Estimation of stress intensity factor (KI) for an FRP bonded concrete beam using the superposition method

The deterioration of civil concrete infrastructures has increased dramatically in recent years. The majority of recent studies have focused on the use of fibre-reinforced plastic (FRP) materials to strengthen or reinforce decayed concrete structures by bonding the FRP plate externally onto the damage surface, These studies have concentrated on the shear and peel-off effects of the adhesive material rather than the failure mechanisms of the concrete itself However the stress intensity factor, K-1, at the crack-tip of the strengthened cracked concrete structures, cannot be overlooked. Numerical and experimental investigations have prove that K-1 of the strengthened structure is highly influenced by the modulus and geometry of the reinforced plate. Therefore, the failure of the strengthened specimen may be due to a high K-1 value in the concrete material. In this paper, a theoretical model is proposed to estimate the value of K-1 with different reinforced plate properties for a strengthened concrete beam using a simple superposition method. The results from the proposed method compare well with the numerical solutions obtained from the finite-element method. Both results show that the steosintensity value, of the beam decreases as the modulus and thickness of the reinforced plate increase, while the closing force of the beam, induced by the reinforced plate, increases.