Canadian Wind Loads on Canopies, Open Structures and Overhang

[EngEquilibrium]

Hello,

I'm curious to know what other Canadian engineers used for wind loads (mainly Cp and Cg) on canopies, open structures and overhangs. I've seen many things posted for values/guides/figured/clauses etc in the US, but am finding limited information in the Canadian NBCC. Figures 4.1.7.6-C/E have some guidance for overhangs, but in my case I have a monosloped roof and Figure 4.1.7.6-G doesn't have any reference to overhangs. Would you typically just use Figures C and E? Or do you use figure G and then apply a Cpi and Cgi that would be appropriate?

Thanks!

 

[skeletron]

I am also perplexed as to why NBCC does not specifically address open structures. NBCC 2020 does now include Figure 4.1.7.12-A, -B which indicate CpCg for canopies attached to buildings.

I believe that the intent would be to use Fig. 4.1.7.6-G and apply the Cpi = +/- 0.7. The Commentaries indicate that Cpi = +/- 0.7 applies for sheds with one or more open sides. If your roof slope was < 3degrees, NBCC kicks you to Figure 4.1.7.6-C and I believe the same rules would apply. From a ten-second glance, it looks like Figure 4.1.7.6-G is slightly more conservative.

As it is not explicitly stated in NBCC, I believe this falls under the "use a rational engineering method to get a number" category.

FWIW: I usually do a quick crossover check with ASCE 7. It appears that a lot of the diagrams and methodologies have been derived from the same or similar research, including empirical testing. Not saying that it's apples-to-apples, but it's certainly close...more like comparing apple pie to pumpkin pie.