Simplified design-oriented axial stress-strain model for FRP-confined normal- and high-strength concrete

This study presents a simple yet powerful design-oriented model that makes use of commonly available input data to predict the axial stress–strain behavior of fiber reinforced polymer (FRP)-confined concrete in circular sections. The approach of identifying the most influential parameters on the axial compressive behavior of FRP-confined concrete and developing new expressions based on these parameters by balancing accuracy and simplicity of use was adopted. A comprehensive experimental test database of FRP-confined normal-strength and high-strength concrete (NSC and HSC) was compiled and used in the model development. Although the proposed expressions to predict the axial stress and strain at the ultimate and transition point of the stress-strain curve were simple, the results show that they performed as good as or better than the best performing existing models. Based on these expressions a model to predict the complete axial stress-strain curve of FRP-confined concrete was developed and verified against the available experimental data. The proposed model is applicable to both FRP-confined NSC and HSC with compressive strengths up to 120 MPa, and is the first accurate design-oriented model to provide the complete stress-strain curve of FRP-confined HSC.