Modeling and Design of the Restoration and Seismic Strengthening of the Sanctuary of Santa Maria Delle Grazie at Fornò under New Italian Rules NTC 2018

Abstract

The Sanctuary of “Santa Maria delle Grazie” at Fornò is in the countryside near Forlì (Italy). The first edification time was in 1450, the today's configuration was reached at the beginning of the sixteenth century, due to various modifications: from static necessities to changes in tastes related to the time, as well as natural disasters and war damage. From a structural point of view, the Sanctuary is constituted by two masonry cylinders, without horizontal floors in elevation: the exterior cylinder around 33m diameter and 15m in height, with four semicircular niches protruding outwardly; the interior cylinder, 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. In the latest studies we have assumed the Guidelines (2011) for the "Evaluation and Reduction of Seismic Risk of Cultural Heritage.". In the present work, following the entry into force of the new Italian rules NTC2018 and, more recently (February 2019), of the Explanatory Circular, which among other topics introduced significant changes in the field of existing buildings and in particular in the non-linear analysis mode, we have made a new update of the structural analysis and designed a series of works for restoration and anti-seismic improvement (also dehumidification works to mitigating the effects of decay caused by soaking on the mechanical characteristics of the masonry).