DYNAMIC BEHAVIOR OF A MASONRY TOWER DURING LOW MAGNITUDE SEISMIC EVENTS: RESULTS OF AN EXPERIMENTAL MONITORING CAMPAIGN ON THE ARNOLFO TOWER (FLORENCE, ITALY)

Continuous seismometric monitoring of built structures allows the estimation of structural parameters in ordinary conditions, in the case of anthropic actions inside or outside the structure, and in the case of seismic events of different magnitude, hypocentral distances or epicentral azimuths. Moreover, in the case of buildings of historical and monumental interest, dynamic monitoring is a valid tool to compensate for the lack of information on the mechanical-physical properties of the construction materials, the geometry and the construction history, which can be up to several hundred years old, providing useful indications for the definition of numerical models for the dynamic behaviour simulation. Recognizing how the response in ordinary conditions of historic buildings varies during stresses produced by even small-magnitude seismic events can help in estimating the elastic behaviour of the structure when subjected to larger seismic actions. This study presents data acquired during a long-term experimental campaign conducted on the Torre di Arnolfo of Palazzo Vecchio in Florence. During the campaign seismic events characterized by different source parameters were recorded. The estimation of the dynamic behaviour of the Tower in unperturbed conditions and during earthquakes permitted the assessment of how the dynamic response may vary as a function of magnitude, distance and azimuth of the event. The ultimate target was to understand if and how the results obtained can contribute to providing useful information to define possible damage scenarios produced by seismic events originating in the different seismogenic zones present in the area surrounding the structure under study.