Axial stress–strain relationship for FRP confined circular and rectangular concrete columns

A general mathematical model is developed to describe the stress–strain (fc–εc) relationship of FRP confined concrete. The relationship is applicable to both circular and rectangular columns, and accounts for the main parameters that influence the stress–strain response. These include the area and material properties of the external FRP wraps, the aspect ratio of rectangular column sections, the corner radius used for FRP application, and the volumetric ratio and configuration of internal transverse steel. The proposed model reproduced accurately experimental results of stress–strain or load–deformation response of circular and rectangular columns. In addition to its importance in evaluating the effect of FRP confinement on the ultimate axial strength of concrete columns, the developed fc–εc relationship can be employed very efficiently and effectively for analyzing the response of FRP confined concrete under different types of load application.