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South Dakota Department of Transportation
Project Synopsis

Title: Precast Box Culvert Inlet Loss Coefficients
Project Researcher: Turner-Fairbank FHWA,
Project Manager: Jon Becker
Research Period: -
Cost: $0.00

Problem Statement:The Turner-Fairbank Highway Research Center agreed to determine inlet loss coefficients for certain inlet types used by SDDOT. SDDOT supplied the Research Center with plans, specifications, and photographs to be used in building scale models with which the testing would be accomplished. The initial models were built and hydraulics testing performed as a graduate research fellowship project. Unfortunately, the models were not properly constructed and did not conform to the plans. As a result, the inlet loss coefficients determined by testing were not valid. After the research panel pointed this out, the research center agreed to accurately reconstruct the models and perform the tests again. The Research Center contracted with GKY & Associates, Inc., who took over the study and completed it in four months.

During retesting, Richard Phillips, SDDOT Hydraulics Engineer, inspected a representative number of the new models and found them to accurately represent the box culvert inlets submitted for testing. The panel found the final report to be concise, understandable, the test models correctly built, and the experimentally determined inlet loss coefficients appear to be reasonable. The results indicate that the use of 30N flared wing walls, as on cast-in-place inlets, is slightly more hydraulically efficient than straight wing walls with beveled edges, as on precast culverts. Although the original questions in the problem statement were answered, this research has brought up new questions regarding the combined effects of varying barrel size and constant 4" bevel on loss coefficients. The Turner-Fairbank Highway Research Center may perform hydraulics testing on a continual basis, and may be suited to answer these new questions

The panel feels that this project may have been performed on schedule if at the outset we had met with the researcher in person and required that a work plan be written and evaluated by the panel. This may have been impractical, however, because the research was done by a graduate student focusing on many culvert designs, rather than specifically on SDDOTs inlet sections.


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