A comprehensive assessment of curling effects in stainless steel bolted connections

There has been a significant increase in stainless steel investigations related to steel construction in the last few years, contemplating numerical and experimental studies. This fact is associated with the excellent properties these materials can provide compared to carbon steel, such as corrosion resistance, durability, fire resistance, and added aesthetic value. On the other hand, the current standards and design codes are still mostly based on carbon steel analogies that do not consider stainless steel's hardening response. The stainless steel has a distinct structural behaviour; its stress versus strain curve is nonlinear from low-stress levels and does not present a well-defined yield plateau. The present investigation was centred on developing experimental and numerical tests to clarify the response of splice connections. The experiments and numerical models involved stainless steel thin-plates connected by a single bolt (with two shear planes). Comparisons with current design codes and the new stainless steel design manual recommendations were also performed. The main aim of the performed studies was to investigate the influence of the curling effect over the bolted connections strength since this phenomenon can reduce the connection load-carrying capacity. The main investigated parameters were the end distance, e(1), plate thickness, t and the adoption of stiffness plates. The results indicated that the curling effects were not significant for connections with e(1)/d ratios less than 3.5. A transition zone was also observed from this value up to 3.0, where the connections ultimate strength was only slightly influenced. Comparing thin-plate connections of the same geometry, with and without curling effects, led to 8% and 20% reductions of the ultimate capacity of austenitic and ferritic bolted connections. Alternatively, in thick-plate connections (5 mm), this effect could not be observed. The present investigation confirmed that a solution to minimize curling effects could be achieved using plate lips with heights equal to one-third of the plate width.