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Re: Flat Slabs

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Michael Zaitz wrote:

> We are looking at a preliminary design for a flat slab floor (at grade)
> supported by precast piles at 12'-6" o.c. each way.  The floor must
> support a 800 psf live load.  We also have a forklift carrying a 7000
> lbs roll of paper (trying to get more information on this).  They have
> not informed us of any rack storage in the building.  At present we are
> looking at a 12" slab as a starting point.

What soil conditions are present at your site?

I have done a couple of these in Louisiana where soil subsidence was the
problem. There, drop panels were not a problem.  Also the live load was 200

You can size the depth of the slab for shear, then determine the maximum
positive moment in the slab and pick bar size and spacing for that moment.
That reinforcing can be placed in two layers each way ( top and bottom).
Then determine the additional top reinforcing that needs to be added at
each pier. Bar lap splices need to be staggered which can be easily
accomplished in the field.

This method does use a liitle more reinforcing than the classical method,
however, it allows the use of unskilled labor to place the reinforcing; it
is easier to review the in- place reinforcing prior to placing concrete
since you can see when the additional reinforcing  over the piers are

Davis G. Parsons II, PE RA AEI
a practical structural engineer
in Fort Worth, Texas

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