Few studies are available on members reinforced internally with fiber-reinforced polymer (FRP) bars and subjected to compressive axial load; therefore, the behavior of FRP internally reinforced concrete columns has not been well established. In this paper, experimental results of 23 nearly full-scale square concrete columns reinforced transversally with glass FRP (GFRP) and carbon FRP (CFRP) ties, and longitudinally with GFRP, CFRP, and steel bars, and subjected to concentric monotonic axial compression