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RE: AISC Steel Spec Combine forces question
- To: <seaint(--nospam--at)seaint.org>
- Subject: RE: AISC Steel Spec Combine forces question
- From: "Jason Christensen" <jason.christensen(--nospam--at)es2eng.com>
- Date: Mon, 2 Jan 2006 09:41:15 -0700
Title: RE: AISC Steel Spec Combine forces question
Charlie. I did find in Appendix F of LRFD 3rd edition a more concise
definition of Iyc.
From: Carter, Charlie
December 30, 2005 8:26 AM
Subject: RE: AISC Steel Spec
Combine forces question
>I have been reading section H
>of the new steel spec. This
>section is for designing members
>for combined forces and torsion.
>My question is on section H1 ... it
>reads as follows:
>"... where Iyc is the moment of
>inertia about the y-axis referred
>to the compression flange, in.4 (mm4)."
>My question is with the definition
>of Iyc, specifically the use of the
Iyc is just the weak-axis moment of inertia of the
The equation in which it is used in Section H1 is
essentially requiring that there be a compression flange. That is, if the ratio
of Iyc to Iy is less than 0.1 the compression flange is too small for the
behavior to be properly predicted with the provisions in Section H1.
Likewise, if the ratio of Iyc to Iy is greater than 0.9, the tension
flange is too small for Section H1 provisions. In either of these cases, the
provisions in Section H2 are more appropriate.
Thanks for pointing out that the "referred to"
phrasing is a bit ambiguous.