Study On Vulnerability Of Bridge Structure Based On Seismic Intensity

The damage of bridge structure caused by earthquake has been widely concerned in the field of international seismic resistance.To deeply understand the damage degree and characteristics of various bridge structures in earthquake,it has become a research hotspot in the international bridge seismic field to explore the seismic vulnerability of the bridge structure based on the empirical seismic damage observation data.Due to the multiple regional intensity scales in the world,the assessment of bridge structural vulnerability grade is different,and the bridge structure damage is often affected by multi factor coupling.It is difficult to realize the overall grasp of the entire areas and a certain type of bridge structure damage to analyze the vulnerability of single bridge structure in a seismic region.In this dissertation,the seismic damage of typical bridge structure is analyzed,and the investigation data of bridge structure in typical earthquake are collected and sorted out.The vulnerability grade of bridge structure is evaluated by using different intensity scales and lifeline engineering specifications,and the seismic damage vulnerability matrix model of bridge is established,and its intensity grade is evaluated;Based on the numerical value,probability model and functional theory,the nonlinear fitting model method of vulnerability(nonlinear regression model and matrix probability model method)is proposed,and the nonlinear model of typical bridge structure is established,and the reliability analysis of these models is carried out based on the measured data;Combined with the typical intensity scale,the vulnerability analysis of RC girder bridge is carried out with failure ratio and exceeding probability as the vulnerability evaluation parameters,and the vulnerability matrix models based on the typical intensity scales are obtained respectively;Based on the vulnerability model,based on the empirical seismic damage data of 22 highway sections in Wenchuan earthquake,the model is verified,and the empirical seismic damage vulnerability function,matrix and curve model of group bridge structure in each section are developed.The specific research work of this dissertation is as follows:1.The seismic damage of RC girder bridge and masonry arch bridge(Wugong arch bridge)is investigated and analyzed.Taking Wenchuan earthquake investigation data as an example,the damage characteristics of two kinds of bridges are analyzed.From the material point of view,the similarities and differences of seismic damage between RC girder bridge and building,masonry arch bridge and masonry building are compared and analyzed.Based on the results of comparative analysis,opinions and suggestions for improving the seismic performance of RC girder bridge and masonry arch bridge are put forward.2.Classifies and compares the provisions in EMS-98,MSK-81,MMI-56,JMA-96,CSIS-08 and CSIS-57 scales which can be developed to assess the vulnerability of bridge structures and different intensity grades,taking 105 typical damaged bridges in 10 highway sections of Wenchuan earthquake as an example,the vulnerability grade of bridges is evaluated one by one by using typical intensity scale,and the evaluation data are statistically analyzed,and the vulnerability and intensity grade matrix of typical groups of bridges under different intensity scales are obtained.3.The calculation method of nonlinear fitting model for empirical seismic damage vulnerability is proposed,and a group of typical bridge structural vulnerability nonlinear models are established,and 1516 girder bridges and 612 arch bridges are evaluated and counted by using EMS-98,MSK-81 and CSIS-08 scales respectively,taking the number and failure ratio as parameters,the vulnerability matrix model is established,and the reliability analysis of the nonlinear vulnerability model is carried out,and the bridge vulnerability regression function and nonlinear curve model are obtained.4.Taking the failure ratio and exceeding probability as the vulnerability parameters of RC simple supported girder and continuous girder bridge,the vulnerability grade distribution,parameter matrix and curve model of two kinds of girder bridge under,EMS-98,MSK-81 and CSIS-08 scales are obtained respectively.The calculation method of mean seismic damage index matrix model based on failure ratio model is proposed.The mean seismic damage index matrix model of RC girder bridge and its simply supported and continuous girder bridges in different intensity regions are obtained based on EMS-98,MSK-81 and CSIS-08 scales.Employing 1069 typical RC girder bridges and 949 RC buildings in Wenchuan earthquake as samples,combined with the vulnerability assessment criteria of EMS-98,MSK-81 and CSIS-08,the vulnerability models of RC girder bridges and buildings based on failure ratio and exceeding probability are calculated and obtained,and the comparative analysis is developed.According to the analysis results,the measures and methods to improve the seismic capacity of RC girder bridges are proposed.5.The seismic damage field observation data of 2134 group bridges of 22 highway sections(47 sub sections)in Wenchuan earthquake are collected and sorted out.Combined with CSIS-08 scale and relevant nonlinear vulnerability model,the vulnerability of groups of bridges in each highway section is analyzed,and the seismic damage vulnerability matrix,function and curve model of each section based on the sample bulk of group bridges are established.The probability and curve model of group bridge vulnerability matrix of each highway section are established considering the failure ratio and exceeding probability parameters respectively,which verifies the engineering reliability of the vulnerability model.