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• A computational model for progressive cracking in large dams due to the swelling of concrete

  M. Cervera, J. Oliver, E. Herrero, E. Oñate

  Engineering Fracture Mechanics (1990). Vol. 35 (1-3), pp. 573-585

  
  

  Abstract

  The paper presents a computational model for the analysis of large concrete gravity dams subjected to severe damage due to internal actions. It has been observed in several operating concrete dams that the combined effects of water intrusion and concrete expansion produce a time-advancing deteriorating process that may endanger the global stability of the construction. The present study was undertaken to simulate numerically the observed phenomena and to enable to predict future developments. Tensile cracking of the concrete is modelled using an elasticfracturing constitutive model. The model is able to simulate in a realistic manner the phenomena of primary and secondary crack initiation, elastic degradation, crack closing and reopening. The triggering of the volumetric expansion due to water intrusion is linked to the onset of cracking at each point, assuming that water enters the dam mostly through the cracks. Temperature and pore-water pressure effects are included using assumed distributions based on available field data. Construction joints are modelled using a frictional joint element, although a “constitutive alternative” is outlined. Close surveillance of the behaviour of a dam that presented this sort of problem was used to calibrate the numerical model and to confirm the obtained results.

  Abstract
  The paper presents a computational model for the analysis of large concrete gravity dams subjected to severe damage due to internal actions. It has been observed in several [...]

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• Numerical aerodynamic analysis of large buildings using a finite element model with application to a telescope building

  R. Codina, C. Morton, E. Oñate, O. Soto

  Int. J. of Num. Meths. for Heat and Fluid Flow (2000). Vol. 10 (5-6), pp. 616-633

  
  

  Abstract

  Presents a numerical strategy for the aerodynamic analysis of large buildings, with an application to the simulation of the air flow within a telescope building. The finite element formulation is presented first, and then the methodology followed to obtain significant data from the calculations is described. The quality of the ventilation of the building is defined by the average residence times, and the feasibility of this ventilation by the actions created on the instruments and the general flow pattern.

  Abstract
  Presents a numerical strategy for the aerodynamic analysis of large buildings, with an application to the simulation of the air flow within a telescope building. The finite [...]

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• Mould filling simulation using finite elements

  R. Codina, U. Schäfer, E. Oñate

  Int. J. of Num. Meths. for Heat and Fluid Flow (1994). Vol. 4 (1), pp. 291-310

  
  

  Abstract

  In this paper we consider several aspects related to the application of the pseudo‐concentration techniques to the simulation of mould filling processes. We discuss, in particular, the smoothing of the front when finite elements with interior nodes are employed and the evacuation of air through the introduction of temporary free wall nodes. The basic numerical techniques to solve the incompressible Navier—Stokes equations are also briefly described. The main features of the numerical model are the use of div‐stable velocity—pressure interpolations with discontinuous pressures, the elimination of the pressure via an iterative penalty formulation, the use of the SUPG approach to deal with convection‐dominated problems and the temporal integration using the generalized trapezoidal rule. At the end of the paper we present some numerical results obtained for a two‐dimensional test problem showing the ability of the method to capture complicated flow patterns.

  Abstract
  In this paper we consider several aspects related to the application of the pseudo‐concentration techniques to the simulation of mould filling processes. We discuss, in [...]

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• Análisis de puentes mediante el método de la banda finita

  E. Oñate

  Hormigón y Acero (1977). Vol. 124, pp. 53-85

  
  

  Abstract

  Se presenta el análisis general de estructuras formadas por un ensamblaje de placas y vigas y con sección transversal constante, mediante una combinación de elementos finitos transversalmente y series de Fourier en dirección longitudinal. Se ha tenido en cuenta en el análisis el efecto de la deformación transversal debida al esfuerzo cortante, que puede ser importante si los espesores de los componentes que forman la estructura son considerables. Debido a la generalidad del análisis se evita la dificultad de tener que establecer hipótesis simplificadoras para idealizar la estructura, a veces lejos de la realidad, como ocurre en el análisis clásico mediante las teorías de Guyon-Massonet o la de la losa ortótropa. Asimismo permite el estudio de estructuras complejas, como puentes con sección transversal tipo cajón, etc., resultado ser uno de los métodos más versátiles y económicos para el análisis de puentes de los más diversos tipos. Al final del estudio se analizan diversas estructuras tipo puente, comparándose los resultados obtenidos aplicando el método de la banda finita, el método de los elementos finitos y el método del prisma finito. 

  Abstract
  Se presenta el análisis general de estructuras formadas por un ensamblaje de placas y vigas y con sección transversal constante, mediante una combinación [...]

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• Wrinkling and folding analysis of elastic membranes using an enhanced rotation-free thin shell triangular element

  F. Flores, E. Oñate

  Finite Elements in Analysis and Design (2011). Vol. 47 (9), pp. 982-990

  
  

  Abstract

  This paper presents a formulation for analysis of thin elastic membranes using a rotation-free shell element within an explicit time integration strategy. The applications presented are isotropic/anisotropic rectangular membranes under shear forces and fabric drapes falling over a pedestal. Results are compared with other numerical results existing in the literature.

  Abstract
  This paper presents a formulation for analysis of thin elastic membranes using a rotation-free shell element within an explicit time integration strategy. The applications [...]

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• Advancing front techniques for filling space with arbitrary separated objects

  R. Löhner, E. Oñate

  Finite Elements in Analysis and Design (2010). Vol. 46 (1-2), pp. 140-151

  
  

  Abstract

  A review is given of advancing front techniques for filling space with arbitrary separated objects. Over the last decade, these techniques have reached a considerable degree of maturity and are being used to generate clouds of points for SPH and FPM simulations, as well as spheres, ellipsoids, objects defined by a collection of spheres or polyhedral objects for DEM simulations. Algorithmic as well as implementational aspects are discussed. Techniques to obtain maximum packing, such as closest object placement (during generation) and move/enlarge (after generation) are also considered. Several examples are included that demonstrate the capabilities developed.

  Abstract
  A review is given of advancing front techniques for filling space with arbitrary separated objects. Over the last decade, these techniques have reached a considerable degree [...]

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• Nonlinear finite element analysis of orthotropic and prestressed membrane structures

  J. Valdes-Vazquez, J. Canet, E. Oñate

  Finite Elements in Analysis and Design (2009). Vol. 45 (6-7), pp. 395-405

  
  

  Abstract

  A new methodology for the geometrically nonlinear analysis of orthotropic membrane structures using triangular finite elements is presented. The approach is based on writing the constitutive equations in the principal fiber orientation of the material. A direct consequence of the fiber orientation strategy is the possibility to analyze initially out-of-plane prestressed membrane structures. An algorithm to model wrinkling behavior is also described. Examples of application to a number of membrane structures are presented.

  Abstract
  A new methodology for the geometrically nonlinear analysis of orthotropic membrane structures using triangular finite elements is presented. The approach is based on writing [...]

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• The numerical tools and the professional practice in Civil Engineering

  B. Suarez, E. Oñate, R. Ribó

  Revista de Obras Públicas (2002). Vol. 149 (3418), pp. 7-15

  
  

  Abstract

  This paper presents some thoughts about the evolution of numerical methods and the difficulties posed by their applications to solve real problems of everyday´s engineering. Some remarks on the mathematical and computational tools needed for the practical use of numerical methods are given, together with some best practice rules. Finally the limits and perspectives of numerical methods are discussed.

  Abstract
  This paper presents some thoughts about the evolution of numerical methods and the difficulties posed by their applications to solve real problems of everyday´s engineering. [...]

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• Advances in FE explicit formulation for simulation of metalforming processes

  J. Rojek, O. Zienkiewicz, E. Oñate, E. Postek

  Journal of Materials Processing Technology (2001). Vol. 119, pp. 41-47

  
  

  Abstract

  This paper presents some advances of finite element explicit formulation for simulation of metal forming processes. Because of their computational efficiency, finite element programs based on the explicit dynamic formulation proved to be a very attractive tool for the simulation of metal forming processes. The use of explicit programs in the sheet forming simulation is quite common, the possibilities of these codes in bulk forming simulation in our opinion are still not exploited sufficiently. In our paper, we will consider aspects of bulk forming simulation. We will present new formulations and algorithms developed for bulk metal forming within the explicit formulation. An extension of a finite element code for the thermomechanical coupled analysis is discussed. A new thermomechanical constitutive model developed by the authors and implemented in the program is presented. A new formulation based on the so-called split algorithm allows us to use linear triangular and tetrahedral elements in the analysis of large plastic deformations characteristic to forming processes. Linear triangles and tetrahedra have many advantages over quadrilateral and hexahedral elements. Linear triangles and tetrahedra based on the standard formulations exhibit volumetric locking and are not suitable for large plastic strain simulation. The new formulation allows to overcome this difficulty. New formulations and algorithms have been implemented in the finite element code Stampack developed at the International Centre for Numerical Methods in Engineering in Barcelona. Numerical examples illustrate some of the possibilities of the finite element code developed and validate new algorithms.

  Abstract
  This paper presents some advances of finite element explicit formulation for simulation of metal forming processes. Because of their computational efficiency, finite element [...]

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• Application of explicit FE codes to simulation of sheet and bulk metal forming processes

  J. Rojek, E. Oñate, E. Postek

  Journal of Materials Processing Technology (1998). Vols. 80-81, pp. 620-627

  
  

  Abstract

  This paper presents the application of an explicit dynamic finite element code for simulation of metal forming processes, of both sheet and bulk forming. The experiences reported here have been gained during the development and use of our own explicit program Stampack. An original formulation of a triangular shell element without rotational degrees of freedom is reviewed combining the explicit sheet forming simulation with the implicit springback analysis as well as the parallelization of the explicit program described. An extension of a finite element code for coupled thermomechanical analysis is discussed. A new thermomechanical constitutive model developed by the authors and implemented in the program is presented. Numerical examples illustrate some of the possibilities of the finite element code developed.

  Abstract
  This paper presents the application of an explicit dynamic finite element code for simulation of metal forming processes, of both sheet and bulk forming. The experiences [...]

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