Influence of Different Rheological Models on Predicted Pavement Responses in Flexible Pavements

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ABSTRACT Conventional response models are based on linear elastic theory and stationary loading. Such models are in principle considered inadequate for predicting actual pavement responses. Since bitumnous mixes exhibits viscoelastic properties and the wheel loads are moving, several rheological models have been proposed for describing mechanical properties of bituminous mixes. However, many of these models are capable of representing a material in terms of stiffness and phase angle only within a limited frequency range. As a moving wheel load generates a wide range of frequencies in the pavement structure, it is important to select a rheological model that is able to describe the material properties over the range of frequencies occurring in practice. In this paper the Burgers and Huet-Sayegh models were evaluated. The viscoelastic properties of a bituminous mix were characterised at different frequencies and temperatures. The capability of the two models in describing measured data was investigated and illustrated as Black and Cole-Cole diagrams. The model parameters determined were used to predict pavement response at different temperatures and velocities for two pavement structures. These calculations were based on VEROAD, a linear viscoelastic multilayer program. The results presented show that the Burgers model is suitable for describing viscoelastic properties within a limited range of temperatures and frequencies, whereas the Huet-Sayegh model is suitable for most conditions occurring in practice. The comparison between calculated pavement responses indicated, that there are differences between the models depending on the prevailing conditions. At temperatures, velocities and locations with frequency content within the range well described by the Burgers model, the differences in predicted response were small. However, for conditions outside this range, the differences may be considerable.