Steel Stud Deflection Track Gap

[skeletron]

I'm designing some 16ft non-loadbearing interior steel-stud walls in an arena. Roof is 42" OWSJ @ 6ft o/c with standard metal deck. The OWSJ span 60ft. The room I'm working in is pretty much mid-span of the roof joists. This is an area that can get up to 50psf snow.

Most of my interior walls run parallel to the joists and will be fit up to the deck. I am spinning my wheels trying to figure out what to do with the deflection gap at the top of wall. I know that the deck will deflect L/240 = 5/16" and the OWSJ is likely also designed for L/240 = 3".

1. Is my design deflection at the deck = 5/16" + 3" since the deck itself will drop relative to the supports. I think it needs to be at least 3" because the OWSJ would drive the roof deflection.

2. Most slotted tracks give up to 2" total deflection (1" up + 1" down), so I'm now seeing recommendations in previous threads (#1 and #2) for top deflection clips or fire-stopping style track that can provide greater deflection values. TDC clips by Bailey and RipTrak by Clark Dietrich have been mentioned and look like they may help. Is this the go-to solution for this type of scenario? I think the clips would be easier to access and seem more conventional.

3. When the "total deflection" is reported on any one of these components it is usually indicative of an equal amount of movement up and down (i.e. Up + Down = Total). Is there a way to squeeze more deflection out of this by installing the screws at the bottom of the slot and utilizing the "total deflection" as my full deflection gap? Am I running a risk that the floor deflects and creates deformation at the top of the wall because the roof hasn't deflected (e.g. summer or fall w/o full roof load).

 

[structSU10]

in that bailey's catalog there is an HFA clip - any way you can frame some cold form between the OWSJ's that allow you to use that for the slip connection? I could see struts perpendicular to the OWSJ with a continuous angle with the HFA attached to that and each vertical stud.

 

[skeletron]

That's a great solution. Not sure if it'll work with my layout.

Floorplan is pretty much fixed; it's a golf simulator so the rooms have to bang on for the software to work. In the 16ft wall sections, I don't expect the walls (parallel to OWSJ) to be close enough to the OWSJ to use a slide clip like this. I'll keep it in my back pocket in case things do turn.

 

[skeletron]

I guess just thinking about this some more, if my top-of-wall connection (deep leg slotted track or deflection clip) can only accommodate a portion of the deflection gap, would my other option be to size the stud to take a proportional amount of axial load to compensate for the remaining "total deflection"?

 

[XR250]

I guess just thinking about this some more, if my top-of-wall connection (deep leg slotted track or deflection clip) can only accommodate a portion of the deflection gap, would my other option be to size the stud to take a proportional amount of axial load to compensate for the remaining "total deflection"?

I think in reality that is what happens but technically, you would have to design the bar joists for that support or you risk damage to the bottom chord. I have, in the past, framed the wall 3" low and braced it to the joists with low slope, diagonal braces so when it deflects, it just moves the wall sideways slightly. You could then add a pony wall on top that is 3" below the deck. Not sure if this works in you situation.

 

[RFreund]

Take a look at this system if you need to achieve a specific fire rating a need space for deflection over 2":
Deep leg tracks by "Fire Trak".

http://www.firetrak.com/fire-trak.html

 

[skeletron]

Thanks @RFreund. The Fire Trak is one solution I've considered. No special fire rating for this space, but it does provide that additional deflection gap. It seems a bit unconventional, so I'm hesitant to spec it on this job for a couple of reasons.

I have re-thought my original deflection gap calculation after looking through joist and decking tables.
1. The lightest gauge, standard RD938 deck is not governed by deflection (L/240) for 3-span condition. To me this indicates that the anticipated deflection of the deck is < L/240. The existing drawings don't show the deck spec, but this is pretty standard in my area.
2. The Canam joist guide talks about nominal camber of the joists (0.002 of the span) and lists a nominal camber (1-1/4"), a minimum camber (7/8"), and a maximum camber (1-5/8"). If true, this would reduce my original 3" estimate to ~2" if the joists are cambered. Again, there's no spec for the joists and it probably varies depending on the manufacturer. But I would expect some camber in the members for such a long span.

 

[phamENG]

Why not just abandon the slotted tracks and clips and do it the old fashioned way? You may not be able to get a deep leg track that does that, but you could get a pair of 6" leg angles and put them on either side of the wall with a 6" or 8" gap (or whatever your stud width is). Then leave a 3 or 4 inch gap between the top of the studs and the deck. Then make sure you have bridging within the top 12" of the stud.

 

[lexpatrie]

Couldn't you just frame it so the studs bypass the joists and then put something at the bottom chord of the joists that stabilizes the wall laterally? If you trap the studs between two pieces attached to the joist the wall can't go anywhere. If there's no need for a fire-block at the top of the wall and there's no particular need for a wall finish on the wall, (or you work around that)?

 

[EngDM]

The joist is probably L/240, but what is it under live load? The dead load is already deflecting it, so it may be less than 3" from live. I have specc'd installing screws in the bottom of slots before, but that was to a structural slab that had little movement. If you expect the floor to heave with the seasons a bit, then an option would be to nest two deflection tracks, the top track being installed at bottom of the holes, and the bottom track being installed at the center. You'd have 2" from the top one, and 1" from the bottom one. With allowance for 1" of upwards deflection/heaving.

The resistance to lateral load for the built-up configuration is harder to figure out, and not prescribed by Bailey, but for interior loads you should be fine.