FLOOD06847

• County: Statewide
• Basin: Statewide
• Title: Bridge Scour and Stream Instability Countermeasures
• Date: 7/1/1997
• Prepared By: Federal Highway Administration
• Floodplain - Doc Type: Educational/Technical/Reference Information

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Figure 6.4 Blue Creek Site

Row
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8m

J 1m

N

Low
Row.

Bridge Deck

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2.4m
-L
A/Mnent

Section A-A

1. Determine the velocity value, Vv (m1s).
Because the pier is located in the thalweg of the bend, C1 = 1.1.
The angle of attack, ex = 150> 50, therefore C. = 1.0.
The Toskane pad is installed so that the top of the pad is level with the bed, Ch = 1.0.
A randomly installed pad of Toskanes is selected, C; = 1.0.

Vv= (1.5)(2.5)(1.1)(1.0)(1.0)(1.0) = 4.1 m/s.

2. Calculate the adjusted structure width, b. (m).
The angle of attack, ex = 150.
Length of pier, L = 6 m.
Pier width, b = 1 m.

b. = Lsina+bcosa = 6sin(150)+1cos(150)= 2.5 m

3. From Figure 6.2 or the design equation calculate the equivalent spherical diameter, Du,
for Vv = 4.1 mls and b. = 2.5 m.

(1.4)Ou = 0.255(4.1}12.5 I 9.806 =) Du = 0,377 m = 377 mm

Using standard sizes, a 100 kg Toskane unit (Du = 430 mm) is selected. The ratio balDu
= 2.5/0.43 = 5.8 < 21, therefore the size is acceptable.

6.9