High-Strength Rectangular CFT Members: Database, Modeling, and Design of Short Columns

Abstract

AISC 36-16 (the current AISC Specification) does not endorse the use of high-strength materials (Fy≥525 MPa and fc′≥7 MPa) for concrete-filled steel tube (CFT) columns because of a lack of adequate research and comprehensive design equations. This paper makes a contribution toward addressing this gap and proposes effective stress-strain relationships and design equations for high-strength rectangular CFT members using a three-step method. The first step consists of compiling the experimental database of high-strength rectangular CFT column tests in the literature and evaluating the possibility of extending the current AISC 36-16 design equations to high-strength rectangular CFT short columns. The second step consists of developing and benchmarking detailed three-dimensional (3D) nonlinear finite-element models for predicting the behavior of high-strength CFT columns from the database. The benchmarked models are then used to perform comprehensive parametric studies to (1) address gaps in the database and (2) develop effective stress-strain relationships for modeling the steel tube and concrete infill of high-strength rectangular CFT members, while indirectly accounting for the effects of confinement, yielding, and local buckling. The third step consists of using these effective stress-strain relationships and the enhanced database to propose a new design approach (including equations) for high-strength rectangular CFT short columns. Finally, a reliability analysis is performed to establish a resistance (strength reduction) factor (ϕ) to be used with the proposed design equations.