Checking Roof Diaphragm for Wind Uplift

[oengineer]

I have been tasked to check roof diaphragm for uplift for a building. I have already designed the roof diaphragm for wind shear and vertical DL + LL. If anyone knows of a good example on how to check for uplift, suggestion & comments are appreciated.

My building is enclosed. Would wind uplift still be critical for the roof?

 

[msquared48]

Well, depending on the roof slope and wind orientation, you can develop upward suction on the roof.

You can also get upward suction on the eaves.

Yes, it can be critical, depending on your situation.

Mike McCann, PE, SE (WA, HI)

 

[human909]

Uplift can often be critical especially due to the potentially unrestrained compression flange.
(See the thread next-door about fly braces if you dare.)

 

[oengineer]

Would either of you happen to know of a good design example? I have a flat roof.

 

[TheDW]

What have you tried so far?

Did you find your components and cladding roof uplift loads, and combine that with the D+W load combination? From there most diaphragms have tabulated vertical load psf capacities (metal deck) or section properties so you can check it as a beam in a 1' width (wood).

 

[Bagman2524]

ASCE-7-10 section 29.5.1 (equation 29.5-3)is for uplift force on rooftop structures. And section 27.4.4 is uplift on Roof Overhangs.

All I know is P/A and Mc/I

 

[AaronMcD]

I'd read code, get wind load, combine with dead per applicable load combination, check any part of the diaphragm I think could be a weak point. You don't mention what kind of diaphragm or wind loads. One part that could need special attention is holding down an eave. Corner eaves can get a lot of uplift. A recent small wood eave repair I did had 230 lbs uplift per foot and that was only an 18" eave. I prefer to add clips for that than trust 3 toe nails.

http://www.hellodwell.design