Research On Seismic Fragility Of Double-layer Special-shaped Continuous Beam Bridge

Our country is one of the countries with more earthquakes.When the earthquake occurs,the destruction of the bridge structure has a serious impact.Especially in recent years,the structure of the pedestrian bridge has become more and more complex,so it is of great significance to propose a specific post-earthquake damage probability for complex bridge structures.In this paper,a double-layer special-shaped continuous beam bridge is taken as the research object,and the following aspects are studied:(1)The finite element model of the double-layer special-shaped continuous beam bridge was established by the finite element software OpenSees.The constitutive relation of materials and the selection of the element types were introduced in detail.In addition,the finite element model was also established by Midas Civil.Comparing the first several modes of the models built by the two finite element software to verify the accuracy of the models built by OpenSees.(2)To determine two important indicators of seismic vulnerability analysis: ground motion intensity parameter and damage index of structural vulnerable members.The peak ground acceleration is used as the ground motion intensity parameter.The support,bridge pier and round bracket are selected as structural vulnerable members.The relative displacement the support,the curvature of the bottom of the pier and the curvature of the bottom of the round bracket are selected as the damage index of each vulnerable member.(3)Probabilistic seismic demand analysis was conducted on the bridge structure.Nonlinear time history analysis was carried out according to the selected ground motion intensity parameters and the demand parameters of each vulnerable component,and the probabilistic seismic demand model of the bridge was obtained by logarithmic regression analysis with Matlab.The required parameters are provided for vulnerability analysis.(4)Vulnerability analysis was conducted on the vulnerable members of the bridge structure.And first-order boundary method and Monte Carlo method were used to analyze the vulnerability of the double-deck bridge.