Seismic fragility assessment of a multi-span cable-stayed bridge with tall piers

In this study, the longitudinal seismic fragility of a five-span cable-stayed bridge with tall piers is investigated using the fragility method. The OpenSees is applied to develop a finite element model of the cable-stayed bridge, and both the geometric and material nonlinearities are considered. A suite of 80 ground motions is selected to perform the nonlinear time history analysis, and the seismic responses of the expansion joint, deck, cables, and piers are discussed to determine the damage indexes of these components. Next, fragility curves are developed to assess the seismic performance of the cable-stayed bridge. The results show that the expansion joint, deck and cables are the vulnerable components, while the failure probability of the pier is relatively low. Moreover, the effects of the deck-pier connections and viscous fluid dampers on the vulnerability of the components and the bridge system are also studied. It is shown that the vulnerability of the cable and deck is sensitive to the deck-pier connections. Moreover, the deck-pier connection enhances the stiffness of the cable-stayed bridge. Therefore, it affects the seismic response of the cable-stayed bridge. However, the deck-pier connection has relatively slight effect on the system fragility. Furthermore, the location of the viscous fluid dampers significantly affects their effectiveness.