To: "'seaint(--nospam--at)seaint.org'" <seaint(--nospam--at)seaint.org>
Subject: RE: IBC special seismic load combinations for steel design
From: Scott Maxwell <smaxwell(--nospam--at)engin.umich.edu>
Date: Thu, 5 Apr 2001 21:45:03 -0400 (EDT)
It may not matter, but then again...be careful...while I can't see any
real problems because Supplement No. 2 is "more complete", the 2000 IBC
_DOES_ not refer to Supplement No. 2 at all...it references Supplement No.
1 only. Thus, strictly speaking, the "letter of the law" (so to speak) is
1997 AISC Seismic Provisions with the 1999 Supplement No. 1.
There may be a "code cycle" change than has updated the 2000 IBC (or will
shortly) to use Supplement No. 2...I believe that a supplement to the IBC
is in the works. Someone from AISC maybe able to comment...Charlie are
you out there?
On Thu, 5 Apr 2001, Haan, Scott M. wrote:
> Thanks again Scott.
> You can download the supplement for free. I do not see any revisions
> pertaining to this issue.
> Scott M Haan
> Plan Review Engineer
> Building Safety Division http://www.muni.org/building
> Development Services Department
> Municipality of Anchorage
> phone:907-343-8183 fax:907-249-7399
> -----Original Message-----
> From: Scott Maxwell [mailto:smaxwell(--nospam--at)engin.umich.edu]
> Sent: Thursday, April 05, 2001 4:22 PM
> To: Seaint list (E-mail)
> Subject: Re: IBC special seismic load combinations for steel design
> While I can really answer your question (don't have the time to look at it
> and then switch off the "brain power conservation mode" at the
> moment...plus I am sure someone else with more brain power will respond),
> I can ask a dumb question. Are you using the 1997 AISC Seismic Provisions
> WITH the 1999 Supplement No. 1? This is actually what the 2000 IBC
> references. I don't know if the Supplement No. 1 deals with the sections
> that you are dealing with since I cannot located my electronic copy of
> Supplement No. 1 and AISC seems to have removed it from their web site.
> HTH, but likely does not...
> On Thu, 5 Apr 2001, Haan, Scott M. wrote:
> > Hello everyone:
> > IBC 1605.4 indicates the IBC special seismic load combinations [combos
> > Em] are required where required by Sections 1613 through 1622 or by
> > 18 through 23. Chapter 22 does not specifically require the special load
> > combinations. IBC Section 2212.1.2 requires steel structures to be
> > and detailed in with AISC Seismic Part I or Part III and there are no
> > amendments to AISC Seismic. AISC Seismic Part 1 Section 8.2 indicates to
> > use the AISC "additional load combinations" for column design when
> > Pu/[phi*Pn]>.4.
> > IBC 1617.1.2 special seismic load combinations Em include a vertical
> > component of + - .2*SDS*D. The AISC Seismic Part 1 Section 4.1 OMEGAo*Qe
> > load combinations do not include the + - .2*SDS*D and the section
> > Qe is the horizontal seismic affect.
> > Is this an oversight that the IBC adoption of the AISC Seismic Provisions
> > not amended to specifically require the use the IBC special load
> > combinations? Why-why not? The IBC special load combinations require the
> > additional .2*SDS*D vertical effect and this can be significant for a
> > multistory building.
> > PS. IBC 1605.1 indicates buildings need to be designed for the load
> > combinations indicated in 1605.2 and 1605.3 and the load combinations in
> > chapters 18 through 23. IBC 1605.1 also indicates buildings need to be
> > designed for the special seismic load combinations when required by
> > 1620.1.7 or Section 1620.3.5. This appears to be a misreference and it
> > appears 1620.1.6, 1620.1.9 and 1620.3.4 are intended.
> > Respectfully,
> > Scott M Haan P.E.
> > Plan Review Engineer
> > Building Safety Division http://www.muni.org/building
> > Development Services Department
> > Municipality of Anchorage
> > phone:907-343-8183 fax:907-249-7399
> > mailto:haansm(--nospam--at)ci.anchorage.ak.us