Lateral and Local Buckling of Beams and Frames

A finite element model is presented for the lateral buckling analysis of beams and frames having a plane of symmetry in the midsurface of the web. In-plane and out-of-plane behaviors are assumed to be uncoupled. Lower order displacement assumptions are used for the geometric stiffness matrices than for the conventional stiffness matrices. Specific applications of the two-dimensional model are demonstrated for the analysis of structures having I-section members. The proposed model for such members accounts for the interaction between the local and the overall buckling phenomena. The web is allowed to distort. Realistic representation of I-section structures with tapered members, deep sections, complex joints, web stiffeners, and various elastic restraints can be made. Effects of stress concentrations at the joints and under the loads are considered. Three numerical examples: (1)A beam with a stiffener; (2)a gable frame; and (3)a deep highway bridge girder, are presented to illustrate the applicability of the model.