RESUMO Na atualidade, a necessidade de reabilitação estrutural tem se tornado cada vez mais frequente. Diversos métodos de reabilitação, desde o advento do concreto, vêm sendo desenvolvidos e aplicados. Como alternativa aos métodos tradicionais de reforço surgiram, recentemente, os polímeros reforçados com fibras, usualmente de carbono (PRFC), denominados materiais compósitos avançados. As vantagens desse material de reforço em relação aos tradicionais são a sua alta resistência e rigidez específica, além de ótima resistência à fadiga e facilidade de aplicação. O objetivo deste estudo é a modelagem unidimensional, por meio do Método dos Elementos Finitos, de vigas biapoiadas de concreto armado sem e com reforço, encontradas na literatura. Os comportamentos mecânicos do concreto e do aço são descritos por modelos constitutivos baseados na teoria da Mecânica do Dano Contínuo, e o PRFC é simulado por um modelo elástico linear. As análises não lineares são efetuadas considerando o método de Comprimento de Arco com o processo iterativo tipo Newton-Raphson. A partir da comparação dos resultados numéricos com os experimentais, a modelagem proposta apresenta potencialidade na análise de estruturas de concreto armado reforçadas com PRFC devido a sua reduzida complexidade e baixo custo computacional. Palavras-chave: Mecânica do Dano, Concreto, Viga, PRFC. ABSTRACT Currently, the need for structural rehabilitation has become ever more frequent. Several rehabilitation methods have been developed and applied since the concrete genesis. As an alternative to traditional methods, a new conception of advanced composite materials for strengthening structures has emerged recently. These composite materials are usually made of carbon fiber reinforced polymer (CFRP). The advantages of such materials as compared to the traditional ones are their high specific strength and stiffness, high corrosion and fatigue resistance, besides the ease to apply. The aim of this study is the one-dimensional modeling, through the Finite Element Method, of reinforced concrete bi-supported beams with and without reinforcement, found in the literature. The mechanical behaviors of concrete and steel are described by constitutive models based on the Continuum Damage Mechanics theory, and CFRP is simulated by a linear elastic model. The nonlinear analyzes are performed using the Arc Length method with Newton-Raphson iterative procedure. From the comparison between the numerical and experimental results, the proposed modeling has potentiality in the analysis of reinforced concrete structures with CFRP, due to its reduced complexity and low computational cost.

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The structural behavior resulting from alkali-aggregate reactions on four-pile caps was numerically studied using software based on the Finite Element Method. The cracking was analyzed in terms of reduction rates in the mechanical properties of the concrete (compressive strength, tensile strength and modulus of elasticity) as a consequence of the expansion induced by the alkali-aggregate reaction (AAR) referred to in the literature. One option for dealing with changes in mechanical properties, reported as influenced by the reactive aggregate type, environmental conditions and stress state, is to directly use the value of the properties of the material tested in the analysis, an approach adopted in the study and implemented in the analysis. From the results found in the analysis program the three main effects of AAR could be better understood: expansion, cracking and degradation of mechanical properties of concrete.

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