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Re: IBC Special inspection for Slab-on-Grade supporting HVAC unit.

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Bob,

Actually, Elias was not stressing about the design of the SOG for 1 kip
HVAC...it is/was impossible to tell if he had questions about the design
portion of the SOG from his post.  His post was focused on whether he
needed to do Special Inspection for this particular SOG.  He did not feel
that there was much guidance/clarity in the code, even though it turned
out there was (i.e. an exception for SOGs).  So, I cannot guess if he was
obsessing over the design of the SOG or not...and his concern about
whether or not Special Inspections are/were required is valid as Special
Inspections are generally some new to a lot of people.

And yes, while I was overly sensative, your post was written is such a way
that it appeared critical (not the right word...but I am at a loss at the
moment for a better one).  But, then that is the joy of email...it is WAY
to easy to have some of the intent/essence of what you want to say be lost
if the black and white letters...which is also a challenge of writing code
language.

Regards,

Scott
Adrian, MI


On Fri, 27 May 2005, Robert Kazanjy wrote:

> Scott-
>
> Don't your panties in a bunch.  You're being way too senstive.
>
> I was trying to emphasize (not necessarily to you) that a simple SOG
> may not be so simple.  They're not always just something to keep the
> dirt out of the building.
>
> In my post I should have said "one's howework"  rather than "your
> homework"; which could have implied the specific "you" (Scott) when I
> really meant the general "you" (one).
>
> My main point was that Elias had totally lost sight (if he ever had
> sight)  of common sense reality & was way too focused on finding (in
> the wrong spec) something to hang his hat on; the typical refuge of
> the code monkeys who seem to predominate in the CE/SE world.
>
> Come on, he was stressing & obsessing)over a pad for a 1 kip HVAC unit
> even after Stan had tried to enlighen him!  Unless it was back life
> support for the space shuttle it seemed pretty much like a no
> brainer..
>
> My secondary point was that a "simple SOG" can bite one in the ass if
> one is not careful.
>
>
> JMO / YMMV
>
> cheers
> Bob
>
>
>
> On 5/27/05, Scott Maxwell <smaxwell(--nospam--at)engin.umich.edu> wrote:
> > Bob,
> >
> > I am curious...where in my post did I say that a non-structural slab such
> > as SOG with wheel loads did not need to be properly designed (i.e. "doing
> > your homework")?  That is funny, I don't recall ever just saying or
> > implying that you just pick a slab design out of thin air with no design
> > or thought.  Must be my imagination.
> >
> > My point was that a SOG with wheel loads is still technically not a
> > structural slab (which you seem to agree with).  It _STILL_ needs to be
> > designed properly.  It is just that the slab its self is not design purely
> > to take the load by structural action back to some other element.  The
> > load is largely transfered to the ground directly through the slab by
> > direct bearing not "spanning" or bending.  It still definitely requires
> > design so it will not fail (i.e. deform, crack, settle locally, etc) under
> > the applied load (i.e. wheel load).
> >
> > Regards,
> >
> > Scott
> > Adrian, MI
> >
> >
> > On Fri, 27 May 2005, Robert Kazanjy wrote:
> >
> > > Elias-
> > >
> > > Are there no senior engineers with common sense to share at your firm?
> > >
> > > Stan gave you an ecellent answer.
> > >
> > > Scott, while a SOG that is subject to wheel loads (esp hard tire
> > > forkf) may not strictly be a structural slab, not doing your homework
> > > could cause everyone involved  a lot of headache.
> > >
> > > cheers
> > > Bob
> > >
> > > On 5/27/05, Scott Maxwell <smaxwell(--nospam--at)engin.umich.edu> wrote:
> > > > Elias,
> > > >
> > > > Stan basically answered your question...but to say it a again, SOGs are
> > > > generally NOT structural.  Technically, it is the SOIL that is doing the
> > > > "work" not the slab.  For a SOG, the slab will generally be designed to
> > > > minimize cracking if the soil does consolidate in local spots, but the
> > > > whole idea of a slab on grade is that it is the soil that is supporting
> > > > the loads.  This is precisely why ACI 318 does not apply to SOGs...they
> > > > are non-structural and ACI 318 is for STRUCTURAL concrete.
> > > >
> > > > I will kind of disagree with Stan some...if the SOG is designed for wheel
> > > > loads, I believe it is still considered to be non-structural.  For such
> > > > conditions, it is still generally the soil that takes the load with the
> > > > slab being "stiffed" to help spread the load a little more.  If the SOG is
> > > > designed to span some distance, then it might be considered structural.
> > > >
> > > > Thus, the "non-structural slabs supported directly on ground" exception
> > > > that you cite applies to your case...at least based upon the information
> > > > that you gave, that would appear to the be the case.
> > > >
> > > > Regards,
> > > >
> > > > Scott
> > > > Adrian, MI
> > > >
> > > >
> > > > On Fri, 27 May 2005, Elias Hahn wrote:
> > > >
> > > > > I tend to agree, but I can't find anything to cite.  There are only four
> > > > > exceptions given in the IBC - Isolated spread footings (under 3 stories),
> > > > > Continuos footings (some requirements), "non-structural slabs supported
> > > > > directly on the ground." and some foundation walls.
> > > > >
> > > > >
> > > > >
> > > > > So, my follow-up question - what differentiates a structural slab and a
> > > > > non-structural slab?
> > > > >
> > > > >
> > > > >
> > > > >   _____
> > > > >
> > > > > From: Arvel L. Williams, P.E. [mailto:awilliams(--nospam--at)gwsquared.com]
> > > > > Sent: Friday, May 27, 2005 12:52 PM
> > > > > To: seaint(--nospam--at)seaint.org
> > > > > Subject: RE: IBC Special inspection for Slab-on-Grade supporting HVAC unit.
> > > > >
> > > > >
> > > > >
> > > > > Elias,
> > > > >
> > > > >
> > > > >
> > > > > Unless the existing building is in a use category that is considered life
> > > > > essential.  Such as a hospital, water plant, etc.
> > > > >
> > > > > Even then, its a long shot on this type of foundation.  Special Inspection
> > > > > is usually required only on deep foundations, deep fill, some type of
> > > > > structural steel, pre and post tension concrete and a few other items that
> > > > > are "special applications" and all building 3 stories and taller.
> > > > >
> > > > >
> > > > >
> > > > > So, for your little mat, I would say no.
> > > > >
> > > > >
> > > > >
> > > > > Arvel
> > > > >
> > > > > -----Original Message-----
> > > > > From: Elias Hahn [mailto:ehahn(--nospam--at)eepdx.com]
> > > > > Sent: Friday, May 27, 2005 1:22 PM
> > > > > To: seaint(--nospam--at)seaint.org
> > > > > Subject: IBC Special inspection for Slab-on-Grade supporting HVAC unit.
> > > > >
> > > > > I recently designed a SOG (~10'x15', 6" thick, thickened edge) for a HVAC
> > > > > unit (~1000lbs) for an existing building.  Our standard general notes call
> > > > > for special inspection for steel and concrete placement.  Is this
> > > > > applicable?  There is very little good information on SOGs in either the IBC
> > > > > or ACI 318.
> > > > >
> > > > >
> > > > >
> > > > > Thanks in Advance,
> > > > >
> > > > > Elias Hahn, EIT
> > > > >
> > > > > Evergreen Engineering, LLC
> > > > >
> > > > >
> > > >
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