Wind pressure on an open roof
Wind pressure on an open roof
(OP)
I'm working on a project involving a roof that is about 80'x60' and about 22' tall at its peak. The roof is being built on the ground and then lifted onto the main structure which is about 40' above the ground. Right now I'm trying to determine how the wind is going to act on the roof. I followed the procedure in the National Building Code of Canada to find the pressures acting on the top of the roof but this procedure is for a roof sitting on an enclosed building, and when the roof is being lifted it is going to be more like a canopy. Any suggestions on how I would go about calculating the uplift on the roof while it is being lifted? Any suggestions would be helpful.
Thanks,
Sheldon
Thanks,
Sheldon






RE: Wind pressure on an open roof
I would design to a specific wind velocity and not lift if the velocity is excedded or forecast for the time of lift. You do not have to design for the highest wind load for your area if you are just lifting. However, once in place, the structure, to include the roof, can and will see the recommended design wind loads for the area.
Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask
RE: Wind pressure on an open roof
After it is lifted in then you need to treat it as a double sloped free roof (most codes have a coefficient for this).
You may find that the critical case is between the initial andf the final state where it is partially blocked under.
RE: Wind pressure on an open roof
BA
RE: Wind pressure on an open roof
Thanks for your input so far.
RE: Wind pressure on an open roof
Overall: +0.9 or -1.2
Or in 4 zones:
A +1.3/-1.4
B +1.9/-1.9
C +1.6/-1.4
D +0.7/-2.0
with negative being upward.
B,C, and D are at the ends, eaves and ridge respectively and extending 10% of the length of the respective roof dimension.