Lateral–distortional buckling of I-beams and the extrapolation techniques

Abstract Various extrapolation techniques are utilized for predicting the critical buckling load of structural members undergoing lateral buckling. For the application of these methods it is only necessary to have data relating load to a deformation characteristic. In order to obtain an experimental comparison of the Southwell, Modified, and Massey Plot methods, these have been applied on lateral deflections and web transverse strains of four full-scale simply supported I-beams subjected to a central concentrated load with an effective lateral brace at the midspan of the top flange, undergoing inelastic lateral–distortional buckling. Although there is some scatter due to the application of various deformation variables and extrapolation techniques, the agreement between the extrapolated and the maximum test loads is generally good. The smallest discrepancy is found in the case of the Modified Plot. Moreover, in addition to demonstrating direct coupling between the lateral deflections and the web transverse strains representing web distortion, it is also shown that good predictions are provided by applying the Meck Plot on these deformation variables.