Reliability of Fiber-Reinforced Polymer-Confined Reinforced Concrete Columns

Abstract

Fiber-reinforced polymer (FRP) composite jackets are increasingly used for strengthening and retrofit of reinforced concrete columns. The jackets provide lateral confinement to concrete that enhances strength and ductility of the columns. There are a number of existing empirical models that predict an increase in compressive strength and the maximum axial strain of FRP-confined concrete. Comparison with available experimental data indicates a large degree of uncertainty associated with these models. In the paper this uncertainty is estimated and then taken into account in a reliability analysis of FRP-confined columns. Only short columns with circular cross sections under static loads are considered. Based on results of the reliability analysis tentative recommendations are presented on how to modify the strength reduction factor for the design of FRP-confined columns in order to ensure for them the same level of reliability as for conventional unconfined columns. A relationship between the strength reduction factor and the confinement ratio is proposed for FRP-confined columns in axial compression and axial compression with flexure. The influence of reinforcement ratio, live-to-dead load ratio, and eccentricity ratio on reliability of FRP-confined columns is also investigated.