The current study presents advanced finite element (FE) models that combine the stress weighted damage model and the crack propagation using explicit dynamic approach of commercial FE software ABAQUS. The applicability of the subroutine for ductile fracture prediction and crack propagation modeling of structural steel is confirmed by comparing the results of fracture tests performed on circumferential notch specimens. FE analysis is performed on 17 circular hollow section (CHS) XK-joint models with various sized partial penetration welds to simulate the fracture process of the joint models, and the obtained results are used to analyze the fracture ultimate bearing capacity of the joint weld. The results indicate that the crack first appears on the inner side of the weld at the crown point of the intersecting line of the tensile web member. The findings also demonstrate that the joint weld does not lose the bearing capacity completely after the initial cracking. Instead, the joint weld's bearing capacity increased with the displacement at the early stages of fracture propagation to reach the maximum value prior to gradual decrease in bearing capacity. A design formula of weld bearing capacity suitable for partial penetration weld has been proposed herein to incorporate the effects of uneven distribution of joint weld stress in the considered XK-joints.

Bearing capacity; fracture; partial penetration weld; XK-joints