Stress-strain model for fiber-reinforced polymer jacketed concrete columns

The stress-strain behavior of fiber-reinforced polymer (FRP) confined concrete columns was experimentally and analytically investigated, with particular emphasis on rectangular column sections. A new design-oriented model of the stress-strain response of FRP confined columns was developed and an experimental study was carried out for deriving the model characteristic parameters. The test variables included the volumetric ratio of the FRP jackets, the aspect ratio of the column Section, and the area of longitudinal and lateral steel reinforcement. It was found that jacketing rectangular column sections with FRP sheets increases their axial strength and ductility. In reinforced concrete columns, the FRP jackets prevent premature failure of the concrete cover and buckling of the steel bars, leading to substantially improved performance. The corresponding improvements become less significant as the aspect ratio of the column section increases. The rate of increase in concrete lateral strain with axial strain is influenced by the stiffness of the FRP jackets and aspect ratio of the column sections. Based on the results of this investigation, the main parameters that control the stress and strain characteristics of FRP-confined rectangular column sections were discussed, and a general design model of the stress-strain response of FRP-confined concrete was generated. The results predicted by the model showed very good agreement with the results of the current experimental program and other test data of FRP-confined circular and rectangular columns reported in the literature.