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RE: UBC Section 1634

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I don't agree with your interpretation of 1634.1.2.  I read it as saying you
can use R in Section 1630 equations only if you have sufficient strength and
ductility to resist the actual motions, otherwise you must use R=1 (fully
elastic response).  Based on your parameters and past experience designing
non-building structures under previous editions of UBC, V=0.2 W sounds right
for strength design level in Zone 2.  0.09W sounds too low even at service
> ----------
> From: 	Sassan Parhizgari[SMTP:shahkarp(--nospam--at)]
> Sent: 	Friday, September 11, 1998 9:58 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)
> I=1.25
> 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.
> Thanks
> S Parhizgari