Study On Seismic Behavior Of High-speed Railway Continuous Rigid Frame Bridge Considering Sand Liquefaction

Bridges occupy a large proportion in high-speed railway and are an important part of high-speed railway.The seismic capacity of bridges also directly affects the damage degree of high-speed railway under earthquake.Because of its own characteristics,continuous rigid frame bridges are widely used on the main lines in earthquake-prone areas.Therefore,it is of great significance to study the seismic performance and seismic vulnerability analysis of continuous rigid frame bridges.In this paper,a high-speed railway continuous rigid frame bridge is studied,and the following aspects of work are carried out:(1)The model of High-speed Railway Continuous Rigid Frame Bridge Considering sand liquefaction is established,and compared with the model without considering sand liquefaction,the influence of sand liquefaction on the finite element model of bridge is studied.(2)The response spectrum method is used to calculate the seismic response of bridges under frequent earthquakes.Each checking index should not exceed the limit value required by the code.Nonlinear time history analysis method is used to calculate the seismic response of bridges under rare earthquakes.Plastic hinges are set at specific locations of piers to simulate the deformation of structures after plasticity.The seismic response of bridges is obtained and the ductility of piers is checked.(3)Determine the lateral load distribution of static elastic-plastic analysis,locate the displacement control points and calculate the control displacement of the control points,carry out static elastic-plastic analysis of the bridge,and select the capacity spectrum method to obtain the seismic response of the structure.The vulnerability curve of the bridge is obtained from the results of static elastic-plastic analysis.The seismic performance of the bridge is evaluated according to the obtained vulnerability curve.(4)Incremental dynamic analysis of bridges is carried out to determine the seismic demand of bridges.The ratio of demand capacity to peak ground motion acceleration PGA is plotted in logarithmic coordinates and the curve is fitted.On this basis,the longitudinal vulnerability curve of piers is established.The seismic performance of the bridge is evaluated and the vulnerability curves obtained by the two methods are compared.(5)Constant pier-height continuous rigid frame bridge models with pier heights of 30m,40m and 50m are established,and corresponding vulnerability curves are obtained by IDA method,so as to study the influence of pier heights on seismic vulnerability of bridges.