The Sanctuary of Santa Maria delle Grazie at Fornò: studies for the restoration and seismic strengthening.

The Sanctuary of “Santa Maria delle Grazie” is located at Fornò in the countryside near Forlì (Italy). The first temple, built in 1450, assumes today's configuration at the beginning of the sixteenth century, to undergo various modifications, due to static necessities and to changes in tastes related to the time, as well as due natural disasters and war damage. Structurally, the Sanctuary consists of an external masonry cylinder, around 33m diameter and 15m in height, with four semicircular niches protruding outwardly; inside there is a similar concentric structure, the oldest temple, about 14m diameter and 20m tall, covered by a dome supported by an octagonal masonry structure. The space between the two circular structures is covered with a wooden roof resting on thirty-six main wooden beams. In the last years the Sanctuary has been subjected to numerous studies, surveys and analysis, including FEM structural analysis (also due to singular curvilinear typology of the masonry structures). In regard to the seismic risk, the building was studied focusing on the Guidelines (2011) for the "Evaluation and Reduction of Seismic Risk of Cultural Heritage.". Today, following the entry into force of the new technical standards NTC2018 (January 2018) we have scheduled an update of the structural analysis and a series of proposals for restoration, anti-seismic improvement and dehumidification works, in regard to the effects of decay caused by soaking on the mechanical characteristics of the masonry.