Civil Engineering Reference
In-Depth Information
2.
The diameter of stirrups may not be less than 0.042 times their spacing, and stir-
rups smaller than #10 may not be used. (ACI Section 11.6.6.2.)
3.
Maximum yield stresses
f
yv
or
f
y
420 MPa.
(ACI Section 11.6.3.4)
Example 15.2 illustrates the design of the torsional reinforcing for a member using SI
units.
EXAMPLE 15.2
c
Design the torsional reinforcing for the beam shown in Figure 15.15, for which
28 MPa,
f
y
420 MPa,
V
u
190 kN,
T
u
30 kN-m, and
A
s
required for
M
u
is 2050 mm
2
. Assume #13 stirrups
and a clear cover equal to 40 mm.
f
SOLUTION
(1) Is torsion reinforcing necessary?
A
cp
(350)(650)
227 500 mm
2
p
cp
(2)(350
650)
2000 mm
c
A
cp
(227 500)
2
2000
f
p
cp
(0.75)
28
[ACI Section 11.6.1(a)]
12
12
8.558
10
6
N
mm
8.56 kN
m
30 kN
m
Torsion reinforcing is required
(2) Compute sectional properties
With 40 mm clear cover and #13 stirrups (diameter
12.7 mm)
40
12.7
2
x
1
350
(2)
257.3 m
40
12.7
2
y
1
650
(2)
557.3 mm
A
oh
(257.3)(557.3)
143 393 mm
2
A
o
0.85
A
oh
(0.85)(143 393)
121 884 mm
2
y
1
650 mm
x
1
350 mm
Figure 15.15
