Effects Of Soil-structure Interaction On Structural Response Of Shallow Foundation Bridges Subjected To Earthquake Loads

Most of the shallow foundation bridges constructed based on the current seismic design code had not taken anti-seismic checking calculation,or at most this kind of bridges were regarded as cantilever structure that fixed on the rigid foundation.However,soil-structure interaction(SSI)were not considered under these circumstances,and these traditional methods could not effectively predict the dynamic response of an actual bridge under earthquake.Some scholars had considered the SSI effect in their study,but the research was not systematic enough.It was an urgent task to study the SSI of shallow foundation bridges.In this paper a simplified model of shallow foundation bridge considering SSI was established,then this paper systematically studied the effect of SSI on seismic response of bridges.Parameters analysis on seismic response of shallow foundation bridges considering SSI was also conducted.The works of this paper were as follows:(1)Fixed base model without SSI and linear SSI model and nonlinear SSI model of shallow foundation bridges were formulated separately using ruaumoko-3D,and then we verified the correctness of the model though comparison with other modeling method and examples from other papers published before.(2)By comparing the seismic response of linear SSI model and fixed base model,nonlinear SSI model and fixed base model,the effect of SSI on bridge seismic response was analyzed.The results shown that the swing separation response of the shallow foundation of linear soil interaction and the hysteretic characteristics of soil greatly dissipated the seismic energy,we considered SSI effect on structural seismic response in order to get a more accurate analysis results.However,the increase of the displacement response and the generation of residual displacement also bring about some new subject of studies.In addition,through the comparison of seismic response of linear SSI model and nonlinear SSI model,the influence of different types of SSI on bridge seismic response was analyzed.(3)We established simplified models of bridge considering linear and nonlinear soil-structure interaction separately based on macro-element method,then changed soil shear wave velocity,the width of foundation,soil cohesion separately and kept other parameters of the system unchanged so as to study the impact of the parameters changing on the seismic response.The results shown that the larger shear wave velocity and the larger base width are beneficial to reduce the seismic response of the bridge.However,the increase of the width of the bridge put forward higher requirements of the foundation bearing capacity,in the seismic design of shallow foundation bridges,it was necessary to take into account both the pier top displacement limit requirements and the bearing capacity.Special attention was needed when considering linear soil-structure interaction soil cohesion had no effect on structural response,however,when considering nonlinear soil-structure interaction,the displacement got smaller and the acceleration got larger with the increase of soil cohesion.When soil cohesion was less than a certain value,toppling of the structure happened.