In this study, fatigue tests and corresponding FE simulations were performed on six rib-to-deck welded specimens to examine the influence of the actual weld profile. Fatigue crack initiation and propagation behaviors, including single, dual, triple, and combined internal-external cracks, were analyzed, and crack growth curves under constant and variable amplitude loading were obtained. The weld profile was captured using the replica method and mathematically modeled to support accurate FE simulation. A simplified approach was adopted to simulate the actual weld that a single representative profile along the weld was considered. Comparative analyses between models with ideal and actual weld profiles show that the nominal stress-based fatigue assessment is insensitive to the weld geometry. However, the stress concentration at internal and external weld toe was affected by the variations between the ideal and actual weld profiles: the peak values of the stresses at internal and external weld toes have decreased by 10.28 % and 31.96 %, respectively. The hot-spot stresses (σ2-HSS and σ3-HSS) at the internal weld toe is insensitive to the variation of weld profile; however, the σ2-HSS and σ3-HSS decrease notably when considering the actual weld profile, with concentration factors reduced from 1.123 to 1.106 and from 1.134 to 1.105. It is recommended to model ideal weld profiles for conservative results, with correction factors (0.985 and 0.974) applied when higher accuracy is desired.