Study On The Probabilistic Seismic Damage Characteristics Of Urban Rail Transit Bridge With Different Reinforcement Levels

Along with the rapid development of urban rail transit in our country,an increasing number of urban rail transit viaducts as an import base form of line font have been constructed.Nevertheless,the earthquake damage characteristics especially the probabilistic seismic damage characteristics of urban rail transit bridge also need to be studied nowadays.An large span continuous girder viaduct of Shenzhen Metro was used as an engineering background,and a group of strong earthquake records were selected,the fragility analysis of urban rail transit bridge with different reinforcement levels were studied systematically by IDA analysis method.The main research cnotents are as following:(1)On the basis of considering soil-pile interaction,the nonlinear bridge model with track system or not were established by OpenSEES finite element platform.And the influence of track system on the natural vibration characteristics of urban rail transit bridge were compared and analyzed.(2)The peak accelerations of 15 seismic waves which were selected were adjusted,the earthquake response of urban rail transit bridge was analysed by IDA method,the IDA curves and the corresponding percentile curves of fixed pile were drawn.The damage states of urban rail transit bridge under different seismic intensities were also assessed.(3)The moment curvature characteristics of rectangular reinforced concrete pier section under different reinforcement level were analysed.The varieties of diameter and quantity of longitudinal reinforcement,stirrup space,and diameter with consistent longitudinal reinforcement ratio were indentified as four conditions of reinforcement levels.The dynamic response of bridge models under different reinforcement level was analysed by IDA method,the damage characteristics of fixed pier in earthquake were studied.IDA probability score curves for bridge models under differentworking conditions were calculated respectively,and their comparison and analysis were done.The influence of reinforcement levels on damage characteristics of pier under the action of earthquake were analysed.(4)The seismic vulnerability analysis of bridge with different reinforcement levels was studied based on the results of IDA analysis.The linear regression method was used to establish the functional relationship between the ground motion demand parameters and the ground motion intensity index.The transcendental probability formula for each state of failure were obtained,the fragility curves were set up.The influences about the fragility curves of urban rail transit bridge were studied,the varieties of diameter and quantity of longitudinal reinforcement,stirrup space,and diameter with consistent longitudinal reinforcement ratio were all considered.