1620.6.1 was in the IBC 2000.  In the 2006 it is gone because most of the seismic requirements are now referenced out to ASCE 7.  Basically, this section required collectors to be designed using the special seismic load combinations.

There are other elements besides collectors that require this and they can be found in ASCE 7 or AISC Seismic Specifications.

JAE,

Thanks for response,
Going back to thread # 726 126245 "pcoiron" who asked the question was using ASCE 7-02 which is referenced by IBC 2003 that's whu I thought you were referencing to 2003IBC.
I have similar situation as he described and I am using 2003IBC. I am in a SDC "C" I have used Equivalent Lateral Force Procedure to calculate my forces and I am trying to find section in a code that says that I don't need to design each element in my frame for special load combinations listed in 1605.4.
Section 1620.2.6 and 1620.2.9 says that but my understanding is that it only applies when the forces were calculated using Simplified Analysis Procedure see 1620.2.
Am I missundersatnding something?
 

I'm not sure that the code is set up to say when you DON'T use the special load combinations, but rather its set up to only say WHEN YOU DO need to use them.  The text of ASCE 7-02, section 9.5.2.7.1 says "Where specifically indicated in this standard...".

Here's some example ASCE 7-02 sections that specifically call out the special load combos with the omega factor:

9.5.2.6.2.11
9.5.2.6.3.1
9.5.2.6.4.2
9.5.2.6.4.3


I could be wrong, but I also don't think that the special load combinations depend on whether you use the Simplified method or not.

Thanks JAE, I appreciate your answers.