INELASTIC BUCKLING OF I-BEAMS WITH CONTINUOUS ELASTIC TENSION FLANGE RESTRAINT

I-section beams may be restrained continuously along one flange. Two c ommon applications of this are in composite tee-beams where buckling m ay occur in the hogging region, and half-through girder bridges consis ting of two parallel I-section beams connected by a deck at the bottom flange level. In these applications, the compression flange is restra ined only by the stiffness of the web, and the buckling mode is genera lly lateral-distortional. The elastic buckling mode in the compression flange is commonly predicted by the U-frame approach, and this method assumes that the half-through girder or composite tee-beam is subject ed to uniform bending. The elastic buckling load may then be converted into a design strength utilising the interaction between elastic buck ling and yielding. The paper uses an energy method of analysis to stud y the inelastic buckling of beams continuously and elastically restrai ned at the tension flange level, being typical of half-through girders . The inelastic buckling strength is predicted by recourse to the U-fr ame model and to the Australian AS4100 steel structures standard as we ll as the numerical method, and discrepancies between the design metho d and the accurate formulation are noted. (C) 1998 Elsevier Science Lt d. All rights reserved.