Analysis-Oriented Stress–Strain Model for Prestressed FRP-Confined Circular Concrete

To develop an analysis-oriented stress-strain model for prestressed fiber-reinforced polymer (FRP)-confined circular concrete, the differences in path-dependent response between prestressed FRP-confined concrete and actively confined concrete were systematically investigated. Existing experimental data were used to examine the applicability of the stress-path independence and strain-path independence assumptions under different prestressing methods. The results indicate that the continuous filament winding method generally satisfies the stress-path independence assumption, whereas expansive-type methods require consideration of the effect of initial lateral confinement on the axial stiffness of concrete. After removing the initial lateral confinement strain, prestressed FRP-confined concrete exhibits pronounced strain-path dependency relative to actively confined concrete. Accordingly, the peak stress, peak strain, and lateral strain-axial strain relationship were consistently modified, and an iterative computational framework was established to construct a complete stress-strain analytical model. Validation against independent experimental data demonstrates that the proposed model can accurately predict the axial stress-strain response, lateral dilation behavior, and compressive strength, thereby providing a theoretical basis for nonlinear analysis and engineering applications of prestressed FRP-confined concrete members.