experimental study of four flexural critical CPSW specimens under high axial compression ratio ranging from 0.313 to 0.542 and reciprocal lateral load, the seismic performance of shear studs connected CPSW systems with orthogonal reinforcement in wall web and longitudinal reinforcement in boundary element is examined. The failure mode, load-displacement relationship, flexural strength, displacement capacity, stiffness degradation and equivalent damping ratio are reported in detail. The compression yielding of boundary element was observed before its local buckling, and yielding of faceplate was observed before faceplate local buckling. The fracture failure of the boundary element and crushing of infilled concrete were observed at the descending branch. The test results showed that the CPSW systems connected by shear studs had adequate ductility, and the ultimate drift ratio ranged from 1.17% to 1.78%. The overstrength ratio of the moment capacity ranged from 1.06 to 1.18 in the test. Based on the plasticity theory, the strain measurement results of steel faceplates were used to calculate the shear force contribution of the steel plate. The influence of axial compression ratio on the internal force transfer and ultimate capacity is investigated. In addition, a database of 47 flexural critical CPSW specimens with boundary element was established, and the overstrength ratio for the anchorage design was proposed with adequate safety. [ABSTRACT FROM AUTHOR]

A new set of constitutive models named TsingHua University Concrete 2D (THUC2) is developed for use in ABAQUS. THUC2 has reduced mesh sensitivity and is based on the decoupling assumption and the fixed-angle crack assumption in order to consider the pinching effect, confinement, strength degradation, and shear softening of concrete. In the developed biaxial reinforced concrete models, the uniaxial model is first established, and the biaxial model is subsequently assembled from the uniaxial model. First, the proposed uniaxial constitutive model of concrete is reported. The mesh sensitivity of the model is reduced by adjusting the descending branch of the concrete model based on mesh size. Second, a total of five biaxial constitutive models of concrete are reported to cover a wide range of simulation requirements in engineering design. Third, the numerical implementation of the proposed concrete model in both ABAQUS implicit and explicit solvers is discussed. Subsequently, the modified two-way fixed angle crack model is validated by monotonic and hysteretic panel tests. The FE model exhibits little mesh sensitivity when the element number increased from 4 to 400. The developed model accurately predicts the pinching effect and the softening effect of the panels. Finally, previous tests on two nuclear containment vessels under lateral loads are simulated, and the modified two-way fixed angle crack model demonstrates adequate accuracy in terms of predicting the initial stiffness, ultimate capacity, and pinching effect. The proposed subroutine package for simulating RC members includes the dominant mechanical behaviors of concrete and can be adopted for high-efficiency simulation of RC shear wall structures. [ABSTRACT FROM AUTHOR]