Design Interaction Equations for Cylindrical Tubular Beam Columns

Abstract

The aim of the work described in this paper is to provide an improved interaction equation for the design of braced‐steel, cylindrical tubular beam columns. It is found that the current American Institute of Steel Construction (AISC) linear interaction equations generally give a very conservative result for cylindrical tubular members, especially for shorter members and members bent in double curvature, because these equations were developed and refined on the basis of the test results and the exact analyses of wide‐flange members. In this paper, a unified design interaction equation for wide‐flange members under uniaxial bending recently proposed by the writers is extended to the design of cylindrical tubular beam columns. The effects of local buckling and external hydrostatic pressure on the strength of these members are also considered. Extensive evaluations of the proposed equation have been made by comparing with the results of exact inelastic solutions and more than 100 full‐scale tubular column tests, providing final confirmation of the validity of the proposed equation.