In situ testing and structural assessment of an historic masonry dome

This paper reports some results from a research work focused on the analysis and interpretation of the damage pattern in the Dome of the Siena Cathedral (Italy). The research was motivated by the failure of some elements of the internal stone-truss system connecting the two masonry shells which constitute the Dome structure. Reported data represent the main results obtained from an in-situ survey; then, numerical analyses performed to obtain the static identification of the monument as well as to assess the possible causes that may have led to the observed static problems are described. The numerical modeling was performed by steps, from linear and quite simple models built with plane elements up to non linear models with three-dimensional elements. The non linear FEM, performed with respect to a series of in situ measures, allowed to reproduce the behavior of the monument and to give a first interpretation of the causes for the structural static problems. A preliminary evaluation of the building’s static safety was assessed to account for the observed failure of the stone-trusses system.