The Dome of Santa Maria del Fiore in Florence: Historical, geotechnical and structural studies for its conservation.

This paper aims to present the complex and interdisciplinary study carried out on one of the most important masonry dome in the world: the Brunelleschi’s Cupola of Santa Maria del Fiore in Florence. The Cupola has been affected, since the beginning, by a widespread crack phenomena, and different studies were done during centuries in order to clarify its real behaviour: structural models, geotechnical and geophysical investigations. A complex monitoring system was installed on the monument in order to have a direct and indirect record of the cracks which affect the Cupola. An accurate analysis of crack widths and global displacements (horizontal and vertical), performed both considering historical and more recent monitoring data, has allowed to detect the static movements developed in the monument over the time, also considering their relation with environmental and seismic events. In step with the interdisciplinary method, strongly recommended in the field of structural monument conservation, some issues on Cupola damage causes are reconsidered herein. Hence, at the light of the results obtained, the famous XVII century Viviani's conclusion on Cupola damage (horizontal thrusts worsened by seismic response) is here compared with other hypotheses proposed during centuries by other scholars: as the differential settlement of pillars (Cecchini, 1698 and Ximenes, 1757) and the temperature variation influence (Nervi, 1934). The large amount of measured data and the more complex results of the last structural model of the Cupola, combined to the last dynamic measurements, have allowed to update some previous conclusions on the damage cause and trend. Starting from these conclusions, a more reliably forecasting model of the monument can be set up, that could be really useful for both the seismic assessment and the effective conservation strategy for this emblematic monument.