Civil Engineering Reference
In-Depth Information
For 22-ft interior beam (with 18-ft slab width)
1
12
(12
18)(6)
3
3888 in.
4
I
s
15,870
3888
4.08
5.36
3.34
(2)(4.08)
4
m
Avg.
4.21
s
ratio of length of continuous edges to total perimeter
62
80
0.78
ratio of long to short clear span
22
1
12
18
1
12
1.24
(e)
Thickness limits by Code Section 9.5.3
n
22.0
15
12
20.75 ft
As
m
2.0, use ACI Equation 9- 13.
f
y
200,000
n
0.8
h
36
9
0.8
60,000
200,000
(12)(20.75)
5.81 in.
k
36
(9)(1.24)
h
not less than 3.5 in. (as per ACI Section 9.5.3.3(c))
Try
h
6 in. (shear checked later)
3.
Moments for the short-span direction centered on interior column line:
w
u
(1.2)(100)
(1.6)(120)
312 psf
M
o
(
w
2
)(
n
)
2
8
(0.312)(22)(16.75)
2
8
241 ft- k
(a)
Dividing this static design moment into negative and positive portions, as per Section
13.6.3.2 of the Code:
negative design moment
(0.65)(241)
157 ft- k
positive design moment
(0.35)(241)
84 ft- k
(b)
Allotting these interior moments to beam and column strips, as per Section 13.6.4 of
the Code:
2
22
1
18
1.22
1
in direction of short span
3.34
1
2
1
(3.34)(1.22)
4.07
The portion of the interior negative moment to be resisted by the column strip, as per Table
16.3 of this chapter, by interpolation is (0.68)(
157)
107 ft-k. This
107 ft-k is allotted 85%
