A continuum mechanical approach to model asphalt

Abstract

The goal of this paper is to contribute to tire–pavement-interaction analyses from a structural mechanics point of view. The proposed asphalt material model is used to analyse the strain–stress dependencies of an asphalt pavement which is cyclically loaded by a truck tire. For the analysis of tire and pavement as well as its interaction, a finite element approach is utilised. The development of the material model is based on triaxial material tests of cylindrical specimens. The asphalt material is characterised by elastic, viscous (rate-dependent) and plastic behaviour. In order to enable the use of the model also for large deformations within the pavement, it is developed for finite strains. The proposed approach consists of five rheological constitutive branches in parallel. A nonlinear elastic material model is used, which represents the elastic behaviour. The plastic effects are considered by an endochronic frictional element. One Maxwell element and two fractional Maxwell elements represent the viscoelastic behaviour of the model. The consideration of fractional elements is commonly used for the characterisation of cyclicly loaded materials like asphalt. Furthermore, it enables the representation of viscoelastic properties with few material parameters. For the fractional element, a material parameter determines the transition of the rheological element's features between spring () and dashpot (). The proposed model is finally considered within a simulation of a pavement at transient cyclic tire loading. Hence, the increase of the pavement deformation after each load cycle is obtained. Taking this result into account, the long-term behaviour of asphalt pavement is extrapolated and the development of rutting is computed in dependency on the number of load cycles.

Keywords::

• tire–pavement interaction
• predictive structural analysis
• finite element simulation
• finite strains
• visco-plastic material formulation
• fractional time derivative

Acknowledgements

The helpful cooperation of the Institute of Urban and Road Engineering (IURE) at Technische Universität Dresden and their work within our joint research project on tire–pavement interaction phenomena is gratefully appreciated. The collaboration of Prof. Wellner, as one of the project leaders and Mr Zeißler, as scientific project staff, is particularly acknowledged.

Additional information

Funding

The financial support of this research project by the Deutsche Forschungsgemeinschaft (DFG) under grant KA 1163/6 is gratefully acknowledged.