ABSTRACT
High-strength concrete (HSC) offers advantages over normal-strength concrete in terms of increased strength, improved performance, and overall economy of construction. However, the use of HSC in seismically active regions poses major concerns because of the brittle nature of material. It is well established that ductility of concrete can be improved through proper confinement. On the other hand, the confinement requirements for HSC columns may become prohibitively stringent when conventional steel reinforcement is used, as these members require proportionately greater confinement than those with normal-strength concrete. An alternative to conventional confinement reinforcement is the use of fibre reinforced polymer (FRP) tubes in the form of stay-in-place formwork.
The objective of this paper is to compare the findings of the experimental investigations on the effectiveness of FRP tubes and steel hoops/spirals as confinement reinforcement for HSC circular columns. HSC of up to 90 MPa was considered in column tests. The columns were tested under a constant axial compression and incrementally increasing lateral deformation reversals, simulating earthquake loading. A carbon fibre polymer composite system was used to manufacture the FRP tubes. Steel confinement reinforcement consisted of spirals or hoops. The experimental results indicate that deformation capacities of HSC circular columns can be improved significantly through the use of FRP tubes, with lateral drift capacities in excess of 10%. It was consistently observed that the FRP tubes provided a superior alternative to conventional steel reinforcement as column confinement.
