Holographic and seismic comparative modal analysis on Radicofani fortress

In this article, we performed the modal analysis on historical building Rocca di Radicofani located in Tuscany, Italy. The experimental analysis has been conducted by comparing two techniques: Infrared Digital Holography (IRDH) and the traditional seismic measurements. We show how IRDH is able to detect the same structural frequencies and modal shapes of seismic analysis. IRDH, using a long wavelength laser radiation (10.6 µm), allows to accurately monitor large area of buildings without the need to physically access the structures. The remarkable sensitivity (∼0.1 µm) and the capacity to work remotely make the holographic technique significant promise in the field of structural dynamics, especially for buildings with architectural or historical constraints or in case of damaged building. In addition, the ability of the holographic technique to detect the modal parameters can be used to monitor their evolution in time in order to verify the structural health of historical structures.