RESUMOEste artigo apresenta um modelo numérico para simulação do processo de fissuração em meios parcialmente frágeis. A análise fisicamente não linear se inicia empregando-se o Método dos Elementos Finitos Padrão -MEF, com o qual se simula a degradação inicial do meio de forma distribuída por meio de modelos constitutivos que consideram que o meio, apesar de degradado, permanece contínuo. O estágio limiar de nucleação de fissuras é indicado pela singularidade do tensor acústico, característica que fornece a condição clássica de localização de deformações. A presença das trincas é simulada com método cinemático que incorpora as descontinuidades por meio de interpolações enriquecidas, com base no Método dos Elementos Finitos Generalizados -MEFG, ao passo que a propagação destas trincas é também indicada pela singularidade do tensor acústico. As forças de coesão atuantes nos planos das trincas são simuladas ao se incorporar ao processo de enriquecimento um modelo constitutivo discreto, que consiste na relação entre tensões e deslocamentos no caminho da trinca e baseia-se no conceito de fissura coesiva. Este modelo apresenta a vantagem da não necessidade de definição prévia da região de nucleação e do caminho da trinca ou de redefinição da malha durante o processamento. As implementações foram realizadas na plataforma INSANE -Interactive Structural ANalysis Environment. Palavras-chave: processo de fissuração, degradação distribuída, nucleação de fissuras, MEFG, propagação de trincas. ABSTRACTThis paper presents a numerical model for simulation of cracking process in quasi-brittle medium. The physically nonlinear analysis begins using the Standard Finite Element Method -FEM, through which the initial medium degradation is simulated in a distributed manner employing constitutive models that consider the medium, even though degraded, remains continuous. The threshold stage of cracks nucleation is indicated by singularity of the acoustic tensor, which provides the classical strain localization condition. The presence of cracks is simulated through kinematic method that incorporates the discontinuities by using enriched interpolations based on the Generalized Finite Element Method -GFEM, whereas the cracks propagation is also indicated by singularity of the acoustic tensor. The cohesive forces acting on the crack plane are simulated incorporating to the enrichment process a discrete constitutive model, which is the relationship between stresses and displacements in the crack path and is based on the concept of cohesive crack. This model has the advantage of not having to pre-set nucleation region and crack path nor having to redefine the mesh during processing. The implementations have been performed on the INSANE -Interactive Structural ANalysis Environment platform.

No abstract

The development of numerical and computational resources that can present reliable models for the analysis of reinforced concrete structures is mainly driven by its widespread use. Considering that reinforced concrete is a composite material and bond is the load-carrying mechanism, these models must consider that the structural behavior is affected by the interaction between concrete and reinforcement. On this basis, the Finite Element Method (FEM) is a well-established method able to provide consistent results for reinforced concrete modeling through reinforcement and bond models. Nevertheless, to simplify the analysis, the hypothesis of strain compatibility between concrete and reinforcement is usually considered. Under certain loads and specific geometries, this hypothesis is not valid, and the bond-slip phenomenon must be considered to fully characterize the structural behavior. To fulfill this need, this paper presents a graphic interface that enables the modeling of reinforced concrete structures through discrete and embedded reinforcement models, with the possibility to include the bond-slip phenomenon based on several constitutive laws proposed in the literature. The computational implementations were held in the INSANE (INteractive Structural ANalysis Environment), an open-source software based on the Object-Oriented Programming paradigm, which enclosures several constitutive models for nonlinear concrete modeling and different numerical techniques, and a post-processing application able to represent the results by way of a friendly-user graphic interface.