Metal Deck as Flexible Diaphragm

[Rainbowtrout]

I am designing a very small building, 22 ft by 7'-8" actually. The structure will be CMU and have type B roof deck. My question is, because the span is so small, is it common to use deck only as a flexible diaphragm - by which I mean no joists no beams? I am going to use 7'-8" as the span and select fastener layout per SDI.

Thanks in advance!

 

[JAE]

I think you'd have to use a 16 gage deck at 1 1/2" depth to get a simple span to work.

It isn't a "diaphragm" question here - just a strength/stability question.
Perhaps a 3" deep roof deck? For simple spans of 7'-8" you can use a 22 gage.



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[KootK]

Whether or not you have beams or joists has little to do with whether or not your diaphragm should be considered flexible for lateral analysis. Additionally, for a simple four perimeter shear wall layout, the classification of your deck as rigid or flexible will be immaterial as it won't affect the distribution of shear to the block walls.

Spanning the deck without intermediate support sounds like an economical solution. Just ensure that you still meet Factory Mutual requirements etc.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[KootK]

Will your building be open on one of the short sides? If so, what will be the lateral system on that side?

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[Rainbowtrout]

@kootk, the building is 9 feet tall and will have a pedestrian door @ one short side. The masonry walls will be designed for that condition.

 

[KootK]

Got it. I was just concerned about potential 3-sided diaphragm action.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.