Study On Seismic Performance Of Prefabricated High-speed Railway Bridge With Large Diameter PHC Pipe Pile

In recent years,the application of prefabricated assembly method in infrastructure construction in China has gradually increased.Prefabricated PHC pipe piles and assembled piers are two important components.Experts and scholars at home and abroad have carried out extensive theoretical analysis and experimental research on them.Based on the research and development plan of China Railway Corporation(P2018G004)’ Key Technology Research of Intelligent Jingxiong ’,this paper analyzes the mechanical performance and seismic response of assembled piers based on the test of large diameter prestressed pipe pile(PHC)and the structural performance test of assembled piers.The main research contents and conclusions are as follows :(1)The static performance test of large diameter PHC pipe pile and pile head connection is carried out.The parameters of soil spring at each depth of pile are obtained by P-Y method.The finite element simulation of pile-soil system is carried out and the parameter analysis is carried out.It is found that the initial prestress and stirrup reinforcement ratio have little influence on the static performance of pipe pile,but have great influence on the pile head connection.(2)The influence of axial compression ratio,initial prestress and reinforcement ratio on the seismic performance of PHC pipe pile is studied.It is found that the axial compression ratio should be controlled within 0.35,the initial prestress should be 900～ 1094 MPa and the reinforcement ratio should be 0.66 % ～ 0.81 % to meet the engineering needs.The effects of prestressed reinforcement,spiral stirrups and anchor reinforcement on the seismic performance of the connection between PHC pipe pile and pile cap are studied.It is found that reducing the number and diameter of prestressed reinforcement and increasing the spacing of stirrups will reduce the bearing capacity and energy dissipation capacity of the structure.(3)The finite element models of assembly pier and cast-in-place pier connected by grouting sleeve are established and checked according to the results of full-scale model test.The hysteretic curves,skeleton curves and stiffness degradation curves of assembly pier,cast-in-place pier and actual assembly pier considering pile-soil effect are compared and analyzed.The results show that the seismic performance of assembly pier and cast-in-place pier is close,and the initial stiffness,energy dissipation and residual deformation are reduced after considering pile-soil effect.(4)A two-span simply supported bridge model with assembled piers and cast-in-place piers was established.Three sets of seismic waves conforming to the location of the bridge were selected to study the seismic response of the two under the action of frequent earthquakes and rare earthquakes.It was found that under frequent earthquakes,assembled piers and cast-in-place piers are in the elastic stage;under rare earthquakes,the displacement ductility ratio meets the specification requirements.The seismic response of the bridge using the assembled pier and the cast-in-place pier is close,indicating that the assembled pier can meet the seismic needs in the actual project.