Seismic Vulnerability Analysis Of Railway Super-High Pier Based On Incremental Dynamic Analysis

With the rapid development of railway construction in western China,super-high pier long-span bridge has been widely used.This kind of bridge structure is vulnerable and difficult to repair under earthquake,so it is necessary to conduct in-depth research on seismic response analysis of super-high pier bridge structure.In this thesis,a Hshaped double-column thin-walled hollow super-high pier structure in a high-speed railway bridge in the western mountainous area is taken as the object,and the seismic performance and vulnerability assessment of the super-high pier bridge structure are carried out.The main work is as follows:(1)According to the structural characteristics of the super-high pier,the damage index of the super-high pier is taken as the section curvature,and the ground peak acceleration is taken as the intensity index of the ground motion.The global finite element model of super-high pier was established based on ANSYS finite element software,and 15 groups of ground motions were selected as input samples.The seismic responses corresponding to ground motions of different intensities were obtained by elastoplastic dynamic time-history analysis.(2)Based on Increment Dynamic Analysis method,the capacity demand comparison number increment dynamic analysis curve of each control section of superhigh pier is established,and the corresponding fitting curve function is obtained by least square regression analysis.The probabilistic seismic demand model and vulnerability curve of each control section of super-high pier are established,and the seismic performance and seismic vulnerability of super-high pier are evaluated.The single column section of the super-high pier is prone to bridge damage,and the cross beam section is prone to cross bridge damage.The bottom of the pier is the most unfavorable position,and the most unfavorable direction is along the bridge.(3)The damage and failure laws of super-high pier in each group under the action of ground motion are summarized,and the damage and failure modes of H-type doublecolumn thin-walled hollow super-high pier under the action of bi-directional earthquake are proposed.At the same time,the overall seismic vulnerability curve of super-high pier is established by the first-order boundary method.The results show that the super-high pier damage occurs first at the bottom of the pier,then the bridge damage occurs at the top of the pier,and finally the bridge damage occurs at the hollow part of the pier.(4)The parameter influence analysis was carried out,and the vulnerability analysis was carried out by increasing the axial pressure specific gravity of ultra-high pier.The influence of axial compression ratio on seismic vulnerability of ultra-high pier is discussed,and the reliability of damage failure mode obtained above is verified.The results show that the increase of axial compression ratio is beneficial to reduce the longitudinal bridge seismic response of super-high pier,but can improve the transverse bridge seismic response of super-high pier.In general,the increase of axial compression ratio within a certain range is beneficial to improve the overall seismic performance of the super-high pier.