A thesis submitted in partial fulfillment of the requirements for the degree of Master of Engineering, School of Civil Engineering

Thesis (M.Eng.) - Asian Institute of Technology, 1992

Thin-walled structural members can be used in many ways. When they are employed as columns, they are subjected to buckling by torsion and flexure. In the buckling analysis of thin-walled members, the "Wagner hypothesis" has generally been accepted. But after Ojalvo rejected this theory by presenting his new theory without Wagner's hypothesis, many researches made efforts to settle the dispute on the validity of Wagner's hypothesis. In this study, many arbitrary shapes of cross sections were examined in order to identify conditions under which the theory using Wagner hypothesis are and are not applicable. To demonstrate the difference between the two theories, lateral buckling and combined flexural torsional buckling were investigated. Solving problems of stability of structural members requires a six-node degenerate finite element for geometrically linear and non-linear analysis of thin-walled structures to be developed. This is due to the fact that the stiffness formulation of this element does not invoke the Wagner Hypothesis. The result of the present analysis should establish a valid basis for comparing the two theories.