Simulating the Behavior of FRP-Confined Cylinders Using the Shear-Friction Mechanism

The axial compressive behavior of concrete confined with fiber reinforced polymer (FRP) has received much attention over the past two and a half decades, with over 90 empirical and semiempirical models developed to predict the compressive stress strain behavior. While there is no doubt that in general these models show a good correlation to the dataset from which they were derived, when applied to a global dataset, accuracy is reduced. In response to the largely empirical analysis approaches, which should only be applied within the bounds from which they were developed, a new, mechanics-based approach for predicting the axial and lateral stress-strain relationships of concentrically loaded FRP-confined cylinders is presented. The approach uses shear-friction theory to simulate the formation and displacement of sliding planes as concrete softens. It is shown that cylinders can fail through two shear-friction mechanisms, namely, through either the formation of a circumferential wedge, or, a single sliding plane. Importantly, from this is shown that although each mechanism is defined by the same shear-friction material properties different stress-strain relationships result and this may explain some of the scatter of test results. In this paper, the mechanism of a single sliding plane is derived and compared with that of a circumferential wedge. (C) 2015 American Society of Civil Engineers.