Civil Engineering Reference
In-Depth Information
1
2
2
"
18
"
13
"
1
2
2
"
18
"
Figure 11.8
SOLUTION
Is it a slender column? (ACI 10.13.2)
k
u
r
(1.3)(12)(17.5)
(0.3)(18)
50.55
22
Yes
Does the bending moment between the column ends exceed the maximum end moment by more
than 5%? (ACI Equation 10-19)
r
(12)(17.5)
35
35
0.3
18
38.88
P
u
f
600
(4)(18)
2
c
A
g
51.44
No
Note that the axial loads and moments have been factored, but since wind loads are involved
which have not been reduced by a directionality factor, smaller values may be used as obtained
with a load factor of 1.3 instead of 1.6 for wind as described in ACI Section 9.2.1(b). After this is
done, the following values are assumed to result:
P
u
544 k
M
2
ns
97.5 ft- k
M
2
s
90 ft- k
Calculating the Magnified Moment
s
M
s
M
2
s
1
P
u
0.75
P
c
s
M
s
(ACI Equation 10-18)
90
162 ft- k
16,000
(0.75)(48,000)
1
162
Note:
s
90
1.80
2.50
there is no danger of the frame becoming unstable
under gravity loads alone [ACI 10.13.6(c)]
