φ n = φ0.6FuAnv + FyAgt]
R
[
AISC LRFD Eq. J4-3b
φ n = 0.75(0.5) [(0.6)(58)(2 x 11) + (36)(17.2)] = 519 k (2309 KN) > 238 k (1058 KN)
R
Buckling of plate:
Buckling capacity of the brace = AgFcr = φPn / φ = 87 kips / 0.85 = 102 kips (454 KN) (buckling strength
c
c
determined previously)
4000t 3 f y
4000(1 / 2) 3 36
= 0.90
= 218 kips (970KN) > 102kips (457 KN) , OK
0.90
lc
12.4
Out-of-plane strength of plate: The bracing member can buckle both in and out of plane due to the round section
used. For out-of-plane buckling the gusset plate must be able to accommodate the rotation by bending. The brace
shall terminate on the gusset a minimum of two times the gusset thickness from the theoretical line of bending which
is unrestrained by the column or beam joints. This ensures that the mode of deformation in the plate will be through
plastic hinging rather than torsional fracture.
1 inch = 25.4 mm
H3-58
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