Analysis Of Fragility And Seismic Reliability Of Offshore Isolaed Bridge With Life Cycle

To meet the increasing traffic demand of our country.,Promote the rapid development of social economy,More and more offshore Bridges are being built in our country.Due to the particularity of geographical location,Offshore Bridges are vulnerable to natural disasters such as Marine environment erosion and earthquakes during the service period.With the development of isolation technology,The isolation support is widely used in the seismic field of Bridges.However,The performance of the isolation support is degraded due to the corrosive action of the environment,When the bridge is hit by an earthquake,it can not play its isolation effect effectively.In addition,The performance of reinforced concrete bridge pier in the erosion of Marine chloride ion is also greatly deteriorated.The seismic design concept of traditional Bridges ignores the degradation of seismic performance due to the erosion of environment,to maintain the seismic performance of the bridge life cycle,a large amount of maintenance cost is required for seismic reinforcement.Reinforced concrete piers and isolation bearings are the main stress components of offshore seismic Bridges under earthquake action,within the full life cycle,the influence of performance degradation of bridge piers and supports on seismic performance of offshore seismic Bridges is discussed,The influence of performance degradation of bridge piers and supports on seismic performance of offshore seismic Bridges is discussed,furthermore,it is necessary to analyze the seismic vulnerability and seismic reliability of Bridges in the future.So,this paper considers the isolation and degradation of piers and supports,the corresponding vulnerability and seismic reliability of the bridge are analyzed respectively,the seismic performance of the bridge is evaluated.The specific research contents are as follows:(1)On the basis of previous studies,the erosion process of chloride ion in reinforced concrete structure in Marine environment is described,the performance degradation of reinforced concrete materials under chloride ion erosion is summarized and summarized;according to the research results of the durability test of rubber isolation mount in the early stage of the research group,In this paper,the performance degradation of rubber isolation bearings under Marine erosion is summarized.(2)SAP2000 software is adopted to establish the nonlinear dynamic analysis model of offshore seismic bridge.The corrosion of the longitudinal bars,the rust of stirrups and the joint corrosion are considered separately,bending moment-curvature analysis of bridge pier section in full life cycle,the effect of corrosion on the seismic capacity of the steel structures under chloride ion erosion is discussed.(3)Three types of deterioration conditions are defined,namely,pier deterioration,isolation pedestal deterioration and joint deterioration of both,and the seismic response of Bridges in the whole life cycle is analyzed under three types of deterioration conditions(4)Under three kinds of degradation conditions,to carry out the whole life cycle of Bridges time-varying seismic vulnerability analysis,comparative analysis of different components are separate degradation and degradation effect on seismic performance of the bridge whole life period and failure probability of various kinds of damage state.(5)Calculate the value of earthquake action under different design base period according to the principle of equal transcendental probability;the method of minimum resistance is used to calculate the time-varying seismic reliability of bridge life cycle,the influence of three kinds of deterioration conditions and the design base period on the reliability of time-varying seismic resistance in bridge life cycle is analyzed.(6)The cost of direct economic loss in the whole life cycle of offshore seismic Bridges is evaluated,the effects of three kinds of deterioration conditions,discount rate and subsequent service period on the cost of earthquake loss are discussed.This paper provides a theoretical basis for the evaluation of the seismic performance of the bridge in the whole life cycle,the formulation of the maintenance and reinforcement strategy and the development of the anti-seismic design concept of LCCA.