Modelagem computacional de vigas de concreto armado reforçado com fibras de aço submetidas a cisalhamento

Abstract

ResumoComputational modeling has become a common activity to Civil Engineering researchers and professionals. Therefore, the knowledge about the mechanical behavior of materials is very important. To correctly model the mechanical behavior of concrete structures subjected to shear stress, it is necessary to determine the shear retention factor that accounts for the friction between the two surfaces of a crack. The objective of this study is to show how the shear retention factor of steel fiber reinforced concrete can be obtained from direct shear tests associated to computational modeling. A concrete matrix with compressive strength of 60 MPa, to which 1% and 2% content of steel fibers were added, was used for the shear tests. The stress-slip relationship was obtained from these tests, and the shear retention factor of the steel fiber reinforced concrete was determined from inverse analysis using the Finite Element Method software DIANA © 8.1.2. Finally, the shear retention factor and the influence of steel fibers on the cracks were validated from the computational modeling of steel fiber reinforced concrete beams subjected to shear available in the literature. Keywords: Shear, Steel Fiber Reinforced Concrete, Computational Modeling.A modelagem computacional cada vez mais se torna parte integrante das atividades dos pesquisadores e profissionais da área de engenharia civil. Para isso, o conhecimento do comportamento mecânico dos materiais é de fundamental importância. No caso das estruturas de concreto submetidas a esforços de cisalhamento, para a correta representação do seu comportamento é necessária a determinação do fator de retenção do cisalhamento. Neste trabalho, procura-se determinar esse fator para concretos reforçados com fibras de aço por meio de ensaios de cisalhamento direto em corpos-de-prova prismáticos associados à modelagem computacional. Foi estudada, em laboratório, uma matriz de concreto com resistência à compressão de 50 MPa, à qual foram adicionadas 1,0% e 2,0% de fibras de aço. A relação tensão versus deslizamento foi determinada experimentalmente, sendo em seguida realizada uma análise inversa dos corpos-de-prova de modo a se determinar o fator de retenção do cisalhamento do concreto reforçado com fibras de aço. Para tanto, foi utilizado o programa comercial de elementos finitos DIANA © 8.1.2. Ao final, o fator de retenção do cisalhamento, bem como a influência das fibras na fissuração, foi validado por meio da modelagem de vigas de concreto armado reforçado com fibras de aço submetidas a esforços de cisalhamento disponíveis na literatura. Aço, Modelagem computacional. Palavras-chave: Cisalhamento, Concreto Reforçado com Fibras de

Computational modeling of plain and steel fiber-reinforced concrete beams without transverse reinforcement

“…The tensile behavior of the steel fiber-reinforced concrete in the V-1-0 beam was represented by a bilinear tension softening diagram, as shown in Figure 9a. The stress and strain values for this diagram were obtained by Araújo et al [5] using an inverse analysis on prismatic specimens under four-point loading, as presented in Table 7. The compressive fracture energy was defined as 100 times the area under the tensile stress-strain curve multiplied by the crack bandwidth, which was adopted as the size of the finite element (10 mm).…”

“…There are several methods for modeling cracking in nonlinear finite element analyses of reinforced concrete, with smeared and discrete approaches being the most common. Araújo et al [5] suggested that the discrete crack model is preferable for structures with few cracks. The discrete crack approach considers a crack to be a geometric discontinuity in the finite element mesh; therefore, it is necessary to define the direction and position of cracks before proceeding with the analysis.…”

“…Several authors have proposed different values for the shear retention factor. For example, Araújo et al [5] used a constant β value of 0.01 when modeling the results of direct shear and bending tests of reinforced concrete beams. The same authors used β values of up to 0.5 for steel fiber-reinforced concrete beams.…”