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RE: 2000 IBC v 1999 UBC code question - 2

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Ben: 
 

"AISC Seismic Part III (ASD) section 4.2 modifies the allowable
stress increase of 1.33  in ASD A5.2, that you refer to, to 1.7.

This is the same as the 1997 UBC 2213.4.2. This section merely says that to
determine the strength for multiply the allowable stress by 1.7 without the
1.33 increase. The strengths of certain elements and components of the
lateral force system need to be sufficient for special load combinations or
the capability of the system to deliver force to them, regardless of whether
ASD is used.  

The ASD load combinations should be checked as well as requirements in the
seismic chapter.  The 1.33 increase applies to wind design as well as
seismic.  I will not argue that the IBC is a little more confusing here
since it uses the standards and they don't quite jive,  but the 97 UBC is
confusing in this regard too.


Respectfully,   

Scott M Haan P.E.
Plan Review Engineer
Building Safety Division 
Development Services Department
Municipality of Anchorage
http://www.muni.org/building
phone:907-343-8183  
fax:907-249-7399
mailto:haansm(--nospam--at)ci.anchorage.ak.us



-----Original Message-----
From: Yousefi, Ben [mailto:Ben.Yousefi(--nospam--at)ci.sj.ca.us]
Sent: Tuesday, October 30, 2001 2:42 PM
To: 'seaint(--nospam--at)seaint.org'
Subject: RE: 2000 IBC v 1999 UBC code question


	Scott M Haan P.E. wrote

	AISC ASD 89 A5.2 allows a 1.33 increase.
	AISI Spec. A5.1.3 allows loads to be reduced.
	ACI 530-99 2.1.1.1.3 allows a 1.33 increase.


	Scott:

	In regard to 2000 IBC and steel design:

*	The Material section 2212.1 refers to AISC Seismic for seismic
design of building. 
*	AISC Seismic Part III (ASD) section 4.2 modifies the allowable
stress increase of 1.33  in ASD A5.2, that you refer to, to 1.7. However,
section 4.1 requires a load combination very similar to the LRFD and section
4.3 requires resistance factors for member strengths similar to LRFD also.
*	So, what we end up with, as far as ASD design for seismic is
concerned, is a hodgepodge of a methodology that, in my opinion, forces the
designer to use LRFD and get it over with.

Ben Yousefi, SE
San Jose, CA



	 

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