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Re: Green Sandwich Technology

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Ben,

I have never had any exposure to Structural Concrete Insulated Panels
(SCIPs...which is what the Green Sandwich panels are), but I have had
exposure (as in I work part-time for a manufacturer) to Structural
Insulated Panels (SIPs).  They are obviously significantly different, but
use similar thoughts (concrete "skins" around EPS foam vs. OSB "skins"
around EPS foam).  Thus, some of the principles will be the same/similar.

I will note that it appears that they may not have a code acceptance
reports (I looked on there website and did not find anything as well as
looking on the ICC-ES website).  Considering information that you had
provided in the past about how the Santa Monica building department works,
this might present a problem.

In some regards, I would say that it could be treated like precast
concrete.  The "tough" part would be how to determine how the two skins
work in combination with the EPS to form the composite section and how
that composite section works.  As the most conservative approach, one
could consider the two skins to just "share" load (i.e. deformation
compatibility...but in truth that is not necessarily accurate either as
one skin could deflect differently than the other if the foam crushes; the
relative strength of the concrete to EPS foam is significantly higher than
the relative strength of OSB skins to EPS).  By and large, good old simple
principles of statics and solid mechanics should likely govern the
composite behaviour...to some degree more so than with SIPs (with SIPs the
shear strength and shear deformation of the EPS foam has a significant
effect on the composite behaviour...I would think that it would be less so
for SCIPs as the concrete skins will likely be so much stronger than the
EPS foam than the OSB realtive to EPS foam in SIPs).  This should handle
much of your non-seismic uses (i.e. roof panels carrying vertical loads,
wall panels carrying transverse wind loads, wall panels carrying axial
loads).  The tougher issue would be performance under seismic loading
inplane (i.e. if used as shearwalls).  To some degree, I would think it
could be treated like R/C shearwalls or precast shearwalls if the concrete
skins are detailed per ACI 318 requirements, but this might be tough
assuming that they are likely using relatively thin concrete "skins".  At
worst, maybe they will just have to use "regular" concrete (either R/C or
precast) shearwalls and use the SCIPs everywhere else...this is what
happens on some SIPs projects (i.e. we just use stick-framed or
proprietary shearwalls rather than try to do SIP shearwalls).

FWIW, I believe that there are some precast manufacturers that make
similar type wall panels.  The PCI Design Handbook has some information on
"sandwich" panels in it (I spotted at least three sets of P-M interaction
diagrams).

If information on SIPs might end up helping you deal with SCIPs, then free
to ask away.  Otherwise, I have probably exhausted my knowledge (if not my
fingers) of SCIPs.

HTH,

Scott
Adrian, MI


On Wed, 24 Aug 2005, Ben Yousefi wrote:

> I was wondering if anybody out there has had any exposure to this
> structural system. We have received our first set of plans for a small
> multifamily project using this system and wanted to see if anyone can
> provide some useful feedback.
>
> Thanks
> Ben Yousefi, SE
> Santa Monica, CA
>
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