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RE: AISC Seismic Provisions for SCBFs

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I appreciate all of the responses to this subject.  All of the responses
helped to clarify some the terms and wording used in the AISC codes.  I
understand the concept of having the brace yield before the connection,
however, I don't understand why I have to meet certain criteria when I
expect an elastic response versus a deformation response.

For example, for most of the Midwest or areas of low seismic forces, wind
forces would generally "control" over the seismic forces.  Since my wind
forces control, my members are designed for elastic responses.  These
members wouldn't be able to reach deformation levels since my seismic forces
are so low.  Since I expect the members to remain elastic, I believe these
members would be considered "force-controlled" members rather than
"deformation-controlled" members.  

I originally thought my problem was determining the strength of the
connection ("brace strength" vs. "transferred by the system").  Now that I
know what "transferred by the system" really means, I find a problem
accepting the criteria for the limiting KL/R ratios.   The member I'm using
for the brace was not selected based on its capacity.  The member was
selected based on the limiting KL/R ratios.  If the KL/R ratios wasn't so
limiting, I wouldn't need a TS10x6.  A smaller TS size would be satisfactory
with regard to capacity.

I've read through the commentaries and the responses to this list concerning
the concept behind why the ratios are limiting, and I agree with the concept
behind it.  However, since I'm expecting elastic responses from my system,
why do I have to meet the KL/R criteria, when the criteria applies to
inelastic responses?

Is there some "fine print" somewhere that says the criteria is only
applicable to deformation/inelastic responses?  At the beginning of AISC's
seismic provisions, it says that the criteria applies to seismic design
categories D or greater.  My building happens to be category "D" so the AISC
criteria apparently applies.

John Connor, EIT
Kansas City, MO