Bracing Partition Walls to a Roof Structure when the walls aren't full height 1

[MJC6125]

I'm curious about how well kick bracing details work for the lateral support of interior partition walls in regards to allowing the roof structure to deflect without imparting a vertical load into the partition walls. I found the first two details shown below through a google search. Based on what I've seen in buildings, I think these types of details are relatively common. Are you concerned about how the brace detail in the one rigid brace doesn't technically allow the roof to slip up or down relative to the top of the wall?

I know there are alternative details when you have a nice smaller run of wall where you can kick near the corner of a wall in plan over to an adjacent perpendicular wall. But let's say you had a long run of wall where the top of wall is 12' and the roof structure above is 20'. Let's say its interior CFS wall studs and a bar joist and metal deck roof. Has anyone come up with a good solution for kicking/bracing the top of this type of wall? I came across this image from KootK from a previous thread for a CMU wall bracing detail. Would people do something like this for a metal stud wall.

 

[skeletron]

If you had an 8ft drop as you suggest, I might think about actually dropping a bigger beefier bulkhead and then bracing to that. Typically the CFS kick-brace at interior walls is for light walls with a drop equivalent to standard drop-ceiling height. Your brace ends up being a 20ga stud or sim. screwed/clipped to the structure and screwed to the track on the wall.

That, or I would run the wall full height to underside of deck. Brace the wall with clipped channels @ 4ft (or the Spazzer) and then have a connection at the top: either some sort of structure at the bottom chord of the OWSJ or actually right into the deck.

As for slip in the wall with the rigid brace: I don't think there is more play when using the CFS brace as opposed to a red iron angle. It would be assessed on a case-by-case basis.

 

[GC_Hopi]

I guess it would depend how much deflection you expect in your roof and what material your brace is. With a stiff roof structure and a light gage metal brace, I have not heard of issues. I assume if the roof needs to move there is enough play in the screws and out of plane bending of the brace at the connection. However, if you are so inclined it is easy enough to specify a deep leg top track with vertically slotted holes. I have done this before.

 

[MotorCity]

If this an interior wall, I assume the only lateral load on it is 5 psf. If that's the case, you may want to consider designing it as a cantilever wall and not providing any support at the top.

 

[BAretired]

I would be concerned about the two details shown below. In both cases, the diagonal braces would have to buckle in order to allow the upper structure to deflect. It is better to confine the top of wall horizontally, but allow vertical deflection.

The detail shown below permits one inch of deflection before the braces start to buckle, that is, after the screws have been removed. If more deflection is required, the gap may be increased.

BA

 

[strucbells]

@motorcity Only works for low seismic

 

[BAretired]

But let's say you had a long run of wall where the top of wall is 12' and the roof structure above is 20'. Let's say its interior CFS wall studs and a bar joist and metal deck roof. Has anyone come up with a good solution for kicking/bracing the top of this type of wall? I came across this image from KootK from a previous thread for a CMU wall bracing detail. Would people do something like this for a metal stud wall.

I can't remember ever having encountered that situation, but I guess it would have to be assessed on an individual basis. With the ceiling so far below the roof, it makes no sense to stabilize the wall from the roof. A framing system would likely be used for the ceiling itself. The wall could be laterally braced by the ceiling framing.

BA

 

[skeletron]

Yeah the 12ft wall with roof structure @ 20ft happened to us at a TI in a mall recently. You either have to drop big bulkheads or use heavy-duty ceiling framing.

 

[MJC6125]

The 12' tall wall to 20' high roof was an example scenario, but I have typically used hardlid ceiling framing to brace the walls in these cases.

I was wondering more generally if bracing these walls to the roof structure is acceptable or how it is typically done in an acceptable manner. What I typically see when I go to existing buildings in these instances is like @skeletron mentioned in his first response: a 20 ga stud screwed to the top track of the wall and to the deck above. I just don't think this actually allows for the roof structure to deflect unless the that stud buckles or the wall moves out of plane as the roof deflects. I haven't been called to review an issue with these and I don't remember seeing them buckled ever, so I'm not sure what happens in practice.

However, if you are so inclined it is easy enough to specify a deep leg top track with vertically slotted holes. I have done this before.

Are you suggesting a deep leg slip track at the top of the wall and doing the kicker up from that or are you just saying run the wall full height and do a slip track? Because I don't think the first thing actually braces the wall unless your kicker has a moment connection at its top end or is framed like some sort of frame with another stud kind of similar to the double angle triangle image. I have seen details like this on other engineer's drawings, but I don't think it actually works in theory.

 

[GC_Hopi]

Yes, a deep slip track. The system would function the same as the hand sketch given above. I am not sure why you would need a moment connection. One of the snips above shows splay wires which is definitely not a moment connection. Here is a Link to a bunch of CFS details. If you want to be fancy you can start adding clips with slotted holes at the connections and the slots will allow movement.

 

[MJC6125]

I think if you draw the FBD for that kicker, it doesn't actually work out per the image below.

 

[BAretired]

In the last pic (by OP), there can be no force F, and no reaction Rx. So, there can be no force in the kicker.

BA

 

[GC_Hopi]

What about the following FBD?

 

[BAretired]

No good!

BA

 

[GC_Hopi]

One more! lol Ok, I am done.

 

[BAretired]

I modified the sketch of GC Hopi below:

The inverted bucket shape can be a continuous member, but more likely a short keeper assembly spaced along the partition to be laterally supported. The gap must be equal to or greater than the expected deflection of the structure above. The connection to the roof structure must be rigid to prevent the keeper assembly from rotating.

BA

 

[MJC6125]

No good!

What is automatically incorrect about the one before this comment? I think the FBD would be stable.

 

[BAretired]

How does the lateral force get from the channel to the hinge? You didn't show a connection between them.

BA

 

[MJC6125]

Ah, I figured a connection between those elements was implied. Carry on.

 

[BAretired]

Ah, I figured a connection between those elements was implied. Carry on.

It's not implied. If it's a vertical member hinged top and bottom, the assembly is unstable.

If it's a vertical member hinged on top and rigidly connected to the channel, deflection of the roof will be transmitted to the partition.
BA