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ASCE 7-05 - Vertical overhang pressures on leeward wind

ASCE 7-05 - Vertical overhang pressures on leeward wind

ASCE 7-05 - Vertical overhang pressures on leeward wind

(OP)
It may not end up making any difference in the design, but I am designing supports for two canopies hanging off the side of a low rise building (4' wide x 16' long and 8' wide x 12' long). I'll design the canopies for the uplift on an overhang, and I know the uplift on an overhang is due to windward wind hitting the surface and channeling upward. Does the opposite happen on the leeward (suction) side? Is it a downward force? An upward force? Just a force parallel to the canopy? Thanks for your knowledge and opinions.

RE: ASCE 7-05 - Vertical overhang pressures on leeward wind

On the leeward side, my understanding is that there would be the usual suction (uplift) force, normal to the canopy surface. There is also the possibility of a downward load, but that usually comes out to less than the minimum 10psf design load, for most cases around these parts.

Thaidavid

RE: ASCE 7-05 - Vertical overhang pressures on leeward wind

Why not use components and cladding simplified table for Zone 2 and 3 overhangs? Negative magnitudes indicate uplift. Adjust for importance and exposure.


Juston Fluckey, SE, PE, AWS CWI
Engineering Consultant

RE: ASCE 7-05 - Vertical overhang pressures on leeward wind

If your question wasn't on the how (you said you were going to design it for the overhang) and more on the academia of the wind behavior, I would point out Method 2 of the C&C does not give a positive GCp for overhangs like it does for the non-overhang zones. You are always looking at an uplift force regardless of windward/leeward. However, this figure does not indicate if there is a difference in magnitude and which side is controlling. I would think the leeward side provides the worst-case results though.

Juston Fluckey, SE, PE, AWS CWI
Engineering Consultant

RE: ASCE 7-05 - Vertical overhang pressures on leeward wind

ASCE 7-10 sheds more light:

Juston Fluckey, SE, PE, AWS CWI
Engineering Consultant

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