Elastic local buckling formulae for thin-walled I-sections subjected to shear and direct stresses: Fid-Bau Portal

Elastic local buckling formulae for thin-walled I-sections subjected to shear and direct stresses

Lapira, Luke / Gardner, Leroy / Wadee, M. Ahmer

Abstract Formulae for calculating the elastic local buckling stresses of doubly-symmetric thin-walled I-section girders subjected to combined shear and direct stresses, accounting for the interaction between the plate elements are presented. The interaction between the plate elements (i.e. the flanges and web) is bounded by a theoretical lower-bound, where there is no interaction and the critical plate is considered to be simply-supported, and a theoretical upper-bound where interaction is strongest and the critical plate is considered to have rotationally fixed edges. The interaction is accounted for by introducing an interaction coefficient $ζ$ that quantifies the relative level of fixity between the aforementioned lower and upper bounds. Expressions to calculate $ζ$ are calibrated using results from finite element analyses generated in Abaqus. Doubly-symmetric I-sections of varying geometric proportions loaded in shear, major axis bending, compression and a full range of combinations thereof are considered. Using the developed formulae, the elastic local buckling stresses of the studied cross-sections are accurately predicted, typically within 5% of the values obtained from FE models; this is a significant improvement over the results determined in the traditional manner in which plate element interaction effects are ignored, where the full cross-section buckling stress is shown to be underestimated by as much as 40%.

Graphical abstract Display Omitted

Highlights • Elastic buckling stress of thin-walled I-sections under shear stress is determined. • Interaction coefficient quantifies restraint of critical plate element boundaries. • Elastic buckling stress predicted to within 5% of FE results. • Buckling stress under combined shear and direct stresses also predicted accurately. • Significantly improved predictions when compared to the current EC3 provisions.