Study On Tension-shear And Tension-flexure Behavior Of Reinforced Concrete Walls

Shear walls are the major lateral load-carrying structural components in high-rise buildings.Under strong ground motions,shear walls may be subjected to tensile force.In order to ensure the seismic performance of high-rise buildings,control of the tensile force level for shear walls has become one of the key points in the peer-review of structural design of super-tall buildings.This thesis investigates the tension-shear and tension-flexure behavior of reinforced concrete(RC)walls and the design methods.The main innovative works and achievements are as follows:(1)A series of quasi-static tests were conducted,where seven RC wall specimens with low aspect ratios(?=1.1)were subjected to axial tensile force and cyclic shear loading.The influence of axial tensile force and boundary longitudinal reinforcement ratio on seismic performance of low-aspect-ratio walls were investigated.The test results indicate that the failure modes of these specimens vary with different axial tensile forces and boundary longitudinal reinforcement ratios,including shear failure,shear-sliding failure,sliding failure and flexural failure.Increase of axial tensile force leads to significant decrease of lateral strength,lateral stiffness and energy dissipation capacity.(2)Refined numerical model was established to simulate the tensile-shear behavior of RC shear walls.The variables in the simulation included axial tensile force,horizontally and vertically distributed reinforcement,and boundary longitudinal reinforcement.The effect of those variable on the strength capacity,failure mode and mechanism were studied.Both analytical model and design equation were proposed to estimate the tensile-shear strength for the RC shear walls.Comparison with the test results and numerical results indicates that the design formulas in JGJ 3-2010(China code),ACI318-14(U.S.code),proposed by Ren et al.and the equation proposed in this thesis provide conservative estimates of tensile-shear strength for RC shear wall The mean values of the experimental-to-calculated strength ratio V^Test/V^Calc are 1.47,1.66,1.54 and1.34,respectively.The standard deviations of V^Test/V^Calc are 0.39,0.65,0.55 and 0.26,respectively.Compared with other design formulas,the equation proposed in this thesis reasonably reflects the influence of vertical reinforcement and axial tensile force,and it has a smaller standard deviation.Finally,experimental and numerical analysis indicate that the RC squat wall is prone to sliding failure if the normalized reinforcement tensile stress n_s exceeds 0.5.(3)Quasi-static tests were conducted on four wall specimens with high aspect ratios(?=2.0),which were subjected to axial tensile force and lateral cyclic loading.The influence of tensile force on tensile-flexural performance of RC shear wall was investigated.The test results indicate that the failure modes of these specimens vary with different axial tensile forces,including flexural failure and flexural-sliding failure.Increase of axial tensile force leads to significant decrease of lateral strength,lateral stiffness and energy dissipation capacity.Comparison with the test results indicates that the design formulas of tensile-flexural strength specified in GB 50010-2010(China code)and ACI 318-14(U.S.code)can provide accurate estimation of the tensile-flexural yield strength of RC shear wall.(4)The applicability of the strut-and-tie model for calculating the tensile-shear stiffness of RC shear walls was studied.A tensile-shear stiffness degradation equation of RC shear walls was proposed.Based on the sectional analysis,the simplified moment-curvature curves of RC walls under the tension-flexure were proposed.Based on the simplified moment-curvature curves,both a refined model and simplified equation are proposed to calculate the effective flexural stiffness for RC slender walls subjected to axial tensile forces and cyclic lateral loading.(5)Using various tension-stiffening models of cracked concrete,the axial tensile behavior of RC shear wall was studied.The mechanism of axial elongation for RC slender wall under the tension-flexure was revealed.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.