Earthquake-tsunami combined fragility curves for coastal masonry buildings: a numerical-analytical approach

Abstract The vulnerability of coastal buildings to tsunami events has garnered increasing attention in the last decades due to the severe impacts of recent disasters. Numerous challenges have been addressed to develop valuable methodologies to estimate the probability of damage to structures and infrastructures and to formulate effective strategies to mitigate potential damages and losses. However, a comprehensive predictive framework for constructing damage probability models applicable across different structural types and tsunami scenarios, while also accounting for the potential impact of previous earthquake damage, is still missing. In the present study, a double-stage approach for investigating the vulnerability of masonry buildings under sequential earthquake-tsunami events is proposed and discussed. Monte Carlo simulations are performed, analyzing the response of different building classes, characterized by different numbers of storeys. The random generation of the involved and basic parameters characterizing structures and loads have been followed by time-history dynamic analyses for seismic actions and push-over analyses for tsunami loading. The results provide valuable insights for refining multi-risk evaluations, highlighting the impact of earthquake-induced damage on tsunami vulnerability compared with studies that neglect seismic effects. In the paper, the influence of previous random seismic action on tsunami loading vulnerability was obtained and translated into a new type of fragility curve for the earthquake-tsunami interaction. Meanwhile, the important effect of building height on tsunami vulnerability is stressed along with the influence of vertical loads and seismic intensity, expressed in terms of Peak Ground Acceleration (PGA). Comparative analyses were conducted to assess the effectiveness of the proposed methodology for constructing analytical fragility curves, evidencing the reliability of the proposed approach.