Fatigue life analysis of airport runways with semi-rigid base asphalt surfaces under the coupling effect of temperature and traffic load

Cracking is a prevalent issue in asphalt pavements, particularly in airport runways with semi-rigid bases, where top-down cracks are exacerbated by the combined effects of traffic loads and environmental temperature fluctuations. This study employs fracture mechanics and finite element numerical simulation to investigate the fatigue life of asphalt pavements under three loading conditions: traffic loading alone (Condition 1), coupled traffic-temperature loading with constant modulus (Condition 2), and coupled loading incorporating temperature-dependent dynamic modulus (Condition 3). The results reveal that the stress intensity factor (SIF) at crack tips exhibits an inverse correlation with external temperature variations. Under Condition 3, the SIF peak envelope decreases by 12.0% during daytime heating and increases by 8.0% during nighttime cooling, resulting in a 20.0% total diurnal variation. The SIF_peak maximum increases from 0.0188 MPa m 1/2 in Condition 2 to 0.0367 MPa m 1/2 (Condition 3), representing a 95.2% amplification due to temperature-dependent modulus. Correspondingly, the fatigue life decreases from 7.72 × 10 5 cycles (Condition 1) to 7.54 × 10 5 cycles (Condition 2) and further to 6.99 × 10 5 cycles (Condition 3). A sensitivity analysis based on the minimum fatigue life reveals that the Paris exponent m is the most influential parameter, followed by the Paris coefficient C, the final crack depth, and the initial crack depth. These findings underscores the critical importance of considering both thermal gradients and temperature-dependent material properties in pavement design. Neglecting these factors can overestimate fatigue life by 9.5%, leading to premature failure. The results provide a quantitative framework for optimizing pavement durability under combined thermal and mechanical loads, offering valuable insights for the maintenance and design of airport runways.