Experiments on distortional buckling of I-beams

This paper describes a test program on full-scale fabricated simply supported I-beams with central concentrated load and an effective lateral brace at the midspan of the top compression flange that was performed mainly with the aim of experimental verification and investigation of distortion in doubly symmetric I-section beams. The experimental ultimate loads were compared with the buckling loads of the specimens determined by using the so-called Southwell, Modified, and Massey extrapolation techniques, and in most of the cases very little discrepancy was found between the maximum test and extrapolated loads. Moreover, the experimental beam strengths were compared with the design strengths predicted by the American AlSC/LRFD and the Australian AS4100 specifications. Generally, the two specifications provide unconservative predictions in the inelastic range of structural response as the beam length decreases and inelastic behavior becomes more intense. However, the AS4100 specification provides conservative predictions in comparison with the AISC/LRFD specification.