Seismic Design Method Of Segmental Precast Post-tensioned Piers

Traditional bridge pier construction methods have many disadvantages,such as low construction efficiency,long construction period,interference with traffic,generation of construction waste,impact on surrounding environment,etc.The appearance of precast pier system solves these problems.According to the different connection modes and seismic performance,the precast pier system can be divided into emulative precast pier and nonemulative precast pier.Emulative precast piers have similar mechanical characteristics to monolithic piers,while nonemulative precast piers have the characteristics of swing and selfresetting structures.In the nonemulative precast pier,the segmental precast post-tensioned piers have good seismic performance and are widely used.The post-tensioned unbonded prestressing bar provides the self-resetting ability of the pier,and the energy-consuming bar increases the energy-consuming capacity of the pier.Dry joints are usually used for segment joints.Firstly,a quasi-static test is carried out on the segmental precast post-tensioned piers.The following conclusions can be drawn from the analysis and test results:(1)the higher the energy dissipation bars ratio,the stronger the energy dissipation capacity of the pier;(2)the carrying capacity of the pier can be increased by increasing the energy dissipation bars ratio and pre-stress;(3)Piers with high energy dissipation bars ratio have large residual displacement,and piers with large pre-stress have slightly smaller residual displacement;(4)the size of opening at pier joint is limited by energy dissipation bars ratio and pre-stress;(5)the opening at joint of bearing platform and pier segment is much larger than that at other joint openings,and the corner of pier is mainly provided by the opening at this joint.Subsequently,based on the test results and existing research,the direct displacementbased design and section design method of the segmental precast post-tensioned piers are proposed.And the specific design steps are given respectively.In the direct displacementbased design method,the specific application of design parameters such as pier lateral displacement mode,yield displacement,target displacement and elastic-plastic displacement spectrum is studied and given in this paper.Then the working process of pier is divided into pressure relief state,yield state and limit state.Through stress analysis of each working state,section design method is proposed.Finally,the actual design of a segmental precast post-tensioned pier is carried out by using the design method proposed in this paper.And a solid finite element model was established to verify.According to the results of static elastic-plastic analysis and time-history analysis of the finite element model,the design calculation results of the example are in agreement with the simulation results,which can prove that the design method of the posttensioned pre-fabricated pier proposed in this paper is reasonable.