Dynamic monitoring and model updating of the Leaning Tower of Pisa

The Leaning Bell Tower of Pisa (Italy) – built between 1173 and 1370 – is included within the list of the World Heritage Sites by UNESCO since 1987. In the past years, the Tower and the underlying soil have undergone many interventions in the attempt to reduce and stop definitely its inclination. The Tower was also equipped with a sensor network in-tended for seismic monitoring, which recorded the dynamic response of the monument un-der some far-field earthquakes. In this study, the dynamic response of the Tower recorded under some recent seismic event has been analyzed in the time- and frequency-domain, thereby allowing the identification of its main vibration modes. Furthermore, a simplified finite element model of this valuable monument has been developed taking into account the soil-structure interaction. This numerical model has been used to perform a large sensitivity analysis and to calibrate the dynamic impedances at the base of the structure. The results of the dynamic analyses performed using the seismic input evaluated on the ground surface by means of a seismic hazard assessment and the local site response analysis are finally pre-sented and discussed.