The static model in Bernardo Antonio Vittone architecture: The Santa Chiara and San Leonardo churches in Turin

Abstract

The study aims to analyse the two static models most widely adopted by Bernardo Antonio Vittone, through the comparison of two churches in Turin: Santa Chiara and San Leonardo. They are double envelope buildings, with central dome, respectively 10 and 15 meters in diameter, supported by eight pillars and surrounded by a continuous ambulatory. The static model of Santa Chiara provides the internal pillars that play the main structural role and cooperative outer envelope: the dome transmits his loads directly to the interior pillars. The walls and vaults of the lateral chapels have an important role, arranging themselves around the main dome, like a ring of containment of the horizontal thrusts induced by the dome itself. Also the choirs, that Vittone places in smaller spaces behind the pillars, play an important static role: their horizontal structures connect the pillars with the rear wall, which thus offers its collaboration to contain the horizontal thrusts. The church of San Leonardo has a reverse operation, with the dome that rests on the outer walls, while the internal pillars support only a raised gallery. Through three-dimensional info graphics models, the study shows that the entire structure is designed as a discretized system, which replaces the traditional structure based on continuous wall and uniformly distributed loads. The brick vaults are ribbed structure, in which arches and ribs convey loads on the pillars or in precise high-resistance points of the external masonry. This feature makes the space open to the light; also reduces the masonry mass, saving material and reducing construction costs. The formal representation of structural components agrees with the effective static operation of buildings: the decoration on the surface of the dome indicates the presence of ribs. The groins are hollow and open in order to highlight the condition of non-load bearing element.