ASCE 07 min wind load on car shade canopies ?

[Zeeko83]

We are designing a cantilevered car shade canopies to cover 18ft X 40 ft, but we end up using:
3 steel post 78.7X78.7x 0.4 in .
3 isolated footing (width 40 in) (80 in length) (30 in depth)
it seems huge! right? we considered minimum wind pressure as 10 psf.
is there any exception in the code regarding the minimum wind load on car canopies?
Thank you in advance

 

[woodman88]

10 psf wind load seems to be low for an Open Free Roofs per ASCE 7-10 section 27.4.3. Which year and section are you using?

Garth Dreger PE - AZ Phoenix area
As EOR's we should take the responsibility to design our structures to support the components we allow in our design per that industry standards.

 

[Zeeko83]

I am using ASCE07-05 where the min wind load is 10 psf as per 10.1.4.1. and i'm using section 6.5.13.
Actually I am not sure if my structure can be considered as building or not! in the link below u may find something similar to what I am designing.

http://www.shadestructures.net/Projects/Details.aspx?project_id=37

thank you very much

 

[woodman88]

So you are getting a wind load from section 6.5.13 less than the 10 psf from section 6.1.4.1?

Garth Dreger PE - AZ Phoenix area
As EOR's we should take the responsibility to design our structures to support the components we allow in our design per that industry standards.

 

[Zeeko83]

Yes, therefor I am considering 10 psf downward case and upward case.
the covering material is perforated. considering 10 psf seems to me very conservative,I am wanderings if there some exceptions in code that allow me to go below 10 psf.

 

[woodman88]

Not sure if I would use it as for reducing the required minimum loading. But, in the 2009 IBC "Section 3105.3 Awnings and canopies shall be designed and constructed to withstand wind or other lateral loads and live loads as required by Chapter 16 with due allowance for shape, open construction and similar features that relieve the pressures or loads..."



Garth Dreger PE - AZ Phoenix area
As EOR's we should take the responsibility to design our structures to support the components we allow in our design per that industry standards.

 

[Ron]

Zeeko83....I've designed hundreds of canopies including many of which were cantilevered. My first impression was that your footings are too small, not too large. I live and practice in a relatively high wind load area and have never used a loading of 10 psf. As woodman88 noted, it is appropriate to use the proper wind load for the area with appropriate shape and other factors applied. In my opinion, you are not meeting the required standard of care if you only apply a 10 psf load. Even the 90 mph min wind speed in most of the country yields higher than 10 psf.

 

[Zeeko83]

Dear Ron thank you very much for your comments.
I will recheck my calculation.However, the covering material is perforated, is there any exception in code to reduce such load in such case?
Thx

 

[Ron]

Unless the covering is a fabric screen....no.

 

[woodman88]

It is a lot of work but you can just apply the wind load along the members not over an area. AASHTO has calculations for the amount of wind load to apply to difference shapes of members that might be helpful if you decide to design this way.

Garth Dreger PE - AZ Phoenix area
As EOR's we should take the responsibility to design our structures to support the components we allow in our design per that industry standards.