Cold‐formed steel back‐to‐back built‐up beams are efficient and very attractive structural elements which can also offer excellent efficiency in production, both in capacity and material savings. The connection between such built‐up steel components can be easily obtained by screws or bolts, but the developments in the welding processes also lead to other solutions like continuous (laser or MIG brazing) or discrete (spot welding). This paper presents a parametric numerical study on such elements where various shapes and cross‐section geometries will be analysed, using different types of connection between the built‐up steel elements. The results from the evaluation of local and global buckling behaviour of such beams will serve as a base for planning future experimental work. Based on the numerical model, the paper presents the influence of several parameters i.e., the type of the channel section (lipped or plain channels), length of the beam, continuous and discrete connections between channels, the number and the distance between discrete connections along the beam axis and along the beam height. From the parametric study, it is concluded that capacity of the cold‐formed steel back‐to‐back built‐up steel beams is highly affected by the type of connections.

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Beam-to-column joints are one of the most common types of joints in metal structures. In the design of load-bearing aluminium structures, welding, as a joining method, is often avoided because of localised degradation of mechanical properties in the heat-affected zone (HAZ). However, recent experimental studies on the extent and strength of the HAZ show a significant difference compared to very conservative design rules when modern welding techniques are used. Therefore, the numerical study conducted in this paper addresses the influence of HAZ on the mechanical behaviour of the welded aluminium beam-to-column joint. Parametric numerical analyses were performed varying the aluminium alloys, the reduced mechanical properties of the HAZ, and different definitions of the HAZ extent. The obtained results show that the highest stress concentration occurs at the connection between the top beam flange and the column flange, resulting in plastic softening in this region. Different joint capacities were observed by varying the mechanical properties of the HAZ. A detailed overview of numerical models as well as the obtained moment–rotation curves show that the behaviour of some models is not as conservative as assumed in the design standards considered.

With the upcoming release of the second generation of European standards for the design of aluminium structures (Eurocode 9), significant changes in design guidelines are on horizon. The design of aluminium joints is a major component of the improvements and novelties that will be presented in the new generation of this standard. Therefore, this paper provides an up-to-date research overview on aluminium structural joints focusing on beam-to-column joints as well as identifying knowledge gaps and opportunities in this research field.