1,721,214 research outputs found
A new method for the representation and evolution of three dimensional discontinuity surfaces in XFEM/GFEM
Full text linkThe ability of the extended and generalized finite element methods of modeling discontinuities independent of mesh alignment requires a suitable representation for the discontinuity surfaces. In the present paper a method for constructing level set functions based on vector data and geometric operations in three dimensions is presented. In contrast to classical level set methods, the proposed approach does not require the integration of differential evolution equations, resulting in a particularly simple structure and easy implementatio
Domain and boundary quadrature for enrichment functions in the extended finite element method
No full textOn the elimination of quadrature subcells for discontinuous for in the Extended Finite Element Method
No full textThe introduction of discontinuous/non-differentiable functions in the eXtended Finite-Element Method allows to model discontinuities independent of the mesh structure. However, to compute the stiffness matrix of the elements intersected by the discontinuity, a subdivision of the elements into quadrature subcells aligned with the discontinuity line is commonly adopted. In the paper, it is shown how standard Gauss quadrature can be used in the elements containing the discontinuity without splitting the elements into subcells or introducing any additional approximation. The technique is illustrated and developed in one, two and three dimensions for crack and material discontinuity problem
EQUIVALENT POLYNOMIALS FOR ONE CELL QUADRATURE OF DISCONTINUOUS FUNCTIONS IN THE EXTENDED FEM
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Single domain quadrature techniques for discontinuous and non-linear enrichments in local partition of unity FEM
No full textA unilateral nonlocal tensile damage model for masonry structures
No full textIn the present paper, a constitutive nonlocal damage model is proposed for the non-linear incremental finite element analysis of masonry structures. The mechanical model is based on the assumptions of linear elasticity under compression and softening behaviour under tension, described by the adoption of a unique strain-driven nonlocal damage variable. Specifically, non-locality of the integral type is introduced in order to prevent spurious strain localization. It can be noted that the unilateral nature of the model is suitable to contemplate both diffused macro-cracks induced by the tensile damage process and the stiffness recovery in the transition from tension to compression, considering the anisotropy induced by the damage process as well. This is performed by realizing a decomposition of the strain tensor in its positive and negative components, and accounting for stiffness degradation only along tensile direction. The assumption of a linear elastic behaviour in compression is motivated by the fact that the main interest of the model is represented by investigating the response of masonry structures under service loads, condition in which very low compressive states are usually predominant. Consequently, the number of constitutive parameters is more limited with respect to other models that include a damage criterion also in compression. Finally, the validation of the proposed damage model is carried out with reference to a plane problem, in order to check the capability of the model to treat damage in an anisotropic way as well as the almost null dependence of the results on the discretizatio
Numerical modelling of fiber and steel bar reinforced concrete beams by the bridged crack model
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