Civil Engineering Reference
In-Depth Information
P
n
P
n
= 1482 k,
M
n
= 0
Compression failure zone
P
n
= 623.7 k,
M
n
= 521.8 ft-k
Compressive
loads
P
bn
= 504.4 k,
M
bn
= 559.7 ft-k
Tension failure zone
M
n
P
n
= 0,
M
n
= 297 ft-k
Tensile
loads
Axial
tension
Figure 10.8
Interaction curve
for the column of Figure 10.4.
Notice these are nominal values.
P
n
= 360 k,
M
n
= 0
the column of Figure 10.4, and then the values of
P
n
and
M
n
were determined. The results
were plotted at the bottom of Figure 10.8 and were connected with the dashed line which
is labeled “tensile loads.”
Because axial tension and bending are not very common for reinforced concrete
columns, the tensile load part of the curves is not shown in subsequent figures in this chap-
ter. You will note that the largest tensile value of
P
n
will occur when the moment is zero. For
that situation, all of the column steel has yielded, and all of the concrete has cracked. Thus
P
n
will equal the total steel area
A
s
times the yield stress. For the column of Figure 10.4
P
n
A
s
f
y
(6.0)(60)
360 k
Round columns. (Courtesy of Economy Forms Corporation.)
