Development of a consistent design procedure for lateral–torsional buckling of tapered beams

• Current approaches for the verification of non-uniform members are discussed.
• An Ayrton-Perry type formulation is derived for the case of tapered beams.
• Relevant parameters are identified and calibrated against numerical simulations.
• Proposal for lateral-torsional buckling verification of tapered beams is developed.

Eurocode 3 provides several methods for the stability verification of members and frames. However, several inconsistencies and difficulties have been noticed in the case of non-uniform members regarding in what concerns stability verification. In this paper, the case of web-tapered beams is studied. In a first step, available methods for stability verification of web-tapered beams are discussed. A second order analytical model based on an Ayrton–Perry approach is then derived for the case of tapered beams with uniform bending moment and further extended to other bending moment distributions. Several consistent simplifications are carried out in order to build a simple but coherent design model for the stability verification of tapered beams subject to linear bending moment distributions and to parabolic bending moment. More than 3000 numerical simulations are carried out for calibration and analysis of the results. Throughout the paper, specific issues such as the presence of shear or the codified imperfections for welded cross-sections are brought in and taken into account. Finally, it is noted that the proposed model is consistent with recently proposed design models for the stability verification of prismatic beams.