Assessment of fatigue crack propagation and lifetime of double-sided U-rib welds considering welding residual stress relaxation

Welding residual stresses (WRS) impacts the fatigue life of welded steel bridges , but its relaxation is commonly overlooked in assessments. This study introduced a numerical simulation model to assess the effect of WRS relaxation on the fatigue crack propagation and lifetime of double-sided U-rib welds in orthotropic steel decks (OSD). Firstly, an initial distribution of WRS was determined using a thermal-mechanical finite element (FE) method. Then, a cracked FE model was employed to evaluate the crack propagation and lifetime under WRS and cyclic loading. Finally, the influence of initial crack parameters on the fatigue lifetime was studied. The results indicated that WRS notably alter the stress intensity factor values along the crack front, and this relaxation of WRS occurs concurrently with the crack propagation progression. The presence of WRS reduces the fatigue propagation lifetime, and fatigue life predictions that consider WRS but overlook its relaxation are overly conservative. The dimensions of the initial crack, including depth and aspect ratio, significantly influence the fatigue propagation lifetime of double-sided U-rib welds. This research underscores the critical role of WRS relaxation in the crack propagation of welded joints and offers an innovative framework for assessing the fatigue propagation lifetime of steel bridges. • Presented a method for assessing the fatigue crack propagation and lifetime of OSD welded joints considering WRS relaxation. • Fatigue crack propagation behavior of rib-to-deck double-sided welded joints considering WRS relaxation was simulated. • The influence of initial fatigue crack parameters on the fatigue propagation lifetime was discussed.