Design of composite columns based on Eurocode – comparison between general and simplified methods

Abstract

[EN] In this paper, the results of a comprehensive parametric study for the member capacity of columns subjected to axial forces on the one hand and axial forces plus bending moments on the other hand are presented, considering all relevant types of composite sections: a) concrete encased sections, b) partially encased sections, c) concrete filled rectangular and circular tubes. Different steel grades and concrete strength classes are also considered. Firstly, the different methods of design in the Eurocode are briefly summed up: a) simplified method, based on buckling curves, for axial forces only, b) simplified method, based on a section verification with 2nd order moments, including equivalent geometric imperfections, c) a general method, based on geometrical and material nonlinear calculations with 3D-FEM-models. In the main part of the paper, the buckling resistance of the columns, based on these 3 methods, are compared, over the whole range of relative slenderness, for different section types, material strengths and type of loading (N, N + Mz, N + My). Also in the case of columns subjected to bending moments about the strong axis and axial forces, buckling about both axis is studied in detail.