A unified method for the design of steel beam-columns

In Eurocode 3, Part 1-1 [1] two methods are given for the design of beam-columns. They have been criticized for their complexity. Furthermore, internal plastic redistribution of stresses of class 3 cross-sections is not utilized in the code. These shortcomings were resolved in proposal for amended rules in [5], however, the procedures for beam-columns are still complicated and difficult to understand.
An approximate method for the design of beam-columns was proposed 1968 in [6] which was addressed in the Commentary to the Swedish regulations for steel structures [10] and used in Sweden since then [11]. It was accepted also in Eurocode 9 for aluminium [4], where it is especially convenient to allow for softening of the material at local transverse welds, see [9]. The method is here proposed to be included also in Eurocode 3.
In this paper the resistance of class 3 cross-sections is discussed and the unified method for beam-columns is presented. Four worked examples are presented, three of them on rather complicated structures, to show the capability to treat such structures as well.