The Vasari’s Cupola of the Basilica dell’Umiltà in Pistoia. Studies, surveys, and one year structural monitoring results

The Cupola of the Basilica della Madonna dell’Umiltà in Pistoia was designed and realized by Giorgio Vasari in the middle of the sixteenth century. Soon after its completion, the Cupola manifested serious structural problem: Vasari himself carried out the first retrofitting works, through the insertion of steel chains inside and outside the Cupola. Additional chains have been inserted over the centuries due to the evolution of the cracking pattern. Last restorations in modern time are due to Albino Secchi, former responsible for Soprintendenza (the Institution in charge of conservation of historical buildings), who, in 1966, added two chains. Since 2008, the Cupola of the Basilica dell’Umiltà has been interested by a series of studies, experimental investigations and analyses - promoted by Soprintendenza and financed by the Cassa di Risparmio di Pistoia e Pescia Foundation - aimed at the conservation of the structural complex. The project consisted of the restoration of the whole Basilica; the restoration of the Cupola started in 2012 and concluded in 2014 with the renovation of the lantern. As a conclusive part of the restoration, a new steel chain was inserted and a monitoring system installed. This paper, after a brief description of the Cupola, reports the results obtained from a numerical model, tuned according to the identified modal behavior of the structure and the results of few static tests; the main features of the installed structural monitoring systemare also reported and discussed.