Wire Reinforcement Institute (WRI) Method presents design nomographs for slab thickness determination based on solutions using a discrete element computer model for the concrete slab as a continuum on a Winkler foundation. Only loadings on the interior of the slab are considered.

  Slab stresses are less for moving loads than for static loads.

  At free edges that lack adequate load transfer, concentrated loads will produce stresses that are somewhat greater than those for the interior, Because of this, if trucks will pass over an isolation joint (at a doorway for instance) the slab should be thicked by 25% gradually over a distance of 5 ft.

  Temperature and shrinkage reinforcement should be at or above middepth of the slab on grade, never below middepth.

  Evaporation of moisture from the top surface of a slab causes the upper half of the slab to shrink more than the lower half.

  Type I and III cements can cause higher concrete shrinkage than type II cement because of their higher water demands.

  Reference:
    ACI360R   Design of Slabs on Grade