Proposed procedure for the design of RC flexural members strengthened with FRP sheets

As the development of new materials (particularly FRP) spawns innovation in the field of structural engineering, an accepted procedure for the design of the strengthened system must be created. The goal of this paper is to present a design protocol and suggest alterations/additions to the language of the current ACI-318 code for the use of FRP materials as strengthening reinforcement externally bonded to the concrete. The focus of the discussion is the design of RC members subjected to flexure. Thus, the design for shear strengthening or concrete confinement under compression is not addressed. The paper presents the design at ultimate state using the classical failure mode of steel yielding followed by concrete crushing or FRP rupture. In addition, the topic of required ductility is addressed. For the service state, acceptable stress levels in all materials at working loads and deflection are also considered, taking into account residual stresses. The proposed methodology can be a useful tool for professional engineers