Seismic Vulnerability And Risk Assessment Research Of Railway Simply Supported Girder Bridge For Sichuan-Tibet

A wide geographical region is spanned by Sichuan-Tibet railway. It goes through multiple seismic zones which are severely affected by the earthquakes.42.5% of the distance between the start and finish point is covered by bridges and tunnels, and the majority of bridges are simply supported girder bridges. Therefore, it is of great significance to conduct the seismic vulnerability analysis and the seismic risk assessment of the simply supported girder bridges of Sichuan-Tibet railway. With records recorded from the Wenchuan Earthquake as the input ground motion, aiming at the simply supported girder bridges, the nonlinear dynamic time history analysis has been done on Sichuan-Tibet railway. The dynamic response of the bearing and pier components of simply supported girder bridges are recorded, and then the probabilistic seismic demand analysis is conducted. Based on the analysis, the seismic vulnerability curves of the simply supported girder bridges of Sichuan-Tibet railway are established. The hazard analysis for the simple supported girder bridges of Sichuan-Tibet railway is conducted in this thesis. Bases on the results of the seismic hazard and the seismic vulnerability analysis, the seismic risk curves are established and then these are used to assess the seismic danger. The main contents and the conclusion of this thesis can be summarized as follows:1. The introduction to the seismic vulnerability analysis, seismic hazard analysis, seismic risk assessment theory and method have been provided, meanwhile, the existing problems in the research of seismic vulnerability are pointed out.2. Based on the traditional seismic vulnerability analysis, a more suitable basic process of seismic vulnerability analysis of simply supported girder bridges of Sichuan-Tibet railway is established. A detailed discussion on the sample library of the ground motion-bridge structure and the damage index of the simply supported girder bridges is provided in this thesis and then displacement ductility ratio, maximum displacement are selected as the damage index to carry on the seismic vulnerability analysis of the simply supported girder bridges.3. A detailed introduction into the categorization of the seismic, the selecting principle of seismic has been provided in this thesis and then the records recorded from the Wenchuan Earthquake are chose as the input ground motion to do the seismic vulnerability analysis of the simply supported girder bridges.4. Based on the "Cloud-method", different categories of seismic demand models for Sichuan-Tibet railway’s simply supported girder bridge components are built and then proper evaluation criteria are established. By comparing seismic demand models, the double exponential function model is concluded to be the most suitable seismic demand model for simply supported girder bridges of Sichuan-Tibet railway in the seismic vulnerability analysis.5. The seismic vulnerability curves of simply supported girder bridges at various heights are established and then a comparative study is subsequently conducted, which analyses how the vulnerability factors vary depending on the height of the bridge.6. On the basis of the seismic vulnerability and hazard analysis of simply supported girder bridges of Sichuan-Tibet highway railway, the seismic risk curves are established, and then the seismic risk analysis is conducted.