Experimental and numerical analysis of mechanical properties of steel beam-column joints with initial defects

The welding defects in the lower flange area of beam-column joints can easily cause brittle fracture, which can lead to structural failure. In this paper, an artificial defect was deliberately introduced into the single-beam-flange welds of beam-column assemblies. Five distinct loading protocols were then applied to the test specimens to investigate how the initial flaw and the loading regime jointly affect the mechanical response of the welded joints. Furthermore, the Extended Finite Element Method (XFEM) was employed to simulate the experimental process. A comparative analysis between experimental and XFEM results was conducted. The results indicate that the initial weld defect causes significant differences in the crack propagation rate and location, and decreases the bearing capacity and energy dissipation of the joints. The performance of the joint is independent of the loading span, but the sudden displacement loading can cause greater damage. The XFEM can accurately reflect the mechanical performance of the joints, particularly under cyclic loading conditions with initial defects.