Seismic Response Of A Continuous Bridge With Dynamic Soil-structure Interaction

Bridges are crucial parts of a transportation system.Once the earthquake disaster occurs,the bridge will play an extremely important role in emergency rescue and earthquake relief.However,the seismic design of most bridge structuress is based on the assumption of rigid connection between foundation and the ground,and it does not consider the influence of dynamic soil-structure interaction.As a result,the seismic design may not be safe,reliable and economical.In this thesis,the influence of dynamic soil-structure interaction on the seismic response of a continuous beam bridge is investigated by the finite element method.The main work of this paper is as follows:(1)The seismic damage types and seismic analysis methods of bridge structures are summarized,and the analysis methods and the computational models of dynamic soil-structure interaction are compared and discussed.Also,the seismic time history of a three-span continuous bridge is analyzed by the dynamic finite element method.(2)A three-dimensional solid finite element model is built to simulate the soil-strcuture interaction.The bridge and soil are discretized as all solid elements and the soil boundary is discretized as infinite elements.The contact interface of pile and soil is simulated by master-slave contact elements based on the surface contact,and the soil constitutive relationship is a Mohr-Coulomb model.The initial stress balance,damping ratio and computational process control are also discussed.(3)The dynamic interaction between a pier foundation of a simply supported beam bridge and the soil was numerically simulated by finite element method.This paper analyzes and compares the natural vibration characteristics and seismic time-history response of bridge piers with and without considering soil-structure dynamic interaction,considers the influence of contact nonlinear behavior in the calculation,and analyzes the contact pressure and relative slip of pile-soil contact interface under earthquake action.In order to verify the proposed finite element model,the dynamic interaction between a pier of a simply supported beam bridge and the surrounding soil is numerically simulated.The results show that,by considering the dynamic interaction between soil and structure,the natural vibration frequency of the pier decreases,the acceleration of the pier top decreases,the displacement increases,and the stress and internal force of the structure decrease.The pile-soil contact pressure is larger at the pile top and at the middle part of the pile body,while it is smaller at the pile bottom part.The pile-soil slip is larger at the pile top and smaller at the pile bottom.After considering the contact nonlinearity,the distribution of the amplitude of pile shear stress show a trend of decreasing first and then increasing.(4)Using the proposed pile-soil interaction model,the natural vibration characteristics and seismic response of a continuous beam bridge with dynamic soil-structure interaction are investigated and discussed.The results show that considering the action of pile and soil,the natural vibration frequency of the structure decreases.Under the simultaneous action of single longitudinal earthquake action,single transverse earthquake action,and transverse plus longitudinal earthquake actions,the acceleration response of the structure decreases,the displacement response increases,and the stress and internal force responses of the main pier decreases,while the stress and internal force response of the main girder increase.