Seismic Fragility of Multispan Simply Supported Steel Highway Bridges in New York State. II: Fragility Analysis, Fragility Curves, and Fragility Surfaces

Abstract

This paper presents the seismic fragility analysis of a typical multispan simply supported steel bridge in New York State. A detailed description of the bridge model including an analysis of parameter uncertainties was provided in the companion paper. The companion paper also describes a sensitivity analysis that was performed to determine the most critical parameters that control the seismic response of the bridge. A set of statistically independent bridge samples and earthquake samples were specified for the fragility analysis. Two alternative seismic retrofit designs were also presented in the companion paper. The results of the seismic fragility analysis performed in this paper based on the data assembled in the companion paper show that typical multispan simply supported steel bridges in New York State have more than 50% probability of exhibiting slight damage when subjected to earthquakes with peak ground accelerations (PGAs) of 0.51 g. A 50% probability of incurring moderate damage is observed for earthquakes with