Advanced numerical insight into the structural damage of masonry vaults under seismic excitation: Two valuable case studies

Historical buildings are essential expressions of the artistic and cultural heritage of a country and thus, their preservation becomes of primary importance, especially in regions frequently affected by seismic events. Most recent earthquakes have once again demonstrated the high seismic vulnerability of monumental masonry buildings and, specifically, critical issues associated with complex structural elements like vaults. In this framework, the main purpose of this paper is the analysis of how quadripartite vaults behave under horizontal loads and what their role is in the global seismic behaviour of historical constructions. As a matter of fact, the study of vaults subjected just to gravitational loads is very difficult by itself. Consequently, it is by far harder to define how they behave with respect to lateral forces and, secondly, how they influence the global response of a structural system. The analysis of the effects of vaults is afterward dealt with by referring to two different case studies: the Narthex of the Nativity Church in Palestine, one of the most ancient examples of basilica structures listed as a world heritage site by UNESCO and Torre Fornasini, a squat defensive tower near Poggio Renatico, N-E Italy and severely damaged by the recent 2012 Emilia Romagna (Italy) seismic event. By means of the software ABAQUS, a proper finite elements model is implemented in order to assess the global structural behaviour of the structures, evaluating the seismic behaviour directly thorough non-linear dynamic analyses, discussing the obtained crack patterns, with particular attention to the vaulted systems. For all masonry structural members, a Concrete Damage Plasticity (CDP) constitutive model is used to properly account for damage phenomena and softening occurring on masonry during an earthquake.