Dynamic axle loads were measured with an instrumented vehicle, and pavement performance was modelled using a modified version of VESYS-III-A. The experiment involved five levels of pavement roughness, three levels of vehicle speed, and two suspension types -- air and rubber. A method was proposed for modelling the impact of the repetitive in-space dynamic loads experienced by AASHO road test sections. It consisted of dividing the load frequency distribution experienced by each section into segments and assigning segment combinations from the axles of a vehicle to pavement subsections. The method yielded a considerable improvement in performance prediction accuracy. Another part of the study examined the impact of suspension type on pavement performance by assuming that dynamic loads are random in space. The load frequency distributions obtained for the highest vehicle speed tested were used for this purpose. Comparisons were based on the area contained between the performance curve and a minimum psi value. For the roughest section, the rubber suspension caused 17 to 22 percent more damage than the static load, depending on the terminal psi value assumed. Similar values calculated for the air suspension ranged between 4 and 8 percent. Results were sensitive to the way the tire inflation pressure was handled in modelling dynamic load.
Abstract