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<br />1. Report No, HEC-18 2, Government Accession No. 3, Recipient's Catalog No,
<br />4, Title and Subtitle 5, Report Date
<br /> EVALUATING SCOUR AT BRIDGES
<br /> 6. Performing Organization Code
<br />7, Author(s) 8, Performing Organization Report No,
<br /> E,V, Richardson and S,R. Davis
<br />9, Performing Organization Name and Address 10, Work Unit No, (TRAIS)
<br /> Ayres Associates, formerly Under Contract to:
<br /> Resource Consultants & Engineers GKY and Associates, Inc.
<br /> 3665 JFK Parkway 5411 E. BacIdick Rd,
<br /> Building 2, Suite 300 Springfield, VA 22151 II. Contract or Grant No,
<br /> Fort Collins, Colorado 80525 DTFH61-93-C-00 101
<br />12. Sponsoring Agency Name and Address 13, Type of Report and Period Covered
<br /> Office of Technology Applications, HTA-22
<br /> Federal Highway Administration
<br /> 400 Seventh Street, S,W, 14, Sponsoring Agency Code
<br /> Washington, D,C, 20590
<br />IS. Supplementary Notes
<br /> Project Manager: Mr. Thomas Krylowski
<br /> Technical Assistants: Larry Arneson, Chris Dunn, L.J, Harrison, J, Sterling Jones, Johnny L. MOlTis, Jorge Pagan, Philip
<br /> L. Thompson, Arlo Waddoups, FHWA; G,K. Young, GKY & Assoc" Dave Halverson, MOOT; P,F, Lagasse,
<br /> J,R, Richardson, L,W. Zevenbergen, Ayres; Lee Butler, WES
<br />16, Abstract
<br />This document is the third edition of HEC-18, Le" presents the state of knowledge and practice for the design, evaluation, and
<br />inspection of bridges for scour, It contains updated material not included in the second edition dated April 1993, This
<br />document is a revision to HEC-18 dated April 1993 which, in turn, was an update ofHEC-18 dated February 1991 and of the
<br />publication, "Interim Procedures for Evaluating Scour at Bridges," issued in September 1988 as part of the FHWA Technical
<br />Advisory T 5140.20, "Scour at Bridges," T 5140,20 has since been superseded by T 5140,23, "Evaluating Scour at Bridges"
<br />dated October 28, 1991. This document contains revisions obtained from further scour-related developments and use of the 1993
<br />edition of HEC-18 by the highway community.
<br />The principal change from the 1993 edition ofHEC-18 is the use of metric (SI) units of measurement. Additional changes are:
<br />a discussion of backwater effects on contraction scour and the use of the water surface or the energy grade line as the reference
<br />line for measuring contraction scour depths, addition of a coefficient to the pier scour equation to account for the armoring
<br />effect of large particle sizes in the bed material, and addition of an equation to compute the coefficient applied to the pier scour
<br />equation when there is an angle of attack, Figures have been added to clarify computation of pier scour for exposed footings,
<br />pile caps placed in the flow, multiple columns skewed to the flow, and scour resulting from pressure flow, This document
<br />includes a method to compute scour depths for pressure flow when a bridge deck is submerged. A method to compute ll.H for
<br />constricted tidal waterways is given along with the procedure used by Maryland SHD to evaluate scour for bridges over tidal
<br />waterways, A discussion of computer models to determine the value of the hydraulic variables for scour analysis of bridges
<br />over tidal waterways has been added and information on scour detection equipment has been updated based on recent research,
<br />Finally, minor errors in the text and figures have been corrected,
<br />17, Key Words 18, Distribution Statement
<br /> scour design, contraction scour, local scour, pier scour, This document is available to the public through the
<br /> abutment scour, scour susceptible, scour critical, clear- National Technical Information Service,
<br /> water scour, live-bed scour, superflood, bridge Springfield, V A 22161 (703) 487-4650
<br /> inspection, countermeasures, tidal scour
<br />19. Security Classif, (of this report) 20, Security Classif, (of this page) 21. No, of Pages 22. Price
<br /> Unclassified
<br /> Unclassified
<br />
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