The strengthening of concrete by applying bonded fiber-reinforced polymer (FRP) jackets has become a popular retrofit technique. Failure of such FRP-wrapped columns is usually governed by rupture of the FRP in the hoop direction. Two common material tests have been used to obtain the hoop strength and rupture strain of FRP composites used in these applications: tensile tests of flat coupons and so-called split-disk tests. The FRP rupture strain obtained from a split-disk test is usually lower than that obtained from a flat coupon test, but there is neither a well-defined relationship between the two results nor a comprehensive explanation for why they should have different values. This paper presents a finite element (FE) analysis of the FRP hoop strains in the split-disk test. The results show that the local strains in an FRP ring in a split-disk test are increased by the geometric discontinuities at the ends of the FRP and circumferential bending of the FRP ring at the gap arisen from the relative moment of the two half disks. The model predicts that the FRP will rupture once the strain at one of the above locations reaches the FRP rupture strain, leading to a lower apparent tensile strength than that obtained from flat coupon tests.