Page 314 - Handbook of Structural Steel Connection Design and Details

Partially Restrained Connections

Partially Restrained Connections 299

2. Check net area fracture versus gross section yielding of the girder flange by
AISC (2005) Section F13. (Note: Y (F /F ) 50/65 0.76 < 0.8 so Y 1.0;
t y u t
for the W 27 94, b 9.99 in, t 0.745 in, and d 27.7 in; holes for 1-in
f f
bolts assumed as 1.125 in in diameter):
F u A fn 5 s65ds9.99 2 2.25ds0.745d 5 374.8.0 kips
Y t F y A fg 5 s1.0ds50ds9.99ds0.745d 5 372.1 kips

Thus the gross section governs (F A > Y F A ) by these computations, but
u fn t y fg
in reality either of them could control as the two values are very close to one
another.
3. Check local buckling:
Flange:

b E
a b 5 6.70 # 0.30 5 7.2, ok
t BF y
Web:
h E
aa b 5 49.5 # 3.14 5 75.6, ok
t w BF y
4. The maximum unbraced length (L ) for seismic design is
b
L b , 2500 r y F y 5 2500s1.87d>50 5 93.5 in 5 7.8 ft, say 7.5 ft for design
5. Estimate number of A490X 1-in bolts required for shear. Note that a 1.25 fac-
tor is used here to increase the number of bolts, as the design moment at the
column face will be increased by the shear acting at the critical section:

1.25s17585d
1.25M pr
n $ 5 5 13.3, say 14 bolts
v sddsF v A b d s1.00ds27.7ds0.79 3 75d
a. Determine the beam hinge location (S ). The hinge will be located below the
h
last row of bolts away from the column face. Assuming a bolt spacing and
end distance of 3 in and a distance between the first row of holes and the col-
umn of 4 in, the hinge will be located at 25 in from the column face.
b. Compute the shear in the beam (V ) at the location of the plastic hinges (Fig.
h
4.14). The actual distance between the hinges (L ) is the total centerline dis-
v
tance minus the column depth minus 2 times the distance to the plastic
hinge:
L v 5 L 2 d c 2 2S h 5 336 2 17.1 2 2s25d 5 268.9 in

The shear will be computed based on assuming a w 1.2 d
0.5 L
u
1.2(0.75)
0.5(0.75) 1.275 kip/ft. Thus:
s2ds17,585d 1.275s268.9d
2M pr w u L v
V h 5 1 5 1 5 145.1 kips
L v 2 268.9 2s12d

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