Interaction between critical torsional flexural and lip buckling in channel sections

The energy method is first used to find the critical stress for anti-symmetric lip buckling, for any given half-wave length, including the preferred half-wave length. The energy method is then applied to describe the critical buckling interaction between the torsional-flexural and anti-symmetric lip modes, and its effect in reducing the critical buckling stress. The results obtained by the energy solutions are validated by those obtained by finite element eigenvalue analyses. This paper gives closed form equations which enable the interactive critical stress to be calculated for a member of given geometry. Reductions of up to 24\% in the smaller of the individual buckling stresses have been found for the examples studied. A further paper will describe how the interactive critical stress can be incorporated in a design method for finding the resistance of the member. (C) 2001 Elsevier Science Ltd. All rights reserved.