Seismic fragility assessment of RC highway bridges: The case of Moroccan bridge typologies

The post-earthquake functionality of transportation networks relies critically on the seismic resilience of bridges. This study presents an analytical approach to assess the seismic fragility of two bridge typologies within the Moroccan highway system: The Reinforced Concrete Girder Bridge (RCGB) and the Reinforced Concrete Slab Bridge (RCSB). To rigorously quantify their structural response, nonlinear static (pushover) analyses were performed to derive capacity spectra in both the longitudinal and transverse directions. The Capacity Spectrum Method (CSM), incorporating inelastic demand spectra, was then applied to evaluate structural performance points. Finally, the HAZUS methodology was utilized to generate analytical fragility curves for four discrete damage states (slight, moderate, extensive, and complete). The quantitative results demonstrate an exceptional degree of structural robustness for both configurations. The analytical models yield a nil probability of experiencing extensive or complete damage under the considered seismic demand. The probability of exceeding the slight damage state is remarkably low for the RCGB and practically negligible for the RCSB, with moderate damage potentials remaining statistically insignificant. Although the RCGB exhibits a marginally higher relative vulnerability, both typologies possess substantial structural capacities that guarantee uninterrupted post-earthquake serviceability and continuous traffic flow. This research contributes significantly to the advancement of performance-based earthquake engineering in Morocco, offering a rigorous quantitative foundation for regional risk mitigation and infrastructure management.