High-Cycle Fatigue Assessment Method for Composite Bridges Based on Predamage Mechanics Model

Long-span bridges face the significant challenge of deteriorating life cycles under fatigue loads. A new macroscopic damage mechanics model for rod hinge elements has been proposed to quantify the predamage of bridge beams subjected to high-cycle fatigue. This model introduces predamage variables to evaluate the damage evolution process prior to fatigue crack initiation, enabling the prediction of moderate deterioration in bridges that cannot be monitored during their service life. By comparing the fatigue test results and predamage simulation results of simply supported composite beams and continuous composite beams, it was found that the error between the model predictions and the test results is relatively small. This result confirms the reliability of the model. The predamage model has been implemented as a self-programming subroutine for numerical analysis. Taking the Daxi River Bridge as the engineering background, this predamage model was applied to practical engineering. Combined with typical traffic loads, a predamage assessment was conducted on its dangerous points. The dangerous beam segments of the bridge were taken and the damage values were calculated using a predamage subroutine model. The results obtained had a small error compared to the damage values of the corresponding beam segments in the full bridge simulation. The proposed high-cycle fatigue predamage subroutine model offers a valuable reference for predicting fatigue damage in bridges.