An Interdisciplinary Approach for the Geometric, Constructive, and Structural Assessment of Historical Masonry Domes with Application to the 'Badia di Sant'Agata' in Catania, Sicily

Masonry domes have always represented one of the most fascinating and daring architectural structures, with great symbolic relevance. However, their structural behaviour under environmental actions, such as earthquakes, has not yet been thoroughly investigated. This paper defines an interdisciplinary methodological approach, based on advanced digital survey techniques to evaluate constructive, geometrical, and structural aspects of historical domes. The applied procedure comprises the study of archival documents and diagnostic reports, in-situ analyses and advanced three-dimensional surveys, the development of simplified discrete-element-based structural models, and the performing of pushover analyses. The procedure is applied to a case study represented by the dome of the 'Badia di Sant'Agata' church in Catania, an earthquake-prone town located in Eastern Sicily. This church was built after the devastating 1693 earthquake and its dome represents one of the most significant examples among hundreds of masonry domes built in Sicily. The historical and constructive investigation showed that the dome was built without supporting formworks, by laying 21 concentric courses of limestone voussoirs on a peculiar springing ring made of mortared rubble stones. The numerical simulations highlighted that this peculiar ring affects the dome's failure mechanism and limits its displacement capacity and the maximum shear transferred to the substructure.