Development of a consistent buckling design procedure for tapered columns

EC3–EN 1993-1-1 provides several methodologies for the stability verification of members and frames. When dealing with the verification of non-uniform members in general, with tapered cross-section, irregular distribution of restraints, non-linear axis, castellated, etc., the code mentions the possibility of carrying out a verification based on 2nd order theory; however, several difficulties are noted when doing so, in particular when the benefit of plasticity should be taken into consideration.Other than this, there are yet no guidelines on how to apply standardized, easily reproducible rules as those contained in Section 6.3.1 to 6.3.3 of the code to non-uniform members. As a result, practical safety verifications for these members are often carried out using conservative assumptions, not accounting for the advantages non-uniform members provide. In this paper, firstly, available approaches for the stability verification of non-uniform members are discussed. An Ayrton–Perry formulation is then derived for the case of non-uniform columns. Finally, and followed by a numerical parametric study covering a range of slenderness, cross-sections and fabrication process, a design proposal is made for the relevant case of in-plane flexural buckling of linearly tapered columns subject to constant axial force. The proposal is consistent with current rules for uniform columns provided in EC3-1-1, i.e., clause 6.3.1.

► Current approaches for the verification of non-uniform members are discussed. ► An Ayrton–Perry type formulation is derived for the case of non-uniform columns. ► Relevant parameters are identified and calibrated against numerical simulations. ► A proposal for verification of in-plane buckling of tapered columns is developed.