Three-Dimensional finite-element analysis of FRP-Confined circular concrete columns under eccentric loading

Fiber-reinforced polymer (FRP) jacketing/wrapping has become a widely accepted technique for strengthening/retrofitting reinforced concrete (RC) columns. Although extensive research has been conducted on FRP-confined concrete columns under concentric compression, leading to many stress-strain models, the applicability of these concentric-loading models in the analysis of columns under eccentric loading has not been properly clarified. This paper presents the development and application of a reliable three-dimensional (3D) finite element (FE) approach for an in-depth investigation into this problem. In the proposed FE approach, an accurate plastic-damage model recently developed by the authors' group for concrete under a general state of multiaxial compression is employed. The accuracy of the proposed FE approach is demonstrated through comparisons with available tests. Numerical results from the verified FE approach are then presented to gain an improved understanding of the behavior of confined concrete in such columns (e.g., distributions of axial stresses and confining pressures), leading to the conclusion that the direct use of a concentric-loading stress-strain model in the analysis of an eccentrically-loaded column may lead to significant errors.