Behavior of FRP jacketed concrete columns under eccentric loading

This paper describes a study on the behavior of fiber-reinforced polymer (FRP) jacketed square concrete columns subjected to eccentric loading. The effect of strain gradient on the behavior of concrete columns confined by the FRP jacket was investigated through experimental and numerical analysis methods. Nine (108 x 108 x 305 mm) square concrete column stubs with zero, one, and two plies of unidirectional carbon FRP fabric were tested under axial compressive loading. In addition to the FRP jacket thickness, the effects of various eccentricities were examined. The nonlinear finite-element analysis results were compared and validated against the experimental test results. The results show that the FRP jacket can greatly enhance the strength and ductility of concrete columns under eccentric loading and that the strain gradient reduces the retrofit efficiency of the FRP jacket for concrete columns. Therefore, a smaller enhancement factor should be used in designing FRP-jacketed columns under eccentric loading. Furthermore, the nonlinear finite-element models established in this study can be used as templates for future research work on FRP-confined concrete columns.