Methodology for Scour Evaluation of US Army Installation Bridges: A Proposed Evaluation for Scour Risk and Channel Instability
ENGINEER RESEARCH AND DEVELOPMENT CENTER VICKSBURG MS GEOTECHNICAL AND STRUCTURES LAB
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At the end of the past decade, channel stability and scour risk considerations were not part of stream crossing design for roads. According to the National Bridge Inspection Standards NBIS, all bridges crossing waterways are to be assessed for vulnerability to scour risk and stream instability. General guidelines for scour risk and channel instability are contained within Hydraulic Engineering Circular HEC Nos. 18, 20, and 23, published by the Federal Highway Administration FHWA. In accordance with the NBIS and FHWA, the US Army Corps of Engineers USACE has developed a scour evaluation program to account for those bridge conditions caused by scour risk and channel instability. The purpose of this document is to present an overview of and the guidelines for identifying bridges on the US Army Installations inventory that are at risk of scour and subject to channel instability. Techniques based on hydrology, geomorphology, and bridge design have been studied for use in channel classification and reconnaissance. Field assessment methods also have been investigated for use in identifying potential channel instability. Qualitative evaluation and quantitative engineering analysis also are presented herein, in order to propose a complete scour evaluation form based on channel stability and rating procedures, as well as basic bridge, culvert, and abutment dimensions. This form is used to obtain general data for determining which bridges might be vulnerable to scour. The scour evaluation form is recommended as an effort in minimizing the risk to the public, monitoring the structure, and recommending repair or replacement strategies.
- Civil Engineering
- Structural Engineering and Building Technology