Wood shear wall and pre-approved panels

[HofOblivion]

I have a plan check correction about using the wood shear walls and pre-approved panels such as strong walls on the same line of resistance.

The plan checker believes that "the combinations should not be used as the stiffness between them is unknown and questionable."

I believe the question to be far-fetched although I believe the question to be somewhat valid.

Am I wrong here?

 

[Shotzie]

Could you run the calculations to show that the stiffness of the two are similar (if they in fact are)? There are drift and allowable loads given in the strong wall ICC reports, could you calculate the stiffness from there? It might be worth picking up the phone and calling Simpson (assuming strong walls) and asking them if they've encountered this question before.

 

[jdgengineer]

We typically do as Shotzie suggests and distribute load to elements based on their relative stiffness. I'm not confident it's an entirely accurate representation of force distribution due to widely unknown stiffness of wood shearwall (extra nails, sheetrock, wall above and below windows are all typically neglected) but I feel it's as good as we can do with the tools currently available. The assumption that all single-family residences are flexible diaphragms is likely a bigger flaw in logic in my opinion.

 

[jayrod12]

It would be a stiffness distribution since I assume the double top plate would be continuous even over the strong wall, therefore the actual deflection of them would be the same.

 

[msquared48]

If the strong wall takes more load per foot than the wood shear wall per foot, then either upgrade the wood shear wall nailing to match the strong wall, or eliminate the other shear walls. The strong wall is likely to suck up most of the load anyway based on stiffness.

Personally, I do not know what the reviewer is talking about, because for shorter walls, the nailing has to be increased to get the same load, all based on the h/d ratios anyway. What's the difference?

Mike McCann, PE, SE (WA)

 

[HofOblivion]

It seems like the stiffness check approach is I need to do. If the initial design load is within 5% of the stiffness based re-evaluated design load, then I'll consider the design to be fine.

Thank you Shotzie, jdgengineer, jayrod12, and msquared48.