• Evaluating Hydraulic Spread Calculations and Closed Drainage Performance System

    NCDOT Research Project Number: 2021-10

 Executive Summary

  • Hydraulic spread calculations dictate the number and spacing of deck drains and closed drainage system locations. Closed drainage systems require routine maintenance to function properly, but typically maintenance is not performed until the drainage system has failed, and problems become apparent. Current procedures for calculating hydraulic spread result in a closely spaced bridge deck drains which present a construction challenge and require regular maintenance during the life span of the bridge. Current drainage system adopted by North Carolina Department of Transportation (NCDOT) routinely fails and is difficult to maintain.

    Deck Drainage.png

    Example of a closed deck drainage system in North Carolina 
    (Winston et al., 2012)

    The main objective of this research is to update NCDOT's guidelines for bridge deck drainage system design and investigate potential alternative drainage systems to be used by NCDOT in future bridge construction projects. The research implementation includes the following tasks:

    1. Perform a literature review of relevant research and specifications for different drainage systems adopted by different state transportation departments within the United States, including the review of current NCDOT policy and procedures. The literature review will focus on practices implemented in states with similar rainfall and environmental conditions.
    2. Review existing hydraulic spread policy in other states to provide possible updates for current policy at NCDOT.
    3. Evaluate closed drainage system used by NCDOT and other states to identify detailed parameters affecting the system effectiveness, and possibly detect causes of potential drainage system problems at NCDOT. The evaluation of NCDOT closed drainage system will provide recommendations to modify the current system and minimize existing problems. In addition, the evaluation of closed drainage system will provide recommendations for possible adjustments to improve the drainage efficiency and reduce the need to future maintenance, repair, and replacement requirement of closed drainage system of future projects.
    4. Investigate alternate drainage solutions and techniques including alternate closed drainage systems adopted by other states or new open-drainage systems, similar to residential drainage through gutters. The alternative drainage systems will be compared according to their initial cost of installation, potential maintenance requirement, hydraulic efficiency, and life cycle cost.

    The outcome of this research project includes providing the NCDOT with a conclusive report that will assist department personnel in achieving increased drainage efficiency with minimal future maintenance requirements. Research outcomes will include: 

    • providing NCDOT with recommended procedures and calculations for hydraulic spread with relevant spreadsheets or design software packages to be used in future NCDOT projects, 
    • recommendations for improved closed drainage system to minimize clogging, leaks, and insufficient drainage efficiency, and 
    • update Design Manual and Appendixes with details to implement the provided recommendations. Upon the completion of this research project, the research findings will provide NCDOT personnel with improved hydraulic spread calculations to reduce the number of bridge deck drains, which will reduce the initial construction cost, minimize maintenance expenditure, and improve the life cycle cost of the bridge drainage system.

Amin K. Akhnoukh
Amin K. Akhnoukh; Rudolf Seracino
Trey Carroll
Mustan Kadibhai, PE, CPM
East Carolina University

 Related Documents

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 Report Period

  • January 1, 2021 - December 31, 2021


  • In Progress


  • Structures, Construction and Geotechnical

 Sub Category

  • Miscellaneous

 Related Links

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