Piers in the waterway affect the velocity distribution across the channel and may act as barriers to floating debris. In addition, they also affect channel geometry by causing general anddlocal scour in the vicinity of the bridge. The level of hydraulic efficiency of an unobstructed channel may be reduced by several percent if piers are placed in the waterway. Reductions of up to 11 percent were observed at sites used in the study. Field studies of several channels indicate that depths of general scour may be greater scour usually occur midway between piers. General scour may extend several hundred feet upstream and downstream from the bridge. Large piers in alluvial channels may initiate long-term general scour that may continue for decades. General scour at a bridge has been observed to cause enlargement of the channel by as much as 23 percent to compensate for reduced flow area and flow inefficiency associated with bridge piers. Pier design should consider the probability that the channel alignment and geometry will change with time. To reduce the potential for pier damage by streamflow; pier shape, size, spacing, location in the channel, and footing elevation relative to the lowest point in the channel bed should be considered. Pier size should individually or collectively occupy not more than about 5 percent of the original waterway at bankfull discharge. (Author)

Media Info

  • Media Type: Print
  • Features: Figures; References; Tables;
  • Pagination: pp 172-183
  • Monograph Title: Second bridge engineering conference. volumes 1 and 2
  • Serial:

Subject/Index Terms

Filing Info

  • Accession Number: 00390827
  • Record Type: Publication
  • ISBN: 03090036593
  • Files: TRIS, TRB
  • Created Date: Dec 30 1984 12:00AM