An approach to unified fatigue life assessment of high-strength steel bolted connections

This study proposes a unified approach to evaluate the fatigue life of bolted connections made of high-strength steels (Q460D and Q690D). The method considers both crack initiation and stable propagation phases within a single predictive framework. This includes an ellipsoidal fracture criterion to capture crack-tip behavior and instability, and its accuracy is further supported and explained via theoretical calculations and numerical simulations of fatigue crack propagation. The results demonstrate that, by including the influence of high-strength steel mechanical properties, the calibrated unified fatigue model shows significantly reduced prediction errors compared to conventional design provisions. The findings highlight the necessity of considering material-specific effects on bolted connections and demonstrate the effectiveness of the proposed unified approach in improving fatigue life predictions.