ON THE PARADOX OF TORSIONAL BUCKLING OF THIN-WALLED I COLUMNS

摘要

Torsional stability analysis of thin-walled I column with variable width flanges leads to a paradoxical result that the critical load may lie outside of the limits described by the loads of the columns with constant extreme cross-section. The result has been obtained on the basis of the theory of thin-walled beams with non-dcforrnable cross-sections. Moreover, the initial post-buckling analysis shows that the bifurcation points are symmetrical and stable. The investigations, carried out recently, by means of the generic finite element method, allow a conclusion to be draw that omission of the in-plane shear stresses is the main cause of the paradox. In this paper, the validity of the above mentioned findings are reexamined by means of the FEM method based upon a fully nonlinear theory of shells and the ABAQUS System, as well. The numerical examination carried out leads to the conclusions that the paradoxical property of the torsional buckling load is confirmed and the results of stability analysis obtained with aid of the generic finite element method accounting for the in-plane shear effect are not sufficiently accurate.