Abstract
This study examines the seismic fragility of cable‑stayed bridges using an integrated probabilistic framework that explicitly incorporates spatial variability of ground motion, soil liquefaction, and nonlinear cable behavior. A detailed numerical model of the seven‑span, 730 m Suez Canal Bridge is developed in OpenSees and analyzed through nonlinear incremental dynamic analysis using twenty recorded bedrock ground motions from the PEER database. Spatial variability is represented through apparent seismic wave velocities of 100, 430, and 1000 m/s and benchmarked against uniform excitation to quantify wave‑passage effects. Soil profiles corresponding to dense sand, dry loose sand, and saturated loose sand are considered, with liquefaction simulated through a thin soft interlayer. A slackening‑based fragility methodology is introduced, evaluating cable vulnerability through loss of pretension rather than conventional yield‑strain criteria. Fragility functions are developed for elastomeric bearings, expansion joints, tower drift, section curvature, and cable yielding and slackening across four damage states using peak ground velocity as the intensity measure. Results indicate that spatial variability induces mixed, mechanism‑dependent effects: wave passage reduces displacement‑controlled fragility in bearings and expansion joints by desynchronizing support motions, whereas higher apparent wave velocities create more coherent support movement that increases curvature demands in towers and piers. For stay cables, spatial variability induces phase‑lag motions that trigger earlier and stronger slackening. Liquefaction further amplifies fragility for bearings, joints, and piers through soil softening and increases slackening susceptibility without significantly affecting cable yield strain. These findings highlight the importance of considering wave propagation, soil softening, and pretension loss in fragility assessments.