Study On The Damage Performance-Based Seismic Design Method For Long-Span RC Continuous Girder Bridges Of High-Speed Railway

ABSTRACT:At present, high-speed railway is developing rapidly. The seismic response characteristics of long-span RC continuous girder bridges of high-speed railway are obviously different from general simple supported girder bridges since the coupling effect of higher modes. Long-span RC continuous girder bridges of high-speed railway are also significantly different from RC continuous girder bridges of highway for its strong stiffness and support restraint. So the study on the seismic design method of long-span RC continuous girder bridges of high-speed railway is imperative. In this paper, the typical long-span prestressed RC continuous girder bridge in Chinese high-speed railway is taken as an example to carry out research of damage performance-based seismic design method for continuous bridges accounting for higher mode effects. The main research work in this paper is as follows:(1) A seismic design method is proposed according to the structure characteristics of long-span RC continuous girder bridges of high-speed railway based on the research of the present situation and existing deficiencies of the seismic design methods of domestic and foreign bridges. This design method takes the damage performance index as the design goal and includes a complete design process, and the higher mode effects are taken into consideration as well.(2) A certain60+100+60m long-span RC continuous girder bridge of Beijing-Shanghai high-speed railway is taken as an example to implement the seismic design method proposed and the specific results of the seismic design are presented. The finite element model of the bridge is built. The reliability of the proposed seismic design method is verified by the seismic performance test respectively from the perspective of strength index, deformation index, damage index and so on, through the strength checking under small earthquakes by response spectrum method and the checking under major earthquakes by nonlinear dynamic time-history method.(3) Further more, the rationality of the proposed seismic design method is proved through the comparison of seismic performance between design results and the actual example of bridge. The proposed seismic design method can provide reference for the seismic design of long-span RC continuous girder bridges of high-speed railway in high intensity seismic region.(4) The degree and regularity of the influence of the seismic design results produced by damage performance goal DI and stirrup ratio etc. are discussed emphatically. The rationality of the seismic design results under different conditions are verified through the nonlinear dynamic time-history analysis. Comparative study shows that the longitudinal reinforcement ratio of piers decreases with the increase of design value of DI under the same level of the ground motion. The longitudinal reinforcement ratio of piers decreases with the increase of stirrup ratio when the design value of DI is fixed. Although increasing stirrup ratio have little influence on the level of longitudinal reinforcement ratio of piers, the damage of piers will be reduced significantly.