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Re: Redundancy Factor

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I have received several different interpretations of the application of rho for
light frame construction (plywood shearwalls).  In spite of the tidy rectangles
presented in various ICBO '97 Update courses, I continue to question the
intended inclusion of rho for these applications.

Issue 1:  One interpretation considers the number of 10' shearwalls in a system.
However, I observe that light-frame is most commonly modeled about wall-lines in
this region (Zone 3, Placer/Eldorado/Sacramento/Sutter County, CA). Given that
local models are accepted in this region, I question the incorporation of the
entire area of the level being considered.  If a local model is accepted as the
standard of practice, then it seems reasonable (conservative) to utilize only
the area tributary to the local model.  IMO "rho area" as depicted for a global
model should not be used for local model applications.

Issue 2:  In consideration of rho as applied to wall-lines (local models), I
have had responses from earlier posts that indicate some practicioners consider
the 'cummulative sum of shear-wall units' in a wall line vs the "minimum length
of wall" in the line for the derivation of rmax.

Issue 3:  Rho max selected by   [ a.) entire structure   b.) local model only ]
and  applied to  [ a.2) entire structure   b.2.) local model only ]  {responses
were weather dependant}.

Frustrated, I have applied rho = 1.5  to entire light-frame structures, and have
been pleasantly surprised to find that wind (80 mph, exp B) usually (still)
controls demand forces.

Hope that helps define the clarity of the issue.