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Re: CONC Slab Uplift

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ACI-318-95 is for "Structural" concrete.  A slab on grade is not
considered a structural element for resisting uplift (see chapter 22).

My suggestion is to saw-cut out the slab around the column and add
enough concrete (with rebar dowels/pins) to the existing footing to
provide a total dead load of 1.5 times the uplift, and disregard the
weight of the slab.

Lew Midlam, PE


Sickler wrote:
> First, thanks to all who responded to my request for repeat of
> information on concrete slabs for machinery.  I received exactly
> the information I needed.
> I have another concrete slab question that I could use some
> help with:
> I am evaluating a 4" slab on grade with no edge beams or footings.
> At one column location, there is an uplift load of 2.5 kips.
> Given that the slab is thin and flexible, it would appear that
> the uplift load would engage a portion of the slab in bending.
> The highest uplift reaction occurs in the middle of the slab, away
> from the edges; but I am also interested in behavior near the edges.
> How would you determine what portion of the slab resists the uplift
> load and then how would you evaluate the design moments in the slab?
> Any suggestions or references would be greatly appreciated.
> Thanks,
> Nina Sickler