Buckling resistance of non-uniform steel members based on stress utilization: General formulation

Abstract

In Eurocode 3 (2005) the buckling curve approach is adopted for verification of prismatic columns and beams. It has the flexibility of adjusting imperfection factors according to their sections, steel grade and other relevant parameters. However, for generic single members, built-up or not, uniform or not, with complex support conditions or not, the available possibilities for such cases are the General Method given in clause 6.3.4 of Eurocode 3 (2005) or advanced numerical simulations. The applicability of the general method, however, is limited and in some aspects inconsistent (Simões da Silva et al., (2010)). As an alternative, the stability of non-uniform members can be analysed using numerical GMNIA which is a time-consuming procedure and the output is highly dependent on the experience of the user.In this paper, a novel general formulation for stability design of steel columns, beams and beam-columns with variable geometry, loads and complex support conditions is presented. The verification is based on the buckling mode as shape of the initial imperfection with an amplitude previously calibrated for the standard prismatic simply-supported columns and beams in Eurocode 3. The verification is performed as an interaction equation where the first and second order contributions to the longitudinal stress utilization are added for each cross-section along the member length. Several aspects regarding the member behaviour in the context of a specific buckling mode are discussed and finally, validation of the approach is carried out to show its consistency and accuracy.