Seimic Fragility And Risk Analysis Of Long-span Road-rail Cable-stayed Bridge

The long-span road-rail cable-stayed bridge is more complex than that of ordinary bridge.Because of its strong span ability,it is very popular in the scheme selection of long-span bridges.However,China is an earthquake prone country,there are large and small earthquakes almost every year.The study on seismic fragility and seismic risk of long span cable stayed bridge is still at the primary stage,and there is no comprehensive specification or experience.Based on the above reasons,this paper takes the bridge of road-rail cable-stayed bridge at ping-tan strait as the engineering background,Based on the present research situation of seismic response and vulnerability of cable-stayed bridges,Referring to the method of seismic vulnerability and risk analysis for general simple supported beam,continuous beam and high pier rigid frame bridge.In this paper In this paper,the damage index of the bridge is put forward,and the method of vulnerability analysis is selected to analyze the seismic vulnerability and risk of the long-span cable-stayed bridge.Through the analysis of the longitudinal and transverse seismic fragility and the risk analysis of the cable-stayed bridge with high piers and high towers,the research conclusions are obtained.The main contents of this paper are summarized as follows:(1)The curvature is used as the control parameter to define the damage index of the main tower of the cable-stayed bridge,the auxiliary pier and the transition pier,and the damage index of the transition pier and the supporting pier is defined by the relative displacement of the pier beam.(2)Based on the actual long-span cable-stayed bridge,the finite element model of the cable-stayed bridge is established based on the OpenSEES software,and this paper describes the various elements of the unit simulation.Finally,the Midas model is built by using the bridge special software to validate the OpenSEES finite element model,and the correctness of the model is proved.(3)In order to determine the control section of vulnerability analysis.The 20 line with the site feature of seismic wave are are selected In this paper,PGA(peak ground acceleration)as a parameter and considering the p-delta effect,A single IDA of seismic wave analysis and multiple seismic elastic-plastic time history analysis are performed respectively,and the longitudinal and transverse axial force and curvature distribution along the pier height are obtained.(4)Considering the uncertainty of ground motion,20 seismic waves were input for IDA analysis,and the results of statistical processing were calculated.Then,the probabilistic seismic demand model of long-span cable-stayed bridge with PGA as the variable was established.(5)In this paper,the vulnerability analysis results of the main members(Main tower,tower beam,auxiliary pier,transition pier,support)of the long span cable stayed bridge are compared,and the vulnerable parts of the cable-stayed bridge and the damage order of each component are analyzed and discussed.(6)Seismic hazard analyses of different earthquake-intensity regions in China are studied.Expressions of risk analysis,coupled with the results of fragility analysis,are used to carry out probabilistic seismic risk analysis of a long-span highway and railway dual-use cable-stayed bridge.The results are therefore analyzed to provide references for future studies.