THE COLOSSEUM

The original design of the Colosseum was a robust, closed structure with concentric rings and radial walls. However, due to foundation settlements and earthquake vibrations, a significant portion of the external zone on the south side has collapsed, making the structure more vulnerable. To maintain the current situation and prevent further collapses, it is essential to support monitoring activities focused on the structural health conditions of the monument. This study centers on dynamic monitoring based on variations in specific dynamic properties over time. After reviewing some elements of structural dynamics, modal quantities, frequencies and vibration modes, are shown to be suitable for monitoring because they can be easily determined experimentally and are sensitive to damage. The technique has been applied comparing the results obtained in two experimental campaigns in 2006 and 2022, where the Colosseum response to ambient excitation has been measured. Additionally, recorded accelerations from road traffic and a recent earthquake enable an assessment of traffic vibrations and a preliminary evaluation of the seismic vulnerability.