The role of environmental effects in the structural health monitoring: the case study of the Ficarolo Tower in Rovigo, Italy

The paper presents some preliminary results of the dynamic monitoring of the Ficarolo Tower. The Ficarolo Tower is an historical masonry bell tower about 68 m high and characterized by impressive inclination. The tower reported serious damage during the seismic sequence of May 2012 and, consequently, retrofitting interventions were carried out and a continuous dynamic monitoring system was installed. Valuable information on the structural behaviour and the structural health in the case of seismic events can be obtained from the monitoring system. Modal-based damage detection procedure are based on the relation between variations in the measured modal parameters and changes in the physical properties, such as stiffness reductions due to damage. However, important variations in the dynamic response of a healthy structure can also be caused by changing in the environmental conditions, leading to a false positive diagnosis. For a proper modal-based damage detection, the effects of temperature and humidity on the modal properties have to be removed. To this aim, the paper investigates the effects of temperature and humidity variations on the identified natural frequencies.