Concrete Columns Reinforced with High-Strength Steel Subjected to Reversed Cycle Loading

The use of high-strength steel bars in concrete columns can reduce steel congestion and construction costs. The purpose of this study is to investigate the seismic behavior of concrete columns with high-strength steel bars. Six concrete columns were subjected to reversed cycle loading: two columns were reinforced with conventional steel bars (HRB400) and four columns were reinforced longitudinally with high-strength steel bars (HRB600). Other experimental variables were: axial compressive stress (0.2fc, 0.4fc, and 0.5fc) and spacing of transverse reinforcement. Test results showed that columns reinforced with high-strength steel bars exhibited larger flexural strength and energy dissipation, similar driftcapacity, and smaller ductility when compared with the control columns. High axial compressive stress can enhance the flexural strength of columns with high-strength steel bars within the bounds of the variables tested. Columns with high-strength steel bars sustained bond failure around the longitudinal bars, raising questions about degradation in the strength and stiffness of columns, as well as a decrease of longitudinal bar strains.