This report presents an overview on the most known equivalent layer theories, which are used in pavement design to combine overlaying layers with different thicknesses and moduli into one layer with an equivalent thickness Heq. Special attention is paid to the applicability in case of calculations using the Hogg and Westergaard models for concrete pavements. It is shown that in principle the equivalent layer thickness theories can not be used in the Westergaard model, because this model (Winkler foundation) is not comparable with the linear elastic isotropic half space or multilayer model (Burmister model), on which all the equivalent layer theories are based. Only in the case of the Supplementary Theory model of Westergaard, in which the reaction of the foundation is corrected to that of a linear elastic half space (Hogg-Jeuffroy model), a relationship can be established between the modulus of subgrade reaction k and the Youngs modulus E(sub 0) for both the deflection and the stress. Therefore the relationship given by Eisenmann, k = E(sub 0)/Heq, is not correct.
Samenvatting