A unified generic RC model for FRP plating: Intermediate crack theory

Abstract

There has been much very good research on the use of FRP as: internal bar reinforcement; adhesively bonded reinforcement on or in the surface such as externally bonded plates or near surface mounted plates; as wrapping or encasement for confinement; and as fibres in concrete. In particular, the study of the bond of adhesively bonded FRP with the concrete which is often referred to as intermediate crack debonding. However, there has always been and still remains a great difficulty in applying this FRP research to the main body of reinforced concrete design. It will be shown in this paper that this difficulty is not the fault of the FRP research community but of the lack of progress by the steel reinforced concrete research community because there are large elements of steel reinforced concrete behaviour that are little understood. A unified reinforced concrete model that is perfectly suited for FRP reinforcement as well as all types of reinforcement is described. It will be shown that this same model can simulate with the help of FRP intermediate crack debonding research the apparently disparate behaviours of: deflection due to cracking; moment rotation and the subsequent ability to redistribute moment and absorb energy; the shear resistance; confinement for members with or without FRP reinforcement or wrap; and the effect of synthetic fibres in concrete on tension and compression. This unified model will allow the effect of FRP reinforcement, wrap and fibres to be quantified much more rapidly to produce structural mechanics based design approaches for FRP and consequently allow rapid expansion of the use of FRP in reinforced concrete structures.