Central Italy Earthquakes occurred in 2016 pointed out once more the vulnerability of Cultural Heritage (CH), especially for what concerns bell-towers since they tend to get dramatically damaged due to their considerable slenderness and deterioration, endangering their surroundings and making their preservation fundamental. This work presents the results of the study carried out on four different isolated masonry bell towers, located in Ferrara province (Italy); the parameters of the materials were deduced by calibrating Finite Element Models (FEMs) using the data collected during an investigation campaign conducted with a wired accelerometric sensor system, since it was not possible to apply destructive methodologies. Dynamic data were extracted through the application of two Operational Modal Analysis (OMA) identification techniques: the Enhanced Frequency Domain Decomposition (EFDD) and the Stochastic Subspace Identification (SSI) methodology. Particular attention was devoted to the use of MAC matrix in the validation of the mode shapes results.

Background: In October 2016, two major earthquakes occurred in Marche region in the Centre of Italy, that resulted in widespread damage. The second one strokes Norcia, Visso, Arquata del Tronto, Accumoli and Amatrice, causing a lot of damages to cultural heritage of the cities of Tolentino, San Severino, Camerino and Ascoli Piceno, where the church ofSanta Maria della Caritàis located.Introduction: The church has high historical, architectural and social value for the city of Ascoli Piceno, because it is the only one that is opened to the devotees all time in the day and night. From the structural point of view, the church has a long and important annex to the north, which was later built with respect to the church, and after the L’Aquila earthquakes (2009) damages, the church was subjected to a retrofit intervention, in order to obtain a better “box-like behavior”.Objective: This paper addresses how the relevant annex influenced the seismic response of this historical complex and how, more generally, this kind of asymmetric mass may affect the behavior of historic churches.Results and Conclusion: The results indicate that the presence of annex plays a significant role in the dynamic response of the church and affects the distribution of damages in the whole building. The results of the seismic simulation agree with the observed damage.