Noncompact and slender circular CFT members: Experimental database, analysis, and design

Abstract

The AISC 360-10 Specification categorizes circular concrete filled steel tube (CFT) members as compact, noncompact or slender depending on the slenderness ratio (diameter-to-thickness D/t ratio) of the steel tube walls. International design codes typically focus on the design of compact circular CFT members with relatively small slenderness (D/t) ratios, and the behavior and design of noncompact and slender circular CFT members is not addressed directly. This paper presents the basis of the current AISC Specification (AISC 360-10) for the design of noncompact and slender circular CFT members under axial compression, flexure, and combined axial and flexural loading. An experimental database of tests conducted on noncompact and slender circular CFT members is compiled, and used to establish the conservatism of the design equations in the AISC Specification. Detailed 3D finite element method (FEM) models are developed for circular CFT members, and benchmarked using the database of experimental results. The benchmarked models are used to conduct parametric studies to address gaps in the experimental database, and further verify the conservatism of the design equations. The AISC 360-10 Specification is recommended for the design of noncompact and slender circular CFT members. Additionally, the numerical models developed and benchmarked for circular CFT members are recommended for future investigations.