The R = 6.0 (as an FYI, this number will be increased to 6.5 in the 2003 IBC and beyond) is based on ASCE7, which is based on NEHRP Provisions, which date back to ATC-03.
Different committees, hence different judgment.
To my knowledge, the safety factor had nothing to do with the difference in committee decisions.
Tom
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Thomas D. Skaggs, Ph.D., P.E.
Manager, Product Evaluation
Technical Services Division
APA - The Engineered Wood Association
7011 S. 19th Street
Tacoma, WA 98466
ph: 253/565-6600
fx: 253/620-7235
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-----Original Message-----
From: Pinyon Engineering [mailto:Pinyonengineering@hughes.net]
Sent: Monday, July 23, 2007 12:15
To: seaint@seaint.org
Subject: Redundancy R-factor and new math
Hi
I was looking at some APA test of plywood shearwalls see that the saftey
factors ar for 2.8 to 3.5 for the testing to the ultimate load capacity.
Then I looked at my enercal software that fits with the 2003 IRC and now
plywood shearwall get a R of 6.0 where the 2001 california building code
(1997 UBC) gives them a R of 5.5. the Redundany value reduces the earthquake
forces based on the type of system to be used.(Iknow the R is made by
comittee not by "science") While we use the chosen system at with a safety
factor applied to the ultimate load capacity of that system. I know we
design to a code that is for life safety and looks to design for the big one
at the "near colapse level" . is the difference in the R=5.5 and the 2.8 to
3.5 safety factor made up in reducing the building peroid thru damage so
then the force on the building is less? If I am to design an addition to a
fire station then the importance factor makes sure that everything remains
elastic thus no damage and the facility remains operational?
Tim Rudolph
Pinyon Engineering
Bishop CA
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