Dynamic-based F.E. model updating to evaluate damage in masonry towers

The paper presents the experimental and analytical modal analysis of a masonry bell-tower, dating back to the XVII century. The tower, about 74 m high, is characterised by the presence of major cracks on the Westem and Eastern load-bearing walls. The field test was carried out by ambient vibration testing; both the classical Peak Pieking spectral technique and the more advanced Frequeney Domain Decomposition procedure were used to extract the modal parameters (natural frequencies and mode shapes) from ambient vibration data. [n the theoretical study, vibration modes were determined by using a 3D finite element model. The experimental data were first used to verify the main assumptions used in the models through rough comparison of measured and predicted modal parameters; furthermore, some structural parameters of the model were updated in order to enhance the match between theoretical and experimental modal parameters.