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RE: 'R' Values

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Hi Scott.

I'm familiar with the 'R' concept but was trying to see the equivalence of
our Rd*Ro to the US 'R'.

Thanks

Thor

-----Original Message-----
From: Scott Maxwell [mailto:smaxwell(--nospam--at)umich.edu] 
Sent: Monday, October 05, 2009 2:58 PM
To: <seaint(--nospam--at)seaint.org>
Subject: Re: 'R' Values

Hocus pocus.

If I try engage my serious mode...

R vlaues, in theory, are to represent the amount of ductility relative  
to a purely elastic system.  The idea is a purely elastic response  
would have an R of 1.0.  The higher the R value, the more ductile the  
system will behave.

Now, in theory, you can think of this a relative measure of the energy  
of the system response or the area under the curve of plot load vs  
deflection for a system.  Nominally, in theory, a system with an R of  
5 will be able to dissipate 5 times the energy than that of a system  
with a pure elastic response.

In reality, R values have never really been done purely based upon a  
rational method.  The have more been a function of "politics" (i.e.  
Kind smoke-filled backroom agreements).  While they are not complete  
BS, they can not currently be determined from a rational engineering  
method.

In theory, this is potentially going to change.  There is an effort to  
make R values be more rational.  This part of the reason why Appendix  
A of the SIP ICC-ES acceptance requirements was killed (this assumes  
you read my long dissertation post on SIPs for lateral loads).   
Personally, I have lost track of where this effort stands.

HTH,

Scott
Adrian, MI

On Oct 5, 2009, at 4:47 PM, "Thor Tandy" <vicpeng(--nospam--at)telus.net> wrote:

> Showing my ignorance of IBC/UBC through little use thereof.
>
>
>
> What makes up the 'R' value?  I'm trying to align some Hardy Frame  
> table
> values (quoting 'R'= 5.5 & 4.4) with the local 'R' for loads I'm  
> using here
> in BC.
>
>
>
> No doubt apples & oranges .  :^)
>
>
>
> Thanks
>
>
>
> Thor A. Tandy P.Eng, C.Eng, Struct.Eng, MIStructE
> Victoria, BC
> Canada
>
>
>
>
>
>
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