L’abside in facciata: soluzioni “antisismiche” del XVIII secolo in Sicilia

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In the course of the 18th century, church facades with curvilinear shapes were designed and built in Sicily.Convex and concave shapes, positioned in the central portion of the facade, made these structures similar to apses. Choices of an esthetic nature initially triggeredemulation of models that spread in the second half of the 17th century in Sicily based on engravings reproducing the inflexed facades created by the masters ofRoman Baroque. So far, interest in these models appeared to be the most relevant interpretation in explaining the design trends of the major architectsoperating in the 18th century in Sicily. However, it seems plausible to surmise that the preference for the curved facades derived, in some specific cases, from areflection focused on the strength of these structures especially if subjected to the action of earthquakes, which were violent and frequent in the island from theMiddle Ages and throughout the Modern period. The aim of this study is to demonstrate the static efficiency of facades with a curvilinear shape, which was probablyrecognized by designers as being among the factors that contributed to determining the stability of buildings.We will seek to understand whether behind the esthetic and formal reasons there was also a debate focused on the structural advantages offered by this typeof façade, thus influencing the design of the reconstruction projects. In this context, Giovanni Amico, Giovanbattista Vaccarini, and Rosario Gagliardi imposedfacades with a concave-convex pattern on Sicilian construction sites in the 18th century, an interest that was shared by the three Sicilian architects, as demonstratedby archival sources. Obviously, Sicilian architects of the early 18th century were well aware of the extraordinary fact that some apses (like the Norman apses of theCathedral in Catania) had survived unscathed more or less catastrophic earthquakes that hit Sicily in the Modern period (1542, 1693 and 1726). The observation ofthese structures still standing against a backdrop of rubble in the aftermath of the earthquake had an impact on those who were to design new monumental andlasting edifices in an area at risk of earthquakes. The documents discovered and the constructions realized in Sicily prove that the assumption, never actually codified,according to which the architectural form was able to cooperate actively in seismic safety was a part of the body of building knowledge shared by generationsof architects and masters of the Modern period who worked throughout the island. Some eyewitnesses of earthquakes realized that history had an essential “functional” role and that the surviving works were an invaluable heritage, related to both the technical and formal aspects of the constructions, to be recovered and optimized for anti-seismic purposes in future works. Sicilian architects and master builders of the 18th century knew the concept of the so-called "crossbow" effect, which is namely the rotary force exerted on facades by the multiplication of the thrusts of internallongitudinal arches, amplified during earthquakes, making them overturn and collapse, as shown by the famous document that rejected the plan for the newfacade of the Cathedral of Modica (1761). Likewise this effect however was of interest for the apses built on the opposite side of the facades. They were structures that, as mentioned, were sometimes left unscathedthanks to their particular curvilinear geometry. Many Sicilian apse-shaped facades of the 18th century were built on pre-existing edifices that had been hit by anearthquake to a
Lingua originaleItalian
Numero di pagine15
Stato di pubblicazionePublished - 2015

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