A NEW DERIVATION OF THE BUCKLING THEORY OF THIN-WALLED BEAMS

摘要

There existed two formulae at present for calculation of flexural-torsional buckling moments of thin-walled beams with monosymmetric Ⅰ-sections. This paper compared the stability theories from which these formulae were derived. This paper presented a buckling analysis of Ⅰ-sectional beams based on the stability theory of shells, which is certainly superior to the beam theories because fewer assumptions are adopted to establish the shell buckling theory. Totally 36 Ⅰ-sectional beams were analyzed using the FEM program ANSYS, among which 12 have doubly symmetrical sections, 12 tensile flange strengthened and 12 compressed flange enlarged. The element SHELL63 was used in the analysis. It was found that the shell buckling analysis verified the traditional formula, not the newer, seemly more rational theory. This paper presented a new derivation of the flexural-torsional buckling theory of thin-walled beams. This new derivation, which is in agreement with the results of shell buckling analysis, verified the traditional formula.