Leaning tower of Pisa: recent studies on dynamic response and soil-structure interaction

The Leaning Bell Tower of Pisa has been included in the list of the World Heritage Sites by UNESCO since 1987. Over the last 20 years, the Tower has successfully undergone a number of interventions to reduce its inclination. The Tower has also been equipped with a sensor network for seismic monitoring. In this study, preliminary results on the dynamic behavior of the monument are presented, including a review of historical seismicity in the region, identification of vibrational modes, definition of seismic input, site response analysis, and seismic response accounting for soil-structure interaction. This includes calibration of the dynamic impedances of the foundation to match the measured natural frequencies. The study highlights the importance of soil-structure interaction in the survival of the Tower during a number of strong seismic events since the middle ages