How They Do This?

[XR250]

24" O.C. room truss designed for 40 psf floor live. 16 ft. wide room, 2x10 bottom chord. Could that massive plate in the middle being used to create a moment connection? Otherwise, are they counting on an 8 ft. cantilever on the joist? It does say 40 PSF live load in the room area in notes that are further down on the sheet.
View attachment 9611

 

[EngDM]

I think you're right about cantilevering the bottom chord, I haven't seen those plates be sized for moment and I avoid wood moment connections like the plague; I'd imagine truss suppliers would be in the same boat.

Do you have a local truss supplier you could reach out to who might be able to answer this for you?

 

[XR250]

I think you're right about cantilevering the bottom chord, I haven't seen those plates be sized for moment and I avoid wood moment connections like the plague; I'd imagine truss suppliers would be in the same boat.

Do you have a local truss supplier you could reach out to who might be able to answer this for you?

They are local but my experience is that generally they're not that helpful and not Ron the Redneck!

 

[ANE91]

The plate at Node 13 is a splice plate. You see the same thing in normal trusses. Why wouldn’t it facilitate continuity of the chord? I would consider it to be a “weak moment connection.” Wood bearing at the top and tension in both plates at the bottom. That said, I don’t like where it is. I saw a big roof collapse recently where the splice plates “unzipped” right down the middle of the span.

Waiting for the truss guys to pop in and prove me wrong.

 

[RWW0002]

The plate at Node 13 is a splice plate....

I think the concern is over bending in the bottom chord. Either the splice plate has to take bending (never seen that and my gut says to avoid it) of as XR pointed out the bottom chords would have to cantilever each direction to the splice.

I agree with your concern over the condition, but do not have alot to add here. Surely there are better locations for this splice. Why not mirror splice 15 on the adjacent side? I would reach out to truss supplier on this one I think and see if there is a better solution, even if it technically "works"

 

[XR250]

Well here it is in real life. I imagine interior wall will be working some.

 

[ANE91]

 

[XR250]

If they are counting on the 2x10's cantilevering, it'll certainly be a weird deflection curve inside the room if it actually gets loaded up.
The truss guys don't care about that though.
This is one of those houses where the contractor is saying he will never do a trussed roof again.
Couldn't get the truck anywhere near the site so he had to pay laborers to carry each truss 200 yards down the street. Some were 400 pounds

 

[XR250]

View attachment 9618

Seems like an absolutely terrible idea.

 

[ANE91]

Seems like an absolutely terrible idea.

It is when the splice plates are positioned at points of maximum moment. You cannot avoid bending entirely in any chords. I'd ask for them to be moved if the thing wasn't installed already. No idea what to do here...

 

[XR250]

Apparently, the AHJ is only gonna let them use this for mechanical equipment anyway so it’ll never get loaded significantly

 

[XR250]

Could sister with a 2 x 10 if needed

 

[mikek396]

View attachment 9618

just curious - what reference is this from?

 

[ANE91]

just curious - what reference is this from?

TPI 1, which is the code that truss designers use.

 

[XR250]

TPI 1, which is the code that truss designers use.

Might work great in theory, I would never want to count on that for a floor system though.

 

[phamENG]

Can't say I love that knot.

 

[XR250]

Supposed to be No. 1 SYP - K(NOT)!

 

[ANE91]

Supposedly, all the extra capacity from TPI (relative to ASCE/NDS) is substantiated by testing. I think SJI does the same thing. It’s kind of a wash, though, when plates are embedded over tack-nailed/stapled joints and knots end up in the worst possible places. These days, I only get called when trusses break, so I could be biased.