Oller Martinez, Sergio Horacio
Total activity: 566
Areas of expertise
Prof. Structures and Continuum Mechanics
h index
26
Professional category
University professor
Doctoral courses
Dr. Ingeniero de Caminos, Canales y Puertos
University degree
Ingeniero en Construcciones (Homologado al Título de Ing. de Caminos)
Postgraduated qualification
Especialidad en Métodos Avanzados de Análisis y Diseño de Estructuras.
Research group
(MC)2 - Group of Computational Mechanics on Continuous Medium
Department
Department of Strength of Materials and Structural Engineering
School
Barcelona School of Civil Engineering (ETSECCPB)
Associated research bodies
CIMNE. Centre Internacional de Mètodes Numèrics en Enginyeria Open in new window
E-mail
sergio.ollerupc.edu
Contact details
UPC directory Open in new window
Orcid
0000-0002-5203-8903 Open in new window
Scopus Author ID
7003881173 Open in new window
Links of interest
Google Scholar Open in new window
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1 to 50 of 566 results
  • Modelización del comportamiento de estructuras mediante la teoría de homogeneización

     Quinteros, Ricardo D.
    National University of Salta
    Theses

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    Esta tesis se focaliza en el análisis y desarrollo de técnicas de homogenización ad-hoc para resolver el problema de representar el comportamiento estructural de muros de mampostería, aprovechando la configuración periódica que sus materiales y distribución le confieren. Mediante estas técnicas, es posible derivar el comportamiento global de la estructura a partir del comportamiento de los materiales constituyentes (ladrillo y mortero) adoptando modelos constitutivos diferentes para cada uno de ellos. Se realizan diversos ejemplos de validación para los modelos propuestos mediante la simulación de ensayos sencillos y curvas de falla del material compuesto. Se realizan además simulaciones de estructuras de paneles de mampostería con diversas configuraciones geométricas y mecánicas, sometidos a varias tipologías de cargas, para analizar el comportamiento mediante la comparación con resultados experimentales presentes en la bibliografía y/o otros modelos desarrollados por otros autores.

  • Finite element modeling of delamination in advanced composite beams and plates using one- and two-dimensional finite elements based on the refined zigzag theory

     Eijo, Ariel
    Universitat Politècnica de Catalunya
    Theses

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    Aunque los materiales laminados se han utilizado durante décadas, su uso ha aumentado en los últimos años como resultado de una mayor confianza por parte de la industria. Esto ha proporcionado a la comunidad científica muchas razones para dedicar una considerable cantidad de tiempo y esfuerzos en aras de una mejor comprensión de su comportamiento mecánico. Con este objetivo tanto la simulación experimental como numérica han estado trabajando juntos para dar respuesta a una variedad de problemas relacionados con estos materiales.En cuanto a la simulación numérica, un correcto modelado de la cinemática de los materiales laminados es esencial para capturar el comportamiento real de la estructura. Por otra parte, una vez que la cinemática de la estructura se ha predicho con precisión otros fenómenos no lineales como los proceso de daño y/o plasticidad podrían ser también estudiados.En consecuencia, con el fin de contribuir al constante desarrollo de herramientas numéricas más simples y eficaces para modelar materiales laminados, un método numérico para el modelado de la delaminación (modo II/III) en materiales compuestos avanzados utilizando elementos finitos de una y dos dimensiones es propuesto en este trabajo. Además, dos elementos finitos para la simulación de vigas y placas de varias capas altamente heterogéneos son desarrollados aquí.El documento está escrito en base a los resultados de cuatro artículos publicados en revistas indexadas. Copias de estos artículos se incluyen en el Apéndice. El cuerpo principal de esta tesis está constituido por los Capítulos 2-4. El Capítulo 2 aborda el tratamiento numérico de vigas y placas laminadas. El capítulo 3 presenta la formulación de los elementos finitos de viga LRZ y placa QLRZ basados en la Teoría Zigzag Refinada. Finalmente, la principal contribución de esta tesis, el modelo de delaminación LRZ/QLRZ, se desarrolla en el capítulo 4.

  • Delamination in laminated plates using the 4-noded quadrilateral QLRZ plate element based on the refined zigzag theory

     Eijo, Ariel; Oñate Ibáñez de Navarra, Eugenio; Oller Martinez, Sergio Horacio
    Composite structures
    Vol. 108, p. 456-471
    DOI: 10.1016/j.compstruct.2013.09.052
    Date of publication: 2014-02
    Journal article

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    A numerical method based on the Refined Zigzag Theory (RZT) to model delamination in composite laminated plate/shell structures is presented. The originality of this method is the use of 4-noded quadrilateral plate finite elements whit only seven variables per node to discretize the plate/shell geometry. The ability to capture the relative displacement between consecutive layers in fracture mode II and III is the more important advantage of this element, denoted QLRZ. A continuum isotropic damage model is used to model the mechanical behavior of the plies. The material non-lineal problem is solved with the modified Newton¿Raphson method. The RZT plate theory, the QLRZ finite element and the isotropic damage model are described in this work. Also, the implicit integration algorithm is presented. The performance of the numerical model is analyzed by studying the delamination in a rectangular plate for two different laminates, using the 3D analysis as the reference solution.

  • Formulación de elementos finitos para vigas de sección abierta formadas por laminados compuestos incluyendo las deformaciones tangenciales por cortante y torsión

     Oñate Ibáñez de Navarra, Eugenio; Oller Martinez, Sergio Horacio; Vargas, P. E.
    Revista internacional de métodos numéricos para cálculo y diseño en ingeniería
    Vol. 30, num. 4, p. 238-246
    DOI: 10.1016/j.rimni.2013.07.007
    Date of publication: 2014-10
    Journal article

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    In this paper we derive the field of displacements and strains for thin-walled open composite beams with composite laminated material including in their kinematics flexural and torsional shear deformations effects. The equilibrium equations are defined through the variational formulation and show that is possible to formulate C-o finite elements taking into account the torsional shear deformation. Stressstrain relationships for the cross-section of thin-walled composite beams are obtained by extending first-order laminate (FSDT: first-order shear deformation) theory and using a "free stress resultant condition at the boundary". Three different one-dimensional finite elements with C-o continuity are formulated for the study of thin-walled open composite beams and they are labelled as BSW (beam with shear and warping). The influence of the integration strategy in the BSW elements is evaluated via the shear-locking phenomenon and the rate of convergence for displacements and rotations. The stiffness matrix integration is compared using exact and reduced integration methods. Examples of pure torsion and flexo-torsion in a cantilever composite beam are performed. Numerical results are compared to those reported by other authors. (C) 2013 CIMNE (Universitat Politecnica de Catalunya). Published by Elsevier Espana, S.L.U. All rights reserved.

  • Numerical modelling of the cyclic structural behavior of slender steel members with restrained buckling

     Castro Medina, J. C.; Lopez Almansa, Francisco; Oller Martinez, Sergio Horacio
    Revista internacional de métodos numéricos para cálculo y diseño en ingeniería
    Vol. 30, num. 4, p. 229-237
    DOI: 10.1016/j.rimni.2013.07.008
    Date of publication: 2014-01-01
    Journal article

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    This work presents a numerical model of the cyclic structural behavior of dissipative buckling-restrained braces, commonly used as an alternative to classical concentric braces for seismic protection of building frames and other structures. Such devices are usually composed of a slender steel core embedded in a stockiest casing that is intended to prevent its buckling when it is under compression. The casing is made either of mortar or steel, and a sliding interface is interposed between the core and the casing to prevent excessive shear stress transfer. The behavior of the steel core is described by a damage and plasticity model; the behavior of the mortar casing is described by an isotropic damage model and the sliding behavior of the interface is described by a contact penalty model. These 3 models are implemented in the Abaqus software package following an explicit formulation. In a previous article (published in an earthquake engineering journal) the model was briefly described, its ability to reproduce the cyclical behavior of buckling-restrained braces was preliminarily pointed out and their results were satisfactorily compared with those of experimental tests. The aim of this paper is to describe the model thoroughly and to present new judgments about its usefulness. (C) 2013 CIMNE (Universitat Politecnica de Catalunya). Published by Elsevier Espana, S.L.U. All rights reserved.

  • Formulation of enriched macro elements using trigonometric shear deformation theory for free vibration analysis of symmetric laminated composite plate assemblies

     Rango, Rita F.; Nallim, Liz G.; Oller Martinez, Sergio Horacio
    Composite structures
    Vol. 119, p. 38-49
    DOI: 10.1016/j.compstruct.2014.08.012
    Date of publication: 2014-08-23
    Journal article

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    The formulation of an enriched macro element suitable to analyze the free vibration response of composite plate assemblies is presented in this article. Based on the Trigonometric Shear Deformation Theory (TSDT) and the use of Gram-Schmidt orthogonal polynomials as enrichment functions a finite macro element is developed. In the TSDT framework, shear stresses are vanished at the top and bottom surfaces of the plates and shear correction factors are no longer required. The Principle of Virtual Work is applied to derive the governing equations of motion. A special connectivity matrix is obtained; so that hierarchically enriched global stiffness matrix and mass matrix of general laminated plate structures are derived, allowing to study generally coplanar plate assemblies by combining two or more macro elements. This procedure gives a matrix-eigenvalue problem that can be solved with optimum efficiency. Results of free vibration analysis for symmetric laminated plates of different thickness ratios, geometrical planform shapes and boundary conditions are presented. The accuracy of the formulation is ensured by comparing some numerical examples with those available in the literature.

  • A localized mapped damage model for orthotropic materials

     Pelà, Luca; Cervera Ruiz, Miguel; Oller Martinez, Sergio Horacio; Chiumenti, Michele
    Engineering fracture mechanics
    Vol. 124-125, p. 196-216
    DOI: 10.1016/j.engfracmech.2014.04.027
    Date of publication: 2014-05-08
    Journal article

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    This paper presents an implicit orthotropic model based on the Continuum Damage Mechanics isotropic models. A mapping relationship is established between the behaviour of the anisotropic material and that of an isotropic one. The proposed model is used to simulate the failure loci of common orthotropic materials, such as masonry, fibre-reinforced composites and wood. The damage model is combined with a crack-tracking technique to reproduce the propagation of localized cracks in the discrete FE problem. The proposed numerical model is used to simulate the mixed mode fracture in masonry members with different orientations of the brick layers.

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    Comparative experimental analysis of the effect caused by artificial and real induced damage in composite laminates  Open access

     Pérez Martínez, Marco Antonio; Gil Espert, Lluis; Sanchez Romero, Montserrat; Oller Martinez, Sergio Horacio
    Composite structures
    Vol. 112, p. 169-178
    DOI: 10.1016/j.compstruct.2014.02.017
    Date of publication: 2014-06-02
    Journal article

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    This paper presents the results of an extensive experimental campaign aimed to examine the effect upon the vibration response and on the residual load-bearing capacity caused by both: isolated artificially induced interlaminar damage and low-velocity impact induced damage in composite laminates. The experimental programme included modal testing, drop-weight impact testing, ultrasonic inspection, transverse quasi-static loading testing and compression testing conducted on a set of 72 carbon fibre-reinforced composite laminated coupons. Both types of damage caused measurable changes in laminate performance, however marked divergent trends were observed. The results allowed for conclusions to be drawn regarding the adequacy of the artificial damage approach and highlighted the importance and role of other forms of degradation upon damage tolerance of laminated composites containing damage.

  • Impact damage identification in composite laminates using vibration testing

     Pérez Martínez, Marco Antonio; Gil Espert, Lluis; Oller Martinez, Sergio Horacio
    Composite structures
    Vol. 108, p. 267-276
    DOI: 10.1016/j.compstruct.2013.09.025
    Date of publication: 2014-02
    Journal article

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    Due to the problems arising from impact damage in composite laminates, there is a need to develop fast, accurate, cost-effective and non-destructive testing methods to identify this type of damage at an early stage and thus enhance the service life of composite structures. This paper presents the results of an extensive experimental campaign conducted to investigate the feasibility of using vibration-based meth- ods to identify damages sustained by composite laminates due to low-velocity impacts. The experimental programme included an evaluation of impact damage resistance and tolerance according to ASTM test methods, characterisation of induced damage by ultrasonic testing and quantification of the effects on the vibration response. The damage identification involved the detection, localisation, quantification and estimation of the remaining bearing capacity. Four damage indicators based on modal parameters were assessed by comparing pristine and damaged states. The results allowed for conclusions to be drawn regarding the capability and suitability of each damage indicator, including its ability to detect impact-induced damage, its precision in determining the location of damage, its sensitivity regarding damage extent and pertinent correlations with residual bearing capacity.

    Due to the problems arising from impact damage in composite laminates, there is a need to develop fast, accurate, cost-effective and non-destructive testing methods to identify this type of damage at an early stage and thus enhance the service life of composite structures. This paper presents the results of an extensive experimental campaign conducted to investigate the feasibility of using vibration-based methods to identify damages sustained by composite laminates due to low-velocity impacts. The experimental programme included an evaluation of impact damage resistance and tolerance according to ASTM test methods, characterisation of induced damage by ultrasonic testing and quantification of the effects on the vibration response. The damage identification involved the detection, localisation, quantification and estimation of the remaining bearing capacity. Four damage indicators based on modal parameters were assessed by comparing pristine and damaged states. The results allowed for conclusions to be drawn regarding the capability and suitability of each damage indicator, including its ability to detect impact-induced damage, its precision in determining the location of damage, its sensitivity regarding damage extent and pertinent correlations with residual bearing capacity.

  • Grup de resistència de materials i estructures a l'enginyeria

     Agelet de Saracibar Bosch, Carlos; Barbat Barbat, Horia Alejandro; Bugeda Castelltort, Gabriel; Cervera Ruiz, Miguel; Chiumenti, Michele; Oller Martinez, Sergio Horacio; Suarez Arroyo, Benjamin; Miquel Canet, Juan; Cante Teran, Juan Carlos; Hernandez Ortega, Joaquin Alberto; González Lopez, Jose Manuel; Martinez Garcia, Xavier; Escudero Torres, Cuauhtemoc; Morillo Guzman, Carlos; Huespe, Alfredo Edmundo; Carbonell Puigbo, Josep Maria; Rossi, Riccardo; Otero Gruer, Fermin Enrique; Comellas Sanfeliu, Ester; Barbu, Lucia Gratiela; Oliver Olivella, Fco. Javier
    Competitive project

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    Análisis numérico de la reparación y refuerzo de estructuras con FRP  Open access

     Oller Martinez, Sergio Horacio; Molina, Maritzabel; Vielma Pérez, Juan Carlos; Martinez Garcia, Xavier; Barbat Barbat, Horia Alejandro; Nallim, Liz G.
    DOI: 10.3926/oms.210
    Date of publication: 2014
    Book chapter

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    El propósito de esta obra es aportar una visión global del estado actual de la técnica y los recientes desarrollos sobre la aplicabilidad de los materiales compuestos en la obra civil y la edificación. El libro recoge una colección de trabajos de investigación de expertos nacionales e internacionales, que abordan los retos actuales y futuros en este campo, proporcionando, a través de una amplia variedad de casos de estudio, una hoja de ruta con las habilidades técnicas y los conocimientos prácticos necesarios para el empleo de materiales compuestos en nuevas aplicaciones. Los textos son ¿en la medida de lo posible¿ autocontenidos en sus partes, permitiendo una lectura acorde al interés particular de cada lector. En ellos se presentan fundamentos técnicos, resultados de investigaciones, y se revisan y compilan referencias bibliográficas actualizadas que complementan y permiten al lector adquirir un conocimiento más profundo de los temas expuestos, encaminándolo hacia posibles futuras líneas de investigación. Escrito por profesionales e investigadores con experiencia en este campo, este libro pretende ser un texto de referencia para los no iniciados en la temática y una herramienta de estudio e investigación para lectores de niveles más avanzados.

    Este libro presenta una panorámica del estado actual de los materiales compuestos y sus aplicaciones más relevantes en la obra civil y la edificación.

  • Análisis no-lineal de materiales compuestos mediante la teoría de mezclas serie-paralelo

     Martinez Garcia, Xavier; Oller Martinez, Sergio Horacio; Rastellini Canela, Fernando Gabriel
    DOI: 10.3926/oms.210
    Date of publication: 2014
    Book chapter

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    El propósito de esta obra es aportar una visión global del estado actual de la técnica y los recientes desarrollos sobre la aplicabilidad de los materiales compuestos en la obra civil y la edificación. El libro recoge una colección de trabajos de investigación de expertos nacionales e internacionales, que abordan los retos actuales y futuros en este campo, proporcionando, a través de una amplia variedad de casos de estudio, una hoja de ruta con las habilidades técnicas y los conocimientos prácticos necesarios para el empleo de materiales compuestos en nuevas aplicaciones. Los textos son ¿en la medida de lo posible¿ autocontenidos en sus partes, permitiendo una lectura acorde al interés particular de cada lector. En ellos se presentan fundamentos técnicos, resultados de investigaciones, y se revisan y compilan referencias bibliográficas actualizadas que complementan y permiten al lector adquirir un conocimiento más profundo de los temas expuestos, encaminándolo hacia posibles futuras líneas de investigación. Escrito por profesionales e investigadores con experiencia en este campo, este libro pretende ser un texto de referencia para los no iniciados en la temática y una herramienta de estudio e investigación para lectores de niveles más avanzados.

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    Coupled plastic damage model for low and ultra-low cycle seismic fatigue  Open access

     Barbu, Lucia Gratiela; Oller Martinez, Sergio Horacio; Martinez Garcia, Xavier; Barbat Barbat, Horia Alejandro
    World Congress on Computational Mechanics
    p. 2955-2966
    Presentation's date: 2014-07-21
    Presentation of work at congresses

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    This paper presents the theoretical framework for a coupled plastic damage constitutive model valid for materials subjected to cyclic loads that lead to low and ultra-low cycle fatigue. Two numerical examples were presented in order to illustrate the behaviour of the model and its capabilities.

  • Computational model of the human urinary blader

     Monteiro, Virginia; Oñate Ibáñez de Navarra, Eugenio; Oller Martinez, Sergio Horacio
    Date of publication: 2013
    Book

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    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.

    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.

  • Computational Model of the Human Urinary Bladder  Open access

     Silva Araujo monteiro, Virginia
    Department of Strength of Materials and Structural Engineering, Universitat Politècnica de Catalunya
    Theses

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    La propuesta de una vejiga artificial es un obstáculo a trasponer. El cáncer de vejiga está entrelos casos más frecuentes de enfermedades oncológicas en Estados Unidos y Europa. Ese cánceres considerado un problema médico importante una vez que esa enfermedad presenta altastasas de re-ocurrencia, muchas veces llevando a la remoción del órgano.La solución más sofisticada para remplazar ese órgano es la vejiga ileal, que consiste en una neovejigahecha de tejido intestinal del enfermo. Desafortunadamente, esa solución presenta no soloproblemas mecánicos funcionales, descritos en la literatura como problemas de vaciado y fuga,peo también problemas de orden biológica (como ejemplo pérdida ósea, debido a la absorciónpor el intestino de substancias que necesitan ser eliminadas del organismo).A través de la solicitación de la comunidad urológica del Hospital Clínico de Barcelona y con suexperiencia en modelos numéricos para estructuras biomédicas, el Centro de MétodosNuméricos en Ingeniería (CIMNE) ha tenido la iniciativa de proporcionar actividadinvestigadora de la mecánica de la vejiga urinaria y de la simulación de interacción fluidoestructurapara reproducir el llenado y vaciado de ese órgano con la orina.La simulación de la vejiga humana por el Método de los Elementos Finitos (FEM) y un completoentendimiento de la mecánica de ese órgano y de su interacción con la orina dará la posibilidadde proponer mejora en la geometría y de analizar materiales para la solución artificial en caso deremplazamiento de la vejiga.Para lograr ese objetivo, primeramente procedemos a una revisión bibliográfica de los modelosmatemáticos del aparato urinario y un estudio comprehensivo de la fisiología y dinámica de lavejiga. Presentamos una revisión de las principales estructuras urológicas, riñón, uréter y uretra.Las estructuras anexas también son consideradas para entender las condiciones de contorno delproblema estudiado.Posteriormente, proponemos el modelo constitutivo para estudiar la vejiga urinaria humana. Elcomportamiento del musculo detrusor durante llenado y vaciado de la vejiga con orina, suhabilidad de retención de orina a baja presión debe ser correctamente representada por mediode la implementación de un modelo constitutivo no-lineal. El modelo matemático necesitarepresentar las variables mecánicas que gobiernan ese órgano, y también las propiedades de laorina. El comportamiento no-lineal de tejidos vivos es implementado y validado con ejemplos dela literatura. La propiedad quasi-incompressible de la orina y las ecuaciones Navier-Stokes sonconsideradas para análisis del fluido.Para representar la geometría de la vejiga, implementamos un modelo computacional 3D apartir de imágenes de tomografía computadorizada de un cadáver adulto. Los datos son tratadospara considerar las condiciones de contorno. Hemos construido dos modelos de malla: ummallado com tetrahedos de quatro nodos y outro mallado com elementos de membrana de tresnodos.El esquema utilizado para calcular la interacción fluido-estructura debe ser adecuado paramateriales de densidad muy parecidas. La análisis numérica de llenado y vaciado de la vejigahumana es validada con testes urodinámicos estandarizados.La parte final de la tesis, presentamos una simulación de una neo-vejiga, siendo el primer pasopara representar numéricamente materiales artificiales para remplazamiento de la vejiga

    La propuesta de una vejiga artificial es un obstáculo a trasponer. El cáncer de vejiga está entre los casos más frecuentes de enfermedades oncológicas en Estados Unidos y Europa. Ese cáncer es considerado un problema médico importante una vez que esa enfermedad presenta altas tasas de re-ocurrencia, muchas veces llevando a la remoción del órgano. La solución más sofisticada para remplazar ese órgano es la vejiga ileal, que consiste en una neovejiga hecha de tejido intestinal del enfermo. Desafortunadamente, esa solución presenta no solo problemas mecánicos funcionales, descritos en la literatura como problemas de vaciado y fuga, peo también problemas de orden biológica (como ejemplo pérdida ósea, debido a la absorción por el intestino de substancias que necesitan ser eliminadas del organismo). A través de la solicitación de la comunidad urológica del Hospital Clínico de Barcelona y con su experiencia en modelos numéricos para estructuras biomédicas, el Centro de Métodos Numéricos en Ingeniería (CIMNE) ha tenido la iniciativa de proporcionar actividad investigadora de la mecánica de la vejiga urinaria y de la simulación de interacción fluidoestructura para reproducir el llenado y vaciado de ese órgano con la orina. La simulación de la vejiga humana por el Método de los Elementos Finitos (FEM) y un completo entendimiento de la mecánica de ese órgano y de su interacción con la orina dará la posibilidad de proponer mejora en la geometría y de analizar materiales para la solución artificial en caso de remplazamiento de la vejiga. Para lograr ese objetivo, primeramente procedemos a una revisión bibliográfica de los modelos matemáticos del aparato urinario y un estudio comprehensivo de la fisiología y dinámica de la vejiga. Presentamos una revisión de las principales estructuras urológicas, riñón, uréter y uretra. Las estructuras anexas también son consideradas para entender las condiciones de contorno del problema estudiado. Posteriormente, proponemos el modelo constitutivo para estudiar la vejiga urinaria humana. El comportamiento del musculo detrusor durante llenado y vaciado de la vejiga con orina, su habilidad de retención de orina a baja presión debe ser correctamente representada por medio de la implementación de un modelo constitutivo no-lineal. El modelo matemático necesita representar las variables mecánicas que gobiernan ese órgano, y también las propiedades de la orina. El comportamiento no-lineal de tejidos vivos es implementado y validado con ejemplos de la literatura. La propiedad quasi-incompressible de la orina y las ecuaciones Navier-Stokes son consideradas para análisis del fluido. Para representar la geometría de la vejiga, implementamos un modelo computacional 3D a partir de imágenes de tomografía computadorizada de un cadáver adulto. Los datos son tratados para considerar las condiciones de contorno. Hemos construido dos modelos de malla: un mallado con tetrahedos de cuatro nodos y otro mallado con elementos de membrana de tres nodos. El esquema utilizado para calcular la interacción fluido-estructura debe ser adecuado para materiales de densidad muy parecidas. El análisis numérico de llenado y vaciado de la vejiga humana es validada con tests urodinámicos estandarizados. La parte final de la tesis, presentamos una simulación de una neo-vejiga, siendo el primer paso para representar numéricamente materiales artificiales para remplazamiento de la vejiga.

    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.

  • A four-noded quadrilateral element for composite laminated plates/shells using the refined zigzag theory

     Eijo, Ariel; Oñate Ibáñez de Navarra, Eugenio; Oller Martinez, Sergio Horacio
    International journal for numerical methods in engineering
    Vol. 95, num. 8, p. 631-660
    DOI: 10.1002/nme.4503
    Date of publication: 2013-05-20
    Journal article

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    A new bilinear four-noded quadrilateral element (called quadrilateral linear refined zigzag) for the analysis of composite laminated and sandwich plates/shells based on the refined zigzag theory 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.

    A new bilinear four-noded quadrilateral element (called quadrilateral linear refined zigzag) for the analysis of composite laminated and sandwich plates/shells based on the refined zigzag theory 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.

  • An integrated procedure for the structural design of a composite rotor-hydrofoil of a Water Current Turbine (WCT)

     Oller Aramayo, Sergio A.; Nallim, Liz G.; Oller Martinez, Sergio Horacio
    Applied composite materials
    Vol. 20, num. 6, p. 1273-1288
    DOI: 10.1007/s10443-013-9332-9
    Date of publication: 2013-12
    Journal article

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    This paper shows an integrated structural design optimization of a composite rotor-hydrofoil of a water current turbine by means the finite elements method (FEM), using a Serial/Parallel mixing theory (Rastellini et al. Comput. Struct. 86:879¿896, 2008, Martinez et al., 2007, Martinez and Oller Arch. Comput. Methods. 16(4):357¿397, 2009, Martinez et al. Compos. Part B Eng. 42(2011):134¿144, 2010) coupled with a fluid-dynamic formulation and multi-objective optimization algorithm (Gen and Cheng 1997, Lee et al. Compos. Struct. 99:181¿192, 2013, Lee et al. Compos. Struct. 94(3):1087¿1096, 2012). The composite hydrofoil of the turbine rotor has been design using a reinforced laminate composites, taking into account the optimization of the carbon fiber orientation to obtain the maximum strength and lower rotational-inertia. Also, these results have been compared with a steel hydrofoil remarking the different performance on both structures. The mechanical and geometrical parameters involved in the design of this fiber-reinforced composite material are the fiber orientation, number of layers, stacking sequence and laminate thickness. Water pressure in the rotor of the turbine is obtained from a coupled fluid-dynamic simulation (CFD), whose detail can be found in the reference Oller et al. (2012). The main purpose of this paper is to achieve a very low inertia rotor minimizing the start-stop effect, because it is applied in axial water flow turbine currently in design by the authors, in which is important to take the maximum advantage of the kinetic energy. The FEM simulation codes are engineered by CIMNE (International Center for Numerical Method in Engineering, Barcelona, Spain), COMPack for the solids problem application, KRATOS for fluid dynamic application and RMOP for the structural optimization. To validate the procedure here presented, many turbine rotors made of composite materials are analyzed and three of them are compared with the steel one.

    This paper shows an integrated structural design optimization of a composite rotor-hydrofoil of a water current turbine by means the finite elements method (FEM), using a Serial/Parallel mixing theory (Rastellini et al. Comput. Struct. 86:879–896, 2008, Martinez et al., 2007, Martinez and Oller Arch. Comput. Methods. 16(4):357–397, 2009, Martinez et al. Compos. Part B Eng. 42(2011):134–144, 2010) coupled with a fluid-dynamic formulation and multi-objective optimization algorithm (Gen and Cheng 1997, Lee et al. Compos. Struct. 99:181–192, 2013, Lee et al. Compos. Struct. 94(3):1087–1096, 2012). The composite hydrofoil of the turbine rotor has been design using a reinforced laminate composites, taking into account the optimization of the carbon fiber orientation to obtain the maximum strength and lower rotational-inertia. Also, these results have been compared with a steel hydrofoil remarking the different performance on both structures. The mechanical and geometrical parameters involved in the design of this fiber-reinforced composite material are the fiber orientation, number of layers, stacking sequence and laminate thickness. Water pressure in the rotor of the turbine is obtained from a coupled fluid-dynamic simulation (CFD), whose detail can be found in the reference Oller et al. (2012). The main purpose of this paper is to achieve a very low inertia rotor minimizing the start-stop effect, because it is applied in axial water flow turbine currently in design by the authors, in which is important to take the maximum advantage of the kinetic energy. The FEM simulation codes are engineered by CIMNE (International Center for Numerical Method in Engineering, Barcelona, Spain), COMPack for the solids problem application, KRATOS for fluid dynamic application and RMOP for the structural optimization. To validate the procedure here presented, many turbine rotors made of composite materials are analyzed and three of them are compared with the steel one.

  • Robust design optimisation of advance hybrid (fiber¿metal) composite structures

     Lee, Dong Seop; Morillo Carbonell, Carlos; Oller Martinez, Sergio Horacio; Bugeda Castelltort, Gabriel; Oñate Ibáñez de Navarra, Eugenio
    Composite structures
    Vol. 99, p. 181-192
    DOI: 10.1016/j.compstruct.2012.11.033
    Date of publication: 2013-05
    Journal article

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    Impact damage prediction in carbon fiber-reinforced laminated composite using the matrix-reinforced mixing theory  Open access

     Pérez Martínez, Marco Antonio; Martinez Garcia, Xavier; Oller Martinez, Sergio Horacio; Gil Espert, Lluis; Rastellini Canela, Fernando Gabriel; Flores, Fernando
    Composite structures
    Vol. 104, p. 239-248
    DOI: 10.1016/j.compstruct.2013.04.021
    Date of publication: 2013-10-01
    Journal article

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    The impact damage tolerance of fiber-reinforced laminated composite materials is a source of concern, mainly due to internal induced damage which causes large reductions on the strength and stability of the structure. This paper presents a procedure based on a finite element formulation that can be used to perform numerical predictions of the impact induced internal damage in composite laminates. The procedure is based on simulating the composite performance using a micro-mechanical approach named matrix-reinforced mixing theory, a simplified version of the serial/parallel mixing theory that does not require neither the iterative procedure nor the calculation of the tangent stiffness tensor. The numerical formulation uses continuum mechanics to simulate the phenomenon of initiation and propagation of interlaminar damage with no need to formulate interface elements, resulting in a computationally less demanding formulation. To demonstrate the capability of numerical procedure when applied to a low-velocity impact problem, numerical results are compared with the experimental ones obtained in a test campaign performed on 44 laminates specimens subjected to an out-of-plane and concentrated impact event, according to ASTM test method. Results are in good agreement with experimental data in terms of delamination onset and the internal spatial distribution of induced damage.

  • A numerical model of delamination in composite laminated beams using the LRZ beam element based on the refined zigzag theory

     Eijo, Ariel; Oñate Ibáñez de Navarra, Eugenio; Oller Martinez, Sergio Horacio
    Composite structures
    Vol. 104, p. 270-280
    DOI: 10.1016/j.compstruct.2013.04.035
    Date of publication: 2013-10
    Journal article

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    A method based on the Refined Zigzag Theory (RZT) to model delamination in composite laminated beam structures is presented. The novelty of this method is the use of one-dimensional finite elements to discretize the geometry of the beam. The key property of this beam element, named LRZ [1], is the possibility to capture the relative displacement between consecutive layers which occurs during delamination. The fracture mode that the LRZ element is capable to predict is mode II. In order to capture the relative displacement using the LRZ element it is necessary to adapt the RZT theory as presented in this paper. The mechanical properties of the layers are modeled using a continuum isotropic damage model [2]. The modified Newton-Raphson method is used for solving the non-linear problem.The RZT theory, the LRZ finite element and the isotropic damage model are described in the paper. Also, the implicit integrations algorithm is presented. The performance of the LRZ element is analyzed by studying the delamination in a beam for two different laminates, using the plane stress solution as a reference.

    A method based on the Refined Zigzag Theory (RZT) to model delamination in composite laminated beam structures is presented. The novelty of this method is the use of one-dimensional finite elements to discretize the geometry of the beam. The key property of this beam element, named LRZ [1], is the possibility to capture the relative displacement between consecutive layers which occurs during delamination. The fracture mode that the LRZ element is capable to predict is mode II. In order to capture the relative displacement using the LRZ element it is necessary to adapt the RZT theory as presented in this paper. The mechanical properties of the layers are modeled using a continuum isotropic damage model [2]. The modified Newton–Raphson method is used for solving the non-linear problem. The RZT theory, the LRZ finite element and the isotropic damage model are described in the paper. Also, the implicit integrations algorithm is presented. The performance of the LRZ element is analyzed by studying the delamination in a beam for two different laminates, using the plane stress solution as a reference.

  • Multi-objective green design optimization of carbon nanotube composite structures

     Morillo, Carlos; Lee, Dong Seop; Bugeda Castelltort, Gabriel; Oller Martinez, Sergio Horacio; Oñate Ibáñez de Navarra, Eugenio
    International Conference on Computational Methods for Coupled Problems in Science and Engineering
    p. 1
    Presentation's date: 2013-06-19
    Presentation of work at congresses

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  • Diseño óptimo multi-objetivo y ecológico de materiales con estructuras compuestas con nanotubos de carbono

     Morillo, Carlos; Lee, Dong Seop; Bugeda Castelltort, Gabriel; Oller Martinez, Sergio Horacio; Oñate Ibáñez de Navarra, Eugenio
    Congreso de Métodos Numéricos en Ingeniería
    p. 1695
    Presentation's date: 2013-06-26
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  • Analytical and numerical analysis of human dental occlusal contact

     Bastos de Souza, FLAVIA; Casas, Estevam; Oller Martinez, Sergio Horacio
    Computer methods in biomechanics and biomedical engineering
    Vol. 16, num. 5, p. 495-503
    DOI: 10.1080/10255842.2011.627328
    Date of publication: 2013
    Journal article

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    The knowledge of contact forces in teeth surfaces during mastication or para-functional movements can help to understand processes related to friction and wear of human dental enamel. The development of a numerical model for analysis of the occlusal contact between two antagonistic teeth is proposed, which includes three basic steps: the characterisation of the surface roughness, its homogenisation using an assumed distribution function and the numerical determination of the resulting forces. Finite element strain results for the main different asperities are statistically combined, deriving the predicted macroscopic behaviour of the interface. Axisymmetric and 3D numerical models with an elasto-plastic constitutive law are used to simulate micro-indentations and micro-contacts, respectively. The contact is allowed to occur locally in planes not necessarily parallel to the surface's mean plane, a problem for which there is no analytical solution. The three identified parameters, homogenised surface hardness (3.68 GPa), surface yield stress (3.08 GPa) and static friction coefficient (0.23), agree with the experimental values reported in the literature.

  • Characterization of mechanical properties of biological tissue: application to the FEM analysis of the urinary bladder

     Oñate Ibáñez de Navarra, Eugenio; Bellomo, Facundo J.; Monteiro, Virginia; Oller Martinez, Sergio Horacio; Nallim, Liz G.
    Date of publication: 2013
    Book chapter

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    This text presents an approach for the mechanical behavior of soft biological tissue using the finite elements method and a general constitutive model. Specifically we analyze the mechanical behavior of a urinary bladder starting from a procedure for obtaining the mechanical characterization of the biological tissue. Bladder tissue is modelled as a composite material formed by soft matrix reinforced with preferentially oriented fibres. In the first part of the text we present a procedure for identifying the mechanical properties of biological tissue main constituents by an inverse method. Then this information is used for the numerical simulation of the mechanical behavior of the bladder within the FEM. The formulation can be applied to various types of biological tissues, both in the field of material characterization, and in the numerical simulation of the tissue biomechanical behavior.

  • MODELO ANALÍTICO NUMÉRICO PARA EL ESTUDIO Y OPTIMIZACIÓN DE PLACAS GRUESAS LAMINADAS

     Rango, Rita-Fernanda
    Universidad Nacional de Salta (UNSa)- Argentina.
    Theses

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  • Modelización numérica del comportamiento constitutivo del daño local y global y su correlación con la evolución de las frecuencias naturales en estructuras de hormigón reforzado  Open access

     Paredes Lopez, Jairo Andrés
    Universitat Politècnica de Catalunya
    Theses

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    Esta tesis surge de la necesidad de establecer un método racional y práctico para identificar, a través del cambio de las frecuencias naturales , el daño en estructuras de hormigón armado. Por lo que se desarrolla un nuevo modelo constitutivo de daño diferenciado con dos variables internas de daño utilizando una única superficie de discontinuidad para tracción, compresión y cortante; asimismo, se plantea un procedimiento numérico para el cálculo de las frecuencias naturales con sus formas modales de vibración para diferentes estados de daño de estructuras de hormigón armado; se presenta una metodología para correlacionar daño global y frecuencias naturales . Esta tesis se desarrollará en el marco del análisis de estructuras y la mecánica computacional, particularmente, del análisis de materiales compuestos utilizando la teoría de mezclas serie/paralelo. Los resultados numéricos obtenidos se han comparado con resultados experimentales y numéricos obtenidos de la literatura, se ha observado buenos ajustes de los resultados.

    Esta tesis surge de la necesidad de establecer un método racional y práctico para identificar, a través del cambio de las frecuencias naturales , el daño en estructuras de hormigón armado. Por lo que se desarrolla un nuevo modelo constitutivo de daño diferenciado con dos variables internas de daño utilizando una única superficie de discontinuidad para tracción, compresión y cortante; asimismo, se plantea un procedimiento numérico para el cálculo de las frecuencias naturales con sus formas modales de vibración para diferentes estados de daño de estructuras de hormigón armado; se presenta una metodología para correlacionar daño global y frecuencias naturales . Esta tesis se desarrollará en el marco del análisis de estructuras y la mecánica computacional, particularmente, del análisis de materiales compuestos utilizando la teoría de mezclas serie/paralelo. Los resultados numéricos obtenidos se han comparado con resultados experimentales y numéricos obtenidos de la literatura, se ha observado buenos ajustes de los resultados

    This thesis emerges from the need to establish a rational and smart method to estimate the global damage through changes on eigenfrequency of concrete structures. Therefore, a new constitutive damage model is developed with two scalar inner variables and using only one surface of discontinuity to traction, compression and shear. Additionally, a numerical process has been proposed to calculate eigenfrequencies and eigenvectors of concrete structure with different levels of damage. A methodology to correlation ship between global damage and changes on e1genfrequencies has been proposed. This thesis is based on structural analysis and computational mechanics and, particularly, on analysis of composite materials using serial/parallel mix theory. The numerical results obtained in this thesis is have been compared with experimental and numerical results obtained of literature, and can be seen a good fit.

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    Stepwise advancing strategy for the simulation of fatigue problems  Open access

     Barbu, Lucia Gratiela; Oller Martinez, Sergio Horacio; Martinez Garcia, Xavier; Barbat Barbat, Horia Alejandro
    International Conference on Computational Plasticity Fundamentals and Applications
    p. 1153-1164
    Presentation's date: 2013-09-04
    Presentation of work at congresses

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    A time advance strategy for cyclic loading will be presented, applied to the fatigue formulation first proposed by [1].The coupling of both formulationsprovides a comprehensive approachto simulate high cycle fatigue problems accurately and with an important computational cost reduction. The capabilities of the proposed procedure are shown in a numerical example

    A time advance strategy for cyclic loading will be presented, applied to the fatigue formulation first proposed by [1].The coupling of both formulations provides a comprehensive approachto simulate high cycle fatigue problems accurately and with an important computational cost reduction. The capabilities of the proposed procedure are shown in a numerical example

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    Analysis of ultra low cycle fatigue problems with the Barcelona plastic damage model  Open access

     Martinez Garcia, Xavier; Oller Martinez, Sergio Horacio; Barbu, Lucia Gratiela; Barbat Barbat, Horia Alejandro
    International Conference on Computational Plasticity Fundamentals and Applications
    p. 352-363
    Presentation's date: 2013-09-05
    Presentation of work at congresses

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    This paper presents a plastic formulation based on the Barcelona plastic damage model capable of predicting the material failure due to Ultra Low Cycle Fatigue. This is achieved taking into account the fracture energy dissipated during the cyclic process. This approach allows the simulation of ULCF in regular cyclic tests, but also in non-regular cases such as seismic loads.

  • Dimensionado sísmico de edificios porticados de hormigón armado mediante factores de amplificación con base en energía

     Vielma Pérez, Juan Carlos; Barbat Barbat, Horia Alejandro; Oller Martinez, Sergio Horacio
    Hormigon y acero
    num. 263, p. 83-96
    Date of publication: 2012
    Journal article

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    El proyecto sismorresistente de estructuras actual se realiza mediante una serie de prescripciones normativas que persiguen garantizar su adecuado comportamiento. Los procedimientos actuales de análisis se realizan utilizando el comportamiento elástico, aplicando los factores de reducción de respuesta para obtener fuerzas sísmicas equivalentes, representativas del comportamiento inelástico que pueden alcanzar las estructuras al ser sometidas a la acción de sismos fuertes. A partir de los resultados del análisis elástico se obtienen los desplazamientos inelásticos, amplificados mediante factores que son función de los factores de reducción; sin embargo, se ha observado una amplia variación en los valores de los factores de amplificación prescritos en las normas a nivel mundial, por lo que se justifica profundizar en el estudio de dichos factores. En este trabajo se presenta un procedimiento de dimensionado sísmico con base en la respuesta no lineal. El procedimiento es aplicado a un conjunto de edificios regulares de hormigón armado de diferentes alturas, proyectados para niveles altos de amenaza sísmica y es evaluado aplicando análisis dinámico no lineal para tres Estados Límite, correlacionado con tres umbrales de daño que se definen a través de las derivas de planta. Los resultados demuestran que el procedimiento es adecuado para realizar el dimensionado sísmico de edificios, proporcionando al proyectista criterios de evaluación más cónsonos con las características de los edificios y de la amenaza sísmica.

  • Dynamical analysis of long fiber-reinforced laminated plates with elastically restrained edges

     Bellomo, Facundo; Quinteros, Ricardo D.; Oller Martinez, Sergio Horacio; Nallim, Liz G.
    Advances in Acoustics and Vibration
    Vol. 2012, p. 1-16
    DOI: 10.1155/2012/189376
    Date of publication: 2012
    Journal article

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  • Nonlinear homogenization techniques to solve masonry structures problems

     Quinteros, Ricardo D.; Oller Martinez, Sergio Horacio; Nallim, Liz G.
    Composite structures
    Vol. 94, num. 2, p. 724-730
    DOI: 10.1016/j.compstruct.2011.09.00
    Date of publication: 2012-01
    Journal article

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  • Simple and accurate two-noded beam element for composite laminated beams using a refined zigzag theory

     Oñate Ibáñez de Navarra, Eugenio; Eijo, Ariel; Oller Martinez, Sergio Horacio
    Computer methods in applied mechanics and engineering
    Vol. 213-216, p. 362-382
    DOI: 10.1016/j.cma.2011.11.023
    Date of publication: 2012-03
    Journal article

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  • Multilayered composite structure design optimisation using distributed/parallel multi-objective evolutionary algorithms

     Lee, Dong Seop; Morillo Carbonell, Carlos; Bugeda Castelltort, Gabriel; Oller Martinez, Sergio Horacio; Oñate Ibáñez de Navarra, Eugenio
    Composite structures
    Vol. 94, num. 3, p. 1087-1096
    DOI: 10.1016/j.compstruct.2011.10.009
    Date of publication: 2012-02
    Journal article

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  • Study and prediction of the mechanical performance of a nanotube-reinforced composite

     Otero, Fermin; Martinez Garcia, Xavier; Oller Martinez, Sergio Horacio; Salomon, Ramon Omar
    Composite structures
    Vol. 94, num. 9, p. 2920-2930
    DOI: 10.1016/j.compstruct.2012.04.001
    Date of publication: 2012-09
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  • Estudio numérico-experimental de la interfaz hormigón-epoxi-FRP para una estructura reforzada sometida a doble corte

     Molina, Maritzabel; Cruz Solis, Juan Jose; Oller Martinez, Sergio Horacio; Barbat Barbat, Horia Alejandro; Gil Espert, Lluis
    Revista internacional de métodos numéricos para cálculo y diseño en ingeniería
    Vol. 28, num. 2, p. 65-79
    Date of publication: 2012-02
    Journal article

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  • A constitutive model for tissue adaptation: necrosis and stress driven growth

     Bellomo, Facundo; Armero, Francisco; Nallim, Liz G.; Oller Martinez, Sergio Horacio
    Mechanics research communications
    Vol. 42, num. SI, p. 51-59
    DOI: 10.1016/j.mechrescom.2011.11.007
    Date of publication: 2012-06
    Journal article

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  • Evaluación del daño por impacto en laminados de material compuesto mediante la respuesta dinámica

     Pérez Martínez, Marco Antonio; Gil Espert, Lluis; Oller Martinez, Sergio Horacio
    Date of publication: 2012-04-23
    Book

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  • Puentes peatonales sostenibles (superbam)

     Martinez Garcia, Xavier; Oller Martinez, Sergio Horacio
    Competitive project

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  • Simulación de los materiales compuestos como refuerzo en estructuras de hormigón armado

     Molina Herrera, Maritzabel
    Department of Strength of Materials and Structural Engineering, Universitat Politècnica de Catalunya
    Theses

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  • Numerial modelling based on the multiscale homogenization theory. Application in composite materials and structures  Open access

     Badillo Almaraz, Hiram
    Department of Strength of Materials and Structural Engineering, Universitat Politècnica de Catalunya
    Theses

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    A multi-domain homogenization method is proposed and developed in this thesis based on a two-scale technique. The method is capable of analyzing composite structures with several periodic distributions by partitioning the entire domain of the composite into substructures making use of the classical homogenization theory following a first-order standard continuum mechanics formulation. The need to develop the multi-domain homogenization method arose because current homogenization methods are based on the assumption that the entire domain of the composite is represented by one periodic or quasi-periodic distribution. However, in some cases the structure or composite may be formed by more than one type of periodic domain distribution, making the existing homogenization techniques not suitable to analyze this type of cases in which more than one recurrent configuration appears. The theoretical principles used in the multi-domain homogenization method were applied to assemble a computational tool based on two nested boundary value problems represented by a finite element code in two scales: a) one global scale, which treats the composite as an homogeneous material and deals with the boundary conditions, the loads applied and the different periodic (or quasi-periodic) subdomains that may exist in the composite; and b) one local scale, which obtains the homogenized response of the representative volume element or unit cell, that deals with the geometry distribution and with the material properties of the constituents. The method is based on the local periodicity hypothesis arising from the periodicity of the internal structure of the composite. The numerical implementation of the restrictions on the displacements and forces corresponding to the degrees of freedom of the domain's boundary derived from the periodicity was performed by means of the Lagrange multipliers method. The formulation included a method to compute the homogenized non-linear tangent constitutive tensor once the threshold of nonlinearity of any of the unit cells has been surpassed. The procedure is based in performing a numerical derivation applying a perturbation technique. The tangent constitutive tensor is computed for each load increment and for each iteration of the analysis once the structure has entered in the non-linear range. The perturbation method was applied at the global and local scales in order to analyze the performance of the method at both scales. A simple average method of the constitutive tensors of the elements of the cell was also explored for comparison purposes. A parallelization process was implemented on the multi-domain homogenization method in order to speed-up the computational process due to the huge computational cost that the nested incremental-iterative solution embraces. The effect of softening in two-scale homogenization was investigated following a smeared cracked approach. Mesh objectivity was discussed first within the classical one-scale FE formulation and then the concepts exposed were extrapolated into the two-scale homogenization framework. The importance of the element characteristic length in a multi-scale analysis was highlighted in the computation of the specific dissipated energy when strain-softening occurs. Various examples were presented to evaluate and explore the capabilities of the computational approach developed in this research. Several aspects were studied, such as analyzing different composite arrangements that include different types of materials, composites that present softening after the yield point is reached (e.g. damage and plasticity) and composites with zones that present high strain gradients. The examples were carried out in composites with one and with several periodic domains using different unit cell configurations. The examples are compared to benchmark solutions obtained with the classical one-scale FE method.

    En esta tesis se propone y desarrolla un método de homogeneización multi-dominio basado en una técnica en dos escalas. El método es capaz de analizar estructuras de materiales compuestos con varias distribuciones periódicas dentro de un mismo continuo mediante la partición de todo el dominio del material compuesto en subestructuras utilizando la teoría clásica de homogeneización a través de una formulación estándar de mecánica de medios continuos de primer orden. La necesidad de desarrollar este método multi-dominio surgió porque los métodos actuales de homogeneización se basan en el supuesto de que todo el dominio del material está representado por solo una distribución periódica o cuasi-periódica. Sin embargo, en algunos casos, la estructura puede estar formada por más de un tipo de distribución de dominio periódico. Los principios teóricos desarrollados en el método de homogeneización multi-dominio se aplicaron para ensamblar una herramienta computacional basada en dos problemas de valores de contorno anidados, los cuales son representados por un código de elementos finitos (FE) en dos escalas: a) una escala global, que trata el material compuesto como un material homogéneo. Esta escala se ocupa de las condiciones de contorno, las cargas aplicadas y los diferentes subdominios periódicos (o cuasi-periódicos) que puedan existir en el material compuesto; y b) una escala local, que obtiene la respuesta homogenizada de un volumen representativo o celda unitaria. Esta escala se ocupa de la geometría, y de la distribución espacial de los constituyentes del compuesto así como de sus propiedades constitutivas. El método se basa en la hipótesis de periodicidad local derivada de la periodicidad de la estructura interna del material. La implementación numérica de las restricciones de los desplazamientos y las fuerzas derivadas de la periodicidad se realizaron por medio del método de multiplicadores de Lagrange. La formulación incluye un método para calcular el tensor constitutivo tangente no-lineal homogeneizado una vez que el umbral de la no-linealidad de cualquiera de las celdas unitarias ha sido superado. El procedimiento se basa en llevar a cabo una derivación numérica aplicando una técnica de perturbación. El tensor constitutivo tangente se calcula para cada incremento de carga y para cada iteración del análisis una vez que la estructura ha entrado en el rango no-lineal. El método de perturbación se aplicó tanto en la escala global como en la local con el fin de analizar la efectividad del método en ambas escalas. Se lleva a cabo un proceso de paralelización en el método con el fin de acelerar el proceso de cómputo debido al enorme coste computacional que requiere la solución iterativa incremental anidada. Se investiga el efecto de ablandamiento por deformación en el material usando el método de homogeneización en dos escalas a través de un enfoque de fractura discreta. Se estudió la objetividad en el mallado dentro de la formulación clásica de FE en una escala y luego los conceptos expuestos se extrapolaron en el marco de la homogeneización de dos escalas. Se enfatiza la importancia de la longitud característica del elemento en un análisis multi-escala en el cálculo de la energía específica disipada cuando se produce el efecto de ablandamiento. Se presentan varios ejemplos para evaluar la propuesta computacional desarrollada en esta investigación. Se estudiaron diferentes configuraciones de compuestos que incluyen diferentes tipos de materiales, así como compuestos que presentan ablandamiento después de que el punto de fluencia del material se alcanza (usando daño y plasticidad) y compuestos con zonas que presentan altos gradientes de deformación. Los ejemplos se llevaron a cabo en materiales compuestos con uno y con varios dominios periódicos utilizando diferentes configuraciones de células unitarias. Los ejemplos se comparan con soluciones de referencia obtenidas con el método clásico de elementos finitos en una escala.

  • Numerical-experimental study of the FRP-epoxy-concrete interface for reinforced structures under double shear

     Molina Herrera, Maritzabel; Cruz Solis, Juan Jose; Oller Martinez, Sergio Horacio; Barbat Barbat, Horia Alejandro; Gil Espert, Lluis
    Revista internacional de métodos numéricos para cálculo y diseño en ingeniería
    Vol. 28, num. 2, p. 65-79
    DOI: 10.1016/j.rimni.2011.11.007
    Date of publication: 2012
    Journal article

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  • An inverse approach for the mechanical characterisation of vascular tissues via a generalised rule of mixtures

     Bellomo, Facundo; Oller Martinez, Sergio Horacio; Nallim, Liz G.
    Computer methods in biomechanics and biomedical engineering
    Vol. 15, num. 12, p. 1257-1262
    DOI: 10.1080/10255842.2011.585976
    Date of publication: 2012-12
    Journal article

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    Mechanical factors such as stresses and strains play a major role in the growth and remodelling of soft biological tissues. The main constituents of tissue undergo different processes reacting to mechanical stimulus. Thereby, the characterisation of growth and remodelling requires an accurate estimation of the stresses and strains of their main components. Many soft tissues can be considered as composite materials and can be analysed using an appropriate rule of mixtures. Particularly, arterial tissue can be modelled as an isotropic soft matrix reinforced with preferentially oriented collagen fibres. An inverse approach to obtain the mechanical characterisation of each main component is proposed in this work. The procedure is based on a rule of mixtures raised in a finite deformation framework and generalised to include kinematics and compatibility equations for serial–parallel behaviour. This methodology allows obtaining the stress–strain relationship of the components fitting experimental data.

  • Advanced models for finite element analysis of composite materials

     Oller Martinez, Sergio Horacio; Oñate Ibáñez de Navarra, Eugenio
    DOI: 10.1002/9781118097298
    Date of publication: 2012
    Book chapter

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    Written by prominent international experts from industry and academia, the Wiley Encyclopedia of Composites, Second Edition presents over 265 new and revised articles addressing the new technological advances in properties, processing, formulation, design, analysis, evaluation, manufacture, testing, and reliability of composites. The entire range of industrial applications of composites is covered.

  • Evaluación del daño por impacto en laminados de material compuesto mediante la respuesta dinámica

     Pérez Martínez, Marco Antonio
    Department of Strength of Materials and Structural Engineering, Universitat Politècnica de Catalunya
    Theses

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  • Formulación de elementos finitos para vigas de sección abierta en laminados compuestos

     Vargas Mendoza, Pablo Enrique
    Department of Strength of Materials and Structural Engineering, Universitat Politècnica de Catalunya
    Theses

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  • The Quadrants Method: a procedure to evaluate the seismic performance of existing buildings

     Vielma Pérez, Juan Carlos; Martínez, Y; Barbat Barbat, Horia Alejandro; Oller Martinez, Sergio Horacio
    World Conference on Earthquake Engineering
    p. 1-9
    Presentation's date: 2012-09-25
    Presentation of work at congresses

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    In this work a new simple procedure for the evaluation of the seismic performance is formulated. It combines the results of non-linear static analysis with a specific Limit State defined by inter-storey drift-based damage threshold and the seismic demand obtained from the inelastic design spectrum. With both values it is possible to define four zones in the capacity curve which characterizes four different seismic performances. The procedure is used to evaluate two reinforced concrete framed buildings, the first one consist in a typical lowrise building designed according to current Venezuelan codes; the second one is a four-storey building designed according to older code, whose had been damaged by fire. Results shown both cases do not meet the Quadrants Method criterion then they need to be redesigned. Redesigned buildings were submitted to a non-linear dynamic analysis, representative of three hazard levels associated with three Limit States. These redesigned buildings met all the objectives associated with the hazard levels, showing the efficiency of the method for the rapid evaluation of the seismic performance of existing buildings.

  • Low environmental impact composite structure design optimisation using robust multi-objective optimisation platform

     Morillo Carbonell, Carlos; Lee, Dong Seop; Bugeda Castelltort, Gabriel; Oller Martinez, Sergio Horacio; Oñate Ibáñez de Navarra, Eugenio
    International Conference on Mechanics of Nano, Micro and Macro Composite Structures
    p. 1-2
    Presentation's date: 2012-06
    Presentation of work at congresses

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