Safety factors for CFRP strengthening in bending of reinforced concrete bridges

Abstract

Concerning the strengthening in bending of reinforced concrete bridge decks, the use of fiber reinforced polymers (FRP) has increased due to its easy application and excellent mechanical and chemical properties. However, due to the lack of codes and standards and the lack of experience in the long term behavior, uncertainties exist in the calculation bases along the dimensioning of this reinforcement and more precisely in the partial coefficients of safety to be adopted for the material properties. As a consequence, bridge engineers are reluctant to use composite materials in the strengthening of damaged reinforced concrete bridge decks. To try to overcome this problem, this paper describes the methodology for a reliability-based calibration of the partial safety factors to be used for the CFRP material in the design of strengthening to bending. The method requires the definition of a response model jointly with the statistical definition of the model error. This is discussed in the first part of the paper. The reliability-based procedure is developed based on the design equation and the corresponding model. A simple set of partial safety factors is finally proposed for a representative population of RC bridges. The conclusions highlight the importance of incorporating the model error in the calibration. In addition, the paper shows how in some cases it is not feasible to design a flexural strengthening by using CFRP.