ABSTRACT
Tubular steel elements are very suitable for slender frames, where the buckling effects are very important. Steel design codes, and in particular Eurocode-3 (EC3), base the buckling analysis upon the element effective length factor K. This factor depends on the buckling shape of that particular element within the structure, and in practical cases it is obtained by means of approximations.
This paper presents a direct one-step method for the buckling analysis of tubular steel frame structures. The method avoids the use of the effective length factor of each individual element. The key idea is to perform a nonlinear analysis of the structure starting from an initial deformation state that includes the initial imperfections of the elements and so, obtaining the resulting element stresses including the buckling effects. The performance of the method is checked against the procedures established in EC3 by means of a series of numerical examples.
