A three dimensional discrete-element (DE) method was developed to simulate the four-point bending fatigue test of asphalt mixture. Firstly, after generating the irregular polyhedron aggregates, a three-dimensional (3D) DE model was constructed based on the typical gradation of AC-16 mixture. Then the contact parameters were chosen from the microscopic model in PFC3D and macroscopic mechanical parameters were obtained from uniaxial compression test. Therefore the conversion relationship between microscopic and macroscopic parameters could be determined. A virtual fatigue test was performed using an optimal algorithm based on basic DEM theory and time-temperature superposition (TTS) principle. To calculate the fatigue life, we considered the emergence of cracks inside small beams as fatigue failure criterion. Test results obtained from 3D virtual fatigue test showed agreement with laboratory four-point bending beam fatigue test, showing that this approach could serve as an alternative method to investigate the fatigue behavior of asphalt mixture and also laid good foundation for further studies about the effects of microscopic structures on the fatigue behavior of asphalt mixtures.
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