Research On The Residual Deformation Mechanism Of Bridge Pier Considering Pile-Soil Interaction

The basic theory of the aseismic design of bridges is the further study of mechanism of seismic damage.It is generally believed that pier’s residual displacement is caused by bending properties of the structure itself,strain penetrating effect of longitudinal reinforcement and bond slip effect.However,the complicated pile-soil nonlinear behavior is not discussed and the impact on seismic performance of the pier is unclear.So this paper makes a further study on pile-soil-pier interaction and meanwhile provides a basis for the aseismic design of bridges in consideration of pile-soil interaction.The main work contents and conclusions are as follows:1.The pile-soil interaction is elaborated.According to the pile-soil interaction in the API specification,p-y springs,t-z springs,q-z springs are used to simulate the pile-soil horizontal interaction and vertical pile-soil interaction respectively.The group pile-soil-pier interaction analysis model is built,and the accuracy of the model is verified.Finally,the impact of hardness of clay on pier capacity and force distribution of each pile group foundation are discussed in the paper.The result shows that the group pile-soil-pier interaction numerical analysis model reflects pile-soil interaction nonlinearity,and the outside piles’ internal force is generally larger than the inner piles’.2.In order to study the seismic performance of the pier and the pile in the pile-soil interaction,the single pile-soil nonlinear numerical analysis model is built based on the OpenSees numerical analysis platform,and the accuracy of the model is verified by comparing with the experimental results.On such basis,the single pile-soil-pier nonlinear numerical analysis model is built.By using ductility factor of the pier,curvature ductility factor of the pile zone length of the pile as the indexes of evaluation,and by adopting the method of quasi-static force analysis,piers and pile damage are discussed.The results show that pier and pile are both in nonlinear condition in consideration of pile-soil interaction.With the increase of sand constraint,the pier’s capacity and displacement ductility factor are also enlarged,the palstic length of pile and the residual displacement angle both get smaller.3.According to the numerical analysis,the seismic performance of piers in the pile-soil interaction is discussed.The single pile-soil-pier and group pile-soil-pier interaction analysis dynamic numerical analysis models are built respectively.The impact of pile-soil interaction on maximum displacement of the pier top and the residual displacement is concerned and meanwhile the constituent parts of residual displacement is also analyzed.The results indicates that pile-soil interaction will intensify the maximum displacement of pier top and the residual displacement.The result also shows that,apart from pier nonlinearity and the strain penetrating effect of steel,pile nonlinearity and the pile-soil interaction can also lead to the residual displacement.