Performance of concrete columns strengthened with fiber reinforced polymer composite sheets

The performance of concrete columns externally wrapped with carbon, glass, and aramid fiber reinforced polymer composite sheets is presented in this paper. The confined and unconfined (control) specimens were loaded in uniaxial compression. Axial load and axial and lateral strains were obtained in order to evaluate stress-strain behavior, ultimate strength, stiffness, and ductility of the wrapped specimens. Results show that external confinement of concrete by FRP composite sheets can significantly enhance strength, ductility and energy absorption capacity. An analytical model to predict the entire stress-strain relationship of concrete specimens wrapped with FRP composite sheets was developed. Comparison between the experimental results and those of analytical indicates that the model provides satisfactory predictions of the stress-strain response. The paper also presents the performance of the wrapped concrete specimens subjected to wet-dry environments. The specimens were exposed to 300 cycles of wetting and drying using salt water. Results show that the specimens wrapped with carbon and aramid fibers experienced no reduction in strength due to wet/dry exposure, whereas those wrapped with glass fiber experienced a significant reduction in strength.