Seismic Vulnerability And Risk Analysis Of V-Supported Continuous Beam Bridges With Performance Degradation

The earthquake has been one of the major disasters of various engineering structures.As a pivotal project of transportation,the bridge's seismic capacity and reinforcement after the earthquake are urgent issues for engineers.As a kind of bridge structure with high rigidity,the V-supported continuous beam bridge has little research on the damage state and seismic risk probability after the earthquake.At the same time,due to the increasing number of service bridges in China,the seismic performance evaluation of already serviced bridges in harsh environments needs further research.Therefore,the seismic vulnerability and seismic risk of a V-supported continuous beam bridge under chloride ion erosion are studied.The main research contents are as follows:The paper calculates curvature ductility and displacement ductility as damage indicators of bridge piers and supports,and considers the uncertainty of ground motion.In this paper,100 seismic waves are selected and a three-span V-supported continuous beam model is established based on OpenSEES.The structure under earthquake is obtained,and the probability requirement model of each component is obtained by linear regression.In this paper,the seismic vulnerability curves of each component are established by comparing the probabilistic demand and seismic performance.Finally,the vulnerability curves of the V-supported continuous beam bridge system are obtained by using the first-order bound method and the Monte-Carlo method.This paper considers the erosion effect of chloride ion,obtains the degradation function of reinforced concrete after chloride ion erosion,and updates the model to obtain the seismic response of the bridge after chloride ion erosion during service.The probabilistic demand model of each member under chloride ion erosion is obtained by regression,and the seismic behavior of the V-support and transition piers after material degradation under longitudinal reinforcement and stirrup rust is analyzed separately,and the damage index of the member after time-varying is obtained.Since the environment in which the structure is located is a humid environment,chloride ion corrosion is selected as a factor of degradation of the material.The time-dependent seismic vulnerability curve of the V-supported continuous beam bridge under the chloride ion erosion is obtained by the seismic capacity and seismic demand of the material after the material degradation.This paper combines the various components to obtain the time-varying seismic vulnerability curve of the structural system,and compares the upper and lower bounds of the system vulnerability curve.The seismic hazard curve of the site is obtained through the information of the site of the bridge,and the annual probability seismic risk of the component is obtained from the seismic vulnerability function.It converts the annual earthquake risk probability into probability of earthquake risk by components and systems under the 100-year design basis,and makes a risk assessment of the V-supported continuous beam bridge under chloride ion erosion.