Plastic collapse load prediction of cracked circular hollow section gap K-joints under in-plane bending

• Create finite element mesh models of cracked CHS gap K-joints containing a surface crack at the weld toe of the chord.
• Carry out a parametric study to investigate the in-plane plastic collapse moment of cracked CHS gap K-joints.
• Propose an equation to predict the in-plane plastic collapse moments of cracked CHS gap K-joints.

This paper reports the in-plane plastic collapse moment of cracked circular hollow section (CHS) gap K-joints containing a semi-elliptical surface crack located at the crown position. An in-house 3D finite element (FE) mesh generator is developed to create all the mesh models automatically. Firstly, in-plane plastic collapse moment applied to the uncracked CHS gap K-joints are investigated. Both Lu’s deformation limit and twice elastic compliance are used to determine the in-plane plastic collapse moment. Consequently, an extensive parametric study is carried out to investigate the in-plane plastic collapse moment of the cracked joints. It is found that the crack has a significant influence on the in-plane plastic collapse moment. The decrease of the in-plane plastic collapse moment is up to 30.4% when the crack area Anc reaches up to 25%. The strength reduction factors of all the analyzed cracked CHS gap K-joints are calculated. Finally, a lower bound reduction factor FAR equation is proposed based on the FE results.