Dynamic fatigue life prediction of ballastless track under high-frequency train vibrational loads

The fatigue life of ballastless track is a critical measure of its long-term structural durability under repeated train loading. However, existing quasi-static fatigue evaluation methods fail to adequately capture the influence of complex, multi-frequency vibrations induced by high-speed train operations, especially the random vibration components generated by track irregularities, on fatigue damage. This paper proposes a dynamic fatigue damage evaluation method that integrates the characteristic vibration loading modes of high-speed railway tracks with the nonlinear evolution of concrete fatigue damage. Specifically, the proposed method modifies both the fatigue damage accumulation criterion and the traditional fatigue life equation by incorporating the frequency-dependent behavior of concrete, with model parameters calibrated through acoustic-emission-based fatigue tests. To demonstrate the applicability of the proposed approach, a case study on the CRTS II slab track is conducted, in which the dynamic stress responses under train moving excitation and track irregularity excitation are analyzed through equivalent treatment of dynamic stress amplitudes and frequencies using the power spectral density method. The results reveal that train-induced moving excitation has a negligible influence on fatigue damage, as its acting frequency nearly coincides with the wheel-passing frequency. In contrast, track irregularity excitation significantly accelerates the damage evolution, reducing the fatigue life of the track slab from 174 years to 119 years at the critical fatigue damage state when the train speed is 350 km/h, corresponding to an equivalent fatigue load approximately 3.6 times the static wheel load. • A dynamic fatigue framework is developed for ballastless tracks. • A spectral-density method yields representative amplitude and frequency features. • Frequency-dependent and nonlinear damage are modified to capture concrete fatigue. • Track irregularity reduces fatigue life by 40% and raises load to 3.6 times.