Lateral torsional buckling of partially restrained beams of high strength S690 welded I-sections

Abstract This paper reports a systematic experimental investigation into the structural behaviour of a total of eighteen simply supported beams of high strength S690 welded I-sections with various restraint conditions, focussing on lateral torsional buckling. Deformation characteristics of these beams, critical failure modes and moment resistances, are fully presented and discussed. In general, these beams of S690 welded I-sections were found to behave in an essentially similar manner to beams of S355 I-sections. Lateral torsional buckling in these beams was thoroughly assessed and compared with the predictions of EN1993-1-1 using their non-dimensionalized slenderness, determined using the procedures of EN 1993-1-1, and measured mechanical properties, geometrical dimensions and restraint conditions. It was demonstrated that the codified design rules were very conservative when being extended to cover these beams of S690 welded I-sections. This comprehensive experimental investigation provides scientific evidence and test data that highlights a need to improve structural efficiency of the design rules in EN 1993-1-1 so that structural engineers can fully exploit the structural benefits offered by these high strength S690 steels in construction.