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• Simulación del choque de vehículos por el método de los elementos finitos. Programa "SIMPACT"

  J. Rojek, E. Oñate, J. Canet

  (1995). Research Report, Nº PI71

  
  

  Abstract

  En este trabajo se presentan las principales características del programa de ordenador “SIMPACT” desarrollado en el Centro Internacional de Métodos Numéricos en Ingeniería de Barcelona para la simulación numérica de problemas de impacto y choque de vehículos. El programa se basa en una formulación de elementos finitos de lámina no lineal incorporando también elementos de sólido y de viga para modelar correctamente todos los componentes resistente típicos de estructuras de vehículos. El programa permite la utilización de algoritmos de integración en el tiempo explícitos incluyendo además modelos constitutivos para materiales compuestos. Los ejemplos que se presentan muestran la aplicación del programa a la deformación de una puerta sometida a un ensayo penetración lateral, el choque frontal de un prototipo de vehículo industrial, y el vuelco de una cabina de autobús.

  Abstract
  En este trabajo se presentan las principales características del programa de ordenador “SIMPACT” desarrollado en el Centro Internacional de Métodos [...]

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• Análisis de procesos de conformado de metales por el método de los elementos finitos. Posibilidades y perspectivas.

  E. Oñate

  (1995). Research Report, Nº PI72

  
  

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• Structural analysis and durability assessment of historical construction using a finite element damage model

  E. Oñate, A. Hanganu, A. Barbat, S. Oller, R. Vitaliani, A. Saetta, R. Scotta

  (1995). Research Report, Nº PI73

  
  

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• Moving least square approximations for solution of differential equations

  R. Taylor, O. Zienkiewicz, E. Oñate

  (1995). Research Report, Nº PI74

  
  

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• A rate-dependent isotropic damage model for the seismic analysis of concrete dams

  M. Cervera, J. Oliver, O. Manzoli

  (1995). Research Report, Nº PI76

  
  

  Abstract

  In this paper a rate‐dependent isotropic damage model developed for the numerical analysis of concrete dams subjected to seismic excitation is presented. The model is shown to incorporate two features essential for seismic analysis: stiffness degradation and stiffness recovery upon load reversals and strain‐rate sensitivity. The issue of mesh objectivity is addressed using the concept of the ‘characteristic length’ of the fracture zone, to show that both the softening modulus and the fluidity parameter must depend on it to provide consistent results as the computational mesh is refined. Some aspects of the numerical implementation of the model are also treated, to show that the model can be easily incorporated in any standard non‐linear finite element code. The application of the proposed model to the seismic analysis of a large gravity concrete dam shows that the structural response may vary significantly in terms of the development of damage. The inclusion of rate sensitivity is able to reproduce the experimental observation that the tensile peak strength of concrete can be increased up to 50 percent for the range of strain rates that appear in a structural safety analysis of a dam subjected to severe seismic actions.

  Abstract
  In this paper a rate‐dependent isotropic damage model developed for the numerical analysis of concrete dams subjected to seismic excitation is presented. The model is shown [...]

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• Viscous damage model for Timoshenko beam structures

  A. Barbat, S. Oller, E. Oñate, A. Hanganu

  (1995). Research Report, Nº PI77

  
  

  Abstract

  A local damage constitutive model based on Kachanov’s theory is used within a finite element frame and applied to the case of 2D and 3D Timoshenko beam elements. The model takes into account viscous effects, thus allowing damping to be considered in a rigorous way. A damage index based on potential energy criteria, useful in evaluating the behaviour of structures or of parts of structures, is proposed. The procedure is applied to estimate the damage produced by seismic actions in reinforced concrete building structures, whose response is computed by using a non-linear Newmark-type incremental time integration scheme. Three numerical examples are included; one of them compares results obtained by using the proposed model with results of a laboratory test.

  Abstract
  A local damage constitutive model based on Kachanov’s theory is used within a finite element frame and applied to the case of 2D and 3D Timoshenko beam elements. The [...]

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• Alguns aspectos da simulação numérica pelo método dos elementos finitos da estampagem de chapas finas

  E. Casas

  (1995). Research Report, Nº PI78

  
  

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• The energy input spectrum scaling laws and synthetic compatible records

  J. Hurtado, A. Barbat

  (1995). Research Report, Nº PI79

  
  

  Abstract

  A method for predicting the seismic energy input spectrum is presented. The method is based on the analytical relationship linking this spectrum and other measures of earthquake energy such as power spectrum and Arias intensity, and the results of the statistical analysis made on 120 strong motion records. Upon the same relationships, a method for simulating artificial accelerograms compatible with a prescribed energy input spectrum is also developed. This procedure is used for the calculation of damage indexes for reinforced concrete single-degree-of freedom-systems, corresponding to types of energy input spectra and different ground motion durations.  

  Abstract
  A method for predicting the seismic energy input spectrum is presented. The method is based on the analytical relationship linking this spectrum and other measures of earthquake [...]

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• On the stabilization of numerical solution for advective-diffusive transport and fluid flow problems

  E. Oñate

  (1996). Research Report, Nº PI81

  
  

  Abstract

  The concept of the so called “artificial or balancing diffusion” used to stabilize the numerical solution of advective diffusive transport and fluid flow problems is revised in this paper. It is shown that the standard forms of the balancing diffusion terms, usually chosen in a heuristic manner, can be naturally found by introducing higher order approximations in the derivation of the governing differential equations via standard conservation (or equilibrium) principles. This allows us to reinterprete many stabilization algorithms and concepts used in every day practice by numerical analysts and also provides an expression for computing the stabilization parameter.

  Abstract
  The concept of the so called “artificial or balancing diffusion” used to stabilize the numerical solution of advective diffusive transport and fluid flow [...]

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• Comparing two algorithms to add large strains to a small strain finite element code

  A. Rodríguez-Ferran, A. Huerta

  (1996). Research Report, Nº PI91

  
  

  Abstract

  Two algorithms for the stress update (i.e., time-integration of the constitutive equation) in large strain solid mechanics are discussed, with particular emphasis on two issues: the incremental objectivity and the implementation aspects. It is shown that both algorithms are incrementally objective (i.e., they treat rigid rotations properly) and that they can be employed to add large strain capabilities to a small large deformation paths (rigid rotation, simple shear, extension, extension and compression, dilatation, extension and rotation), have been used to test and compare the two algorithms, both for elastic and plastic analysis. These test evidence different time integration accuracy for each algorithm. However, it is demonstrated that the, in general, less accurate algorithm gives exact results for shear-free deformation paths.  

  Abstract
  Two algorithms for the stress update (i.e., time-integration of the constitutive equation) in large strain solid mechanics are discussed, with particular emphasis on two issues: [...]

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