ASD/LRFD Manual - American Wood Council
ASD/LRFD Manual - American Wood Council
ASD/LRFD Manual - American Wood Council
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26 M4: SAWN LUMBER<br />
Column Capacity – y-axis<br />
F<br />
0.822E<br />
=<br />
min<br />
cE 2<br />
( <br />
e<br />
/ d<br />
y)<br />
( )<br />
( 144/5.5) 2<br />
0.822 580,000<br />
=<br />
= 696 psi<br />
′<br />
( )<br />
2( 0.8)<br />
1+ 696/1,000<br />
C =<br />
x<br />
Py<br />
P′ =<br />
( )<br />
( )<br />
⎛1+ 696/1,000 ⎞ 696/1,000<br />
−<br />
⎜<br />
−<br />
2 0.8 ⎟<br />
⎝<br />
⎠ 0.8<br />
= 0.556<br />
( 0.556)( 41.25)( 1,000)<br />
= 22,952 lb<br />
Bending Member Capacity Tables<br />
where:<br />
where:<br />
The general design equation for flexural bending is:<br />
M′ ≥ M<br />
M = moment due to design loads<br />
M′ = allowable moment capacity<br />
The general design equation for flexural shear is:<br />
V′ ≥ V<br />
V = shear force due to design loads<br />
V′ = allowable shear capacity<br />
2<br />
Example M4.6-3: Application – structural<br />
lumber<br />
Species: Douglas Fir-Larch<br />
Size: 2 x 6 (1.5 in. by 5.5 in.)<br />
Grade: No. 2<br />
C F : 1.3 (size factor)<br />
C r : 1.15 (repetitive member factor)<br />
F b : 900 psi<br />
F v : 180 psi<br />
E: 1,600,000 psi<br />
A: 8.25 in. 2<br />
S: 7.56 in. 3<br />
I: 20.80 in. 4<br />
Moment Capacity<br />
C M ′ = F C C S<br />
r b F r<br />
Shear Capacity<br />
= ( 900)( 1.3)( 1.15)( 7.56)<br />
= 10,172 lb -in.<br />
2<br />
V ′ = F′<br />
v<br />
A ⎛ ⎜ ⎞<br />
⎟<br />
⎝ 3 ⎠<br />
⎛ 2 ⎞<br />
= ( 180)( 8.25)<br />
⎜ ⎟<br />
⎝ 3 ⎠<br />
= 990 lb<br />
Flexural Stiffness<br />
EI = (1,600,000)(20.80) = 33 × 10 6 lb - in. 2<br />
<strong>American</strong> <strong>Wood</strong> <strong>Council</strong>
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