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RE: UBC Section 1634

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No.  Your impression is not correct.  I had some hand in writing this, and I am sorry if you are confused.  

The intent is that you either use the conservative provisions of the Section 1634 "Nonbuilding Structures" in its entirety or you are permitted to use the less conservative R values as used in the "buildings" sections if you provide all of the ductility requirements set forth in the "buildings" section.

A skirt supported vessel is a unique entity.  I would not even try to guess what equivalent R value you would have in the buildings section. 

The intent was as follows:
Say you had a pipe rack that was a concentric braced frame.  You could use an R of 2.9 per Table 16-P and be done with it.  But you do have the latitude to use an R of 5.6 per Table 16-N if you also use all the special requirements for concentric braced frames like the amplified connection forces.

Harold Sprague, PE
Krawinkler, Luth & Assoc.

-----Original Message-----
From:	Sassan Parhizgari [SMTP:shahkarp(--nospam--at)]
Sent:	Friday, September 11, 1998 10:58 AM
To:	seaint(--nospam--at)
Subject:	UBC  Section 1634

I'm using the UBC 97 code for the first time and since it's been
completely revised since the last edition
I still have some problems with it. I would appreciate input that would
help me understand some of the parts.

In section 1634 (Loads on non building structures) article 1634.1.2
states that "... reductions in these forces using the coefficient R is
permitted where the design of non building structures provides
sufficient strength and ductility....".

Does this mean that I could divide the minimum base shears obtained by
equations 34-1 or 34-2 by the proper R value?

I'm designing a foundation for a skirt supported vertical vessel with a
height of 86m and a diameter of 5.87m containing hydrocarbons. The rest
of the parameters are as follows:

T=1.87s      Z=0.2 (Zone 2)     R=2.9    
Cv=0.4  Ca=0.28 (Soil profile SD)

Eq. 30-4 would give  V= .09W
According to Eq. 34-2  V=0.2W

But if my impression of article 1634.1.2 is correct I could reduce the
minimum value to .2W/2.9=.07W using the R factor.

I'd appreciate any comments on this matter.

S Parhizgari