Victor Azzi wrote an article in Structures in April 2008 on point loads on a slab-on-grade. He derived his recommendations from Westergaard.
http://www.structuremag.org/article.aspx?articleID=613
The WRI also published the following article that may help.
http://www.wirereinforcementinstitute.org/pages/pubs/pdf/TF%20705-R-03.pdf
Regards, Harold Sprague
> Date: Fri, 1 May 2009 09:06:04 -0500
> From: admin@structuralae.com
> To: seaint@seaint.org
> Subject: Westergaard Formula for Point Loads on One-Way Slab
>
> Does anyone happen to have a pdf of an explanation of the Westergaard
> formula for the effective width of point loads on one-way slabs? I am
> looking for a credible resource for finding the effective width of a
> one-way slab for point loads. I read in the Eng-Tips Forum that the
> AASHTO equations are adapted from the Westergaard formula for
> application to truck loading. If I am applying the code prescribed
> point loads to a slab on a 4.5 in x 4.5 in square area I think the
> AASHTO equations are too liberal. The contact area for a truck tire
> is much larger than the 4.5x4.5 contact area.
>
> Thanks,
> Jeremy
>
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