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Beam Loading Help

Beam Loading Help

Beam Loading Help

(OP)
I haven't done this in years so I am hoping someone will refresh my memory. I need to find the maximum weight that can be handled safely on structural tubing (ANSI A500) class B - 2 x 2 x 16 ga wall. The weight will be uniformly distributed along a 48" span.  The supports will be fixed at either end.  I know this seems simple but I just want to make sure I am doing this correctly.  Thanks in Advance

RE: Beam Loading Help

If its just strength you are looking for, do the following:
1) Determine Sx of your section.
2) Determine allowable stress (fy) of steel. Normally .66 Fy therfore you have (0.66 X 50)=33 ksi.
3) Determine allowable moment of your section.
Mmax= Fa (in psi) * sx (in in 3)/ 12
4) Mmax= w* l * l/8
 where l is your span (4'-0). This will give you in pounds per foot.
Hope this helps.
Geoff

RE: Beam Loading Help

Double check that you have the right tubing spec- I didn't realize it went down to anything that small and light.  Also, check to make sure it qualifies as compact, or whatever the criteria is (IE, not too thin-walled relative to width).

RE: Beam Loading Help

Possibly also check for crippling of the webs and shear issues at the ends.  If this is a critical member, upsize it - there is essentially no money involved here.  Watch for corrosion issues also.  Especially if it is outdoors or the end fixity is developed by embedding in concrete.

RE: Beam Loading Help

A500 Class B for a square tube: Fy=46ksi, not 50 ksi.

The maximum moment for the fix-fix condition (which occurs at the ends) is =wL^2/12 (not wL^2/8).  

I prefer LRFD method instead of ASD, so I would take .9(Fy)Sx for the nominal moment allowed and compare it to factored max moment.  Then solve for Sx.  This only works if the section compact, and I think in your case, 48" is too long and the walls are too thin, therefore the section is probably non-compact.

RE: Beam Loading Help

No solve for Sx, solve for w.  Whoops, I'm thinking design, not analysis.

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