ASD/LRFD Manual - American Wood Council
ASD/LRFD Manual - American Wood Council
ASD/LRFD Manual - American Wood Council
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<strong>ASD</strong>/<strong>LRFD</strong> MANUAL FOR ENGINEERED <strong>Wood</strong> Construction<br />
97<br />
M14.3 Shear Walls<br />
Overturning<br />
Overturning moments result from shear walls being<br />
loaded by horizontal forces. Overturning moments are<br />
resisted by force couples. The tension couple is typically<br />
achieved by a holddown. Figure M14.3-1 and the accompanying<br />
equations present a method for calculating<br />
overturning forces for a non-load-bearing wall. Figure<br />
M14.3-2 and the accompanying equations present a<br />
method for calculating overturning forces for a load-bearing<br />
wall. Overturning forces for load-bearing walls can<br />
utilize dead load as overturning restraint. To effectively<br />
resist uplift forces, holddown restraints are required to<br />
show very little slip relative to the chord (end post).<br />
Figure M14.3-2 Overturning Forces<br />
(with dead load)<br />
Unit shear = V L<br />
= v<br />
Elevation<br />
Overturning force = chord force = Vh L<br />
Figure M14.3-1 Overturning Forces<br />
(no dead load)<br />
Overturning moment = Ph<br />
Dead load restraining moment* = wL2<br />
2<br />
V<br />
T<br />
L<br />
C<br />
h<br />
Net overturning moment = Ph −<br />
wL<br />
2<br />
Net overturning force – chord force = Ph −<br />
wL<br />
2<br />
L<br />
2<br />
2<br />
Ph wL<br />
= −<br />
L 2<br />
* See building code for applicable reduction to the dead load restraining moment<br />
to insure an appropriate load factor for overturning.<br />
M14: SHEAR WALLS AND DIAPHRAGMS<br />
Elevation<br />
14<br />
<strong>American</strong> Forest & paper association
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