Elastic tripping analysis of asymmetrical stiffeners

Abstract An energy method is developed for analyzing the flexural-torsional and lateral-torsional buckling (“tripping”) behavior of flanged stiffeners subjected to axial force, end moment, lateral pressure and any combination of these. A strain distribution is assumed and the total potential energy functional is then derived. The strain assumptions coincide with van der Neut's assumption. However, unlike the somewhat obscure differential equation approach given by van der Neut, this study provides a simple, clear, energy approach. Both the rigid web case and the flexible web case are studied. The study explores the effect of plate rotational restraint, and a previously unresolved question regarding plate mode shape is answered. The method requires only four degrees of freedom and therefore the solution process is rapid. A number of sample stiffened panels are analyzed using the ABAQUS finite-element program; the results are in quite good agreement. The method has also been extended to inelastic tripping, and this generalized form shows excellent agreement with experimental tests on typical steel panels. This work will be presented in a second paper, to avoid an overly long publication.