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  • Mètodes numèrics en ciències aplicades i enginyeria

     Sarrate Ramos, Jose; Diez Mejia, Pedro; Rodriguez Ferran, Antonio; Fernandez Mendez, Sonia; Arias Vicente, Irene; Arroyo Balaguer, Marino; Parés Mariné, Núria; Muñoz Romero, Jose Javier; Discacciati, Marco; Zlotnik, Sergio; de Villardi de Montlaur, Adeline; Poblet Puig, Jordi; Shen, Yongxing; Huerta Cerezuela, Antonio
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  • Continuous-discontinuous modelling for quasi-brittle failure: propagating cracks in a regularised bulk.  Open access

     Tamayo Mas, Elena
    Universitat Politècnica de Catalunya
    Theses

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    En aquesta tesi, presentem una nova estratègia per tal de descriure el procés de fallida de materials quasi-fràgils, com ara el formigó. Típicament la simulació numèrica d'aquest procés s'ha dut a terme mitjançant models de dany o models de fractura. Els primers -models continus- descriuen la fractura com un procés de localització de deformacions on el dany creix i es propaga. Els models de fractura, en canvi, són models discontinus que introdueixen de manera explícita discontinuïtats en el camp de desplaçaments. Recentment s'han proposat estratègies que combinen aquestes dues teories clàssiques. Tot i que aquestes formulacions alternatives permeten simular millor el procés de fallida, encara queden alguns aspectes per aclarir, especialment pel que fa al canvi de models -de l'estratègia contínua a la discontínua.En aquesta tesi es presenta una nova estratègia contínua-discontínua. El nostre principal objectiu és proposar nous mètodes per tal de resoldre tres de les dificultats que presenten aquests models combinats: (1) solucionar la dependència patológica de la malla d'elements finits que presenten els models locals amb reblaniment; (2) determinar la trajectòria de la fissura i (3) assegurar-se que el canvi de models -delcontinu al discontinu- es fa de manera que les dues estratègies siguin energèticament equivalents.En primer lloc, ampliem l'ús -per tal de poder simular problemes dos i tres dimensionals- d'una estratègia alternativa que regularitza el reblaniment de les lleis de tensió-deformació. Aquí la no-localitat s'introdueix a nivell del camp de desplaçaments i no a través d'una variable interna com succeeix en les formulacions estàndards. Per aquest motiu, proposem noves condicions de contorn combinades per l'equació de regularització (pel camp de desplaçaments suavitzat). Tal com s'observa en diferents exemples dos i tres dimensionals, aquestes condicions permeten simular de manera físicament realista les primeres etapes del procés de fallida.En segon lloc, presentem una nova formulació combinada on les fissures es propaguen a través del medi regularitzat. Per tal de definir la trajectòria d'aquestes fissures, utilitzem un criteri geomètric, a diferència dels criteris mecànics clàssics. En particular, sigui D(x) un camp regularitzat de dany, les discontinuïtats es propaguen seguint la direcció marcada per l'eix mitjà de la isolínia (o isosuperfície mitjana en 3D) D(x) = D*. És a dir, utilitzem aquí aquesta eina geomètrica -molt emprada en d'altres aplicacions com ara l'anàlisi d'imatges, la visió artificial o la generació de malles- per tal de propagar les fissures. En aquest cas, donem també exemples dos i tres dimensionals.Finalment, proposem un nou criteri per tal d'estimar l'energia que l'estructura encara no ha dissipat en el moment en que canviem de model, per tal que pugui ser transferida a la fissura cohesiva. D'aquesta manera, s'assegura que l'estratègia contínua i la contínua-discontínua siguin energèticament equivalents. En comparació amb d'altres tècniques, aquesta estratègia té en compte les diferents branques de descàrrega dels models de dany i permet estimar de manera més precisa l'energia que cal transmetre. Per tal de mostrar aquest balanç energètic es duen a terme diferents exemples en una i dues dimensions.

    A new strategy to describe failure of quasi-brittle materials -concrete, for example- is presented. Traditionally, numerical simulation of quasi-brittle failure has been tackled from two different points of view: damage mechanics and fracture mechanics. The former, which belongs to the family of continuous models, describes fracture as a process of strain localisation and damage growth. The latter, which falls in the family of discontinuous models, explicitly introduces displacement discontinuities. Recently, some new approaches that merge these two classical theories have been devised. Although these combined approaches allow a better characterisation of the whole failure process, there are still some issues that need to be addressed, specially regarding the model switching -from the continuous to the continuous-discontinuous strategy. The goal of this thesis is to present a new contribution in this direction. Our main concern is to properly account for the three main difficulties that emerge when dealing with combined strategies: (1) the pathological mesh-dependence exhibited by local softening models needs to be corrected; (2) the crack-path location has to be determined and (3) the switching from the continuous to the continuous-discontinuous strategy should be done in such a way that the two approaches are energetically equivalent. First, we extend the applicability to a two- and three-dimensional setting of an alternative approach to regularise strain-softening -where non-locality is introduced at the level of displacements rather than some internal variable. To this end, we propose new combined boundary conditions for the regularisation equation (for the smoothed displacement field). As illustrated with different two- and three-dimensional examples, these boundary conditions allow to obtain physical realistic results for the first stages of the failure process. Second, we present a new combined formulation that allows the propagation of cracks through a regularised bulk. To define the crack-path, instead of the classical mechanical criteria, we propose to use a geometrical criterion. More specifically, given a regularised damage field D(x), the discontinuity propagates following the direction dictated by the medial axis of the isoline (or isosurface in 3D) D(x) = D*. That is, a geometric tool widely used for image analysis, computer vision applications or mesh generation purposes is used here to locate cracks. We illustrate the capabilities of this new approach by carrying out different two- and three-dimensional numerical tests. Last, we propose a new criterion to estimate the energy not yet dissipated by the bulk when switching models, so it can be transferred to the cohesive crack. This ensures that the continuous and the continuous-discontinuous strategies are energetically equivalent. Compared to other existing techniques, we present a strategy that accounts for the different unloading branches of damage models thus better estimating the energy that has to be transferred. We illustrate the performance of this technique with one- and two-dimensional examples.

    En aquesta tesi, presentem una nova estratègia per tal de descriure el procés de fallida de materials quasi-fràgils, com ara el formigó. Típicament la simulació numèrica d'aquest procés s'ha dut a terme mitjançant models de dany o models de fractura. Els primers |models continus| descriuen la fractura com un procés de localització de deformacions on el dany creix i es propaga. Els models de fractura, en canvi, són models discontinus que introdueixen de manera explícita discontinuïtats en el camp de desplaçaments. Recentment s'han proposat estratègies que combinen aquestes dues teories clàssiques. Tot i que aquestes formulacions alternatives permeten simular millor el procés de fallida, encara queden alguns aspectes per aclarir, especialment pel que fa al canvi de models |de l’estratègia contínua a la discontínua. En aquesta tesi es presenta una nova estratègia contínua-discontínua. El nostre principal objectiu és proposar nous mètodes per tal de resoldre tres de les dificultats que presenten aquests models combinats: (1) solucionar la dependència patològica de la malla d'elements finits que presenten els models locals amb reblaniment; (2) determinar la trajectòria de la fissura i (3) assegurar-se que el canvi de models del continu al discontinu| es fa de manera que les dues estratègies siguin energèticament equivalents. En primer lloc, ampliem l’ús |per tal de poder simular problemes dos i tres dimensionals d'una estratègia alternativa que regularitza el reblaniment de les lleis de tensió-deformació. Aquí la no-localitat s'introdueix a nivell del camp de desplaçaments i no a través d'una variable interna com succeeix en les formulacions estàndards. Per aquest motiu, proposem noves condicions de contorn combinades per l’equació de regularització (pel camp de desplaçaments suavitzat). Tal com s'observa en diferents exemples dos i tres dimensionals, aquestes condicions permeten simular de manera físicament realista les primeres etapes del procés de fallida. En segon lloc, presentem una nova formulació combinada on les fissures es propaguen a través del medi regularitzat. Per tal de definir la trajectòria d'aquestes fissures, utilitzem un criteri geomètric, a diferència dels criteris mecànics clàssics. En particular, sigui D(x) un camp regularitzat de dany, les discontinuats es propaguen seguint la direcció marcada per l'eix mitjà de la isolínia (o isosuperfície mitjana en 3D) D(x) = D_. _Es a dir, utilitzem aquí aquesta eina geomètrica, molt emprada en d'altres aplicacions com ara l’anàlisi d'imatges, la visió artificial o la generació de malles| per tal de propagar les fissures. En aquest cas, donem també exemples dos i tres dimensionals. Finalment, proposem un nou criteri per tal d'estimar l'energia que l'estructura encara no ha dissipat en el moment en que canviem de model, per tal que pugui ser transferida a la fissura cohesiva. D'aquesta manera, s'assegura que l’estratègia contínua i la contínua-discontínua siguin energèticament equivalents. En comparació amb d'altres tècniques, aquesta estratègia té en compte les diferents branques de descàrrega dels models de dany i permet estimar de manera més precisa l'energia que cal transmetre. Per tal de mostrar aquest balanç energètic es duen a terme diferents exemples en una i dues dimensions.

  • Efficient models for building acoustics: combining deterministic and statistical methods  Open access

     Diaz Cereceda, Cristina
    Universitat Politècnica de Catalunya
    Theses

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    La modelización de problemas vibroacústicos en el ámbito de la edificación supone un desafío debido al gran tamaño de los dominios y al amplio rango frecuencial requerido por las normativas. Las técnicas numéricas estándares, como por ejemplo el método de los elementos finitos (MEF), fallan al tratar de alcanzar las frecuencias más altas, puesto que el tamaño de elemento requerido es muy inferior a las dimensiones del problema y el coste computacional asociado es excesivo para tratarse de un cálculo tan cotidiano.El análisis estadístico de energía (SEA) es un marco de análisis de problemas vibroacústicos basado en el comportamiento de las ondas a altas frecuencias. Trata directamente con magnitudes promediadas, tal y como requieren las normativas, y su coste computacional es muy bajo. Sin embargo, presenta numerosas limitaciones a la hora de analizar estructuras reales. Habitualmente la definición del modelo SEA necesita ser complementada con experimentos u otros datos añadidos.Esta tesis se centra en la modelización de problemas de acústica de la edificación con un coste computacional razonable. En ese sentido se han seguido dos líneas fundamentales de investigación.En la primera parte de la tesis se analiza el potencial uso de simulaciones numéricas para extender la aplicabilidad del SEA. En particular, se tratan tres aspectos diferentes: en primer lugar, se desarrolla una metodología sistemática para la estimación de factores de acoplamiento a partir de simulaciones numéricas. Estos factores se estiman a partir de pequeñas simulaciones deterministas y posteriormente se aplican para la resolución de problemas mayores con SEA. En segundo lugar, se presenta un modelo basado en el SEA para acoplamientos no conservativos, así como una estrategia para obtener los factores de acoplamiento conservativos y no conservativos a partir de simulaciones numéricas. Finalmente, se propone una metodología para la identificación de subsistemas SEA con análisis modal. Esta técnica consiste en realizar un análisis cluster basado en los modos propios del problema, y permite la detección de subdivisiones óptimas para dominios complejos, incluso si varios subsistemas coexisten en la misma región geométrica.En la segunda parte de la tesis, se analiza la transmisión sonora a través de paredes dobles desde diferentes puntos de vista, por ser éste un ejemplo paradigmático de las complejidades asociadas a las simulaciones vibroacústicas. En primer lugar, se presenta una compilación de modelos clásicos para este problema. A continuación, se propone la utilización del método de las capas finitas como una nueva manera de discretizar el campo de presiones en la cavidad interior de las paredes dobles, especialmente cuando esta se encuentra parcialmente llena con material absorbente. Este método combina una discretización de tipo MEF en la dirección perpendicular a la pared con funciones trigonométricas en las dos direcciones coplanarias con la misma. El coste computacional de esta técnica es inferior al del MEF, pero también permite la aplicación de las condiciones de continuidad y equilibrio entre capas fluidas. Seguidamente, esta técnica se compara tanto con datos experimentales como con otros modelos predictivos, con objeto de verificar la influencia de distintas simplificaciones habituales en estos modelos.Por último, se presenta la combinación de métodos deterministas y estadísticos como una posible solución para la modelización de problemas vibroacústicos compuestos por paredes dobles y otros elementos. El análsis global se realiza con SEA, pero se utilizan simulaciones numéricas de pequeñas partes del problema para obtener los parámetros necesarios. La combinación de ambas técnicas permite la realización de simulaciones con un coste computacional razonable.

    Modelling vibroacoustic problems in the field of building design is a challenging problem due to the large size of the domains and the wide frequency range required by regulations. Standard numerical techniques, for instance finite element methods (FEM), fail when trying to reach the highest frequencies. The required element size is too small compared to the problem dimensions and the computational cost becomes unaffordable for such an everyday calculation. Statistical energy analysis (SEA) is a framework of analysis for vibroacoustic problems, based on the wave behaviour at high frequencies. It works directly with averaged magnitudes, which is in fact what regulations require, and its computational cost is very low. However, this simplified approach presents several limitations when dealing with real-life structures. Experiments or other complementary data are often required to complete the definition of the SEA model. This thesis deals with the modelling of building acoustic problems with a reasonable computational cost. In this sense, two main research lines have been followed. In the first part of the thesis, the potential of numerical simulations for extending the SEA applicability is analysed. In particular, three main points are addressed: first, a systematic methodology for the estimation of coupling loss factors from numerical simulations is developed. These factors are estimated from small deterministic simulations, and then applied for solving larger problems with SEA. Then, an SEA-like model for non-conservative couplings is presented, and a strategy for obtaining conservative and non-conservative coupling loss factors from numerical simulations is developed. Finally, a methodology for identifying SEA subsystems with modal analysis is proposed. This technique consists in performing a cluster analysis based on the problem eigenmodes. It allows detecting optimal SEA subdivisions for complex domains, even when two subsystems coexist in the same region of the geometry. In the second part of the thesis, the sound transmission through double walls is analysed from different points of view, as a representative example of the complexities of vibroacoustic simulations. First, a compilation of classical approaches to this problem is presented. Then, the finite layer method is proposed as a new way of discretising the pressure field in the cavity inside double walls, especially when it is partially filled with an absorbing material. This method combines a FEM-like discretisation in the direction perpendicular to the wall with trigonometric functions in the two in-plane directions. This approach has less computational cost than FEM but allows the enforcement of continuity and equilibrium between fluid layers. It is compared with experimental data and also with other prediction models in order to check the influence of commonly assumed simplifications. Finally, a combination of deterministic and statistical methods is presented as a possible solution for dealing with vibroacoustic problems consisting of double walls and other elements. The global analysis is performed with SEA, and numerical simulations of small parts of the problem are used to obtain the required parameters. Combining these techniques, a realistic simulation of the vibroacoustic problem can be performed with a reasonable computational cost.

  • A finite element strategy coupling a gradient-enhanced damage model and cohesive cracks for quasi-brittle materials

     Tamayo Mas, Elena; Rodriguez Ferran, Antonio
    International Conference on Computational Plasticity Fundamentals and Applications
    p. 376-387
    Presentation's date: 2013-09
    Presentation of work at congresses

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    A new combined strategy to describe failure of quasi-brittle materials is presented thus allowing the complete description of the process, from initiation of damage to crack propagation. For the early stages of the process, and in order to overcome the well-known problems characterising local descriptions of damage (e.g. mesh-dependence), a gradient-enhanced model based on smoothed displacements is employed. In order to deal with material separation, this continuous description is coupled to a cohesive crack when damage parameter exceeds a critical value. Some difficulties may arise when dealing with the transition from regularised damage models to evolving cracks: crack initiation, crack-path direction, energetic equivalence... In this work, a discrete cohesive crack is introduced when the damage parameter exceeds a critical value. On the one hand, and to determine the crack-path direction, the medial axis of the already damaged profile is computed. That is, a geometric tool widely used in the computer graphics field is used here to track the crack surface. Since this technique is exclusively based on the shape of the regularised damage profile, no mesh sensitivity is observed when determining the crack direction. On the other hand, and to define the cohesive law, an energy balance is imposed thus ensuring that the fracture energy not yet dissipated in the damage zone is transferred to the crack.

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    Pushing SEA beyond its limits: a model for real building structures  Open access

     Diaz Cereceda, Cristina; Poblet Puig, Jordi; Rodriguez Ferran, Antonio
    International Congress and Exposition on Noise Control Engineering
    p. 1-9
    Presentation's date: 2013-09-18
    Presentation of work at congresses

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    The main challenge for models of building acoustics is being able to consider all the geometrical and physical details of real structures with a reasonable computational cost for high frequencies. The SEA (Statistical Energy Analysis) framework is suitable for these frequencies, but presents some difficulties for dealing with complex structural configurations. For instance, modelling absorbing materials with SEA is an open issue, since they are neither reverberant subsystems nor conservative couplings. In this work, a model to account for absorbing materials with a SEA-like approach is performed. It is obtained by analogy with an electrical circuit. This approach is combined with numerical simulations in order to solve vibroacoustic problems in real structural configurations (including complex geometries or dissipative connections) throughout the entire frequency range required by regulations. The proposed technique is applied to modelling the sound insulation of double walls. These walls consist of two leaves of plasterboard connected through metallic studs and filled with a layer of absorbing material. The combination of numerical simulations and SEA arises as a good technique for modelling the acoustic behaviour of real life structures with an affordable computational cost.

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    An energy model for the acoustic insulation of absorbing materials  Open access

     Diaz Cereceda, Cristina; Poblet Puig, Jordi; Rodriguez Ferran, Antonio
    Congreso de Métodos Numéricos en Ingeniería
    p. 1-13
    Presentation's date: 2013-06-25
    Presentation of work at congresses

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    In this work an energy model for the acoustic insulation of absorbing ma- terials is shown. This model is an extension of Statistical Energy Analysis (SEA) [1] in order to account for the effect of non-conservative connections [2, 3]. The energy-based approach allows to solve sound insulation problems in large domains (such as those in building acoustics) in an efficient way for the whole frequency range required by regulations (50-5000 Hz). In particular, this approach is applied here for the study of the insulating behaviour of an absorbing layer (mineral wool) filling the cavity of a double wall. The absorbing layer is considered as a non-conservative connection between the two leaves of the wall. This model is combined with detailed numerical computations to obtain the loss factors associated to the connection. With these parameters, a combined system including the transmission between rooms and double walls can be stated. Obtained results show that absorbing layers can be modelled as non-conservative cou- plings and incorporated in an SEA-like system to compute the sound insulation in buildings successfully.

  • Influence of the microstructure of micro-perforated plates in the emergence of band gaps

     Diaz Cereceda, Cristina; Askes, Harm; Rodriguez Ferran, Antonio
    Congreso de Métodos Numéricos en Ingeniería
    p. 1-13
    Presentation's date: 2013-06-25
    Presentation of work at congresses

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    Wave propagation through solids is strongly influenced by th eir microstruc- ture, especially if this microstructure is periodic. This u sually leads to the emergence of band gaps, i.e. frequency ranges that cannot propagate thro ugh the material [1]. These phenomena can be taken into account with nonlocal continuum models. They outperform the classical elastic models in the sense that they can captu re dispersive behaviours and band gaps within a continuous medium [2]. The addition of a hi gher order inertia term, characterised by a certain intrinsic length, leads to the di spersion of the waves propagated through the solid medium. Microperforated plates (MPP) are an example of solid ele- ments with periodic microstructure. In this case the micros tructure consists of a set of holes distributed throughout the plate. In this work, the in fluence of the microstructural properties of the MPP (hole size, inter-hole distance and ho le pattern) on the emergence of band gaps is studied. Moreover, an equivalent nonlocal co ntinuum model for the MPP is developed, relating the plate microstructure with the ch aracteristic length of the higher inertia term.

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    An SEA-like model for double walls filled with absorbing materials  Open access

     Diaz Cereceda, Cristina; Poblet Puig, Jordi; Rodriguez Ferran, Antonio
    Congreso Ibero-americano de Acústica
    p. 127
    Presentation's date: 2012-10-03
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    Modelling absorbing materials with statistical energy analysis (SEA) is an open issue. They are neither reverberant subsystems nor conservative couplings. The absorbing material layers located inside the cavities of double walls should be treated as non-conservative couplings between the wall leaves. However, the standard SEA formulation cannot take into account non-conservative couplings. In this work, an equivalent circuit analogy is used to deduce how to introduce these couplings in an SEA-like system. Besides, a technique for obtaining the SEA-like factors associated to a double wall filled with absorbing material is presented. These factors are computed from numerical simulations of the vibroacoustic leaf-absorbing material-leaf system and applied for solving larger problems with SEA.

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    A numerical technique for obtaining SEA coupling loss factors in double walls  Open access

     Diaz Cereceda, Cristina; Poblet Puig, Jordi; Rodriguez Ferran, Antonio
    Congreso Ibero-americano de Acústica
    p. 1-12
    Presentation's date: 2012-10-03
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    Double walls usually consist of two leaves of material connected by steel studs. Aside from improving the structural performance, studs create a vibration transmission path which connects the two leaves. There is interest in reliable models of the acoustic performance of these structures, for the frequency range required in regulations. Statistical energy analysis allows reaching high frequencies with a low computational cost. However, the best SEA approach for modelling double walls is not clear in the literature. The cavity may be considered as a subsystem or treated as a connecting device between the two leaves. The effect of the cavity is also often neglected compared to the coupling provided by the studs. In this work, numerical techniques are used to evaluate these approaches and to define a combined deterministic–statistical approach that accounts for all the transmission phenomena.

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    A geometric bridge between regularised damage and energetically equivalent cracks  Open access

     Tamayo Mas, Elena; Rodriguez Ferran, Antonio
    European Congress on Computational Methods in Applied Sciences and Engineering
    p. 1-13
    Presentation's date: 2012-09-10
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    In order to achieve a better characterisation of a whole failure process, models which combine damage and fracture mechanics have recently been proposed. Here, a new combined methodology is presented: in order to describe damage inception and its diffuse propagation, a gradient-enhanced continuum model based on smoothed displacements is used, which is coupled to a discontinuous one to describe the final stages of the process. Special emphasis should be placed on the difficulties concerning the transition between continuous damage growth and fracture. On the one hand, and in order to conserve the energy dissipation through the change of models, an appropriate cohesive law must be defined. In this paper, the proposed technique to define this law is explained. On the other hand, the direction of the crack path should be determined. Here, a new strategy is proposed: the discontinuity is propagated following the direction dictated by the medial axis of the damaged domain. That is, a geometric tool, widely used in the computer graphics field, is used here to locate cracks.

  • Sound transmission through double walls: statistical and deterministic models

     Diaz Cereceda, Cristina; Poblet Puig, Jordi; Rodriguez Ferran, Antonio
    European Conference on Noise Control
    p. 583-588
    Presentation's date: 2012-06-11
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  • Discontinuous failure in a gradient-enhanced continuous damage model: a regularised displacement framework

     Tamayo Mas, Elena; Rodriguez Ferran, Antonio
    International Conference on Computational Plasticity
    p. 1-12
    Presentation's date: 2011-09-08
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  • Time domain analysis of impact noise

     Nouri, N.; Ziaei-Rad, N; Diaz Cereceda, Cristina; Poblet Puig, Jordi; Rodriguez Ferran, Antonio
    Congreso en Métodos Numéricos em Engenharia
    p. 1-12
    Presentation's date: 2011-06-15
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  • Obtaining SEA (Statistical Energy Analysis) parameters by means of numerical models

     Diaz Cereceda, Cristina; Poblet Puig, Jordi; Rodriguez Ferran, Antonio
    Congreso en Métodos Numéricos em Engenharia
    p. 13-
    Presentation's date: 2011-06-16
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  • Continuous-discontinuous simulation of failure with smoothed displacements: from damage to energetically equivalent cracks

     Tamayo Mas, Elena; Rodriguez Ferran, Antonio
    Congreso en Métodos Numéricos em Engenharia
    p. 1-15
    Presentation's date: 2011-06-14
    Presentation of work at congresses

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  • Boundary conditions for the displacement-based damage model

     Tamayo Mas, Elena; Rodriguez Ferran, Antonio
    International Conference on Computational Modeling of Fracture and Failure of Materials and Structures
    p. 294
    Presentation's date: 2011-06-06
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  • Controlling the critical time step with the bi-penalty method

     Hetherington, Jack; Rodriguez Ferran, Antonio; Askes, Harm
    Computational Methods in Structural Dynamics and Earthquake Engineering
    p. 4439-4444
    Presentation's date: 2011-05-26
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  • Controlling the critical time step via the bipenalty method

     Hetherington, Jack; Rodriguez Ferran, Antonio; Askes, Harm
    UK National Conference on Computational Mechanics in Engineering
    p. 157
    Presentation's date: 2011-04-05
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  • The Bipenalty method for explicit time integration

     Askes, Harm; Caramés-Saddler, M.; Rodriguez Ferran, Antonio
    International Conference on Computational Structures Technology
    p. 1-9
    DOI: 10.4203/ccp.93.339
    Presentation's date: 2010-09-14
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    Error estimation in vibroacoustic problems solved by means of finite elements  Open access

     Poblet Puig, Jordi; Rodriguez Ferran, Antonio
    International Congress and Exposition on Noise Control Engineering
    p. 1-8
    Presentation's date: 2010-06-16
    Presentation of work at congresses

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    The vibroacoustic equations can be solved by means of the finite element method. A discretisation of the structure and the acoustic domains is required and highly influences the quality of the numerical solution. There exist meshing criteria (a priori error estimators) for the case of the Helmholtz equation but these studies have not focused their attention in the case of the vibroacoustic problem. The fluid structure interaction represents a new source of numerical errors and meshes in the interaction zone should be designed by not only taking into account the physical properties of the acoustic medium but also the mechanical properties of the structure. The goal of the work is to obtain an a priori error estimation criterion for the vibroacoustic problem and Illustrate its efficiency by means of numerical experiments.

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    A continuous-discontinous model for softening and cracking based on non-local displacements  Open access

     Tamayo Mas, Elena; Rodriguez Ferran, Antonio
    European Conference on Computational Mechanics
    p. 1-13
    Presentation's date: 2010-05-19
    Presentation of work at congresses

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    A continuous-discontinuous model to simulate numerically an entire failure process is presented. Crack inception and its propagation is modelled by means of a gradient non-local model based on non-local displacements. To simulate properly the final stages of the process, a discrete crack approach (X-FEM) is used, where both local and non-local displacements are modelled as discontinuous fields. In this paper, this new combined approach is studied in detail and one- and two-dimensional examples are carried out to validate it.

  • MÈTODES NUMÈRICS EN CIÈNCIES APLICADES I ENGINYERIA

     Roca Navarro, Francisco Javier; Giorgiani, Giorgio; Zlotnik, Sergio; Fernandez Mendez, Sonia; Rodriguez Ferran, Antonio; Muñoz Romero, Jose Javier; Arias Vicente, Irene; de Villardi de Montlaur, Adeline; Sarrate Ramos, Jose; Diez Mejia, Pedro; Arroyo Balaguer, Marino; Sevilla Cardenas, Ruben; Parés Mariné, Núria; Casoni Rero, Eva; Ruiz Girones, Eloi; Modesto Galende, David; Millan, Raul Daniel; Abdollahi Hosnijeh, Amir; Steffens, Lindaura Maria; Discacciati, Marco; Shen, Yongxing; Rahimi Lenji, Mohammad; Tamayo Mas, Elena; Diaz Cereceda, Cristina; Prat Robles, David; Verdugo Rojano, Francesc; Zhang, Kuan; Estela Carbonell, M. Rosa; Peco Regales, Christian; Pérez Foguet, Agustí; Angeloski, Aleksandar; Gargallo Peiró, Abel; Huerta Cerezuela, Antonio
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  • Un modelo diferencial de histeresis para paredes de cortante en estructuras de acero conformado en frío

     Pastor, N.; Rodriguez Ferran, Antonio; Arnedo Pena, Alfredo Bernardo
    Congreso de Métodos Numéricos en Ingeniería
    p. 156
    Presentation's date: 2009-06-29
    Presentation of work at congresses

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  • Modelización Numérica de ruido de impacto

     Diaz Cereceda, Cristina; Poblet Puig, Jordi; Rodriguez Ferran, Antonio
    Congreso de Métodos Numéricos en Ingeniería
    p. 328
    Presentation's date: 2009-06-29
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  • Modelo continuo-discontinuo del fallo material basado en desplazamientos no-locales

     Tamayo, E; Rodriguez Ferran, Antonio
    Congreso de Métodos Numéricos en Ingeniería
    p. 273
    Presentation's date: 2009-06-29
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  • Análisis y aplicación del método de Gauss-Seidel por bloques en vibroacústica: Transmisión de ruido

     Poblet Puig, Jordi; Rodriguez Ferran, Antonio
    Congreso de Métodos Numéricos en Ingeniería
    p. 319
    Presentation's date: 2009-06-29
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  • MODELOS NUMERICOS PREDICTORES PARA LA GESTION MEDIOAMBIENTAL

     Roca Navarro, Francisco Javier; Rodriguez Ferran, Antonio; Fernandez Mendez, Sonia; Sala Lardies, Esther; Pérez Foguet, Agustí
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  • A continuous-discontinuous model for softening and cracking based on non-local gradient elasticity

     Rodriguez Ferran, Antonio; Tamayo Mas, Elena; Bennett, T.; Askes, Harm
    International Conference on Computational Plasticity Fundamentals and Applications
    p. 1-4
    Presentation's date: 2009
    Presentation of work at congresses

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  • Numerical modelling of sound transmission in lightweight structures

     Poblet Puig, Jordi
    Barcelona School of Civil Engineering (ETSECCPB), Universitat Politècnica de Catalunya
    Theses

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  • Trabajos topográficos en un proyecto de cooperación en Tanzania

     Puig Polo, Carolina; Rodriguez Ferran, Antonio; Ribot, Mineke; Casas, Irene; Jiménez, Alejandro; Muñoz, David
    Congreso Nacional de Topografía y Cartografía
    Presentation's date: 2008-02-18
    Presentation of work at congresses

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    Actualmente, la Organización No Gubernamental (ONG) Ingeniería Sin Fronteras – Asociación para el Desarrollo (ISF-ApD) está llevando a cabo diferentes proyectos hidrosanitarios en Tanzania, con el objeto de mejorar el acceso a los servicios básicos de agua y saneamiento de la población. La Universitat Politècnica de Catalunya (UPC) está colaborando con ISF-ApD en las tareas de recopilación de información espacial, principalmente en la captura de datos con equipos GPS y su integración con la cartografía existente, analizando las alternativas disponibles para publicar en la web los datos geográficos obtenidos para su reutilización posterior. En esta comunicación se hace una descripción de las metodologías aplicadas y se aborda la cuestión de cómo aprovechar las últimas tendencias de Neocartografía, basadas en mashups colaborativos y servicios de mapas, para publicar en Internet los datos cartográficos resultantes y permitir su posterior explotación en todo tipo de proyectos y trabajos sobre el territorio. El Instituto Geográfico Nacional ha iniciado el procedimiento institucional para poder colaborar aportando equipamiento e infraestructura tecnológica.

  • Modeling, identification, and semi-active control of a large-scale magnetorheological fluid damper

     Rodriguez Ferran, Antonio; Iwata, N; Ikhouane, Fayçal; Rodellar Benede, Jose Julian
    Third International Conference Smart Materials, Structures and Systems
    p. 2-9
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  • Identification of a magnetorheological damper: Theory and experiments

     Rodriguez Ferran, Antonio; Ikhouane, Fayçal; Rodellar Benede, Jose Julian; Luo Ren, Ningsu
    World Congress of the International Federation of Automatic Control
    p. 7877
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  • Modelización numérica de estructuras e infraestructuras: diseño, durabilidad y estados limite

     Muñoz Romero, Jose Javier; Huerta Cerezuela, Antonio; Sarrate Ramos, Jose; Parés Mariné, Núria; Vidal Segui, Yolanda; Roca Navarro, Francisco Javier; Poblet Puig, Jordi; Rodriguez Ferran, Antonio
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  • A symetric sparse approximate inverse preconditioner for block tridiagonal

     Sandoval, M L; Rodriguez Ferran, Antonio
    2007 International Conference On Preconditioning Techniques For Large Sparse Matrix Problems In Scientific And Industrial Applications
    p. 87-88
    Presentation of work at congresses

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  • Diseny Workpack per a una Casa d'Acer

     Rodriguez Ferran, Antonio; Huerta Cerezuela, Antonio; Diez Mejia, Pedro; Sarrate Ramos, Jose
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  • Models numérics per a la diagnòsis i predicció de la contaminació atmosférica.

     Pérez Foguet, Agustí; Sala Lardies, Esther; Rodriguez Ferran, Antonio; Fernandez Mendez, Sonia
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  • Regularized softening models based on nonlocal displacements

     Rodriguez Ferran, Antonio; Askes, A
    International Conference on Computational Fractures and Failure of Materials and Structures
    p. 109
    Presentation of work at congresses

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  • Métodos iterativos eficientes para problemas de convección-difusión transitorios  Open access

     Sandoval Solis, M. Luisa
    Department of Applied Mathematics III, Universitat Politècnica de Catalunya
    Theses

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    Diversos procesos naturales e industriales de interés medioambiental se modelan a través de la ecuación de convección-difusión-reacción transitoria. Dos aplicaciones tecnológicas que han motivado esta tesis son el funcionamiento de filtros de carbón activo y la dispersión de contaminantes en la atmósfera. Para que la modelización numérica de estos problemas sea eficaz es indispensable contar con un solver lineal eficiente para resolver los sistemas de ecuaciones obtenidos al discretizar la ecuación en derivadas parciales, mediante elementos finitos.Por ello, el objetivo de esta tesis es resolver de forma eficiente los grandes sistemas de ecuaciones, simétricos definidos positivos (SDP), tipo sparse asociados a los problemas de convección-difusión transitorios. Con este fin se estudian los precondicionadores tanto explícitos como implícitos, así como los métodos de descomposición de dominios (DD). La tesis se estructura en tres partes. En la primera se elabora un análisis computacional detallado del comportamiento de dos familias de factorizaciones incompletas de Cholesky (FIC): de memoria prescrita y de umbral. Estas técnicas se utilizan para precondicionar el método iterativo de gradientes conjugados (PCG). En la segunda parte se construye una inversa aproximada sparse simétrica (SSPAI) basada en la minimización en la norma de Frobenius. El precondicionador explícito se diseña para resolver en paralelo grandes sistemas de ecuaciones sparse, SDP, tridiagonales por bloques con múltiples lados derechos. Finalmente, se desarrolla el método multiplicativo de Schwarz (MSM) en dominios activos, es decir, DD solapados con la innovación de activar y desactivar dominios. Se estudia el comportamiento de esta estrategia al resolver los subproblemas mediante: (1) el método directo de Cholesky y (2) PCG + FIC de umbral.De los resultados numéricos presentados se concluye que es preferible utilizar el método directo de Cholesky para sistemas con menos de 30,000 variables. Para sistemas mayores y hasta 80,000 incógnitas se sugiere emplear una FIC de umbral. Y para sistemas aún más grandes, el MSM en dominios activos + PCG + FIC de umbral propuesto es el más eficiente usando un solo procesador. Por su parte, la SSPAI presentada podría superar a las FIC de umbral si se trabaja en paralelo.

    Many natural and industrial processes of environmental interest are modeled through the transient convection-diffusion-reaction equation. Two technological applications that have motivated this thesis are the operation of activated-carbon filters and the dispersion of pollutants in the atmosphere. In order to ensure the effectiveness of numerical modeling of these problems it is necessary to have an efficient linear solver to solve the systems obtained when discretizing the partial differential equation by means of the finite element method.For that reason, the goal of this thesis is to solve in an efficient way the large sparse symmetric positive definite (SPD) systems of linear equations associated to the transient convection-diffusion problems. With this purpose, we have studied the explicit and implicit preconditioners, as well as domain decomposition (DD) methods.The thesis is structured in three parts. In the first one we have elaborated a detailed analysis of the numerical performance of two families of incomplete Cholesky factorizations (ICF): drop tolerance and prescribed-memory strategies. These techniques are used to precondition conjugate gradient iterations (PCG). In the second part a symmetric sparse approximate inverse (SSPAI) based on the minimization of the Frobenius norm is built. The explicit preconditioner is designed to solve in parallel large block tridiagonal SPD systems with multiple right hand sides.Finally, the multiplicative Schwarz method (MSM) in active domains is developed, which consists of overlapped domain decomposition with the innovation to activate and to deactivate domains. The behavior of this strategy is studied when solving the subproblems by means of: (1) the Cholesky direct solver and (2) PCG + drop-tolerance ICF. According to our numerical experiments we conclude that it is preferable to use the Cholesky direct solver for systems with less than 30,000 variables. For larger systems and up to 80,000 equations we suggest to use a drop tolerance ICF. And for even lager systems, the proposed MSM in active domains is the most efficient when using a single processor. On the other hand, the presented SSPAI could overcome the drop-tolerance ICF if one works in parallel.

  • Numerical modelling of the seismic behaviour of cold-formed steel structures

     Pastor Torrente, Natividad
    Department of Applied Mathematics III, Universitat Politècnica de Catalunya
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  • Nonlocal ineslasticity based on nonlocal displacements

     Rodriguez Ferran, Antonio
    ACME / ISSEC 2006 MEETING
    p. 3-6
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  • Desarrollo de prototipos de estructura metálica con propiedades acústicas y de vibración mejoradas

     Rodriguez Ferran, Antonio; Vidal Segui, Yolanda
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  • Ajudes per a la financiació de grups d'investigació de Catalunya. (Grup consolidat d'investigació en el marc del Plan d'Investigació e Innovació de Catalunya 2005-2008)

     Huerta Cerezuela, Antonio; Sala Lardies, Esther; Rodriguez Ferran, Antonio; Arias Vicente, Irene; Pérez Foguet, Agustí; Arroyo Balaguer, Marino; Fernandez Mendez, Sonia; Sarrate Ramos, Jose
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  • LIGHTFRAME. Desenvolupament de prototipus d'estructura metálica amb propietats acústiques i de vibració millorades (2005-2007)

     Rodriguez Ferran, Antonio; Huerta Cerezuela, Antonio; Diez Mejia, Pedro; Pérez Foguet, Agustí; Fernandez Mendez, Sonia; Sarrate Ramos, Jose
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  • Numerical modeling of sound transmission in double walls

     Poblet Puig, Jordi; Vilaseca Cabo, Roger; Rodriguez Ferran, Antonio
    The European Conference on Noise Control
    p. 1-6
    Presentation of work at congresses

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    Numerical models for the calculation of sound transmission in double walls are presented. The finite element method (FEM) or analytical solutions (for rectangular domains) are used for the acoustic part of the problem while the wall vibration is solved by means of structural finite elements. The vibroacoustic problem is formulated in the frequency range: the acoustic domains (rooms) are described by the Helmholtz equation, the absorbent materials as an equivalent fluid and the structures by means of dynamic linear elasticity. The acoustic and structural parts of the problem are coupled. The influence of the stiffness and spacing of the studs on the performance of lightweight walls is studied. The studs have been modelled with beam finite elements or by means of mechanical constraints. The effect of the boundary conditions of the walls and its dimensions are also analyzed.

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    Experimental and numerical characterization of metallic studs  Open access

     Poblet Puig, Jordi; Guigou-Carter, Catherine; Villot, Michel; Rodriguez Ferran, Antonio
    The European Conference on Noise Control
    p. 1-6
    Presentation of work at congresses

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    In this paper, the characterization of metallic studs used to mount lightweight double wall systems is studied both experimentally and numerically. The metallic studs are usually considered by introducing translational and rotational springs to couple the plasterboards composing the double wall. Therefore, the characterization involves determining these spring characteristics. The performance of this type of lightweight double wall in terms of sound transmission is presented in a companion paper. Different experimental setups have been investigated to determine the equivalent translational and rotational spring values. These experimental setups are described and involve the measurement of an input mobility. A finite element model of the laboratory tests has been developed. Shell and massive finite elements are employed in order to reproduce the experimental setups. A comparison of the measured and numerical results is shown. The FEM modelling is intended to help in developing new type of studs for double walls in order to obtain better sound transmission performance.

  • DPI2004-0103-E Disseny acústic d'estructures lleugeres d'acer.

     Rodriguez Ferran, Antonio; Pérez Foguet, Agustí; Romeu Garbi, Jordi
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