During natural disasters, such as earthquakes followed by tsunamis events, bridges represent critical infrastructures whose failure can severely hinder emergency response and recovery efforts. Coastal regions are among the most susceptible to facing these unfortunate occurrences and it is also well established that even Mediterranean areas have experienced significant events of combined earthquake-tsunami actions. The 1908 Messina tsunami, triggered by a powerful earthquake, devastated southern Italy, causing many facilities and remaining in the memory of Mediterranean regions’ inhabitants.

The focus of this research is to provide insights useful for more resilient infrastructure design standards for multi-hazard scenarios and effective mitigation measures. A probabilistic multi-hazard fragility assessment framework is presented to evaluate the structural vulnerability of bridges subjected to sequential earthquake and tsunami loads, since a significant increase in vulnerability occurs when seismic damage precedes tsunami loading, underscoring the need for integrated design and assessment strategies.

The proposed methodology employs Monte Carlo simulations to account for uncertainties in tsunami forces, structural configurations, and material properties, providing a statistically tool for vulnerability assessment. Representative bridge typologies from Mediterranean coastal zones are analyzed through a two-step process: nonlinear time-history analyses simulate seismic action, then force-controlled pushover analyses model tsunami impact. This sequential approach captures the cumulative effects of damage and degradation in structural capacity.

The simulation results have been examined to identify the most appropriate analytical lognormal distributions capable of accurately representing structural fragility. A comprehensive comparison between the numerical results and the derived fragility functions has been conducted, confirming the effectiveness of the proposed methodology.