Cellular members loaded by an eccentric axial force: a design rule proposal for the elastic critical buckling load

Cellular members are steel I-section members with large circular web openings that appear in a regular pattern. Due to these openings, cellular members loaded in bending have a number of advantages over classical I-section beams, the main one being optimisation of material use. Therefore, structures with cellular members will be lighter in weight and appearance. Mostly, they are used in applications in which they are solely subjected to a bending moment, but a combination of a relatively large bending moment and an axial force is also possible. Compared to classical I-section beams, the failure behaviour of cellular members loaded by a combination of strong-axis bending and axial compression will be altered due to the presence of the web openings. However, to the best of the authors' knowledge, the behaviour of cellular members in this loading condition is still unknown. This behaviour is currently being investigated by the authors. As a part of this extensive research, the authors have studied the elastic buckling behaviour of simply supported cellular members loaded by an eccentrically applied compressive axial force. In this paper, an analytical expression for the out-of-plane buckling load will be proposed. This expression is based on the results for the two limiting cases of the examined loading scenario - pure compression and simply bending - that were obtained in earlier research by the authors. Furthermore, the results of the proposed design rule will be compared with the results from finite element simulations in Abaqus for a large variety of realistic cellular beam geometries. In future work, the failure behaviour of cellular members in this loading condition will be further examined by considering beam imperfections and geometrically and material nonlinear behaviour