FRP-confined concrete under axial cyclic compression

One important application of fiber reinforced polymer (FRP) composites in construction is as FRP jackets to confine concrete in the seismic retrofit of reinforced concrete (RC) structures, as FRP confinement can enhance both the compressive strength and ultimate strain of concrete. For the safe and economic design of FRP jackets, the stress–strain behavior of FRP-confined concrete under cyclic compression needs to be properly understood and modeled. This paper presents the results of an experimental study on the behavior of FRP-confined concrete under cyclic compression. Test results obtained from CFRP-wrapped concrete cylinders are presented and examined, which allows a number of significant conclusions to be drawn, including the existence of an envelope curve and the cumulative effect of loading cycles. The results are also compared with two existing stress–strain models for FRP-confined concrete, one for monotonic loading and another one for cyclic loading. The monotonic stress–strain model of Lam and Teng is shown to be able to provide accurate predictions of the envelope curve, but the only existing cyclic stress–strain model is shown to require improvement.