Full structural dynamic response from ambient vibration of Giotto's bell tower in Firenze (Italy), using modal analysis and seismic interferometry

Abstract

The preservation of historical buildings mainly depends on our capacity to monitor their ageing and quickly detect potential damage. We show how the dynamic characteristics of a building (i.e., frequency, shapes mode and seismic wave velocity) can be automatically identified and tracked in real-time by combining modal analysis with seismic interferometry. The assessment of these characteristics is performed on Giotto's bell tower in Firenze, Italy, by installing a temporary network of seismic sensors. The natural frequencies and modal shapes of the structure are calculated by enhanced frequency domain decomposition (EFDD). The impulse response functions estimated by following a waveform deconvolution approach are analysed to investigate the seismic wave dispersion in Giotto's bell tower. We show that Giotto's bell tower is a dispersive structure affected by a bending deformation, with a weak contribution from soil-system interaction. Combining the results of operational modal analysis (OMA) and seismic interferometry from the same ambient noise recording provides a unique and complete dynamic response of important monuments such as Giotto's bell tower.