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• Current trends in qualitative reasoning and applications

  N. Piera

  Monograph CIMNE (1995). M33

  
  

  Abstract

  In June 1994 the ARCA group was founded in order to enhance communication between Spanish professionals either directly on indirectly related to Qualitative Reasoning. Thus we are talking about a new-born group which tries to follow mainly the working pattern of the French QR group, established in 1987 and closely partner of ARCA, both in research and organization matters. Our group maintains also important relationship with other European clusters and is a integrated in the now in progress European QR Network. ARCA is structured around five research lines; the members of each one contact each other on a personal and non programmed basis, but two general meetings a year are scheduled so as to, in the one hand letting every “ARCher” learn about every other’s activities and, on the other hand, starting up projects involving the whole group.

  Abstract
  In June 1994 the ARCA group was founded in order to enhance communication between Spanish professionals either directly on indirectly related to Qualitative Reasoning. Thus [...]

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• Technology transfer of the new trends in concrete

  R. Gettu, A. Aguado, S. Shah

  Monograph CIMNE (1995). M32

  
  

  Abstract

  The international RILEM Workshop on Technology Transfer of the New Trends in Concrete (ConTech’94) was held at the Universitat Politècnica de Catalunya (UPC). It was organized by the UPC, the International Center for Numerical Methods in Engineering (CIMNE, Barcelona), and the NSF Center for the Science & Technology of Advanced Cement-Based Materials (ACBM, Northwestern University, Evanston,USA). ConTech’94 was sponsored by the International Union of the Testing and Research Laboratories for Materials and Structures (RILEM), the Commission of the European Communities, the Centro i Desenvolupament Empresarial de Generalitat de Catalunya (CIDEM, Barcelona). The workshop had to two primary objectives. First, to discuss the incorporation of recent developments and research results in the concrete technology for the present and the future. Secondly, to help bridge the gaps between research and practice, and between more and less developed sectors in the field of concrete. 100 participants attended the workshop, 88 of whom were from the European Union (including 11 young researchers whose participation was partially funded by the European Commission). The official language of the workshop was English, and simultaneous translation between Spanish and English was provided. In all, 23 lectures were presented by experts form Europe, America and Japan, on topics covering the important aspects of concrete technology. The papers corresponding to the lectures are included in a book published by E & FN SPON.

  Abstract
  The international RILEM Workshop on Technology Transfer of the New Trends in Concrete (ConTech’94) was held at the Universitat Politècnica de Catalunya (UPC). [...]

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• Nonlinear finite element techniques using and object-oriented code

  A. Villa, A. Rodríguez, A. Huerta

  Monograph CIMNE (1995). M31

  
  

  Abstract

  When treating nonlinear problems with the Finite Element formulation, the need to solve nonlinear sets of equations arises. Classically, those nonlinear sets of equations were solved by performing  an incremental / iterative analysis with a full Newton-Raphson method. Today, one can chose from a wide range of methods. The modifications to the original fNR method use tangent stiffness matrices, which are updated at most once per increment. Quasi-Newton methods use secant matrices instead of tangent matrices. Secant-Newton methods are simplifications of the Quasi-Newton. This work deals, in particular, with the implementation of these methods in an object-oriented code and with the comparison between them on several tests. The expected behavior of the methods is observed from the results. Also, an acceleration line-search technique is implemented to improve the results supplied by the previous methods.

  Abstract
  When treating nonlinear problems with the Finite Element formulation, the need to solve nonlinear sets of equations arises. Classically, those nonlinear sets of equations [...]

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• Evaluation of existing highway bridge systems

  M. Ghosn, J. Casas

  Monograph CIMNE (1996). M30

  
  

  Abstract

  Evaluation, repair and rehabilitation of bridges are increasingly important topic in current efforts to deal with the deteriorating infrastructure of developed countries. In fact, after several years of large scale construction projects to build new highway networks, the number of existing bridges is so large that current administrations need to invest increasingly large amounts of funds on the maintenance, diagnostic and repair of these bridges

  Abstract
  Evaluation, repair and rehabilitation of bridges are increasingly important topic in current efforts to deal with the deteriorating infrastructure of developed countries. [...]

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• Comportamiento térmico de presas de hormigón en servicio

  L. Agulló, A. Aguado, E. Mirambell

  Monograph CIMNE (1995). M29

  
  

  Abstract

  Este trabajo se enmarca en el ámbito de las presas de hormigón en fase de explotación y, dentro de este ámbito, se centra en el análisis de la respuesta térmica de la presa frente a la actuación de la acción térmica ambiental.

  Abstract
  Este trabajo se enmarca en el ámbito de las presas de hormigón en fase de explotación y, dentro de este ámbito, se centra en el análisis [...]

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• Modelling strong discontinuities in solid mechanics via strain softening constitutive equations

  J. Oliver

  Monograph CIMNE (1995). M28

  
  

  Abstract

  This part addresses some fundamental aspects about the use of standard constitutive equations to model strong discontinuities (cracks, shear bands, slip lines, etc.) in solid mechanics analyzes. The so called strong discontinuity analysis is introduced as a basic tool to derive a general framework, in which different families of constitutive equations can be inscribed, then allowing to extract relevant aspects for the intended analysis. In particular, a ling between continuum ad discrete approaches to the strain localization phenomena is obtained. Applications to standard continuum damage and elasto-plastic constitutive equations are presented. Relevant aspects to be considered in the numerical simulation of the problem are alo presented.

  Abstract
  This part addresses some fundamental aspects about the use of standard constitutive equations to model strong discontinuities (cracks, shear bands, slip lines, etc.) in solid [...]

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• Utilización de la información histórica en el análisis regional de las avenidas.

  F. Francés

  Monograph CIMNE (1995). M27

  
  

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• Combination of a non-local damage model for quasi-brittle materials with a mesh-adaptive finite element technique

  I. de-Pouplana, E. Oñate

  Finite Elements in Analysis and Design (2016). Vol. 112, pp. 26-39

  
  

  Abstract

  Progressive fracture in quasi-brittle materials is often treated via strain softening models in continuum damage mechanics. Such constitutive relations favour spurious strain localization and ill-posedness of boundary value problems. The introduction of non-local damage models together with a characteristic length parameter controlling the size of the fracture process zone is known to regularize the problem. In order to account for the non-locality of these models, it is crucial to work with fine spatial discretizations at the damage progress zone. In this paper we present a non-local damage model in combination with a mesh-adaptive finite element technique that can help automatize the analysis of progressive fracture problems in an efficient manner. Classical two-dimensional examples are given to illustrate the presented approach.

  Abstract
  Progressive fracture in quasi-brittle materials is often treated via strain softening models in continuum damage mechanics. Such constitutive relations favour spurious strain [...]

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• The challenge of mass conservation in the solution of free‐surface flows with the fractional‐step method: Problems and solutions

  S. Idelsohn, E. Oñate

  Int. J. Numer. Meth. Biomed. Engng (2010). Vol. 26 (10), pp. 1313-1330

  
  

  Abstract

  The purpose of this paper is to put in evidence that the fractional‐step method (FSM) used to solve the incompressible transient Euler and Navier–Stokes equations for free‐surface flows has a problem inherent to the method that may produce unacceptable variations of the domain volume. A simple modification of the free‐surface boundary term is introduced in order to reduce considerably the volume loss and preserve the computational advantages of the FSM.

  Abstract
  The purpose of this paper is to put in evidence that the fractional‐step method (FSM) used to solve the incompressible transient Euler and Navier–Stokes equations [...]

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• A continuum mechanics model for mechanical fatigue analysis

  S. Oller, O. Salomon, E. Oñate

  Computational Materials Science (2005). Vol. 32 (2), pp. 175-195

  
  

  Abstract

  In this paper, a thermo-mechanical constitutive model for the predictions of fatigue in structures using the finite element method is formulated. The model is based on the damage mechanics of the continuous medium and allows the treatment in a unified way of coupled phenomena such as fatigue with damage, plasticity, viscosity and temperature effects. Basically it is gotten sensitive models to cyclic loads starting from classical non-linear constitutive formulations incorporating the special variable influenced by the characteristics of the cyclic load. A formulation based on the theories of damage and plasticity is developed. The necessary modifications of these theories are outlined in order to include the fatigue phenomena. A brief description of the finite element implementation is given. Finally, results of the performance of the proposed model are shown through the simple fatigue test and the fatigue analysis of an aluminium engine alternator support.

  Abstract
  In this paper, a thermo-mechanical constitutive model for the predictions of fatigue in structures using the finite element method is formulated. The model is based on the [...]

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