Operational Modal Analysis of Doria Castle's Tower in Vernazza

Vibration-based damage identification methods are increasingly adopted for the structural condition assessment of heritage buildings and ancient masonry structures. Structural health monitoring relies on the assumption that structural damages cause observable changes in the dynamic properties of the building itself. Damage identification and condition assessment are needed to assure the serviceability and safety of heritage buildings since they can be damaged due to environmental conditions or material deterioration over the years. The subject of this chapter is the medieval fortress known as Doria Castle, located in Vernazza, one of the most important architectural sites along the coast of Liguria, Italy. During the last winter (2022/23) restoration works have been completed, and in spring the tower was reopened to public access. In this chapter a series of operational modal analysis (OMA) tests have been performed to determine the system's dynamic characteristics such as natural frequencies and mode shapes at four different states of restoration stages. Modal parameters have been estimated using the frequency-domain decomposition (FDD) method applied to the response of the structure to ambient vibration. It is possible to observe that natural frequencies increase constantly with the stiffening of the tower as the restoration work proceeded.