Partial safety factors for CFRP-wrapped bridge piers: Model assessment and calibration

Concerning the strengthening or seismic retrofitting of bridge piers, the use of fiber reinforced polymers (FRP) has increased as an element of confinement of concrete 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 bridge piers. 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 confined concrete in the design of strengthening to axial-bending forces using CFRP. 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 and compared with those proposed in existing guidelines.