Optical Structural Health Monitoring of the frescoes in the Conegliano Cathedral, Italy

The Sala dei Battuti (Battuti Hall) in the Scuola dei Battuti, is located in the front part of the cathedral of Conegliano, in north-eastern Italy. The frescoes of the Battuti Hall are subject to serious cracking likely due to differential settlements of the facade of the cathe-dral and of the adjoining bell-tower. Prior to the execution of repair works in the wooden roof of the hall, the Head Office for the Cultural and Landscape Heritage of the Veneto Region decided to monitor the already visible cracks in the frescoes – before and during the structural intervention - in order to avoid any possible disturbance caused by the works to the frescoes, by stopping or calibrating the activ-ities if any sign of cracks widening was noticed during the works execution. Besides monitoring the main cracks by means of “traditional” electronic linear potentiom-etric displacement transducers, it was adopted an innovative optical monitoring system, com-posed by a camera facing the main reported crack, in the Battuti Hall, where the use of traditional methodologies was forbidden due to the presence of frescoes. The paper describes the SHM system with a specific focus on the optical acquisition system, comparing the results of this last with the outcomes of the more traditional linear potentiometric displacement transducers, with more than one year of comparative results.