The application of UHPC in bridge engineering is becoming increasingly common. In order to further study the fatigue performance of RD welded joints in steel UHPC composite bridge decks,fatigue tests and nu-merical simulations were conducted on RD welded joints of steel bridge decks under simulated wheel loads. The fatigue cracking behavior and stress distribution of specimens under central loading conditions were analyzed, and the fatigue life of RD welded joints was predicted using structure stress method. A 3D solid finite element model of RD welded joints with UHPC overlay was established based on ABAQUS software. Static loads were applied to the model,and node forces and moments at the crack initiation section were extracted to calculate the equivalent structure stress. The fatigue performance of RD welded joints was evaluated using the master S- N curve in the structural stress method,and compared with the predicted results of the hot spot stress method and critical distance theory. The research results indicate that under the central loading condition,the weld seam connecting the cover plate and the U- rib is subjected to tensile stress,and the tensile stress gradually increases and tends to stabilize in the middle of the weld seam. Fatigue cracks first initiate at the vulnerable part and propagate in stages along the thickness direction of the plate until fracture; After being reinforced with UHPC,the end effect of the weld seam in the RD welded joint is significantly reduced,and the structural stress value in the middle of the weld seam is greatly reduced,with a maximum reduction of 87.2%. At the same time,the UHPC layer and the cover plate form a whole to jointly bear the load,making the structure stress distribution tend to be flat,significantly improving the fatigue stress state of the steel bridge deck; Compared with the hot spot stress method and critical distance theory,the prediction results given by the structure stress method are more conservative and closer to the experimental values,with a prediction error of only 8%. For steel-UHPC composite welded joints,the predicted values given by the structure stress method reach infinite fatigue life. Overall,the structure stress method can effectively evaluate the fatigue performance of steel bridge decks,accurately predict the fatigue life of welded components at a lower cost,and assist in formulating maintenance strategies. It has broad practical prospects in the field of steel structure bridges.