Light-Gauge Steel Shear Wall Design Values

[North2South]

Does anyone know where I can find shear design values for light-gauge shear walls for plywood sheathing that is not Structural 1. AISI 213 Cold-Formed Steel Framing - Lateral Design Table C2.1-1 and C2.1-3 only have design values for 15/32" structural 1 grade plywood. It does not provide values for rated plywood (Non Structural 1 plywood). Contractor says he cannot source Structural 1 plywood around here (South East USA). Any help would be appreciated.

 

[RobertHale]

Try looking for information related to the fasteners. Simpson has some info in C-CF-2017 pp 150. I know I have also seen some ICC-ES reports for screws that show the capacities.

Robert Hale, PE

 

[phamENG]

You can switch to OSB rated sheathing and still use the tables without the structural 1 classification. That'll probably be your best bet. APA also indicates on their website discussing when to use Structural 1 that a 1/8" increase using standard structural sheathing over what you would have specified for structural 1 typically has comparable performance. So if you can get some 19/32 plywood sheathing, it'll probably work for you. You would need to find some better references to make sure it would behave as expected in your case.

 

[North2South]

Thanks for the replies! The sheathing needed to be fire retardant treated which is why we were leaning towards plywood. I am always skeptical when I hear that a contractor "can't find it anywhere". The contractor ended up finding fire treated OSB.

I did see the APA's article where it said you can increased the thickness to get the equivalent performance. Unfortunately there was not any information to back it up and that made me a bit hesitant.

It seems bizarre that AISI would not have published values available for non-structural 1 plywood, like the NDS does.

 

[phamENG]

Shear walls are tricky things to figure with first principles and theoretical calculations. It's all about research and adapting the empirical data to design equations. NDS's business is wood, so they've tested all sorts of combinations of sheathing and wood studs. AISI's business is steel. There's some test data for use with sheathing because it's a popular choice, but they want you to buy steel products.

The fire retardant treatment does through a monkey wrench in things. APA already warns that Structural 1 availability can vary by region, so I'm sure throwing in the added treatment for fire further reduces the possible supply choices. Glad they were able to source a protect to keep your project moving.

 

[Aesur]

I'm a little late to the party here, but am curios what kind of reduction in shear you took for the FRT? I have found the values to differ significantly depending on the treatment used, from 90% strength (10% reduction) to 80% (20% reduction).

 

[North2South]

I searched 3 or 4 different FRT reductions and took the lesser value which ended up being just over 80%.