Square Reinforced Concrete Columns with Slender Bars Strengthened through Fiber Reinforced Polymer (FRP) Sheet Straps

The paper presents the performance of the existing stress – strain models that are proposed for FRP confinement of concrete columns through partial wrapping. The analytical models are compared against the experimental results of an investigation concerning square columns (150 mm side and 750 mm height) with slender longitudinal bars of different quality. The columns were wrapped partially by light glass FRP sheet confinement. A total of 16 specimens of low concrete strength were tested. Six of them were plain concrete columns while five columns contained four longitudinal bars of 220 MPa nominal yield strength and the remaining columns included four bars of 500 MPa nominal yield strength. Four different levels of strap glass FRP confinement were examined. The columns were subjected to monotonic loading up to failure. Partial light glass FRP confinement can enhance significantly reinforced concrete column strength and deformability. The effect of the partial wrapping is higher in columns with internal steel reinforcement. The study investigates the performance of four existing models. The model by Barros & Ferreira provides fairly accurate prediction of the whole stress-strain behaviour of the partially FRP confined reinforced concrete columns