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re-entrant corner drag strut offset from corner

re-entrant corner drag strut offset from corner

(OP)
I am performing a peer review of a qualified SE's work whereby he designed a re-entrant corner drag strut / collector beam offset about 4' from the actual corner of a tilt-up building. I have never seen this done. It would be my understanding that the collector/drag strut would need to fasten directly to the wall with some sort of hardware.

Can anyone give me a scenario where this isn't the case? He did this in one direction, but not the other.

Thanks for any help someone could give.

RE: re-entrant corner drag strut offset from corner

Perhaps the wall was moved, but the drag strut was not? If so, it will need to be redesigned.

Is there a connection detail?

Mike McCann, PE, SE (WA)


RE: re-entrant corner drag strut offset from corner

I can think of situations where a collector might not be needed at all. I can't, however, think of any where a collector to no where would make any sense. Like Mike has intimated, it sounds like an error of some kind. Post a framing plan sketch and we'll be better able to comment intelligently.

The greatest trick that bond stress ever pulled was convincing the world it didn't exist.

RE: re-entrant corner drag strut offset from corner

(OP)
Thanks for the responses gentlemen! I see that the collector in the north south direction is a chord/collector. The other direction is still a drag strut in my opinion, but I may be wrong if I'm not understanding their design methodology.

Thanks again!

RE: re-entrant corner drag strut offset from corner

The roof diaphragm can transfer load from the 20' purlin (4' from the wall) to the 20' wall. Not a good situation. Is there any special connections called out for the diaphragm to these members?

Garth Dreger PE - AZ Phoenix area
As EOR's we should take the responsibility to design our structures to support the components we allow in our design per that industry standards.

RE: re-entrant corner drag strut offset from corner

(OP)
woodman88: There are purlins that run east to west at 8' oc, typ. I tried to "cartoon" them in.

However, the only member connecting the diaphragm to the 20' wall is the wall's ledger.

RE: re-entrant corner drag strut offset from corner

I agree with Woodman. The 4' x 20' section of roof can act as a transfer diaphragm. It's bounded on all four sides by boundary elements.

I also agree that the collector likely serves as a drag strut for loads applied parallel to the long direction.

It's a weird setup but it can be made to work. Can you query to the EOR to confirm their intent? I wonder if the intent was simply to not mess with the purlin spacing for aesthetic reasons.

The greatest trick that bond stress ever pulled was convincing the world it didn't exist.

RE: re-entrant corner drag strut offset from corner

(OP)
Yes - I can ask. I personally would've added a purlin to drag it at least a bay into the eastward direction for easy continuity.

Thank you for the comments. I also have his calcs, but it's not exactly complete and transparent.

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