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RE: Seismic using 2000 IBC / 1997 AISC Seismic Provisions

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AISC does know about the conflict.  Their response has been that although there does appear to be a technical problem in the Scope portion of the provisions, the commentary makes the intent crystal clear - if you use R>3, you have to use the Seismic Provisions.  They haven't corrected as of yet, but plan to with the next supplement or publication.

Some people feel that section 2205.2.1 of the 2003 IBC is clear enough to stand on its own - it says...

"Structural steel structures assigned to SDC A, B, or C...shall be of any construction permitted [by the strucural steel section of IBC].  An R factor as set forth in Section 1617.6 for the appropriate steel system is permitted where the structure is designed and detailed in accordance with [the AISC Seismic Provisions]. Systems not detailed in accordance with the above shall use the R factor in Section 1617.6 designated for 'steel systems not detailed for seismic.'" 

In 2000 IBC the equivalent section is 2212.1.1

-----Original Message-----
From: Scott Maxwell [mailto:smaxwell(--nospam--at)engin.umich.edu]
Sent: Wednesday, May 21, 2003 8:08 PM
To: seaint(--nospam--at)seaint.org
Subject: RE: Seismic using 2000 IBC / 1997 AISC Seismic Provisions


If I recall correctly, Charlie is already aware of this issue.  I seem to
recall someone else mentioning it on the list in the last several months.
It was noted that the issue was known and "corrected" in the latest
version of the AISC Seismic Provisions.  As I am getting old and senile, I
could be remember incorrectly, however.

With regards to Seismic Design Category A...for the 2000 IBC, it is my
understanding/interpretation that you must only meet the requirements of
section 1616.4.  This section includes a "minimum lateral force"
calculation method that would "replace" the base shear from the equivalent
lateral force procedure.  In addition the section has a few detailing
requirements.

This is consistant with what was present for "older" codes (i.e. the BOCA
codes) that made use of older versions of the NEHRP provisions.  Seismic
Performance Catergory A buildings (similar to Seismic Design Catergory A
except the soil type is not use in determining the SPC) basically did not
have to be "analyzed".  They only had to meet minimum detailing
requirements.  This is also similar (assuming I recall correctly) to how
the UBC treated Zone 0 buildings, except Zone 0 buildings did not have any
requirements if I recall correctly (but may not since I am not from UBC
country).

HTH,

Scott
Ypsilanti, MI


On Wed, 21 May 2003, Jake Watson wrote:

> I don't know what to think of the SDC comment other than the IBC will still
> tell you what kind of system you can use and then kick you to specific AISC
> sections.  For example, Ordinary steel braced frames in IBC Table 1617.6
> sends you to AISC Seismic Chapter 14.  That completely bypasses that scope
> section.  It looks like that scope section is another note that should be
> flagged for Charlie.
>
> I was told in a seminar that with the IBC, EVERYBODY had to determine base
> shear for their building.  I work in SDC C and above, so I never checked the
> validity of that statement.  But it appears from your reference that once
> you know that you are in SDC A, you are done with seismic.  You should know
> however, that section 1603.1.5 requires the base shear to be on the design
> documents.  Don't what good that does, if it's not used for anything.
>
> Hope that helps a little,
> Jake Watson, P.E.
> Salt Lake City, UT
>
> -----Original Message-----
> From: Bruce Holcomb [mailto:bholcomb(--nospam--at)brpae.com]
> Sent: Wednesday, May 21, 2003 1:43 PM
> To: Seaint (E-mail)
> Subject: Seismic using 2000 IBC / 1997 AISC Seismic Provisions
>
>
> IBC 2000, section 2212.1.1 'Seismic Design Category A, B & C' requires
> designers to follow the AISC Seismic Provisions unless designing systems
> designated as "steel systems not detailed for seismic".  In the 1997 AISC
> Seismic Provisions, section 1 'Scope' states "These provisions shall apply
> to buildings that are classified in the Applicable Building Code as Seismic
> Design Category (SDC) D... and higher...".
>
> So the IBC says to use the AISC Seismic Provisions, but the AISC Seismic
> Provisions do not apply to most of the projects I design... SDC A, B & C.  I
> am missing something?
>
> When I design steel framed buildings in SDC B & C, do I follow the AISC
> Seismic Provisions?
>
> Also, regarding SDC A, do I need to following the AISC Seismic Provisions?
> IBC section 1616.6, 'Analysis procedures' "Exceptions: 1. Structures
> assigned to Seismic Design Category A."  If I follow AISC, what do I do...
> SDC A is excepted from seismic analysis?
>
>
> Bruce D. Holcomb, PE
> Butler, Rosenbury & Partners
> 300 S. Jefferson, Suite 505
> Springfield, MO 65806-2217
> ph (417) 865-6100
> fax (417) 865-6102
>
>
>
>
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