Experimental and numerical investigation of fatigue-damage evolution in SMA and AC mixtures based on S-VECD and phenomenological modeling

In this work, dynamic-modulus and uniaxial, tensile fatigue tests are conducted on asphalt concrete-13 (AC-13) and stone mastic asphalt-13 (SMA-13) asphalt mixtures commonly used in bridge-deck pavements. The fatigue-damage evolution is analyzed using the simplified viscoelastic continuum damage (S-VECD) theory and a phenomenological approach. The Williams–Landel–Ferry principle is applied to construct the master curves of dynamic modulus and phase angle, and the C – S damage characteristic curve ( C: pseudo-secant modulus and S: internal state variable), failure-criterion parameter D R , and apparent damage capacity ( S app ) are determined. The results reveal that SMA-13 exhibits a high dynamic modulus and low phase angle across the entire temperature–frequency domain. Its C – S curve consistently lies above that of AC-13, indicating stronger damage resistance and better fatigue performance. Based on these findings, a strain-driven phenomenological fatigue-damage model is developed and implemented in a finite-element framework, to couple the pavement-stiffness degradation with the structural response. Numerical results indicate that the principal tensile strain at the top of the bridge-deck pavement layer is significantly larger than that at the bottom, with damage showing pronounced localization. In addition, higher temperatures markedly accelerate damage evolution. Further analyses under different equivalent loading cycles reveal the influence of pavement-stiffness degradation on the stress amplitude of critical weld details in the underlying steel bridge-deck plate.