Research On The Seismic Performance Of The Cup-Shaped Post Cast Socket Precast Pier In High Earthquake Intensity Area

The emergence of assembled construction has greatly improved the speed of project construction,and also has the advantages of safety,environmental protection and reliable quality,which is the key development direction of China’s future engineering construction.The connection technology between prefabricated piers and pile foundation is one of the key technologies in the assembled bridge construction.This paper takes a high intensity area highway project in Xinjiang as the supporting project,the steel plate composite girder bridge in this project adopts a new type of cup-shaped post cast socket precast piers,in which the cup adopts UHPC material,the precast pier structure is novel,no need to leave holes in the bearing platform like the traditional socket piers,the construction is more convenient and the connection performance is reliable.In this paper,through the pseudo static test and finite element numerical simulation,the seismic performance of the cup-shaped post cast socket precast pier is systematically studied to ensure the safe application of these piers on the one hand,and to provide the technical basis for the large-scale construction and popularization of these precast piers on the other hand.The main contents of this paper and its related conclusions are as follows:(1)Based on the actual scheme of cup-and-cast socketed precast piers,two scaled-down models of bearing platform and pier cast-in-situ and UHPC cup-shaped post cast socketed piers were designed for the proposed static tests,and data such as hysteretic curves,backbone curves,plastic hinge position and reinforcement strain of the two specimens were obtained.The test results show that the plastic hinge position of the pier of the cup-shaped post cast specimen is located within a certain range above the cup,and the hysteretic curve of the cup-shaped post cast specimen is fuller,with better energy dissipation capacity and higher horizontal bearing capacity;(2)A refined nonlinear finite element model of the bridge pier was established based on the Open Sees platform,and the numerical simulation of the whole test process was carried out,and the correctness of the modeling method was determined through the comparative analysis of the test data and the numerical simulation.On this basis,the refined nonlinear finite element model of the frame pier and the refined nonlinear finite element model of the whole bridge,which are the same as the actual project,are established;(3)For the frame pier,under the reciprocating load,the longitudinal plastic region appears only above the top surface of the cup,while the transverse plastic region appears both above the top surface of the cup and at the top of the pier.The pier height and reinforcement rate have significant effects on the seismic performance of the piers,while the axial pressure ratio,diameter of cup and stirrup rate have less effects.From the structural size,structure and economy,the actual diameter of cup is close to the optimal value;(4)Under the same ground vibration excitation,the seismic response generated by near-field pulse-like ground motion is significantly larger than the far-field vibration,and the near-field vibration with forward directional effect is larger than the near-field vibration with slip effect.The influence of pier height and reinforcement rate on the seismic response of bridge pier displacement is significant,while the influence of axial pressure ratio and stirrup rate on the seismic response of bridge displacement is small.On this basis,the actual bridge design scheme was verified to have reliable seismic safety.