ASCE 7-02 - Open Building - Load on Roof

[BurgoEng]

I have a simple 4 column "shed" with no walls, about 20ftx30ft with h=15ft. I am trying to figure out the wind load to apply to the roof. According to section 6.5.13, (Eq 6-25)F=qz G Cf Af. Cf is taken from Figure 6-18, based on the B vs L of the roof as well as the angle. I've got that. My problem comes when determining F. According to 6-25, Af is the projected area normal to the wind direction. Does this projected area refer to a vertical projection of the roof (including the angle) or is the the plan area (BxL) of the roof. If it is indeed the projected vertical area, that is a very small number...roughly 1ft rise over 30ft so A=1x20ft=20sf. But, if it is the roof plan area A=20x30=600sf.

Also, what about Comp&Cladding? I was planning on using qh as the pressure because there does not seem to be anything specificaly designated as design of C&C for and Open bldg.

 

[UcfSE]

ASCE 7-05 has expanded it's evaluation of open roofs. Check there.

I would use the projected area normal to the plane you're interested in, one area for the vertical component of the pressure, and another area for the horizontal component.