Axial stress-strain model for concrete in partially FRP wrapped reinforced concrete columns

Abstract

The application of fiber-reinforced polymer (FRP) composites has become a commonly-used technique for the strengthening/retrofitting of existing reinforced concrete (RC) columns. To date, extensive experimental studies have been conducted in this field, resulting in many stress-strain models of FRP-confined concrete for analysis or design use. Few models, however, are concerned with the concrete in FRP-confined RC columns, especially for the columns under partial FRP confinement. This paper first investigates the mechanical properties of the concrete under FRP strip-transverse steel reinforcement composite confinement via the assessment of existing analysis-oriented models (AOMs). Then, the peak stress of actively confined concrete and the dilation model in AOM are calibrated based on existing research, leading to a new AOM for FRP strip-steel confined concrete. Finally, a test database is assembled to evaluate the reliability of the new model in terms of the predictions of ultimate conditions and stress-strain curves. By comparing the experimental results and theoretical predictions, the proposed model exhibits higher accuracy for the FRP strip-steel confined concrete compared with the other existing models.