Abstract
With the adoption of the new mechanistic-empirical pavement design method and the employment of axle load spectra, the question of evaluating the pavement damage resulting from different axle and truck configurations has become more relevant. In particular, the state of Michigan is unique in permitting several heavy truck axle configurations that are composed of up to 11 axles, sometimes with as many as 8 axles within one axle group. Thus, there is a need to identify the relative pavement fatigue damage resulting from these multiple axle trucks.
In this paper, the fatigue life of a typical plain concrete mixture under different truck axle configurations was determined directly from a cyclic four point beam test by using load pulses that are equivalent to the passage of an entire axle group. The S-N curves were determined for each axle configuration from the cyclic beam tests. The laboratory investigation indicates that the fatigue damage due to different axle configurations increases with increasing number of axles within an axle group for a given stress ratio. However, the results also indicate that for the multiple axles, the damage per axle is less than the single axle for the same stress ratio. Additionally, the results show that the axle factors for multiple axles tend to increase as the stress ratio decreases.