The experimental study aims to investigate uniaxial behavior of ultra-high-performance fiber-reinforced composite (UHPFRCC) columns with compressive strengths of 180, 150, and 120 MPa. Eleven square columns and six circular columns will be constructed and tested with uniaxial load. Main variables were the amount and spacing of transverse reinforcement, and concrete compressive strength. The amount and spacing of transverse reinforcement were chosen based on the seismic design provisions of ACI Code (ACI 318-14) and CSA Standard (CSA 2014).

In this study, uniaxial compression tests were performed to investigates the stress-strain relations of Double Skinned Composite Tubular Columns reinforced with steel tube. The confined concrete has been known as the strength of concrete increases significantly. Specimens reinforced with outer and inner steel tube were tested by uniaxial compression test. To investigate the influence of concrete strength increase by confining conditions in steel tubes, 8 specimens with different thickness of tube, hollowness ratio and concrete strength were tested and compared with other researcher's concrete material model.