Civil Engineering Reference
In-Depth Information
Note
x
1
and
y
1
run from
c.g. of stirrup
on one edge
to c.g. of
stirrup on
other edge
y
1
26
"
x
1
16
"
Figure 15.13
SOLUTION
(1) Is torsion reinforcing needed?
A
cp
area enclosed by outside perimeter of
concrete cross section
(16)(26)
416 in.
2
(the letter
c
stands for concrete, and the
letter
p
stands for perimeter of cross section)
p
cp
outside perimeter of the cross section
(2)(16
26)
84 in.
Torsion
T
u
can be neglected if less than
c
A
cp
416
2
84
f
p
cp
(0.75)(
4000)
97,723 in.- lb
97.72 in.- k
30
12
360 in.- k
Torsion reinforcing is required
(2) Compute sectional properties
A
oh
area enclosed by centerline of the outermost closed stirrups
Noting 1.5 in. clear cover and #4 stirrups
x
1
y
1
12.5 in.
26
(2)(1.5
0.25)
22.5 in.
16
(2)(1.5
0.25)
See Figure 15.13
A
oh
(12.5)(22.5)
281.25 in.
2
A
o
gross area enclosed by shear flow path
0.85
A
oh
from ACI Section 11.6.3.6
(0.85)(281.25)
239.06 in.
2
d
effective depth of beam
26
1.50
0.50
1.00
2
23.50 in.
p
h
perimeter of centerline of outermost closed torsional reinforcing
(2)(
x
1
y
1
)
(2)(12.5
22.5)
70 in.
