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NDS 2005 shear values

NDS 2005 shear values

NDS 2005 shear values

(OP)
When designing wood shear walls, I usually take the base shear per wall and multiply by 0.7 or divide by 1.4 to get ASD.
Using Table 4.3A wood-frame shear walls in the 2005 NDS (I don't have the 2012 yet, its on its way), footnote 1 refers to section 4.3.3 to determine ASD allowable unit shear capacity. That section calls for dividing by the ASD reduction factor of 2.0 Why is it not 1.4?

Could someone explain please.

RE: NDS 2005 shear values

The tables are based on nominal capacities, so dividing by 2 is a factor of safety and multiplying by phi is reducing the strength based on the behavior of the failure. It's similar in the AISC provisions where you may have Pn/omega for ASD and phiPn for LRFD but the method of calculating Pn is the same.

RE: NDS 2005 shear values

I agree with the response above, but I think OP's question is not a confusion between ASD and LRFD, rather between demand and capacity.
Multiplying by 0.7 (a.k.a. dividing by 1.4) is the load factor from the ASD load combinations for earthquake forces.
Dividing the tabulated nominal shear capacity by 2.0 gives you your ASD capacity, which is used for unity checks with ASD loads.
The difference is that dividing by 1.4 is something you apply to the demands, and dividing by 2.0 is something you apply to the capacity.

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