Bridge Deflection Monitoring Using Small, Low-Cost Radar Sensors

The ability to accurately measure bridge deflections is an important aspect of bridge monitoring and maintenance, both in the US and internationally. Static deck deflections are used to provide load ratings while dynamic deflection measurements may be used to track changes in the dynamic behavior of the bridge due to environmental, loading, and condition changes. Directly measuring bridge deflection has proven challenging, requiring either a fixed reference point or the use of non-contact laser sensors. This presentation introduces wireless, continuous wave radar sensors developed for bridge monitoring applications. The small, bridge-mounted sensors provide a practical and low-cost solution for a range of measurement conditions. As the bridge moves, the radars send a continuous wave that is reflected by a stationary target (either the ground below or a fixed transponder, depending on the application). The reflected signal contains the information necessary to extract the bridge motion. While the theoretical operation is straightforward, there are challenges associated with signal demodulation and data processing in the presence of noise due to interference or long detection ranges. Characterization of the static and dynamic performance of the radar is presented, as well as guidelines for their practical application. The audience of this presentation will be both researchers and practitioners working to improve bridge inspection and monitoring practices. Specifically, the audience will learn about a novel technology to improve bridge testing, gain an understanding of the advantages and challenges of applying radar technology to structural monitoring, and be presented with strategies for achieving a network of distributed radar sensors to capture bridge responses.