Seismic Assessment of Medium-Span Concrete Cable-Stayed Bridges Using the Component and System Fragility Functions

Abstract

Many studies have been conducted to investigate the seismic fragility of regular girder bridges, whereas only a few studies have focused on irregular cable-stayed bridges. In this study, the performance of a medium-span concrete cable-stayed (MSCCS) bridge is investigated by developing its component and system fragility functions. Structural analysis software is used to build the finite-element model of the case study bridge, and the ground-motion bin is assembled to match the practical site condition. The spectral acceleration at the geometric mean of the two periods of both longitudinal and transverse directions is applied to develop the component fragility functions. Analyses show that the bearings and transverse retainers are the most fragile components, whereas the failure probabilities of the concrete towers are relatively lower. This study proposes a user-friendly and efficient framework for establishing the system fragility functions on the basis of serial system assumption. Moreover, the fragility functions are applied to investigate a reasonable earthquake-resisting system for MSCCS bridges. The results show that the fragility functions are sensitive to the stiffness of the cable restrainer, and the longitudinal constraint system performs better than the total floating system and the total rigid system, especially when the stiffness of the cable restrainers is adjusted to a certain acceptable value.