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.

Fiber reinforced polymer (FRP) jacketing of reinforced concrete (RC) columns is now a widely accepted strengthening/retrofit technique. The extensive existing research conducted on concrete in FRP-confined RC columns has led to a large number of stress-strain models, but most of these models are applicable only to FRP-confined RC columns with limited transverse steel reinforcement (i.e., steel hoops or spirals). In many RC columns such as those designed following modern design standards, the transverse steel reinforcement may provide significant confinement which needs to be accounted for in design. This paper presents an analysis-oriented stress-strain model for concrete in such columns where the concrete is under combined confinement from the FRP jacket and the transverse steel reinforcement (i.e., FRP-steel-confined concrete). Two alternative versions of the proposed model are proposed to cater for different considerations. Both versions of the proposed model are shown to provide accurate predictions of existing test results and to be superior to the existing models of the same type.Department of Civil and Environmental Engineerin