Fragility Analysis of Cable‐Stayed Bridges: Assessing Seismic Vulnerability and Structural Integrity Loss

ABSTRACT This study investigates the impact of progressive cable loss on the seismic performance of cable‐stayed bridges using fragility curve analysis under multi‐component earthquake excitations. A detailed finite element model of the Bill Emerson Memorial Bridge was developed using OpenSees and validated against existing experimental data. Fragility curves were then generated for scenarios involving the sequential failure of one to four cables under seven selected ground motion records. The fragility analysis focused on the pylons, the most critical structural components of cable‐stayed bridges. Following the calculation of the ductility and behavior factor of the pylon, four seismic limit states were defined, and the failure probability of bridge was computed based on the regional seismicity. The results demonstrate that cable‐stayed bridges have high seismic capacity and resilience; failure of up to three sequential cables does not significantly increase the probability of total collapse compared to the normal condition. However, the loss of four cables leads to a near‐unity failure probability at low intensity levels, indicating a complete loss of structural integrity.