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Implementation of OMS-Based Scour Prediction and Real-Time Monitoring of Scour Processes for Alabama Bridges
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2025-04-01
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[PDF-6.36 MB]
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Edition:Final Report
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Abstract:This research compares the current methods used by ALDOT in developing bridge pier scour calculations, based on FHWA HEC-18, with alternative methods using the Observational Method for Scour and propose methods for pier scour real time monitoring. The work performed entailed the development of pier scour depth estimates in four Alabama bridges using a range of hydrological and hydraulic approaches. Various peak flow estimation methods—Regional Regression Equations (RRE), Flood Frequency Analysis (FFA), and HEC-HMS 4.9 with SCS Curve Number—were used, with results analyzed through HEC-18 and the Observational Method for Scour (OMS). Hydraulic modeling to compute scour velocities was conducted with HEC-RAS 6.1/6.2, incorporating 1D and 2D approaches. The research determined that RRE, commonly used by ALDOT, frequently did not correspond to the most conservative peak flow rate predictions. Also, it was found that 2D approaches were better at capturing velocity distributions resulting in more representative pier scour depth predictions. OMS yielded scour estimates that were smaller than HEC-18 by at least 20% across the studied bridges. Additionally, long-term scour monitoring using sonar sensors proved to be a simple, low-cost, deployable, and reliable strategy, though requiring periodic visits for simple maintenance. Such approaches can be seen as part of monitoring efforts that could be applied in bridge structures that could be more at risk of excessive scour to ensure their safety.
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