Advances and Trends in Structural Engineering, Mechanics and Computation – Zingoni (Ed.) © 2010Taylor & Francis Group, London, ISBN 978-0-415-58472-2 Brunelleschi’s dome in Florence: The masterpiece of a genius C. Borri, M. Betti & G. Bartoli Department of Civil and Environmental Engineering (DICeA), Florence, Italy Gratefully dedicated to the memory of our formerTeacher, Prof.Andrea Chiarugi, for his pioneering contributions. ABSTRACT: After a brief description of the main geometric characteristics and the relevant constructive aspects ideated by Brunelleschi to build the Dome of Santa Maria del Fiore the paper sketches the actual cracking pattern together with recent results concerning the static behavior of the Dome. The F.E. model built to assess the Dome’s structural behavior is described, and the identification procedure (based on the results of previous in-situ experimental investigation) is illustrated. The paper offers a contribution in the assessment of the safety and vulnerability of one of the most emblematic masonry domes all over the world. 1 INTRODUCTION The paper approaches the problem of safety evaluation of the Brunelleschi’s Dome of Santa Maria del Fiore in Firenze (Italy) which has been declared part of the UNESCO World-Wide Heritage in late 1982. The first stone of the Santa Maria del Fiore Cathe- dral was laid on September 9, 1296. The new church was originally designed by Arnolfo di Cambio (about 1240–1310) in the Gothic style. He planned a three wide naves church ending under an octagonal dome (an octagonal dome 42 metres in span to be built at the east end of the nave). The middle nave of the new church was covering the area of the old church (Santa Reparata). The construction of this impressive project required about 170 years, and it collects the efforts of several generations of “Maestri muratori” (freema- son). At the end the Arnolfo’s plan for the Santa Maria del Fiore Cathedral, although maintained in concept, was greatly expanded in size and majesty. The construction of the Dome, in particular, started in 1420 (August, 7) and finished in 1434 under the design and the supervision of Filippo Brunelleschi (1377–1446) that initially began to work to the fab- ric of Santa Maria del Fiore making statues for the cathedral. Gradually he became interested in the build- ing itself and in about 1415 he prepared a design that, audaciously, proposed to build the Dome without the aid of formwork, which had been absolutely necessary in all previous Roman and Gothic construction. In only 14 years one of the most extraordinary constructions of Renaissance was built. The Brunelleschi’s Dome remains one of the largest brick dome ever built in the world. The paper, discussing the case study of the Brunelleschi’s Dome (Fig. 1), present a careful use of numerical analyses to face practical engineer- ing problems in the field of historical construc- tions. The Dome is analysed to assess its structural behaviour under static loads and, eventually, hori- zontal loads. To this aim, 3D non-linear analyses have been performed by the FE technique: the non- linear behaviour of masonry has been considered through proper assumptions. A basilar concept of the assessment methodology considered in the present study is the achievement of an adequate knowledge of structural static behaviour (and materials for that matter) that is essential also for seismic evaluation purposes. After calibrating the numerical model to fit the damage state non-linear analyses have been per- formed to assess potential seismic vulnerability of the Dome. 2 GEOMETRY AND CONSTRUCTIVE TECHNIQUE From a structural point of view the Brunelleschi’s Dome consists of two layers: an inner thin dome span- ning the diameter of the octahedral ring beam and an external thin one to protect it against the environ- mental loads (Fig. 1). The inner layer (intrados) has a constant thickness; the outer layer (extrados) becomes gradually thinner from the base to the oculus. These two layers are structurally connected by masonry joining elements that starts from the octa- hedral ring beam and continues until the oculus, the top level of the Dome. 1317