European design rules provide simplified design models for steel beams subjected to biaxial bending moments and torsion (e.g. Annex A of EN 1993-6 [1]). However, these rules do not consider axial forces. This paper presents a combined experimental and numerical study on the structural member behaviour of simple steel beams under axial compression, biaxial bending and torsion. First, an experimental study performed at Ruhr-Universität Bochum is presented. Secondly, a numerical model is developed and validated with the results of the tests. Next, a numerical parametric study analyses the influence of the cross-section, member slenderness ratio and ratio of internal forces on the member stability behaviour. The paper uses the results of both the numerical simulations as well as the experimental investigations for reviewing the existing simplified structural models. Finally, the paper develops and proposes a simplified model for simple steel members subjected to combined axial compressive forces, biaxial moments and torsion.