Influence of Structural Modeling on Seismic Vulnerability Assessment of a RC Viaduct using Fragility Curves

The fragility curve is a tool to estimate the probabilities that the structural damage exceeds specific damage state under various levels of seismic excitation. The main objective of this paper is to develop the fragility curves for a typical viaduct by analytical approach. In this study, a sample three span, two lane viaduct, situated in a highly seismic region in the country, is considered for development of fragility curve for seismic vulnerability assessment. Capacity of the bridge has been determined by static nonlinear analysis (Pushover analysis). The seismic demand parameters of the bridge were obtained by performing nonlinear time history analysis for different prescribed ground motion histories recorded in the past earthquakes. The fragility curves for the overbridge piers have been constructed assuming a lognormal distribution. The influence of modeling aspects of the viaduct structure on fragility curves has been investigated by considering two different structural models for the response analysis. It is observed that that the fragility curves are more sensitive to the structural modeling for higher damage level.