Stress and strain distributions in fillet welded joints

Structural integrity in steel structures relies heavily on welding, which fuses metallic parts using molten metal. Fillet welded joints, commonly used in buildings, bridges, railways, and marine structures, are subjected to static and dynamic loads, which can lead to potential failures. The fillet welded joint resistance calculation must account for the influence of various parameters, such as weld discontinuities, geometry, and joint configuration. Additionally, the accuracy of resistance calculated using the Finite Element Method (FEM) is influenced by numerical modelling parameters. In this study, stress and strain distributions in weld beads at the analytical design resistance level, the critical values, were investigated using numerical simulations with solid elements. Four common fillet welded joints were selected: lap joints with short and long longitudinal welds, lap joints with transverse fillet welds, fin plate joints, and unstiffened T-joints with transverse welds. The unstiffened T-joint was also studied experimentally using three specimens, where the surface strain distribution on the plate at the weld toe was measured using the Digital Image Correlation (DIC) method. A total of 48 distributions were analyzed. The minimum critical stress was determined to be 243.8 MPa, and the minimum critical plastic strain was 1.51 %. Both values were observed in the fin plate joint. For the lap joints, the critical values increased with increasing weld length.