Lateral-torsional buckling resistance of aluminium I-beams

This paper presents a detailed investigation into lateral-torsional stability of aluminium extruded I section beams under pure bending. Forty aluminium members of two different alloys 6061-T6 and 6063-T5, representing weak hardening and strong hardening alloys respectively, were tested. Stress–strain relationships were determined by tensile tests with 8 coupons cut from extruded flanges and web. Widths of flanges and lengths of members were herein taken as primary parameters to study lateral-torsional stability of the beams. With rigid lateral-torsional restraint on beam ends, lateral-torsional buckling resistances and load-rotation relationships were obtained by continuous loading. Comparison of numerical predictions with test results indicated that accurate and reliable replication could be achieved by the described finite element (FE) models. By means of measured material behaviour and geometric properties, the corresponding provisions in Eurocode 9 (CEN 2007) and a design method previously proposed by the authors were evaluated by the test results. It was demonstrated that the proposed calculation method could provide cross-section lateral-torsional buckling resistances that are much closer to the test results than design strengths on the basis of the Eurocode 9 provisions are. Therefore, the proposed design method could be an alternative way of predicting the lateral-torsional buckling resistances of aluminium alloy I-beams.