Framework to Evaluate Seismic Fragility of Bridges Considering Component Damage Correlations

The objective of this study is to propose a framework for evaluating the seismic fragility of bridge systems analytically taking into account correlations between component behaviors. To include coupled effects of component behaviors on system behavior, the second-order reliability approach is adopted. The damage states of the combined fragility are proposed based on system behavior characteristics obtained by pushover analyses. The characteristics of the combined fragility information of two bridge models are illustrated using probabilistic seismic demand analysis based on the time history analysis results from several earthquake excitations. The fragility curves obtained from the second-order reliability model are compared with the first-order reliability model. It is shown that the proposed framework can provide more detailed fragility information rather than only providing bounds of system fragility as in the first-order reliability-based approach.