Dynamic monitoring and nonlinear analysis of the dome of the basilica of S.Maria degli Angeli in Assisi

During the last years, the application of Structural Health Monitoring (SHM) systems to heritage constructions has received a great interest due to the low invasiveness and low-cost of the necessary equipment. When applied to monumental structures and, more in general, to cultural heritage ones, such SHM systems represent an effective solution for preventive conservation against both material degradation and damages derived by natural hazards, such as earthquakes. Among the various technical solutions currently available for SHM, vibration-based systems deserve a special attention, but their application in the context of historical constructions is still quite rare and challenging, with very few documented applications, mostly limiting to masonry towers and bell-towers for their slenderness properties. In this work, the first months of continuous vibration monitoring of the dome of the Basilica of Santa Maria degli Angeli in Assisi are presented. At first, a dynamic identification has been carried out using five high-sensitivity accelerometers, three of them installed at the base of the drum and two at the base of the dome. Then, a fully automated identification technique has been used to extract time series of natural frequencies during the monitoring period. Moreover, some statistical tools have been applied in order to select the best configuration, in terms of number and position of sensors, necessary to obtain a continuous frequency tracking of the first natural modes in view of the use of this information for rapid post-earthquake structural assessment. Moreover, a preliminary investigation about the seismic assessment has been carried by means of a Finite Element (FE) nonlinear dynamic analysis. The damage map obtained by the numerical simulation has been compared with the actual crack scenario present on the structure, giving further information about the structural dynamic response.