BRIDGE THE GAP: UPGRADING THE BRIDGE HEALTH MONITORING WITH SYNTHETIC APERTURE RADAR DATA PROCESSING DRIVEN BY STRUCTURAL MODELLING

On December 2021, the European Commission launched the Global Gateway strategy to boost smart, clean and secure links in digital, energy and transport sectors. Transport networks (TN) are recognized as critical enablers of prosperous economies and societies because their security underpins the resilience of the global economy and supply chains. The security of TN is a current priority and it strongly relies on the security of its components. Among others, bridges can be considered as the TN weakest-link, due to their high vulnerability to natural and man-made hazards and deterioration rate over time. Indeed, the infrastructure managers are putting huge efforts in the Structural Health Monitoring (SHM) of bridges, with the aim of supporting their safety level. SHM may benefit from the massive use of space technology, in particular of Synthetic Aperture Radar (SAR) for high-resolution monitoring of structures from satellite platforms by exploiting the multipass Differential Interferometry techniques and specifically focusing on SAR Tomography. This technique allows implementing a fine beam radar scanner from space to accurately inspect in 3D and monitor the surface of infrastructures up to the finest details; the advantage over standard interferometric approaches is in terms of higher accuracy and density of monitored points. Among others, bridges still represent a critical scenario for the deployment of SAR based techniques. Decades of processing of very high-resolution data stressed that these approaches fail to ensure optimal coverage as the bridge length increases and some gaps arise in the spatial coverage. Indeed, the deformation of long-span bridges is significantly affected by the structural configuration (bridge typology, boundary conditions, end-support, material, geometry, etc) and by external actions (traffic loads, temperature variation and wind). Deformation models exploited in SAR interferometric processing, actually do not incorporate the specific bridge characteristics, whereas their consideration could provide an enhanced prediction and a better detection and interpretation of measured displacement trends. At the light of these considerations, the main goal of this proposal is to develop a coupled integrated approach, between SAR signal processing and structural engineering, to include the information provided by a numerical structural modeling in the SAR Tomography phase models. The focus is on long-span and multi-span bridges. A set of bridges has been pre-selected considering both the availability of long-term very high resolution COSMO-SkyMED SAR archives and the suitability of the structural typology. Detailed analyses over two case studies will be firstly addressed. Then a blind prediction over other bridges will be performed, to evaluate the portability of the research findings over large areas.