Net section failure of stainless steel staggered bolted connections

Abstract

In steel structures, staggered bolted connections are generally employed to achieve more compact bolt arrangement and higher material efficiency over conventional parallel bolted connections. To further enhance their corrosion resistance and long-term durability, stainless steels are increasingly favoured. However, the varying tensile-to-yield strength ratios of different stainless steels introduce challenges in accurately predicting the net section tensile resistance of stainless steel staggered bolted connections using existing design methods. This study therefore experimentally and numerically investigates the structural behaviour and net section tensile resistance of stainless steel staggered bolted connections under tensile loading. A total of 30 austenitic and duplex stainless steel staggered bolted connections (ASTBCs and DSTBCs), fabricated from 6 mm hot-rolled plates, were tested to assess the influence of material type and geometric parameters on the net section tensile strength. While net section fracture along the inclined path was the primary failure mode, shear cracking near the bolt holes was also observed in some specimens. A validated finite element (FE) modelling approach was developed to simulate the full-range tensile behaviour and fracture failure of ASTBCs and DSTBCs. Thereafter, a comprehensive parametric study was conducted to examine the effects of key design parameters, including gauge distance, pitch distance, edge distance, plate thickness, number of bolt lines, and bolt hole diameter. The predictive accuracy of existing design standards, including AS 4100, Eurocode 3, and AISC 360–16, was assessed against the experimental and FE results, revealing limitations in their ability to accurately predict the net section tensile resistance of stainless steel staggered bolted connections. Hence, a new design method incorporating the effect of tensile-to-yield strength ratio was proposed. The proposed design method demonstrated satisfactory agreement with both experimental and FE results, providing a more precise and consistent prediction for both ASTBCs and DSTBCs. Additionally, a reliability analysis was conducted for the proposed design method, recommending an appropriate partial safety factor.