Super-single tire loadings and their impacts on pavement design

Abstract

Pavement design and analysis are generally performed based on the load equivalent factor (LEF) obtained from conventional dual tires and assume that the contact stress is equal to the tire inflation pressure. However, heavier tire loadings, such as super-single tires, produce much higher contact stresses than the inflation pressure. This results in larger deformations of subgrades, requiring advanced modeling of subgrades, such as elastic–plastic analysis. Super-single tires also have a different contact area shape from that of conventional tires. To assess the increased contact stresses by super-single tires, realistic contact stress distribution and contact area ratio for super-single tires should be used in the analysis. Three-dimensional finite element analyses of typical flexible pavements were done to evaluate the effects of the increased contact stresses of tire loadings on the subgrades, including load equivalency factors, overlay effect, and subgrade improvement as the behavior of subgrades becomes more important due to the increased contact stresses. Analysis results indicate that the increased contact stresses should be taken into account in the pavement structure design, as well as design of overlay or subgrade improvement. Based on the numerical results, simple design examples are suggested.