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

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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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