Impact of natural hazards on buildings: the case of rockfalls against masonry structures

Rockfalls are gravitative natural phenomena involving large kinetic energies. The falling rock blocks, which volume span from few cm3 to several m3, can reach speeds up to 30 m/s. Once interacting with buildings and infrastructures, rockfalls can cause damages and fatalities. The vulnerability of the system depends on the magnitude of the phenomenon and the properties of the impacted structure, in terms of material, arrangement of the resisting elements and geometry. The present contribution reports an experimental and numerical analysis of the effects of rockfall on stone masonry structures, which represent the vernacular construction typology in Alpine areas. The numerical FEM analysis consisted in a set of impact simulations of front walls subjected to different boundary conditions to account for the number of stories and floor orientation. The simulations were performed considering a contact stiffness between the block and the masonry that results from an impact experimental campaign. For each numerically simulated scenario, collapse vs. non collapse final configuration is assessed with the scope of quantifying the degree of loss on the single element. Different local damage scenarios emerge depending on the geometrical properties of the impacted wall.