Seismic Retrofit Analysis of Urban Grade Separation Bridge --Application of Capacity/Demand Analysis Method

Application of C/D analysis method to seismic evaluation and retrofit of urban grade Separation Bridge were discussed herein. Firstly, based on previous earthquake damage, the weak elements of urban grade separation bridges were concluded in this paper. Secondly, main process of C/D analysis method and the way of getting capability indexes were discussed . Thirdly, taking an urban grade separation bridge as example, C/D analysis for shear capacities and flexural capacities of piers, and deformation capacities of bearings under common earthquake(E1) were done. After that, C/D analysis for deformation capacities of piers under rare earthquake(E2) were discussed also. Analysis showed that under E1 earthquake the shear capacities and flexural capacities of fixed piers were insufficient; under E2 earthquake the deformation capacities of piers were insufficient. Finally, a seismic retrofit plan was given in this paper. After retrofit, although the seismic demands of critical elements were increased, the C/D ratios of them were all reduced below 1.0. So the risks of earthquake damage were reduced effectively.