Eurocode-compliant topology optimisation of steel moment splice connections

To address the meagre use of Topology Optimisation (TO) in the civil engineering industry, the case of bolted moment connections in steel construction has been investigated. Connections are essential in steel structures, contributing up to 25% of the global weight and concentrating the complexity in design and, therefore, the industry's added value. It has been found that compliance with code requirements and difficulties in employing advanced software packages in real, heterogeneous and complex connections are the two major deterrents to the widespread use of TO. Hence, a novel code-compliant methodology was proposed, applied to the cover flange plate under tension of a bolted beam splice moment connection and validated with non-linear Finite Element Analyses (NLFEA). It has been found that a 50% volume reduction is possible by employing linear elastic TO and establishing the non-exceedance of the steel ultimate stress as a criterion. NLFEA showed that if the original joint capacity is to be maintained, the maximum optimisation threshold reduces only 45% of the initial volume. Two critical conclusions are that linear elastic TO could not meet the safety needs and that the introduced validation stage with NLFEA is an essential step, highlighting the novelty and significance of the proposed method. Topologically optimised solutions showed a significant volume and cost reduction, meaningfully contributing to the steel construction decarbonisation goals and leading to joints with a more ductile behaviour.