Stress-Strain Relation of FRP-Confined Predamaged Concrete Prisms with Square Sections of Different Corner Radii Subjected to Monotonic Axial Compression

This paper presents the results of an experimental study on the behavior of predamaged concrete prisms that were strengthened with fiber-reinforced polymer (FRP) jackets. Tests were conducted on 46 concrete columns involving variations of corner radius ratios, damage levels, and confinement pressure. This paper investigates the effect of corner radii on the main parameters of the stress-strain curve for FRP-strengthened predamaged specimens, such as compressive strength, strain capacity, and initial elastic modulus. The test results demonstrated that the efficiency of repairing damaged columns greatly depends on the corner radius ratio. The strength gains after FRP strengthening decrease as the corner radius ratio reduces. Furthermore, this paper extends a well-established stress-strain model originally proposed for FRP-confined predamaged circular concrete columns to square columns. More accurate expressions for the strength, deformation capacity, and stress-strain relationship were developed considering both the corner radius ratio and predamaged level. The proposed model was verified by test results and can predict the stress-strain behavior of a FRP-confined predamaged concrete column with good accuracy.