Lateral torsional buckling analysis of moment resisting plane frames

Abstract

A finite element formulation is developed to predict the lateral torsional buckling resistance of plane frames with moment connections. The solution focuses on the simple characterization the elastic warping behavior of moment connections in a manner that allows them to interface seamlessly with existing beam buckling finite elements, thus providing means for realistically modelling the lateral torsional buckling of plane frames. Special attention is devoted to the joint rotation effects. The technique successfully captures the interaction between beams and columns of frames, an effect that is neglected in present design methodologies based on individual member checks. The solution is shown to provide lateral torsional buckling resistance predictions in very good agreement with shell based finite element solutions at a fraction of the modelling and computational effort. For typical frames that are laterally supported at the joints, the study suggests that present design methodologies that isolate the member from the rest of the structure provide conservative buckling resistance predictions. Conversely, for frames with no lateral restraints at some of the joints, the present solution predicts lateral torsional buckling resistances that are significantly different from those based on design standard equations, suggesting the need to account for interaction effects in such situations.