________________________________________________________________________
PROBLEM (11.18) Redo Prob. 11.17 for the case in which the length of the column is L =
20 in. and the maximum load permissible load equals P = 30 kips.
SOLUTION
Refer to Solution of Prob. 11.17. Now we have 0.7(20) 14 .
e
Lin
=
=
and P. Equation (11.5): 3(30) 90
cr kips==
232
4336
64 64(90 10 )(14) , 1.05
.
(30 10 )
cr e
PL
ddin
E
ππ
×
== =
×
and
14 53.5 73.4
1.05 4
e
L
r==<
Euler formula does not apply.
Apply Johnson formula, Eq. (11.14):
212
2
2( )
ye
c
y
L
P
dE
σ
πσ π
=+ 212
23
90 55(14)
2[ ]
55 (30 10 )
ππ
=+
××
or
1.493 .di=n
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