Effects of accelerating and decelerating tramway loads on bituminous pavement

The concept of a tramway on tires will allow authorities to provide a modern and efficient transportation system that is well suited to medium-sized towns and suburbs of larger urban areas. Precision in terms of levelling and evenness plays a very important role in the proper functioning of vehicles and in user comfort. These requirements can be satisfied through adequate mechanical resistance against rutting, cracking, and fatigue, and through adequate behaviour of the materials within the structure. These facts motivated the authors to conduct a material and structure study pertaining to the effects of speed and the horizontal forces acting on viscoelastic surface layers that could possibly affect the pavement design. In order to study the various effects of moving loads (braking, accelerating and cornering) on bituminous pavement, numerical calculations were carried out with the help of the ViscoRoute Software version 1.0. The study revealed that the surface layer is subjected to the highest degree of longitudinal shear stress at the driving axles when the tramway is braking or accelerating. These effects decrease with the depth of the pavement materials. The first and second stress invariants (mean stress and deviator stress) are used to show the stress path under the accelerating and braking tramway. When the temperature increases, the same description can be applied to the various load conditions. The stress invariants provide valuable insight into the three-dimensional response of the material, and may be useful in terms of introducing a yield surface for modelling permanent deformations and a more realistic experimental protocol for evaluating the behaviour of bituminous surfacing materials in the laboratory.