online_scour_froehlich 1989:  Calculation of abutment scour using the Froehlich 1989 equation   


Formula:

Fr = v /(gya)1/2

(ys / ya) = 2.27 K1 K2 (L' / ya)0.43 Fr 0.61 + 1


[ SI Units (metric):  ys, ya and L' in m ]
[ U.S. Customary Units:  ys, ya and L' in ft ]
[ Fr = Froude number; g = gravitational acceleration ]


Reference:

Evaluating Scour at Bridges,
FHWA Hydraulic Engineering Circular No. 18,
Fifth Edition, 2012.



DESCRIPTION      [Sample Input]     [Main page]

To determine the abutment scour depth ys, the calculator requires the following information:

  • Average depth of flow on the floodplain ya, in m (or ft).

  • Mean flow velocity directly upstream of the embankment v1, in m/s (or fps).

  • Length of active flow obstructed by the embankment L' , in m (or ft).

  • Angle of embankment with flow θ , in m (or ft).

Fig. 1  Abutment shapes.

  • Abutment shape (Fig. 1), to determine the shape coefficient K1.

      K1 = 0.7 for spill through.

      K1 = 1.00 for vertical wall.

      K1 = 0.82 for vertical wall with flared wingwalls.

  • Angle of embankment to the flow, to determine the coefficient K2 = (θ/90)0.13

      θ < 90o if embankment points downstream

      θ > 90o if embankment points upstream


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