canopy CFS

[McGill10]

Hello All,
We are designing a Canopy using Cold Formed Steel.As we want to create a long span,as a general experience how long CFS members can span? I found 16" member as deepest size studs and planning to make a box section by attaching two members toe to toe and spanning about 30 ft unbraced length.
Does this sound resonable? Any thoughts/experience appreciated.

 

[CANPRO]

Typical PEMB have cold formed purlins spanning about 20'-25' so it sounds reasonable. If you're going to double up your steel studs wouldn't it be easier to connect them together toes out? Might not be as strong as the box section, but 2 - 16" members should be able to span 30'

 

[McGill10]

This member has 8 ft tributory of 45 psf wind uplift load (it's a major beam/girder).As unbraced length of 30 ft gives very little capacity being long unbraced length. I am assuming toe to toe connection makes it a tube member and avoid torsional buckling giving almost full member flexural capacity.
But I don't know how to check it-Is there a spreadsheet or something available to calculate the member capacity of such sections.

 

[strucguy]

McGill -

We use LGbeamer in our office to design CFS members. You may want to check that. Good Luck!

 

[BAretired]

Not a good idea to rely on a spreadsheet to do something which you do not know how to check.

BA

 

[XR250]

I would connect them web to web - much easier. What ever you do, make sure you use 2 members per rafter. At these spans and depths, CFS members are really unstable. It actually sounds like pre-engineered trusses would be better or even red-iron. If it wasn't for the steel erectors raping the GC, red iron would be used more often in these situations.

 

[CANPRO]

The manufacturer of the CFS members will have all of the section properties you need...you can build your own spreadsheet from there. The cold-formed steel code is a pain in the ass but still fairly straight forward.

How do you intend to connect toe to toe? The only thing I can think of is wrapping the members with sheet metal every couple of feet.

 

[XR250]

AISIWIN is a free download and will do this analysis for you.

 

[hokie66]

30' unbraced in light gauge purlins? Did you forget the bridging?