Paper presented at the 32nd Annual Southern African Transport Conference 8-11 July 2013 "Transport and Sustainable Infrastructure", CSIR International Convention Centre, Pretoria, South Africa.
Growing traffic volumes, increasing construction and maintenance costs continually drive
for more innovative approaches and methodologies towards sustainable road infrastructure.
At the current price levels of around R6000 per metric tonne, bitumen, as a “raw” product,
is by far the most costly element in flexible pavements, for example compared to Crushed
stone, which is at approximately R170 per metric tonne. Since the asphalt layer or relatively
thin bituminous seal acts as the stress barrier between rolling tyres and the road structure it
needs to be durable so as to withstand current traffic loading and hence contact stresses,
given the environmental forces also acting on it. For road infrastructure to perform as
expected, it is important to optimize road pavement design, especially close to the surface
of the pavement requiring accurate modelling of tyre-road contact stresses.
The aim of this paper is to demonstrate modern ways to idealise tyre-road interaction based
on Stress-In-Motion (SIM) results, in particular the way in which numerical analyses are used
(and developed) to address non-uniformly distributed tyre contact stresses on the surface
of the pavements. A tyre model is demonstrated whereby the SIM measured contact stress
distribution is idealised with a multitude of circular and rectangular shapes, mimicking the
non-uniform characteristics of the contact stresses inside the tyre contact patch. An
example, in terms of pavement layer life and strain energy of distortion, is given highlighting
the effects of different tyre-road models on a typical flexible road structure, compared to the
traditional circular shape model of a single uniformly distributed contact stress (1D).
