Combined-section columns composed of two separate steel sections present an ideal and economic design for long columns subject to high values of bending moments and axial forces. Research dealing with design of these columns is currently insufficient. At present, most codes of practice consider each column's component to behave either separately or rigidly connected to the other components. As such, the main objective of this research is to scrutinize the behaviour of laced-section columns which are subjected to eccentric loading and propose design criteria for them. In this paper, a non-linear numerical model for these columns is developed based on the finite element method. The results of the numerical model are first verified against the outcomes of experimental investigations available in literature. Then, the model is adopted to simulate the behaviour and the capacity of the combined laced columns. The numerical model includes both the geometric and materials nonlinearities along with the effect of initial imperfections.