Seismic Behavior Of Unbonded Post-tensioned Self-centering Concrete Shear Wall With Concealed Steel Plate Brace

Traditional reinforced concrete shear walls are widely used in high-rise buildings due to their advantages such as large lateral stiffness and high horizontal bearing capacity.Reinforced concrete shear wall structures are often severely damaged under intense earthquake,which seriously affects the function of the building.After the earthquake,the residual deformation of the structure is too large to repair.Most of them even need to be demolished,causing huge economic losses and waste of resources.In recent years self-centering concrete shear wall was proposed by researchers home and abroad,which can reduce damage and residual deformation after an earthquake.However,because of its shortcomings such as low horizontal bearing capacity,poor energy dissipation performance,and lacking of multiple seismic lines,it has limited the development and application in engineering project.Therefore,it is necessary to develop a self-centering reinforced concrete shear wall system with multiple seismic lines,good bearing capacity and lateral stiffness that are equivalent to traditional reinforced concrete shear walls and having good energy performance and self-centering ability.A new kind of unbonded post-tensioned self-centering concrete shear wall system with concealed steel plate brace is proposed in this article.This new shear wall system consists of reinforced concrete end columns,unbonded post-tensioned concrete shear wall with horizontal bottom slits,hollow reinforced concrete wall and concealing steel plate brace.Model test and numerical simulation were conducted to study the seismic behavior of this new type of wall systematically.The main research contents and results are as flows:(1)One wall specimen of unbonded post-tensioned self-centering concrete shear wall system with concealed steel plate brace was designed and tested under quasi-static cyclic load.Meanwhile,failure pattern,the lateral load carrying capacity,hysteretic curves,stiffness degradation,energy dissipation and residual deformation were presented.The damage of the specimen was concentrated on the reinforced concrete end columns.There was little damage to the middle shear wall pales.The horizontal bottom slits were observed continuously opening and closing during the test.The specimen has higher bearing capacity and stiffness.The energy dissipation performance was improved and the hysteretic curves were more full than “ Flag Shape” of tradition self-centering shear wall.The hysteretic curves have obvious pinching phenomenon,the residual deformation was small,and the maximum residual drift was 0.42%,indicating that the system has self-centering characteristics.The organic combination of reinforced concrete end columns and steel plate braces can increase the horizontal and vertical bearing capacity.At the same time,the energy-consuming frame composed of reinforced concrete end columns and steel plate braces makes the system have multiple seismic lines.(2)Based on the experimental results,numerical simulation of test specimen was conducted using ABAQUS finite element software.The simulated load-displacement curves and stress changes of unbonded prestressed tendons are in good agreement with the experimental results,which proves that the finite element modeling method and selected parameters are reliable.(3)On the basis of verifying the accuracy of the finite element model,a supplementary analysis of the specimen was carried out by changing parameters such as axial compression ratio,unbonded prestressed tendon area,initial stress of unbonded prestressed tendons,section size and yield strength of steel plate braces.Increasing the axial compression ratio will improve the bearing capacity and stiffness of the specimen.Changing the area of the prestress tendons when keeping the initial prestress as same has no effect on the bearing capacity and stiffness.Increasing the initial stress will improve the bearing capacity and stiffness of the specimen.Increasing the section size and yield strength of the steel plate will improve the bearing capacity and energy dissipation of the system at the same time.