Seismic vulnerability of ancient stone arches by using a numerical model based on the Non-Smooth Contact Dynamics method

Abstract

The dynamics of two Roman stone arches has been studied by means of the Non-Smooth Contact Dynamics method (NSCD), implementing a discrete element numerical model in the LMGC90 code. Schematized as a system of rigid blocks, undergoing frictional sliding and plastic impacts, the arches have exhibited a complex dynamics, because of the geometrical non-linearity and the non-smooth nature of the contact laws.First, harmonic oscillations have been applied to the basement of the arches, and a systematic parametric study has been conducted, aimed at correlating the system vulnerability to the values of amplitude and frequency of the assigned excitation. In addition, numerical analyses have been done to highlight the effects of the friction coefficient and of the blocks geometry on the dynamics, and, in particular, on the collapse modes. Then, the study of the arches stability against seismic excitations has been addressed, and three-dimensional simulations have been performed. Attention has been payed to the occurrence of out-of-plane overturning mechanisms induced by possible bending of the arches.The numerical results have suggested some structural retrofitting actions needed to improve the arches seismic safety.