Remote Sensing Satellite Data and Progressive Collapse Analysis for Structural Monitoring of Multi-span Bridges

This work aims to investigate the potential of the application of Synthetic Aperture Radar Interferometry (InSAR) to bridge monitoring, in order to demonstrate its effectiveness in detecting damages early, preventing collapses and triggering in-situ inspections, especially if integrated with advanced numerical modeling. A post-processing methodology is presented, able to derive two-dimensional displacement configurations of multi-span bridges with properly defined error bounds, using both ascending and descending SAR acquisitions. The bounds are estimated by considering both random and systematic errors, accounting for the orientation of the bridge with respect to the Line-Of-Sights of the satellites, the hypothesized deformation plane and the accuracy of the measurements. The proposed procedure has been applied to the case study of the Albiano-Magra Bridge in Italy, collapsed on April 8th 2020. The results, referred to the monitoring period 2015–2020, highlight anomalies in the displacements of the first two spans and abutment of the East side, observed during the three years preceding the failure, thus providing information on the possible cause of collapse. A numerical model of the bridge, based on the Applied Element Method (AEM), was developed in order to simulate the progressive collapse of the structure subjected to the settlements derived by monitoring data and to verify the hypothesis on the kinematics and its causes.