Fragility Assessment for Seismically Retrofitted Skewed Reinforced Concrete Box Girder Bridges

Abstract

Skewed bridges are susceptible to seismic damage due to their complicated dynamic responses. A range of potential retrofit strategies have been implemented to mitigate damages in seismically deficient bridges. However, because the seismic responses of skewed bridges often differ from straight bridges, and the efficiency of each retrofit measure may vary from one class to another, a comprehensive study with a wide range of retrofit options among skewed bridges is needed. This paper assesses the impacts of 10 different retrofit strategies on the fragility of skewed single-frame concrete box girder bridges with seat-type abutments in two common subclasses termed single- and two-column bent. Fragility curves corresponding to four damage states at both the component and system levels are developed for various skew angles. The results show that, although no single retrofit measure can solely contribute to decreasing all component and system vulnerabilities in highly skewed bridges, combinations of retrofit measures can be used to enhance the desirable level of skewed bridge performance. The level of effectiveness of a retrofit option is highly dependent on bridge class and skew angle.