A direct holistic design approach for reinforced concrete beams strengthened with FRP

This paper describes a procedure for flexural and shear design of reinforced concrete beams strengthened with externally-bonded fibre reinforced polymer (FRP) materials. The method of analysis utilized is based on the Strut-and-Tie Model. Given the target resisting moment and the properties of the un-strengthened beam, the procedure allows a step by step approach to directly calculate the required longitudinal and transverse externally bonded reinforcement needed to assure the desired hierarchy of internal resistance. The key element of the proposed design approach is the presence of a combination of longitudinal and transverse reinforcement in order to activate a synergistic interaction capable of preventing or delaying undesirable premature and brittle failure modes, such as those influenced by bond slip and/or separation of the external or internal longitudinal reinforcement. A numerical example shows the feasibility of the proposed procedure.