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• Análisis termo-mecánico del proceso de fabricación de un tablero del viaducto de Öresund

  T. Prato, R. Faria, M. Cervera, J. Oliver

  (1999). Research Report, Nº PI165

  
  

  Abstract

  El objetivo de este trabajo es presentar una metodología para el estudio del riesgo de fisuración de una estructura de hormigón en primeras edades. Para ello, se presenta un modelo termo-quimio-mecánico y se estudia el comportamiento estructural del tablero de uno de los viaductos de acceso al puente de Öresund (Dinamarca) durante el proceso de construcción y los 10 primeros días de vida. Esta obra se encuentra en proceso de construcción en el Yard que la constructora DRAGADOS posee en el Puerto Real (Cádiz). Primeramente, en el Capítulo 2, se describe los fundamentos básicos del modelo numérico que se propone. A continuación, en el Capítulo 3, se presenta un análisis del tablero del viaducto mencionado anteriormente, que consiste en evaluar el riesgo de fisuración provocado por el calentamiento asociado a la liberación del calor de hidratación y su proceso de construcción y los materiales utilizados para la construcción del viaducto. Seguidamente, en el Capítulo 4, se presenta el análisis térmico correspondiente a la simulación del proceso de hidratación del hormigón del tablero. Se incluyen algunos estudios sobre las posibles consecuencias de la modificación del proceso de calentamiento debido al cambio de las condiciones ambientales y de curado. En el Capítulo 5 se presenta el análisis termo-mecánico del proceso de construcción de uno de los tramos del viaducto. Se presentan también estudios alternativos sobre la evolución del riesgo de fisuración bajo diferentes escenarios de ejecución. Para ello se estudia el comportamiento estructural en condiciones de invierno y verano.

  Abstract
  El objetivo de este trabajo es presentar una metodología para el estudio del riesgo de fisuración de una estructura de hormigón en primeras edades. Para [...]

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• Numerical Simulation of Heat Treatment Processes on Industrial Steel Parts

  B. Lax, M. Cervera, M. Chiumenti

  Monograph CIMNE (2003). M84

  
  

  Abstract

  The aim of this work is to fullfill the given requirements: A finite numerical program, originally developed to solve a great variety of thermo-mechanical problems, was adapted to a specific industrial problem by a user who was confrontated for the first time with both the industrial problem and the developed computer program.

  Abstract
  The aim of this work is to fullfill the given requirements: A finite numerical program, originally developed to solve a great variety of thermo-mechanical problems, was adapted [...]

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• Characterization of mechanical properties of biological tissue – Application to the FEM analysis of the urinary bladder

  E. Oñate, F. Bellomo, V. Monteiro, S. Oller, L. Nallim

  (2014). Multiscale Simulations and Mechanics of Biological Materials, S. Li et al (Eds), Wiley

  
  

  Abstract

  An approach is presented for studying the mechanical behavior of soft biological tissue using the finite‐element method and a general constitutive model. The overall computational approach is used for the analysis of the mechanical behavior of the urinary bladder. Bladder tissue is modeled as a composite material formed by a soft matrix reinforced with preferentially oriented fibers. A procedure for identifying the mechanical properties of the main constituents of the bladder tissue by an inverse method is detailed. The mechanical parameters are used for the numerical simulation of the mechanical behavior of the bladder during filling within the finite‐element method.

  Abstract
  An approach is presented for studying the mechanical behavior of soft biological tissue using the finite‐element method and a general constitutive model. The overall computational [...]

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• The Particle Finite Element Method for multi-fluid flows

  S. Idelsohn, M. Mier-Torrecilla, J. Marti, E. Oñate

  (2011). Particle-Based Methods, Computational Methods in Applied Sciences, Springer, E. Oñate and R. Owen (Eds.), Vol. 25, pp. 135-158

  
  

  Abstract

  This paper presents the Particle Finite Element Method (PFEM) and its application to multi-fluid flows. Key features of the method are the use of a Lagrangian description to model the motion of the fluid particles (nodes) and that all the information is associated to the particles. A mesh connects the nodes defining the discretized domain where the governing equations, expressed in an integral form, are solved as in the standard FEM.We have extended the method to problems involving several different fluids with the aim of exploiting the fact that Lagrangian methods are specially well suited for tracking any kind of interfaces.

  Abstract
  This paper presents the Particle Finite Element Method (PFEM) and its application to multi-fluid flows. Key features of the method are the use of a Lagrangian description [...]

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• A multi-method approach towards understanding the pathophysiology of aortic dissections – the complementary role of in-silico, in-vitro and in-vivo information

  P. Rudenick, M. Bordone, B. Bijnens, E. Soudah, E. Oñate, D. García-Dorado, A. Evangelista

  (2010). Lecture Notes in Computer Science, Camara, O; Pop, M; Rhode, K; et al. (Eds.), Book Series: Lecture Notes in Computer Science, Vol. 6364, pp. 114-123

  
  

  Abstract

  Management and follow-up of chronic aortic dissections continues to be a clinical challenge due to progressive aortic dilatation. To predict dilatation, guidelines suggest follow-up of the aortic diameter. However, dilatation is triggered by haemodynamic parameters (pressure and wall shear stresses (WSS)), and geometry of false (FL) and true lumen (TL). We aimed at a better understanding of TL and FL haemodynamics by performing in-silico (CFD) and in-vitro studies on an idealized dissected aorta and compared this to a typical patient. We observed an increase in diastolic pressure and wall stress in the FL and the presence of diastolic retrograde flow. The inflow jet increased WSS at the proximal FL while a large variability in WSS was induced distally, all being risk factors for wall weakening. In-silico, in-vitro and in-vivo findings were very similar and complementary, showing that their combination can help in a more integrated and extensive assessment of aortic dissections, improving understanding of the haemodynamic conditions and related clinical evolution.

  Abstract
  Management and follow-up of chronic aortic dissections continues to be a clinical challenge due to progressive aortic dilatation. To predict dilatation, guidelines suggest [...]

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• Shock control bump design optimization on natural laminar aerofoil

  D. Lee, J. Periaux, K. Srinivas, L. González, N. Qin, E. Oñate

  (2010). Computational Fluid Dynamics Review 2010, Part 9, 253-259, Edited by M M Hafez (University of California, Davis, USA), K Oshima (University of Tokyo, Japan), & Dochan Kwak (NASA Ames Research Center, USA)

  
  

  Abstract

  The chapter investigates Shock Control Bumps (SCB) on a Natural Laminar Flow (NLF) aerofoil; RAE 5243 for Active Flow Control (AFC). A SCB approach is used to decelerate supersonic flow on the suction/pressure sides of transonic aerofoil that leads delaying shock occurrence or weakening of shock strength. Such an AFC technique reduces significantly the total drag at transonic speeds. This chapter considers the SCB shape design optimisation at two boundary layer transition positions (0 and 45%) using an Euler software coupled with viscous boundary layer effects and robust Evolutionary Algorithms (EAs). The optimisation method is based on a canonical Evolution Strategy (ES) algorithm and incorporates the concepts of hierarchical topology and parallel asynchronous evaluation of candidate solution. Two test cases are considered with numerical experiments; the first test deals with a transition point occurring at the leading edge and the transition point is fixed at 45% of wing chord in the second test. Numerical results are presented and it is demonstrated that an optimal SCB design can be found to significantly reduce transonic wave drag and improves lift on drag (L/D) value when compared to the baseline aerofoil design.

  Abstract
  The chapter investigates Shock Control Bumps (SCB) on a Natural Laminar Flow (NLF) aerofoil; RAE 5243 for Active Flow Control (AFC). A SCB approach is used to decelerate supersonic [...]

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• New computational challenges in fluid-structure interactions problems

  S. Idelsohn, E. Oñate, R. Rossi, J. Marti, F. Del Pin

  (2009). ECCOMAS Multidisciplinary Jubilee Symposium, J. Eberhardsteiner, Ch. Hellmich, H. Mang and J. Périaux (Eds.)

  
  

  Abstract

  In this paper the so-called added-mass effect is investigated from a different point of view of previous publications. The monolithic fluid structure problem is partitioned using a static condensation of the velocity terms. Following this procedure the classical stabilized projection method for incompressible fluid flows is introduced. The procedure allows obtaining a new pressure segregated scheme for fluid-structure interaction problems which has good convergent characteristics even for biomechanical application, where the added mass effect is strong. The procedure reveals its power when it is shown that the same projection technique must be implemented in staggered FSI methods.

  Abstract
  In this paper the so-called added-mass effect is investigated from a different point of view of previous publications. The monolithic fluid structure problem is partitioned [...]

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• Simulation of structural response to violent-free surface flows

  R. Löhner, C. Yang, E. Oñate

  (2008). Numerical Modeling of Coupled Phenomena in Science and Engineering, M.C. Suárez Arriaga, J. Bundschuh, F.J. Dominguez-Mota (Eds.)

  
  

  Abstract

  High sea states, waves breaking near shores andmoving ships, the interaction of extremewaveswith floating structures, green water on deck and sloshing (e.g. in liquid natural gas (LNG) tankers) are but a few examples of flows with violent free surface motion. The bodies exposed to these flows experience large, time-varying forces that can lead to fatigue and/or failure. It is therefore imperative to have a predictive capability in order to guarantee operability and optimize the lifespan under these conditions.

  Abstract
  High sea states, waves breaking near shores andmoving ships, the interaction of extremewaveswith floating structures, green water on deck and sloshing (e.g. in liquid natural [...]

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• A variational formulation for the multilayer perceptron

  R. Lopez, E. Oñate

  (2006). S. Kollias et al (Eds.), ICANN 2006, Part I, LNCS 4131, pp. 19-168, Germany.

  
  

  Abstract

  In this work we present a theory of the multilayer perceptron from the perspective of functional analysis and variational calculus. Within this formulation, the learning problem for the multilayer perceptron lies in terms of finding a function which is an extremal for some functional. As we will see, a variational formulation for the multilayer perceptron provides a direct method for the solution of general variational problems, in any dimension and up to any degree of accuracy. In order to validate this technique we use a multilayer perceptron to solve some classical problems in the calculus of variations.

  Abstract
  In this work we present a theory of the multilayer perceptron from the perspective of functional analysis and variational calculus. Within this formulation, the learning problem [...]

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• Analysis of the structure of gothic cathedrals. Application to Barcelona cathedral

  P. Roca, L. Pellegrini, E. Oñate, A. Hanganu

  (1998). Structural Analysis of Historical Constructions II, P. Roca, J.L. González, E. Oñate and P. B. Lourenço(Eds.), CIMNE, Barcelona, Spain

  
  

  Abstract

  The study of ancient structures composed of stone arches and vaults requires the use of specific techniques of analysis endowed with powerful procedures for the modelling of geometry, the simulation of the mechanical response of the various materials (including ashlar blocks and masonry, backings and fills) and the simulation of the structure or may have affected it through history. More specifically, those techniques must be able to reproduce the actual conditions of thrust equilibrium between the large number of curved, linear or two-dimensional members involved. The validity of several modelling techniques with a very different level of sophistication is studied through their use in the study of a particular Gothic construction: Barcelona Cathedral. The various techniques used were developed at the school of civil engineering of the technical university of Catalonia and have already been used in the analysis of a set historical constructions, including the Basilica of San Marco (Oñate et al., 1997) and the Crypt of the Colònia Güell (Roca, 1997). The present study of Barcelona Cathedral, now under development, is thus not only aimed at gaining a better understanding of various aspects of the resistance of Gothic constructions (and the southern and Catalan Gothic, in particular) but also at appraising the possibilities and limitations of various analytical techniques.

  Abstract
  The study of ancient structures composed of stone arches and vaults requires the use of specific techniques of analysis endowed with powerful procedures for the modelling [...]

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