Chord tie at wall jog

[Roukkia]

We have a distribution center building with tilt walls (low seismic) that are jogging in and out along the length of the wall. We are trying to work up a way to have a continuous chord tie for our diaphragm. If we were to consider the ledger to be the chord tie we believe there would be some amount of thrust outward towards the walls as the ledger is spliced diagonally. I have seen these kind of wall jogs in a lot of these buildings so I am curious if anyone has encountered this or has any thoughts on the matter?

Our solution was to run the chord tie continuous with the innermost wall and run that the length of the building (see attached sketch). Does this seem like the best approach?

 

[KootK]

I have seen these kind of wall jogs in a lot of these buildings so I am curious if anyone has encountered this or has any thoughts on the matter?

I believe that the crux of the scheme is that you're dragging those lateral kicks back into the diaphragm through your roof framing members rather than dealing with them at the walls.

Our solution was to run the chord tie continuous with the innermost wall and run that the length of the building (see attached sketch). Does this seem like the best approach?

It depends on how long of a run that is. If it's very long then that option seems costly to me and I would prefer either:

1) The diagonal setup or;

2) An offset chord lap splice with a transfer diaphragm in between. This is similar to your proposal but not run the full length of the building.

 

[KootK]

Like the rotating box in the sketch below. For your case, this is related to whether or not there should be a continuous, roof level chord for this kind of building to begin with. Some folks think not owing to concerns for shrinkage etc.

 

[XR250]

Can the walls themselves be uses as the chord with sufficient attachment to each other? Also, maybe look at some three sided building action which is more friendly to discontinuities.

 

[Roukkia]

Koot - thanks for the wisdom. I wasn't aware of this transfer diaphragm concept so this is very helpful. By offset chord lap splice are you referring to something like the longitudinal collector extending to the next joist over, with the joist then being your transfer diaphragm collector? I forgot to add dimensions in my original post, but these walls are jogging 1ft every 50' or so. I feel like the forces generated from the rotating box in this case would be so low, that I wonder if we are overthinking this kind of thing?

XR - that walls are not connected to each other for shrinkage. We did look into three sided diaphragm action but ended up putting a frame in the middle to make it a normal rectangular diaphragm on each side of the frame.

 

[KootK]

By offset chord lap splice are you referring to something like the longitudinal collector extending to the next joist over, with the joist then being your transfer diaphragm collector?

Almost. You use the roof decking as the transfer diaphragm rather than one of your joists. Revit that sketch that I posted earlier. You could, in theory use one of your joist for that purpose but the lateral load on a joist top chord is likely to be quite punishing. The capacity of your transfer diaphragm determines how far back you need to take the collector into the the adjacent joist spacings. Maybe it's one spacing, maybe it's five.

I feel like the forces generated from the rotating box in this case would be so low, that I wonder if we are overthinking this kind of thing?

Probably in this instance. I'd still do something to enforce chord continuity though.

It's a more exotic setup but I've used the model shown below to, effectively, designate the foundations as the roof diaphragm chord. You gotta be careful with this stuff nowadays though. Some standards are starting to impose limits regarding the vertical distance between your diaphragm and it's chords. I would argue that those limits don't apply to the situation shown below but I'm not sure that all AHJ's would be inclined to agree.