Effects of confining stiffness and rupture strain on performance of FRP confined concrete

FRP (fiber reinforced polymer) confinement has been proven to be effective in enhancing the structural performance of concrete columns. However, the effectiveness of FRP confinement is dependent on various structural parameters, including the concrete strength, FRP confining stiffness and FRP rupture strain, and is not easy to predict as revealed by the large differences in the existing design formulas. Herein, a newly developed axial and lateral stress–strain model is used to evaluate the effects of these parameters on the yield strength/strain, ultimate strength/strain and ductility of FRP confined concrete. The new model is first verified by comparing with test results published in the literature and then used to perform a parametric study, based on which design formulas for estimating the performance of FRP confined concrete are developed. It will be seen at the end that the confining stiffness is more fundamental than the confining stress at rupture and that the rupture strain has independently significant effect on the ultimate strength/strain and ductility.