Identification of the failure modes of CFRP shear-strengthened reinforced concrete beams by the finite element method

Abstract The rehabilitation and strengthening of concrete structures using carbon fiber reinforced polymers (CFRP) has become an interesting alternative for a series of important aspects. This material has a low specific weight, high tensile strength, corrosion and fatigue resistance, a high modulus of elasticity, and is a versatile material, with ease and speed in its application. Nevertheless, its consideration and design tend to require more sophisticated analyses to evaluate and predict the behavior of the strengthened structural element. For this reason, numerical methods, such as the Finite Element Method (FEM), can be used in such complex analyses to simulate to a high degree the actual performance of the structure. Thus, this work presents computer simulations of reinforced concrete beams shear strengthened with CFRP through the Finite Element Method in a customized ANSYS model. Special attention is given to the bond behavior between the CFRP sheets and the concrete surface of the beams through contact elements and bilinear cohesive zone models, which allowed for the identification of the debonding failure modes. Twenty-one reinforced concrete beams reported in the literature were simulated: twelve simply supported and nine continuous, with and without CFRP shear strengthening. The beams showed failure modes in shear, bending, concrete splitting, and debonding of the strengthening CFRP sheets. The numerical model developed predicted with good accuracy the beams' behavior in terms of load vs. displacement, load vs. strain, as well as their ultimate loads and failure modes. Resumo A crescente necessidade de reabilitar e reforçar estruturas de concreto armado, assim como os problemas apresentados por técnicas de reforço tradicionais, tornou a utilização de polímeros reforçados com fibras de carbono (PRFC) uma alternativa interessante, uma vez que este material apresenta propriedades como baixo peso específico, elevada resistência à tração, à corrosão e à fadiga, alto módulo de elasticidade, assim como versatilidade, facilidade e rapidez de execução. A fim de avaliar e prever o comportamento do PRFC, é necessário realizar uma análise mais aprofundada dos elementos estruturais reforçados com esse material. Para isso, utilizam-se métodos numéricos, como é o caso do método de elementos finitos (MEF), que permite analisar estruturas complexas, bem como realizar análises não lineares de estruturas de concreto armado. Diante disso, o objetivo deste trabalho