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Re: CONC Slab Uplift

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> 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
> 
I would never try to resist a 2.5 kip uplift with a 4" slab.  You would
need 50 square feet of slab to have enough mass to resist the force.  I
don't know the details but it seems you need to have a foundation poured
or a caisson drilled to resist the 2.5 kip force.

Jim Dane, P.E.