Seismic behavior of high-strength concrete-filled square steel tube columns reinforced with ultrahigh-strength reinforcing bars

This paper investigated the seismic behavior of high-strength concrete-filled square steel tube columns reinforced with ultrahigh-strength reinforcing bars. Three full-scale specimens with different amounts of ultrahigh-strength longitudinal reinforcing bars under a high axial load ratio and cyclic lateral load were tested. The test results demonstrate that the existence of ultrahigh-strength longitudinal reinforcing bars had a significant influence on the seismic behavior of high-strength concrete-filled steel tube columns. Compared with conventional concrete-filled steel tube (CFT) columns, the deformation capacity, bearing capacity and cumulative energy dissipation of these innovative CFT columns are greatly improved, and the cumulative damage and plastic deformation of the specimens decreased with the introduction of steel bars. A calculation model based on AISC360-16 using the superposition method was proposed and verified to evaluate the compressive-flexural strength of the specimen.