| Traditional bridge design concepts only consider the seismic behavior of the initial construction,but neglect the degradation of seismic behavior caused by service environmental factors.In recent years,the influence of pier deterioration on seismic behavior of offshore bridges has been mainly studied,but the influence of bearing deterioration has not been considered.Based on this,this paper takes an offshore high-damping Isolation Bridge as the research object,considering the deterioration of high-damping isolation bearing and bridge pier,compares and analyses the seismic response of Isolation Bridge Structure under three deterioration conditions,namely,the deterioration of pier column alone,the deterioration of high-damping isolation bearing,the deterioration of pier column and bearing together.In addition,based on the performance-based probabilistic seismic analysis method,the seismic vulnerability of isolated bridges is analyzed by the central composite design response surface method,and the seismic vulnerability curves of piers columns,bearings and other components in the life cycle are obtained.It provides the basis for the seismic performance evaluation,monitoring,maintenance and reinforcement strategy of the existing isolation bridges in the whole life cycle.At the same time,it provides the theoretical basis for the development of the isolation bridges to be built based on LCCA seismic design concept.The main research contents are as follows:(1)Summarizing the relevant research at home and abroad,the function models of different corrosion current densities,the diameter degradation models of uniform corrosion and pitting corrosion of steel bars,the yield strength degradation model of steel bars and the concrete degradation model are given.At the same time,considering the uncertainty of chloride diffusion model parameters,the initial corrosion time of bridge pier reinforcement under different corrosion environments was obtained by Latin hypercube sampling simulation.(2)Referring to the manual accelerated deterioration dry-wet cycle test of high-damping rubber bearings conducted by the research group,the experimental data were processed and non-linear fitting was carried out,and a time-varying model of mechanical properties deterioration of high-damping rubber bearings under sea water dry-wet cycle was proposed.(3)The time-varying seismic capacity(including flexural capacity and ductility)of pier cross-section is studied,and the moment-curvature relationship of pier-column cross-section in the whole life cycle is obtained.In addition,according to the time-varying parameters of materials,the finite element model is updated to analyze and compare the time-varying law of bridge seismic response in service period under the condition that different components are deteriorated separately and jointly.At the same time,considering the possibility of occurrence of ultra-strong earthquakes,the time-varying law of seismic response of isolated bridges under E2 earthquake and rare earthquakes is analyzed.(4)Considering the uncertainties of bridge structure and seismic parameters,the central composite design method is used to design the test parameters.Sap2000 is used to carry out the non-linear time history analysis of the test,and the maximum response results of each component are obtained.Design-Expert software is used to carry out polynomial regression fitting of the test design and numerical simulation results,and the dual response surface model of bridge structure can be obtained.Variance analysis was carried out to verify the response surface model and the significance of each parameter.(5)Drawing two-dimensional response contour and three-dimensional response surface of each component by Design-Expert software.Visualization analysis was carried out to analyze the influence of the test parameters on the response value.Based on the double response surface model of bridge structure and given the damage index of each component,the vulnerability curve in the whole life cycle is obtained by Latin hypercube sampling simulation. |
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