Experimental Investigation On Seismic Performance Of PHC Pile In Integral Abutment Bridge

Under temperature and seismic load,pile foundation of integral abutment bridges bear a type of cyclic loading,which need the piles have good deformation capacity,cracking resistance and seismic performance.H-steel piles are most commonly used in integral abutment bridges abroad,while in China,concrete piles are the first choice for bridge engineering because of economy and engineers' habits.Prestressed high-strength concrete pile(PHC pile)is put into industrialized production.PHC pile is a popular type of pile foundation,it has a remarkable cracking resistance because of large prestress,and in addition,its deformation capacity is also good and enormously used in building and large bridge engineering.However,there is no reports about using PHC piles in the integral abutment bridges and the seismic performance of PHC piles need further study.The work and conclusion of this paper are shown as below:(1)Quasi-static experiments of low cyclic repeated horizontal loading on PHC piles are conducted.Test results show that main failure area of PHC piles are around embedded depth of 4 to 8 times pile diameter,under low cyclic repeated horizontal loading.Meanwhile,wall thickness and prestress degree have significant effect on failure modes and cracks distribution of PHC piles,which lead to internal force redistribution and movement of the maximal bending moment.With high ratio of reinforcement and prestress degree,PHC piles have larger elastic critical displacement and better deformation capacity,as well as a better interaction with the soil.Furthermore,results show that in elastic stage,pile contributes much more than soil to the horizontal bearing capacity.Results also show that PHC piles has a good ductility,in the early loading stages,hysteresis loops are of shuttle shape,which illustrates that the piles have good anti-seismic performance and energy-dissipating capacity.Rheostriction effect of hysteretic curve occurs after the appearance of separation between pile and soil.(2)Experimental results illustrate that larger displacement load will cause huge soil pressure around the pile,the pressure is close to the ultimate passive earth pressure.Area around embedded depth of 0 to 7 times pile diameter has large soil pressure,in which value of 5 times pile diameter embedded depth is largest.Regularities of soil pressure distribution is increasing rapidly from soil surface,then decline gradually after reaching the maximual value and reach a small negative value at a deep depth.(3)Depend on the tests results,pile displacement distribution and soil pressure calculating methods are presented,as well as a simplified calculating method of PHC pile-soil interaction.Results are compared with that of m and p-y method,which illustrate that m method overestimate the lateral bearing capacity of pile and load-displacement curve is not correct,while p-y method has accurate results when the displacement load is not large,however,the load-displacement curve don't have a failure or descent stage,which means that p-y method overestimate the ductility and is partial unsafe.Method presented in this paper can calculate pile internal force,displacement and soil pressure results accurately,which provides reference for related standards.(4)Finite element analysis on PHC pile-soil interaction is conducted via ABAQUS.In parameter analysis,effects of prestress degree,wall thickness(reinforcement ratio)and axial compression ratio on soil-pile interaction have been studied.Results show that effects of prestress degree and axial compression ratio on soil-pile interaction are significant,while that of wall thickness(reinforcement ratio)is comparative less.