Dynamic response of a volcanic shelter subjected to ballistic impacts

This paper presents the results of a series of experimental tests, aimed at investigating the impact and dynamic response of a volcanic shelter. Similar shelters are to be installed in the Stromboli island (Aeolian archipelago, Sicily, Italy), to protect human lives from the pyroclastic eruptions of the volcano. Basically, the Shelter consists of two homologous reinforced concrete shells, interconnected by rubber-based special devices, which absorb and dissipate most of the impact energy. The Shelter has been specifically designed to resist, without damage, an impact with a 150 kg mass rock, knocking the surface of the external shell at 62.5 m/s speed.The experimental tests were carried out on a 1:2-scale model, using a testing apparatus purposely realised to simulate impact conditions comparable with those considered in the design. Impact energy and mass ratio between projectile and reinforced concrete shell were assumed as main experimental parameters and varied during the tests. A finite element model of the Shelter was also implemented and direct-integration time-history analyses were performed, to validate the experimental results. Reference to the Hertz's law was made to simulate the impact between the two bodies.The experimental tests proved the ability of the Shelter to resist impacts without damage. Acceptable agreement between numerical predictions and experimental results was found.