Study On Seismic Performance Of Horizontally Assembled Self-Centering Bridge Pier

Many damages or even collapse of bridges occurs during strong ground motions in the world.Recently,self-centering system have been extensively developed and investigated to improve the seismic performance of the bridges.The popular way of past self-centering systems is to assemble one or several precast pier segments in series vertically through unbonded post-tensioning tendons,from bottom to the top,and the energy dissipation devices are usually installed near the pier foot.However,crack may also appear in the damper connecting area due to the stress concentration.Therefore,in view of bridgr pier of wide cross section,this study proposes a novel horizontally assembled self-centering bridge(HASCB)system which consists of two pier segments,two post-tensioning tendons and several distributed steel connecters.This system can increase energy dissipation and reduce the damage of structure to improve the seismic performance.Specific contents are as follows:(1)A simplified mechanism diagram of HASCB system of damper ecentralized arrangement is established to investigate the relationship between the lateral force and deformation(including gap close-open process).The hysteresis character is also studied,including its influencing factors and the relationshape between pier bottom shear force and top displacement.(2)A parametric analysis of steel connectors including its size(effective width and thickness),shape and quantity is carried out to examine the corresponding effect on the energy dissipation ability and damage distribution.And a simplified mechanical theoretical model of damper is established to further study the influence energy dissipation capacity and damage distribution.(3)One optimal energy dissipating connector is selected and a finite element model(FEM)of HASCB system is developed to investigate the pivotal parameter of carrying capacity and self-centering ability.The self-centering ability and energy dissipation capacity of HASCB system are evaluated through the FEM simulation in detail,including the lateral force–displacement hysteretic properties,unbonded tendon stress,concrete compressive strains,connector deformation,and time-frequency characteristics.(4)The equivalent SDOF analysis model and motion equation considering rigid body rotation are established,and correctness is been verified through the FEM simulation.The relationshape between hysteresis parameters and the ground motion response is studied,and the ground motion response and time-frequency response of HASCB caused by near-field and far-field earthquake are comparative investigated.