High-strength rectangular concrete-filled steel tube long columns: Parametric studies and design

High-strength steel and concrete materials (i.e., steel with yield stress F-y > 525 MPa and concrete with compressive strength f'(c) > 70 MPa) have been applied in various types of structures because they can increase the resistance and space efficiency of the structure. However, the AISC Specification (AISC 360-16) does not permit the use of high-strength materials in concrete-filled steel tube (CFT) members due to a lack of adequate research. This paper aims at investigating the behavior of high-strength CFT long columns and evaluating the applicability of current design equations for high-strength rectangular CFT long columns. Firstly, an experimental database including 74 tests of high-strength rectangular CFT long columns was compiled and gaps in the database were identified. Then, finite element (FE) models were developed and benchmarked for parametric studies. The effects of width-to-thickness ratio of the steel tube, yield stress of steel, compressive strength of concrete, and length-to-depth ratio of the member were investigated. Finally, new design equations for high-strength rectangular CFT long columns were proposed based on the modified slenderness reduction factor in AISC 360-16.