Scipedia: Documents published in 2011

La vida es sueño: A Lecture Beginning from the Ending

Scipedia content — Thu, 14 Mar 2019 09:32:11 +0100

The present work studies the dramatic structures of La vida es sueño, focusing on the inaptly called «secondary intrigue» constructed around the character of Rosaura. The presence of motives typical of the comedy of intrigue within this tragedy, moreover the fact that the dramatic system is similar to the system quite often found in the «comedia de burlador», can be explained by a lecture directed backwards, that is to say, beginning from the ending. The marriage of Segismundo and Estrella, which is far from being a coincidence or a convention typical of a happy ending, is considered a fundamental element of the Calderonean inventio to which all the different parts of the tragedy necessarily have to lead, and this is how to explain the function and development of Rosaura.

El Divino Narciso: A Contrafacta of Eco y Narciso?

Scipedia content — Thu, 14 Mar 2019 09:18:48 +0100

Literary works recreated in a religious sense from a profane work are known as «contrafactae». They were developed between the 13th and 16th and even during the 17th century. A contrafactae- writer chooses a profane theme and develops it extensively in order to show an idea related to the Christian tradition. In its most concentrated way of expression, the divinization of profane themes carries out the literary resource of allegory. During the 16th century, many moralized versions of the myth of Narcissus were widely spread. Most of them recreated the one included in Ovid’s (43 a.C.-16 d.C.) Metamorphoses. Such is the case with the auto sacramental El Divino Narciso by the Mexican nun sor Juana Inés de la Cruz, as well as with Eco y Narciso by the Spanish playwright Pedro Calderón de la Barca. The present work analyzes similarities and differences between dramatic moments in both plays. Though sor Juana recreates some aspects from Eco y Narciso’s plot and semantics in her play, it is my opinion that the literary resource of allegory allows her to explore many significance levels related to religious matters, particularly to the Sacrament of Eucharist, a subject of utmost relevance to the auto sacramental as a literary genre. Therefore, I consider that El Divino Narciso cannot be taken as a contrafacta, in a strict sense, of Calderon de la Barca’s drama play Eco y Narciso.

The Enigmatic Textual Transmission of Amado y aborrecido

Scipedia content — Thu, 14 Mar 2019 09:17:00 +0100

The text of Amado y aborrecido, published by Vera Tassis in the Novena parte of Calderón’s Comedias (1691), shows clear signs of deriving from a late and already rather corrupt testimony: the one included in the unauthorized Quinta parte (1677). However, it offers a longer and more coherent text, and its variants seem to reveal the hand of the author. In this paper, two alternative hypotheses are proposed in order to explain these facts. Perhaps the composer of the 1691 text worked from a copy of the Quinta parte accompanied by a list of corrections taken from a more reliable testimony. Or, perhaps, Vera Tassis used the text of a new palace performance of the play, based on the Quinta parte but revised and corrected by Calderón himself. The conclusions may well be relevant for the textual criticism of other plays by the same author.

The Disguise of Madness and the Subversion of Order in La Cisma de Ingalaterra

Scipedia content — Thu, 14 Mar 2019 09:14:25 +0100

This essay intends analyzing the disguise of madness in Calderón’s La Cisma de Ingalaterra, not only as a concrete element of the performance that contributes to Pasquin’s connotation, but also as a dramatic metaphor that is used by Calderón in order to bring on stage the subversion of order and the unmasking of fiction and hypocrisy. concept, whose dramatic construction can be established from symbolic functions of costume. Second, it analyses Pasquin’s clownish aspect, his acting like a theatrical sign of multiple meanings, because it translates a fictional madness that expresses itself at a visual, a verbal and a mimic level at the same time. Moreover, the article deals with some scenic sources based on the concept of inversion, starting from Pasquin’s fiction of madness that, on one hand, is similar to the emblematic figures of the ««fou sage» and the «seeing-blind», and that, on the other hand, points out Enrique’s loss of wisdom.

Unas pocas palabras preliminares

Scipedia content — Thu, 14 Mar 2019 09:11:27 +0100

Flow behaviour of negatively buoyant jets in immiscible ambient fluid

María Jesús Samper — Wed, 06 Mar 2019 13:12:55 +0100

In this paper we investigate experimentally the injection of a negatively buoyant jet into a homogenous immiscible ambient fluid. Experiments are carried out by injecting a jet of dyed fresh water through a nozzle in the base of a cylindrical tank containing rapeseed oil. The fountain inlet flow rate and nozzle diameter were varied to cover a wide range of Richardson Ri(8 × 10−4 < Ri < 1.98), Reynolds Re (467 < Re < 5,928) and Weber We (2.40 < We < 308.56) numbers. Based on the Re, Ri and We values for the experiments, we have determined a regime map to define how these values may control the occurrence of the observed flow types. Whereas Ri plays a stronger role when determining the maximum penetration height, the effect of the Reynolds number is stronger predicting the flow behaviour for a specific nozzle diameter and injection velocity.

A new enrichment space for the treatment of discontinuous pressures in multi‐fluid flows

María Jesús Samper — Thu, 28 Feb 2019 10:42:24 +0100

In this work, a new enrichment space to accommodate jumps in the pressure field at immersed interfaces in finite element formulations, is proposed. The new enrichment adds two degrees of freedom per element that can be eliminated by means of static condensation. The new space is tested and compared with the classical P1 space and to the space proposed by Ausas et al (Comp. Meth. Appl. Mech. Eng., Vol. 199, 1019–1031, 2010) in several problems involving jumps in the viscosity and/or the presence of singular forces at interfaces not conforming with the element edges. The combination of this enrichment space with another enrichment that accommodates discontinuities in the pressure gradient has also been explored, exhibiting excellent results in problems involving jumps in the density or the volume forces.

Numerical simulations of negatively buoyant jets in an immiscible fluid using the Particle Finite Element Method

María Jesús Samper — Thu, 28 Feb 2019 10:26:41 +0100

Negatively buoyant jets consist in a dense fluid injected vertically upward into a lighter ambient fluid. The numerical simulation of this kind of buoyancy‐driven flows is challenging as it involves multiple fluids with different physical properties. In the case of immiscible fluids, it requires, in addition, to track the motion of the interface between fluids and accurately represent the discontinuities of the flow variables.

In this paper, we investigate numerically the injection of a negatively buoyant jet into a homogenous immiscible ambient fluid using the Particle Finite Element Method and compare the two‐dimensional numerical results with experiments on the injection of a jet of dyed water through a nozzle in the base of a cylindrical tank containing rapeseed oil. In both simulations and experiments, the fountain inlet flow velocity and nozzle diameter have been varied to cover a wide range of Froude Fr and Reynolds Re numbers ( 0.1 < Fr < 30, 8 < Re < 1350), reproducing both weak and strong laminar fountains.

The flow behaviors observed for the different numerical simulations fit in the regime map based on the Re and Fr values of the experiments, and the maximum fountain height is in good agreement with the experimental observations, suggesting that particle finite element method is a useful tool for the study of immiscible two‐fluid systems.

Wrinkling and folding analysis of elastic membranes using an enhanced rotation-free thin shell triangular element

María Jesús Samper — Fri, 18 Jan 2019 13:44:22 +0100

This paper presents a formulation for analysis of thin elastic membranes using a rotation-free shell element within an explicit time integration strategy. The applications presented are isotropic/anisotropic rectangular membranes under shear forces and fabric drapes falling over a pedestal. Results are compared with other numerical results existing in the literature.

Possibilities of the particle finite element method for fluid–soil–structure interaction problems

María Jesús Samper — Fri, 21 Dec 2018 11:33:46 +0100

We present some developments in the particle finite element method (PFEM) for analysis of complex coupled problems in mechanics involving fluid–soil–structure interaction (FSSI). The PFEM uses an updated Lagrangian description to model the motion of nodes (particles) in both the fluid and the solid domains (the later including soil/rock and structures). A mesh connects the particles (nodes) defining the discretized domain where the governing equations for each of the constituent materials are solved as in the standard FEM. The stabilization for dealing with an incompressibility continuum is introduced via the finite calculus method. An incremental iterative scheme for the solution of the non linear transient coupled FSSI problem is described. The procedure to model frictional contact conditions and material erosion at fluid–solid and solid–solid interfaces is described. We present several examples of application of the PFEM to solve FSSI problems such as the motion of rocks by water streams, the erosion of a river bed adjacent to a bridge foundation, the stability of breakwaters and constructions sea waves and the study of landslides.

On the need for the use of error‐controlled finite element analyses in structural shape optimization processes

María Jesús Samper — Wed, 19 Dec 2018 13:44:41 +0100

This work analyzes the influence of the discretization error associated with the finite element (FE) analyses of each design configuration proposed by the structural shape optimization algorithms over the behavior of the algorithm. The paper clearly shows that if FE analyses are not accurate enough, the final solution provided by the optimization algorithm will neither be optimal nor satisfy the constraints. The need for the use of adaptive FE analysis techniques in shape optimum design will be shown. The paper proposes the combination of two strategies to reduce the computational cost related to the use of mesh adaptivity in evolutionary optimization algorithms: (a) the use of an algorithm for the mesh generation by projection of the discretization error, which reduces the computational cost associated with the adaptive FE analysis of each geometrical configuration and (b) the successive increase of the required accuracy of the FE analyses in order to obtain a considerable reduction of the computational cost in the early stages of the optimization process.

Consistent pressure Laplacian stabilization for incompressible continua via higher‐order finite calculus

María Jesús Samper — Wed, 19 Dec 2018 13:33:37 +0100

We present a stabilized numerical formulation for incompressible continua based on a higher‐order Finite Calculus (FIC) approach and the finite element method. The focus of the paper is on the derivation of a stabilized form for the mass balance (incompressibility) equation. The simpler form of the momentum equations neglecting the non‐linear convective terms, which is typical for incompressible solids, Stokes flows and Lagrangian flows is used for the sake of clarity. The discretized stabilized mass balance equation adds to the standard divergence of velocity term a pressure Laplacian and an additional boundary term. The boundary term is relevant for the accuracy of the numerical solution, especially for free surface flow problems. The Laplacian and boundary stabilization terms are multiplied by non‐linear parameters that have an extremely simple expression in terms of element sizes, the pressure and the discrete residuals of the incompressibility equation and the momentum equations, thus ensuring the consistency of the method. The stabilized formulation allows solving the incompressible problem iteratively using an equal‐order interpolation for the velocities (or displacements) and the pressure, which are the only unknowns. The use of additional pressure gradient projection variables, typical of many stabilized methods, is unnecessary.

The formulation is particularly useful for heterogeneous incompressible materials with discontinuous material properties, as it allows computing all the stabilization matrices at the element level. Details of the finite element formulation are given. The good behaviour of the new pressure Laplacian stabilization (PLS) technique is shown in simple but demonstrative examples of application. A very accurate solution was obtained in all cases in 2–3 iterations. Copyright © 2010 John Wiley & Sons, Ltd.

A fourth‐order compact scheme for the Helmholtz equation: Alpha‐interpolation of FEM and FDM stencils

María Jesús Samper — Wed, 19 Dec 2018 12:43:36 +0100

We propose a fourth‐order compact scheme on structured meshes for the Helmholtz equation given by R(φ):=f(x)+Δφ+ξ2φ=0. The scheme consists of taking the alpha‐interpolation of the Galerkin finite element method and the classical central finite difference method. In 1D, this scheme is identical to the alpha‐interpolation method (J. Comput. Appl. Math. 1982; 8(1):15–19) and in 2D making the choice α=0.5 we recover the generalized fourth‐order compact Padé approximation (J. Comput. Phys. 1995; 119:252–270; Comput. Meth. Appl. Mech. Engrg 1998; 163:343–358) (therein using the parameter γ=2). We follow (SIAM Rev. 2000; 42(3):451–484; Comput. Meth. Appl. Mech. Engrg 1995; 128:325–359) for the analysis of this scheme and its performance on square meshes is compared with that of the quasi‐stabilized FEM (Comput. Meth. Appl. Mech. Engrg 1995; 128:325–359). In particular, we show that the relative phase error of the numerical solution and the local truncation error of this scheme for plane wave solutions diminish at the rate O((ξℓ)4), where ξ, ℓ represent the wavenumber and the mesh size, respectively. An expression for the parameter α is given that minimizes the maximum relative phase error in a sense that will be explained in Section 4.5. Convergence studies of the error in the L2 norm, the H1 semi‐norm and the l∞ Euclidean norm are done and the pollution effect is found to be small. Copyright © 2010 John Wiley & Sons, Ltd.

An adaptive finite point method for the shallow water equations

María Jesús Samper — Mon, 17 Dec 2018 13:14:44 +0100

An adaptive Finite Point Method (FPM) for solving shallow water problems is presented. The numerical methodology we propose, which is based on weighted‐least squares approximations on clouds of points, adopts an upwind‐biased discretization for dealing with the convective terms in the governing equations. The viscous and source terms are discretized in a pointwise manner and the semi‐discrete equations are integrated explicitly in time by means of a multi‐stage scheme. Moreover, with the aim of exploiting meshless capabilities, an adaptive h‐refinement technique is coupled to the described flow solver. The success of this approach in solving typical shallow water flows is illustrated by means of several numerical examples and special emphasis is placed on the adaptive technique performance. This has been assessed by carrying out a numerical simulation of the 26th December 2004 Indian Ocean tsunami with highly encouraging results. Overall, the adaptive FPM is presented as an accurate enough, cost‐effective tool for solving practical shallow water problems. Copyright © 2011 John Wiley & Sons, Ltd.

Simulación del comportamiento al fuego de paneles de lana de roca

María Jesús Samper — Wed, 28 Feb 2018 15:07:30 +0100

En este trabajo se presenta el informe correspondiente al estudio del comportamiento bajo la acción del fuego de un panel de lana de roca fabricado por la empresa de prefabricados Pretersa-Prenavisa. La referencia de la pieza a estudiar es PANEL DE 20 CON LANA DE ROCA con una longitud de 10m.

El objetivo final es analizar la estabilidad global del panel sometido a la acción del fuego. Dicha estabilidad global puede verse comprometida si las deformaciones térmicas son suficientemente grandes como para que el panel salga fuera del pilar de borde que le confiere estabilidad lateral.

Estudio de la seguridad de presas e identificación de escenarios de riesgo mediante sistemas inteligentes (SEPRISIS)

María Jesús Samper — Wed, 28 Feb 2018 15:06:43 +0100

El proyecto SEPRISIS tiene como objetivo el desarrollo de sistemas inteligentes basados en redes neuronales, para analizar el comportamiento de una presa, y con ello prever e identificar escenarios de riesgo. Dichos sistemas inteligentes servirán por tanto, como herramienta de soporte a la toma de decisiones.

Analysis of the discharge capacity of radial gated spillways using numerical modelling application to Oliana dam

Scipedia content — Fri, 24 Nov 2017 09:17:41 +0100

Current paper focuses on the analysis of radial gated spillways, which are analyzed by the solution of a numerical model. The Oliana Dam study case is considered and the discharge capacity is predicted both by the application of a level-set based free-surface solver and by the use of traditional empirical formulations The results of the analysis are then used in training an Artificial Neural Network so to allow real-time predictions of the discharge in any situation of energy head and gate opening within the operation range of the reservoir. The comparison of the results obtained with the different methods shows that numerical models can be useful as a predictive tool for the analysis of the hydraulic performance of radial-gated spillways, and highlights some drawbacks regarding the application of the empirical formulas.

Contribution to the definition of non deterministic robust optimization in aeronautics accounting with variable uncertainties

María Jesús Samper — Fri, 20 Oct 2017 11:06:15 +0200

Shape optimization is a largely studied problem in aeronautics. It can be applied to many disciplines in this field, namely efficiency improvement of engine blades, noise reduction of engine nozzles, or reduction of the fuel consumption of aircraft. Optimization for general purposes is also of increasing interest in many other fields. Traditionally, optimization procedures were based on deterministic methodologies as in Hamalainen et al (2000), where the optimum working point was fixed. However, not considering what happens in the vicinity of the defined working conditions can produce problems like loose of efficiency and performance. That is, in many cases, if the real working point differs from the original, even a little distance, efficiency is reduced considerably as pointed out in Huyse and
Lewis (2001). Non deterministic methodologies have been applied to many fields (Papadrakakis, Lagaros and Tsompanakis, 1998; Plevris, Lagaros and Papadrakakis, 2005). One of the most extended nondeterministic methodologies is the stochastic analysis. The time consuming calculations required on Computational Fluid Dynamics (CFD) has prevented an extensive application of the stochastic analysis to shape optimization. Stochastic analysis was firstly developed in structural mechanics, several years ago. Uncertainty quantification and variability studies can help to deal with intrinsic errors of the processes or methods. The result to consider for design optimization is no longer a point, but a range of values that defines the area where, in average, optimal output values are obtained. The optimal value could be worse than other optima, but considering its
vicinity, it is clearly the most robust regarding input variability. Uncertainty quantification is a topic of increasing interest from the last few years. It provides several techniques to evaluate uncertainty input parameters and their effects on the outcomes.

This research presents a methodology to integrate evolutionary algorithms and stochastic analysis, in order to deal with uncertainty and to obtain robust solutions.

Anatomía computacional: una metodologia eficiente basada en imágenes médicas para la generación de modelos 3D

María Jesús Samper — Thu, 19 Oct 2017 16:48:00 +0200

Este libro está orientado a introducir en los conceptos generales de la reconstrucción 3D de estructuras anatómicas y presentar una metodología para la obtención de modelos geométricos de tejidos del cuerpo humano a partir de imágenes médicas, útiles para su discretización con los métodos numéricos, con el objetivo de poder simular su comportamiento y planificar intervenciones quirúrgicas. Para este fin, se implementaron diferentes técnicas de procesamiento en imágenes médicas de diversas modalidades, lo que nos permitió obtener geometrías precisas de los tejidos de interés en un corto tiempo de procesamiento.

La amplia gama de estudios basados en la reconstrucción tridimensional de tejidos del ser humano a partir de las imágenes médicas, demuestran que éstas han revolucionado los métodos clínicos de diagnosticar y tratar las enfermedades. No sólo permiten a los médicos y científicos obtener información vital observando el interior del cuerpo humano de una manera no invasiva, además, combinadas con técnicas de procesamiento digital, constituyen herramientas para la obtención de modelos geométricos de nuestro cuerpo más precisos sin necesidad de ingresar al paciente.

Refuerzo de pavimentos sobre arcillas expansivas

Scipedia content — Wed, 28 Jun 2017 11:38:30 +0200

El refuerzo de la capa base de pavimentos se ha utilizado a los efectos de: (i) aumentar la vida útil de un pavimento manteniendo el espesor de la capa base, o (ii) disminuir el espesor de la capa base manteniendo la vida útil del pavimento. Este artículo describe una tercera aplicación del refuerzo basal de pavimentos, a saber, la mitigación de grietas longitudinales inducidas en pavimentos construidos sobre subrasantes compuestas de arcillas expansivas. Aunque todavía existe la necesidad de una mejor caracterización de las propiedades correspondientes a la interacción suelo-refuerzo, observaciones de campo ponen de relieve los importantes beneficios asociados con el uso de geomallas en pavimentos construidos sobre arcillas expansivas.

Comportamiento sísmico de túneles

Scipedia content — Wed, 28 Jun 2017 11:37:53 +0200

Existe suficiente evidencia de campo que demuestra que las estructuras enterradas son vulnerables a los efectos sísmicos y por tanto se deben diseñar para poder soportar las deformaciones del suelo durante el terremoto. Si la estructura está suficientemente alejada del epicentro, se puede realizar un cálculo estático con el que se obtiene con suficiente aproximación la respuesta dinámica de la estructura. Los cálculos deben realizarse considerando la interacción suelo-estructura ya que la presencia de ésta modifica las deformaciones del suelo en campo libre ("free-field"). En este artículo se presentan resultados para poder estimar las deformaciones sísmicas inducidas en estructuras enterradas profundas de sección rectangular o circular.

Compresibilidad de arenas cementadas en ambiente semiárido

Scipedia content — Wed, 28 Jun 2017 11:37:39 +0200

En este artículo se describen las características físicas y los resultados de pruebas de consolidación de una arena silícea cementada con carbonato de calcio, típica de los horizontes petrocálcicos propios de los ambientes áridos y semiáridos del Suroeste de los Estados Unidos. Para preservar la estructura y cementación del suelo se tomaron bloques de la arena cementada y se labraron especímenes inalterados para realizar pruebas de consolidación. Se encontró que la matriz de la arena cementada en su estado natural tiene densidad muy baja y es muy porosa. Cuando este material tiene contenidos de agua muy bajos, similares a las condiciones secas naturales del sitio, la estructura del suelo es estable y relativamente resistente a la carga normal. Sin embargo, los resultados de las pruebas de consolidación indican que la saturación pudiese causar el colapso de la matriz arenosa cementada y el asentamiento de este suelo.

Comportamiento monotónico de suelos diatomáceos

Scipedia content — Wed, 28 Jun 2017 11:37:35 +0200

Hay varios sitios en el mundo donde se ha detectado la presencia de microfósiles (diatomeas) en los depósitos naturales de suelo (ej., la ciudad de México y la Bahía de Osaka, Japón). Estos depósitos naturales de suelos que contienen diatomeas (suelos diatomáceos) se caracterizan por tener propiedades físicas y mecánicas singulares, que no siguen las correlaciones obtenidas y aceptadas para la mayoría de los suelos. Las diatomeas son ejemplos sobresalientes de materiales naturales micro y nano-estructurados que pueden afectar las propiedades de los suelos. Sin embargo, la interacción entre las diatomeas, las partículas de arcilla y el agua requiere una investigación adicional. Mientras las diatomeas se usan en muchas aplicaciones científicas, su uso en la ingeniería geotécnica es escaso. Teniendo en cuenta sus características únicas, hay un gran potencial para utilizar diatomeas en el desarrollo de suelos diseñados para aplicaciones en ingeniería geotécnica y geo-ambiental. Este artículo presenta la investigación realizada sobre mezclas artificiales de diatomita-caolinita utilizando el equipo de corte simple, bajo condiciones no drenadas. Los resultados muestran que las características de las curvas esfuerzo-deformación son dependientes del contenido de diatomeas. Con base en los resultados de esta investigación y tomando en cuenta la presencia de diatomeas en el suelo volcánico-lacustre de la ciudad de México, se sugiere una explicación de algunas de sus propiedades.

Congresos

Scipedia content — Wed, 28 Jun 2017 11:34:44 +0200

Congresos y Seminarios

Seismic analysis of structures

Scipedia content — Wed, 28 Jun 2017 11:34:41 +0200

Revision: Seismic analysis of structures

Critérios de avaliação do conforto humano em edifícios submetidos à ação dinâmica do vento

Scipedia content — Wed, 28 Jun 2017 11:34:38 +0200

Em projetos estruturais, é procedimento usual para a análise de estruturas submetidas a ações de caráter dinâmico a consideração de simplificações, assumindo estas ações como de natureza estática. No entanto, com a adoção desse tipo de simplificação, ações capazes de proporcionar desconforto aos usuários não podem ser verificadas. Especialmente em edificações altas e esbeltas, questões relacionadas ao conforto humano podem apresentar grande relevância pelo fato das vibrações proporcionarem, em algumas situações, a falta de concentração no desempenho de atividades, enjôo, além de incertezas relativas à segurança estrutural, entre outros. O presente trabalho tem como objetivo apresentar procedimentos para a avaliação do conforto humano em edifícios altos submetidos à ação dinâmica do vento, bem como parâmetros de estabilidade global, buscando verificar a correlação destes com a percepção do ocupante. Como estes objetivos foram efetuadas simulações numéricas em diversas estruturas. Apresenta-se resultados de algumas destas simulações, bem como as conclusões obtidas.

Modelo de riesgo urbano de desastre natural por acción del viento. El caso del centro histórico urbano de Guanabacoa, Cuba

Scipedia content — Wed, 28 Jun 2017 11:34:35 +0200

Los centros urbanos tradicionales, específicamente aquellos que tienen categoría de centros históricos, están sometidos a grandes índices de riesgo urbano de desastre natural por acción del viento debido a la compleja situación que yace tras sus vulnerabilidades, y la forma en que se comprometen los valores patrimoniales que ellos contienen. Con el objetivo de realizar procesos de control sobre este tipo de riesgo se inició un estudio preeliminar en el que se diseñó un modelo matemático para un sector urbano del Centro Histórico de Guanabacoa (un caso de particular interés en el occidente de Cuba). En este escrito se presenta la concepción de dicho modelo, la experiencia de su aplicación y la valoración de esta última.

La seguridad de la ciudad de Córdoba: Análisis de la amenaza por falla de la presa san roque

Scipedia content — Wed, 28 Jun 2017 11:34:30 +0200

El nuevo Dique San Roque se ubica en el Valle de Punilla de la provincia de Córdoba en Argentina sobre el curso del río Suquía. Aguas abajo de la presa, sobre las márgenes de este río, se encuentran grandes asentamientos urbanos como la Ciudad de Calera (a 13 km) y la Ciudad de Córdoba (a 42 km), esta última capital de la provincia con más de un millón trescientos mil habitantes. Además, una gran parte de la vida de esta ciudad está localizada en las márgenes del Suquía; en particular servicios fundamentales como son: el suministro de agua potable, electricidad, policía y hospitales. En este artículo se describen estudios y resultados obtenidos que son la base para la realización del Plan de Acción Durante Emergencias de la Presa San Roque. Se plantearon posibles escenarios de rotura, se estudió de manera particular la rotura por sobrepaso y la rotura por actos de vandalismo. Se confeccionó el mapa de inundación para un caso hipotético de rotura por vandalismo utilizando los valores obtenidos de la modelación con HEC-RAS en régimen no permanente. Se realiza también un primer análisis de la vulnerabilidad de la Ciudad a este tipo de eventos. Se recomienda realizar estudios del escenario posible de rotura por sismo.

Colapso del sistema de protección de una alcantarilla ferroviaria durante tormenta de diseño

Scipedia content — Wed, 28 Jun 2017 11:34:26 +0200

Este trabajo documenta la falla de una estructura hidráulica de mediana escala, como consecuencia de la crecida del Arroyo Los Horcones. El sitio en estudio se emplaza en la Provincia de Salta al noroeste de Argentina, Km 950,20 de la Línea C - del ex Ferrocarril General Belgrano. El sistema de protección de la alcantarilla colapsó luego de una tormenta de corta duración y alta intensidad ocurrida durante el 17 de diciembre de 2009 sobre la cabecera de la cuenca. Si bien esta tormenta fue prevista en el diseño de la obra de arte, el sistema de protección falló como consecuencia de la obstrucción parcial de la sección de paso debido a la acumulación de troncos provenientes de la tala de árboles. Esta situación elevó el tirante aguas arriba de la alcantarilla, provocando la erosión detrás del sistema de protección. La pérdida de suelo lateral a la alcantarilla, generó un nuevo paso del flujo a través del terraplén ferroviario. Esto permitió la evacuación del agua acumulada y liberó la estructura de hormigón de empujes mayores a los considerados en el diseño, evitando la falla global del sistema.

El alcantarillado sanitario como modelo global de construcción de riesgo local

Scipedia content — Wed, 28 Jun 2017 11:34:22 +0200

Las prácticas de saneamiento promovidas actualmente son de dos tipos: "tout a l'égout" o alcantarillado sanitario y el almacenamiento con letrina y fosa séptica. Desde hace más de un siglo, el sistema del alcantarillado ha sido percibido como una tecnología ideal, en particular, en las zonas urbanas. El sistema se introdujo en numerosas ciudades de los países del Sur con fondos internacionales. La letrina con pozo se percibe como una solución primitiva y precaria utilizada en aglomeraciones que no tienen una red de alcantarillado. Un sistema de alcantarillado con poca agua o sin tratamiento contribuye inexorablemente a la construcción del riesgo local. Actualmente los municipios enfrentan las siguientes opciones: extender la red de alcantarillado existente, con todas las limitaciones y riesgos que esto implica, o bien, buscar alternativas nuevas y sustentables. Sin embargo, pocos municipios se lanzan hacia la última opción, muchos de ellos por falta de información. El caso de la Ciudad de México es emblemático pero no es el único caso en el mundo en donde la elección del sistema de alcantarillado está conduciendo paulatinamente a la ciudad a un desastre anunciado. La vulnerabilidad de la ciudad a inundaciones ha crecido sobre todo a partir de los años cincuenta. La prevención y mitigación de estas inundaciones conducirá a llevar a cabo más y más obras de desagüe costosas hasta un punto límite donde se tendrán que plantear otras opciones de saneamiento. En este artículo analizamos in fine algunas de las soluciones alternativas secas de eco-saneamiento sustentable que no requieren de agua para funcionar.

Permeabilidad intrínseca de suelos arenosos con presencia de partículas de limo y arcilla

Scipedia content — Wed, 28 Jun 2017 11:34:19 +0200

El flujo de fluidos dentro de los poros del suelo controla aspectos importantes relacionados con la mecánica de suelo. En particular, la permeabilidad intrínseca, junto con la pendiente del terreno es un parámetro de fundamental importancia en el análisis de vulnerabilidad a desastres naturales relacionados con los riesgos de inundación y los derrumbes. Este parámetro afecta considerablemente la relación infiltración-escorrentía en el caso de grandes precipitaciones e influye en la interacción suelo-líquido pudiendo producir colapso o ablandamiento del terreno que con frecuencia se manifiesta en daños en la infraestructura apoyada o enterrada en el mismo. Debido a ello, resulta de interés estudiar los aspectos que controlan el flujo de fluidos dentro de medios granulares gruesos con distintos contenidos de finos de diverso tamaño y forma de partícula. En este trabajo se ensayan suelos arenosos que contienen distintos porcentajes de limo, zeolita y bentonita. Para diversas mezclas se determina la permeabilidad con fluidos orgánicos no miscibles con el agua, con agua destilada y con soluciones de cloruro de calcio con diferentes concentraciones. Los resultados obtenidos permiten identificar el efecto de la interacción fluido-partícula y la influencia de la granulometría en la permeabilidad intrínseca de los suelos arenosos.

Predicción del deterioro de estructuras metálicas de navegación sometidas a cargas hidráulicas con la cadena de Markov y la simulación Latin Hypercube

Scipedia content — Wed, 28 Jun 2017 11:34:15 +0200

El deterioro de los elementos de estructuras hidráulicas metálicas en el sistema de presas y esclusas del país es causada por los efectos combinados de varios fenómenos complejos: desgaste del sistema protector, corrosión, fatiga y fractura, impacto y sobrecargas. Este artículo presenta ejemplos de deterioro en estructuras metálicas sometidas a cargas hidráulicas. También presenta un método para predecir el futuro deterioro basado en las condiciones actuales. El artículo incluye la metodología para desarrollar curvas de deterioro cuando los datos de las condiciones están disponibles.

Desastres naturales: ¿tiene la historia algo que decir?

Scipedia content — Wed, 28 Jun 2017 11:34:12 +0200

Editorial: Desastres naturales: ¿tiene la historia algo que decir?

Congresos

Scipedia content — Wed, 28 Jun 2017 11:34:09 +0200

Congresos y Seminarios

Fundamentals of seismic loading on structures

Scipedia content — Wed, 28 Jun 2017 11:34:06 +0200

Revision: Fundamentals of seismic loading on structures

Coeficientes aerodinámicos de cubiertas cónicas de tenso-estructuras aplicando dinámica de fluidos computacional

Scipedia content — Wed, 28 Jun 2017 11:34:03 +0200

Se estudió el comportamiento ante acciones de viento de una cubierta cónica típica de las tenso-estructuras, mediante Dinámica de Fluidos Computacional y considerando un perfil de velocidades medias obtenido de pruebas experimentales de túnel de viento. La estructura estudiada consiste en una cubierta de base circular y altura (H) variable. Se consideraron tres alturas desde la base hasta el anillo superior. Se observa que la presencia del anillo ocasiona un cambio dramático en los coeficientes de presión cerca del centro de la cubierta, lo que conduce que la cubierta esté sujeta a levantamiento. Los resultados sugieren que para valores grandes de H, las succiones en la cubierta disminuyen cerca del anillo superior y aumentan del lado de barlovento; presentándose los valores más altos a medida que la altura H disminuye. Los efectos aeroelásticos no se incluyen en los modelos numéricos realizados.

Efecto del ascenso del nivel freático en suelos colapsables

Scipedia content — Wed, 28 Jun 2017 11:33:59 +0200

El desarrollo de áreas urbanas, en muchos casos, provoca con el tiempo modificaciones en las condiciones hidrogeológicas locales previamente existente. En un sector del sur de la ciudad de Córdoba, dominada por suelos de tipo loéssicos altamente colapsables, se detectó a principios del año 2001 el ascenso de los niveles freáticos hasta niveles próximos a la superficie. El área afectada comprende una extensión aproximada de 1.7 km2 y una población de unos 5.600 habitantes. En la emergencia del suceso se solicitó la intervención de miembros del área de Geotecnia de la Universidad Nacional de Córdoba a los fines de realizar un estudio de los orígenes del problema y la elaboración de un proyecto de remediación. Para este estudio se realizaron distintos trabajos incluyendo: la revisión de antecedentes geológicos-geotécnicos, la evaluación de las condiciones geotécnicas, y evaluación de las condiciones hidrológicas e hidráulica superficiales. Este trabajo presenta un resumen de los estudios realizados y un resumen del proyecto de remediación inicialmente propuesto que consistió básicamente en la colocación varios de pozos de bombeo. La distribución y localización de los mismos se realizó empleando una modelación numérica del flujo. La concordancia de las mediciones de descenso del nivel de agua y las estimadas mediante el modelo resultó muy aceptable.

Atenuación y distribución de probabilidad de intensidades sísmicas para Colombia y el occidente de Venezuela

Scipedia content — Wed, 28 Jun 2017 11:33:54 +0200

Este artículo utiliza una base de datos de mapas de isosistas (artículo acompañante) para desarrollar dos aproximaciones. Primero, se generan ecuaciones de atenuación tradicionales de intensidad que relaciona variables continuas y discretas, y segunda se presenta un método alternativo de tratamiento del problema que desarrolla funciones probabilísticas conjuntas mixtas discretas-continuas que permite estimar directamente las probabilidades de ocurrencia o excedencia de diferencia de intensidades dada la distancia a un sitio y la intensidad epicentral. La distribución condicional de la distancia dado un nivel de intensidad o diferencia de intensidad es continua y se representa por una distribución lognormal. La distribución de intensidades es discreta y se representa por una función de Poisson bimodal. La representación bimodal se puede deber a reflexiones de onda en la frontera entre la litósfera y la astenósfera. Ambas aproximaciones se aplican para sismos de subducción y eventos superficiales ocurridos en Colombia y el Occidente de Venezuela.

Base de datos de intensidades sísmicas para Colombia y el occidente de Venezuela

Scipedia content — Wed, 28 Jun 2017 11:33:50 +0200

Este artículo presenta una base de datos de intensidades sísmicas recopiladas para Colombia y el Occidente de Venezuela. Esta base de datos macrosísmica está basada en la recopilación y análisis de información contenida en mapas de isosistas generada por diferentes investigadores en el Norte de Suramérica. La base de datos incluye 68 eventos sísmicos ocurridos entre 1766 y 2004. Para estos eventos, se presentan 283 pares de datos de intensidad - radio equivalente. El presente trabajo constituye la base para futuras investigaciones cuyo objetivo sea mejorar el entendimiento de la atenuación de la energía sísmica en la región.

Estimación de la rigidez lateral elástica de muros con aberturas

Scipedia content — Wed, 28 Jun 2017 11:33:47 +0200

Se comparan las aproximaciones obtenidas con distintos métodos simplificados propuestos en la literatura para estimar la rigidez lateral de muros con aberturas de cualquier material que se modele como elástico lineal, con los resultados obtenidos con el método del elemento finito para modelaciones hechas con mallados razonablemente finos. Se estudiaron muros de un nivel y de varios niveles, con distribuciones simétricas y asimétricas de aberturas con respecto a un eje vertical. De los resultados obtenidos se observa que cuando existen asimetrías en la distribución de una sola franja de aberturas en elevación, las mejores aproximaciones se obtienen con el método del marco equivalente más usado en México, el de Coull y Choudhury y el método de la columna ancha equivalente de sección variable propuesto por los autores, sobre todo a medida que aumenta la esbeltez de los muros.

Transformada de Hilbert, descomposición modal empírica y sus aplicaciones en el análisis de vibraciones libres

Scipedia content — Wed, 28 Jun 2017 11:33:42 +0200

Este artículo presenta una introducción a la transformada de Hilbert y la descomposición modal empírica. Se enfatiza en la implementación de estas técnicas en el análisis de vibraciones libres, específicamente en la determinación de frecuencias naturales y amortiguamiento. Se exploran los retos que presenta su aplicación práctica, como la presencia de ruido en la señal original y los efectos de borde. Se concluye que estas técnicas muestran un gran potencial en aplicaciones que involucren el análisis de vibraciones tal como sistemas de monitoreo de salud estructural. Sin embargo varios inconvenientes todavía necesitan ser resueltos y futuras investigaciones en este tema son exhortadas.

Investigación de causas de explosiones en una planta de almacenamiento de combustible en Puerto Rico

Scipedia content — Wed, 28 Jun 2017 11:33:39 +0200

Se presenta el accidente ocurrido en las instalaciones de una compañía petrolera ubicada en Bayamón, Puerto Rico en 2009, con el objetivo de reconstruir detalladamente el desarrollo del accidente, identificar las causas que lo provocaron y resaltar lecciones aprendidas sobre el incendio más grande registrado en la historia de la isla. Se describe el depósito de Caribbean Petroleum Corporation y sus niveles de contención, y se identifican los hechos relacionados al accidente ocurrido en octubre 2009 y sus consecuencias. Las explosiones e incendios desencadenados en esta catástrofe, además de destruir más de la mitad de los tanques de almacenamiento de combustible activos en la planta y causar daños importantes al ambiente y a los habitantes de la zona de desastre, generaron una pérdida económica de gran magnitud.

El peso de la responsabilidad: Sobre la "micro-ética" y la "macro-ética" en la enseñanza de ética en la ingeniería

Scipedia content — Wed, 28 Jun 2017 11:33:35 +0200

Editorial: El peso de la responsabilidad: Sobre la "micro-ética" y la "macro-ética" en la enseñanza de ética en la ingeniería

Métodos Runge-Kutta implícitos de alto orden para flujos incompresibles

Scipedia content — Fri, 26 May 2017 09:48:34 +0200

The spatial discretization of the unsteady incompressible Navier-Stokes equations is stated as system of Differential Algebraic Equations (DAEs), corresponding to the conservation of momentum equation plus the constraint due to the incompressibility condition. Asymptotic stability of Runge-Kutta methods applied to the solution of the resulting index-2DAE system in analyzed, allowing a critical comparison of semi-implicit and fully implicit Runge-Kutta methods, in terms of order of convergence and stability. Numerical examples, considering a Discontinuous Galerkin formulation with piecewise solenoidal approximation, demonstrate the applicability of the approach, and compare its performance with classical methods for incompressible flows.

Previsão do risco de escorregamentos de taludes a partir de um modelo fuzzy

Scipedia content — Fri, 26 May 2017 09:48:30 +0200

The stability of slopes is a topic of great interest to the geotechnical engineer, given the significant economic losses, and even human, resulting from the slopes collapse . Its estimated that the landslides outbreak has already caused thousands of deaths and tens of billions of dollars in annual losses worldwide. The phenomena of instability of slopes are conditioned by many factors, such as climate, the lithology and structures of rock, the morphology, the anthropic and others. The anlaysis of geological and geotechnical conditions of landslides provides and appraisal of each of the factors involved in the processes of instability of slopes, allowing the achievement of results of interest with regard to the mode of acton of fators. The current work aims at the use of Fuzzy Logic to create a model that, in qualitative form, provide an estimate of the risk of landslides on the slope of residual soil. To the development of the mdodel was examined and extensive database of landslides in Rio de Janeiro, provided by the GeoRio Foundation. Among the main findings includes the capability of fuzzy logic predicting risk of landslides on the slope of residual soil, appearing as a tool capable of assisting in the detection of areas of risk.

Modelo de sucesos infrecuentes en túneles de carretera

Scipedia content — Fri, 26 May 2017 09:48:24 +0200

Infrequent Events in road tunnels (fire, accidents, etc.) lead to high risk situations that can endanger many lives and cause great materials damage. These events are so varied and often unpredictable that it is difficult to make correct decisions due to the lack of initial information and the rapid change in the event progress. The development of a Decision Support System (DSS) in road tunnels will permit a suitable emergency management and it will ensure the minimization of personal damages in these kind of events. The system will be formed by three fundamental elements: the Infrequent Events Model. The Evacuation Model has been developed based on the Black-Box Model, Boolean algebra and Probability Theory defining the inputs, the outputs and the main parameters. The mathematical equations which relate inputs, outputs and main parameters have been obtained. The development of the computational model and the auxiliary programs has permitted to verify and validate the model.

Soluçoes analíticas das condiçoes de optimalidade do dimendionamento de secçoes rectangulares de betao armado

Scipedia content — Fri, 26 May 2017 09:48:21 +0200

Formula-se o problema de custo mínimo de secçoes rectangulares de betao armado à flexao segundo o Eurocode 2 nas variáveis de dimensionamento altura de secçao e área das armaduras. As condiçoes de optimalidade de Khun-Tucker sao resolvidas simbolicamente, obtendo-se 6 soluçoes de armadura simples com rotura pelo betao,pelo aço e simultanea, e uma soluçao de armadura dupla com rotura pelo betao. Identificamse as regioes de optimalidade, que se mostra serem adjacentes, de cada uma das soluçoes no plano Cartesianodos parametros

Evaluación holística del riesgo sísmico en zonas urbanas

Scipedia content — Fri, 26 May 2017 09:48:16 +0200

Risk has been defined, for management purposes, as the potential economic, social and environmental consequences of hazardous events that may occur in a specified period of time. In the past, the concept of risk has been defined in many cases in a fragmentary way, according to each scientific discipline involved in its appraisal. A framework and a multidisciplinary risk evaluation model is proposed in this article that take into account not only the expected physical damage, the number and type of casualties or the economic losses, but also the conditions related to soial fragility and lack of resilience which favor second order effects (or indirect effects) when an earthquake strikes an urban centre. Thus, the mentioned evaluation is holistic, that is based on an integrated and comprehensive approach, made by using indicatos andoriented towards guiding decision-making. Th conceptual framework and the model proposed are also valid for their applicationto multihazard risk evaluation, although this article has been focused on the evaluation of the seismic riskk. The first step in obtaining the Urban Seismic Risk index (USRi) consists of calculating a Physical Risk index for each unit of analysis starting form existing physical risk scenarios. An impact factor, associated with a set of socio-economic and lack of resilience conditions of the community, is applied in a second step to the physical risk index in order to obtain the USRi. It has been demostrated that the proponed holistic evaluationmodel of the seismic risk in robust, provideing stable and reliable values of the USRi. Finally, numerical simulation results of the seismic risk obtained with the proposed model are given in the article for the cities of Bogota (Colombia), Barcelona (Spain) and Manila (The Phillipines).

Una metodología para la simulación de mezclas asfálticas recicladas

Scipedia content — Fri, 26 May 2017 09:48:08 +0200

In this article a new methodology is presented for the mechanical characterization of the asphalt mixes, specially the recycled asphalt mixes, which leads to define the adequate laboratory tests and to formulate a new constitutive model able to integrate the mechanical properties and reproduce the response of the material in a more complex context. The addition of asphaltic recycled material over a conventional mix, change in a significant way the properties of this mix. The design of recycled asphalt mixes requires additional information far away the properties of this mix. The design of recycled asphalt mixes requires additional information far away from the usual test used in the design of conventional mixes, to pick up the evolution of the tenacity of the cracking resistance, determinant variables in the recycled asphalt mixs behavior. For thid purpose, the direct tensile test in proposed as the experimental reference for the characterization of the material. A new constitutive model in formulated considering in a explicit shape, the influence of the strain shape, the influence of the strain rate of the material in the simulation of its response. The direct tensile test is used to calibrate the parameters of the model, and so characterize its structural response. The main objective of this development is the simulation of the behavior of the recycled asphalt mixture in a fleexible pavement. The results obtained reach a good approximation to the experimental measures with the proposed model.

PUMI: Un código explícito no estructurado para resolver las ecuaciones de Euler

Scipedia content — Fri, 26 May 2017 09:48:00 +0200

The PUMI flow solver has been developed at CIMNE in order to address the need for fast solutions of the flow field around complex geometries. Nowadays calculations involving a number of cells on the order of tens of millions are performed routinely. PUMI was created to deal with this kind of large-scale problem using modest hardware, therefore special emphasis was placed on the computational efficiency of the code. Design guidelines where minimum memory requirement, very fast single-threaded performance as well as satisfactory parallel scaling up to a moderate number of threads (as found on current entry-level SMP workstations). In order to simplify the mesh generation activities an unstructured finite element formulation was selected. This paper describes the theoretical basis of the algorithm as well as details of the implementation that increase the robustness and efficiency of the code.

Simulação do comportamento não linear de materiais quase-frágeis via elementos finitos com fissura embebida

Scipedia content — Fri, 26 May 2017 09:47:54 +0200

A combined constitutive model based on the Continuum Damage Mechanics is presented to represent the nonlinear behavior of quasi-brittle materials, which present different response when subjected to tension or compression. The constitutive model is a composition of two simple and specific models designed to treat each type of behavior. The combined model is able to deal with alternating load (tensioncompression), involving formation, closure and reopening of cracks. To model the compressive behavior, a degradation criterion based on the second invariant of the deviatoric part of the effective stress tensor (Von Mises or J2 criterion) is used. To simulate cracking, a damage model with degradation criterion based on the strain energy associated to the positive part the effective stress tensor is adopted. The combination of the models is made on the basis of the effective stresses. The model is able to represent the formation of discontinuities in the displacement field (strong discontinuities) for quasi-brittle materials. The region of strain localization (fracture process zone) is described by a softening law which establishes dissipation energy compatible with the fracture energy. The continuous region is described by the J2 damage model, with parameters adjusted to describe the compressive nonlinear behavior in compression. Some basic tests are performed to assess the ability of the model to represent the main aspects of the behavior of quasi-brittle materials. The ability of the model to predict the ductile behavior of reinforced concrete beams is also studied by comparing the numerical results with experimental ones.

Modelo de fuerzas interatómicas para el grafeno a partir del potencial AIREBO

Scipedia content — Fri, 26 May 2017 09:47:50 +0200

In view of the influence that topological defects have on the thermal and electrical properties of graphene, and given the pivotal role that such properties play in potential applications of graphene as a building block for nano-electronic components, models of graphene behavior that allow for the consideration of such defects are of the essence. In the present work, we have obtained an atomic force-constant model from the AIREBO potential (Adaptive Intermolecular Reactive Empirical Bond-Order), of Stuart et al. [1], that accounts for interatomic interactions up to fourth neighbors. We present explicit expressions of the potential derivatives as well as the force-constant values. We have verified that the force-constant model is invariant under the crystal symmetries and that the phonondispersion curves of the corresponding dynamic model are in good agreement with those obtained by other authors. In addition, we have verified that the thirdand fourth-neighbor interactions affect neither the displacement field in the vicinity of dislocation cores nor the corresponding formation energies predicted by the theory of discrete dislocations of Ariza and Ortiz [2].

Diseño y análisis térmico bajo incertidumbre en estructuras aeronáuticas

Scipedia content — Fri, 26 May 2017 09:47:45 +0200

In this work an uncertainty quantification procedure and a robust design method are applied to the thermal design of a skin panel and a wing box section. The uncertainty quantification method selected is based on Monte Carlo simulations and a set of common design parameters have been considered and formulated with random values. Numerical results show that the most significant randomness comes from thermal loads and also that the amount of uncertainty decreases from input to output. On the other hand, the Taguchis method of robust design has been applied to obtain the most appropriate values of a set of control factors in several design situations. In this case, the results show and improvement in the response of the components, maintaining a low dependence on input value variations and producing designs that increase the quality level.

Improving a strongly coupled method for FSI by a simple approximation of the pressure tangent matrix

Scipedia content — Wed, 19 Apr 2017 12:13:47 +0200

La interacción de los fluidos con las estructuras de su entorno es un desafío clásico para las técnicas numéricas. El objetivo de este trabajo es doble: en primer lugar se proporciona una explicación teórica simple de los principales problemas que se deben superar cuando se trata con un fluido incompresible. A continuación se introduce y justifica un nuevo procedimiento para la solución de problemas complejos de interacción fluido-estructura. Dicha estrategia se basa en la introducción de un «laplaciano de interfase» en el contorno común entre ambos medios. La idea es considerar la dependencia entre la presión del fluido y la velocidad de la estructura como un problema no lineal, que se va a resolver mediante un esquema cuasi-Newton. Se demuestra que el término de interfase resultante es una aproximación de la matriz tangente de dicho problema no lineal, usando exclusivamente álgebra lineal discreta. Finalmente, se verifica la validez de la técnica propuesta mediante su aplicación a algunos ejemplos.

Discrete modeling of human body using preprocessing and segmentation techniques of medical images

Scipedia content — Wed, 19 Apr 2017 12:12:47 +0200

The generation of anatomical models is one the most important concern to biomedical researchers as well as to medical doctors, due to needed to understand the human tissues. Is know that the soft tissues like heart, brain, prostate and hard tissues like jaw, bones, skull, etc are structures of complex morphologies, so, the anatomical models generation is not an easy and trivial task. Currently, this task has benefited of advances of imaging diagnostic, which permit obtain cross and longitudinal sections of human body. In this research, we describe a method to obtain 3D discrete models of human body given by a dataset of medical images. Five main modules were implemented in prototype software: (1) Reading and 3D reconstruction of Computerized Axial Tomography and Magnetic Resonance Images. (2) Preprocessing techniques for improve the low medical images quality by using enhancement algorithms to reduce image noise and to increase structures contrast. (3) Combined segmentation techniques for tissue identification, which were applied through a multi-stage approach. (4) Post processing techniques to improve segmented volumes and (5) Exportation task of volumes to readable formats by Computer Aided Design (CAD) tools to be later analyzed by numerical methods. The performance of our method is shown on several medical examples and the techniques were validated using statistical descriptors to compare our models with models from free databases. Results showed that the implemented techniques generate precise and useful models for numerical analysis and medical survey, planning and surgery in a short processing time.

Stability and dispersion of the problem of seismic wave propagation in 2-D using the generalized finite difference method

Scipedia content — Fri, 31 Mar 2017 13:10:26 +0200

This paper shows the solution to the problem of seismic wave propagation in 2-D using generalized finite difference (GFD) explicit schemes. Regular and irregular meshes can be used with this method. As we are using an explicit method, it is necessary to obtain the stability condition by using the von Neumann analysis. We also obtained the star dispersion formulas for the phase velocities for the P and S waves, as well as the ones for the group velocities. As the control over the irregularity in the mesh is very important in the application of this method, we have defined an index of irregularity for the star (IIS) and another for the cloud (IIC), analyzing its relationship with the dispersion and time step used in the calculations.

An algorithm for the design of a feedforward controller in canals

Scipedia content — Fri, 31 Mar 2017 12:59:52 +0200

When it is carried out any movement of a gate or another mechanism of control of a canal in free surface flow, an answer of the flow can take a lot of time in being noticed in the place of the canal takes place in which it was generated the necessity to increase or to reduce the irrigation demand, for example. Usually, the scheduled perturbations of the flow can be programmed for a future horizon. In this manner, the control action can also be programmed. This work, it shows a feedforward control algorithm that plans the gate trajectories when the demand at offtakes are programmed in a prediction horizon. The Hydraulic Influence Matrix (HIM) or matrix of sensibility of the hydrodynamic conditions in the canals to changes in the parameters of the gate trajectories is a tool that is shown very effective in the control of canals in open loop. The work defines the concept, it presents the form of to calculate and to compile the HIM starting from the complete equations of Saint-Venant in their characteristic form. Later on, it shows up an algorithm in that HIM is used: a feedforward controller algorithm so-called GoRoSo. Known the water demands at offtakes, the algorithm calculates the optimal gate trajectories in advance for a prediction horizon with the objective of keeping constant the water depth at gravity offtakes.

The concept hyperbeam as generalization of 1-dimensional models in rod elastostatics

Scipedia content — Fri, 31 Mar 2017 12:56:10 +0200

This paper is concerned with the general formulation of linear problems in rod elastostatics, and with the identification of their common formal and structural features, valid for every kinematical hypothesis. The generalized variables (section forces and generalized deformations) defining the 1-dimensional model are introduced in a consistent and natural way, through a convenient factorization of the density of complementary potential energy, for every kinematical constraint which can be expressed as a linear combination of the generalized displacements. The identification of this complementary energy function with the Hamiltonian functional of analytical mechanics allows a systematic procedure to construct the equations which rule this class of problems. In this frame, the main target is to establish the required conditions to write the rod equilibrium equations in a purely statical form (with no interplay of kinematical variables). We primarily conclude that this is possible when the kinematics of the cross-sections is constrained to a rigid body movement. As a consequence, the concept of hyperbeam is proposed in order to define those models with deformation modes beyond rigid body movements of the cross section: in them, section forces and generalized displacements are coupled in the equilibrium equations. This is related to the idea of local static indeterminacy (hyperstaticity ) and justifies the new name.

Simulation of delamination in composite materials using the serial/parallel mixing theory

Scipedia content — Fri, 31 Mar 2017 12:54:52 +0200

Este artículo presenta un nuevo procedimiento con el que simular el fallo por delaminación en materiales compuestos. El método propuesto utiliza la teoría de mezclas serie/paralelo, desarrollada por Fernando Rastellini, para la caracterización constitutiva del material compuesto. Esta formulación obtiene el comportamiento del compuesto acoplando la respuesta constitutiva de los materiales componentes, fibra y matriz, imponiendo una relación de iso-deformación en la dirección de la fibra (dirección en paralelo) y una relación de iso-tensión en el resto de direcciones (direcciones en serie). Si bien la teoría de mezclas serie/paralelo permite simular los materiales componentes con cualquier ecuación constitutiva, el presente trabajo utiliza una formulación de daño para caracterizar la matriz y una formulación elástica para la fibra. Se mostrará que es posible, utilizando la teoría de mezclas serie/paralelo y una formulación de daño, simular el fallo del compuesto por delaminación. Además, éste se obtiene de forma natural, sin necesidad de definir elementos especiales en los que propagar la fractura, ni ser necesario utilizar costosas técnicas numéricas como el remallado o elementos de contacto. Con el procedimiento propuesto el fallo constitutivo de la matriz conduce a una reducción de la capacidad portante del compuesto en las direcciones en serie (entre otras, la dirección de las tensiones tangenciales) sin eliminar la capacidad resistente en la dirección de la fibra. Se probará que un material compuesto con este comportamiento corresponde a un material delaminado. La última sección de este artículo muestra la simulación del End Notch Failure Test y los resultados obtenidos son comparados con resultados experimentales. La similitud de los resultados numéricos y experimentales demuestra la validez del método propuesto para resolver problemas de delaminación en materiales compuestos.

Prediction of crack propagation via local constitutive models with a scheme to track the discontinuity path

Scipedia content — Fri, 31 Mar 2017 12:54:28 +0200

Estudam-se os aspectos referentes à qualidade e objetividade das respostas obtidas com as diferentes formulações (simétrica e não-simétrica) de elementos incorporados com descontinuidade forte regularizada, assim como com a abordagem contínua (distribuída), combinando-se a lei de abrandamento dependente do tamanho do elemento com um esquema de construção progressiva da trajetória de descontinuidade. O estudo é realizado com base nos conceitos de consistência cinemática e estática das formulações de elementos com descontinuidade incorporada.

Corrección en el artículo de R.G. Espinosa et al. « Optimización de código para un simulador de estructuras aporticadas y su implementación como herramienta productiva »

Scipedia content — Tue, 28 Feb 2017 15:24:57 +0100

Global best local search applied to the economic design of reinforced concrete vaults

Scipedia content — Tue, 28 Feb 2017 15:20:36 +0100

This paper presents two gradient algorithms applied to the economic optimization of reinforced concrete vaults, typically used in the construction of underpasses. The algorithms are gradient multi start neighbourhood exhaustive search procedures. The vault is defined by 45 design variables and the objective function is an economic one. Both methods have been applied to a vault of 12.40 m of diameter and 3.00 m of lateral walls. Design variables have been coded in base 2 for algorithms GB1 and in Gray coding for GB2. The neighbourhood is defined by the set of solutions that differ in one bit. The Gray coding solves the lack of proximity between two solutions typical of the ordinary binary coding. The positive effect of the Gray coding is proven in the present paper, where the average cost of 3, 000 runs of GB2 improves by 3.81% a similar run by algorithm GB1. In addition, GB2 attains the best cost solution. The paper includes a stop criterion for the algorithm based on the stability of the statistics of the multi start results. The algorithms are simple and can be applied to other structural problems. The structure of best cost has a high slenderness and a span to depth ratio of 40. The study reports savings of 6% when compared to a design by an experienced practitioner office.

Corrección en el artículo de B. Vera et al. « Un portal de cálculo para la evaluación de la vulnerabilidad sísmica de estructuras aporticadas mediante elementos finitos »

Scipedia content — Tue, 28 Feb 2017 15:17:41 +0100

Evaluation of the habitability of buildings affected by an earthquake using the fuzzy sets theory and the artificial neural networks

Scipedia content — Tue, 28 Feb 2017 15:17:25 +0100

The fuzzy sets theory and the artificial neural networks are computational intelligence tools which are nowadays widely used in earthquake engineering. This paper develops a method and a computer program which use these computational intelligence tools in order to support the damage and safety evaluation of buildings after strong earthquakes. The model uses an artificial neural network with three layers and a Kohonen learning algorithm, it also uses fuzzy sets in order to manage subjective information such as linguistic qualification of the damage levels in buildings and a fuzzy rule base to support the decision making process. All these techniques are incorporated in the developed computer program. The input data is the subjective and incomplete information about the building state obtained by possibly non experienced evaluators in the field of the seismic performance of buildings. The proposed method is implemented in a tool especially useful in the emergency response phase, when it supports the decision making regarding the building habitability and reparability. In order to show its effectiveness, two examples are included for two different types of buildings.

Probabilistic pounding-induced damage assessment using PEERs methodology. Application to a seismically isolated overpass.

Scipedia content — Tue, 28 Feb 2017 15:15:45 +0100

Bridges with deck supported either on sliding or elastomeric bearings are common in mid-seismicity regions. Pounding between deck and abutments is linked with their main seismic vulnerabilities, which can be assessed by estimating the probability of a given state of damage being reached in a given time period. This paper presents a state of the art methodology used to solve that problem, as well as its application to the assessment of the vulnerability of an overpass placed in Granada area (South-east of Spain), belonging to the previously mentioned typology. The Pacific Earthquake Engineering Research Center methodology will be adapted and applied. Their main steps will be briefly presented, although the identification and characterization of damage likely to occur will be described in more detail. The model of the structure, and specially pounding modeling, will also be detailed. Results are interesting since this bridge can be considered as a representative of a widespread class. The adapted methodology may be applied to similar structures. Also, probability values obtained may serve as benchmarks.

A parametric study of piers for motorway bridge viaducts

Scipedia content — Tue, 28 Feb 2017 14:06:39 +0100

The present paper deals with the economic optimization of a series of 15 bridge piers with rectangular hollow sections. It combines height columns of 20, 30, 40, 50 and 60 m and viaducts of 40, 50 and 60 m of main intermediate spans. The optimization uses a variant of the ant colony method. Results show the variation in geometry, concrete quality, reinforcement and cost, both in the footings and in the main column, as the columns gain height and the viaducts grow in span length.

A Solid finite element with an improvement in the transverse shear behavior for shell analysis

Scipedia content — Tue, 28 Feb 2017 11:47:42 +0100

In this work a solid finite element based on a Total Lagrangian Formulation using logarithmic strains is combined with a classical assumed strain approach of the transverse strains for thick shells. The target is to use the element for shell simulations without shear locking. The selective mass scaling technique used to avoid that the discretization across the thickness reduce the critical time in codes with explicit integration of the momentum equations is summarized. Several examples are presented showing that the element is shear-locking free, the consequences of the selective mass scaling and the possibilities of the element for the analysis of composites laminates in non-linear material regime.

Explicit dynamic analysis of thin membrane structures

María Jesús Samper — Wed, 02 Nov 2016 13:31:10 +0100

An explicit dynamic structural solver developed at CIMNE for the analysis of parachutes is presented. The canopy fabric has a negligible out-of-plane stiffness, therefore its numerical study presents important challenges. Both the large changes in geometry and the statically indeterminate character of the system are problematic from the numerical point of view. This report covers the reasons behind the particular choice of solution scheme as well as a detailed description of the underlying algorithm. Both the theoretical foundations of the method and details of implementation aiming at improving computational efficiency are given. Benchmark cases to assess the accuracy of the solution as well as examples of practical application showing the performance of the code are finally presented.

Development of a 6-DoF simulator for analysis and evaluation of autonomous parafoil systems

María Jesús Samper — Wed, 02 Nov 2016 13:21:39 +0100

The role parachutes have in many civil, humanitarian and military applications call for new and improved computational tools aimed at tackling the current lack of software applications in the field. The present project, which is part of a research line being developed at CIMNE for these purposes, involves the development of numerical tools for the analysis and evaluation of autonomous parafoil systems. These tools, which are based on a 6-DOF dynamic parachute model and a GNC system implemented by means of PID algorithms, facilitate the user to test designs, develop and evaluate control strategies and analyze real-life drop scenarios. As an example of potential use, lateral and altitude control strategies were successfully developed and tested. Future implementations will include Monte Carlo simulations for statistical analysis of landing precision, parameter identification for flight-tests data reduction and an advanced GUI.

The dynamic simulator presented in this work, together with the aerodynamic and structural tools developed by CIMNE, allow simulating the complete parachute-payload system, letting the designer to analyse design variations before building prototypes, the control system engineer to test different control strategies and the flight test engineer to predict the real performance of the system even before flying it once. In brief, involving simulation in the whole development process increases chances of success, shortening development time and costs.

The Cycle of Ideas in research, development and technology transfer

María Jesús Samper — Wed, 02 Nov 2016 13:13:02 +0100

When people talks about research, development and technology transfer (RTD in short) and commercial industrial activities, it is quite usual to mix up objectives, resources and responsibilities. There is a growing opinion, spread by some public administrators and the media, that research groups at universities and RTD centers must be "profitable". In few words, many persons would wish that research is funded with competitive funds or even loans (either public or private) and that the outcomes of the research get into the market rapidly, so that the profits from marketing the corresponding products will allow research groups to be financially self-sustaining.

Advances on Finite Element Methods and Particle-based Methods for Metal Forming Processes

María Jesús Samper — Wed, 02 Nov 2016 13:08:14 +0100

The paper presents an overview of the advances in recent years on the finite element method (FEM) and on particle-based methods for the simulation of industrial metal forming processes. More specifically, we present the evolution of the FEM in the field from the early plastic/viscoplastic flow approaches to the new stabilized FEM for analysis of multiphysics bulk forming processes. Also the paper describes the state of the art in the new rotation-free shell elements for simulation of sheet stamping processes. Finally, we present the so-called Particle Finite Element Method (PFEM), as a component of a family of new computational techniques integrating particle-based methods and mesh-based procedures. The PFEM is particularly suited for large deformation problems in solids and fluids involving nonlinear mechanical and geometrical effects, fluid-structure interactions and frictional contact situations. Applications of the FEM and the PFEM to several metal and material forming processes are presented.

Análisis de flujos en lámina libre y su interacción con sólidos y estructuras por el método de partículas y elementos finitos (PFEM)

María Jesús Samper — Wed, 02 Nov 2016 12:59:46 +0100

Se describen los conceptos básicos del método de partículas y elementos finitos (PFEM) para análisis de flujos de fluidos en lámina libre y su interacción con objetos sólidos y estructuras flotantes o sumergidas. Se presentan diversas aplicaciones del PFEM en los ámbitos de la ingeniería de puertos e hidráulica y al estudio de la caída de una avalancha sobre un embalse.

Modelització del deflectòmetre d’impacte amb el mètode dels elements finits i les partícules

María Jesús Samper — Wed, 02 Nov 2016 12:55:53 +0100

El deflectòmetre d’impacte segurament és l’aparell més utilitzat per realitzar assaigs no destructius dels ferms. Els enginyers utilitzen el deflectòmetre d’impacte per estimar els mòduls elàstics de les diferents capes que conformen el ferm assumint una aproximació quasi estàtica del fenomen. Amb la utilització del Mètode dels Elements Finits i les Partícules (PFEM), per una banda es pot simular l’impacte que provoca el deflectòmetre d’impacte sobre el ferm, i de l’altra validar el PFEM com a model axisimètric de resposta dinàmica d’un ferm.

La validació consisteix a comparar la concavitat de deflexions mesurada pel deflectòmetre d’impacte amb la concavitat de deflexions calculada amb el PFEM utilitzant els mòduls elàstics que proporciona el càlcul invers.

Els capítols 2 i 3 inclouen el marc teòric en el qual es desenvolupa el treball. El capítol 2 inclou una introducció als ferms, presenta el concepte de deflexió, fa un repàs dels equips d’avaluació no destructiva i presenta un resum dels diferents mètodes existents per al càlcul de paviments flexibles. El capítol 3 és una introducció al Mètode dels Elements Finits i les Partícules.

El capítol 4 presenta els desenvolupaments dels objectius plantejats.

Per últim, es presenten unes consideracions finals, que inclouen les conclusions, possibles millores del programa d’ordinador emprat i propostes de futures línies d’investigació.

Els annexes inclouen els resultats de tots els casos calculats amb les taules i les gràfiques corresponents.

An adaptive finite point method for aeroelastic analysis

María Jesús Samper — Wed, 02 Nov 2016 12:50:22 +0100

An adaptive Finite Point Method (FPM) for solving aeroelastic compressible flow problems is presented. The numerical methodology is based on a meshless upwind-biased discretization of the Euler equations, written in arbitrary Lagrangian-Eulerian (ALE) form, and integrated in time by means of a dual-time steeping technique. This procedure allows achieving accurate solutions circumventing stability constraints of time marching schemes but profiting from its explicit features. In order to exploit the meshless potential of the method, the domain deformation approach implemented is based on the spring network analogy and ''h''-adaptivity is also employed in the computations. Several numerical examples involving typical aeroelastic problems illustrate the performance of the proposed technique. Moreover, evidence about the computational cost and parallel performance of the method is given.