Block shear failure of stainless steel staggered bolted connections

This paper presents a comprehensive experimental and numerical study focusing on the block shear failure behaviour of stainless steel staggered bolted connections. The experimental results showed that although austenitic stainless steels possessed slightly higher ultimate tensile strengths, their ultimate block shear resistances were lower than those of duplex stainless steels, primarily due to earlier shear cracking near bolt holes. Two distinct failure modes were identified for austenitic connections, whereas duplex connections only exhibited a single failure mode. The developed finite element (FE) models, validated against the test results and considering material anisotropy and fracture behaviour, accurately captured the observed behaviours and enabled an extensive parametric study. The parametric study results indicated that gauge distance, pitch distance, end distance, bolt spacing, and the number of bolt rows significantly improved the block shear resistance of stainless steel staggered bolted connections, while plate thickness and bolt hole diameter had only marginal influences. A comparison between the existing design predictions and the experimentally validated FE results showed that the current specifications (AISC 360, AS 4100, EN 1993, CSA S-16) cannot adequately account for the pronounced strain-hardening behaviour and failure characteristics of stainless steel staggered bolted connections. To improve the predictive accuracy for stainless steel staggered bolted connections, a modified design method was developed by incorporating the tensile-to-yield strength ratio of stainless steels. Additionally, advanced machine learning approaches, grounded in a rational understanding of the structural mechanisms, were employed to further enhance the accuracy of prediction.