Experimental Behavior and Design of High-Strength Circular Concrete-Filled Steel Tube Short Columns

This paper investigates the behavior of high-strength circular concrete-filled steel tube (CFST) short columns. An experimental database consisting of 87 tests conducted on high-strength circular CFST short columns was compiled, and gaps in the existing research were identified. A total of 20 tests were then conducted to address the gaps in the database. The test parameters were the diameter-to-thickness ratio of the steel tubes D/t, the yield stress of steel F-y, and the compressive strength of concrete f'(c). The tests indicated that the strength of high-strength circular CFST short columns increases with increasing F-y and f'(c), but decreases with increasing D/t. All tested high-strength circular CFST short columns had acceptable ductility. Four of the specimens did not have any strength degradation, while the other 16 specimens retained at least 70% of their strength at strains of 5%. Results from the tests conducted in this research were combined with those from the compiled database; the combined results were used to evaluate the applicability of current design equations for estimating the cross-sectional strength of high-strength circular CFST columns. The evaluations indicated that the Japanese code provides the most accurate estimation. (C) 2019 American Society of Civil Engineers.