The Effect of In-Span Hinges and Span Numbers on the Seismic Vulnerability of Curved Box-Girder Highway Bridges Considering Material and Geometric Uncertainties

Abstract

Around 15% of seismically designed Californian box-girder bridges incorporate at least one in-span hinge. This class of bridges can be further divided into two subclasses (i.e., single-frame and multiframe subclasses) according to the number of bridge spans in each bay of the bridge. The number of spans has a considerable influence on the dynamic response of box-girder bridges and, accordingly, on their seismic vulnerability. In this study, 420 analytical models for horizontally curved and straight highway bridges are developed using finite element OpenSEES software, considering geometric and mechanical uncertainties. Effects of in-span hinges, the number of spans, and the radius of the deck curvature on the seismic fragility of seismically designed concrete box-girder bridges with integral multicolumn bents and seat type abutments are investigated. Nonlinear time history analyses (NTHAs) are utilized to develop the fragility models for the bridge components and corresponding systems. Results show that the presence of in-span hinges and the number of spans have a considerable influence on the seismic vulnerability of box-girder bridges (for example, the median fragility of the straight bridges decreases by 26% when single-frame bridges change to multiframe at the moderate damage state). However, these effects can be quite variable for different deck radius at different damage states of the corresponding fragility functions.