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American Steel Design
Section 2
2-46
Actual Stress Calculation:
Axial stress (f
a
) = 14.02 / 10.6 = 1.323 ksi.
The critical moment occurs at the end node of the beam. So we use
the AASHTO equation 10.42 in section 10-36 to calculate the
design ratio.
Actual bending stress = 57.04 x12/56.5 = 1.001 x 12 = 12.115 ksi
(KL/r)
z =
1x60/6.5= 9.231
() ()
22
22
*29000
1584.398
. . 2.12 9.231
ez
E
F
FS KLr
ππ
===
From table 10-36A, C
mz
= 0.85
So the design ratio is
Equation 10-42
1.323 0.85*12.115
0 0.602
1.323
16.149
1- 19.8
1
1
1584.398
'
'
my by
amxbz
a
a
a
bz
by
ez
ey
Cf
fCf
F
f
f
F
F
F
F
++ =+ +=
⎛⎞⎛⎞ ⎛ ⎞
−
⎜⎟
−
⎜⎟⎜⎟
⎜⎟
⎝⎠
⎝⎠
⎝⎠
for the end section, Equation 10-43
1.323 12.115
0 0.689
0.472 0.472 * 36 19.8
by
abz
ybzby
f
ff
FF F
++= + +=
The value calculated by STAAD is 0.69