Indicative performance of fiber reinforced polymer (FRP) encased beam in flexure

Fiber reinforced polymer (FRP) is an ideal reinforcing material for marine structures because of its chemical stability. It is normally used in rod form to substitute the conventional steel bars in marine structures. However, the FRP bar reinforced concrete structure tends to fail with limited ductility. Thus, the safety of its application is greatly affected. This study aimed to enhance the ductility of FRP reinforced structure by proposing a novel FRP encased beam design. Structural behaviors of different encased beams were studied under four point flexural loading. Four types of encased beams were tested, namely, the plain FRP I-beam, the FRP I-beam with studs, the FRP I-beam with links and studs, and the FRP I-beam with studs and Barchip fiber. The results suggested that the FRP in the I-beam form could enhance the ductility performance of the FRP reinforced concrete beam, to a level that satisfies the ductility requirements as stated in the Canadian Highway Bridge Design Code, i.e. ductility index should exceed 4.0. However, shear studs should have to install on the FRP I-beam and this is also useful in preventing bond slip problem. Addition of Barchip fibers in the mixing concrete could further enhance the first crack load by 25.4%, while addition of stirrups enhanced the ultimate load carrying capacity by another 18.2%. However, both of these methods were not recommended since they would reduce the ductility of the beam, as opposed to the primary objective of the proposed design.