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RE: '97 UBC Lateral Design - Envelope Solutions???? Calmed down r eply[Subject Prev][Subject Next][Thread Prev][Thread Next]
- To: "'seaint(--nospam--at)seaint.org'" <seaint(--nospam--at)seaint.org>
- Subject: RE: '97 UBC Lateral Design - Envelope Solutions???? Calmed down r eply
- From: "Swingle, Mark" <Mark.Swingle(--nospam--at)dgs.ca.gov>
- Date: Fri, 24 Sep 1999 11:56:21 -0700
- Cc: "'mswingle(--nospam--at)earthlink.net'" <mswingle(--nospam--at)earthlink.net>
"Sorry, I might have lost my temper...." (MS) Dennis, I am sorry too, I do appreciate your efforts and persistence. I guess I have just lost my patience, and I was trying to get your attention. However, my tone was uncalled for. ------------------- "There can be only one answer. 1. If the diaprhagm deflection is less than 2 times the story drift the analyisis distribution of shear through the diaprhagm is calculated considering the contribution of shear from torsion in the diaprhagm. 2. If the diaprhagm deflection is equal to or greater than 2 time story drift, the shear may be distributed through the diaphragm by tributary area. 3. A combination (envelope) of the above." ------------------ (MS) Perhaps it is only my inability to write clearly, because you apparently still don't see what I am saying. I will try again. 1. Within item 1 above is a whole range of possibilities, not just one answer. The range includes 100% rigid at one extreme and 100% flexible at the other extreme. 2. Item 2 is one of these extremes, that of 100% flexible diaphragm (tributary force). 3. By item 3 I assume you mean using the highest force obtained for each wall using each extreme method. The code does not require this, however, you may do it if you like. The code says you use item 2 above if the diaphragm meets the test (>=2x). Or use forces derived from item 1 if the test is not met (<2x), but that's the hard part. What I hope is that we can move the discussion beyond what the code says and toward developing the analytical tools required to comply with what the code says. (I also think that we should continue to lobby to have this portion of the code changed, with whatever means there are available to us. That will be a different post.) I know you have spent considerable time in using the sw deflection formula for wood walls. I am interested in your thoughts and/or experience with the use of these formulas. The most important piece in this puzzle is the stiffness of the WALLS, not the stiffness of the diaphragms. I still don't know how one can determine the forces to the walls assuming 100% rigid diaphragm when the shear wall deflection equations are so poorly defined, limited in scope, subject to interpretation, and non-linear. I would be interested in your methodolgy with regard to determining wood sw stiffnesses. Mark Swingle, SE Oakland, CA Disclaimer: these are my own opinions and are subject to change.
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