Determination of critical compressive stress without K value?

[StructureMan44]

I am attempting to determine the critical stress, Fcr, without using the effective length factor, K. If I read this correctly; section C-E3 of AISC 360-10 states that the limit between elastic and inelastic buckling can be defined as F¬e=0.44*Fy. If this is true than Fe depends on Fy (and vice versa) which then means that (Fy/Fe)=2.25 and Fcr is then forced to be equal to equation E3-2. Where is the mistake in this thinking?

 

[KootK]

I'm going to assume that we're talking about the direct analysis method based on some of your recent posting. In that case, the critical stress should be based on KL = 1.0L.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[Lomarandil]

The fact that the limit between elastic and inelastic buckling occurs at Fe=0.44*Fy does not mean that Fe=0.44*Fy. Fe=pi^2*E/(KL/r)^2, same as always. As KootK mentions, for DAM, K=1.0.

 

[StructureMan44]

Thanks guys. This wasn't related to the DAM, I was checked the critical stress for a HSS column and was wondering if it's possible to avoid calculating K.

 

[TLHS]

Not without some sort of p-delta or deflection based moment magnification or something. Anything you do to avoid assuming or calculating K is going to be significantly more calculation intensive.

 

[Lion06]

TLHS, don't forget about the reduced stiffness.