JOURNALS

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• Development of an adaptive mesh generator

  J. Olausson, J. Gustafsson, D. Capua, E. Oñate

  (2002). Research Report, Nº PI211

  
  

  Abstract

  This study thoroughly explains the process of implementing Adaptive Mesh Refinement into a Finite Element Analysis program. Using the error norm, a routine for improving an original mesh for an arbitrary 2D structural problem has been developed. By utilizing user-defined relative global error, an optimal mesh for a given level of approximation can be obtained in an iterative manner. The routine (called AMG v1.0) runs with the pre-/postprocessor GiD and the calculation module Calsef, but can easily be tailored to work with other FEA programs. AMG operates with two mesh optimality criteria, which have proven to refine the mesh in a non-oscillatory manner. The open structure, along with the Graphical User Interface, makes AMG suitable for educational and experimental purposes. For validation, six examples within the field of structural engineering have been solved, four of which have been compared favorably with analytical solutions. The mesh optimality routines used are general, why AMG can be extended to handle more types of elements, 3D analysis, and to be applicable to other types of engineering problems. Above all AMG serves as a first step of implementing Adaptive Mesh Refinement procedures into GiD.

  Abstract
  This study thoroughly explains the process of implementing Adaptive Mesh Refinement into a Finite Element Analysis program. Using the error norm, a routine for improving an [...]

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• Cálculo de estructuras con materiales compuestos laminados por el método de elementos finitos

  E. Oñate

  (2002). Research Report, Nº PI212

  
  

  Abstract

   La utilización de materiales compuestos laminados en estructuras es creciente en todos los ámbitos de la ingeniería. El cálculo de esas estructuras requiere tener en cuenta las características de dichos materiales, tanto en cuanto a sus propiedades mecánicas, generalmente ortótropas, como a la peculiaridad de su distribución en capas laminares. Un caso particular de interés práctico de ese tipo de estructuras mixtas de hormigón y acero, e incluso las estructuras de hormigón armado en las que el hormigón y las armaduras se asimilan a capas de materiales con propiedades diferentes. En este capítulo presentamos una panorámica del cálculo por el método de elementos finitos de estructuras formadas por materiales compuestos laminados. Iniciaremos el capítulo con una introducción al cálculo de vigas planas formadas por un apilamiento de capas utilizando elementos de viga de Timoshenko de dos nodos. Tras ello estudiaremos las placas multilaminadas mediante elementos de Reissner-Mindlin, para terminar con el análisis de láminas de forma arbitraria y de revolución utilizando elementos finitos multilaminados planos y troncocónicos respectivamente, basados también en la teoría de Reissner-Mindlin.    

  Abstract
   La utilización de materiales compuestos laminados en estructuras es creciente en todos los ámbitos de la ingeniería. El cálculo de esas estructuras [...]

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• Volumetric constraint models for anisotropic elastic solids

  C. Felippa, E. Oñate

  (2002). Research Report, Nº PI216

  
  

  Abstract

  We study three “incompressibility flavors” of linearly-elastic anisotropic solids that exhibit volumetric constraints: isochoric, hydroisochoric and rigidtropic. An isochoric material deforms without volume change under any stress system. An hydroisochoric material does so under hydrostatic stress. A rigidtropic material undergoes zero deformations under a certain stress pattern. Whereas the three models coalesce for isotropic materials, important differences appear for anisotropic behavior. We find that isochoric and hydroisochoric models under certain conditions may be hampered by unstable physical behavior. Rigidtropic models can represent semistable physical materials of arbitrary anisotropy while including isochoric and hydroisochoric behavior as special cases.

  Abstract
  We study three “incompressibility flavors” of linearly-elastic anisotropic solids that exhibit volumetric constraints: isochoric, hydroisochoric and rigidtropic. [...]

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• A finite element formulation for the geometrically non linear analysis of shells

  E. Oñate, J. Oliver

  (1986). Finite element methods for plate and shell structures, T.J.R. Hughes, E. Hinton (Ed.) Pineridge Press, Vol. 2: Formulations and algorithms, pp. 83-101

  
  

  Abstract

  A finite element formulation for the analysis of geometrically nonlinear shell problems is presented. Degenerated 3D elasticity elements are used for the finite element discretization of the shell. Large rotation effects are taken into account in the nonlinear large displacement kinematic description. The shell formulation is derived in detail using a Total Lagrangian approach and explicit forms of the relevant finite element matrices are given. In the last part of the chapter the obtention of the alternative Updated Lagrangian formulation is presented.

  Abstract
  A finite element formulation for the analysis of geometrically nonlinear shell problems is presented. Degenerated 3D elasticity elements are used for the finite element discretization [...]

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• A simple method for automatic adaption of finite element meshes to changes in the boundary shape

  G. Chiandussi, G. Bugeda, E. Oñate

  (2001). Innovative Tools for Scientific Computation in Aeronautical Engineering, J. Periaux, P. Joly, O. Pironneau and E. Oñate (Eds.), pp. 149-167, CIMNE, Barcelona, Spain

  
  

  Abstract

  A simple method to automatically update the finite element mesh of the analysis domain is proposed for cases when the shape of the domain in modified. The method considers the mesh as a fictitious elastic body subjected to prescribed displacement at selected boundary points. The mechanical properties of each mesh element are appropriately selected in order to minimize the deformation and the distortion of the mesh elements. Different selection strategies have been used of remeshing in the solution of shape optimization problems and reduces the number of the remeshing step in the solution of coupled fluid-structure interaction problems

  Abstract
  A simple method to automatically update the finite element mesh of the analysis domain is proposed for cases when the shape of the domain in modified. The method considers [...]

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• Fractura elastoplástica: Modelos elastoplásticos para la simulación numérica de procesos de fractura

  J. Oliver, S. Oller, E. Oñate

  (1988). Métodos Numéricos Aplicados a la Mecánica de Fractura, J. Oliver et al (Eds.), CIMNE, Barcelona, pp. 27-60

  
  

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• A finite element formulation for the geometrically non linear analysis of shells using a total lagrangian approach

  J. Oliver, E. Oñate

  (1988). Computational Methods for Non Linear Problems, C. Taylor (Ed.) Pineridge Press, pp. 29-55

  
  

  Abstract

  A total Lagrangian formulation for the large displacement large rotation: analysis of shells using finite elements is presented. Different expressions for the strain matrix obtained using various displacement interpolation forms are discussed and details of the obtention of the tangent stiffness matrix are given. Simplifications of the general 3D shell formulation for 2D shells are also presented together with some examples of applications.

  Abstract
  A total Lagrangian formulation for the large displacement large rotation: analysis of shells using finite elements is presented. Different expressions for the strain matrix [...]

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• Mindlin finite strip and axisymmetric finite element shell analysis

  E. Oñate, B. Suárez, E. Hinton

  (1984). Finite Elements Software for Plates and Shells, Hinton E. y Owen D.R.J. (Eds.), Pineridge Press, 1984

  
  

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• Stress, strain and energy splittings for anisotropic elastic solids under volumetric constraints

  C. Felippa, E. Oñate

  (2002). Research Report, Nº PI217

  
  

  Abstract

  We define stress and strain splittings appropriate to linearly elastic anisotropic materials with volumetric constraints. The treatment includes rigidtropic materials, which develop no strains under a stress pattern that is a null eigenvector of the compliance matrix. This model includes as special case incompressible materials, for which the eigenvector is hydrostatic stress. The main finding is that pressure and volumetric strain must be redefined as effective quantities. Using this idea, an energy decomposition that exactly separates deviatoric and volumetric energy follows.

  Abstract
  We define stress and strain splittings appropriate to linearly elastic anisotropic materials with volumetric constraints. The treatment includes rigidtropic materials, [...]

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• Posibilidades de las nuevas tecnologías de información y comunicaciones en el sector de la construcción

  E. Oñate, J. Marcipar, F. Zárate

  (2003). Research Report, Nº PI221

  
  

  Abstract

  Se presenta una breve panorámica de las posibilidades de las nuevas Tecnologías de la Información y las Comunicaciones en el sector de la construcción. Tras unas reflexiones sobre el valor intrínseco de la información y las comunicaciones, se describe el impacto que está teniendo Internet en los nuevos métodos de trabajo, de comercio, de formación y, en general, de intercambio de información a todos los niveles en las actividades de los técnicos del sector de la construcción. Finalmente se especula sobre las posibilidades de las TIC para generar entornos de trabajo inteligentes que generen y gestionen conocimiento para la solución de problemas prácticos.

  Abstract
  Se presenta una breve panorámica de las posibilidades de las nuevas Tecnologías de la Información y las Comunicaciones en el sector de la construcción. [...]

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