Evaluation of equivalent axle load factors for multi axles based on fatigue tests using actual strain waveforms

Equivalent axle load factor (EALF) is used to characterize the fatigue damage effect of multi-axle loads on asphalt pavement. EALF is calculated as the ratio of the pavement's fatigue resistance under a single axle load to that under a multi-axle load. Existing studies use the same fatigue life function to predict the fatigue life of asphalt mixture under both single- and multi-axle loads, primarily focusing on the differences in pavement strains under these two configurations. However, strain waveforms in asphalt pavement caused by multi-axle loads differ from those under single-axle loads, altering the mixture's fatigue behavior. To address this issue, this research tests the fatigue responses of asphalt mixtures under actual loading waveforms from single-axle, tandem-axle, and tridem-axle loads. Based on the test results, fatigue life functions are developed for each axle configuration and used to establish an updated EALF model. Since the applied fatigue life functions are based on test results from more realistic strain waveforms, the calculated EALFs provide more reliable predictions of the damaging effect of multi-axle loads on asphalt mixtures.