Evaluating Scour At Bridges

This document is the third of HEC 18, i.e., presents the state of knowledge and practice for the design, evaluation, and inspection of bridges for scour. It contains updated material not included in the second edition dated April 1993. This document is a revision to HEC 18 dated April 1993 which, in turn, was an update of HEC 18 dated Feburary 1991 and of the publication, "Interim Procedures for Evaluating Scour at Bridges," issued in September 1988 as part of the FHWA Technical Advisory T 5140.20, "Scour at Bridges." T 5140.20 has since been superseded by T 5410.23, "Evaluating Scour at Bridges" dated October 28,1991. This document contains revisions obtained from further scour-related developments and use of the 1993 edition of HEC 18 by the highway community

This document is the fifth edition of HEC-18. It presents the state of knowledge and practice for the design, evaluation and inspection of bridges for scour. There are two companion documents, HEC-20 entitled "Stream Stability at Highway Structures," and HEC-23 entitled "Bridge Scour and Stream Instability Countermeasures." These three documents contain updated material from previous editions and continued research by NCHRP, FHWA, State DOTs, and universities. This fifth edition of HEC-18 also contains revisions obtained from further scour-related developments and the use of the 2001 edition by the highway community. The major changes in the fifth edition of HEC-18 are: expanded discussion on the policy and regulatory basis for the FHWA Scour Program, including risk-based approaches for evaluations, developing Plans of Action (POAs) for scour critical bridges, and expanded discussion on countermeasure design...

The most common cause of bridge failures is from floods scouring bed material from around bridge foundations. Scour is the engineering term for the erosion caused by water of the soil surrounding a bridge foundation (piers and abutments). The purpose of this document is to provide guidelines for the following: 1. Designing new and replacement bridges to resist scour, 2. Evaluating existing bridges for vulnerability to scour, 3. Inspecting bridges for scour, 4. Improving the state-of-practice of estimating scour at bridges. This document is the fifth edition of HEC-18. It presents the state of knowledge and practice for the design, evaluation and inspection of bridges for scour. There are two companion documents, HEC-20 entitled "Stream Stability at Highway Structures," and HEC-23 entitled "Bridge Scour and Stream Instability Countermeasures." These three documents contain updated material from previous editions and continued research by NCHRP, FHWA, State DOTs, and universities. This fifth edition of HEC-18 also contains revisions obtained from further scour-related developments and the use of the 2001 edition by the highway community. The major changes in the fifth edition of HEC-18 are: expanded discussion on the policy and regulatory basis for the FHWA Scour Program, including risk-based approaches for evaluations, developing Plans of Action (POAs) for scour critical bridges, and expanded discussion on countermeasure design philosophy (new vs. existing bridges). This fifth edition includes: a new section on contraction scour in cohesive materials, an updated abutment scour section, alternative abutment design approaches, alternative procedures for estimating pier scour, and new guidance on pier scour with debris loading. There is a new chapter on soils, rock and geotechnical considerations related to scour. Additional changes include: a new approach for pier scour in coarse material, new sections on pier scour in cohesive materials and pier scour in erodible rock, revised guidance for vertical contraction scour (pressure flow) conditions, guidance for predicting scour at bottomless culverts, deletion of the "General Scour" term, and revised discussion on scour at tidal bridges to reflect material now covered in HEC-25 (2nd Edition).

Full color, richly illustrated book. This manual is part of a set of HECs issued by FHWA to provide guidance for bridge scour and stream stability analyses.

Sponsored by the Water Resources Engineering (Hydraulics) Divsion of ASCE. This collection contains 75 papers and 321 abstracts presented at conferences sponsored by the Water Resources Engineering (Hydraulics) Division of ASCE from 1991 through 1998. The collection contains many new and expanded versions of the original papers and is designed to assist the practitioner with the concepts in evaluating stream instability and scour at bridges. Topics include: history of bridge scour research; bridge scour determination; stream stability and geomorphology; construction scour; instrumentation for measuring and monitoring; field measurement; computer and physical modeling of bridge scour; scour at culverts; and economic and risk analysis. One important paper contains 384 field measurements of local scour at piers made by the U.S. Geological Survey.

"This report contains the findings of a study undertaken to develop, test, and evaluate fixed devices for measuring maximum scour depth. Companion manuals provide specific fabrication, installation, and operation guidance for two such devices. This report and the companion manuals will be of immediate interest to hydraulics engineers, bridge management engineers, and bridge maintenance engineers"--Foreward.

This document, Hydraulic Engineering Circular No. 18 (HEC-18), contains the state-of-knowledge and practice for dealing with scour at highway bridges. The procedures for designing new, replacement and rehabilitated bridges to resist scour are presented. Procedures are presented for evaluating the scour vulnerability of existing bridges as well as inspecting bridges for scour. The use of countermeasures to protect bridges evaluated as failure prone due to scour is also presented. This document replaces the Federal Highway Administration (FHWA) publication "Interim Procedures for Evaluating Scour at Bridges," which was issued with FHWA Technical Advisory 5140.20, "Scour at Bridges," in September 1988.