Random vibration analysis of train-track-bridge systems considering random fatigue damage in cement asphalt mortar layers

The dynamic interactions in train-track-bridge (TTB) systems are crucial for high-speed railway (HSR) safety. The random fatigue damage (RFD) of cement asphalt (CA) mortar layers, a vital interlayer for force transmission, has not been fully explored in terms of its impact on the coupled vibration response systems. This study investigates the influence of RFD and track irregularities on the dynamic behavior of TTB systems through a probabilistic modeling approach. A three-dimensional spatial vibration model was developed, incorporating a multi-rigid body vehicle dynamics model, a finite element model of the CRTS II ballastless track and simply supported bridge, and a fatigue viscoelastic constitutive model for the CA mortar. Random stress levels and cyclic loading ratios were considered to simulate the random damage evolution in the CA mortar layer. The probability density evolution method (PDEM) was employed for dynamic analysis, and the model was validated against Monte Carlo simulations to ensure accuracy and computational efficiency. Key findings reveal that while variations in CA mortar stress levels minimally affect the vehicle and track responses, they significantly influence the bridge acceleration, with mean acceleration increasing by up to 17.3% near the end of the fatigue life. The mid-span deflection of the bridge showed negligible change, indicating the overall structural safety of the system despite interlayer deterioration. This study highlights the train-track system’s resilience to RFD in CA mortar while emphasizing bridge monitoring for long-term safety. The framework effectively analyzes random damage in TTB systems, offering key insights for HSR infrastructure maintenance and design optimization.