This paper aims at showing the potential of geometrically exact beam finite elements to assess, accurately, the non-linear behavior of steel and steel-concrete composite beam-columns. First, one discusses the formulation and implementation aspects of 2D/3D geometrically exact beam finite elements, including geometric imperfections, residual stresses and material non-linear laws for both steel and concrete. Then, a set of numerical examples is provided, to demonstrate the capabilities of the proposed finite elements. Finally, the finite elements are employed to investigate: (ⅰ) the buckling behavior of concrete encased steel I-section beam-columns and (ⅱ) the lateral-torsional buckling behavior of wide flange steel I section beams. The results obtained are then compared with the buckling loads provided by Eurocodes 3 (steel) and 4 (steel-concrete) and relevant conclusions/recommendations are drawn.
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