Cantilever Wind Canopy Design

[SoFloJoe]

Hi All,

I am designing a canopy shade structure for a manufacturer to eventually be used in Florida and potentially other states. Its a 2 column design, the columns are spread 33ft apart with a cantilever shade extending about 11 ft out and with a curved fabric roof structure ranging from 6 degrees to 22 degrees. See attached for a simple diagram.

I conducted the components and cladding wind load calc and focusing on the uplift condition which would be controlling (D+0.6W ASD). With this the GCP for overhang perimeter is fairly high at -2.2. I am designing for a breakaway canopy system at 75mph so design wind speed at 105mph per Florida Building Code. I am ultimately getting 68 psf of uplift, which seems a bit high to me.

I have looked through the forum and ASCE 7-10 and cannot find a specific section that applies to these canopies. I am trying to value engineer it and my design seems to be a bit too conservative. Is there a reduction that I can consider that maybe I am overlooking? I do not think using the component & cladding procedure benefits me here. If I could use a field or even perimeter value for my GCP this would help, but technically I would say this should be an overhang.

Any suggestions would be appreciated! Thank you

 

[SoFloJoe]

As a follow up, I found in ASCE 7-16 the section on attached canopies 30.11. I did not find this in ASCE 7-10. But I can use 7-16 since this product will be implements 6+ months I believe 7-16 will be adopted soon.

With this I found that using the criteria base speed of 105 mph,
Kz = 1.13 (at a max of 60 ft mean elevation height)
Kzt = 1 (staying conservative)
kd = 0.95 (circular curved roof)
ke= 1
qz = qh = 0.00256kzkztkdkeV^2 = +/- 30mph

Using the figure 30.11-1B with greater than 100 sft surface area
My GCpn = -1.13,+0.63

Resulting in -34.3, 19.1 psf

I am happy with this result, the only thing is that ASCE is using this for a "connected" structure not a stand alone, does anyone see an issue with this?

Thanks again!

 

[Yao1989]

I typically find canopy attached to building have stronger uplift than stand alone, so you are probably on the safe side. For reference I recently did a calculation for a canopy in Toronto using Eurocode (never saw ASCE 7-16 yet, and canadian code mentions nothing on canopy) just few weeks ago and got 1.4kPa uplift ~ 29psf overall.

There is a section in the ASCE 7-16 for open structure as well if that is closer to your condition.