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RE: chat thread on gyp shear and steel

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Dave,
If this originated from the discussion of the SureBoard then you must remember that this is not gypsum board directly against steel studs. It is a gypsum material laminated to a 20 or 22 gauge steel plate that is then screwed to the steel studs. In this case and I am not sure, I believe that there is a flange on the steel plate that secures the steel to the studs rather than to consider bending in the screw based on the thickness of the gypsum.
Take a look at the Hardy Panel which might be similar by considering the steel plate over the studs for shear. I do agree that thre brittleness of the screw is the one issue that caused the latest code to abandon 16-gauge studs for shearwalls as the steel was too stiff and caused the screws to shear.
The capacity of the plywood wall (and I assume the gypsum might have some similar response) was in the buckeling of the studs under load.
Dennis
-----Original Message-----
From: David Merrick [mailto:mrkgp(--nospam--at)winfirst.com]
Sent: Monday, October 07, 2002 10:48 AM
To: SEAINT
Subject: Fw: chat thread on gyp shear and steel

I passed on the seaint discussion for "steel bracing and gyp board" to my brother Dan Merrick and got this response.
 
David Merrick, SE
 
----- Original Message -----
Sent: Monday, October 07, 2002 6:49 AM
Subject: Re: chat thread on gyp shear and steel

As far as I know, there really is no way to determine the design capacity of a shear wall from testing that considers strength and ductility. The only test procedures that I am aware of (ASTM) have a test method and no way to calculate a capacity from the result. I am a firm believer that Gyp has capacity but don't know how to determine what capacity. My best shot was the 1997 tests at SJSU http://www.engr.sjsu.edu/dmerrick/shearwalls/ . Dr. McMullin ( he needs to update his website http://www.engr.sjsu.edu/mcmullin/ )is running some more wall tests (with my help) right now to extend the earlier work. I would think that gyp on steel studs would work fine but the variety of available screws and the brittleness of screws would be a concern. McMullin and I tested some screw attached gyp on wood framing as a part of the CUREE project. Although the testing was intended to investigate damage thresholds, we did collect load data.
 
Dan