FRP spiral strip-confined concrete columns: Stress-strain behavior and size effect

Abstract

It is well-known that the hoop rupture strain of fiber-reinforced polymer (FRP) jacket in an FRP-confined concrete column is commonly much lower than that obtained from coupon tests. To improve the strain efficiency of the FRP jacket, FRP spiral strip wrapping scheme has been proposed. In the present study, totally 24 circular column specimens [including 16 FRP spiral strip-confined concrete (FSSCC) column specimens] of four different sizes, with a diameter ranging from 100 mm to 400 mm, were tested under uniaxial compression. The particle image velocimetry (PIV) technique was adopted to obtain the hoop and axial strains as well as the strain distributions of the test specimens. The test results showed that the FRP hoop rupture strains measured by the PIV technique in the FSSCC columns are close to that from the coupon tests. The size effect in terms of compressive strength and stress-strain behavior is obvious in the test FSSCC columns. An existing stress-strain model for FRP-confined concrete was then modified to predict the test results. Finally, a field application of the FRP spiral strip wrapping technique completed recently was also briefly introduced.