An international research team led by Pietro Milillo (University of Houston) analyzed 744 long-span bridges across the world and found a concerning pattern: many bridges, especially in North America and Africa, show signs of structural weakness and are likely past their safe design life, tells Tech Xplore. Aging infrastructure is a key factor: much of North America’s bridge stock was built in the 1960s, so many structures are now old and deteriorating.
To overcome limitations of infrequent inspections and sparse sensor deployment, the researchers applied Multi-Temporal Interferometric Synthetic Aperture Radar (MT-InSAR). This remote sensing technique uses satellite radar to detect micrometer-scale displacements over time. By combining multiple radar images, the method can track subtle movements such as subsidence, shifting foundations, or slow deformation that precedes visible damage.
One major insight is that fewer than 20% of the examined long-span bridges have structural health monitoring (SHM) sensors installed. That leaves vast gaps in real-time structural data. The team proposes integrating satellite observations with existing SHM data under a unified risk framework.
By incorporating “persistent scatterers” (radar pixels that remain stable over time) into assessments, the researchers reduced uncertainty in risk estimation and improved reliability in ranking bridges by structural vulnerability. They suggest that satellite monitoring could oversee over 60% of the world’s long-span bridges.
Ultimately, the study argues for a shift from reactive inspections to proactive, continuous surveillance using satellite data. When combined with in-field inspection and sensors, such an approach could prioritize maintenance resources, prevent catastrophic failures, and extend the safe life of critical infrastructure worldwide.