Buckling and Second-Order Effects in Dual Shear-Flexural Systems

Dual systems consisting of two shear-flexural structures are often used in high-rise buildings. This paper presents a second-order analysis of such dual systems, in which closed-form solutions are derived for the lateral flexural and shear displacements, as well as for the bending moments and shear forces in the two structures. The buckling of the dual system is also investigated. It is found that the total buckling load is a simple summation of the buckling loads of the two component structures when they act independently, and that it is independent of the distribution of the vertical loads amongst the two structures. A simple formula for the amplification factors is proposed for use in routine design. The second-order theory developed in this paper is used to investigate the amplification factors for the lateral displacements and bending moments in a typical shear-flexural structure. It is shown that the amplification factors determined from the proposed formula are in good agreement with those obtained by the more rigorous second-order analysis in most cases. It is also found that the various amplification factors are independent of the distribution of the vertical loads among the two structures.