Page 159 - Handbook of Civil Engineering Calculations, Second Edition

1.142 STRUCTURAL STEEL ENGINEERING AND DESIGN

FIGURE 37

The case of no-stiffeners corresponds to k 5.
2. Check the original assumptions for doubling the shear strength
To double the shear strength, I k 2 5 10. Then in AISC Eq. A-G3-4,
5
k 5 + 10
(a/h) 2
This implies a/h 1.0 or a k; thus, the clear distance between transverse web stiffeners
a h 56 in. (142.2 cm). Checking the original assumption we obtain

h 56 in. k 10
128.9 > 234 234 123.3 o.k.

t w 0.44 in. F y 36
3. Design the stiffener, trying a pair of stiffener plates
Stiffener design can be performed thusly. Because tension field action is not utilized, the
3
equation I st at w j must be satisfied, where
2.5
j – 2 0.5
(a/h) 2
2.5
j – 2 0.5
1 2
3
4
4
I st 56 in. (0.44 in.) 0.5 2.34 in (97.4 cm )
Try a pair of stiffener plates, 2.5 in. 0.25 in. (6.35 0.635 cm), as in Fig. 38. The mo-
ment of inertia of the stiffener pair about the web centerline
0.25 in. × (5.44 in.) 3
4
4
4
I st 3.35 in. > 2.34 in. 4 o.k. (139.4 cm > 97.4 cm ) o.k.
12