Page 163 - Structural Steel Designers Handbook AISC, AASHTO, AISI, ASTM, and ASCE-07 Design Standards

Brockenbrough_Ch03.qxd 9/29/05 5:05 PM Page 3.95

CONNECTIONS

CONNECTIONS 3.95

.
where b = 55 −129 = 211. in
.
2
a = 16 1 . 2 −5 5 = 53 1
.
. in
p = 3 in
n = 7
Thus,
π
3
.
.
2
p = 6 ×+ × 211 + × 531 = 503 in
.
eff
7
Using p eff in place of p, and following the AISC procedure,
b = b = 211 in
.
b′ = 211 − 10 . = 161. in
.
2
++ 0 47 5 5 .
 44 . − 
.
531 125
.
148 531 263)
a = min ,. , . × 211 = min( . , . , . = 149 in
 2 
.
+ .
a′ = 149 05 199 in
= .
b′
ρ = = 081
.
a′
.
δ =− 106 = 079
.
1
503
.
Note that standard holes are used in the column flange.
.
.
t = 444 × 291 . ×161 = 0 798 in
.
c
503 × 65
.
.
α ′ = 1    0 798  2 −  1  =−0 595
.
.
079 ×181   207  
.
.
Since α′ < 0, use α′ = 0.
T d = 29.1 kips/bolt > 15.7 kips/bolt OK
When α′ < 1, the bolts, not the flange, control the strength of the connection.
3.7.4 Vertical Brace Connections Using Extended Single Plate
It often makes sense when designing the lateral force resisting system for a building to design a
moment frame along the strong axis of the columns and a braced frame along the weak one. This can
lead to a situation in which stiffeners are required in the column webs due to the moment connections,
and the weak-axis beam and bracing connections need to be kept clear of the column flanges for erec-
tion. In such cases the connections to the columns are often made using extended single-plate con-
nections. The uniform force method is particularly well suited to analyzing this type of connection.
By moving e c from the center of the column to the center of the bolt group in the single-plate con-
nections, the eccentricity which would normally have to be considered in the bolt group can now be
taken as a couple, H c , producing a more efficient connection. See Figs. 3.53 and 3.54. The uniform
force method equations can now be applied to the connection, with the forces normally associated
with the column now associated with the single-plate connection. As long as the forces derived from
the uniform force method are used without the introduction of ∆V b or a change in α or β, no moments
will need to be considered in any of the connection interfaces or within the plates. However, the
single-plate connector must now be checked to transfer H c as a horizontal shear. If α or β is varied,
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