Seismic Vulnerability Analysis Of Long-Span Continuous Beam Bridge

In recent decades,many major earthquakes have occurred at home and abroad,causing huge casualties and economic losses to the human society.As the most important part of the traffic system,the bridge structure has proved to be easily damaged in the previous earthquake disaster.The damage degree of the bridge is of great significance to evaluate the residual function of the highway system,predict the direct economic loss and guide the rescue and transportation.With the acceleration of the modernization process in our country,the multi-span continuous beam bridge is widely used for its strong spanning ability,reasonable force and good continuity.The seismic vulnerability analysis of such bridges can be used to prevent from bridge earthquake disaster.In this thesis,combined with engineering examples,the main work is as follows:(1)The purpose and significance of bridge seismic vulnerability are introduced.This paper summarizes the current research of scholars at home and abroad,and systematically expounds the analysis process of theoretical vulnerability from the input of ground motion,the determination of damage index and the establishment method of vulnerability curve.(2)Taking the highway long-span continuous beam bridge as the research object,the OpenSees finite element model is established.The ground motion parameter provided by"Safety Assessment Report" was used to generate the target spectrum and then the artificial seismic wave was generated.The bending curvature of the control section was analyzed,and the damage degree was divided to five parts using the displacement ductility ratio as the damage quantification index.Based on the IDA method,the nonlinear dynamic analysis was carried out by the finite element model,and the logarithmic linear regression analysis of the seismic response data and the ground motion strength parameters was carried out to establish the theoretical vulnerability curve of bridge pier.(3)This paper introduces the force characteristics and the isolation principle of the friction pendulum bearings,isolates the OpenSees finite element model to evaluate the seismic performance of the isolated bridge,and finally establishes the friction pendulum bearings vulnerability curve and pier vulnerability curve.The effect of bearing isolation is evaluated from the perspective of probability by the contrast of pier vulnerability curve before and after the bridge isolation.(4)In this paper,the reliability theory of structural system is introduced.On the basis of the vulnerability analysis of bridge structure,the first order boundary method is used to calculate the over-probability of the damage state of the bridge system under different ground strength.Based on the theory of vulnerability,the relevant formula is used to calculate the change of traffic flow and traffic time after the earthquake.The capacity of the bridge after the earthquake can be evaluated quickly,and it can provide certain reference value for decision-makers to grasp the overall disaster area traffic and make more reasonable and more effective relief plans.