Stress concentrations and fatigue behavior of bird-beak SHS overlap K-joints subjected to brace in-plane force

Abstract

This paper focuses on the stress concentration factors (SCFs) and fatigue behavior of bird-beak square hollow section overlap K-joints under brace in-plane force. Four bird-beak overlap K-joint specimens were statically tested to determine the SCFs and to predict the critical cracking locations. Subsequently, high-cycle fatigue tests were performed to investigate the fatigue behavior including crack initiation and propagation, fatigue life and rigidity degradation. The results demonstrate that the crack always initiated at the locations with the greatest SCFs, specifically, at the overlap region and at the brace crown area for square and diamond bird-beak joints, respectively. The experimental fatigue lives were compared with the predictions by the International Institute of Welding (IIW) Srhs-N design curves. The comparison shows that the IIW design curve for conventional joints can conservatively estimate the fatigue life of bird-beak overlap K-joints.