Behavior of circular CFRP-steel composite tubed high-strength concrete columns under axial compression

Application of high strength concrete (HSC) is an effective way to reduce the column size in high-rise and largespan structures, resulting in more available floor space. The concern on the brittleness of HSC can be alleviated by providing some confinement to it. To this end, carbon fiber reinforced polymer (CFRP) and steel tube are found to be very effective. This paper presents experimental and theoretical studies on the axial behavior of CFRP-steel composite tubed HSC columns. Totally, 25 specimens were tested to investigate the influences of CFRP layers, diameter-to-thickness ratio of steel tube, and concrete strength on the load bearing capacity and deformation behavior of such composite members. The observed failure modes, stress-strain relationships, stresses of steel tubes, and deformations of concrete are discussed. The experimental results indicate that with enough CFRP sheets the load bearing capacity and deformation behavior of core concrete are significantly improved, especially the ductility of specimens with concrete strength of 105 MPa. Calculation methods for the axial load bearing capacity of a CFRP-steel composite tubed HSC column are presented and discussed.