Buckling of Flexural-Shear Bracing System and Its Braced Steel Frames

Abstract

This paper reports an investigation into the stability of dual systems composed of the multi-storey steel frame and the flexural-shear bracing system. The lateral buckling of cantilever column, to simulate the bracing system in the dual systems, is first studied with both the flexural and shear deformations taken into account. A very accurate solution in simple expression, capable of considering the variations of the sectional properties and axial force along the height, is proposed for the buckling load of such a cantilever column, with which an explicit solution is proposed for the buckling load of steel frames with the flexural-shear bracing system. The threshold stiffness of the flexural-shear bracing system, the minimum stiffness for the braced steel frame failing into the non-sway buckling mode, is also investigated. Utilizing this threshold stiffness, a simple expression illustrating the relationship between the buckling loads of weakly braced frame with the fully braced and unbraced steel frames is presented. Comparisons are made between the predictions of solutions presented in this paper and those from the finite element (FE) analysis, showing reasonable agreements between these two results.