Study on fatigue performance of steel bridge welded joints considering initial defects

Orthotropic steel bridge decks (OSBDs) are extensively utilized in both medium-span and long-span bridges due to their lightweight and high strength properties. The current predominant method for connecting steel bridge decks is welding. However, the discontinuous geometric shape and inevitable welding defects at the welded joints are prone to stress concentration. This leads to fatigue cracks in steel bridge decks predominantly occuring at locations where defects are present within the welded joints. This study analyzes the fatigue performance and crack propagation of the rib-to-deck connection details considering the influence of initial defects. The experimental results of the T-joint revealed that the undercuts exerted a substantial influence on the fatigue performance, whereas partial penetration had a relatively small impact. The S–N curve of the specimen with undercuts can be derived by reducing 4 standard deviations from the S–N curve without initial defect. Alternatively, the fatigue strength of the specimen without initial defects can be divided by a safety factor of 1.4. The Paris formula was employed to compute pertinent parameters for crack propagation, followed by the utilization of the finite element method to simulate the process of crack propagation within the rib-to-deck details. The feasibility of this approach was confirmed by the simulation results. Furthermore, this study discussed the impact of initial crack size parameters on crack propagation mode and fatigue performance, providing valuable insights into the mechanisms underlying the fatigue crack propagation within welded joints of steel bridges.