Civil Engineering Reference
In-Depth Information
flexural cracking). Tables 3-2 and 3-3 give the minimum and maximum number of bars in a single layer for
beams of various widths; selection of bars within these limits will provide automatic code conformance with
the cover and spacing requirements.
Table 3-2 Minimum Number of Bars in a Single Layer (ACI 10.6)
BAR
BEAM WIDTH (in.)
SIZE
12
14
16
18
20
22
24
26
28
30
36
42
48
No. 4
2
2
3
3
3
3
3
4
4
4
5
5
6
No. 5
2
2
3
3
3
3
3
4
4
4
5
5
6
No. 6
2
2
3
3
3
3
3
4
4
4
5
5
6
No. 7
2
2
3
3
3
3
3
4
4
4
5
5
6
No. 8
2
2
3
3
3
3
3
4
4
4
5
5
6
No. 9
2
2
3
3
3
3
3
4
4
4
5
5
6
No. 10
2
2
3
3
3
3
3
4
4
4
5
5
6
No. 11
2
2
3
3
3
3
3
4
4
4
5
5
6
The values in Tables 3-2 are based on a cover of 2 in. to the main flexural reinforcement (i.e., 1.5 in. clear
cover to the stirrups plus the diameter of a No. 4 stirrup). In general, the following equations can be used to
determine the minimum number of bars n in a single layer for any situation (see Fig. 3-2):
b
w
−
2(c
c
+
0.5d
b
)
n
min
=
+
1
s
where
⎛
⎜
⎞
⎟ −
⎛
⎜
⎞
⎟
40, 000
f
s
4,000
f
s
s
=
15
2.5c
c
≤
12
Table 3-3 Maximum Number of Bars in a Single Layer
BAR
BEAM WIDTH (in.)
SIZE
12
14
16
18
20
22
24
26
28
30
36
42
48
No. 4
5
6
8
9
10
12
13
14
16
17
21
25
29
No. 5
5
6
7
8
10
11
12
13
15
16
19
23
27
No. 6
4
6
7
8
9
10
11
12
14
15
18
22
25
No. 7
4
5
6
7
8
9
10
11
12
13
17
20
23
No. 8
4
5
6
7
8
9
10
11
12
13
16
19
22
No. 9
3
4
5
6
7
8
8
9
10
11
14
17
19
No. 10
3
4
4
5
6
7
8
8
9
10
12
15
17
No. 11
3
3
4
5
5
6
7
8
8
9
11
13
15
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