Confinement Model for Concrete Columns Internally Confined with Carbon FRP Spirals and Hoops

Abstract

Recent years have seen valuable research work and widespread applications of fiber-reinforced polymer (FRP) bars as flexural and shear reinforcement for concrete structures. Nonetheless, the axial compression behavior of FRP reinforced concrete (RC) columns has not yet been defined. This study introduces equations and a confinement model to predict the stress-strain envelope responses of RC columns reinforced with carbon-FRP bars (CFRP) and confined by CFRP spirals or hoops. The model takes into account the effect of many parameters such as transverse reinforcement configuration, longitudinal reinforcement ratio, volumetric ratio, and the size and spacing of spirals or hoops. Results of analysis using the proposed confinement model were verified by means of a series of experiments with full-scale circular CFRP-RC columns. The proposed equations have been shown to predict accurately confined concrete core stress, corresponding concrete strain, and prepeak and postpeak stress-strain relationships for the tested CFRP-RC column specimens.