RESEARCH ON ABUTMENT ASEISMIC PERFORMANCE CONSIDERING INTERACTION OF SOIL,SUPERSTRUCTURE AND ABUTMENT

Exciting earthquakes always cause larger displacement and settlement in abutment,which induce relative displacement between the superstructures and the bearing capacity of abutment.When the relative displacement is large enough,the superstructure will fall down and the bridge will lose its normal performance.In the past,the effects of soil-structure interaction such as uplift of foundation and yielding of underlying soil are not considered in the aseismic design of bridges.In order to evaluate the aseismic performance,the response of an abutment supported by spread foundation is analyzed under earthquake with time-dependent Newmark analysis.By utilizing discrete element method,the soil,superstructure and abutment systems are simulated by mass-spring models.In the discrete model,the pounding between the superstructure and the abutment,the elastoplastic responses of the backfill soil and the underlying soil are modeled by nonlinear springs.Moreover,the Winkler soil spring is used to simulate the interaction between the foundation of abutment and the underlying soil.The results show that the seismic isolation effect of foundation uplift is significant by alleviating pounding between the superstructure and abutment,and the plastic deformation of the plastic hinge regions at the bottom of the abutment stem is reduced.At the same time,the yielding of underlying soil also reduces the plastic deformation of abutment stem,and increases the effect of foundation uplift.However,the settlement induced by the yielding of underlying soil will make the tilt of abutment.Therefore,the soil,superstructure and abutment interaction such as foundation uplift and yielding of underlying soil should be considered in the aseismic design of bridges.