Seismic Fragility Analysis Of Reinforced Concrete Bridge Piers Considering The Effect Of Pile-soil Interaction

Bridges are the most susceptible part of the highway network system to earthquakes.The collapse of bridges under the action of earthquakes will hinder disaster relief channels and restrict post-disaster economic recovery.Pier is the main supporting component of the bridge structure.Its seismic damage will seriously affect the damage degree of the whole bridge.Therefore,there is an enormous meaning to evaluate the precise evaluation of the seismic damage performance of piers.There have been certain researches on the seismic fragility analysis of the pier in our country,however,the seismic fragility of piers considering pile-soil interaction impact is relatively little.This research conducted seismic fragility analysis for two pier models regarding and regardless of pile-soil interaction impacts.And when considering the effect of pile-soil interaction,the influence of reinforcement percentage,axial pressure ratio,and foundation soil material on the seismic vulnerability of piers are explored.The content and conclusions of this research are shown below:(1)In this research,eight pier numerical models are established by using Open Sees.PGA is selected as the ground motion intensity index and the displacement ductility ratio as the damage index.18 seismic waves along the bridge are input into the pier model after amplitude modulation for 20 times,respectively,and the seismic fragility of the pier model is analyzed based on the incremental dynamic method.(2)On the basis of only changing the treatment form of pier substructure,the pier bottom consolidation model and pile-soil-pier model are established,the seismic fragility of the two models is analyzed,and the influence of pile-soil interaction effect on pier seismic fragility is studied by comparing the pier seismic fragility curves of the two models,the conclusions are shown below: the seismic damage resistance of pier decreases with the increase of ground motion intensity;under the action of earthquakes,Non-linear deformation of hard clay occurs,and the overall rigidity of the pile-soil-pier model is lower than the overall rigidity of the pier bottom consolidation model.Piers that consider the impact of pile-soil interaction are more likely to have earthquake damage than those that do not consider the impact of pile-soil interaction.Therefore,when the foundation soil material is hard clay,the seismic design of bridge piers should incorporate the effect of pile-soil interaction.(3)The seismic fragility analysis of piers considering pile-soil interaction impact,which only change the reinforcement ratio or axial pressure ratio or foundation soil material,is carried out,and the seismic fragility curves of piers under the same damage level are compared respectively.In the case of considering the pile-soil interaction,when the local vibration intensity is the same,the following conclusion can be drawn:The probability of four kinds of damage of pier decreases with the increase of reinforcement ratio of pier;the four damage probabilities of piers increase with the increase of axial compression ratio,and the fragility of the pier can be improved by appropriately reducing the axial compression ratio;different foundation soil materials also have a certain impact on the seismic fragility of bridge piers.Because soft clay will have a nonlinear deformation greater than that of neutral clay and hard clay under the action of an earthquake,when the foundation soil material is soft clay,the resistance of the pier to fragility sexual ability is the worst.The research results of this thesis have a certain reference value for the research on the fragility of reinforced concrete bridge piers.