Assessment of the dynamic behaviour of an ancient masonry tower in Lucca via ambient vibrations

This chapter focuses on a seismic monitoring experiment conducted on the bell tower of the San Frediano Church in Lucca, Italy. The tower, dating back to the 11th century, has been fitted along its height with four triaxial seismometric stations which were then left active on the tower for four days. Ambient vibration monitoring provides important information on the structural health of ancient masonry constructions, as it is a non-destructive technique able to capture the most important features of their dynamic behaviour, such as natural frequencies, mode shapes and wave propagation velocities. The chapter presents the results of a seismic monitoring experiment conducted on the bell tower of the Basilica of San Frediano in Lucca, Italy. The tower has been instrumented with four highsensitivity triaxial seismometric stations, left active on the tower from 29 May to 3 June, 2015. This sophisticated instrumentation, usually employed in seismic monitoring networks, had already been installed on the Asinelli and Garisenda towers in Bologna.