The continuous deterioration and/or damages caused in concrete structures during their lifetime have led to the development of new composite materials used for the structural reinforcement. In bridges with durability problems, damaged by external causes or with a likely change in its use or with an increase of the design load, the traditional strengthening methods frequently have disadvantages like the increase of the weight of the structure, the corrosion of the steel and its high cost of manipulation and positioning. More specifically referring to the reinforcement of bridge piers, in recent years the use of fibre reinforced polymers (FRP) has increased as an element of confinement of concrete elements subject to compression due to its excellent mechanical and chemical properties, increasing the resistance and ductility of the piers. However, due to the lack of codes and standards and the lack of experience in the long term behaviour, uncertainties exist in the calculation bases along the dimensioning of this reinforcement and more precisely in the partial coefficients of safety to be adopted. The paper describes the reliability-based calibration of partial safety factors to be used for the confined concrete in the design of strengthening to axial-bending forces using CFRP. The reliability-based procedure is developed based on a theoretical model whose statistical parameters were obtained from a data base of 126 laboratory tests.