| Résumé | The widespread deterioration and some recent collapses of highway bridges have highlighted the importance of developing effective bridge monitoring strategies that can help identify structural problems before they become critical and endanger public safety. A typical major urban centre may possess several hundreds of bridges, which makes it difficult to instrument all these bridges with surface-mounted sensors to monitor their structural performance due to practical and economic reasons. A two-step approach may be used, in which potentially critical bridges are first identified through a screening process by remote satellite-based monitoring, and then further investigated with in-situ monitoring and detailed inspection. The capability of Canada’s RADARSAT-2 advanced Synthetic Aperture Radar (SAR) satellite is being investigated for use in the first step of the proposed approach, which can help prioritize in-situ monitoring and maintenance of critical bridges. Interferometric SAR (InSAR) is an advanced processing technique applied to radar images of the Earth’s surface that can detect very small movements from ground features such as infrastructure systems, including roadway and railway bridges and their major components. By applying InSAR processing techniques to a series of radar images over the same region, it is possible to detect vertical movements of infrastructure systems on the ground in the millimetre range, and therefore identify abnormal or excessive movement indicating potential problems requiring detailed ground investigation. A major advantage of this technology is that a single radar image, which can be obtained in darkness and in any weather, can cover a major urban area of up to 100 km by 100 km, and therefore all bridges in the area could be monitored cost effectively. Preliminary results from the application of this technology to transportation infrastructure assets in selected major Canadian urban centres like Vancouver and Montreal are presented and discussed. |
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