Postbuckling Shear Capacity of Thin Steel Tubes

Abstract

The postbuckling behavior of thin‐walled fabricated steel tubes under transverse shear and bending shows a stable carrying mechanism largely consisting of a banded tension field. This phenomenon, coupled with the possibility that the ultimate load is severely affected by residual stresses due to cold bending in the fabrication process, suggests the use of this stable postbuckling mechanism as a design basis. Hence, an equivalent truss mechanism composed of a helical tension field and inclined compression struts is proposed. The corresponding shear‐carrying capacity relations are developed. The magnitude of postbuckling shear capacity is controlled by the banding phenomenon of the tension field, the local “across‐the‐buckles” bending moments, and the inclination of the compression struts. The developed relations recognize the upper and lower bounds of these phenomena. A comparison is held to existing test and numerical data.