Wind Load Coefficients for Awning/Canopy

[garnereng]

I am looking for pressure coefficients compatible with ASCE 7-95/98 for open awning structure. This awning is a monoslope (up to 45 degrees top slope) welded tubular structure with a fabric cover on the top sloping surface and sides (open bottom).

 

[austim]

garnereng,

you may have noticed that your posts keep disappearing from this forum. That happens when other members have 'red-flagged' those posts.

I can only guess why others have taken that course of action, but it could well be that it is because you have posted (and continue to post) multiple posts on very closely related topics.

I suggest that you will have more chance of getting the responses that you are looking for if you condense all of your roof wind coefficient requests into just one post. That will have a much better chance of survival.

 

[garnereng]

austim,

Thank you for the heads up. I just discovered this site yesterday and am totally new to what happens here. Thnak you for the advice as to the multiple closely related posts. I had no idea that that was a "no-no".

Thank you.

 

[Ron]

garnereng...the procedure austim described is not necessarily a no-no, it's just that it might imply you are one of a group who might get red flagged routinely such as students looking for answers to homework questions. Assuming you are not in that group, I'll give it a shot.

A canopy or awning would typically be an open structure with a monoslope or arched roof as you have described, though other configurations certainly exist. Looking at a monoslope roof on an open structure, the coefficient, Cf, will vary from a low of 0.2 for a flat roof to 1.3 for a roof up to 40 degrees (30 degrees max. in table, +/- 10 degrees allowed), depending upon its length to width ratio. As the progression of the table would imply, a roof at 45 degrees would likely carry a higher coefficient than shown in the table, considering the length to width ratio of the canopy.

Here is where a bit of engineering judgment comes in. Since the table doesn't specifically address your condition, you have to look at what might be a proper and conservative application of the intent of the coefficient. Consider the table for freestanding walls and solid signs as a place to start for your comparison. This table is also dependent upon a length/width comparison and its coefficients, Cf, range from 1.2 to 2.0.

Your application is likely somewhere between these two tables...monoslope roofs and solid signs. Using the projected area of the 45-degree face, you can compute a length/width ratio for the solid sign application, and given the canopy dimensions, you can compute L/B for the monoslope condition. All of this will likely lead you to a rational coefficient of somewhere between 1.0 and 2.0.

You can apply similar logic to your other configurations.

I will add a caution that if you are not familiar with computing wind loads on structures, you should have someone on a local basis (in person) mentor you through the process, as there are numerous variables to consider that cannot be adequately covered in a query to a forum.

Good luck.