RC members strengthened with externally bonded FRP plates: A FE-based limit analysis approach

Fiber-reinforced-polymer (FRP) strengthening systems have been increasingly studied and used as an effective strategy to rehabilitate existing reinforced concrete (RC) structures. The present paper addresses the problem of predicting the load-carrying capacity of these strengthened structural elements. To this aim, in the framework of limit analysis a numerical methodology is presented which employs iterative finite element (FE) analyses with adaptive elastic parameters and a multi-yield-criteria formulation. The latter is adopted to appropriately describe the constitutive behaviour of the three main constituent materials, namely: concrete, steel reinforcement bars (re-bars) and strengthening FRP-laminates. The effectiveness of the promoted methodology is verified by comparison between numerical results and experimental findings regarding FRP-plated RC elements. Despite being based on a simplified approach which is affected by the underlying assumptions of limit analysis theory, the numerical procedure may be useful for the assessment of the load-carrying capacity in large RC structures repaired or retrofitted by FRP plates. Potentialities and limitations of the proposed methodology are discussed carefully.