CHANNEL SCOUR AT BRIDGES IN THE UNITED STATES

Scour of the channel bed around bridge foundations is the leading cause of failure among more than 487,000 bridges over water in the United States. Field measurements of scour at bridges are needed to improve the understanding of scour processes and the ability to predict scour depths accurately. This report documents methods to measure and interpret bridge scour data, presents an extensive pier scour measurement data base, evaluates scour processes in an analysis of these data, and compares observed and predicted scour depths for several scour prediction equations. More than 380 measurements of local scour around bridge piers have been compiled from 56 bridges in 14 States in a cooperative investigation of the U.S. Geological Survey and the Federal Highway Administration. The data are stored in an interactive bridge scour data base management system developed in this study. Improved planning for scour measurements during floods and advances in scour measurement instrumentation and techniques have improved the quantity and quality of measured scour data. Consistent and representative methods are used to interpret scour measurement data that were compiled from several investigations. The relation of scour depth to several explanatory variables, including effective pier width, flow depth, flow intensity, and sediment parameters, is investigated. The data distributions of individual scour variables are typically right skewed. The effective pier width generally has the greatest influence on scour depth. Flow depth has a positive relation with scour depth over the range of measured data; but the influence of flow depth decreases with increasing scour. The positive relation of flow intensity to scour depth is apparent when bed-load transport is negligible, but appears insignificant for active bed-load transport conditions. The influence of sediment size and gradation on local scour depth is inconclusive on the basis of this analysis. Selected local scour prediction equations are evaluated and compared based on the field data. None of the selected equations accurately predict the depth of scour for all the measured conditions. Several equations did better than others when evaluated as design equations. The information in this report is provided to contribute to the improved design and evaluation of bridges, and to the safety of the traveling public.

  • Corporate Authors:

    U.S. Geological Survey

    12201 Sunrise Valley Drive
    Reston, VA  United States  20192

    Federal Highway Administration

    Turner-Fairbank Highway Research Center, 6300 Georgetown Pike
    McLean, VA  United States  22101
  • Authors:
    • Landers, M N
    • Mueller, D S
  • Publication Date: 1996-8

Language

  • English

Media Info

  • Features: Figures; Photos; References; Tables;
  • Pagination: 140 p.

Subject/Index Terms

Filing Info

  • Accession Number: 00725496
  • Record Type: Publication
  • Report/Paper Numbers: FHWA-RD-95-184, 3D3C1-212, Final Report
  • Contract Numbers: DTFH61-87-Y-00123
  • Files: TRIS, ATRI, USDOT
  • Created Date: Sep 3 1996 12:00AM