Ductility of reinforced concrete members externally wrapped with fiber-reinforced polymer sheets

The effectiveness of external wrapping with fiber-reinforced polymer for enhancing the curvature ductility of lightly reinforcedconcrete members is investigated. Referring to members with circular transverse cross sections, the performances in terms of both strengthand ductility capacities are analyzed, and the predictive reliability of two different recent constitutive models, available in the literatureand able to take into account the softening behavior of confined concrete, is checked. A parameter characterizing the effectiveness of theconfining wrapping is proposed, and characteristic values are suggested. Moreover, referring to ductility increases due to confinementeffects, a comparison is made between the predictions obtained using the constitutive models and simple expressions given in recentcodes. Parametric analyses carried out highlight the importance of a definition of the limits of validity of expressions given in the literaturefor estimation of ductility increases in order to avoid nonconservative assessment.