SEISMIC PERFORMANCE STUDY OF URBAN BRIDGES USING NON-LINEAR STATIC ANALYSIS
The structure remains within elastic range employing linear method and resulting forces and the displacement are quite high. By introducing ductility in bridges, the load carrying capacity can be enhanced thus bridge is to be designed for lesser forces than obtained in elastic range. This requires to employ non-linear analysis (in-elastic range). Pushover analysis is an effective tool to evaluate the expected non-linear behavior and consequent failure pattern in different components of the bridge. In the present study, typical short and medium span bridges structure like a mono-pier, bent beam-pier frame (typical flyover) with and without elastic-foundation in the urban area are considered. Nonlinear push over analysis procedure as recommended by ATC-40 is adopted under various seismic demands. The hinge formation for expected performance level is recorded, and compared for different boundary conditions in terms of different soil types using soil-structure interaction, ground acceleration input, and various values of ductility factors. The response parameters like base shear and roof (top) displacement for each case are studied. Evaluation of performance points for the given structure is considered (important parameter) as per capacity-demand methodology.