Adaptative Hyperparameters Selection for Modal Tracking Algorithm in Structural Health Monitoring of Masonry Monumental Structures

In the context of Structural Health Monitoring (SHM), a key step in the monitoring process is the extraction of dynamic features of the system. Once the parameters have been estimated through dynamic identification techniques, the following step, as well as one of the most challenging, consists in progressively assigning the identified modal properties of the different identification tasks performed over time to a particular vibration mode. This last procedure in the framework of SHM is referred to as Mode Tracking. It is commonly performed by the comparison between the estimated natural frequencies and associated mode shapes to the modal properties of a set of reference modes. This process could be easier and immediate in the case of simple structures such as multistorey structural systems, while in the case of monumental masonry buildings some more difficulties arise. These difficulties may be due to multiple factors including the structural complexity, the number of available sensors that make up the monitoring system, the possible overlap between the ranges of natural frequency values and the presence of operational and environmental variation. For these reasons, it could be very complicated to be able to track frequencies manually. In fact, if the latter could still work in the case of many sensors and frequency ranges that are not close together, in the case of a few sensors and overlapping ranges, this method would fail, leading to unsatisfactory results. In this study, an adaptative method to obtain the correct parameters for mode tracking is presented. It is applied to a case study of masonry monumental building equipped with long-term dynamic monitoring system.