Structural behavior of small square steel tubes reinforced self‐compacting concrete columns under biaxial eccentric loads

Abstract In this study, the structural behavior of small square steel tube‐reinforced self‐compacting concrete (SSTR‐SCC) columns is investigated under symmetric and asymmetric biaxial eccentric loads. Twelve specimens were cast and tested under biaxial eccentric loads. Three specimens (reference specimens) were longitudinally reinforced with 12‐mm diameter deformed steel bars, and the remaining nine specimens were reinforced with small square steel tubes filled with self‐compacting concrete. Steel tubes with three different cross‐sectional dimensions (25 mm × 25 mm, 30 mm × 30 mm, and 35 mm × 35 mm) and a constant thickness of 2 mm were used to reinforce the SSTR‐SCC specimens. All the specimens were laterally confined using 10‐mm diameter steel bar ties at a 50 mm center‐to‐center spacing. Based on the type and size of longitudinal reinforcement, the specimens were divided into four groups, with three specimens in each group. Specimens from each group were tested under three different biaxial loading conditions. The experimental results revealed the better performance of the SSTR‐SCC specimens than the reference steel bar reinforced specimens in terms of maximum axial load capacity and ductility, rendering the small square steel tubes a viable option to reinforce concrete columns subjected to biaxial eccentric load.