Analysis Of Seismic Time-varying Vulnerability Of Concrete Bridges Under Marine Environment In Cold Area

In this paper,the concrete bridge under marine environment in cold area is taken as the research object.Based on the degradation model and experimental research results of the existing concrete structure suffering from freeze-thaw damage and steel corrosion,the seismic performance of the concrete bridge in the cold area marine environment is studied.The main contents are as follows:(1)Based on the existing deterioration models of concrete structures subjected to freezethaw damage and corrosion of steel bars and the induction and analysis of experimental theoretical research,the deterioration models of concrete structures subjected to freeze-thaw damage and corrosion of steel bars suitable for this analysis are determined.(2)Through the induction and analysis of the research results of the seismic theory of the deteriorated concrete bridge,the seismic analysis method applicable to the concrete bridge is determined,that is,the IDA(incremental dynamic analysis)method is used for the seismic response analysis of the bridge system,and the structural seismic resistance index analysis method is determined to construct the theoretical vulnerability curve of the structure;at the same time,based on the natural seismic database,the selection of the seismic analysis method is made A suitable number of seismic waves.(3)According to the structural characteristics of the degraded concrete bridge,through the finite element modeling analysis,the element types,constitutive relations and boundary conditions involved in the modeling process are studied,and the applicable finite element software is determined;the real bridge finite element model is established by using OPENSEES software,and the material degradation model is applied to the real bridge pier model,taking into account the concrete freeze-thaw and reinforcement respectively The adverse effect of corrosion on piers.(4)Based on the theory and method of structural vulnerability analysis,taking the finite element model of a real bridge as the object,the nonlinear time history analysis of the structure is carried out by inputting the selected seismic wave respectively,and the structural seismic demand model changes with the service time is obtained;the vulnerable components of a continuous beam bridge under the earthquake action-piers and supports are selected,and the corresponding resistance index and damage state are determined,and the bridge is obtained Based on the seismic demand and seismic capacity model of the bridge,the time-varying damage model of the example bridge is established.The results show that: With the increase of service time,the critical curvatures of concrete piers in various damaged states decrease obviously,and the degradation of piers has a greater impact on the critical curvatures in severe and complete damaged states;with the increase of service time,the exceedance probability of slight and medium damage states of concrete piers increases slightly,while the exceedance probability of severe and complete damage states decreases slightly The deterioration of material properties of concrete piers changes the relative relationship of vulnerability of bridge components.It can provide reference for seismic evaluation and operation maintenance of similar bridges.