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RE: 1997 UBC Section 1634 - Non-building Structures question

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I would agree with Ed's conclusion that UBC Section 1634.5, including its required minimum seismic forces, appear to be intended to apply to nonbuilding structures that are not similar to buildings and that are designed using R-factors from Table 16-P (even though not explicitly stated that the minimums do not apply to UBC Section 1634.2).  Otherwise, if one were to read it that 1634.5 applies to all nonbuilding structures, then the R-factors from Table 16-P would apply to all nonbuilding structures and Section 1634.2 would not seem to have much applicability.
 

William C. Sherman, PE
(Bill Sherman)
CDM, Denver, CO
Phone: 303-298-1311
Fax: 303-293-8236
email: shermanwc(--nospam--at)cdm.com

 


From: Soojin, Hur [mailto:sjhur(--nospam--at)hec.co.kr]
Sent: Wednesday, March 22, 2006 9:30 PM
To: seaint(--nospam--at)seaint.org
Subject: 1997 UBC Section 1634 - Non-building Structures question

This is old subject, but ongoing one in my project.
Even though I found there was discussion on this subject, but I can't trace the result of it.
Is there anyone, who know the final conclusion of Mr. Ed's question below?
 
Thanks for anyone's input in advance.
 
Soojin, Hur
/PE, Korea
 
-----Original Message-----
From: Ed Marshall [
mailto:elmarshall(--nospam--at)HASimons.com]
Sent: Tuesday, September 21, 1999 5:18 PM
To: 'seaint(--nospam--at)seaint.org'
Subject: 1997 UBC Section 1634 - Non-building Structures question

Section 1634.5 of the 1997 UBC specifies increased minimum seismic loads for
"Other Nonbuilding Structures" relative to those for buildings.  It says
that nonbuilding structures not covered by Sections 1634.3 & 1634.4 shall be
so designed.  Section 1634.3 covers rigid structures and Section 1634.4
covers tanks with supported bottoms.  Section 1630.2 (non-building
structures with structural systems similar to buildings) appears not to be
exempted from the increased minimum.

In contrast, in the 1994 NEHRP Recommended Provisions and in ASCE 7-95, the
exception applies to all three categories (rigid structures, tanks with
supported bottoms, and non-building structures with structural systems
similar to buildings).   See NEHRP section 2.7.5 and ASCE 7-95 section
9.2.7.5.

It seems that logically the exception should apply non-building structures
with structural systems similar to buildings since the R factor is typically
coming from UBC Table 16-N rather than Table 16-P.   I'm inclined to assume
this is a typo in the code (although I don't find it corrected in the
Errata).  Does anyone know of any other reason why the 1997 UBC deviates
from the 1994 NEHRP Recommended Provisions in this regard?

Ed Marshall, PE