Constitutive Model of Concrete Simultaneously Confined by FRP and Steel for Finite-Element Analysis of FRP-Confined RC Columns

This paper presents a confined concrete material constitutive model for use in finite-element analysis, which is able to model accurately the combined confinement effect of fiber-reinforced polymers (FRP) and internal steel reinforcement on the structural monotonic, cyclic, and/or dynamic response of reinforced concrete (RC) columns confined with externally wrapped FRP. The proposed material constitutive model for FRP-and-steel confined concrete explicitly models the simultaneous confinement produced by FRP and steel on the core concrete to predict the combined effect on the structural response of circular RC columns. This modified material model is combined with a force-based frame element to predict numerically the load-carrying capacity of FRP-confined RC columns subjected to different loading conditions. Numerical simulations are compared to experimental test data available in the literature and published by different authors. The numerically simulated responses agree very well with the corresponding experimental results. The proposed model is found to predict the ultimate load for FRP-confined RC circular columns with better accuracy than models that do not consider the simultaneous confinement effects on FRP and steel, particularly for columns subjected to concentric axial loads. (c) 2018 American Society of Civil Engineers.