The tensile stress beneath a load at the free edge of a slab is calculated from Kelley's modification of Westergaard's equation. The stresses computed from this equation were found to correlate well with the experimental stresses of Childs and Kapernick for free edge loading. This is the same equation as that evolved by Teller and Sutherland from their experiments on curled slabs.
The tensile stress computed from Teller and Sutherland's empirical equation for corner loading agreed with the experimental stresses obtained by Childs and Kapernick, but underestimated the stress for smaller areas of loading. Pickett's equation gives results which agreed better with the experimental stress for smaller areas of loading and also agreed equally well for the larger areas of loading of upward-curled slabs.
The tensile stress beneath an internal load is determined from Westergaard's original equation. This internal case is more important for rack loads than for wheel loads, because with racks there are several interacting loads in close proximity on the slab.
In calculating the edge and corner stresses, it is assumed that there is no load transfer between slabs. If load transfer is present, the calculated corner and edge stresses are multiplied by 0-7 and 0-85 respectively.