Longitudinal And Transverse Seismic Fragility Analysis Of Long Span Cable Stayed Bridges

Earthquake,as a kind of geological disaster with strong destructive force,has caused great damage and harm to human society.In recent years,with the wide application of long-span cable-stayed bridges,it has gradually become a control project of traffic lines.Once damaged or damaged,it will cause huge losses to life and social economy.As an important bearing component of cable-stayed bridge,it is necessary to analyze its seismic vulnerability,judge its vulnerable parts and guide seismic design conveniently.It is an important research content in bridge seismic engineering,and has very important scientific and economic significance.Taking a Yellow River Bridge in Shaanxi Province as an example,the incremental dynamic analysis(IDA)and seismic vulnerability analysis of the long-span cable-stayed bridge are carried out by using the finite element software sap2000.The main contents and conclusions of this paper are as follows:(1)The research background and current situation of bridge structure vulnerability under earthquake are introduced in detail,and the method of establishing theoretical vulnerability curve is summarized.(2)Some common methods of bridge seismic response analysis are introduced,including static method,dynamic time history analysis and incremental dynamic analysis.(3)This paper introduces the establishment method of vulnerability curve,chooses the Capacity-Demand ratio model method to fit the vulnerability curve through comparison,and introduces the selection of ground motion records,including the main factors considered when selecting seismic waves and the selection of ground motion parameters,and introduces the calibration method of the damage index of the key section of cable-stayed bridge pylon adopted in this paper.(4)The SAP2000 finite element model of the bridge is established and its dynamic characteristics are analyzed.The bending moment curvature analysis and damage calibration of the key section of the main tower of the bridge are carried out by using XTRACT software.Ten seismic waves are selected and classified into different grades.Longitudinal and transverse seismic input is made to the bridge.Then IDA analysis is carried out on the key sections of the main tower.The vulnerability curves of the four damage states of the key section of the main tower are drawn,and the vulnerable parts and variation rules of the main tower are further determined.The vulnerability curves of different sections in the same damage state are plotted in the same Cartesian coordinate system to facilitate the comparative analysis of the vulnerability of each section of the main tower.The results show that the bottom section of the lower column of the main tower is the most vulnerable section,and the middle section of the middle column is the least vulnerable section under the action of both transverse and longitudinal seismic waves.