Seismic Fragility Relationships of a Cable-Stayed Bridge Equipped with Response Modification Systems

This paper presents the development of fragility curves of a benchmark cable-stayed bridge retrofitted with response modification systems. Fragility relationships are an accepted technique used for seismic risk assessment of structures. The example used herein is a benchmark cable-stayed bridge. Synthetic ground motions are used to excite the structure. Semiactive control is applied to the structure to evaluate and quantify its impact on response mitigation. The semiactive devices used herein are magnetorheological (MR) dampers. The performance of the structure retrofitted with MR dampers is compared with the structure retrofitted with passive, active, and no devices. Fragility relationships based on deck displacement, deck shear, and overturning moment are investigated for comparison. Analyses of peak and time history responses are used to support the accuracy of the fragility relationships. An investigation of the cables exceeding an appropriate tension range and control effort required for the control cases is also provided. The resulting fragility relationships show that MR dampers are effective at mitigating the effects of seismic excitation on the cable-stayed bridge.