Analysis of Environmental Effects on the Natural Frequencies of the Civitacampomarano’s Belfry

Masonry towers are distinctive landmarks of Italian historical city centers and because of their historical and architectural relevance, they have been widely investigated to assess their seismic vulnerability and design appropriate interventions. In this framework, Operational Modal Analysis and continuous vibration based Structural Health Monitoring (SHM) play a primary role in supporting numerical modeling and for timely detection of damage. About the latter, it is well known that the experimentally estimated modal parameters can be used as damage sensitive features for SHM application. However, they are also sensitive to environmental and operational conditions, whose effect must be properly taken into account. The present paper discusses an application of vibration based SHM to a historic masonry bell tower. The tower is located near a landslide and in a seismically prone area, thus making timely identification of possible damage crucial for its preservation and maintenance. Natural frequency time series of the bell tower recorded right before and after the Montagano’s earthquake hitting the structure on March 2023 are here processed in order to discriminate between the normal variability due to environmental effects and that induced by damage.