Tek Screw Shear Fastened Thru 5/8" Sheetrock 2

[XR250]

I have a situation where I need to fasten a light gage track to a stud wall thru 5/8" sheetrock to resist shear from gravity loads. I am trying to avoid this, but my client is pushing me to at least do some research. Does anybody know of any testing data that has been done for this condition? I already called Buildex and while they recognize that this comes up alot, they have no testing data.

Thanks

 

[Ron]

XR250....screw will be subjected to shear and bending, since the 5/8" gypsum board offers little or no resistance to the screw. Compute both values and check by unity equation.

 

[XR250]

Sounds easy except the studs are 20ga which likely cannot provide decent fixity for a cantilever. Even if they were heavier, I still would not know how to determine if the stud can provide the fixity.

 

[jayrod12]

How about drywall anchors at a good spacing

 

[XR250]

that was suggested by my sub
I think I will call it a day and go with costlier Plan B

 

[MotorCity]

Sounds to me like you answered your own question........."the studs are 20ga which likely cannot provide decent fixity for a cantilever".

The screw to stud connection offers a single point of contact, and is a pinned connection (no rotational resistance).

Even if you came up with some method of justifying a cantilever, I don't think it would be convincing enough to satisfy my comfort level.

 

[KootK]

Is the gypsum between the track and stud or outside of the track?

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[XR250]

between.

 

[Teguci]

If you can use gypsum sheathed steel studded walls to resist lateral seismic loads then, arguably, you can support a static lateral load through the gypsum.

Using the following table you can interpret the plowing force resisted by a certain number of #6 screws (ex - 1.5-#6 screws resist 184 lbs of shear, ultimate)

http://www.bayarearetrofit.com/PDFs/Drywall shear capacity.pdf

This one, using steel studs, shows on page 19 - #6 screws at 6" edge spacing resisting 748 lbs/ft ultimate (this is for double sided test - say ultimate is half) - pg 13.

http://texas.transconsteel.com/Products/CFS/docs/2_shearwall.pdf

For the track to wall, check for compression stress on the GWB (200 psi or something).

 

[KootK]

Yucky. I suspect that, in reality, the gyp would function like a shim plate does in bolted steel connections (T & C and no fastener bending). Even if you could quantify that, however, It would seem sketchy to have building gravity performance so heavily reliant on the presence of competent drywall. Although we do rely on it to brace our studs...

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[XR250]

Agreed. As far as gyp. shearwalls, my guess is that the resultant of the load on the screw from the gyp is less than 1/2 the thickness of the gyp to the stud. In my situation, the load is at the tip of the screw. As such, the shearwall tables are not of any real use.
I do have a similar situation, however, where I need to attach some soffit ceiling joists to the studs thru the gyp. The load is only about 70 lbs under wind and much less under gravity (they only span 5 ft.). I think I am going to feel ok about using (2)#10 for that.

 

[wannabeSE]

OSHPD has published allowable values in there preapproved partition details

http://www.oshpd.ca.gov/fdd/Pre-Approval/preapprovedDetails-wTemplate.html

See pdf pages 23-25.

Some background explaining the basis is at

http://www.google.com/url?sa=t&rct=...KrrPWwCQTA_l5qCqg&sig2=UZk5mRELPJJZu3DEn66mlA

 

[bookowski]

Install the tek at up and down angles, forming the worlds smallest truss.

 

[XR250]

OSHPD has published allowable values in there preapproved partition details

http://www.oshpd.ca.gov/fdd/Pre-Approval/preapprov...

See pdf pages 23-25.

Some background explaining the basis is at

http://www.google.com/url?sa=t&rct=j&q=&am...

Interesting... I am not sure what they mean by a "prying condition" however. 100lb allowable w/o prying, 15 lb w/ prying. I assume a track fastened to the wall would be a non-prying condition?

 

[KootK]

Nicely done Wannabe. I would also assume our condition here to be non-prying.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[XR250]

Dunno if I still feel comfortable fastening a floor system in that manner even with their testing

 

[KootK]

So this is a track supporting balloon framed floor joists? I was thinking of a wall to track which is why I was so befuddled about the location of the dry wall. This may indeed be a prying condition of sorts.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[XR250]

See attached. (drywall not shown)

 

[KootK]

Re-flip-flop then. If the joist shear comes in through the clip angles, I'd say no prying.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[JLNJ]

I don't understand the load path.

Does the vertical load go through the gyp and then make its way back into the studs through screws further down the wall? Or is there some shear friction effect going on? Is it through the fixity in the screws?