Air fall deposits due to explosive eruptions: Action model and robustness assessment of the Vesuvian roofs

During an explosive eruption, a construction is hit by several actions, which are associated to elevated temperatures causing fires, possible explosions and reduction of the mechanical properties of the structural materials. In this paper, the attention is focused on the analysis of a specific volcanic event constituted by the pyroclastic deposits, falling on the roofs due to gravity, the so-called air fall deposits. The study faces two important aspects. The first one concerns the proposal of a model of the action on the basis of a similitude between the air fall deposits and the snow load. The second item is the robustness evaluation against the air fall deposits of the most common roof types in the Vesuvian area, which are made of timber, steel and reinforced concrete. Consequently, some mitigation systems have been identified.