Analysis of industrial floor slabs-on-ground for design purposes

Slab-on-ground foundations refer to ground supported floor slabs used to transfer loads safely to the subgrade without undergoing distress themselves. These foundations have been used in residential, light commercial and industrial buildings for many years. Since the loading conditions and magnitudes in industrial buildings are wery different from those in residential and light commercial buildings, their design must be approached differently. Various design procedures have evolved for the thickness design of industrial floor slabs, but most of them have been developed for a specific use or have certain limitations. Therefore, there is still a need for a rational design procedure which will eliminate some of these limitations.

In order to develop a rational design or analysis procedure, a parametric study involving slab length, slab width, slab thickness, modulus of elasticity of soil, aisle width between stacks, stack loading, and forklift loading was conducted to study their influence on deflections, bending stresses, bending moments, and shear forces occurring in the slab. The study was conducted by considering the influence of stack and forklift loadings, both separately and together. The values used in the study were over a realistic range. Regression analysis was performed on the results of 618 individual problems and equations for the thickness design of industrial floor slabs were developed. Correlation coefficients for these equations ranged from 0.78 to 0.99.

As the modulus of elasticity of the soil is an important parameter in the design of industrial floor slabs, a survey of eight practicing engineers and commercial testing laboratories was conducted to determine the most practical and economical means of evaluating the modulus of elasticity of soil.

Equations rather than nomographs have been developed for maximum bending stresses, maximum shear forces and maximum differential deflection for each loading condition. These equations permit solving for the required slab thickness to resist the imposed loads.