Development of New Design Guidelines for Protection Against Erosion at Bridge Abutments - Phase IV

"Reliable and safe transportation infrastructure design for flooding events is of great economical importance for state and federal agencies in charge of maintaining our roads operational. The US Midwest has experienced increasingly catastrophic flood events. Severe erosion problems were reported at many bridge sites. Two of the most encountered types of abutments used at such bridges are spill-through and wing-wall abutments. Placing riprap stone around the base of a bridge abutment, where the highest stresses generally occur, and over its erodible faces is one of the most common way to protect abutments against erosion. The present research proposes the use of a numerically-based approach to develop improved design formulas for minimum riprap stone size for protection against erosion of spill-through abutments (open channel flow conditions) and wing-wall abutments (pressurized flow due to bridge deck overtopping)."

"The formula for wing-wall abutments was presented at the most recent MATC workshop (February 2020) and was published in the J. Hydraulic Research (Wu et al., 2020). We intend to submit the new multi-parameter design formula we are proposing for spill-through abutments in straight and curved channels to the J. Hydraulic Engineering. We will also give presentations at the MATC research seminars. We will start working with the Transportation Research Board TRB-AFB60 committee such that the new design formulas will be considered for adoption in future Tech Briefs updates of HEC-23. We will present our formulas and findings to the USDOT Fed. Highway Adm. TFHRC (Dr. Kornel Kereny) and ask for input to further streamline and clarify our recommendations and proposed novel methodologies such that they are easily applicable by engineers in charge of bridge erosion protection. We will also contact several DOTs in the Midwest that are part of MTC for further omments. Once adopted by state and federal agencies in charge of maintaining operational our bridges, the present research will increase the efficiency of scour protection measures for two main types of abutments used especially at small bridges in the US. "

"Information inferred from the proposed new simulations of flow past spill-through abutments placed over the floodplain of a curved channel will be used to determine the limitations of existing design formulas recommended in HEC-23 and to gain a better understanding of the effects of the main nondimensional geometrical variables on the bed shear stress distributions over the riprap layer. The main outcome of the research is expected to be a multi-parameter design formula that can be applied to determine the critical Froude number for riprap shear failure for cases when spill-through abutments are placed in either straight or curved channels. Simulations of flow in a channel containing wing-wall abutments at its two sides under bridge overtopping conditions will allow understanding how the critical Froude number changes once the flow becomes pressurized at the bridge site. This information will be used to develop a riprap design formula for such cases. Better design of scour prevention measures will result in less failure of bridges during natural disasters (e.g., floods). As such the project will enhance the safety of our transportation infrastructure that is also one of USDOT’s strategic goals."

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