Palazzo Vecchio, Florence, Italy: Seismometric Monitoring and Dynamic Behavior

The safety assessment of historical monumental buildings is extremely difficult to perform, due to their complexity, both in geometry and in construction properties, and to the limitations of invasive testing. Continuous seismometric monitoring is one of the most effective techniques for investigating these constructions. It can provide important information regarding their dynamic behavior and, indirectly, about their mechanical properties, a crucial support for structural modeling and for conservative interventions. This work illustrates a two-year seismometric campaign performed on Palazzo Vecchio, the town hall and symbol of Florence, one of the most famous buildings in the world. Before the monitoring, a comprehensive knowledge process has been developed in order to understand the main technological and mechanical properties of the monumental complex. The knowledge process included a detailed geometrical survey and a careful diagnostic campaign, ranging from simple observation to non-destructive investigation techniques, such as thermography, georadar, and sonic tests. In the monitoring campaign, special attention has been paid to the Arnolfo Tower, a 95 m tall masonry tower embedded in the Palace’s façade. The Palace and the Tower present geometry, features, and slenderness that are very different from each other, with a dynamic behavior very different as well. The temporal variation in the modal frequencies was related to the seismic events recorded during the monitoring period and to the cyclical nature of the trend of the environmental parameters that were monitored simultaneously. As a result of the analysis, the dynamic properties of Palazzo Vecchio and of Arnolfo Tower have been determined, and the effects on their response of the external oscillation sources, such as earthquakes and temperature variation, have been assessed.