Abstract

The gross vehicle weight (GVW) and dimensions of articulated freight vehicles have been considerably relaxed during the past few decades, which have contributed to many concerns related to highway safety and preservation of the roadways. The directional dynamics of articulated heavy vehicles is investigated to study the influence of road roughness on the directional performance measures and the road damage potentials of the vehicle undergoing a directional maneuver. The directional performance characteristics and the road damage potentials are investigated for low speed cornering and high-speed directional maneuvers. A number of measured road profiles are analyzed to identify three groups of roads, namely: smooth, medium and rough roads based on their roughness index (RI) values. A detailed analysis of the road roughness data is carried out to derive correlation between the right and left wheel excitations. A range of performance measures are formulated to study the influence of road roughness on the directional dynamics and the influence of steering maneuver on the pavement damage. The equations of motion of the vehicle are solved for typical low-speed cornering, and high-speed lane-change and evasive maneuvers. The results of the study show that the road roughness affects some of the directional performance measures of the vehicle in a significant manner, specifically the lateral load transfer ratio related to dynamic rollover potential of the vehicle. The study also revealed that the multiple excitations arising from the tire-road interactions and the directional maneuvers, significantly contribute to the dynamic wheel loads transmitted to the pavement. The contributions of excitations arising from directional maneuvers to the dynamic wheel load are presented in terms of different measures, which have been related to the road damaging potentials of heavy vehicles. These measures include dynamic load coefficient, the dynamic road stress factor and the peak tire force.