Analytical Load–Strain Model for FRP-Reinforced Concrete Hollow Columns under Axial Compression

The use of fiber-reinforced polymer (FRP) bars as longitudinal and transverse reinforcement in concrete columns has become attractive because of their higher corrosion resistance compared with conventional steel bars. Introducing inner voids into these reinforced concrete (RC) columns to minimize material usage and optimize their strength/weight ratio makes them an efficient design solution for elevated structures, such as bridge piers, under harsh environmental conditions. Therefore, this study proposes an analytical model to predict the full-range axial load–axial strain response of these FRP–RC hollow circular columns under axial compression by explicitly considering the load contribution of three components: (1) confined concrete; (2) longitudinal FRP bar; and (3) unconfined concrete cover. This study introduces a novel analysis-oriented model (AOM) that is based on precise lateral stress distribution within the confined concrete and force equilibrium condition at the interface between the lateral FRP reinforcement and concrete. Then, the axial load–strain predictions that are generated by the proposed model are compared with several existing test results and showed that the model in this study closely captures the experimental outcomes, which outperforms the existing design-oriented model (DOM).