Need a book? Engineering books recommendations...

Return to index: [Subject] [Thread] [Date] [Author]

RE: Redundancy R-factor and new math

[Subject Prev][Subject Next][Thread Prev][Thread Next]
The complete history of this would take a long e-mail and a lot of research.  However, the short answer is R=5.5 is based on the 1997 UBC and all prior UBCs, which were heavily influenced by the SEAOC Bluebook.

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

-----------------------------------------------------------------------
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
-----------------------------------------------------------------------




-----Original Message-----
From: Pinyon Engineering [mailto:Pinyonengineering(--nospam--at)hughes.net]
Sent: Monday, July 23, 2007 12:15
To: seaint(--nospam--at)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


******* ****** ******* ******** ******* ******* ******* ***
*   Read list FAQ at: http://www.seaint.org/list_FAQ.asp
*
*   This email was sent to you via Structural Engineers
*   Association of Southern California (SEAOSC) server. To
*   subscribe (no fee) or UnSubscribe, please go to:
*
*   http://www.seaint.org/sealist1.asp
*
*   Questions to seaint-ad(--nospam--at)seaint.org. Remember, any email you
*   send to the list is public domain and may be re-posted
*   without your permission. Make sure you visit our web
*   site at: http://www.seaint.org
******* ****** ****** ****** ******* ****** ****** ********

******* ****** ******* ******** ******* ******* ******* ***
*   Read list FAQ at: http://www.seaint.org/list_FAQ.asp
* 
*   This email was sent to you via Structural Engineers 
*   Association of Southern California (SEAOSC) server. To 
*   subscribe (no fee) or UnSubscribe, please go to:
*
*   http://www.seaint.org/sealist1.asp
*
*   Questions to seaint-ad(--nospam--at)seaint.org. Remember, any email you 
*   send to the list is public domain and may be re-posted 
*   without your permission. Make sure you visit our web 
*   site at: http://www.seaint.org 
******* ****** ****** ****** ******* ****** ****** ********