Search

This paper aims at developing a pore-scale numerical model for non-Darcy fluid flow through rough-walled fractures. A simple general relationship between the local hydraulic conductivity and the flow velocity is proposed. A new governing equation for non-Darcy fluid flow through rough-walled fractures is then derived by introducing this relationship into the Reynolds equation. Based on the non-linear finite element method, a self-developed code is used to simulate the non-Darcy fluid flow through fractures. It is found that the macroscopic results obtained by the numerical simulation agree well with the experimental results. Furthermore, some interesting experimental observations can be reproduced. [ABSTRACT FROM AUTHOR]

This paper introduces a numerical simulation tool using the Finite Element Method (FEM) for near-surface mounted (NSM) strengthening technique using fibre reinforced polymers (FRP) applied to concrete elements. In order to properly simulate the structural behaviour of NSM FRP systems there are three materials (concrete, FRP and the adhesive that binds them) and two interfaces (FRP/adhesive and adhesive/concrete) that shall be considered. This work presents the major details of a discontinuous-based constitutive model which aims at simulating NSM FRP interfaces implemented in the FEMIX FEM software. This constitutive model was adapted from one available in the literature, originally employed for fracture simulation in meso-scale analyses of quasi-brittle materials, which is based on the classical Flow Theory of Plasticity combined with fracture mechanics concepts. The most important features of the implemented constitutive model are the consideration of both fracture modes I and II and the possibility of performing 2D and 3D analysis. In the end, results based on FEM simulations are presented with the aim of investigating the soundness and accuracy of the constitutive model to simulate NSM FRP systems’ interfaces. [ABSTRACT FROM AUTHOR]

In this paper, we present an extension of the Stable Generalized FEM (SGFEM) for 3-D fracture mechanics problems. Numerical experiments show that the use of available singular enrichment bases derived from the 2-D asymptotic crack tip solution leads to a severe loss of accuracy in the SGFEM. An enrichment scheme based on singular bases and linear polynomials is shown to recover the optimal convergence of the SGFEM. The proposed SGFEM for 3-D fractures delivers the same rate of growth in condition number as the standard FEM for proper choice of singular enrichment functions. The accuracy and conditioning obtained with the SGFEM is compared with the Generalized FEM (GFEM) for different types of singular enrichment bases. A fully 3-D fracture mechanics problem is considered to highlight issues that arise only in 3-D problems. The convergence of Stress Intensity Factors (SIFs) extracted from GFEM and SGFEM solutions and the effect of the size of enrichment sub-domains on the accuracy of extracted SIFs are also studied. It is shown that the accuracy of SIFs may deteriorate with mesh refinement when the topological enrichment strategy is adopted. The proposed SGFEM delivers much better accuracy than the GFEM for both geometrical and topological enrichment strategies. [ABSTRACT FROM AUTHOR]