Vulnerability Analysis Of High-speed Railway Box Girder Bridge Under Near-field Earthquake

Our country is located in the earthquake-prone zone between the Asia-Europe earthquake zone and the Pacific Rim earthquake zone.it has experienced various catastrophic earthquakes in recent decades and caused unpredictable losses to the country.With the development of high-speed rail technology,bridges have become more and more important in the construction of high-speed rail and the importance of earthquake resistance is naturally beyond words.At present,research on isolated bridges has increased,but it is not comprehensive.The seismic analysis method of bridges in the form of vulnerability curve can reflect the probability that the corresponding requirements of the structure of the bridge structure under different earthquakes will exceed the limit resistance of the structure in different damage states.It is necessary to use this method to evaluate the seismic performance of isolated high-speed railway bridges,which can prevent bridges from being damaged by earthquakes to a certain extent.This article takes a 32-meter high-speed railway bridge as an example,and mainly does the following work:(1)Based on the current research status of bridges,the significance and purpose of seismic vulnerability analysis of bridges are introduced.This paper summarized the existing research result of scholars at home and abroad,and the vulnerability analysis steps was explained systematically from the determination of damage indicators and selecting the ground motion.(2)Taking a four-span high-speed railway bridge as the research object,considering the uncertain factors of the bridge,the finite element software SAP2000 is used to establish the analysis model.The ground peak acceleration PGA is used to analysis parameter for the ground motion,and selected 10 qualified far-field earthquake waves from the Ground Motion Database(PEER);Based on the IDA analysis method,the nonlinear time-history analysis is carried out by the finite element model under the action of earthquakes,then conducted the regression analysis of structural seismic response,and the vulnerability curve of bridge pier is established by the linear fitting method of direct regression probability demand model.(3)The mechanical properties of high-damping rubber isolation bearings are described.Based on the high-damping rubber bearings,a new bridge analysis model is established in conjunction with the finite element software SAP2000 to evaluate the seismic performance of the isolated bridges;At the same time,determine the damage index and damage level of the isolated support,and establish the vulnerability curve of the bridge pier and the isolated support,and evaluate the isolated effect of the support from the probability perspective.(4)According to selection principle of near-field earthquakes,10 near-field vibration records is selected.The nonlinear time history analysis of isolated bridges is carried out,and establish the vulnerability curve of isolated bridge pier and support.A detailed comparison and analysis with the vulnerabilities of pier columns and bearings under far-field earthquakes is discussed,and the influence of near-field earthquakes on the seismic performance of isolated bridges is discussed.(5)Under the conditions of the vulnerability analysis results of the bridge members,based on the first-order limit method,the vulnerability curves of the isolated bridge under different earthquakes in the near and far fields are established respectively.Executed comparative analysis of the failure probability of isolated bridges under different earthquakes in this paper,and the overall seismic performance of isolated bridges can be evaluated.