A rational model for the distortional buckling of tapered members Original Research Article

A general finite element is developed for the analysis of coupled local and lateral buckling of steel structures composed of tapered I-sections. Structures such as gable frames and steel bridges fall into this category. The present method is capable of considering both the tapering of the flanges as well as the web. The effect of vertical web stiffeners is handled automatically, and loading remote from shear centre can also be incorporated. The analysis is performed in two stages: in-plane and out-of-plane. The resultant in-plane stresses are used for the out-of-plane initial loading pattern. This arrangement results in a general eigenvalue problem, where the buckling load and mode are found using algorithms such as the Sturm Sequence and Random Force Vector methods. The accuracy of the method is then demonstrated in several examples incorporating tapering of both kinds. Finally, the method is used to investigate the significance of distortion in the buckling of a typical gable frame under gravity loads.