A stress-path dependent stress-strain model for FRP-confined concrete

High-strength concrete (HSC) has higher strength-to-weight ratio and stiffness than normal-strength concrete (NSC). Therefore, the use of HSC can decrease the construction and demolition waste and embodied carbon content of structural members that enhances the urban sustainability. However, HSC is more brittle than NSC. To further push up the maximum concrete strength limit in practical construction, confining concrete by fibre-reinforced polymer (FRP) has been advocated to restore ductility. Compared with using hollow-steel tube as confinement, FRP has lighter weight, higher tensile strength, better corrosion resistance, and is more durable and flexible. Nevertheless, it is up to now a difficult task to predict accurately the uni-axial stress-strain behaviour of FRP-confined concrete since the effect of confining stress, concrete strength, hoop and axial strains are interrelated and need to be determined simultaneously. Herein, to better understand and simulate the behaviour of FRP-confined concrete, a stress-strain model has been developed, which consists of the following three main components: (1) A hoop strain equation elaborated from the authors' previous study on steel-confined concrete columns for application to FRP-confined concrete; (2) A modified confined concrete model considering stress-path of confining stress (or history of hoop strain); (3) Interaction between FRP and concrete. The model was verified based on 321 test results obtained from the literature, the design application of the which to a broad range of FRP-confined concrete structures is thus ensured.