Finite element analysis of interfacial shear behavior for CFRP flexural-externally strengthened reinforced concrete beams using a modified CZM model

The paper aims to develop a nonlinear finite element (NLFE) model to predict the response of carbon-fiber reinforced polymer (CFRP) flexural-externally strengthened reinforced concrete (RC) beams subjected to a four-point flexural test. The ANSYS (c) code based on the finite element method (FEM) is utilized to model a control RC beam as well as CFRP flexural-externally strengthened RC beams, using data from experimental tests found in the literature. A 3D NLFEA with perfect bonding is conducted alongside with seven cohesive zone material (CZMs) models employed to simulate the behavior of CFRP flexural-externally strengthened RC beams. Among the seven-bond stress-slip models and the perfect bonding model evaluated, it is found that Lu et al.'s bilinear CZM model demonstrates the closest match to the experimental results, predicting an ultimate load with a minimal deviation of 0.50%, making it the most accurate among the CZM models. This comparison highlights the effectiveness of Lu et al.'s bilinear CZM model in simulating the response of CFRP flexural-externally strengthened RC beams. Following this, a parametric study is conducted to analyze the effects of concrete compressive strength, tensile steel reinforcement diameter, length and thickness of the CFRP materials, and elastic modulus of epoxy resin on the behavior of CFRP flexural-externally strengthened RC beams. Also, Lu et al.'s bilinear CZM model is modified. The level of fitness between the modified Lu et al.'s bilinear CZM model and the experimental results is assessed with statistical metrics, including the coefficient of determination, mean, standard deviation, coefficient of variation, and root mean square error, which are equal to 0.996, 0.95, 0.19, 20%, and 1.64, respectively.