Civil Engineering Reference
In-Depth Information
In Examples 10.3 to 10.5, reinforcing bars are selected for three columns. The values
of
k
n
c
A
g
c
A
g
h
P
n
/
f
and
R
n
P
n
e
/
f
are computed. The position of those values is lo-
cated on the appropriate graph, and
g
is determined and multiplied by the gross area of
the column in question to determine the reinforcing area needed.
EXAMPLE 10.3
The short 14
20-in. tied column of Figure 10.17 is to be used to support the following loads and
moments:
P
D
125 k,
P
L
140 k,
M
D
75 ft-k and
M
L
90 ft-k. If
4000 psi and
f
y
60,000 psi, select reinforcing bars to be placed in its end faces only using appropriate ACI column
interaction diagrams.
c
f
SOLUTION
P
u
(1.2)(125)
(1.6)(140)
374 k
P
n
374
0.65
575.4 k
M
u
(1.2)(75)
(1.6)(90)
234 ft- k
M
n
234
0.65
360 ft- k
e
(12)(360)
575.4
7.51
15
20
0.75
Compute values of
k
n
and
R
n
P
n
575.4
(4)(14
20)
0.513
k
n
c
A
g
f
P
n
e
(575.4)(7.51)
(4)(14
R
n
c
A
g
h
20)(20)
0.193
f
2
2
"
15"
h
= 20"
b
= 14"
2
2
"
Figure 10.17
