Seismic Fragility Assessment of Cable-Stayed Bridges Crossing Fault Rupture Zones

Abstract

Current studies lack probabilistic evaluations on the performance of fault-crossing bridges. This paper conducts seismic fragility analyses to evaluate the fragility of cable-stayed bridges with the effects of fault ruptures. Synthetic across-fault ground motions are generated using existing simulation methods for the low-frequency pulses and high-frequency residuals. Incremental dynamic analysis is utilized to generate the seismic responses of the bridge. The optimal intensity measure (IM) for a cable-stayed bridge that crosses a fault is identified based on the coefficient of determination (R2). Root-mean-square velocity (Vrms) is found to be the best IM for cable-stayed bridges traversed by fault ruptures, instead of the commonly used ones such as peak ground acceleration or velocity (PGA or PGV). Fragility curves for the critical components of fault-crossing cable-stayed bridges, including pylons, cables, and bearings, are developed using the IM of Vrms, and are subsequently compared with those for the cable-stayed bridge near faults. Results show that the bearings on transition piers are the most vulnerable component for fault-crossing cable-stayed bridges because of the rotation of their girder. Compared to cable-stayed bridges near faults, pylons and bearings are more vulnerable in the transverse direction for cable-stayed bridges crossing faults, whereas the vulnerability of cables is comparable.

Evaluating the identification methods of permanent displacement derived from strong motion records: Case studies in the 2023 Turkey–Syria earthquake

“…2 Therefore, near-fault displacement has attracted growing attention in the fields of ground motion simulation and risk analysis, as well as in the design of structures susceptible to cross-fault effects. [3][4][5] However, the mechanisms and processes that produce the velocity pulse remain elusive. 6 Pulse-like ground motion is typically attributed to the directivity effect.…”

“…A notable feature of near‐fault ground motion is the velocity pulse or permanent displacement for large‐magnitude earthquakes, which can pose severe damage to long‐period structures 2 . Therefore, near‐fault displacement has attracted growing attention in the fields of ground motion simulation and risk analysis, as well as in the design of structures susceptible to cross‐fault effects 3–5 . However, the mechanisms and processes that produce the velocity pulse remain elusive 6 .…”