Tra sicurezza e conservazione: strategie per la conoscenza ed il monitoraggio di torri murarie

A survey of the historic complex of ‘Santa Maria del Carrobiolo’ in Monza highlighted that two sides of the bell-tower are directly supported by the load-bearing walls of the apse and South aisle of the neighbouring church. After the discovery of the weak structural arrangement of the building, a static monitoring was installed to check the opening variation of the main cracks. Subsequently, ambient vibration tests were performed and closely spaced modes with similar mode shapes were clearly identified: since the dynamic characteristics of the tower are quite different from those obtained in past experimental studies of similar structures and conceivably related to the construction sequence, a simple dynamic monitoring system was installed in the tower to complete the health monitoring aimed at the preservation of the historic structure. The paper—after a brief description of the tower and a summary of selected evidences provided by on-site survey, historic research and static monitoring—focuses on the dynamic characteristics identified in the preliminary ambient vibration tests and the main results of the monitoring.