Estimation of scour for bridges in Illinois

Scour development around bridge piers is one of the main reasons for bridge failure. This paper presents the comparison of ultimate pier and contraction scour depth for cohesive soils at nine bridge sites in Illinois. Results obtained from common prediction methods such as SRICOS, Hydraulic Engineering Circular No. 18 (HEC 18), Florida Department of Transportation (FDOT) and reduction factor method were compared. All bridge piers have round nose shape except one. SRICOS and FDOT method predicted the lowest and highest ultimate depths of scour, respectively. Measured scour depth for real time obtained from the field was also compared with the ones predicted by SRICOS and modified HEC – 18 methods. In this case, SRICOS method and modified HEC – 18 predictions were in reasonable agreement with each other, however, they both were conservative.