Documents published in 2010 : Scipedia

An introduction to soil dynamics, por Arnold Verruijt
L. Suárez

Revista Internacional de Desastres Naturales, Accidentes e Infraestructura Civil (2010). Vol. 10, 2

Abstract
Revision: An introduction to soil dynamics, por Arnold Verruijt
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Análise dinâmica de uma torre estaiada submetida à tormenta EPS
V. Puglia, L. Miguel, I. Iturrioz

Revista Internacional de Desastres Naturales, Accidentes e Infraestructura Civil (2010). Vol. 10, 2

Abstract
No presente trabalho faz-se uma análise dinâmica de uma torre treliçada estaiada submetida à tormenta EPS através de um registro de vento obtido a partir de sua componente média registrada experimentalmente in loco e da simulação numérica do espectro de sua componente flutuante. A torre estudada está localizada na Universidade de Passo Fundo, na cidade de Passo Fundo, RS, Brasil. Esta torre se encontra instrumentada, registrando velocidades de vento de forma contínua, sendo possível determinar, nos registros existentes, ventos característicos de tormentas TS e EPS. Conta-se também com a caracterização dinâmica desta torre para a qual foram determinadas suas freqüências naturais de vibração. Para determinar um histórico de vento foi usado um registro anemométrico proveniente de uma tormenta do tipo EPS. A taxa de aquisição utilizada foi baixa, razão pela qual as flutuações do registro experimental foram perdidas. Utilizando expressões teóricas foi possível regenerar a componente flutuante a qual foi somada ao registro anemométrico. A metodologia empregada para realizar esta implementação é um aspecto original do presente trabalho.
Abstract
No presente trabalho faz-se uma análise dinâmica de uma torre treliçada estaiada submetida à tormenta EPS através de um registro de vento obtido a partir de sua componente [...]
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Estudio de la estructura del subsuelo y de los efectos de sitio en Chilpancingo Guerrero, México
A. García, A. Bernal, J. González

Revista Internacional de Desastres Naturales, Accidentes e Infraestructura Civil (2010). Vol. 10, 2

Abstract
Se estimó la estructura estratigráfica de los depósitos sedimentarios profundos en el valle de Chilpancingo Guerrero, México, y la variación de la velocidad de las ondas de cortante con la profundidad. Se realizaron mediciones simultáneas de microtremores a partir de arreglos de sismómetros en dos sitios del valle. Para determinar las curvas de dispersión de la velocidad de fase de las ondas superficiales se utilizó el método de autocorrelación espacial, SPAC, en un rango de frecuencias de 0.37 a 8.0 Hz. Los efectos de sitio se estimaron al usar la técnica del cociente espectral suelo sedimentario/roca, y la técnica del cociente espectral H/V. Cuando se comparan las funciones de transferencia de los modelos estratigráficos, que se extienden hasta 355 m de profundidad, con las observadas de acelerogramas de sismos, se muestra la eficacia del método SPAC usado en este trabajo para estimar el perfil del subsuelo. Se encuentra que la amplificación más importante en el valle se concentra en un intervalo de 2 a 3 s. Los resultados sugieren un fuerte efecto 2D de las irregularidades de la geología profunda.
Abstract
Se estimó la estructura estratigráfica de los depósitos sedimentarios profundos en el valle de Chilpancingo Guerrero, México, y la variación de la velocidad de las ondas [...]
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Modelo aproximado para el análisis sísmico del Puente Norte 1 en Ecuador construido con aisladores FPS
R. Falconí, D. Añazco, R. Ángulo

Revista Internacional de Desastres Naturales, Accidentes e Infraestructura Civil (2010). Vol. 10, 2

Abstract
El uso de aisladores de base tipo péndulo de fricción, FPS ("Frictional Pendulum System") en puentes es una muy buena alternativa en países de alta peligrosidad sísmica ya que el peso de la superestructura se opone al movimiento de la subestructura como consecuencia de un sismo. En este artículo se detallan aspectos constructivos de uno de los puentes ubicados en el estuario del río Esmeraldas, en el Ecuador, con aisladores de base FPS ubicados sobre los estribos exteriores tipo cajón y pila central circular. Se realiza el análisis sísmico en sentido longitudinal empleando elementos finitos lineales con masa uniforme distribuida para los pilotes y elementos finitos rectangulares para los apoyos del puente. Los FPS han sido modelados como resortes cuya rigidez es función de la carga que sobre ellos gravita y del radio de curvatura. Se ha considerado un modelo elasto-plástico para la curva carga-deformación del suelo. Por otra parte, se generó un sismo artificial compatible con el espectro del Código Ecuatoriano de la Construcción, para un período de retorno de 475 años, para el sitio del proyecto. Las respuestas en el tiempo que se presentan ayudan a entender el comportamiento sísmico del puente con aisladores FPS.
Abstract
El uso de aisladores de base tipo péndulo de fricción, FPS ("Frictional Pendulum System") en puentes es una muy buena alternativa en países [...]
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Relaciones entre límites de daño, parámetros estructurales y magnitudes sísmicas para evaluar pórticos de hormigón reforzado
A. Vega, M. Kowalsky

Revista Internacional de Desastres Naturales, Accidentes e Infraestructura Civil (2010). Vol. 10, 2

Abstract
El presente trabajo propone una metodología sencilla para evaluar pórticos de hormigón reforzado para diferentes límites de daño en función de las deformaciones del material (acero de refuerzo y hormigón), desplazamientos entrepisos, y magnitud del terremoto. Se utilizó el método conocido como diseño directo basado en desplazamientos (DDBD) en conjunto con ecuaciones de desplazamientos espectrales y aceleraciones del código de diseño IBC-06 y ecuaciones existentes de magnitud sísmica de momento para desarrollar la metodología de evaluación propuesta. Mediante relaciones entre deformaciones del material, desplazamientos y magnitud sísmica se determinó qué límites de daño pueden ser desarrollados en una zona sísmica especificada y qué alturas de pórticos pueden ser más críticas.
Abstract
El presente trabajo propone una metodología sencilla para evaluar pórticos de hormigón reforzado para diferentes límites de daño en función de las deformaciones del [...]
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Daño por efectos de oxidación en gasoductos
J. Massa, A. Giudici

Revista Internacional de Desastres Naturales, Accidentes e Infraestructura Civil (2010). Vol. 10, 2

Abstract
La seguridad en los sistemas de transporte y distribución de gas es uno de los principales aspectos que debe considerarse en el diseño de dichas instalaciones. Este hecho es abordado por las regulaciones internacionales con el objeto de minimizar los eventos negativos para la población. En la primera parte de este trabajo se describen las distintas características constructivas de las cañerías de gas y los defectos típicos que pueden contener. Como caso de estudio se tratan aspectos relacionados con la seguridad que presenta en la actualidad uno de los gasoductos que proveen gas natural a la ciudad de Córdoba (Argentina), que ha estado operando por más de 40 años y muestra algunos signos de corrosión. Para determinar las características del gasoducto se tomaron muestras de la cañería constitutiva y se realizaron ensayos mecánicos. El estado tensional asociado a los defectos de tipo "volumétrico" se estudia con un modelo basado en la "tensión de flujo" del material. Este modelo permite calcular, dependiendo de las dimensiones de la cañería y el largo del defecto, la presión de transición que separa los defectos que causan fallas por rotura de aquellos que provocan fuga de gas. A partir de la presión de falla de la cañería para defectos pasantes y no pasantes se definen las condiciones de seguridad del sistema según el tamaño de los defectos y la presión operativa. En la parte final se calcula el tamaño de los defectos que son tolerables en función del coeficiente de seguridad adoptado, se determina el tamaño de los defectos que son críticos y se aborda el problema del acondicionamiento de las presiones para determinar de una manera rápida la presión reducida a la que debe operarse el gasoducto ante la detección de un defecto "no tolerable" y hasta que el mismo sea reparado.
Abstract
La seguridad en los sistemas de transporte y distribución de gas es uno de los principales aspectos que debe considerarse en el diseño de dichas instalaciones. [...]
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Comportamiento sísmico de columnas de hormigón armado expuestas a temperaturas por debajo del punto de congelación
L. Montejo, M. Kowalsky, T. Hassan

Revista Internacional de Desastres Naturales, Accidentes e Infraestructura Civil (2010). Vol. 10, 2

Abstract
Este artículo recopila los principales resultados de una serie de pruebas experimentales en las cuales columnas circulares de hormigón armado fueron sujetas a incrementos cíclicos de carga lateral y carga axial constante. Durante las pruebas, las columnas fueron expuestas a temperaturas ambiente y a temperaturas por debajo del punto de congelación. Con el objetivo de caracterizar cada aspecto de la respuesta sísmica a temperaturas muy bajas, algunas de las columnas fueron diseñadas para fallar por cortante y otras para fallar por flexión, estas últimas incluyendo columnas convencionales de hormigón armado y tubos de acero rellenos de hormigón armado. Se encontró que las columnas probadas a temperaturas bajas experimentan un incremento en rigidez y en la capacidad a cortante y a flexión. En el caso de las columnas dominadas por flexión, el aumento en capacidad esta acoplado con una reducción en la capacidad de desplazamiento.
Abstract
Este artículo recopila los principales resultados de una serie de pruebas experimentales en las cuales columnas circulares de hormigón armado fueron sujetas a incrementos [...]
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Método de análisis para vigas pre-flexionadas basado en estándares de Norte América
U. Valdes, G. Portela, T. Stanton, W. Varela, G. Velázquez

Revista Internacional de Desastres Naturales, Accidentes e Infraestructura Civil (2010). Vol. 10, 2

Abstract
Este artículo presenta una descripción del análisis de vigas pre-flexionadas con aplicación a superestructuras de puentes. El sistema consiste de vigas compuestas de acero y hormigón armado que son sometidas a pre-esfuerzos producidos por momentos flectores inducidos durante la etapa inicial de su construcción. El método de análisis está basado en la filosofía de esfuerzos admisibles en los materiales que conforman la viga. Se adoptaron los límites establecidos por las normas de la "American Association of State and Highway Transportation Officials" (AASHTO) para sistemas convencionales de concreto pre-esforzado y de acero. Además, este artículo presenta formulaciones para estimar la capacidad nominal a flexión del sistema, considerando criterios de plasticidad en los materiales (AASHTO-LRFD).
Abstract
Este artículo presenta una descripción del análisis de vigas pre-flexionadas con aplicación a superestructuras de puentes. El sistema consiste [...]
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Una mirada a los diez años de publicación de la revista
L. Suárez, L. Godoy

Revista Internacional de Desastres Naturales, Accidentes e Infraestructura Civil (2010). Vol. 10, 2

Abstract
Editorial: Una mirada a los diez años de publicación de la revista
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Un método simplificado de newton para calcular la raíz cuadrada de una matriz real simétrica definida positiva
A. Mexía, O. Aldama

Rev. int. métodos numér. cálc. diseño ing. (2010). Vol. 26, 1

Abstract
One of the numerically stable methods to calculate he Squire root of a matrix is the Newton’s Method, but it has the disadvantage that in each iteration it is necessary to solve a Sylvester’s matrix equation for full matrix, which is computationally expensive. Modifications to the method have been made, resulting a pair of simplified iterations, but it has been proved, through the perturbations theory, that these are numerically unstable. In this article, a simplified alternative iteration of Newton’s Method for the calculation of the square root of a positive definite real matrix is presented, which is attractive for being convergent, computationally economic and, for practical purposes, numerically stable.
Abstract
One of the numerically stable methods to calculate he Squire root of a matrix is the Newton’s Method, but it has the disadvantage that in each iteration it is necessary [...]
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Técnica de visualización científica para datos escalares discretos
H. Herrera, Y. López, A. Esquivel, C. Morfa

Rev. int. métodos numér. cálc. diseño ing. (2010). Vol. 26, 1

Abstract
The scientific visualization of continuous scalar data is currently widely used. New formulations based on particles or point clouds, like the Discrete Element Method, Mesh Free Methods and some more traditional methods such as the Finite Elements Method of Points, Finite Volume Method, among others, has allowed a better analysis of material structures and their behaviour, specifically in the area of engineering. This paper describes a new scientific visualization technique related to the representation of scalar discrete data that can be considered a modification to the way discrete data are visualized now days, known as tiny polygons. It is pretended that this technique be extended to any other method, rather than the mentioned above, capable of generate discrete scalar data or combination of them with continuous data. In the implementation of the scientific visualization technique presented in this paper cuaternions are used, with the aim of forming the figures that eventually will be displayed and one of the approaches to the nearest neighbour problem is used too, with the purpose of improving the computational complexity. Furthermore it is discussed the impact of this technique to obtain information from the final image.
Abstract
The scientific visualization of continuous scalar data is currently widely used. New formulations based on particles or point clouds, like the Discrete Element Method, Mesh [...]
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Cálculo directo de la carga crítica de pandeo de pórticos. Parte II
M. Pérez, A. Iván

Rev. int. métodos numér. cálc. diseño ing. (2010). Vol. 26, 1

Abstract
In a previous article, we presented a mathematical tool for the systematic calculation of the critical buckling load and the buckling mode of any frame, under some simplificative hypothesis. The present work extends this formulation to provide greater generality, considering the possibility of analyzing variable section beams under any kind of loads (including any distributed load and linear variation of the temperature in the edge of the profile). With this purpose, we consider the equilibrium equations of each beam in its deformed configuration, under the hypothesis of infinitesimal strains and displacements, so called First-Order Theory, resulting in a system of di®erential equations with variable coefficients for each element. To obtain the nonlinear response of the frame, it is necessary to impose in each beam end the compatibility of displacements and the equilibrium of forces and moments, also in the deformed configuration. The solution is obtained by requiring that the total variation of potential energy is zero at the instant of buckling. The objective of this work is to develop a systematic method to determine the critical buckling load and the buckling mode of any frame, without using the common simplifications usually assumed in matrix analysis or finite element approaches. This allows us to obtain precise results regardless of the discretization done.
Abstract
In a previous article, we presented a mathematical tool for the systematic calculation of the critical buckling load and the buckling mode of any frame, under some simplificative [...]
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Dimensionamento de plataformas offshore de concreto utilizando a teoria de cascas de tres camadas
C. Friaca, M. Barbosa, T. Bittencourt, M. Machado

Rev. int. métodos numér. cálc. diseño ing. (2010). Vol. 26, 1

Abstract
The concrete ffshore platforms, which are subjected a several loading combinations and, thus, requires an analysis more generic possible, can be designed using the concepts adopted to shell elements, but the resistance must be verify in particular cross- sections to shear forces. This work about design of shell elements will be make using the three-layer shell theory. The elements are subject to combined loading of membrane and plate, totalizing eight components of internal forces, which are three membrane forces, three moments (two out-of-plane bending moments and one in-plane,or torsion, moment) and two shear forces. The design method adopted, utilizing the iterative process proposed by Lourenço & Figueiras (1993) obtained from equations of equilibrium developed by Gupta (1896), will be compared to results of experimentally tested shell elements found in the literature using the program DIANA.
Abstract
The concrete ffshore platforms, which are subjected a several loading combinations and, thus, requires an analysis more generic possible, can be designed using the concepts [...]
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Análisis estructural de muros de mampostería asistido mediante fotografía digital para la generación de la malla
D. Capua, V. Pérez-Gracia, R. González-Drigo

Rev. int. métodos numér. cálc. diseño ing. (2010). Vol. 26, 1

Abstract
This paper presents a proposed methodology developed to obtain the geometry of masonry walls. The methodology is based on the automatic recognition of boundaries. The geometry is used to proceed to the numerical simulation of damages based on a simple model, which allows determinate the cracking process due the tensile stresses in joints. Masonry units are considered as lineal and elastic elements, and the non-elastic processes are considered to exist only in the joints. Two examples are included showing two different walls: a regular mansonry wall built with bricks, and an irregular masonry wall with limestone stones as masonry units.
Abstract
This paper presents a proposed methodology developed to obtain the geometry of masonry walls. The methodology is based on the automatic recognition of boundaries. The geometry [...]
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Análisis numérico de estructuras de hormigón reforzadas con FRP por medio de la teoría de mezclas serie/paralelo
M. Molina, S. Oller, A. Barbat, X. Martínez

Rev. int. métodos numér. cálc. diseño ing. (2010). Vol. 26, 2

Abstract
The numerical simulation of composite materials is a field under continuous development. Its application to structural design has shown important improvements, leading to a better simulation of strengthened structures. This paper uses the serial/parallel mixing theory to predict the mechanical behavior of composites. This theory uses the constitutive equations of the component materials to obtain the composite performance. The advantages provided by this formulation to simulate concrete structures reinforced or retrofitted with Fiber Reinforced Polymers (FRP) will be shown from the analysis of several finite element models, consisting of a set of concrete frames with different strengthening configurations. The results obtained will show that the use of this theory to simulate FRP reinforced structures improves their analysis and design.
Abstract
The numerical simulation of composite materials is a field under continuous development. Its application to structural design has shown important improvements, leading to [...]
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XFEM+: Una modificación de XFEM para mejorar la precisión de los flujos locales en problemas de difusión con conductividades muy distintas
F. F.Cordero, P. Díez

Rev. int. métodos numér. cálc. diseño ing. (2010). Vol. 26, 2

Abstract
When applied to diffusion problems in a multiphase setup, the popular XFEM strategy suffers of an inaccurate representation of the local fluxes in the vicinity of the interphase. The XFEM enrichment improves the global quality of the solution but it is not enforcing any local feature to the fluxes. Thus, the resulting numerical fluxes in the vicinity of the interphase are not realistic. This paper introduces an additional restriction to the XFEM formulation aiming at properly reproducing the features of the local fluxes in the transition zone. This approach is denoted as XFEM+ and requires adding linear constrains to the XFEM algebraic system. The XFEM+ strategy is applied to several examples and the solutions obtained show a spectacular improvement with respect to the standard XFEM.
Abstract
When applied to diffusion problems in a multiphase setup, the popular XFEM strategy suffers of an inaccurate representation of the local fluxes in the vicinity of the interphase. [...]
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Simulación por elementos finitos de la biomecánica del corazón fetal
E. Peña, J. Ohayon, Y. Usson, A. Azancot, M. Doblaré

Rev. int. métodos numér. cálc. diseño ing. (2010). Vol. 26, 2

Abstract
The purpose of this research is to study the fetal heart biomechanics during cardiac cycle. A 3D FEM of the human fetal heart (FH) is built by using the geometry and the ¯ber orientation measurements of a post-mortem FH. An anisotropic hyperelastic constitutive law describing the mechanical properties of the active myocardium is used. Kinematics of the heart and ejection fraction predicted by the model are compared with experimental observations. Our model can quantify the transmural distribution of strains and stresses during the cardiac cycle. Several authors supported the idea that fetal growth depends on the mean wall stress averaged through the space and during the cardiac cycle. For this reason, the results obtained in this work can be relevant in order to better understand the human FH growth process.
Abstract
The purpose of this research is to study the fetal heart biomechanics during cardiac cycle. A 3D FEM of the human fetal heart (FH) is built by using the geometry and the ¯ber [...]
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Una formulación numérica de volúmenes finitos de alto orden basada en el método de mínimos cuadrados móviles para flujo compresible
X. Nogueira, L. Cueto-Felgueroso, I. Colominas

Rev. int. métodos numér. cálc. diseño ing. (2010). Vol. 26, 2

Abstract
In this work we show a numerical methodology for the resolution of compressible ows in both,structured and unstructured grids. The Moving Least Squares method (MLS) is used for the computation of the gradients and successive derivatives in a higherorder nite volume framework. Using the multiresolution properties of the MLS methodology, we dene a shock-detection methodology. This new methodology allows the extension of slope limiters to nite volume methods with order higher than two. We present some numerical examples that show the accuracy and robustness of the numerical method.
Abstract
In this work we show a numerical methodology for the resolution of compressible ows in both,structured and unstructured grids. The Moving Least Squares method (MLS) is used [...]
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Experimentos numéricos sobre ecuaciones de reacción convección difusión con divergencia nula del campo de velocidad
D. Garzón-Alvarado, C. Galeano, J. Mantilla

Rev. int. métodos numér. cálc. diseño ing. (2010). Vol. 26, 2

Abstract
This article studies the effect of the inclusion of the transport term in the reaction-diffusion equations, through toroidal velocity fields. The formation of Turing patterns in diffusion-advection-reaction problems is studied specifically, considering the Schnacken- berg reaction kinetics and glycolysis models. Four cases are analyzed and solved numerically using finite elements. Is found that, for the glycolysis models, the advective effect totally modifies the form of the obtained Turing patterns with diffusion-reaction; whereas for the problems of Schnackenberg, the original patterns distort themselves slightly, making them to rotate in the direction of the velocity field. Also this work was able to determine, that for high values of velocity, the advective effect surpasses the difusive one and the instability by diffusion is eliminated. On the other hand for very low values in the velocity field, the advective effect is not considerable and there is no modification in the original Turing pattern.
Abstract
This article studies the effect of the inclusion of the transport term in the reaction-diffusion equations, through toroidal velocity fields. The formation of Turing patterns [...]
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Interpolación con funciones de base radial y el método del sistema diferencial para identificación de parámetros en acuíferos
M. Morales, F. Mejía

Rev. int. métodos numér. cálc. diseño ing. (2010). Vol. 26, 3

Abstract
Aquifer characterization is an important problem in Geohidrology. The problem consits in estimating phenomenological parameters given piezometric data. In general eld data is obtained in observation wells, which are few and scattered in the aquifer. In this work we propose a solution to the problem of parameter estimation in two parts. First we use an interpolation technique by means of radial basis functions to generate suffcient piezometric data, then we apply the Differential System method for parameter estimation. To illustrate the method, we show a characterization of the Silao-Romita aquifer located in Guanajuato Mexico.
Abstract
Aquifer characterization is an important problem in Geohidrology. The problem consits in estimating phenomenological parameters given piezometric data. In general eld data [...]
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Análisis aeroelástico de chimeneas de acero utilizando elementos no-lineales de lámina sin rotación
J. Valdés, H. Hernández, A. Hernández

Rev. int. métodos numér. cálc. diseño ing. (2010). Vol. 26, 3

Abstract
As alternative to methods presented in several codes around the world to analyze chimneys, an analysis procedure based in the finite element method is presented. To achieve a reliable analysis, a stabilized incompressible fluid with an ALE scheme is used to simulate wind action. Geometrically nonlinear BST rotation-free shell elements are used to model a steel chimney and both schemes are coupled to simulate the fluid-structure interaction of chimneys. Shell elements without rotation degrees improve time solution due to a significant reduction of degrees of freedom in the geometrically nonlinear system. A strong coupling scheme with Aitken relaxation method is used to ensure convergence. Detailed theory for fluid, structure and interaction can be founded in [1]. Differences between code analysis and the proposed procedure are presented for a case of study.
Abstract
As alternative to methods presented in several codes around the world to analyze chimneys, an analysis procedure based in the finite element method is presented. To achieve [...]
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Aproximación del proceso de falla en sólidos con elementos finitos mixtos usando de daño continuos
G. Juárez, A. Ayala

Rev. int. métodos numér. cálc. diseño ing. (2010). Vol. 26, 3

Abstract
This paper presents nonlinear mixed formulations to simulate the material failure process in solids by its finite element approximation. The formulations presented are the corresponding virtual work by the virtual stresses and displacements and the virtual work by displacements and strains. Both formulations presented are derived from the principle of virtual work with four independent variables. The beha- viour of the material is governed by an isotropic continuum damage model equipped with two internal variables at each integration point. In the numerical implementation, the displacement-stress formulation presents numerical problems when the behaviour of the material approaches complete damage, thus only the displacement-strain formulation was implemented. The advantage of the strain-displacement over a typical displacement formulation to simulate the material failure process with damage models as strain concentrations is discussed. To show the validity and illustrate the effectiveness of the displacement-strain formulation, results from some representative numerical examples are presented and discussed within the framework of continuum approximations.
Abstract
This paper presents nonlinear mixed formulations to simulate the material failure process in solids by its finite element approximation. The formulations presented are the [...]
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El problema de medir la diversidad en conjuntos no dominados y una propuesta de solución
G. Lizárraga, S. Botello, P. Perez

Rev. int. métodos numér. cálc. diseño ing. (2010). Vol. 26, 3

Abstract
Diversity is a very important property for non-dominated sets. The diversity is a measure of how much information is contained in a non-dominated set. Evaluating diversity has been a diffcult issue in multi-objective evolutionary computation. Many diversity performance measures fail in simple cases. In this work, we describe the most common problems in diversity performance measures and we propose a more robust approach. The problem with most performance measures is that they consist on evaluating the standard deviation of the distances between the elements of the non-dominated sets, or a similar calculation. This dependence on a standard deviation produces a high sensibility to small changes in the non-dominated sets. Our approach is based on an hype-volume associated to the non-dominated set. The behavior of this hyper-volume is exactly what we expect from a diversity performance measure. We tested our approach using a benchmark published in bibliography, showing an exceptional performance.
Abstract
Diversity is a very important property for non-dominated sets. The diversity is a measure of how much information is contained in a non-dominated set. Evaluating diversity [...]
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Un algoritmo de estimación de distribución basado en una red bayesiana para optimización topológica de estructuras
S. P, S. R, A. A.

Rev. int. métodos numér. cálc. diseño ing. (2010). Vol. 26, 3

Abstract
The topological optimization problema is stated as follows: to find the best shape of a mechanical structure subject to certain service conditions. Usually, the topological optimization problem is tackled by starting from an initial structure which is modified by adding parts, generating gaps, modifying dimensions or the shape contour. This work presents a novel proposal on topological optimization which uses an Estimation of Distribution Algorithm (EDA) based on a Bayesian network. The EDA works as follows: propose a set of candidate solutions (population),the candidate solutions are generated according to a probability distribution, the population is evaluated on the objective function and contraints, and finally, the best structures are selected and used to recomputed the search distribution, and so on. The objective function is the structure weight, and the constraints are maximum Von Mises Stress,the node displacement and practical conditions such as connectivity of all the parts of the structure. The results show that the proposal is capable of designing low weight structures which fulfill the service conditions.
Abstract
The topological optimization problema is stated as follows: to find the best shape of a mechanical structure subject to certain service conditions. Usually, the topological [...]
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Evaluación numérica del proceso de granallado y determinación del campo de esfuerzos residuales por medio del método de respuesta de grieta
G. Urriolagoitia-Sosa, G. Urriolagoitia-Calderón, L. Hernández, B. al.

Rev. int. métodos numér. cálc. diseño ing. (2010). Vol. 26, 3

Abstract
In the open literatura around the world, it has been very well established the benefits that produces the shot peening process. Nevertheless, this process is a task, in some of the cases, of the development of handcrafted and/ or dependent on the experience of the workman. One of the principal virtues of this process, is the strengthening of the surface and increase in the yield stress of the material. This strengthening or increase of the resistance in the material, owes to the induction of a residual stress field of compressive type. The induction of this type of effect is extremely beneficial for the component, since this operation does that the elements submitted to cyclical loads raise its fatigue resistance (crack propagation)on the surface and could have hereby a longer useful life, and in the order hand, the applied loads to these elements could raise considerably. In this article, it is presented a comparison of the obtained residual stress field by shot peening by two methods, by the analytical and the finite element method (FEM), in order to obtain a confinable method for the evaluation of residual stresses, which approaches in major measurement to the registered ones by the experimental procedure. The numerical analysis performed in this work, it was done by 2D simulation, considering quasi-static conditions and not accounting random shot in the shot peening process. Also it is present the results obtained in the effect that the ball size produced. Hereby, in a later analyses, it will be possible to do an evaluation of the best results obtained by means of the FEM, changing certain factors that throw the suitable conditions of the parameters in the experimental tests, reducing cost and time.
Abstract
In the open literatura around the world, it has been very well established the benefits that produces the shot peening process. Nevertheless, this process is a task, in some [...]
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Resolución numérica de las ecuaciones de la magnetohidrodinámica en el proceso Czochralski para la obtención de cristales semiconductores
N. Hernández-Silva, R. Codina

Rev. int. métodos numér. cálc. diseño ing. (2010). Vol. 26, 3

Abstract
The objective of this work is to introduce and numerically solve the mathematical model for the bahavior of liquid semiconductors in the Czochralski process to obtain semiconductor crystals under the influence of a magnetic field. Such model is framed within the Magnetohydrodynamics equations. The numerical solution of this mathematical model presents important difficulties due to the involvement of phenomena from Fluid Mechanics, Electromagnetism and Heat Transfer. In order to numerically solve this model a stabilized finite element approximation based on tha algebraic version of a subgrid scale model in used. This approach makes possible to satisfy the free divergence condition over the velocity of the fluid together with the free divergence condition over the magnetic field and also to avoid numerical oscillations. The numerical scheme used in this work is based on the scheme proposed in (1). This numerical scheme is applied to the numerical benchmark proposed by Bückle (2). Such example is the most common numerical benchmark for the Czochralski process. The cases analysed in this work only differ from those proposed by Bückle in the fact that a magnetic field has been added. The use of magnetic fields in the Czochralski process is headed to diminish and suppress the perturbations inthe liquid which can originate defects in the semiconductor cristal.
Abstract
The objective of this work is to introduce and numerically solve the mathematical model for the bahavior of liquid semiconductors in the Czochralski process to obtain semiconductor [...]
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Solución de ecuaciones diferenciales elípticas en regiones planas irregulares usando mallas convexas generadas por métodos variacionales empleando elementos finitos
F. Domínguez-M, M. Equihua, S. Mendoza, J. Tinoco

Rev. int. métodos numér. cálc. diseño ing. (2010). Vol. 26, 3

Abstract
Recently, in order to approximate the solution of a partial differential equation overa n irregular planar domains, several efficient and robust variational methods designed to generate smooth and convex grids on such regions have been proposed (3-9,11-14). For those grids, several schemes have also been designed, and for them it is quite clear how effortless the use of the grid logical rectangular data structure can be (1,2,15). This fact makes these schemes attractive competitors to the finite element methods, which use unstructured grids and, in consequence, non trivial data structures inorder to save the grid information. Nevertheless, one must acknowledge that, since triangulatiolns have been known for a while , finite element methods have been known for a while, finite element methods have been thoroughly studies, and there is a lot of research on how to assemble the systems required to solve a large class of equations. Thus, a question that arises in a natural way is how competitive are FE/FD methods, when applied to the structured convex grids generated for irregular regions-which often have elongated elements-, in order to produce the numerical solution in an easy computational way using structured grids and, at the same time, accurate enough by using finite elements. In this paper we show how to accomplish this goal, and a series of numerical examples at the end provided a good example of the validity of the approach.
Abstract
Recently, in order to approximate the solution of a partial differential equation overa n irregular planar domains, several efficient and robust variational methods designed [...]
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Análisis numérico de las funciones corriente circulación y vorticidad, para flujo rotatorio con frontera rígida
A. R, R. C., J. G., H. P., A. V.

Rev. int. métodos numér. cálc. diseño ing. (2010). Vol. 26, 3

Abstract
The tangential vorticity function, circulation and meridian stream that form in a closed rotating cylinder are analyzed. The cylinder has a rotating bottom whereas the lateral surface and the top are fixed. The results are presented as graphs that compare the mentioned functions for different aspect ratios. The comparing aspect ratios: 0.5, 1.0 and 2.0. In comparing the 2.0 aspect ratio versus the 1.0 aspect ratio; it is found that the stream function diminished a 29.63%, whereas the circulation does not change and the vorticity decreases 65.91%. On the other hand comparison of the cylinder with aspect ratio 0.5 against the one with aspect ratio 1; gives that the stream function increases 1.4 times; that the circulation increases 3.45 times and the vorticirty increases 0.7 times. The analysis was made for a 3 x 104 Reynolds number. The mentioned results give an indication of the influence of the aspect ratio as to the motion inside the cylinder. Further investigation is required in order to apply the results to particular conditions of mixing or another practical application.
Abstract
The tangential vorticity function, circulation and meridian stream that form in a closed rotating cylinder are analyzed. The cylinder has a rotating bottom whereas the lateral [...]
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Modelado del daño en sólidos mediante formulaciones variacionales de discontinuidades interiores
J. Retama, A. Ayala

Rev. int. métodos numér. cálc. diseño ing. (2010). Vol. 26, 3

Abstract
This paper presents different variational formulations for the modeling of damage in solids by the embedded discontinuity formulation. Initially the energy functional, for a continuum medium, if presented from which; the displacement and mixed strain-displacement formulations, of the finite element method, are developed for a solid where the damage is modeled as a discontinuity. To validate the theoretical consistency of the developed formulations, a numerical example is presented. Comments and conclusions, derived from this study, are given at the end of the paper.
Abstract
This paper presents different variational formulations for the modeling of damage in solids by the embedded discontinuity formulation. Initially the energy functional, for [...]
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Construyendo soluciones en serie de potencias de modelos diferenciales aleatorios
L. Villafuerte, J. Cortés, L. Jódar

Rev. int. métodos numér. cálc. diseño ing. (2010). Vol. 26, 3

Abstract
This paper deals with the construction of analytic-numerical solutions of random linear differential equations by means of a power series method. Sufficient conditions for the mean square convergence of the series solution are established. The mean and variance functions of the approximate solution stochastic process are also computed. Lastly, several illustrative examples where the proposed methods is compared with respect to Monte Carlo approximations are included.
Abstract
This paper deals with the construction of analytic-numerical solutions of random linear differential equations by means of a power series method. Sufficient conditions for [...]
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Un nuevo método de empaquetamiento de partículas: Aplicaciones en el modelado del tejido óseo
I. Pérez, Y. Pérez, C. Recarey, M. Cerrolaza

Rev. int. métodos numér. cálc. diseño ing. (2010). Vol. 26, 4

Abstract
Packing- particle methods to simulate compact and spongy bone-tissue are presented. The methods ara based on moddified front-advance algorithms, able to reduce the density of large sets of circles or spheres. As well, elliptical shape holes to represent trabeculae in spongy bone are allowed. Some preliminary results of bone modeling using the methods proposed are presented and discussed.
Abstract
Packing- particle methods to simulate compact and spongy bone-tissue are presented. The methods ara based on moddified front-advance algorithms, able to reduce the density [...]
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Modelado termomecánico del proceso de Friction Stir Welding utilizando la geometría real de la herramienta
D. Santiago, G. Lombera, S. Urquiza, C. Saracibar, M. Chiumenti

Rev. int. métodos numér. cálc. diseño ing. (2010). Vol. 26, 4

Abstract
This work deals with the computational modeling of Friction Stir Welding (FSW) processes including the discretization of the tools. The mechanical problem has been solved using a Stokes viscoplastic flow model with a suitable constitutive law for the range of deformation rates induced in the process. The thermal problem has been solved using an advection-diffusion model using an ALE formulation. Finite element formulations have been implemented for both problems. Two-dimensional and three-dimensional FSW problems have been solved under a number of particular process conditions and a particular tool geometry. Results obtained for the material flow around the tool have been compared with published experimental results, obtained under the same process conditions. A good correlation has been obtained between the numerical and the experimental results. The patterns of the material flow reported in the references, which were obtained using experimental techniques with tracers, have been identified performing the post-process of the results obtained for the material flow using computational visualization techniques with tracers. The role played by those visualization techniques in the analysis of the material flow around the tool, leading to a better understanding of the phenomena involved in the FSW process, is pointed out.
Abstract
This work deals with the computational modeling of Friction Stir Welding (FSW) processes including the discretization of the tools. The mechanical problem has been solved [...]
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Aspectos computacionales del método local discontinuous Galerkin para mallas no conformes en 2D
P. Castillo

Rev. int. métodos numér. cálc. diseño ing. (2010). Vol. 26, 4

Abstract
This article describes an implementation of the Local Discontinuous Galerkin (LDG) method applied to a general elliptic boundary value problem in 2D. The implementation takes advantage of some intrinsic properties of the method, in particular, the use of non conforming meshes with an arbitrary but fixed number of hanging nodes and polynomial approximations with variable degree. A detailed description of efficient data structures yielding a fast assembly of the linear system in its mixed formulation is presented. This implementation can be used as a model for hp adaptive codes.
Abstract
This article describes an implementation of the Local Discontinuous Galerkin (LDG) method applied to a general elliptic boundary value problem in 2D. The implementation takes [...]
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Influencia da velocidade, do espaçamento e do número de veículos sobre a resposta dinamica de pontes rodoviárias de concreto armado
E. Lopes, J. Silva, M. Nóbrega

Rev. int. métodos numér. cálc. diseño ing. (2010). Vol. 26, 4

Abstract
Neste trabalho de pesquisa desenvolve-se um estudo paramétrico para análise da resposta dinámica de pontes rodoviárias de concreto armado, devido à travessia de comboios de veículos sobre o pavimento irregular dessas obras-de-arte. O estudo é feito com base em uma metodologia de análise, no dominio do tempo, de acordo com um modelo estatástico. O modelo matemático empregado para simular o comportamento do sistema "veículo-ponte" considera a participação da massa e da rigidez das viaturas na definição das freqüências do sistema e, conseqüentement, a força de interação entre os veículos e a ponte é afetada pela flexibilidade desta. A ponte é modelada a partir do emprego de elementos finitos de barra unidimensionais e discretizado com massas concentradas e flexibilidade distribuída. O modelo de veículo empregado baseia-se no veículo TB-12 preconizado pela norma brasileira NBR 7188. Este veículo é simulado por sistemas de massas, molas e amortecedores sendo descrito por graus de liberdade à translaçãó e rotação no plano. As irregularidades da pista são definidas por um modelo não-determinístico com base na densidade espectral do pavimento. O carregamento sobre a ponte é constituído por sucessões de vículos deslocando-se com velocidade constante sobre a obra. Devido à própria natureza das irregularidades da pista e do comboio de veículos, atenção especial é concetrada na fase permanente da resposta do sistema. São estudadas as respostas de dois modelos estruturais existentes, com base em tabuleiros isitáticos, em concreto armado, com e sem balanços, em seção do tip "T" e duplo "T", respectivamente, em termos de deslocamentos e esforços nas seçõesonde ocorrem os efeitos máximos. As conclusões do trabalho versam sobre a influência da velocidade, espaçamento e do número de veículos, referentes a situações distintas de carregamento, no que tange a resposta dinâmica das pontes rodoviárias de concreto armado. A magnitude dos efeitos dinâmicos associados à interação dos veículos com o pavimento irregular também é investigada.
Abstract
Neste trabalho de pesquisa desenvolve-se um estudo paramétrico para análise da resposta dinámica de pontes rodoviárias de concreto armado, devido [...]
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Dependencia estrutural da capacidade de rotaçao plástica em vigas de concreto armado
A. Gamino, O. Manzoli

Rev. int. métodos numér. cálc. diseño ing. (2010). Vol. 26, 4

Abstract
Neste trabalho a dependencia da capacidade de rotaçao plástica com relaçao às características físicas, geométricas e construtivas das vigas de concreto armado, ou dependencia estrutural da capacidade de rotaçao plástica em vigas de concreto armado, conforme definiçao por Bigaj [1] é avaliada através do Método dos Elementos Finitos. O termo dependencia estru- tural refere-se a relaçao necessária ou interaçao entre o comportamento da estrutura e seus materiais constituintes, tais como concreto e aço ou mesmo fatores geométricos como efeito de escala. O objetivo é conseguir uma melhor compreensao sobre o comportamento nao-linear de elementos de concreto armado e executar estudos paramétricos extensivos por meio do modelo analítico desenvolvido por Bigaj [1] afim de analisar o fenómeno da capacidade de rotaçao plástica em elementos de concreto armado. Supoe-se que somente a ruptura por flexao é relevante devido à capacidade resistente suficiente do elemento ao cisalhamento e torçao. O trabalho inicia-se com uma revisao de literatura a respeito do desenvolvimento da rotaçao plástica em vigas de concreto armado, atentando tanto para aspectos experimentais quanto a aspectos de modelagem analítica. Dá-se enfase especial na introduçao da dependencia estrutural da capacidade de rotaçao plástica em vigas de concreto armado. A dependencia do tamanho do elemento e a propriedade dos materiais de construçaao sao enfatizados. Os componentes essenciais do modelo de Bigaj para o cálculo da capacidade de rotaçao plástica sao discutidos. O comportamento da rotaçao plástica é analisado levando-se em consideraçao a deformaçao localizada em zonas de dano da regiao plastificada. O Modelo de Fissura Fictícia e o Modelo de Zona de Dano na Compressao sao adaptados à Mecanica da Fratura a fim de modelar o comportamento do concreto a traçao e compressao respectivamente. Nas simulaçoes numéricas utilizou-se o programa FEMOOP, um "solver" desenvolvido segundo o Método Elementos Finitos e aplicado para avaliar a ductilidade em vigas segundo uma análise 2D. Exemplos de aplicaçaão são apresentados para avaliar o potencial das implementações cujos modelos forma gerados com o programa GiD desenvolido pelo CIMNE.
Abstract
Neste trabalho a dependencia da capacidade de rotaçao plástica com relaçao às características físicas, geométricas e construtivas [...]
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