Finite Element Modeling of Carbon Fiber-Reinforced Polymer Reinforced Concrete Beams under Elevated Temperatures

The paper presents details of a three-dimensional finite element (FE) model for the prediction of response of reinforced concrete (RC) beams under an elevated temperature regime. The beams were reinforced with either steel or fiber-reinforced polymer (FRP) bars. Crack formation and propagation were modeled with the help of smeared cracks. Changes in the material properties of both concrete and reinforcing bars at high temperatures have been considered. Constitutive models for the temperature-dependent material properties of carbon FRP (CFRP) bars and thermal expansion coefficients for both concrete and steel have been proposed. The effects of tension softening and stiffening have been included in the model. Excellent convergence and numerical stability of the formulation was found. The models showed good agreement with the recorded data of temperature and beam strength and stiffness. Analytical concrete stress distribution is compared in steel and FRP reinforced beams and differences are discussed.