Techniques for Improving Assessment of the Seismic Vulnerability of a Masonry Bell Tower

Many countries, especially in southern Europe, are heavily exposed to earthquake hazard, that caused severe damage to buildings or even destruction in case of earthquake strong ground shaking [9]. The recent experience of earthquakes showed the behavior, the damage and the intrinsic vulnerability of monumental buildings. Historical buildings and monuments are characterized by an inherent vulnerability to seismic action, due to the fact that most of them frequently lack basic seismic characteristics and/or never were equipped with adequate provisions against the actions of an earthquake. This implies the need for urgent strategies for the protection of cultural heritage from the seismic risk. This paper deals with the structural monitoring and seismic evaluation of a single masonry Tower in a region Puglia in southern Italy: the Bell Tower of the "monastery of St. Clare" in the city of Casamassima. This monument was monitored by means of environmental vibration tests on a large scale. Measured responses were then used for modal identification. The assessment procedure must include morphological and structural knowledge, environmental vibration tests on a large scale, modal identification from ambient vibration feedback, finite element modeling, dynamic model identification. A satisfactory improvement in modal parameters is obtained, resulting in an agreement between the modal properties observed in dynamic tests and those calculated by a numerical model. Nonlinear dynamic analysis helps you identify potential mechanisms of collapse and dangerous structural weaknesses may play a key role in the seismic vulnerability of the towers.