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Ga (apparent shear stiffness) when wood shear walls have double sided sheathing?

Ga (apparent shear stiffness) when wood shear walls have double sided sheathing?

Ga (apparent shear stiffness) when wood shear walls have double sided sheathing?

(OP)
I haven't been able to find a specific wood shear wall deflection example for a double sided wood shear wall, so I'm wondering what others would use in this scenario. The NDS-SDWPS Table 4.3A gives values for Ga, the apparent shear stiffness, of different wood shear wall nailing configurations. The Ga value is then used in calculating the shear deflection and nail slip portion of the shear wall deflection.

If I had a 7/16" OSB (Sheathing Grade) with 8d nails at 6" o.c. edge nailing, my Ga value would be 15. Now if i used the same nailing pattern and sheathing on both sides of the wall, would my Ga value be doubled equaling 30, or could I still only use 15?

I'm pretty sure I can double the Ga value based on my understanding of what it represents.

RE: Ga (apparent shear stiffness) when wood shear walls have double sided sheathing?

I'm pretty sure it should be doubled. Though I don't have the SDPWS in front of me right now.

There are double sided shear walls given in the NDS tables, right? I know I've seen them somewhere. Maybe the IBC.... I would just take one of those double shear walls with a given Ga value and make sure I could back out the number in the table with my hand calculations. Or, just compare it to a single wall with the same sheathing and nail patterns.

RE: Ga (apparent shear stiffness) when wood shear walls have double sided sheathing?

If you simply doubled the tabular sheer values, would you not be taking credit for the same interior ribs (upper & lower 2x4s and interior vertical studs) twice? Granted, in sheet, the single outer "wall" member is contributing most of the resistance to sheet forces, but not all. (Don't have that reference, so I don't know how they developed the equations and tests verifying their table. )

RE: Ga (apparent shear stiffness) when wood shear walls have double sided sheathing?

The NDS allows you to add GA from both sides if the material is the same. See 2015 SDPWS SECTION 4.3.3.3

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