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

Abstract

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 elasticplastic 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 γ Rd was deduced. Two different section types were investigated: the stocky HD and more slender HL type, featuring a height-towidth ratio (h/b) of approximately 1.23 and 2.35, respectively. Based on the criterion that the partial (safety) factor γ Rd should not exceed 1.05 it is suggested to check the buckling response of a heavy HD section according to buckling curve "a 0 " 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.

Safety Assessment of Eurocode 3 Stability Designrules for the Flexural Buckling of Columns

“…This is due to the relative amplitude of the residual stress with respect to the yield stress of the member when compared to S235 steel. Figure 6 again confirms that the imperfection factors for S460 may not be adequate, except for h/b>1.2, tf>100mm because they were recently proposed and calibrated as this range was not available in the code (Snijder et al [19], [20]). Finally, note that no cases with h/b≤1.2 and tf>100mm are included in the parametric study since no sections with these characteristics were found in catalogues.…”

“…The recent study presented in [19], [20] about buckling curves for heavy sections was confirmed -the buckling curves chosen for sections with h/b>1,2 and tf>100mm are found suitable;…”

“…The design procedure is summarized in Table 6 for simply supported members of length L, whereas the imperfection factors are summarized in Table 7 for the cross section shapes covered by the parametric study. The latter imperfection factors are considered from Table 6.1 and 6.2 of EC3-1-1 and from (Snijder et al [19], [20]) for hot-rolled heavy cross-sections with tf>100mm and h/b>1.2. In Section 3.3 and Section 3.4 the partial factors γM1 for several subsets are obtained respectively for minor and major axes flexural buckling.…”

Trends in steel structures concerning materials, codes and applications

“…However, these heavy sections are available nowadays. Based on research reported in [7][8][9], Table 6.2 of EN 1993-1-1 is supplemented for these heavy sections.…”

“…5. Finite element model to determine the flexural buckling response [9] v.11.0 implicit environment to obtain the elastic-plastic buckling response (Fig. 5) for a wide set of column configurations.…”