As the nation’s infrastructure continues to age, and traffic congestion continues to increase, the rapid load rating of highway bridges is becoming a necessity. Presented herein are two separate case studies in which static and dynamic deflections of typical highway bridges were measured with a non-contacting interferometric radar system (IBIS-S). The bridges were monitored during both normal traffic loading and known weight, slow rolling load testing. Both bridges were instrumented with additional sensors as an ongoing research project, which provides comparison measurements to the radar system. The Interferometric radar system (IBIS-S) can simultaneously measure the displacement and vibration responses of multiple locations of a structure from distances up to 0.5 kilometer. The IBIS-S system has a maximum accuracy of 0.01 mm (0.0004 inch) and a maximum sampling frequency of 200 Hz (Nyquist frequency of 100 Hz). The system is tripod mounted and can be rapidly deployed, allowing load testing in a matter of hours. The non-contacting nature of the system can, in some instances, provide measurements in otherwise difficult access situations.

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