Torsional-Flexural Buckling of Thin-Walled Members

A simple method of calculating the elastic, torsional-flexural buckling load of centrally-loaded, thin-walled columns with singly-symmetrical sections is presented. The method is based on the use of an interaction equation. Curves for determining the parameters necessary to use the interaction equation are given. Because buckling of singly-symmetrical sections can occur either in simple bending or in simultaneous bending and twisting, a set of curves for determining which of these modes is critical for any shape and length is also presented. By the use of effective lengths for bending and warping, the theory, originally limited to hinged and fixed ends, is extended to include members with elastic end restraints as well. Based on various experimental results, the linear theory is shown to predict satisfactorily the carrying capacity of actual columns that buckle elastically.