Conceptual Model of bed Shear Stress in Single-Span Rip rap-Protected Bridges

Vertical bridge abutments along the river cause three-dimensional flow and can cause scour at the bridges and eventually damage the bridge. In cases where deep foundations are not used, the level of vulnerability increases. These abutments are often used for single-span bridges and scour countermeasures such as using riprap apply. The purpose of the current study is to present a conceptual model of localized bed shear stresses applied to heterogeneous bed roughness at bridge opening. The adaptation of the flow with the change in roughness of the rock material compared to the bed material results in increased bed shear stress in the unprotected bed material and eventually the contraction scour depth increase compare with that without rock protection.