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Slab on Grade Point Load
3

Slab on Grade Point Load

Slab on Grade Point Load

(OP)
I have an 'infinite' slab on grade with a point load applied in the middle having an area of A in2. It is supported on a uniformly compacted granular base.

Does anyone have a formula for the maximum -ve moment at the top of the slab, and a maximum +ve moment at the bottom of the slab?

Thanks, Dik

RE: Slab on Grade Point Load

You could also use this to work your way back to moments: Link

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

RE: Slab on Grade Point Load

(OP)
Thanks, gentlemen...

Dik

RE: Slab on Grade Point Load

dik, attached is some info from Ringo and Anderson book's for design of slab on grades. Although, they mentioned that the moments at the bottom of the slab due to concentrate loads are important for the design, the don't have equations to calculate it. However, they have several methods for calculating slab thicknesses for column and wall loads.

RE: Slab on Grade Point Load

(OP)
Thanks Okiryu... not quite what I need, but an excellent reference.

Dik

RE: Slab on Grade Point Load

I realise you are seeking a FORMULA, but I doubt you will find an exact one anywhere.  On my website (rmniall.com) you will find a downloadable spreadsheet that solves this problem numerically.  It accommodates a Winkler subgrade or a continuous elastic subgrade.  However it assumes fully elastic behaviour so it does not allow for slab cracking and it treats subgrade tension the same as subgrade compression.

RE: Slab on Grade Point Load

dik...use elastic layer analysis. This will give you tension in the bottom of the slab, which I assume is your goal.

You can do a manual calculation as outlined in Yoder and Witczak, Principles of Pavement Design

RE: Slab on Grade Point Load

(OP)
Thanks gentlemen... the elastic layer approach is good. I was looking foe something qualitatively to add to a paper on SOG design and construction.

Dik

RE: Slab on Grade Point Load

I believe that the British Standard TR-34 gets into moments at the top and bottom of the slab.
It may be worth looking into

RE: Slab on Grade Point Load

Treat the slab as two perpendicular infinite long beams, and each beam takes 50% of the load. Based on the infinite long beam on elastic foundation theory, you can derive the movement, shear and deflection.

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