The critical bending moment due to uniform loading is determined by a discrete-element slab analysis, as used by Panak and Rauhut. This technique is well documented and gives results for this type of problem as accurate as those obtained by the more expensive and time-consuming finite element techniques.
The bending moment in the slab is determined for a given aisle width and radius of relative stiffness, which is a measure of the ratio of the stiffness of the slab to the stiffness of the subgrade. The critical bending moment is usually the negative moment in mid-aisle, but in the case of large aisle widths may be the positive moment. This Figure assumes that the aisle is loaded on both sides. If the aisle is loaded on only one side, the bending moment from Figure should be halved. The design moment is the bending moment from Figure multiplied by the loading in kN/m2 and by the load safety factor. The required tensile strength of the concrete is the design moment divided by the section modulus.
For uniform loading, the slab and sub-base have virtually no load-spreading ability. To avoid shear failure, therefore, the loading on the slab may have to be limited in the case of organic soils and clays to the bearing capacity of these layers. Loads may also have to be limited to avoid unacceptable consolidation.