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Global Structural Assessment of Highway Bridges Through Rapid Modal Analysis

The qualitative nature of visual inspections has helped to fuel significant advances in the areas of non-destructive evaluation and structural health monitoring over the last several decades, but the actual practice of bridge assessment has remained largely unchanged. An envisioned Global Structural Assessment System GSA is presented in which a conventional Falling Weight Deflectometer (FWD) is transformed into a modal impact source allowing quantitative metrics reflecting the health of a bridge to be acquired in a rapid, semi-automated manner. The GSA system is comprised of a trailer equipped with a falling weight capable of imparting a single, controllable, broadband impact. This is paired with a fixed array of sensors. As the GSA is driven across a bridge, Single Input Multiple Output modal testing methods are utilized in which a series of local responses are captured and later ‘stitched together’ to form a complete, unique flexibility matrix. With minimal traffic interference and virtually no time restrictions, qualitative visual inspection may now be supplemented with quantitative metrics on a large scale. Theoretical background, impact source prototype testing, and bench-mark field tests are presented as well as the progress of the development of custom modal processing software.

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