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Ten-Year Review of Monitoring System on I-35W Saint Anthony Falls Bridge

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Status:  Complete
Report Date:  07/06/2020

Summary:

Opened to traffic in 2008, the St. Anthony Falls Bridge, a smart bridge with over 500 gauges and sensors embedded in the structure, continues to collect useful information. A 10-year check-in found that 90% of the successfully installed instruments still gather and report data. Key systems track temperatures in the structure, displacements from the natural creep and shrinkage of concrete, and strains in bridge elements. The original corrosion detection system has not, at any point, produced usable information. Data shows that the bridge manages significant thermal strains caused by temperature variations in the environment, such as sunlight heating or rainfall cooling the top of a deck but not the underside, forcing uneven expansion or contraction in the concrete. Conservative design choices protect the structure from these stresses. In future smart bridges, designers may adjust instrumentation plans based on these findings, electrically grounding systems for stormproof performance, providing a wider distribution of temperature gauges and possibly using wire-based strain gauges rather than fiber optic sensors. Researchers recommended design standards and modeling options for Minnesota locations based on data trends observed with the St. Anthony Falls Bridge.

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