Analysis of the collapse mechanisms of religious structures struck by the 2016 Italian earthquake

A major hazard during an earthquake is the overturning of slender and vulnerable walls, often made of stone masonry and weak mortar.Several medieval churches ruined during the 2016 Italian earthquake, while it has been noted that several ordinary retrofitted buildings only reported moderate or little damage. Researchers are studying these religious masonry structures with the aim of understanding their structural behaviour and at finding effective retrofitting solutions. Several causes can determine the collapse of these religious constructions: external factors, i.e. the failure of the nearby bell tower or adjacent structures, and, more often, the out-of-plane mechanism of the church’s side walls. In this paper it is demonstrated that the overturning mechanism of the facade is often facilitated by a lack or missing connection between the load-bearing walls. The collapse modes of two mediaeval churches, located in the small village of Campi, in the Nera’s valley, Italy, are investigated as case studies. The churches object of this study completely ruined during the 2016 Italian earthquake producing a significant loss in terms of architectural and art heritage. Between 2000 and 2004, a research team from the Technical University of Milan and the University of Padua in collaboration with the Italian Ministry of Culture carried out an extensive survey on the heritage constructions of Campi. This previous study provided additional information regarding the construction typologies, the building geometry, the construction rules and construction materials, also providing interesting data about the maintenance level. Although all these information provided a summary of the structural state of the churches, no interventions aimed to reduce the seismically vulnerability were adopted at that time.