A multidisciplinary insight into the collapse causes of the masonry clock tower and castle in Finale Emilia, Italy

The devastating earthquake sequences of the 20-29th May 2012 in Emilia- Romagna, Italy, caused the full collapse of the masonry clock tower and the partial collapse of the masonry castle in Finale Emilia, one of the historical cities most stricken by the seismic event. The present technical note is aimed at presenting some results of a comprehensive and multidisciplinary analysis conducted by the authors at the Technical Universities of Milan and Bari in cooperation with the Italian Cultural and Architectural Heritage Ministry (MiBAC), within a wider research project aimed at the reconstruction of the structures, after a deep understanding of the causes at the base of the collapses occurred. The two main seismic events, occurred on May 20 and 29th, were characterized by the presence of low frequency ground motions, with relevant vertical components. Consequently, structures having natural periods greater than those typical of ordinary buildings -such as the ones analyzed- have been severely damaged. The analyses conducted comprise a detailed geometric recover of the volumes and materials used before the collapses, basing on post-seismic photogrammetric surveys, historical research on existing documentation and repeated in situ investigation. Despite the apparently good texture of the external masonry walls, in situ surveys have proven the particularly low tensile strength of the joints, an impressive deterioration of mortar as well as bed interlocking within external and internal layers.