Results 1 to 2 of 2

Thread: Determing the Critical Buuckling Load of a 3"x2"x1/8" Angle

  1. #1
    Associate Engineer
    Join Date
    May 2011

    Question Determing the Critical Buuckling Load of a 3"x2"x1/8" Angle

    I want to design a column 83" long using a 3"x2"x1/8"angle. This isn't a standard angle size, so the slenderness ratio is not readily found in most reference books for me to make a quick evaluation. I know angles aren't typically used as columns, but I believe the angle will be useful for this one specific application. I tried using Euler's formula's to get the critical load, but the results I got for the load and stress didn't make sense. It said the critical bucking stress is actually higher than the yield strength of the material. Is there a formula for designing columns with a non-form cross section such as this angle?

  2. #2
    Lead Engineer RWOLFEJR's Avatar
    Join Date
    Mar 2011
    Rochester Pennsylvania
    You've apparently made a mistake using the formula.
    Euler's formula doesn't take slenderness ratio into account. The slenderness ratio is length in inches divided by least radius of gyration... 83 divided by ABOUT .626 = 132.5 That ratio is too high to use Rankine or Gordon formula. (I say about because I used 2 x 2 angle radius of gyration found in book because it should be darned near same as 3 x 2 x 1/8" angle since we're using the least radius of gyration in any of these formula anyway. And... I didn't feel like doing the math. It could be 12 x 2 x 1/8" angle and still be weak and same number on the 2" side. You can grab a Machinery's handbook and do the math in section called "Strength of Materials" where there are formula for Moment, Section moduli, Areas, radius of gyration etc. for various cross sections.) With Euler's should get you ultimate load of 13,004 lbs. with no safety factor and both ends fixed. (The fixed end condition gives the lowest load for added factor of safety.) This assumes an evenly applied load... no shock loads, and a good piece of stock fixed at both ends. That's the point it should buckle. Myself... even if I was stacking bags of foam peanuts on this column I wouldn't go over 1,000 maybe 2,000 lbs. on the thing. Angle iron sucks for use as a basically free standing column. If it's tied to other columns at various locations it can be helped out, but in the typical sense of the word column... you're using the second worst thing available. Worst being a piece of flat stock.

Tags for this Thread

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts