Combining satellite data with soil measurements for Structural Health Monitoring – Uso combinato di dati satellitari e misure di sensori al suolo per il monitoraggio strutturale

The growing interest in the conservation of architectural heritage and in ensuring safety of civil structures have encouraged, mostly in the last decades, the development of modern techniques of Structural Health Monitoring (SHM). As can be easily understood, it is really complex to thoroughly define the behaviour of historical buildings, for instance due to uncertainties on material properties, their actual conditions and used construction techniques. As well as, for civil structures, the high complexity and large dimensions can lead to a strong variety of local behaviours which are complex to be catch. In light of this, monitoring the health state of structures reveals to be quite useful both for evaluating the conservation status, from which design the interventions in a targeted way, and also to have a comprehensive health state scenario after sudden events like earthquakes. In this context, Vibration-Based SHM aims at predicting the insurgence or worsening of damages from anomalous variations of the structural modal parameters. Such a kind of system stands out, among the possible approaches, thanks to their non-invasiveness, relatively low costs and ease of installation. One of the main aspect that partially counteracts these advantages is the marked sensitivity of modal parameters to Environmental and Operational Variations (EOVs). Additionally, it is frequent practice in SHM to discard the elastic coupling between structure and soil, by assuming that buildings vibrate as they are fixed at the base. One of the most discussed issues in monitoring of civil and monumental structures is indeed the Soil-Structure Interaction (SSI); in general, it is evident that such a kind of simplification induce an increase of anomalies, misdetections and occurrence of false alarms. In light of this, recent studies aim to overcome the current limitations trying to quantify the effects of SSI and potentially also of Structure-Soil-Structure Interactions (SSSI), in terms of dynamic response, by accounting for the dependency of soil mechanical properties on environmental parameters. On the other hand, in recent years the satellite remote sensing techniques are gaining great importance, also for their strong flexibility and broad variety of possible applications. Within this frame, the current work aims at exploring the possibility of using satellite observations data in order to extract soil parameters which can influence the elastic response of soils. It has been decided to work with the satellite data coming form the Copernicus program of the European Space Agency (ESA), specifically analysing: Land Surface Temperature (LST) as a measure of ground temperature; Surface Soil Moisture (SSM) and Soil Water Index (SWI) for soil moisture information and lastly, Interferometric Synthetic Aperture Radar Line of Sight (In-SAR LoS) data for ground displacements. These data have been analyzed and processed using appropriate signal analysis techniques. As a result, the SWI parameter seem to be fairly correlated to the in situ hygrometric measurements and thus gave a right signal in the optic of using soil moisture satellite data as governing parameter to model the mechanical characteristics of soils. For this reason, it has been used to calibrate a predictive model of soil moisture. Therefore it was introduced in a specific soil model in which the elastic parameters of the soil are retrieved through the computation of shear wave propagation velocities.