Abstract
Axial compression tests have shown fiber reinforced polymer (FRP) tubes to significantly enhance both strength and ductility of concrete columns. However, most experiments and associated models typically do not account for the internal reinforcement, size effect of the column, and the end load-bearing conditions of the tube. An experimental program was undertaken to evaluate the effect of these parameters on the performance of CFFT columns. Glass FRP tubes filled with plain, steel-reinforced, and glass FRP-reinforced concrete were tested with and without end grooves, which would prevent the tube from directly bearing of the axial load. The experiments showed the dowel action of the internal reinforcement to improve the ductility of the columns by restraining the lateral dilation of concrete core. Anempirically derived confinement model, augmented with the stress-strain response of the internal reinforcement, showed close agreement with test results.