The J-factor versus the safety factor applied to design of FRP reinforced concrete structures

FRP reinforced concrete structures lack ductility in the traditional sense of the word. This means that the customary ductility factor cannot be defined for or applied to FRP reinforced concrete structures. To overcome this difficulty, some investigators and design codes have defined an overall performance factor, termed J-factor. The J-factor is the ratio of the product of moment and curvature at ultimate to the product of moment and curvature at strain of 0.1% at the extreme compressive fibre in the concrete. In this paper, using the moment-curvature relation of FRP reinforced sections, the J-factor is derived and its equivalence to safety factor is demonstrated. Due to the familiarity of designers with the concept of safety factor, it may be more advantageous to use the latter factor instead of the J-factor to comfortably assess the level of safety in FRP reinforced concrete structures.