Fatigue tests and fatigue-life prediction models for hybrid welded-bolted demountable shear connectors

Four push out tests were conducted to assess the structural performance of a welded demountable shear connector (WDSC) under high-cycle fatigue loading. The primary failure mode observed was stud fracture at the base. The presence of grout inside the tube significantly increased the WDSC's fatigue life by 5.4 times. The study also analysed stiffness degradation and relative slip evolution during fatigue cycles. Two finite element-based approaches were employed for fatigue life prediction: the critical plane method for fatigue crack initiation life and fracture mechanics for crack propagation life. Based on the experimental and numerical results, fatigue life prediction formulas (Wöhler curves) are proposed for WDSCs with and without grout to aid in predicting fatigue failure in fatigue-sensitive structural designs.