Design Considerations for Distortional Lateral Buckling

Abstract

A finite-element formulation is presented for the elastic distortional buckling analysis of doubly symmetric wide flange beams. The formulation characterizes the distribution of the lateral displacement along the web height through Fourier modes and is equipped with features to capture the load height effect and to enforce user-defined kinematic constraints. The formulation is used to investigate the load height and bracing height effects and develop a database of over 20,000 runs on practical beam cross-sections to characterize (1) the reduction in critical moment capacity due to web distortion; and (2) the effect of a load height on the elastic critical moments. A novel indicator characterizing web distortion along the beam span is proposed and integrated within the finite-element formulation in a procedure devised to optimize the location of transverse stiffener(s) along beam spans so as to reduce cross-sectional distortion and maximize the elastic critical moment attainable. The procedure is then applied to optimize the design of beams in two case studies.