sm9 59

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PROBLEM (9.59) Member ABC of the frame shown in Fig. P9.59 is made of a C 6 x 8.2 steel
channel (see Table B.10) having y
σ
=36 ksi. Determine the largest load P that can be
supported by the member, based upon a factor of safety of
s
n = 1.2. Neglect the effect of direct shear.
SOLUTION
PFM BDA 357.2:0 ==
∑
PRF Axx 667.1:0 ==
∑
PRF Ayy 667.0:0 ==
∑
Maximum stress at B occurs at the bottom of channel:
3
36 10 1.667 4(1.408)
1.2 2.4 0.692
BNMc P P
AI
σ
−×
==−=−
or
PP 139.8659.01030 3−=×−
from which
max 4.03Pkips=
6 ft
P
1.92 in.
A
C
B
-0.667
P
V
x
C6x8.2
4P
x
M
R
Ay 4 ft
45o
4
0.692 .
I
in=
z
y
2
2.4 .Ain=
P
R
Ax
F
BD
N
x
1.667P
0.512 in.