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Rw Factor with additional Question comparing Rigid Diaphragm Analysis.[Subject Prev][Subject Next][Thread Prev][Thread Next]
- To: <seaint(--nospam--at)seaint.org>
- Subject: Rw Factor with additional Question comparing Rigid Diaphragm Analysis.
- From: "Dennis S. Wish PE" <wish(--nospam--at)cwia.com>
- Date: Mon, 16 Nov 1998 20:10:33 -0800
If you are dealing with a box system - light gauge framing and are using plywood shear walls, you may use an Rw of 8. If you are considering Gypsum or Stucco as your shear elements (although I don't recommend this) you must use an Rw of 6. If you use a braced frame (correct me if I am wrong) as part of your box system, then use an Rw of 6. In my opinion, using Rw as 6 when 8 is applicable is a very smart approach that keeps helps compensate for potential field defects. This poses an interesting question - Has anyone compared the wood design example done by Bill Nelson which was part of the SEAoSC wood seminar last February to a flexible diaphragm analysis using plywood shear walls and an Rw of 6? I reviewed Bills design example and would like to poses this observation - although I have not looked at other examples to see if this a valid assumption: In Bill's example (and Bill, feel free to jump in anywhere here - please), he provided both a flexible analysis and then a rigid analysis. Rather than use the results of one or the other, he chose to use the more conservative results down each line of shear from both analysis. Comparing results it seemed that Flexible diaphragm analysis was more conservative for longer shear walls and rigid analysis governed when walls approached their maximum aspect ratio. Therefore, why bother to go through such an extensive analysis (considering that you must still design for Wind, Seismic - Flexible and Rigid) in order to compare results and use the worst case situation for each. 1. The resulting shears are not representative of one condition that governs at the time of action 2. The observation that narrower piers require more shear to be absorbed by more rigid elements. Therefore, why not simply stipulate an arbitrary constant to apply to all shearwalls that fall within a specific aspect ratio range? Dennis Wish PE -----Original Message----- From: T. Eric Gillham [mailto:gk2(--nospam--at)kuentos.guam.net] Sent: Monday, November 16, 1998 3:37 PM To: seaoc list Subject: Fw: Rw Factor Not sure if this is a first post or not. If it is, then more information would be needed to answer, beyond the simplest one of "Check the appropriate code table against the structure you are designing (e.g. concrete bearing wall system vs. concrete shear wall system wherein walls take minimal gravity loading)". T. Eric Gillham PE ---------- > From: LAMPSMITH(--nospam--at)aol.com > To: seaint(--nospam--at)seaint.org > Subject: Rw Factor > Date: Tuesday, November 17, 1998 1:36 AM > > Criteria for selecting Rw factor of 6 vs 8? > >
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