Behaviour of carbon fibre–reinforced polymer-confined hollow circular concrete columns with inner polyvinyl chloride tube

Existing studies have shown that the use of an inner tube can significantly enhance the effectiveness of confinement in fibre-reinforced polymer-confined hollow columns. The inner tube used in the existing studies, however, generally had a large stiffness and also served as longitudinal reinforcement. The use of a stiff inner tube is inefficient in resisting bending for hollow columns with a relatively small void and may be unnecessary for constraining the inner surface of concrete. Against this background, this article presents the first experimental study on fibre-reinforced polymer-confined hollow columns with an inner polyvinyl chloride tube. The experimental program included a total of 18 specimens which were tested under axial compression. The test variables included the section configuration (i.e. solid specimens, hollow specimens and hollow specimens with a polyvinyl chloride tube) and the thickness of fibre-reinforced polymer. The test results showed that due to the beneficial effect of the polyvinyl chloride tube which provided constraints/confinement from inside, fibre-reinforced polymer-confined hollow columns with an inner polyvinyl chloride tube generally possessed good strength and ductility compared to their counterparts without a polyvinyl chloride tube.