LATERAL DISTORTIONAL BUCKLING OF STEEL .1. SECTION MEMBERS

The usual types of buckling of steel members assumed in design are lateral-torsional and local buckling modes. In lateral-torsional buckling, the cross-sections of the member translate and twist as rigid bodies. On the other hand, local buckling is characterized by localised distortions of the cross-section over a short wavelength in the absence of lateral translation. These two modes are really limiting buckling types for short members (local buckling) and for long members (lateral-torsional buckling). For intermediate length members, the two modes interact to produce a lateral-distortion at buckle, characterised by simultaneous distortion and lateral deflection of the cross-section. During the past 15 years or so, a proliferation of research work has been undertaken in Australia to quantify the effects of lateral-distortional buckling. The paper provides a survey of this research, and concludes with recommendations regarding the relevance of lateral-distortional buckling to design situations.