Civil Engineering Reference
In-Depth Information
7.5
For the cantilever beam shown, determine the point where two bars can be cut off from the standpoint of the calcu-
lated moment strength
M
n
of the beam.
f
y
60,000 psi,
c
f
3000 psi. (
Ans.
9.96 ft from free end.)
16"
3 @3" = 9"
3
2
"
3
2
"
3"
#3
stirrups
4 #9
w
u
= 5 k/ft
32"
29"
12'
In Problems 7.6 to 7.9 determine the development
lengths required for the tension bar situations described,
(a) using ACI Equation 12-1 and assuming
K
tr
0, and
(b) using ACI Equation 12-1 and the calculated value
of
K
tr
.
7.7
Uncoated bars in normal-weight concrete.
A
s
re-
quired
4.25 (
Ans.
43 in., 27 in.)
f
y
=
60,000 psi
f'
c
= 4000 psi
26"
#4 stirrups
@ 6" o.c.
6 #8
3"
3"
3"
3"
3"
3"
7.6
Uncoated bars in normal-weight concrete.
A
s
re-
quired
2.84 in.
2
7.8
Epoxy-coated bars in lightweight concrete,
A
s
re-
quired
2.62 in.
2
f
y
=
60,000 psi
f'
c
= 3000 psi
f
y
=
60,000 psi
f'
c
= 4000 psi
30"
24"
#3 stirrups
@ 8" o.c.
#3 stirrups
@ 7" o.c.
3 #9
3 #9
3"
3"
3"
4"
4"
3"
3"
3"
3"
3"
