MECHANISTIC DETERMINATION OF EQUIVALENT DAMAGE FACTORS FOR MULTIPLE LOAD AND AXLE CONFIGURATIONS

The increase of the maximum axle load limit in South Africa sparked renewed interest into methods of quantifying traffic load associated damage on pavements. Extensive research with the Heavy Vehicle Simulator (HVS) over the past 20 years has led to improved fundamental understanding of pavement performance and has permitted the development of Equivalent Damage Factors (EDFs) for single-axle loads. A major limitation of this approach is that it does not directly facilitate the calculation of EDFs for multiple axle configurations, i.e., tandem or tridem axles. This paper describes a method for extending the existing HVS-based method to the determination of EDFs for multiple axle configurations. This, in principle, facilitates the development of guidelines on permissible axle loads and tyre inflation pressures for different axle configurations. The method assesses the effects of: wheel load, contact stress, single and dual wheels, and single, tandem and tridem axle configurations. The method, therefore, enables determination of EDFs for the accurate estimation of equivalent traffic loading for design purposes and performance analysis enhancing life predictions and management decisions. Initial determinations indicated the advantage to road friendliness of grouping axles together into tandem or tridem configurations. Additionally, the use of dual-wheel instead of single-wheel axles could result in the axle load being increased by up to 30% without any increase in pavement damage.