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Re: SIP top plate detail

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I would offer a word of caution...to my knowledge, no SIP manufacturer has
an ICC evaluation report that includes evaluation for use of SIPs as
shearwall in high seismic areas (specifically Seismic Design Catergories
D, E, or F).  The ICC-ES acceptance criteria for SIPs (specifically AC04)
did not have any provisions even in draft or non-finalized form for
evaluation of SIPs for seismic categories D, E, or F until approximately
2 years ago and those provisions were not "finalized" until several months
ago (I believe that they are finalize now).  Thus, to my knowledge, no SIP
manufacturer has been able to complete the required testing and get an
evaluation report through the complete process that includes shearwall
values for use in high seismic area.

The high values that you referred to in Premier's report I believe are
only applicable for wind or "low" seismic area (i.e. Seismic Design
Catergories A, B, and C per IBC...rougly equivalent to UBC Zones 0, 1, and
2a maybe).  Their latest report (at least that is available on the ICC-ES
site) is dated as being "re-issued" in March of 2004 and none of the
testing listed in the "evidence submitted" is later than sometime in 2003.
So, I doubt that they have any of the testing that was done per Appendix A
(which is now where the seismic testing of SIP shearwalls is in AC04)
since Appendix A was not officially first "published" in AC04 until around
March 2004.  Their only shearwall testing for that report is likely under
monotonic loading, not the cyclic loading that is now part of Appendix A.

I pretty sure that Premier is pretty close to getting their seismic
evaluation completed, but I don't think it is out there yet.

The point is that any shearwall/racking load values that you see in a SIP
ICC (or NER etc) evaluation report is likely only really applicable for
wind or "low" seismic (Seismic Design Categories A, B, and C).
Unfortunately, to my knowledge, none of the manufacturer's (and that
includes the one that I work for) specifically informs users of that in
the report.  The reports, unfortunately, are silent on the issue and thus
give the impression that the values included can be used for high seismic
loads.

This is not to say that SIPs cannot handle high seismic loads.  They can.
But, they (like other materials/system) need to detailed in a specific way
to achieve the desired ductility for resisting seismic loads.  SIPs in
general are rather stiff and brittle when loaded as shearwalls...at least
compared to stick-framed walls.  They can actually achieve higher loads
than comparable stick-framed walls, but behave in a less dutile manner.
That is unless you actually make your SIP shearwall with at least one
panel joint in the middle of the shearwall (i.e. make the shearwall out of
two SIP panels).  If this "simple" change in introduced, then SIP
shearwalls achieve a ductile response that is much more like a
stick-framed shearwall.

So, hopefully someone mention this issue to you so that you could be aware
of it.  When I assist EORs with SIP on California projects for our panels,
I am clear to inform them of this.  In the relatively near future, it will
not be an issue as new evaluation reports from the various SIP
manufacturer's will be available that include evaluation for use of SIPs
as shearwalls in high seismic areas.

Regards,

Scott
Adrian, MI


On Sat, 4 Feb 2006, Tim Rudolph, PE wrote:

> Hi Scott
> I recently did a SIP house in California in Seismic Zone 4 with a 95 psf
> snow load.  The holddowns I used were the simpson ATS system along with
> custom splines.  Premier Panels had a design for the splines 2 pieses of LVL
> 2x8 with a foam inside that has a 1.5" dia hole for the all thread rod. (
> the hole they core in the foam is the same as for the electrical) I used a
> steel bearing plate washers on the top plates( 2 -2x8 top plates with a
> 1.125" bearing plate on top of that ) I found that simpson has larger width
> bearing plates available but not listed in the catalogs.  This way the
> holddown system has its bearing plates and rod to rod connections (coupler
> nuts) in the floor systems.  I didn't use TUDS because the wall and  floor
> is mostly Engineered lumber.
> It seems that Premier was some what secretive and didn't provide details on
> this.  I found out about this from a consulting engineer they refered me to
> when the couldn't answer my techinical questions about SIPS.  But once
> specified on the plans the said we'll build what you drew.  I still think
> the sales guy is sorta clueless on the system but wanted a sale.  ( we went
> with premeir because of the loads available for the shear walls in the ICC
> report) I found if you have technical questions on SIPS  ---Todd from
> R-Control is the main PHd  PE behind testing and design.
>
> Tim Rudolph
> Bishop,CA
>
>
> From: Scott Maxwell <smaxwell(--nospam--at)engin.umich.edu>
> To: seaint(--nospam--at)seaint.org
> Subject: Re: SIP top plate detail
>
> Howard,
>
> Is you company working on more "SIP" friendly higher capacity (i.e. anchor
> bolt style) hold-downs?  Your PHD and TDX style hold-down (as well as
> similar hold-downs from other manufacturers) can work, but are a challenge
> to work with when doing SIPs.  They kind of create a nice non-insulation
> "void" in the SIP and they can then also act as a thermal break (i.e. a
> big hunk of metal in within the panel).  The biggest issue is that they
> are a challenge to use/install as one does not have easy access to the
> hold-down like one would have with a stick-framed wall.
>
> The reason that I ask is that we are looking for a better solution since
> we are starting to get more and more projects in areas with high seismic
> (i.e. California) and high wind (East Coast hurricane zone).  These areas
> usually end up with some SIP shearwalls with rather significant
> overturning forces that exceed strap style hold-downs (i.e. your STAD
> hold-down) capacities.
>
> Thanks,
>
> Scott
> Adrian, MI
>
>
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