Ambient Vibrations of Age-old Masonry Towers: Results of Long-term Dynamic Monitoring in theHistoric Centre of Lucca

The paper presents the results of an ambient vibration monitoring campaign conducted on theso-called "Clock Tower" (Torre delle Ore), one of the best known and most visited monuments inthe historic centre of Lucca. The vibrations of the tower were continuously monitored fromNovember 2017 to March 2018 using high-sensitivity instrumentation. In particular, four seismicstations provided by the Istituto Nazionale di Geofisica e Vulcanologia and two three-axialaccelerometers developed by AGI S.r.l., spin-off of the National Institute for Astrophysics, wereinstalled on the tower. The measured vibration level was generally very low, since the structurelies in the middle of a limited traffic area. Nevertheless, the availability of two different types ofhighly sensitive and accurate instruments allowed the authors to follow the dynamic behaviour ofthe tower during the entire monitoring period and has moreover provided cross-validation of theresults.