ABSTRACT
The paper discusses the effects of both in-plane displacements and second order P–δ bending on the elastic flexural-torsional buckling of beam-columns. An energy based solution of the elastic flexural-torsional buckling limit curves under arbitrary proportion between the major axis bending moment and the axial force is presented. The novelty of the approach is related to the development of an improved closed-form solution, in which the equivalent uniform moment modification factor should vary not only with the minor axis buckling force utilization ratio N/Nz but also with that of major axis buckling N/Ny represented by the factored ratio N/Nz (1-k 1). Investigations include the effect of in-plane displacements resulting from an arbitrary moment gradient on the elastic flexural–torsional buckling of thin-walled narrow flange and wide flange double-tee section members. The obtained solution is illustrated by elastic flexural-torsional buckling curves for different values of the factor k 1 of a beam-column subjected to unequal end moments.
