Gable end truss drag loads 3

[reverbz]

Hey Guys,

If you have a gable end truss on a single story house with a window or garage opening below, would you call for a drag truss on the plans? I don't really see a reason to do so but I've seen drawings with this done. I'd love to hear some thoughts on why this is done and if it's necessary.

Thank you!

 

[KootK]

If the gable end truss would be over a line

 

[KootK]

If the gable end truss is over a line of lateral resistance then it would be a drag truss. Most garage front walls will be such conditions unless the designer is doing a three sided building lateral scheme.

 

[lexpatrie]

FAQ: https://www.eng-tips.com/forums/337/faqs/2886

(Side note, these seem to disappear when I try to edit them, which I just did, so it may not work). I may have destroyed three FAQs because I tried to fix the " thing on two of the FAQs.

 

[reverbz]

@lexpatrie ?

 

[phamENG]

Is the gable end sheathed? If so, I'd be detailing the sheathing to take the lateral load, not a bunch of studs connected with truss nail plates.

 

[XR250]

Hey Guys,

If you have a gable end truss on a single story house with a window or garage opening below, would you call for a drag truss on the plans? I don't really see a reason to do so but I've seen drawings with this done. I'd love to hear some thoughts on why this is done and if it's necessary.

Thank you!

Um, you're the EOR (I assume). It is up to you to determine the lateral load path.

 

[KootK]

Is the gable end sheathed? If so, I'd be detailing the sheathing to take the lateral load, not a bunch of studs connected with truss nail plates.

The sheathing path works for me and is, of course, more natural in many cases. That said the truss solution works fine too. The fabricator will just do structural gable end truss as shown below. The ostensible reason for doing that is just to take load off of any headers below. Shear capability is just a bonus.

 

[driftLimiter]

I specify gable end trusses with a default minimum drag load. I don't think it takes much to make a gable end truss resist say 200 plf as a drag truss.

From a load path perspective, I like the truss action from top chord to bottom chord better than a triangular chunk of plywood.

That being said, I also show sheathing and boundary nails on a typical gable end detail.

 

[bones206]

In reality, a portion of the shear flows through the truss members and a portion is taken by the sheathing. So taking a simple bounding approach like what @driftLimiter described is reasonable and conservative.

You also need to adequately detail the shear transfer to the shear wall below, so the truss can drag that lateral load into it.

 

[lexpatrie]

Think it either fixed itself or it got fixed unless there's another question?

 

[reverbz]

@XR250 not sure what you're doing here you could literally say that to any question posted on this site. To answer your question, no this is regarding drawings I've looked at not personally done...

 

[XR250]

@XR250 not sure what you're doing here you could literally say that to any question posted on this site. To answer your question, no this is regarding drawings I've looked at not personally done...

You have not given enough information to answer this question. It all comes down to the lateral load path. Somne structures may require it or a sheathed gable some may not.

 

[lexpatrie]

Ok, so the FAQ entry is working (or rather, it was, I edited it just now and it's probably disappeared again).

The article itself I can't find anymore on the Structure Magazine web site, and their online archive goes back only to 2012, so it's currently "lost" although some shadier websites (those "View PDF" ads are a scam to get you to download who knows what) has it.

I reluctantly updated the FAQ to show the full path to this link, use at your own risk, obviously but you can at least see the article from here:

Summary - STRUCTURE magazine

Free essays, homework help, flashcards, research papers, book reports, term papers, history, science, politics

studylib.net

Download or print, I can't confirm are virus free or whatever. That's kind of implicit in everything that involves a link, but these web sites with half a million "download updated Driver" or "Download to view PDFs" web sites kind of set me off, on the suspicion index.

 

[reverbz]

@XR250 Clearly I did as multiple people gave helpful answers....

 

[lexpatrie]

I won't call this a landmine question, but it's often enough discussed that you'll draw some grumpiness from the long term players on the site. XR wants more detail to give a better answer, others are more willing to provide connective tissue and wade in without as much information. It'll vary based on their mental energy and various other factors. I draw their ire frequently enough, as well. If you say something sounds wrong immediately they're asking for a treatise on it, and other times they get mad you're not addressing their post specifically because (see previous comment, you don't have the treatise yet.)

That grouchy "you're the EOR" is probably a comment we've all given at one point or another.

CAT blocking thehec out of my keyboard.

Let me skyhook the rest of this,

The drag truss isn't an absolute requirement, provided you supply a different load path - so a ladder truss, appropriately sheathed with transfer forces accounted for (i.e. nailing of the ladder truss into the top plate to transfer the shear load), I'd be surprised if a drag truss dramatically adds to the cost of the truss, that would be my comment, some of these residential guys like to use things like struct-o-ply or whatever it's called instead of actual sheathing like OSB or Plywood, so sometimes that's a fair backup in case they decide to get clever and remove functional WSP and replace it with insulation and "junk."

I'd explain more but the cat obstruction is making this just impossible to type with my left hand. It's too painful to keep going.

 

[Eng16080]

. . . would you call for a drag truss on the plans?

I have not on any past projects. For you, though, this of course depends on the specifics of your project. I would want a drag truss (which I assume means a triangulated truss as opposed to what's commonly termed a gable end truss with only flat vertical studs as web members) if there was not going to be sheathing with any appreciable shear strength fastened to the truss.

My typical detail in this situation involves a gable end truss with structural sheathing and a full length LVL header beam above the garage door located at the top of the wall. To either side of the door are shear walls, Simpson strong walls, or some other type of vertical lateral force resisting system (VLFRS). In this case, the full length header beam acts as a collector (drag strut) distributing the lateral load to the VLFRS at the ends of the wall.