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

• Presents the basis of the AISC 360-10 design provisions for rectangular CFTs
• Establishes the conservatism of the design provisions using experimental database
• Develops and benchmarks 3D finite element models for rectangular CFTs
• Further verifies conservatism of design provisions using benchmarked models
• 3D finite element models predict behavior of noncompact and slender CFTs.

Rectangular concrete-filled steel tube (CFT) members are categorized as compact, noncompact or slender depending on the slenderness ratio (width-to-thickness b/t ratio) of the steel tube walls. International design codes typically focus on the design of compact CFT members with relatively small slenderness (b/t) ratios. The behavior and design of noncompact or slender CFT members is not addressed directly. This paper presents the basis of the current AISC Specification (AISC 360-10) for the design of noncompact or slender rectangular CFT members under axial compression, flexure, and combined axial and flexural loading. The experimental database of tests conducted on noncompact and slender CFT members is reviewed. Design equations are developed based on the experimental results and observations. Detailed 3D finite element method (FEM) models are developed for noncompact and slender CFT members, and benchmarked using experimental results. The benchmarked models are used to address gaps in the experimental database, and further verify the conservatism of the design equations.