SIF-based Fracture Analysis of Welded Joints in Vierendeel Trusses via FE Modelling.

Steel hollow structure section (HSS) chord-to-branch joints in Vierendeel trusses are concerned for their proneness to fracture due to imperfection in fabrication. In this paper, the stress intensity factors (SIFs) for HSS chord-to-branch joints are examined based on fracture mechanics and finite element modelling. Through a well-prepared sub-modelling strategy, the influences of geometric parameters related to the crack propagation behaviour are analysed and discussed. The crack front of the HSS chord-to-branch joint without the axial stress of the branch is shown to have notably high SIFs at the deepest point and the surface point. Alternatively, the concentration of highest SIFs at the deepest point of the elliptical arc of the crack becomes significant with the increase of the axial stress of the branch. The increase of the chord wall thickness is shown to be beneficial in the reduction of the SIFs for HSS chord-to-branch joints, especially for lower chord width ratio normalized by thickness. Conversely, the influence of the crack shape indicated by larger aspect ratio on the reduced SIFs becomes obvious and consistent for greater chord width ratio normalized by thickness. The SIFs for HSS chord-to-branch joints are decreased with the increase of the normalized crack depth with respect to the chord wall thickness, particular for shallow surface cracks. Such a trend becomes obvious for the joints with lower fillet weld leg length of equal leg fillet welds with respect to the chord wall thickness or with lower weld leg length along the HSS branch with respect to that along the chord. [ABSTRACT FROM AUTHOR]