Wednesday, September 16, 2009

Re: Steel straps on wood shear walls

As for "definitive references" there are none that I know of.  But conceptually it should not matter which side of the shear panels you place a structural element.  The forces are transferring directly from the shear panels into the strap--it's not as if you have the panels acting as a "shim" between the framing and the strap if you put the strap on the outside face of the panels, in that you are not trying to transfer forces from the far side of the shear panel into the strap.
 
You must have tight-fitting blocks to act in compression and the strap must be taught. 
 
You may wish to consider the possibility that panel nailing into the blocks IN ADDITION to the strap nailing could easily split the blocks, and consider that nails through the strap can serve double-duty as also connecting the panels to  the blocking. 
 
Another "mistake" is to require nails in EVERY hole in the strap, which can amount to 2-inch nail spacing (in the case of a Simpson CS-16, for example)--if your panel edge-nail spacing is two inches, then you need this, but otherwise it's likely to cause splitting in the wood and make your design look like it's over-kill (which it would be in that case).
 
Thor Matteson, SE
 
 
 
 
From: Chuck Utzman <chuckutzman@gmail.com>
To: seaint@seaint.org
Subject: Re: Steel straps on wood shear walls


Around here, over the shear ply is SOP. Underneath, structural
observation is more complicated.

Jim Wilson wrote:
> Is there a definitive reference stating that steel straps are okay to
> be placed over wall sheathing and not directly to the studs before the
> sheathing is installed?  I've googled it, I've called Simpson and I've
> tried to look to the APA but I can only find indirect statements about it.

> Simpson does mention that different nail sizes can be used for the
> different installation methods.  That isn't generic enough for the
> condition.

> Thanks,
> Jim Wilson, PE
> Stroudsburg, PA