Research On Seismic Behavior And Calculation Method Of Deformation Capacity Of Reinforced Concrete Shear Walls With Flange

In high-rise building design,in order to minimize the effect on the floor plan,linear rectangular walls are often combined to form T-,L-and I-shaped shear walls with flange.Such configurations lead to complicated interactions between the wall segments(flange and web),so that it is no longer reasonable to assume that linear segments of the walls resist lateral loads in each direction independently,thus the overall mechanical behavior of flanged walls is significantly different from the ordinary rectangular walls.However,the study on shear wall with flange is still lagging behind the engineering practice at home and abroad,especially for T-shaped and L-shaped walls with asymmetric cross section.Therefore,through the methods of experimental study,numerical simulation and theoretical analysis,the seismic behavior of reinforced concrete(RC)shear walls with flange under uniaxial and biaxial cyclic loadings and the sectional curvature as well as the deformation characteristics of shear walls with flange under different loading directions will be investigated respectively in this paper.Furthermore,a new load-deformation analysis model for shear walls with flange is established,based on the model,a simplified calculation method of ultimate displacement is proposed.Specific contents are as follows:Through quasi-static tests of five RC shear walls with flange under cyclic loading,the failure mode of RC shear walls with flange under uniaxial and biaxial loads was studied by using a new loading procedure with unequal amplitude,the seismic behavior under different loading directions(flange in tension and flange in compression)was analyzed as well.The results indicate that the damage to the shear walls with flange is mainly concentrated in the boundary element of the free end of web,while the flange remains intact,so that the boundary element at the web-flange junction is suggested to remove.The strength and stiffness are higher when the flange is in tension,whereas the ductility and energy dissipation capacity are better and the stiffness degradation is slower when the flange is in compression.The influence of biaxial load on the bearing capacity and deformation capacity in the web direction is minor.Enhancing the boundary restraints of the web boundary can effectively improve the seismic behavior of the shear walls,The hysteretic behavior of RC shear walls with flange was simulated by using the stiffness based fiber beam column elements in Open Sees.Based on the verified model,the effects of axial compression ratio,shear span ratio,flange width/web height ratio,concrete strength,longitudinal reinforcement ratio,stirrup reinforcement ratio of boundary element at the free end of web and distributed vertical reinforcement ratio on the bearing capacity,ductility and energy dissipation capacity of RC shear wall with flange were studied,The variation regularity of seismic behavior with various parameters of RC shear walls with flange was obtained systemically.Based on the moment-curvature analysis of RC shear walls with asymmetric cross section,the yield curvature and ultimate curvature values under different parameters were calculated for flange in tension and flange in compression respectively,meanwhile,the variation regularity of sectional curvature with different parameters was described in detail according to the variation of depth of compressive zone.According to the results of numerical analysis,the empirical formulas of yield curvature and ultimate curvature were fitted,and then the formulas for calculating the ductility of section curvature were obtained.According to the relationship between curvature ductility and displacement ductility,the calculation method of displacement ductility was established.The rationality of the method was verified by comparing with the experimental data.The deformation in the plastic hinge region of RC shear walls with flange was measured for whole loading process by Particle Image Velocimetry(PIV),such technique was applied to the test of shear wall components for the first time.Based on this,top flexural displacement,top shear displacement and the sliding displacement between the wall and the foundation were calculated to analyze the proportion of each deformation component and its variation along loading process.The results indicate that the ratio of shear to total displacement remains approximately constant over the entire inelastic range for the shear walls whose behavior is dominated by flexural.The ratio of shear to total displacement can reach about 15%,whereas the sliding displacement constitutes within 3% of the total displacement.Therefore,the contribution of shear displacement should be included in the calculation of deformation capacity,while the contribution of sliding displacement should be neglected.According to the results of deformation analysis of RC shear walls with flange,the calculation methods of the flexural deformation of the wall panel and the deformation caused by the fixed-end rotation of the wall associated with the slip of longitudinal bars were established respectively based on the moment-curvature analysis.According to the linear relationship between shear strain and curvature,the calculation method of shear deformation was established as well.Based on this,a new load-deformation analysis model which includes the contribution of flexural,shear and slip of longitudinal reinforcement was proposed,which can yield the load-displacement curves of RC shear walls with flange.Based on the model,a simplified calculation method of ultimate displacement of RC shear wall with flange was proposed further.The calculated results are in good agreement with the experimental results,which can provide reference for the displacement-based deformation capacity design.