On the DInSAR technique for the structural monitoring of modern existing bridges

The set-up of efficient strategies for the safety assessment and maintenance of modern existing bridges emerges as a crucial research challenge in structural engineering. In Italy, the topic is recently addressed by the "Guidelines for risk management, safety assessment and monitoring of existing bridges", issued in 2020. The Guidelines outline procedures and tools for the safety assessment and maintenance interventions: a mandatory step is represented by the analysis of original documents (concerning the design, the construction process, and the maintenance interventions) to acquire a robust knowledge of the structure. As witnessed by recent literature, non-invasive structural monitoring approaches, among which Multi-Temporal Differential Synthetic Aperture Radar Interferometry (DInSAR) techniques can be included, play a crucial role in the safety assessment of existing bridges. The paper focuses on a cross-disciplinary process for the structural monitoring of modern existing bridges, based on the integration of the DInSAR measurement, exploiting the COSMO-SkyMed measurements collected during the 2011–2019 time interval, and the accurate knowledge of the structures derived by the analysis of the original documents conserved in the historical archives. The procedure is applied to the case study of two reinforced concrete Gerber bridge in Rome, designed in the 1930s.