A mechanics-based procedure for the structural assessment of infilled RC buildings under overpressures generated by pyroclastic density currents

The recent seismic activity of the Phlegrean Fields has drawn attention to the potential impact of volcanic eruptions in densely urbanized areas. Among the volcanic processes, the formation of pyroclastic density currents (PDCs) poses a significant threat to residential buildings because of the large dynamic overpressures generated during the explosion. This study introduces a simple mechanics-based method, called STAM-PYR (STructural Assessment Method for PYRoclastic density currents), for the structural assessment of infilled reinforced concrete buildings subjected to PDCs. The STAM-PYR method allows to predict damage evolution as a function of dynamic overpressure intensity, accounting for the contribution of both structural and nonstructural components as well as typical failure modes that can develop in existing RC buildings. Furthermore, it accounts for the variation in the overpressure profile by dynamically updating the load distribution depending on the progressive failure of infill panels and closures. A suitable damage scale is also introduced to facilitate future multi-risk comparisons. The method is exemplified via application to a case study of a typical 1970s RC building, comparing the results to existing literature to demonstrate the enhanced accuracy of the proposed approach in capturing the complex interactions between PDC loadings and building response. STAM-PYR offers a practical and scalable tool to support probabilistic volcanic risk modeling, vulnerability mapping, and emergency planning, especially in urban areas at high risk of explosive eruptions. By enabling a more accurate quantification of structural vulnerability to PDCs, the methodology enhances current capabilities in disaster mitigation, crisis management, and long-term risk-informed land-use strategies.