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"Gas Station" Canopy

"Gas Station" Canopy

"Gas Station" Canopy

You've all seen these types of structures; The monosloped roof supported by 2 columns at the center (Like a T).
I'm using BOCA for this particular job, and I am coming up with rather small wind loads on this type of canopy.  The mean roof height is under 15' and the limits in plan view of the canopy are 28'x33'.  Using the "Other Structures" formula (not adding in the Af, so I can get a psf wind load) for components and cladding I get 9.5 psf.  This seems ridiculously low.  Job is in CT on the coast, Pv=18.5 psf, I=1.08.  Cf = 0.45.
Anybody have any suggestions of why this seems low, or perhaps I'm using the wrong Cf (Monosloped roofs over unenclosed buildings)????

RE: "Gas Station" Canopy

pylko...I've done hundreds of canopies similar to this.  I typically use Cf=0.85 for free standing canopies and Cf=1.33 for those attached to or immediately adjacent to buildings.  Yes, that exceeds the table, but justifiable for overhang conditions.

I approach design in same way as you have done, by spreading over entire area and not using the concentrated approach.  I check separately for concentrated loads if necessary.  

Assuming I=1.08 and V=110 mph, I get factored q=20.5 psf, with Cf=0.85.


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