Behaviour of concrete cylinders confined by carbon fiber reinforced plastic

Concrete cylinders confined by CFRP loaded axially in compression display a distinct bilinear stress-strain response with a transition zone around the ultimate strength of unconfined concrete where the decrease in modulus occurs. Prestressed confinement would be favourable to raise the load level of the transition zone for improving performance of strengthened columns, which would become unstable at least up to this load level. A consequent investigation was executed including concrete cylinders of 5 different strengths and confinements with 3 different prestress levels. Theoretical prediction and experiments showed that prestress of the confining device elevates the transition zone, which has importance for the stability of confined concrete columns