Theoretical study of the buckling strength of compression members connected to coplanar tension members

Abstract

In structural systems like diagonal cross-bracings, the out-of-plane deformation of the compression members is restrained by the tension members. The purpose of the theoretical study presented in this paper is to determine the transverse stiffness provided by the tension members and to evaluate the effect of this stiffness on the out-of-plane buckling of the compression members. Two practical cases are considered. The compression member is restrained against out-of-plane buckling by one tension member connected at midpoint or by two tension members connected at third points.The theoretical study shows that the transverse stiffness provided by the tension members does not have to be very large to obtain a significant decrease in the effective length factor. It is also shown that the transverse stiffness depends on the ratio of the axial compression force to the axial tension force and that the effective length factor increases with this ratio. However, even for large values of this ratio, the effective length factor is much smaller than 1.0. For instance, when the axial tension force is 0 and the ratio of the out-of-plane moment of inertia of the tension member to that of the compression member is 1.0, the effective length factor is approximately equal to 0.71 instead of 1.0 for both practical cases studied. Key words: stability, elastic buckling, elastic supports.