Reinforcement Characteristics of Prestressed Concrete Beams with Fiber-reinforced Polymer (frp) Tendons

The basic advantages of fiber-reinforced polymer (FRP) reinforcement are reviewed. FRP tendons exhibit linear elastic response to rupture without yielding and thus failure is expected to be brittle. Structural beahaviour of beams prestressed with FRP tendons is different from that of beams with traditional steel reinforcement. Strength design approach for prestressed beams with FRP tendons is based on the concept of brittle ratio, reinforcement ratio at which concrete fails in compression at the same time as FRP tendon ruptures. Depending on reinforcement ratio, the flexural behaviour of the beam can be devided into several groups. If reinfrocement ratio is equal to brittle ratio, beams fail by rupture of tendons and crushing of concrete simultaneously. Beams with reinforcement ratio, less than brittle ratio, are under-reinforced and will fail by rupture of tendons. When reinforcement ratio is greater than brittle ratio, concrete fails in compresion prior to rupture of tendons. Brittle ratio was calculated by different expressions proposed in scietific literature, and particular results were given. It has been shown, that brittle ratio is influenced by the mechanical properties of FRP and concrete.