Strength Analysis of Cellular Steel Members under Combined Compression and Major-Axis Bending

Abstract

Cellular steel shapes offer greater section depth and strong-axis flexural stiffness than their parent hot-rolled shapes, along with web openings for duct system installation. However, their use as structural members other than beams has been constrained by a lack of design guidelines. This research employs both an analytical approach and nonlinear finite element analysis to investigate the strength of cellular steel members under combined compression and major-axis bending. In the analytical approach, the strength interaction equation for cellular steel beam-columns incorporating an initial imperfection is derived using the principle of stationary potential energy. A total of 864 FE models covering practical configurations of cellular steel shapes are analysed to assess the analytical solution and the extension of AISC360 and EC3 strength interaction equations. Effects of the parent shape, web opening configuration, member slenderness, and load eccentricity on the member strength are investigated. The results show that the proposed analytical solution accurately predicts the capacity of cellular steel members under combined compression and major-axis bending. Also, the European Code EC3 strength interaction equation that adopts the refined elastic buckling equation specifically derived for the cellular steel members can accurately predict the strength of practical cellular steel shapes. Finally, a criterion for effective utilisation of the cellular steel shapes is proposed to ensure that they exhibit greater strength than their parent shapes.