Civil Engineering Reference
In-Depth Information
Maximum spacing to provide minimum
A
v
of stirrups:
A
v
f
y
0.75
(2)(0.11)(60,000)
(0.75
s
4000)(15)
18.55 in.
c
b
w
f
s
A
v
f
y
50
b
w
(2)(0.11)(60,000)
17.6 in.
(50)(15)
For convenience, theoretical spacings are calculated at different points along the span and are
listed in the following table:
Distance from
Theoretical
V
s
V
u
V
c
A
v
f
y
d
V
s
V
u
face of support
s
(in.)
(ft.)
(lb.)
(lb.)
0 to
d
1.875
73,800
55,709
5.33
2
72,000
53,309
5.57
3
57,600
34,109
8.71
4
43,200
14,909
Maximum of
11.25
Spacings selected:
1 @ 3 in.
3 in.
6 @ 6 in.
36 in.
4 @ 9 in.
36 in.
symmetric about
L
As previously mentioned, it is a good practice to space stirrups at multiples of 3 or 4
in. on center. As an illustration, it is quite reasonable to select for Example 8.3 the follow-
ing spacings: 1 @ 3 in., 6 @ 6 in., and 4 @ 9 in. In rounding off the spacings to multiples
of 3 in., it was necessary to exceed the theoretical spacings by a small amount near the
end of the beam. However, the values are quite close to the required ones, and the overall
number of stirrups used in the beam is more than adequate.
In Example 8.4, which follows, the value of
V
c
for the beam of Example 8.3 is com-
puted by the alternate method of Section 11.3.2.1 of the Code.
EXAMPLE 8.4
Compute the value of
V
c
at a distance 3 ft from the left end of the beam of Example 8.3 and Figure
8.11 by using ACI Equation 11-5.
c
2500
w
V
u
d
M
u
c
b
w
d
V
c
1.9
f
b
w
d
3.5
f
