ASCE7-05 Components and Cladding wind pressure buildings greater than 60 ft

[tonymz]

I have a building with a footprint of 170 x 130 by 400 ft tall. V = 105 mpf, I = 1.0, Exposure "B"
The wind load program I use gives me a components and cladding corner design pressure of 70 psf and a non- corner pressure of 38 psf
My task is to design curtain wall support members near the corners from elevation 0 to 30 ft.
Do I need to use a design pressure of 70 psf at this location? Seems a bit excessive?

 

[dik]

Your exposure factor would likely give wind pressures less than 70 psf... You have to accommodate higher pressures around the corner areas. Depending on where you are, I would expect corner pressures to be approx 50 psf, or, thereabouts.

Dik

 

[EngineeringEric]

If this is a new design, make sure you aren't looking at ASCE 7-10 or ultimate winds. Now if you are doing a 400ft tall building of this size, your C&C numbers should vary pending on height. At that height are you sure you are exposure B? And i don't think 70psf is excessive for a corner at that height... not like you are framing this wall with 2X4 @ 16" o.c.

I MAY BE INCORRECT, THE HEIGHT VARIATION IS MWFRS. SEE THE SMARTER PEOPLE BELOW TO CORRECT ME

 

[tonymz]

Do component and cladding wind forces vary with height or are they the same at 30 ft vs 300 ft vs 400 ft on a 400 foot tall building?

 

[EngineeringEric]

I have the current code on my desk... so chapters are off. I may be thinking incorrectly, the pressures vary based on mean roof height, not actual height. But this is based on less than 160ft tall building, i guess it says when over you use wind tunnel and the C&C numbers must be no less than 80% of those calculated in Chap 30.

In summary, my mistake I must have been thinking MWFRS at the moment.

 

[JAE]

Using your input conditions I also get about 70 psf (negative suction) at zone 5 areas and 38 psf negative suction at zone 4.
These numbers drop to 42 psf and 31 psf respectively for larger effective areas.

I get positive 21 psf at zones 4 and 5 for small areas and 16 psf for larger effective areas.
Positive pressures are affected by actual height and mean height while negative pressures appear to be based on mean building height.

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