Fundamental issues that govern the rotation of FRP retrofitted RC columns and beams: The intractable plastic hinge ductility problem

Abstract

There is often a perception that FRP retrofitted concrete structures are unable to redistribute stress resultants nor absorb energy due to a lack of rotational capacity because FRP is a brittle material and the interface bond between the FRP plate and concrete is also brittle. However in contrast to this perception, there is clear experimental evidence to show that FRP plating techniques can produce ductile members. Hence, it should be possible to develop ductility design rules for FRP strengthened reinforced concrete structures to considerably widen the application of FRP plating which is the subject of this paper. It is shown that the major problem is not in quantifying the rotational limit due to FRP plate debonding or fracture but in quantifying the rotational limit due to concrete softening which has been an intractable problem for over fifty years.