Effects of tyre contact pressure distribution on the deformation rates of pavements

This paper present the preliminary findings of research aimed at determining the character of the contact pressure distribution of crane tyres and estimating their influence on the deformation of pavements. The impetus for the research was: (i) the requirement of the (Australian) regulation for a minimum tyre size of 20.5-inch (525mm) for all-terrain cranes with a maximum allowable axle load of 12 tonnes; and (ii) the Australian crane industry’s argument for the adoption of smaller tyres with reduced inflation pressures based on the expectation of increased contact area, hence reduced contact pressure. The paper describes the use of pressure-sensitive film to generate a digital field proportional to contact pressure. The results show that the contact pressure distributions measured were complex and not uniformly-distributed over a circular area as is assumed in conventional pavement analysis. The pressure distribution maps revealed large localised contact pressures (often greater that three times the mean net contact pressure) at the edge of individual tread blocks. The measured data were used to study the effects of realistic contact pressure distributions on the deformation rates of flexible pavements, using Finite Element Analysis based on a non-linear visco-plastic strain and temperature dependent constitutive model. Symposium held by the International Forum for Road Transport Technology between June 18-22, 2006,at Pennsylvania State University, State College, Pennsylvania