A novel hybrid member made from two kinds of composite materials, ductile engineered cementitious composite (ECC) as the core material and linear elastic fiber-reinforced polymer (FRP) as the confining material was proposed for application. A series of axial compressive experiments on FRP-confined ECC cylinders were carried out. The test results indicated that FRP-confined ECC specimens exhibited similar compression hardening behavior in the axial stress-strain curve to FRP-confined normal concrete specimens. Moreover, the “self-confinement” effect of ECC and the confinement stiffness of FRP had significant influence on the stress-strain response and failure mode. Based on the FRP strain distribution, a failure mechanism was proposed for FRP-confined cement-based materials under compression. FRP-confined ECC cylinders underwent three distinct stages under compression: formation of microcracks, formation of multiple cracks, and formation and propagation of major cracks. A qualitative model for FRP confined ECC was developed, which illustrates the effects of different tensile properties of cement-based materials on the failure mode and explains why the hoop rupture strain is lower than the ultimate tensile strain of FRP. In addition, fitting equations were proposed for predicting the compressive strength and ultimate strain of FRP-confined ECC cylinders at the ultimate state.
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