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# Re: Column with torsion

• To: "?" <seaint(--nospam--at)seaint.org>
• Subject: Re: Column with torsion
• From: Christopher Wright <chrisw(--nospam--at)skypoint.com>
• Date: Tue, 29 Apr 03 08:52:20 -0500

```>The bending I know how to analyze.  Can anyone offer
>some guidance as to how the torsion component affects
>my column interaction?
If it were me, I'd look at interaction between lateral torsional buckling
due to the bending and ordinary Euler buckling. A linear interaction
relationship is probably conservative--the Aluminum Association has a
quadratic interaction between axial compressioin, bending compression and
shear--
fa/Fa + (fb/Fb)^2 + (fs/Fs)^2 < 1 where f is calculated stress and F is
allowable.

I'd also do a very quick finite element calculation on the column to
figure the effect based on Euler buckling. You won't get the same answer
as the AISC column formula but the relative decrease from shear and
bending should be about right. You might be able to do this with a simple
Rayleigh analysis, but it's probably simpler and quicker with FEA.

Christopher Wright P.E.    |"They couldn't hit an elephant at
chrisw(--nospam--at)skypoint.com        | this distance"   (last words of Gen.
___________________________| John Sedgwick, Spotsylvania 1864)
http://www.skypoint.com/~chrisw

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