Unbraced metal studs in compression

[joshmaughan]

I need to determine the axial compression capacity of a metal stud section that is not braced laterally at all. The hieght is 6.1 feet. The axial load is 400#. I believe all of my software assumes lateral bracing, and I do not have a copy of the AISI Code. I was thinkig of an 350S162-43 or 54. Any help would be much appreciated.

 

[JAE]

I think you'd have to venture into the AISI code for that.

I'm not aware of any manufacturer's tables that publish unbraced studs like that.

Also - I think RISA and a few other programs do analyze light gage steel sections.

 

[AustinStructural]

Download the SSS 5.0 from The Steel Network. It can analyze studs, joists, etc, and you can set the bridging spacing to the height of the stud which would be effectively unbraced over the entire length.

 

[joshmaughan]

Thanks! I have RISA, but i think it assumes bracing of some sort. I could be wrong. I will try the SSS 5.0

 

[MiketheEngineer]

You can set the unbraced length in RISA

 

[msquared48]

I believe that you can also create sections in RISA - at least the 3D version - in order to use the light gage sections.

Mike McCann
MMC Engineering

 

[MonteSanoKid]

I like CFS by Robert Glauz best. You can set the unbraced lengths for x, y, and t axes, like the AISI code requires. I assume this shape is braced for all three axes at each end? Watch out for small bits of eccentricty on the axial load that can rapidy eat up the member capacity by inducing bending. Make sure your software can take this into account. Or, heaven forfend, do it by hand!

Brad Cameron

 

[UcfSE]

You shouldn't be designing without the appropriate code in my opinion. You wouldn't size a hot-rolled steel section without having and being familiar with the AISC Manual, would you?

That said, you can set the appropriate unbraced length in RISA. If you don't know what it is using, look at the member report.

 

[joshmaughan]

Thanks for your help all. I am quite sure RISA does not analyze this correctly. It ignores parts of the code in certain conditions. I think this is one of those conditions......

 

[vato]

If you are using RISA and are unaware of the bracing settings for members, than you better review your work. RISA defaults to full length, no bracing. You must input bracing, Lb, etc. Double check with the Steel stud manufactureres association catalog or a rough check.

 

[joshmaughan]

I know about the bracing lengths in RISA. But if you read about the code checks in RISA, it does not consider certain parts of the AISI code. I just find it very difficult to believe a 10' long 3.5x1.625x43 mil stud can take 1000# in compression, with no lateral bracing, but that is what RISA is telling me. I will get a code and do a hand calc, but I would beware of RISA for this type of condition.

 

[CFSEng]

a 350S162-43 x 10' long unbraced should get you around 790#. Of course this assumes zero eccentricity on the load. If you can't mechanically brace the member I would use back to back studs ][ to make an I or cap the stud with a track to make a 'tube' to help with stability. Good luck with a hand calc, hope you like iterations

check out CFS, well worth the cost if designing metal studs