Compression capacity of closely spaced double‐angle members – effect of joint stiffness at member ends

Usually, pinned ends are assumed to calculate the compression capacity of closely spaced double‐angle members. In reality, the joints used in practice provide additional rotational restraints at the member's ends, which significantly influence the compression member capacity of such built‐up sections. The current study systematically investigates this effect. This is realized through a numerical parametric study using finite element models. The varied parameters are: i) member length, ii) type and dimension of the individual angle sections, iii) number of interconnections, iv) dimensions of the gusset plates at the member's ends (i.e. thickness, width and depth). Finally, a design model is introduced which is based on second order theory calculation of an eccentrically loaded column with rotational end restraints. Furthermore, appropriate stiffness functions for these rotational end restraints are presented, also including cases with plastic hinges in the gusset plate. It is shown that this new design model can accurately predict the ultimate compression capacity of closely spaced double‐angle members.