Center for Cold-Formed Steel Structures Library


INTRODUCTION Compression members of thin walled open sections may buckle in the torsional-flexural mode at loads lower than the Euler buckling load, because of their low torsional rigidity. Doubly symmetric sections, loaded eccentrically in the plane of symmetry, buckle in the torsional-flexural mode when sufficient strength against flexural yielding is provided in the plane of loading. In singly symmetric sections, the shear center and centroid do not coincide. When such sections are loaded in the plane of symmetry, flexural buckling out of the plane of loading is possible only if the load acts at the shear center. Otherwise, torsional flexural buckling will take place, provided that the strength of the member against yielding, due to bending in the plane of loading, is greater. The torsional-flexural buckling capacity of a member decreases when the distance between the load and the shear center increase. This occurs more rapidly when the load is applied on the open side of the section. Therefore, torsional-flexural buckling may be the determining factor in the designing of concentrically as well as eccentrically (on the open side) loaded singly symmetric sections. Torsional flexural buckling of thin walled singly symmetric sections has been extensively studied by T. Pekoz and G. Winter (Report No. 329). Design simplifications for equal end eccentricities were investigated in detail. The basic differential equations and their solution by the Galerkin method for the case of unequal end eccentricities are also given. The purpose of the present study is to investigate suitable design formulations for unequal end eccentricities utilizing these solutions.


Civil, Architectural and Environmental Engineering


American Iron and Steel Institute

Research Center/Lab(s)

Wei-Wen Yu Center for Cold-Formed Steel Structures



Publication Date


Document Version

Final Version


Final Progress Report

Document Type

Report - Technical

File Type