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# RE: 'R' Values

• To: <seaint(--nospam--at)seaint.org>
• Subject: RE: 'R' Values
• From: "Thor Tandy" <vicpeng(--nospam--at)telus.net>
• Date: Mon, 5 Oct 2009 16:24:45 -0700

```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

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
>
>
>
>
>
>
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```