Steel-concrete composite bridges are widely used in the engineering field due to their high strength and durability. However, during the long-term service life, such these structures are inevitably affected by vehicle loads and ambient temperature changes, which may cause fatigue damage. To alleviate this issue, the design and application of gusset plates are particularly important. Through the reasonable layout of the gusset plates, it is possible to effectively disperse stress and prevent stress concentration, thereby reducing the risk of structural damage caused by high local stress and improving the stability and safety of the structure. Welded gusset plates for diagonal braces are crucial components of steel-concrete composite girder bridges. In order to investigate the fatigue crack propagation behavior of welded gusset plates for diagonal braces of steel-concrete composite girder bridges, digital fatigue tests are carried out, taking one sea-crossing steel-concrete composite bridge as the case. The sequential coupling method is used to simulate the whole welding process of the welds of the diagonal braces gusset plates, and fracture mechanics theory and extended finite element method are applied to simulate the fatigue crack propagation. Results show that the crack propagation rate increases by 2-4 times when welding residual stresses are considered compared with no consideration, therefore the effect of welding residual stresses cannot be ignored. Typical fatigue cracks at the welded gusset plates of diagonal braces are Mode I-II-III composite cracks dominated by Mode I. The effects of Mode II and III cracks are non-negligible in fatigue assessment of welded gusset plates for diagonal braces.
ACKNOWLEDGEMENT
The authors gratefully acknowledge the financial support provided by National Natural Science Foundation of China (52308160)， Fundamental Research Funds for the Central Universities (HEU 3072024JJ2703)， Global High-level Partnership Building Project (HEU GK0000020127), and Guangdong Zhuhai LNG Expansion Program Phase II EPC Project Excellence Initiative Program (China National Offshore Oil Corporation) (Grant No. Z2023LGENT1210).