Gable end frame details

[WWTEng]

Single story building, masonry walls and pre-fab wood trusses at the roof. Do you conventionally include a detail/section of how the gable end frame is to be connected to the rest of the trusses or is it not a consideration at all? In my case, I don't have a ceiling so the bottom chord of the truss/top of the wall under the gable end is not braced. I am considering putting a note to provide bottom chord bridging at 4' oc . Not sure if that's an efficient approach though.

 

[msquared48]

I always detail the gable end detail. It's an inherent knuckle joint if left to some conractors to decide how to do it.

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com

 

[WWTEng]

M^, do you use horizontal bracing top and bottom or diagonal bracing. I feel like horz would be OK and easier to install. Also, for wind on face of the gable, if I say put a not for the truss mnfr to design for 25 psf (for example) wind perpendicular to the gable, then I wouldn't have to worry about scabbing reinforcement to the verticals of the end gable.

 

[SteelPE]

A very similar question asked a few days ago.

http://www.eng-tips.com/viewthread.cfm?qid=340185

Although the materials are different, the question is still the same.

 

[WWTEng]

Steel, thanks for the post. I'll read thru the thread. But here are a couple of interesting things I found while doing some research:

http://www.pinellascounty.org/build/retrofit.htm

http://www.youtube.com/watch?v=SrYL2ooCOxA

 

[SteelPE]

The links you provided are interesting, however, this may be a case of making a horrible detail better but not perfect. I can see how adding the studs and blocking will help but, coming up with the engineering numbers to prove it might be a little difficult. I wonder if they justify it be assuming some sort of vierendeel truss?

 

[WWTEng]

Steel.

What I am thinking of doing is this: Create a section showing T&B 2x4 blocking extending to at least 5 trusses. Blocking is @ every other vertical or 4' oc, whichever is smaller. Each segment of the top blocking will also be nailed to roof diaphragm with (4) 8ds. The bottom blocking will be continuous 12' long, connected with (2) 1/4 screws at each truss. I am also going to put a note on the detail for the truss mnfr to design for wind of 25 psf perpendicular to the face of the truss, this way I don't have to worry about nailing scabs to the vertical members.

Also, here is another useful link:

http://www.structuremag.org/article.aspx?articleid=360

 

[ToadJones]

This is probably way off topic, but I really don't liek gable end trusses.
When I was building homes, (nail banger, not designer) I set the last truss in the width of the wall from the end and framed the gable end in 2x4 or 2x6 like the wall below. Setting the last truss (normal truss, not gable) in it could be used as a nailer on the inside. The gable end was then nice and straight (flat) and could span the height of the gable to the roof diaphragm and to the ceiling diaphragm.
I also would keep the gable wall down the height of the truss top chord and this would allow me to do a "Drop gable" type eave or overhang.
Much cleaner and more robust, though surely more $$$