Allowable Bearing Stress of...GWB? 1

[phamENG]

I've been asked to size some connections for architectural elements that will be installed after the space is otherwise finished - so wallboard will be up and painted before these custom pieces are installed. They are mostly cable connected so the reactions are considerable if not large, and the connection needs to be well thought out.

As I resolve the moment in the connecting bracket, I realized I have no idea how much GWB can take in bearing. Anyone have a clue? This could have applications in stair hand rails, too - I have a problem in my house where a stair handrail with brackets spaced too far apart has crushed the drywall below it. Curious if it's been reliably quantified anywhere.

Thanks.

 

[kipfoot]

You might find something useful in this document: GA-235-2019

 

[phamENG]

Thanks. Found that last night. Sadly there's nothing on bearing stress that I could find. Closest might be the negative wind resistance if I were to calculate the stress under the nail heads...

8x8 pattern, 80psf, that's 35.6lbf/nail. 3/8" roofing nail head has an area of 0.11in² for a bearing stress under the nail head of 322psi. It's a start.

 

[Brad805]

I noticed Simpson Strong Tie has some hangers designed for applications where there is drywall behind. I looked now and do not see any pull out data and they are top flange hung. I seem to recall a project not long ago where I was concerned about this problem for a staircase. I believe Simpson has done some research if my recollection is accurate.

https://www.strongtie.com/joistfram...medsteelconstruction/s.dhutf_hanger/p/s.dhutf

 

[BAretired]

This table provides ultimate strength. You can apply whatever factor you wish. For the full link, see:

https://www.americangypsum.com/site...ypical Mechanical and Physical Properties.pdf

BA

 

[dhengr]

PhamENG:
Whatever the shape and size of your bracket or end pl., make a plywood piece the same shape, but .5” smaller on a side, and the same thk. as the sht. rk. in question. Trace it onto the sht. rk. and cut a pocket out to fit the plywd. Nail and glue the plywd. in place and fix your stl. bracket over this. The fact that plywd. is under-thicknessed these days should cause the stl. end pl. to draw up tight on the sht. rk. when bolts/screws are tightened. This will give you a higher compressive strength behind the stl. Whatever they are trying to do this should not be too much extra work.

 

[Enable]

At least one overweight drywaller per ft2 in bearing. And at least 1 stripper and 3 overweight drywallers per 3 sheets of sheetrock in flexure when simply supported over 6 foot span or so! Details of site testing here.

 

[phamENG]

Brad805 - Thanks. I reached out to Simpson but they couldn't point me to anything but the mechanical properties document.

BA - I saw that, but for some reason I envisioned the samples oriented vertical. But it doesn't actually say that and my 322psi above comes in pretty nicely with the table. Thank you.

dhengr - simple, elegant, and practical. A fantastic idea. Thank you.

Enable - good grief. And Canadians say Americans are crazy...

 

[BAretired]

phamEng - Orientation should have been stated in the table. I assumed the intent was normal to the plane of the gypsum board; otherwise slenderness would be a significant factor.

BA

 

[Enable]

phamENG: I think it shows great initiative. When strip clubs are closed don't give up, bring the strip club to the jobsite! The Grey Goose was a nice touch though. The videos circulating in Canadian construction circles are wild. The best is the plumbers in the background wanting nothing to do with it and just hacking away at their task lol

BTW not to hijack your thread but I would appreciate any insight you have on a thread of my own in the restoration forum. Thanks!