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In July 2019, the largest inflatable hangar of the world has been installed by Buildair in Jeddah. Its main function is to shelter and maintain aircrafts such as Airbus 330 or Boeing 777-200ER, during an expected lifetime of 7 years. In addition to size (97,9 x 90 x 33 m) , other outstanding values are the structural efficiency: 40.000 kp / 8.811 m2 = 4,5 kp/m2, the storage volume of parts (700 m3) = 3 ‰ of the built volume (228.365 m3) and the total time (including design, manufacture, transport and installation): 6 months. This values are much lower than those of a conventional hangar.

Este trabajo describe una metodología de cálculo para evaluar la rotura de piezas y estructuras de hormigón y su aplicación a cuatro ensayos típicos en laboratorios de resistencia de materiales. Los resultados de los ensayos son comparados y analizados desde el punto de vista experimental y numérico a fin de poner de manifiesto la necesidad de que los ensayos experimentales se basen en resultados numéricos, y en contrapartida que los modelos numéricos sigan fielmente el comportamiento y la física que ocurre en los experimentos de laboratorio. Esta comparativa permite explicar los mecanismos que ocurren a lo largo del experimento y también verificar la integridad e idoneidad del código de cálculo y del modelo numérico a utilizar. This paper describes a computation methodology to evaluate the ultimate strength and fracture of concrete samples and structures and its application to four typical tests of experimental laboratories of strength of materials. The tests results are compared and analysed from the experimental and numerical points of view in order to highlight the need for experimental trials to use the information derived from numerical results and, in turn, to validate that numerical models follow the behaviour and physics that occur in laboratory tests This comparison allows to explain the different mechanisms that occur throughout the experiments.

This is the accepted version of the following article: [Franci, A., Oñate, E., and Carbonell, J. M. (2016) Velocity-based formulations for standard and quasi-incompressible hypoelastic-plastic solids. Int. J. Numer. Meth. Engng, 107: 970–990. doi: 10.1002/nme.5205], which has been published in final form at http://onlinelibrary.wiley.com/doi/10.1002/nme.5205/abstract We present three velocity-based updated Lagrangian formulations for standard and quasi-incompressible hypoelastic-plastic solids. Three low-order finite elements are derived and tested for non-linear solid mechanics problems. The so-called V-element is based on a standard velocity approach, while a mixed velocity–pressure formulation is used for the VP and the VPS elements. The two-field problem is solved via a two-step Gauss–Seidel partitioned iterative scheme. First, the momentum equations are solved in terms of velocity increments, as for the V-element. Then, the constitutive relation for the pressure is solved using the updated velocities obtained at the previous step. For the VPS-element, the formulation is stabilized using the finite calculus method in order to solve problems involving quasi-incompressible materials. All the solid elements are validated by solving two-dimensional and three-dimensional benchmark problems in statics as in dynamics.

Progressive fracture in quasi-brittle materials such as concrete, rocks, soils, is often treated as strain softening in continuum damage mechanics. Such constitutive relations favour spurious strain localization and ill-posedness of boundary value problems, and call for some kind of regularization. In the present work, two different approaches are presented: a partially regularized local damage model that adjusts the softening part of a stress-strain law depending on the size of the element, and a fully regularized non-local damage model that introduces the characteristic length as an additional material parameter controlling the size of the fracture process zone. In addition, the strain softening of such models usually results in highly complex structural responses, including the snap-back type, and thus in this work we will be discussing non-linearity associated to damage modelling, and a global arc-length method for tracing the equilibrium path will be exposed. Furthermore, in the context of non-local damage models it is crucial to work with fine spatial discretizations at the damage progress zone, so that elements are smaller than the characteristic length. In this regard, a meshadaptive technique has been implemented with the purpose of enhancing the efficiency of the numerical analysis. Finally, two classical examples, the three-point bending test, and the single-edge notched beam test, are performed in order to analyse the mesh objectivity of the implemented integral-type non-local damage model, and assess the strengths and limitations of the mesh-adaptive procedure.

En este proyecto se han desarrollado herramientas multimedia de autoaprendizaje para cálculo de estructuras por el método de los elementos finitos (MEF). Estas herramientas permitirán mejorar la formación de los estudiantes de ingeniería en este ámbito, y en particular facilitarán el desarrollo de las competencias de aprendizaje autónomo, y apoyarán las necesidades de aprendizaje a lo largo de la vida. En el proyecto, han participado 7 profesores de los departamentos CEN y RMEE de la UPC. Se contempla la implantación futura de las herramientas en diversas asignaturas de los departamentos involucrados, a partir del desarrollo en el proyecto de diferentes "temas de estudio", cada uno de ellos compuesto por tres bloques: ejemplo, ejercicio y evaluación. Como prueba de concepto, se han implantado las herramientas de autoaprendizaje en la asignatura “Teoría y Práctica del MEF en Construcción Naval” impartida en la Facultad de Náutica de Barcelona. Para esta tarea, se han utilizado diferentes temas de estudio específicos del campo naval, que se han desarrollado en el proyecto. Los resultados de la evaluación de la implantación han sido muy positivos, incluyendo valoraciones de los alumnos superiores a 4.5/5, y destacando en varios casos el interés en disponer de temas de estudio adicionales.

The proposal of an artificial bladder is still a challenge to overcome. Bladder cancer is among the most frequent cases of oncologic diseases in United States and Europe. It is considered a major medical problem once this disease has high rates of reoccurrence, often leading to the extirpation of this organ. The most refined solution to replace this organ is the ileal bladder, which consists of a neobladder made of the patient’s intestinal tissue. Unfortunately this solution presents not only functional mechanical problems, described on the literature as voiding and leaking problems, but also biological ones (i.e. bone loss, given the absorption by the intestine of substances that should be eliminated from the organism). Urged by the urological community of the Hospital Clinic de Barcelona and backgrounded by its experience in the numerical simulation of biomedical structures, the Center of Numerical Methods in Engineering (CIMNE) had the initiative to provide the research of the mechanics of the urinary bladder and the simulation of fluid structure interaction (FSI) to account for the filling and voiding of this organ with urine. The Finite Element Method (FEM) simulation of the real bladder and the comprehensive understanding of the mechanics of this organ and its interaction with urine will give the possibility to propose geometrical improvements and study suitable materials for an artificial solution to address the cases on which the bladder needs to be removed. To reach this goal, first we proceeded to the bibliographic review of mathematical models of the urinary apparatus and to a comprehensive study of the physiology and dynamics of the bladder. A review of the major urological structures, kidney, ureter and urethra, takes place. To consider boundary conditions other surrounding structures to the urinary system are also studied. In the second part of the thesis, we propose the numerical model to study the human urinary bladder. The behavior of the detrusor muscle during filling and voiding of the bladder with urine and its ability to promote the storage of urine under low pressure need to be accurately represented, requiring the implementation of a non-linear constitutive model. The mathematical model needs to be capable to simulate the mechanical variables that govern this organ and the properties of the urine. The nonlinear behavior of living tissues is implemented and validated with examples from the literature. The quasi-incompressibility property of urine and the navierstokes equations for the fluid are taken into account. The geometry of the bladder needs to be taken into account, and the implementation of a 3D computational model obtained from the computerized tomography of a cadaver male adult is considered. The data has been treated to consider boundary conditions. Two models have been conceived: one meshed with four nodes tetrahedral and another meshed with shell elements. FSI must work for the simulation of filling and voiding of the bladder. Due to the close densities of the materials the scheme used to solve fluid-structure needs to be carefully selected. The proposed numerical model and the filling and voiding analysis are finally validated with standardized urodynamic tests. The final part of the thesis, the simulation of a neobladder is presented, being the first step to simulate numerically artificial materials for bladder replacement.

Las conferencias presentadas durante la Jornada Técnica sobre Avances en investigación aplicada en seguridad hidráulica de presas organizada por el Centro de Estudios Hidrográficos del CEDEX y la Universidad Politécnica de Madrid el mes de junio de 2013 versan sobre la mejora de la seguridad hidráulica de las presas, una materia de especial importancia en nuestro país (habida cuenta del elevado número de infraestructuras de regulación en servicio y de su antigüedad media) y constituye una tarea en la que tanto el CEDEX como la Universidad Politécnica de Madrid han trabajado activamente en los últimos años. El Centro Internacional de Métodos Numéricos en Ingeniería (CIMNE) es un centro de investigación dependiente del Gobierno de Cataluña y de la Universidad Politécnica de Cataluña creado en 1987. Su principal actividad es el desarrollo y aplicación de métodos numéricos innovadores para resolver problemas prácticos en diversos campos de la ingeniería, y se desarrolla fundamentalmente en el marco de proyectos de investigación nacionales e internacionales. En los últimos años el centro ha participado en diversos proyectos relacionados con la seguridad de presas, fundamentalmente hidráulica, pero también estructural, en cooperación con diversas empresas y organismos públicos de investigación como el CEDEX y la UPM. La presente comunicación describe brevemente los objetivos principales de los mencionados proyectos, haciendo hincapié en cómo la modelación numérica ha contribuido a alcanzarlos.

A new bilinear 4-noded quadrilateral element (called QLRZ) for the analysis of composite laminated and sandwich plates/shells based on the refined zigzag theory (RZT) proposed by Tessler et al. [1] is presented. The element has seven kinematic variables per node. Shear locking is avoided by introducing an assumed linear shear strain field. The performance of the element is studied in several examples where the reference solution is the 3D finite element analysis using 20-noded hexahedral elements. Finally, the capability for capturing delamination effects is analyzed.

We present three new stabilized finite element (FE) based Petrov–Galerkin methods for the convection–diffusion–reaction (CDR), the Helmholtz and the Stokes problems, respectively.

La enfermedad de Alzheimer (AD) es un desorden neurodegenerativo cuyo diagnóstico clinico es realizado después de excluir otros tipos de demencia y el diagnóstico clinico definitivo requiere además de la presencia de un alto decit cognitivo, la confirmación histológica mediante autopsia de la presencia de proteinas como las neurobras de tau ( ) y amyloid beta (A) en los tejidos cerebrales. AD es una de las enfermedades de mayor impacto social en Europa y América. En el pasado 2005, en Europa fueron diagnosticados 3.600.000 pacientes afectados por AD (fuente: Frost & Sullivan) y en una reciente investigación impulsada por la asociación Alzheimer Europe, se estima que 7.3 millones de personas padecen algún tipo de demencia. A pesar de que la ocurrencia de AD no es un suceso normal en la población mayor, el riesgo de desarrollar la enfermedad se incrementa en esa etapa.

Dealing with large simulation is a growing challenge. Ideally for the wellparallelized software prepared for high performance, the problem solving capability depends on the available hardware resources. But in practice there are several technical details which reduce the scalability of the system and prevent the effective use of such a software for large problems. In this work we describe solutions implemented in order to obtain a scalable system to solve and visualize large scale problems. The present work is based on Kratos MutliPhysics [1] framework in combination with GiD [2] pre and post processor. The applied techniques are verified by CFD simulation and visualization of a wind tunnel problem with more than 100 millions of elements in our in-hose cluster in CIMNE.

Se presentan unas reflexiones sobre el ciclo que las ideas recorren desde que surgen en un entorno universitario hasta que se transforman en un producto industrial. Se concretan estas reflexiones en el contexto de la Escuela Técnica Superior de Ingenieros de Caminos, Canales y Puertos de la Universitat Politècnica de Catalunya y se presentan algunos ejemplos de éxitos en la implantación del denominado Círculo de las Ideas.

This work aims at developing formulations and algorithms where maximum advantage of using Lagrangian finite element fluid formulations can be taken. In particular we concentrate our attention at fluid-structure interaction and thermally coupled applications, most of which originate from practical “real-life” problems. Two fundamental options are investigated - coupling two Lagrangian formulations (e.g. Lagrangian fluid and Lagrangian structure) and coupling the Lagrangian and Eulerian fluid formulations. In the first part of this work the basic concepts of the Lagrangian fluids, the so-called Particle Finite Element Method (PFEM) [1], [2] are presented. These include nodal variable storage, mesh re-construction using Delaunay triangulation/tetrahedralization and alpha shape-based method for identification of the computational domain boundaries. This shall serve as a general basis for all the further developments of this work.

Adaptive mesh refinement is one of the most important tools in Computational Fluid Dynamics (CFD) for solving complex engineering design problems. The paper investigates two practical transonic aerofoil design optimization problems using a genetic algorithm coupled with an Euler aerodynamic analysis tool. The first problem consists in the minimization of transonic drag whereas the second is a reconstruction transonic problem solved by minimizing the pressure error. In both cases, the solutions obtained with and without adaptive mesh refinement are compared. Numerical results obtained by both drag minimization and reconstruction design clearly show that the use of adaptive mesh refinement reduces the computational cost and also produces a better solution.

The present work introduces a new application of the Particle Finite Element Method (PFEM) for the modeling of excavation problems. PFEM is presented as a very suitable tool for the treatment of excavation problem. The method gives solution for the analysis of all processes that derive from it. The method has a high versatility and a reasonable computational cost. The obtained results are really promising.

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.

Cuando una estructura de hormigón armado queda expuesta a la acción del fuego se roducen, tanto en el hormigón como en el acer. un conjunto de fenómenos físico-químicos que pueden comprometer la estabilidad de la misma. Entre los procesos más importantes destaca el de la eclosión (spalling). Se considera que las posibles causas del spalling pueden ser un elevado crecimiento de la presión en los poros (spalling hidraúlico) o un exagerado aumento de las tensiones de compresión debidas a la dilatación térmica restringida. Para poder tener en cuenta en el análisis el spalling hidraúlico es necesario considerar un modelo que tenga en cuenta la componente hídrica del hormigón. En esta monografía se presenta un modelo higro-termo-mecánico que permite representar el comportamiento general del hormigón armado expuesto a elevadas temperaturas y en particular simular el fenómeno de spalling.

The DISHEART project aims at developing a new computer based decision support system (DSS) integrating medical image data, modelling, simulation, computational Grid technologies and artificial intelligence methods for assisting clinical diagnosis and intervention in cardiovascular problems. The RTD goal is to improve and link existing state of the art technologies in order to build a computerised cardiovascular model for the analysis of the heart and blood vessels. The resulting DISHEART DSS interfaces computational biomechanical analysis tools with the information coming from multimodal medical images. The computational model is coupled to an artificial neural network (ANN) based decision model that can be educated for each particular patient with data coming from his/her images and/or analyses. The DISHEART DSS system is validated in trials of clinical diagnosis, surgical intervention and subject-specific design of medical devices in the cardiovascular domain. The DISHEART DSS also contributes to a better understanding of cardiovascular morphology and function as inferred from routine imaging examinations. Four reputable medical centers in Europe took an active role in the validation and dissemination of the DISHEART DSS as well as the elaboration of computational material and medical images. The integrated DISHEART DSS supports health professionals in taking promptly the best possible decision for prevention, diagnosis and treatment. Emphasis was put in the development of userfriendly, fast and reliable tools and interfaces providing access to heterogeneous health information sources, as well as on new methods for decision support and risk analysis. The use of Grid computing technology is essential in order to optimise and distribute the heavy computational work required for physical modelling and numerical simulations and especially for the parametric analysis required for educating the DSS for every particular application. The four end user SMEs participating in the project benefits from the new DISHEART DSS. The companies COMPASS, QUANTECH and Heartcore will market the DSS among public and private organizations related to the cardiovascular field. EndoArt will exploit the DISHEART DSS as a support for enhanced design and production of clinical devices. The partnership was sought in order to gather the maximum complementary of skills for the successful development of the project Disheart DSS, requiring experts in Mechanical sciences, Medical sciences, Informatic, and FEM technique to grow up the testes.

An increasing interest is rising on the study of rockfill embankment dams during overspilling. Design criteria of earth dams are being reviewed in many countries to guarantee an increasing safety level in front of an exceptional flooding. The possibility of studying the failure process is currently limited by the lack of a precise knowledge and by the absence of a suitable computational method which can predict accurately the onset and evolution of breaching. The analysis of the possible consequences of an accidental overspill is then impossible or very imprecise and the necessary economical measures for solving the problem are then inefficient. An appropriate computational method will help to reduce the economic impact of the investments in dam safety and in emergency plans for embankment dams. The dam failure is mainly due to the hydrodynamic forces acting on the rockfill material in the downstream face. Two failure mechanisms occur in an alternative or combined mode: dragging of rockfill particles with erosive effects, and loss of stability of a part of the downstream region due to the slippage of a bulk mass of the rockfill material. The loss of a relevant part of the rockfill material in the downstream side of the dam, can lead to mechanical failure of the impervious region, either if this is formed by a concrete (or asphalt) face, or by a clay core. In the latter case, erosion of the cohesive material can also influence the failure process, but the scale time of appearance of this erosion phenomenon is so different from the principal erosion of the rockfill part, that this second one is not taken into account. The objectives of the current work is to develop and validate a new computational method of general applicability that allows treating above problems. The method will combine advanced finite element and particle techniques. Fluid-structure interaction effects and non-linear geometrical and mechanical effects in the dam material will be considered. The specific features of the analysis method proposed make it appropriate to treat the rockfill material adjacent to the downstream surface where a transfer of momentum between the water running over the dam surface and that moving through the interior due to seepage occurs

El objetivo principal del presente trabajo es el desarrollo, formulación e implementación computacional, de un modelo numérico para el tratamiento de la no linealidad constitutiva de laminados reforzados con fibras, en el contexto de la mecánica de los medios continuos. Esta formulación plantea combinar (o componer) los comportamientos de materiales simples (homogéneos) con el objetivo de obtener la respuesta mecánica del material compuesto (heterogéneo).

En el desarrollo de este trabajo se ha estudiado en detalle el modelo clásico de viga Cosserat, su formulación tangente y las teorías de alto orden que se puede establecer con el. El análisis se ha realizado adoptando un punto de vista general que permite comparar la eficacia de diversos sistemas de parametrización de las rotaciones incluyendo en el análisis los sistemas de alta parametrización-y de distintas formas de interpolación de las variables cinemáticas: lineal o no lineal.

In this monograph is presented a method for the solution of an incompressible viscous fluid flow with heat transfer and solidification usin a fully Lagrangian description on the motion. The originality of this method consists in assembling various concepts and techniques which appear naturally due to the Lagrangian formulation.

One of the aims of this text is to show some important results in LES modelling and to identify which are main mathematical problems for the development of a complete theory. A relevant aspect of LES theory, which we will consider in our work, is the close relationship between the mathematical properties of LES models and the numerical methods used for their implementation. In last years it is more and more common the idea in the scientific community, especially in the numerical community, that turbulence models and stabilization techniques play a very similar role. Methodologies used to simulate turbulent flows, RANS or LES approaches, are based on the same concept: unability to simulate a turbulent flow using a finite discretization in time and space. Turbulence models introduce additional information (impossible to be captured by the approximation technique used in the simulation) to obtain physically coherent solutions. On the other side, numerical methods used for the integration of partial differential equations (PDE) need to be modified in order to able to reproduce solutions that present very high localized gradients. These modifications, known as stabilization techniques, make possible to capture these sharp and localized changes of the solution. According with previous paragraphs, the following natural question appears: Is it possible to reinterpret stabilization methods as turbulence models? This question suggests a possible principle of duality between turbulence modelling and numerical stabilization. More than to share certain properties, actually, it is suggested that the numerical stabilization can be understood as turbulence. The opposite will occur if turbulence models are only necessary due to discretization limitations instead of a need for reproducing the physical behaviour of the flow. Finally: can turbulence models be understood as a component of a general stabilization method?

We present a variational formulation of the finite calculus (FIC) equations for problems in mechanics governed by differential equations with symmetric operators. Applications considered include solid mechanics, diffusion-transport and diffusion-reaction problems. The key of the variational formulation is the identification of the FIC governing equations with the classical differential equations of mechanics written in terms of modified non-local variables. A total potential energy (TPE) functional is found in terms of the modified variables. The FIC equations in the domain and the boundary are recovered as the Euler-Lagrange equations and the natural boundary condition of the TPE functional, respectively. Symmetric finite element equations are obtained after discretization of the TPE functional, therefore preserving the symmetry of the governing infinitesimal equations. The variational FIC expression is reinterpreted as a Petrov Galerkin weighted residual form of the original FIC equations with non-local weighting functions. The analogy of the variational FIC-FEM formulation with a discontinuous Galerkin method is recognized. Extensions to multidimensional linear elastostatics and diffusion-reaction problems are presented.

A new decision support system (DSS) for the risk assessment and management of emergency scenarios due to severe floods was created. The DSS combines environmental and geo-physical data from earth observation, with advanced computer simulation, graphical visualisation methods and artificial intelligence techniques, for generating useful knowledge contributing to the flood risk assessment and prevention of floods. The aim of the RAMFLOOD project is to develop a new DSS to assist public administrators and emergency services in the flood risk assessment and in the management of different emergency scenarios in the floodplain area.

The objective of the RAMFLOOD project is to develop and validate a new decision suuport system (DSS) for the risk assessment and management of emergency scenarios due to severe floods. The DDS combines environmental land geo-physical data from earth observation, with advanced computer simulation and graphical visualisation methods and artificial intelligence techniques, for generating knowledge contributing to the risk prevention of floods and the design of effective response actions maximising the safety of infrastructures and human life.

A Volume of Fluid (VOF) technique has been developed and coupled with an incompressible Euler/Navier Stokes solver operating on adaptive, unstructured grids to simulate the interactions of extreme waves and three-dimensional structures. The present implementation follows the classic VOF implementation for the liquid-gas system, considering only the liquid phase. Extrapolation algorithms to obtain velocities and pressure in the gas region near the free surface have been implemented. The VOF technique is validated against the classic dam-break problem, as well as series of 2-D sloshing experiments and results from SPH calculations. These and a series of other examples demonstrate that the present CFD method is capable of simulating violent free surface fows with strong nonlinear behaviour.

A finite calculus formulation of the level set equation is presented. Quadratic Galerkin finite elements are used for spatial discretization. A unique stabilization parameter is computed. A time stabilization parameter allowing the use of the forward Euler scheme with Courant number larger than one is presetend.

The basis of the FIC method is the satisfaction of the standard equations for balance of momentum (equilibrium of forces) and mass conservation in a domain of finite size and retaining higher order terms in the Taylor expansions used to express the different terms of the differential equations over the balance domain. The modified differential equations contain additional terms which introduce the necessary stability in the equations to overcome the volumetric locking problem in incompressible situations. The same ideas are applied in this paper to derive a stabilized formulation for non linear dynamic finite element analysis of quasi incompressible and fully-incompressible solids using linear triangles and tetrahedra. Examples of application of the new stabilized formulation to the semi-implicit and explicit non linear transient dynamic analysis of an impact problem and a bulk forming process are presented.

This paper shows a step forward in the development of a stabilized method for solving the Reynolds equations (RANSE) including free surface effects. The starting point of this method is the modified governing differential equations for an incompressible turbulent viscous flow and the free surface condition, incorporating necessary stabilization terms via a Finite Increment Calculus (FIC) procedure. Time integration scheme of the method is based on an implicit monolithic second order method. Implementation of the algorithm, based on the Finite Element Method (FEM) using unstructured grids of linear tetrahedra, allows us to take into account dynamic sinkage and trim. This paper also presents a validation study of numerical results obtained for America’s Cup boats.

In this work the problem of overcoming local minima in the solution of nonlinear optimisation problems is addressed. As a first step, the existing nonlinear local and global optimisation methods are reviewed so as to identify their advantages and disadvantages. Then, the major capabilities of a number of successful methods such as genetic, deterministic global optimisation methods and simmulated annealing, are combined to develop an alternative global optimisation approach based on a Stochastic-Probabilistic heuristic. The capabilities, in terms of robustness and efficiency, of this new approach are validated through the solution of a number of nonlinear optimisation problems. A well know evolutionary technique (Differential Evolution) is also considered for the solution of these case studies offering a better insight of the possibilities of the method proposed here.

El objetivo principal de esta monografia es obtener y desarrollar la formulacion del Método de Puntos Finitos, como método totalmente libre de malla, para la resolución de las ecuaciones de la elasticidad en solidos. Para cumplir este objetivo se pretende determinar y estudiar los aspectos relevantes de la fundamentacion matemática del método, entre otros, la aproximacion mediante mínimos cuadrados móviles, la función de ponderación y la técnica de colocación puntual. Para un completo análisis de las capacidades del método, se implementará un código que permita resolver diversos problemas, de índole mas bien académico, principalmente en 1D, 2D y en forma complementaria en 3D. Se pretende finalmente extender el desarrollo en la formulación de MPF para abarcar, ademas del análisis estático,algunos problemas de la dinámica lineal de sólidos

The document presents a numerical model of rocks and soils using spherical Discrete Elements, also called Distinct Elements. The motion of spherical elements is described by means of equations of rigid body dynamics. Explicit integration in time yields high computational efficiency. Spherical elements interact among one another with contact forces, both in normal and tangential directions. Efficient contact search scheme based on the octree structures has been implemented. Special constitutive model of contact interface taking into account cohesion forces allows us to model fracture and decohesion of materials. Numerical simulation predicts wear of rock cutting tools. The developed numerical algorithm of wear evaluation allows us us to predict evolution of the shape of the tool caused by wear. Results of numerical simulation are validated by comparison with experimental data.

A meshless method is presented for the solution of the incompressible fluid flow equation using a lagrangian formulation. The interpolated function are those used in the moving least square approximations and the time integration is introduced in a semi-implicit way by a fractional step method. Both classical stabilization terms used in incompressible Navier-Stokes equations are unnecessary: numerical diffusion for convective terms are unnecessary due to the lagrangian formulation, and stabilization of pressure due to the incompressibility constraint for equal order interpolations is eliminated using the fractional step method.

L’any 1995, l’IEC acordà iniciar un projecte d’elaboració d’estudis periòdics sobre l’estat de la recerca a Catalunya, anomenat Reports de la recerca a Catalunya. Amb el suport de la Generalitat de Catalunya, i coordinat per la Secretaria Científica de l’IEC, el projecte es basava en la redacció d’una sèrie d’informes sobre cada una de les àrees en què es dividia l’activitat científica. Redactats per investigadors de prestigi, els informes eren debatuts públicament abans de tancar-ne la versió definitiva.

En esta monografía se presenta un modelo constitutivo que permite tener en cuenta el modelo constitutivo que permite tener en cuenta el comportamiento de los materiales compuestos a través del método de los elementos finitos. El objetivo general del trabajo consiste en presentar una metodología que permita evaluar el comportamiento de materiales compuestos, para así poder estudiar y modificar el diseñio del material en función de los esfuerzos a los que se encuentre sometido. El modelo constituvo esta basado en tres teorías que permiten simular los diversos mecanismos que se generan durante el proceso de falla de los materiales compuestos.

El aprendizaje de los nuevos métodos de cálculo de estructuras, utilizados en el análisis de problemas de ingeniería, no es una tarea fácil. Las herramientas de enseñanza tradicionales son insuficientes para mostrar la potencia de las técnicas numéricas de análisis. Partiendo de ello se ha desarrollado un entorno educativo que pretende superar los inconvenientes de los métodos clásicos de enseñanza, comenzando por los métodos matriciales para análisis de estructuras de barras y continuando con el método de los elementos finitos. El entorno educativo se ha desarrollado en base a tres bloques: teoría, ejemplos y ejercicios. Los dos primeros guían al usuario en una primera etapa de aprendizaje y finalmente el tercer bloque le permite experimentar con sus propios problemas reforzando su nivel de conocimientos. Los programas están dirigidos principalmente a estudiantes de las carreras técnicas y a los profesores y profesionales de empresas que deseen actualizar sus conocimientos. En este artículo se presentan algunas de las características de los programas educativos Vigas y Pórticos, ED-Tridim y ED-Elas2D y los resultados de su utilización real por estudiantes de escuelas técnicas.

La monografía presenta la aplicación de diversos métodos evolutivos a la optimización topológica de estructuras. El Trabajo de investigación se basa en la busca de una distribución de material dentro de un dominio específico que reúna unas condiciones establecidas. Los algoritmos aplican las leyes de supervivencia del mejor dotado de Darwin y su base genético molecular: mutación y recombinación aleatoria de material genético.

Se presenta una nueva técnica de predicción de puntos críticos en el análisis de inestabilidad estructural por el MEF. El procedimiento se basa en la determinación de un camioo de desplazamiento critico aproximado. Se calculan estos desplazamientos críticos imponiendo la condición de singularidad en una expresión aproximada de la matriz de rigidez tangen.te en el punto crítico. Este procedimiento implica un problema no lineal de autovalores. La carga crítica se obtiene a posteriori, de modo directo, utilizando la relación secante entre carga y desplazamiento. Se detalla este procedimiento y la forma explícita de la matriz secante Para elementos de sólido en dos y tres dimensiones. Los resultados obtenidos constatan la efectkidad del método propuesto para análisis de distintas tipologías estructurales con elementos finitos de barra articulada 3D y de sólidos 2D y 3D. A new technique for predicting structural instability points using the finite element method is presented. The approach is based on the estimation of the critical displacement pattern by writing an aproximation of the tangent stiffness singularity condition at the instability point. The critical load is subsequently computed by using a secant load-displacement relationship. Details of this procedure are given together with explicit forms of the secant stiffness matrix for finite element analysis of solids. The accuracy and effectiveness of the method are shown in the non linear analysis of severa1 two and three dimensional structures.

The monograph presents recent developments on the solution of high speed compressible flow problems using finite element and finite point (meshless) methods with adaptive refinement, techniques. This work treats two of the main problems of today's problems related to computational fluid dynamics. One problem dealt with is the assured accuracry of a numerical model, at least for the problems which are presented. The other problem which is addressed is the vast amount of time spent in generating (or regenerating) a mes in the design process.

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.

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.