Wind Loads on Canopy
Wind Loads on Canopy
(OP)
I frequently design drive-through and entrance canopies for churches, banks and other structures.
I intend on designing these as open structures. I see no other ASCE 7-02 provision for wind loads on canopies.
In ASCE 7-02, Figure 6-18, why does this portion of the load and wind pressure determination process start with Monoslope roofs in lieu of Gable and Hip roofs? Are there no force coefficients for open structures with Gable or Hip roofs?
What am I not considering?
Thank you!
I intend on designing these as open structures. I see no other ASCE 7-02 provision for wind loads on canopies.
In ASCE 7-02, Figure 6-18, why does this portion of the load and wind pressure determination process start with Monoslope roofs in lieu of Gable and Hip roofs? Are there no force coefficients for open structures with Gable or Hip roofs?
What am I not considering?
Thank you!
RE: Wind Loads on Canopy
RE: Wind Loads on Canopy
I did just as you and have suggested, as per 6.5.13. However, the resultant pressure=qz*G*Cf, before applying the roof area, is very low (14 psf) in comparison to what I would expect for a canopy, of which, in the absence of any other provision, I want to compare to an overhang, at the very least.
I realize, I can design at my discretion. I'm just amazed at the great range of difference between the extremely high pressures of the Simplified Procedure and the extremely low pressures of the Analytical Procedure.
By the way, I have downloaded the demo for Wind Loads on Structures, that you have recommended. Do you use this exclusively for all of your structure designs? Do you find it friendly and convenient?
Thank you, very much, for all of your guidance.
RE: Wind Loads on Canopy
If I'm analyzing a simple structure I generally use the wind program alone, however, I generally check hand calcs against the ones from the program on more complex buildings. If they are reasonably close I leave well enough alone. The reports make a very good presentation and include them in with all my other calcs for submittal. I've found that the program is fairly accurate and can save an enormous amount of time (allways check to be sure, a program is only as good as the input).
RE: Wind Loads on Canopy
I failed to mention that in the simplified procedure mean roof height is taken at 30'. Pressure on buildings with a mean roof height of less than that will come in higher than in the analytical procedure.
RE: Wind Loads on Canopy
Thank you for your time and consideration!
RE: Wind Loads on Canopy
ERV,
Where can I find the demo for Wind Loads on Structures to be downloaded?
Thanks!
RE: Wind Loads on Canopy
I do not know where we obtained the draft copy however.
RE: Wind Loads on Canopy
Governing bodies are generally free to adopt any guidance code they wish, and any version of such, and to modify or supplement such codes to "fit local conditions".
RE: Wind Loads on Canopy
When the design reference - in this case any ASCE wind provision that you mention - does not address a condition, how then do we proceed? Make something up? Use the provisions defined in an older code such as SBC 1997?
Why not use the newer, unadopted version of the reference that actually defines some provisions for the condition being considered? This is certainly better engineering practice. And for the throngs out there afraid of "Lawsuit", this approach is likely more defensible than the alternatives.