Buckling of welded high-strength steel I-beams

Abstract

National constructional steel design standards preclude many high-strength quenched and tempered steel grades, and with the growth update of such steels in structural applications, revision or new guidance is needed. This paper reports experiments and presents numerical studies of welded high-strength steel (HSS) I-section beams fabricated by welding BISPLATE-80 (nominal yield stress fy = 690 MPa) and BISPLATE-100 (fy = 890 MPa) plates. For the experimental program, three BISPLATE-80 and five BISPLATE-100 I-sections were fabricated and tested under scenarios of uniform bending and moment gradient. The specimens were designed to develop either lateral-torsional or local buckling modes, with tensile fracture not being observed during the tests. The buckling capacity so obtained significantly exceeded the predictions of Eurocode 3 and of the Australian AS4100, especially for intermediate beam slendernesses, while the ANSI/AISC 360–16 guidelines marginally estimated the buckling resistance of specimens. It was also found that lateral-torsional buckling initiated after partial yielding of the compression flange. The numerical studies consisted of two ABAQUS finite element (FE) models, being a test simulation model as well as a generic representation, to facilitate extending the pool of experimental data, which showed that Eurocode 3 and AS4100 underestimate the buckling strength of intermediate and slender beams, while the ANSI/AISC 360–16 curves overestimate the FE predictions for lateral-torsional buckling capacities of beams in inelastic portions. A parameter that is dependent on the material properties is introduced in the AS4100 beam buckling strength formula and a new curve for the buckling of HSS flexural members is proposed.