Experimental Research On Seismic Behavior Of Integral Abutment-Pile Joint

Integral abutment bridges eliminate the expansion joints and bearings at the abutment,and the abutment walls are connected monolithically with the girders.The girder deformation is accommodated by the flexible piles below the abutment.Integral abutment bridge is receiving more and more attention from bridge designers,resulting from easier maintenance,reduced costs,and an enhanced capacity of resisting catastrophic events.When the earthquake occurs,the abutment,backfill,piles and foundation soil all participate in resisting the earthquake,which changes the load condition and the failure mode of abutment-pile joint,and improves the requirement to pile foundation flexibility.The current researches on seismic performance of integral abutment-pile,especially experimental studies,are limited,which limits the development of theory research and application of this type of bridge.Therefore,the experimental study on seismic performance of integral abutment-pile joint has a great practical significance.This paper emphasized on the experiments and analyses of six integral abutmentsteel H pile joint specimens under low-cycle cyclic test,and investigated the influence of adopting crumb rubber concrete in local region of the abutment,and wrapping rubber plate in the tip of steel pile on the seismic performance when the steel pile bends about strong or weak axis.The models were established using ABAQUS,and the results obtained from hysteretic analysis were in good agreement with the seismic performance test results,which verifies the correctness of the model.On this basis,a series of pushover analyses was conducted,investigating the influences of axial compression ratio,rubber content,steel type,and rubber plate thickness.The main conclusions are:(1)The bending axis of steel H pile has a big influence on seismic performance of the joint.The energy dissipation capacity and flexural capacity of weak axis bending specimen is worse than strong axis bending specimen,but the failure displacement and ductility is the opposite.(2)After adopting crumb rubber concrete in local region of the abutment,concrete cracks are obviously reduced,the initial lateral stiffness of the specimen is reduced,but the stiffness degradation speed is slower;Adding crumb rubber has a small influence on the bearing capacity of the specimen,but increases the yielding lateral displacement,and is not conducive to the improvement of ductility of the whole system;The local use of crumb rubber concrete has a small influence on the damping coefficient,but reduces the total energy dissipation to a certain extent.(3)Wrapping rubber plate in the tip of steel pile reduces the initial lateral stiffness,but has a small influence on the lateral stiffness in the late loading.Wrapping rubber plate significantly reduces the bearing capacity,increases the failure displacement and the system ductility to a certain extent.Wrapping rubber plate can reduce strength degradation coefficient,and the reducing amount increases with the lateral displacement.(4)When the axial compression ratio increases,the flexural capacity decreases,the initial lateral stiffness and displacement capacity of weak axis bending specimens decreases,but the influence on the strong axis bending specimens is small.The influence of rubber content on the flexural capacity,initial lateral stiffness and displacement capacity is small.Increasing the steel grade can increase the flexural capacity obviously.When rubber plate thickness increases,the initial lateral stiffness and flexural capacity decreases,and the displacement capacity increases.