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>I recently saw a calculation of a rigid frame with tapered members. In the
>columns I saw the effective length factor K. When I asked if that was right,
>that it should be Kgamma according to appendix F of AISC, they answered me
>that "most" metal building manufacturers in the U.S. don't use that

>Can anybody tell me what is the common design practice for metal buildings
>in the US then? What do they use and how do they do it?

I'm not aware of anything that's technically wrong with the provisions we have in Appendix F, but we are aware that few metal building manufacturers seem to use them in the design of tapered members. It seems to be a case of the difficulty (real or perceived) of applying the Appendix F provisions in a computer solution. I'm not sure why because the existing provisions provide a way to account for a tapered member while modeling it as a prismatic member.

I've seen solutions that model the tapered member as a series of a whole lotta (technical term) prismatic segments. I presume (hope) that the corresponding K factor was selected as for a stepped column.

We have a task group of our Committee on Specifications that is working on a proposal for a replacement to the current provisions.