Accurately predicting key reference points on the axial stress–strain curve of fiber-reinforced polymer (FRP)-confined concrete is of great importance for the pre-design and modeling of structures manufactured with this composite system. This paper presents a detailed study on the development of accurate and practical expressions for predicting the ultimate condition and transition point, as key reference points, on axial stress–strain curves of FRP-confined concrete using generic programming (GP). A comprehensive data tuning and cross-validation analysis was firstly performed to develop prediction models. Afterwards, the accuracy and performance of the developed empirical expressions were examined by sensitivity analysis, parametric analysis and model validation. Finally, a comparison was made between the performance of these proposed expressions and that of the existing best-performing expressions in the literature using statistical analysis. Based on the sensitivity and parametric analysis of the database, it is shown that: compressive strength (f’cc) and axial transition strain (ɛc1) are more sensitive to FRP lateral stiffness (Kl); ultimate axial strain (ɛcu) is more sensitive to Kl-to-unconfined compressive strength (f’co) ratio and fiber ultimate tensile strain (ɛfu); hoop rupture strain (ɛh,rup) is more sensitive to fiber elastic modulus (Ef); and axial transition strength (f’c1) is more sensitive to f’co. It is also shown that the proposed expressions provided more accurate predictions of the ultimate condition and transition point on the axial stress–strain curve of FRP-confined concrete than the existing expressions. This was achieved by using a larger number of datasets and accurately capturing the effects of the most influential input parameters in the proposed expressions.
- Axial strain at transition point
- Axial stress at transition point
- FRP-confined concrete
- Genetic programming (GP)
- Hoop rupture strain
- Ultimate axial strain