Buckling curves for heavy wide flange QST columns based on statistical evaluation

• Existing buckling curves were proposed to check heavy QST steel columns.
• The assignment procedure was based on FE analyses and according to EN 1990.
• A distinction was made between stocky (HD) and more slender (HL) sections.
• Buckling curve a0 (strong-axis) or b (weak-axis) should be used for HD columns.
• HL columns can be designed with buckling curve a (strong-axis) or b (weak-axis).

This paper proposes the use of existing European buckling curves to check the resistance of heavy wide flange quenched and self-tempered (QST) sections made from high-strength steel, failing by flexural buckling. The buckling curves are evaluated according to the statistical procedure given in Annex D of EN 1990 using finite element analyses. The residual stress model as described in a related paper was used to define the initial stress state of the column in the finite element model. A large database was created containing the ratio between the elastic–plastic buckling resistance obtained from finite element analysis and the buckling resistance obtained from the proposed buckling curve for a wide set of column configurations from which a partial factor γRd was deduced. Two different section types were investigated: the stocky HD and more slender HL type, featuring a height-to-width ratio (h/b) of approximately 1.23 and 2.35, respectively. Based on the criterion that the partial (safety) factor γRd should not exceed 1.05 it is suggested to check the buckling response of a heavy HD section according to buckling curve “a0” or “b” when failing by strong-axis or weak-axis buckling, respectively. HL sections are to be designed according to buckling curve “a” for strong-axis buckling and buckling curve “b” for weak-axis buckling.