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RE: Relative Stiffness of Wood Shearwalls

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Scott,
Compliance is with ICC ES PFC5342 and the frames are designed to comply
within division 04- Metals, section 05400 - Cold Formed Metal Framing.
Design on concrete states the following under the ES report section 2.6.6:
"Normal-weight concrete must have a minimum 2,500 psi compressive strength
at 28 days. The concrete materials must comply with Section 1903 of the 1997
UBC or Chapter 3 of ACI 318-99 (under the 2000 IBC and the 2000 IRC)."

There is no specific reference to ACI 04 that I could find in the ICC
report. 

Hardy's (as well as ShearMax and others) are empirically tested, but the
information I received from both Hardy and Shearmax is that you may use a
straight line interpolation to calculate the deflection and capacity on
non-standard frames that lie between standard frame heights. I was told that
a straight line interpolation (by Hardy Frame) was considered to be
conservative on their 12, 18 and 24" panels only. We did not discuss Frames.
ShearMax will (for a reasonable fee) test any panel height and width that is
non-standard for those wanting more exact information. However, when I posed
the problem I had, I was recommended to use a straight line interpolation to
obtain conservative values.

Dennis


Dennis S. Wish, PE


California Professional Engineer

Structural Engineering Consultant

dennis.wish(--nospam--at)verizon.net

http://www.structuralist.net

 


-----Original Message-----
From: Scott Maxwell [mailto:smaxwell(--nospam--at)engin.umich.edu] 
Sent: Wednesday, May 26, 2004 10:00 PM
To: seaint(--nospam--at)seaint.org
Subject: RE: Relative Stiffness of Wood Shearwalls

Keith/Dennis:

While I am certainly no expert on ICC ES AC 130 (which is the acceptance
criteria that I believe Hardy and other propiertary shearwall manufacturer
must use to gain their ICC ES evaluation report), I do believe that it
does require the manufacturer to test most (if not all) different
configurations of their prefabbed/propiertary shearwall.  This can include
different support conditions (i.e. on concrete foundation, on wood framed
first floor, on wood framed upper floor, etc) as well panel sizes/aspect
ratios.  And I believe that it means that the values that they have in
their report come from testing (although there might be an analysis
option...but from my experience with ICC ES on AC 04 [for SIPs] they are
not too terrible fond of the analysis options at times).

Regards,

Scott
Adrian, MI


On Wed, 26 May 2004, Keith De Lapp wrote:

> I too spoke to Hardy just yesterday before sending my previous email.  The
> point I was trying to make with you was that you said, something to the
> effect...I don't care what the numbers say, I don't combine different
> systems in the same line...  Or something like that, I believe the intent
of
> your thought is clear.  You mentioned that intuition and experience tell
you
> not to.  Which is fine.  I believe clarification may be in order though.
We
> each have "our way" (ie some rational) to add either redundancy or
ductility
> which we believe improves LFRS performance.
>
> I thought the comment you made was liken to forget what P over A plus M
over
> S tell me, I'm gonna do something different.  Now not exactly, but sort
of.
> Considering the world stage this forum is being viewed on, I thought the
> topic warranted further consideration.  To me relative stiffness is
> foundational and I'm sure you agree.  And, I don't take "the numbers" as
> gospel.
>
> But your remarks sounded a bit, "prescriptive" to put it in building code
> terms.  Which surprised be coming from you.  I referenced the Hardy Frame
> because if testing is only used to verify the allowable shear and drift
> based upon calculations, then I don't see a difference with enveloping the
> performance of a plywood wall and a Hardy Frame based on a relative
> stiffness calculation.  There probably isn't a one of us who hasn't used
> steel to reinforce a tilt-up panel opening retrofit for out-of-plane loads
> using relative stiffness.  The elements don't know how the load gets
there,
> they just do what their geometric/material properties demand they do.
>
> Would you recommend a Hardy Frame "Panel" and "Frame" be used in the same
> line?  Or how about a Hardy Frame installed on concrete and another
> installed on a wood sill plate and another installed on wood framing?
Each
> of the above two cases will vary in relative stiffness (all other things
> being equal), now swap in a plywood shearwall and you have the exact same
> problem.  You have to pay attention to their relative stiffnesses to see
how
> the load will be shared throughout the LFRS system.
>
> The preaching is not meant to be belittling in any way, it's just a style
> thing.
>
> Keith De Lapp, P.E.
> KDL ENGINEERING
>   -----Original Message-----
>   From: Dennis Wish [mailto:dennis.wish(--nospam--at)verizon.net]
>   Sent: Wednesday, May 26, 2004 9:09 AM
>   To: seaint(--nospam--at)seaint.org
>   Subject: RE: Relative Stiffness of Wood Shearwalls
>
>
>   Keith,
>
>   I spoke with Hardy the other day and this is not correct. Their values
are
> based on testing and their current ICC reports indicate that the drift
> calculations can be interpolated in a straight line interpolation which is
> considered conservative to their test data. Hardy (Mitek) has been
listening
> to this thread and I would recommend that they respond to your comments.
> They asked if it was appropriate for them to participate and I felt it was
> as long as they were not attempting to sell product. I think they are in a
> better position to respond to you than I am, but I do know that they
> recommended an interpolation of in plane drift based on height changes in
> each frame or panel. Also, as I mentioned, when different panels/frames
are
> used in the same line of shear, the drift/stiffness should be calculated
> based on relative rigidity.
>
>   Shearmax also uses an interpolation for non-standard frame heights. I
have
> not spoken to Simpson or TJ, so others may respond to this.
>

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