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RE: Philosophy: Seismic Design Standards

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Actually, Rw is 8/K.  But the simple act of moving the coefficient to the
denominator improves the formula by identifying the coefficient more
directly with a structural property.  

Following is a conversion from the "old UBC" formula to the "new" formula,
that I developed a number of years ago; the "new" formula has changed some

V=ZIKCSW can be converted to the new formula by replacing the coefficients
with the following: 
	Z=2.5*Z	 (e.g., 2.5*0.40=1.0 zone factor)    
	C=C/20	 (e.g., CSmax=2.75/20=0.14)    
	K=8/R	 (e.g., 8/6=1.33 for shear walls)    
so: Z=ZIKCSW=(2.5*Z/)I(8/R)(C/20)SW=ZICSW/R. 
(Based on the SEAOC Commentary.)   

> -----Original Message-----
> From: Roger Turk [mailto:73527.1356(--nospam--at)]
> Sent: Wednesday, January 19, 2000 6:36 PM
> To: seaint(--nospam--at)
> Subject: RE: Philosophy: Seismic Design Standards
> Bill Sherman wrote:
> >>Code formulas and coefficients should correspond to 
> identifiable quantities.
> This is one area that I think improvements have been made in 
> the seismic
> codes over the years, e.g. I couldn't relate to "K" in the 
> formula ZIKSW,
> but I can relate "R" to ductility in the formula ZICW/R; and 
> I can relate to
> Aa=0.40 better than "Zone 4".  Also, commentaries and design 
> examples help
> greatly when trying to interpret the real purpose of code language.<<
> R is simply 1/K!  And was developed that way so that the 
> results of the 
> formula wouldn't change.
> "A rose is a rose ..."
> A. Roger Turk, P.E.(Structural)
> Tucson, Arizona