Determination of scour susceptibility through rapid assessment

Abstract

A need existed to efficiently predict the potential scour that could be expected at nearly 20,000 existing off-system bridges in the State of Kansas to assign a National Bridge Inspection Standards (NBIS) Item 113 coding. A customized methodology for scour evaluation was developed through the guidance of TranSystems Corporation, The Kansas Department of Transportation, and the Federal Highway Administration. This thesis presents a procedure to rapidly assess the scour potential at existing bridges. This procedure consists of a prioritization method and routines to rapidly estimate scour components outlined in FHWA guidelines. Key to the successful implementation of this procedure is all information including bridge plans, historic inspection records, historic photographs, and current photographs were digitized, geo-referenced, and incorporated into GIS software. This procedure was validated on approximately 300 bridges and, at the time this report was written, has been applied to over 8,000 existing off-system bridges in the State of Kansas. The procedure was beneficial because it is repeatable, the information is easily obtained at a relatively low cost, it requires multiple sets of eyes on every bridge, it is efficient, it accounts for the main scour components outlined within HEC-18, and the results show good correlation with HEC-18 results.Although this procedure was developed for use in the state of Kansas, it may be applicable for use in other states. However, before doing so an evaluation of the site specific information should be performed and if necessary modifications should be made to the procedure to account for regional issues. The rapid assessment should only be administered by an Interdisciplinary Scour Team having expert knowledge with regards to structural, hydraulic, and geotechnical engineering.