Experimental and Numerical Study of Flexural-Torsional Buckling of Web-Tapered High-Strength Steel I-Beams

Despite now over half a century since its manufacture, high-strength steel (HSS) structural sections have only recently attracted the civil engineering fraternity as a replacement for mild steel in order to achieve lighter design solutions. Contemporary HSS is weldable, reliable and more ductile than its predecessors, leading to designs with lower carbon footprints than those offered by conventional mild steel that provides an entry portal to the circular economy of low emissions, deconstructability and reuse. Further economies may be gained by tailoring the profile of the HSS cross-section to suit the envelope of design actions based on the load cases which it is needed to resist. This paper presents the experimental testing of full-scale web-tapered HSS beams for the lateral buckling limit state, purported to be the first such tests reported in the literature. Fundamental to the buckling strength of HSS is the state of the residual stresses induced during its fabrication by welding, and these are determined by the non-destructive technique of neutron diffraction which is also described. Based on the results of the experimental programme, a numerical technique embedded in the widely-used ABAQUS computational library is described, which may be used to achieve advanced solutions for the flexural-torsional buckling of HSS beams whose webs are tapered to suit the variation of the applied bending moments along their lengths.