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RE: AWWA D100

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Harold, the Rf factor is shown in D100-96 Section 13.3.3.2.3 and is
discussed in 13.4.1 as relating to site specific response spectra. For
some reason, Rf is lower than Rw. (I need to study this a bit more on my
own time - I don't get why they use a different R-value for a site
specific response spectrum.) 

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

> -----Original Message-----
> From: Harold Sprague [mailto:spraguehope(--nospam--at)hotmail.com] 
> Sent: Tuesday, December 21, 2004 3:22 PM
> To: seaint(--nospam--at)seaint.org
> Subject: RE: AWWA D100
> 
> Albert,
> 
> In response to your particular question, the answer is no.
> 
> You really have me confused.  If you are looking at the D 
> 100-96, the "force reduction factor" is Rw (not Rf) which is 
> really a response factor and is independent of the ground 
> shaking / seismicity.
> 
> It sounds like you are trying to fine tune a tank design.  If 
> so the "out of the can" D 100-96 is not the proper tool.  
> Besides, it is the Z that defines seismicity (recurrence 
> periods) and the ground shaking.  All that aside, the rest of 
> the seismic code world left much of the D 100-96 behind 
> several years ago without MAJOR tweaking.
> 
> To get what I think you want, use the ASCE 7-02, Section 
> 9.14.7.3.  If you want to modify the seismic probabilities, 
> do it within the SDS and SD1 calculations.  Don't modify the 
> R.  You will probably want a site specific response spectra 
> developed for the probability that you desire.
> 
> I would also suggest that you read the FEMA 450-1 and FEMA 
> 450-2, Chapter 14 for the commentary that led to the 
> development of the tank provisions contained in ASCE 7-02.  
> You will find similar changes in the ACI 350.3.
> 
> BTW, the D 100 is in the process of a major upgrade.  I 
> believe that it is being balloted now.  Seismic is one of the 
> MAJOR overhaul areas.
> 
> Regards,
> Harold Sprague
> 
> 
> 
> 
> >From: "Al Grathwol" <AGrathwol(--nospam--at)BoyleEngineering.com>
> >Reply-To: <seaint(--nospam--at)seaint.org>
> >To: "SEAOC List (E-mail)" <seaint(--nospam--at)seaint.org>
> >Subject: AWWA D100
> >Date: Tue, 21 Dec 2004 12:00:35 -0800
> >
> >According to AWWA D100, the force reduction factor Rf = 2.5 
> for a 10,00 
> >year recurrence period.  Is there a methodology for adjusting Rf for 
> >smaller recurrence periods?
> >
> >
> >Albert H. Grathwol
> >Phone (949) 476-3562
> >Fax (603) 971-0200
> 
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