Damage survey, simplified assessment, and advanced seismic analyses of two masonry churches after the 2012 Emilia earthquake

Recent Italian earthquakes (L’Aquila 2009, Emilia 2012, Central Italy 2016–2017) have shown the high vulnerability of existing and historical masonry constructions to seismic actions. This article investigates the damage distribution and the seismic response of two masonry churches located in the province of Ferrara (Northern Italy) and severely damaged by the 2012 Emilia earthquake. A proper knowledge of the geometry and structural details of the two churches was achieved through accurate on-site surveys and documentary research conducted after the earthquake. Moreover, field surveys provided detailed information about the crack patterns, highlighting the presence of significant damage in several parts of the churches. The seismic vulnerability assessment of the two churches was conducted on the basis of both the simplified approach given by Italian Guidelines on the Built Heritage and sophisticated nonlinear dynamic analyses performed on detailed finite element models assuming an elasto-plastic damage constitutive law for masonry. Limit analysis with pre-assigned failure mechanisms was carried out to preliminarily identify the most probable active failure mechanisms. Nonlinear dynamic analyses with different PGA levels allowed for a deep insight into the damage distribution in the churches: moreover, the energy density dissipated by tensile damage and the maximum normalized displacements were computed for the different macro-elements. A comparison between the numerical results and the damage observed during detailed field surveys was also provided. The results obtained in this study may represent a useful step to improve the knowledge of the seismic behavior of similar masonry churches located in the same region.