Civil Engineering Reference
In-Depth Information
20 in
22 in
24 in
FIGURE 7.28
Column section of example 7.5.
Example 7.5: Design
This example is intended to increase the axial load capacity of a rectangular column
by 20% by means of increasing confinement. The following data describe the column,
Figure 7.28.
Height
24 in.
610 mm
Width
20 in.
508 mm
Clear cover
1 in.
25 mm
r
c
1.2 in.
30.5 mm
f
c
6.0 ksi
41.39 MPa
t
f
0.015 in.
0.381 mm
E
f
33,000 ksi
2 2 7. 67 G P a
ε
fu
0.0167
0.0167
f
yt
60 ksi
413.93 MPa
Tie spacing
18 in.
4 5 7. 2 m m
Tie diameter
#3
9.5 mm
Longitudinal bars
10 #10
10
ϕ
32 mm
f
y
60 ksi
413.93 MPa
Solution:
ε=ε= ×
C
*
0.95
0.0167
=
0.0159
fu
E u
[
]
φ
P
P
=
0.80.650.856(2420101.27)
×
× ××−× +××
60
10
1.27
=
1635.52 kips
existing
1635.52
k
1.2
1962.62k
φ
=
×=
nreq d
'
(
)
=φ −+ =× ×
0.80.85(
fA AAf
)
0.8
0.65
0.85
× ×−
f
24
20
12.7
cc
g
st
sty
cc
+
12.760
×
f
=
7.584 ksi
cc
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