Background: Current methods for predicting local scour at bridge piers, including those described in Hydraulic Engineering Circular No. 18 (Publication No. FHWA NHI 01-001, "Evaluating Scour at Bridges"), were developed on the basis of small-scale laboratory studies and do not consider factors relevant to wide piers and long skewed piers. Because of these limitations, the current methods generally over-predict local scour at such piers, leading to the use of unwarranted and costly foundations or countermeasures. There is a need for research to evaluate current methods for predicting local pier scour and their applicability to wide piers and long skewed piers and to develop improved methods for use by highway agencies in the design, operation, and maintenance of highway bridges.
Objective: The objective of this research is to develop methods and procedures for predicting time-dependent local scour at wide piers and at long skewed piers, suitable for consideration and adoption by AASHTO. The research shall be limited to non-cohesive soils and steady flow.
Status: The project is complete. The research reviewed available information relevant to the prediction of time-dependent local scour at wide piers and at long skewed piers, compiled and evaluated relevant laboratory and field databases, and identified and evaluated predictive equations. Based on this work, the research recommended a predictive equation for local scour and identified a potential equation for predicting scour evolution rates at wide piers and skewed piers. The final report has been received; copies have been distributed to Program sponsors (state departments of Transportation). The final report has been published as NCHRP Report 682.