Localized Failure in Fiber-Reinforced Polymer-Wrapped Cylindrical Concrete Columns

Localization of deformation in fiber-reinforced polymer (FRP) confined, axially loaded, concrete columns and the effect of confining pressure on the arrest of localization is investigated. The effect of confining pressure on failure loads is found to be strongly nonlinear with the confinement pressure required to exceed a threshold value to arrest shear band growth and lead to a significant gain in failure loads. Second, the nature of the interfacial bond between concrete and FRP is found to influence the gain in column strength. Assuming a tied interface may significantly overestimate the confining pressure acting on the concrete. For a more realistic cohesively bonded interface, however, the gain in column strength is shown to depend on the stiffness of the interfacial bond between concrete and FRP, up to a limiting value. Explanations are offered for the aforementioned observations based on an analysis of the stress state and the kinematics of the bond.