Documents published in 2019 : Scipedia

Real-time micro-modelling of city evacuations
E. Haug, R. Löhner, C. Zinggerling, E. Oñate

Comp. Part. Mech (2018). Vol. 5 (1), pp. 71-86

Abstract
A methodology to integrate geographical information system (GIS) data with large-scale pedestrian simulations has been developed. Advances in automatic data acquisition and archiving from GIS databases, automatic input for pedestrian simulations, as well as scalable pedestrian simulation tools have made it possible to simulate pedestrians at the individual level for complete cities in real time. An example that simulates the evacuation of the city of Barcelona demonstrates that this is now possible. This is the first step towards a fully integrated crowd prediction and management tool that takes into account not only data gathered in real time from cameras, cell phones or other sensors, but also merges these with advanced simulation tools to predict the future state of the crowd.
Abstract
A methodology to integrate geographical information system (GIS) data with large-scale pedestrian simulations has been developed. Advances in automatic data acquisition and [...]
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Virtual modeling of polycrystalline structures of materials using particle packing algorithms and Laguerre cells
C. Recarey Morfa, M. Farias, I. Pérez, E. Oñate

Comp. Part. Mech (2018). Vol. 5 (2), pp. 213-226

Abstract
The influence of the microstructural heterogeneities is an important topic in the study of materials. In the context of computational mechanics, it is therefore necessary to generate virtual materials that are statistically equivalent to the microstructure under study, and to connect that geometrical description to the different numerical methods. Herein, the authors present a procedure to model continuous solid polycrystalline materials, such as rocks and metals, preserving their representative statistical grain size distribution. The first phase of the procedure consists of segmenting an image of the material into adjacent polyhedral grains representing the individual crystals. This segmentation allows estimating the grain size distribution, which is used as the input for an advancing front sphere packing algorithm. Finally, Laguerre diagrams are calculated from the obtained sphere packings. The centers of the spheres give the centers of the Laguerre cells, and their radii determine the cells’ weights. The cell sizes in the obtained Laguerre diagrams have a distribution similar to that of the grains obtained from the image segmentation. That is why those diagrams are a convenient model of the original crystalline structure. The above-outlined procedure has been used to model real polycrystalline metallic materials. The main difference with previously existing methods lies in the use of a better particle packing algorithm.
Abstract
The influence of the microstructural heterogeneities is an important topic in the study of materials. In the context of computational mechanics, it is therefore necessary [...]
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Systemic characterization and evaluation of particle packings as initial sets for discrete element simulations
C. Recarey Morfa, L. Cortés, M. Farias, I. Pérez, R. Valera, E. Oñate

Comp. Part. Mech (2018). Vol. 5 (3), pp. 319-334

Abstract
A methodology that comprises several characterization properties for particle packings is proposed in this paper. The methodology takes into account factors such as dimension and shape of particles, space occupation, homogeneity, connectivity and isotropy, among others. This classification and integration of several properties allows to carry out a characterization process to systemically evaluate the particle packings in order to guarantee the quality of the initial meshes in discrete element simulations, in both the micro- and the macroscales. Several new properties were created, and improvements in existing ones are presented. Properties from other disciplines were adapted to be used in the evaluation of particle systems. The methodology allows to easily characterize media at the level of the microscale (continuous geometries—steels, rocks microstructures, etc., and discrete geometries) and the macroscale. A global, systemic and integral system for characterizing and evaluating particle sets, based on fuzzy logic, is presented. Such system allows researchers to have a unique evaluation criterion based on the aim of their research. Examples of applications are shown.
Abstract
A methodology that comprises several characterization properties for particle packings is proposed in this paper. The methodology takes into account factors such as dimension [...]
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Air demand estimation in bottom outlets with the particle finite element method
F. Salazar, J. San-Mauro, M. Celigueta, E. Oñate

Comp. Part. Mech (2017). Vol. 4 (3), pp. 345-356

Abstract
Dam bottom outlets play a vital role in dam operation and safety, as they allow controlling the water surface elevation below the spillway level. For partial openings, water flows under the gate lip at high velocity and drags the air downstream of the gate, which may cause damages due to cavitation and vibration. The convenience of installing air vents in dam bottom outlets is well known by practitioners. The design of this element depends basically on the maximum air flow through the air vent, which in turn is a function of the specific geometry and the boundary conditions. The intrinsic features of this phenomenon makes it hard to analyse either on site or in full scaled experimental facilities. As a consequence, empirical formulas are frequently employed, which offer a conservative estimate of the maximum air flow. In this work, the particle finite element method was used to model the air–water interaction in Susqueda Dam bottom outlet, with different gate openings. Specific enhancements of the formulation were developed to consider air–water interaction. The results were analysed as compared to the conventional design criteria and to information gathered on site during the gate operation tests. This analysis suggests that numerical modelling with the PFEM can be helpful for the design of this kind of hydraulic works.
Abstract
Dam bottom outlets play a vital role in dam operation and safety, as they allow controlling the water surface elevation below the spillway level. For partial openings, water [...]
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General advancing front packing algorithm for the discrete element method
C. Recarey Morfa, I. Pérez, M. Farías, E. Oñate, R. Valera, H. Casañas

Comp. Part. Mech (2018). Vol. 5, pp 13–33

Abstract
A generic formulation of a new method for packing particles is presented. It is based on a constructive advancing front method, and uses Monte Carlo techniques for the generation of particle dimensions. The method can be used to obtain virtual dense packings of particles with several geometrical shapes. It employs continuous, discrete, and empirical statistical distributions in order to generate the dimensions of particles. The packing algorithm is very flexible and allows alternatives for: 1—the direction of the advancing front (inwards or outwards), 2—the selection of the local advancing front, 3—the method for placing a mobile particle in contact with others, and 4—the overlap checks. The algorithm also allows obtaining highly porous media when it is slightly modified. The use of the algorithm to generate real particle packings from grain size distribution curves, in order to carry out engineering applications, is illustrated. Finally, basic applications of the algorithm, which prove its effectiveness in the generation of a large number of particles, are carried out.
Abstract
A generic formulation of a new method for packing particles is presented. It is based on a constructive advancing front method, and uses Monte Carlo techniques for the generation [...]
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The Double Hierarchy Method. A parallel 3D contact method for the interaction of spherical particles with rigid FE boundaries using the DEM
M. Santasusana, J. Irazábal, E. Oñate, J. Carbonell

Comp. Part. Mech (2016). Vol. 3, pp. 407-428

Abstract
In this work, we present a new methodology for the treatment of the contact interaction between rigid boundaries and spherical discrete elements (DE). Rigid body parts are present in most of large-scale simulations. The surfaces of the rigid parts are commonly meshed with a finite element-like (FE) discretization. The contact detection and calculation between those DE and the discretized boundaries is not straightforward and has been addressed by different approaches. The algorithm presented in this paper considers the contact of the DEs with the geometric primitives of a FE mesh, i.e. facet, edge or vertex. To do so, the original hierarchical method presented by Horner et al. (J Eng Mech 127(10):1027–1032, 2001) is extended with a new insight leading to a robust, fast and accurate 3D contact algorithm which is fully parallelizable. The implementation of the method has been developed in order to deal ideally with triangles and quadrilaterals. If the boundaries are discretized with another type of geometries, the method can be easily extended to higher order planar convex polyhedra. A detailed description of the procedure followed to treat a wide range of cases is presented. The description of the developed algorithm and its validation is verified with several practical examples. The parallelization capabilities and the obtained performance are presented with the study of an industrial application example.
Abstract
In this work, we present a new methodology for the treatment of the contact interaction between rigid boundaries and spherical discrete elements (DE). Rigid body parts are [...]
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A modular, partitioned, discrete element framework for industrial grain distribution systems with rotating machinery
G. Casas, D. Mukherjee, M. Celigueta, T. Zohdi, E. Oñate

Comp. Part. Mech (2017). Vol. 4 (2), pp. 181-198

Abstract
A modular discrete element framework is presented for large-scale simulations of industrial grain-handling systems. Our framework enables us to simulate a markedly larger number of particles than previous studies, thereby allowing for efficient and more realistic process simulations. This is achieved by partitioning the particle dynamics into distinct regimes based on their contact interactions, and integrating them using different time-steps, while exchanging phase-space data between them. The framework is illustrated using numerical experiments based on fertilizer spreader applications. The model predictions show very good qualitative and quantitative agreement with available experimental data. Valuable insights are developed regarding the role of lift vs drag forces on the particle trajectories in-flight, and on the role of geometric discretization errors for surface meshing in governing the emergent behavior of a system of particles.
Abstract
A modular discrete element framework is presented for large-scale simulations of industrial grain-handling systems. Our framework enables us to simulate a markedly larger [...]
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Computation of the stabilization parameter for the finite element solution of advective–diffusive problems
E. Oñate, J. García-Espinosa, S. Idelsohn

Int. J. for Num. Meths. in Fluids (1997). Vol. 25, pp. 1387-1407

Abstract
In a previous paper a general procedure for deriving stabilized finite element schemes for advective type problems based on invoking higher order balance laws over finite size domains was presented. This provides an expression for the element stabilization parameter in terms of the solution residual and its first derivatives in a kind of iterative or adaptative manner. Details of the application of this procedure to 1D and 2D advective- diffusive problems are given. Some examples of applications showing the potential of the new approach are presented.
Abstract
In a previous paper a general procedure for deriving stabilized finite element schemes for advective type problems based on invoking higher order balance laws over finite [...]
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A Comparison of two objective stress rates in object-oriented codes
A. Rodríguez-Ferran, A. Huerta

Monograph CIMNE (1994). M26

Abstract
An object-oriented code, CASTEM2000, has provided the framework for algorithmic development and numerical testing. In these codes, information is stored and manipulated as objects which represent the entitiesrelevant to a finite element method computation.
Abstract
An object-oriented code, CASTEM2000, has provided the framework for algorithmic development and numerical testing. In these codes, information is stored and manipulated as [...]
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A rate dependent plastic-damage constitutive model for large scale computational in concrete structures
R. Faria, J. Oliver

Monograph CIMNE (1993). M17
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Composite materials non-linear modelling for long fibre-reinforced laminates: Continuum basis, computational aspects and validations
F. Rastellini, S. Oller, O. Salomon, E. Oñate

Computers and Structures (2008). Vol. 86 (9), pp. 879-896

Abstract
An innovative computational methodology is proposed for modelling the material non-linearmechanical behaviour of FRP structures. To model a single unidirectional composite lamina, a serial–parallel (SP) continuum approach has been developed assuming that components behave as parallel materials in the fibres alignment direction and as serial materials in orthogonal directions. The model is based on the appropriate management of the constitutive models of the component materials, by making use of suitable ‘closure equations’ that characterize the composite micro-mechanics [Rastellini F. Modelización numérica de la no-linealidad constitutiva de laminados compuestos. PhD thesis. ETSECCPB, Politechnical University of Catalonia, Barcelona, March, 2006. [in Spanish]]. Classical lamination theory is combined with the SP model to describe multidirectional laminates. The methodology is validated through several numerical analyses, which are contrasted against benchmark tests and experimental data taken from the world-wide failure exercise [Hinton MJ, Soden PD. Predicting failure in composite laminates: The background to the exercise. Comp Sci Technol 1998; 58:1001–10].
Abstract
An innovative computational methodology is proposed for modelling the material non-linearmechanical behaviour of FRP structures. To model a single unidirectional composite [...]
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An integration of a low cost adaptive remeshing strategy in the solution of structural shape optimization problems using evolutionary methods
G. Bugeda, J. Ródenas, E. Oñate

Computers and Structures (2008). Vol. 86 (13-14), pp. 1563-1578

Abstract
Evolutionary methods are a powerful and robust tool for the solution of structural shape optimization problems. Nevertheless, the use of these methods requires the structural analysis of an important number of different designs, this making the computational cost of the analysis of each design a critical issue. For this reason, each design must be analyzed at a minimum computational cost but ensuring a minimum quality of the results. It is well known that the cheapest mesh for producing a solution with a fixed quality at minimum cost is an adapted one. Nevertheless, traditional adapted meshes are obtained from adaptive remeshing strategies, where each design has to be analyzed more than once, thereby also causing a high computational cost. This work presents a new strategy that allows generating an adapted mesh for each design without the necessity of performing a full adaptive remeshing procedure for each of them. It is based on the use of sensitivity analysis of all magnitudes related with adaptive remeshing (location of nodes, error estimation, etc.) with respect to the design variables. This sensitivity analysis is performed only once using a geometry of reference and it is used to project the results of the corresponding analysis to all other designs to be analyzed. The projected information allows generating an appropriate adapted mesh for each new design in one shot, greatly reducing the computational cost compared with standard strategies.
Abstract
Evolutionary methods are a powerful and robust tool for the solution of structural shape optimization problems. Nevertheless, the use of these methods requires the structural [...]
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Integration methodology of different softwares for constrained tubular truss size optimization problems
C. Lage, F. Neves, M. Freitas

Rev. int. métodos numér. cálc. diseño ing. (2019). Vol. 35, (3), 42

Abstract
Practical size structural optimization problems can involve a large number of variables and constraints that meet regulatory requirements for safety and structural performance. Most optimization problems tend to find the minimum value of the objective function within a feasible set that satisfies the constraints. Among evolutionary computation techniques, genetic algorithms (GAs) have been successfully used for the optimization of structures, including lattice systems. This article proposes an automated interactive methodology for the optimization of structures based on the integration of two commercial programs: Ansys and Matlab. The developed script uses the Finite Element Method for the analysis of the structure, together with the Genetic Algorithms for the optimization. The objective of the article is to evaluate the applicability, precision and efficiency of the proposed methodology. Two numerical examples of trusses were solved with the proposed methodology, classic truss of the literature and truss with normative restrictions. The results show that the methodology is adequate for the solution of size structural optimization problems with a good precision of the results.
Abstract
Practical size structural optimization problems can involve a large number of variables and constraints that meet regulatory requirements for safety and structural performance. [...]
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Análisis de problemas de choque e impacto entre sólidos deformables por el Método de los Elementos Finitos.
J. Miquel, E. Oñate, C. Garino, S. Botello, F. Flores, J. Rojek

Monograph CIMNE (1994). M25

Abstract
El trabajo que se expone ha hecho uso de los últimos avances en mecánica computacional, métodos numéricos, visualización y algoritmos de cálculo para obtener un programa de ordenador para simulación de problemas de choque e impacto de interés práctico para una amplia variedad de sectores industriales. En particular, el objetivo del proyecto SIMPACT ha sido el desarrollo de un paquete de software para análisis de problemas de dinámica rápida y análisis no lineal procesable en una amplia variedad de ordenadores, con aplicación a choques de vehículos, impacto en estructuras aeroespaciales, defensa y problemas de conformado, entre otros.
Abstract
El trabajo que se expone ha hecho uso de los últimos avances en mecánica computacional, métodos numéricos, visualización y algoritmos de [...]
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Estructuras de edificación con aislaminto antisísmico
L. Jané, A. Barbat

Monograph CIMNE (1992). M13
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Estimación y corrección del error en el análisis estructural por el MEF
G. Bugeda

Monograph CIMNE (1991). M9

Abstract
En los últimos años se han desarrollado diversas técnicas para resolver el problema de la estimación y la corrección del error. De hecho, la mayoría de los avances que se han realizado dentro del campo de los elementos finitos se pueden entender como formas distingas de minimizar el error existente en las soluciones. En esta monografía se hablará de dos técnicas distintas para la corrección de errores: Técnicas de refinamiento y técnicas de remallado.
Abstract
En los últimos años se han desarrollado diversas técnicas para resolver el problema de la estimación y la corrección del error. De hecho, [...]
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Modelización numérica de materiales friccionales
S. Oller

Monograph CIMNE (1991). M10

Abstract
La presente monografía trata el problema del comportamiento de los materiales friccionales, especialmente del hormigón, más allá de su límite elástico. Estudia los problemas de aplastamiento y fractura y describe un modelo constitutivo amplio que permite una muy adecuada simulación de estos fenómenos.
Abstract
La presente monografía trata el problema del comportamiento de los materiales friccionales, especialmente del hormigón, más allá de su límite [...]
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A Finite Element formulation for the numerical solution of the convection-diffusion equation
R. Codina

Monograph CIMNE (1993). M14

Abstract
In this work we present several finite element techniques to solve the convection-diffusion equation when the Péclet number is high, tha is, when diffusion is very small. The basic finite element formulation employed here is the Streamline-Upwind-Petrov-Galerkin (SUPG). A thorough description of this approach is presented in Chapter 1. Chapter 2 deals with the application of the generalized trapezoidal rule to advance in time for the transient equation. A complete stability and accuracy analysis is performed for the explicit Euler scheme, both using linear and quadratic finite elements. Chapter 3 is concerned with the problem of removing the localized oscillations that remain about abrupt layers of the solution.
Abstract
In this work we present several finite element techniques to solve the convection-diffusion equation when the Péclet number is high, tha is, when diffusion is very [...]
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Mechanics of a continuum medium. Vol. III
A. Fusco

Monograph CIMNE (1993). M20

Abstract
This work presents the fundamental assumptions and the successive mathematical developments which allow to establish the complete field equations of a continuum. The aim is to be sufficiently general and self-content using, however, mathematical procedures which can be always understook by an engineer with a common background of Linear Algebra and elementary Differential Calculus.
Abstract
This work presents the fundamental assumptions and the successive mathematical developments which allow to establish the complete field equations of a continuum. The aim is [...]
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A Finite Element formulation for viscous incompressible flows
R. Codina

Monograph CIMNE (1993). M16
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Modelado de la fisuración en estructuras de hormigón
J. Oliver

Monograph CIMNE (1993). M15

Abstract
En este trabajo, se presenta una perspectiva general de los modelos de fisuración existentes y de algunas aportaciones de la línea de investigación que se desarrollan, tanto en el dominio de la formulación teórica de dichos modelos como de su aplicación práctica.
Abstract
En este trabajo, se presenta una perspectiva general de los modelos de fisuración existentes y de algunas aportaciones de la línea de investigación que [...]
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Particle finite element method in fluid-mechanics including thermal convection-diffusion
S. Idelsohn, R. Aubry, E. Oñate

Computers and Structures (2005). Vol. 83 (17-18), pp. 1459-1475

Abstract
A method is presented for the solution of an incompressible viscous fluid flow with heat transfer using a fully Lagrangian description of the motion. Due to the severe element distortion, a frequent remeshing is performed in an efficient manner. An implicit time integration through a classical fractional step is presented. The non-linearities of the formulation are taken into account and solved with the fixed-point iteration method. The displacement and temperature solutions are coupled through the Boussinesq approximation. The Lagrangian formulation provides an elegant way of solving free-surface problems with thermal convection as the particles are followed during their motion. To illustrate the method, the Rayleigh–Bénard instability with and without free surface in two dimensions has been computed.
Abstract
A method is presented for the solution of an incompressible viscous fluid flow with heat transfer using a fully Lagrangian description of the motion. Due [...]
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A Lagrangian meshless finite element method applied to fluid–structure interaction problems
S. Idelsohn, E. Oñate, F. Del Pin

Computers and Structures (2003). Vol. 81 (8-11), pp. 655-671

Abstract
A method is presented for the solution of the incompressible fluid flow equations using a Lagrangian formulation. The interpolation functions are those used in the meshless finite element method and the time integration is introduced in a semi-implicit way by a fractional step method. Classical stabilization terms used in the momentum equations are unnecessary due to the lack of convective terms in the Lagrangian formulation. Furthermore, the Lagrangian formulation simplifies the connections with fixed or moving solid structures, thus providing a very easy way to solve fluid–structure interaction problems.
Abstract
A method is presented for the solution of the incompressible fluid flow equations using a Lagrangian formulation. The interpolation functions are [...]
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Lectures on nonlinear finite element analysis of concrete shells
E. Oñate

Monograph CIMNE (1991). M7

Abstract
This monograph presents 4 lectures on non linear analysis of concrete shells by the finite element method. The lectures were prepared by the author for the course on "Non linear analysis of shells by finite elements" held at the International Center for Mechanics Sciences in Udine, Italy on June 24-28th 1991. The content of the lectures presents an overview of the different aspects involved in the analysis of concrete shells by finite elements. Thus, Lecture 1 introdeuces the basic concepts of the analysis of reinforced concrete shell structures using flat shell and curved degenerated layered shell finite elements. Both the geometric and kinematic assumptions are described in detail together with the respective finite element formulation and the numerical algorithm for non linear elasto-plastic analysis including the effect of moderately large displacements. Lecture 2 presents an overview of the constitutive behaviour of concrete and steel in a form suitable for numerical computations using the finite element models described in previous lecture. The reinforcing steel bars are modelled with a simple elasto-plastic model. Hovewer, two conceptualy different concrete models are presented. The first model is based on elasto-plastic theory to describe the compressive behaviour of concrete, whereas a linear orthotropic elasto-brittle model is used for modelling the cracking behaviour under tensile conditions. This ``elasto-platic-brittle model has been extensively used by Owen and Figueiras and most of the concepts presented emanate from reference [18] of this chapter. The second model is based on the assumptions that both the tensile and compressive behaviour of concrete can be treated under the unified framework of elasto-plasticity theory. This model termed ``plastic-damage model has ben proposed by Lubliner, Oller, Oliver and O\~nate in different publications which main concepts are summarized in the lecture (see refs. [33-38] of this chapter). In Lecture 3 the basic finite element formulation for the analysis of stiffened concrete shells via the use of eccentric beams is described. Finally, in Lecture 4 some examples of applications of the finite element formulations presented to the non-linear analysis of different reinforced concrete shell structures analyzed by different authors are described. Examples included range from the analysis of plain and pre-stressed concrete deep beams, to more sophisticated shell type structures including the nonlinear behaviour of a composite steel-concrete girder bridge and a cryogenic concrete liquid gas tank under severe thermal conditions. This monograph has been written exclusively with didactic purposes. Most of the ideas included in the text have been extracted from research publications by the author and many others. The interested reader will be able to find details on the different subjects treated in the many references included at the end of each chapter.
Abstract
This monograph presents 4 lectures on non linear analysis of concrete shells by the finite element method. The lectures were prepared by the author for the course on "Non [...]
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Análisis dinámico de presas
J. Canet, E. Oñate, J. Buil, E. Herrero

Monograph CIMNE (1991). M5

Abstract
Se desarrolla en este trabajo un estudio numérico-experimental acerca del comportamiento dinámico de las presas bóvedas considerando su interacción con el agua del embalse. Para ello, se ha realizado un análisis de los factores que inciden más directamente en el comportamiento dinámico de tales tipos de estructuras. Dicho análisis se realiza mediante e lmétodo de los elementos finitos, estudiando distintas alternativas de formulación. Asimismo, se ha realizado un esayo a escala real de una presa bóveda existente, mediante una serie de explosiones y midiendo la respuesta obtenida.
Abstract
Se desarrolla en este trabajo un estudio numérico-experimental acerca del comportamiento dinámico de las presas bóvedas considerando su interacción [...]
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Simulación Numérica de Patologías en Presas de Hormigón
M. Cervera, J. Oliver, M. Galindo

Monograph CIMNE (1991). M4
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Stress, strain and energy splittings for anisotropic elastic solids under volumetric constraints
C. Felippa, E. Oñate

Computers and Structures (2003). Vol. 81 (13), pp. 1343-1357

Abstract
We define stress and strain splittings appropriate to linearly elastic anisotropic materials with volumetric constraints. The treatment includes rigidtropic materials, which develop no strains under a stress pattern that is a null eigenvector of the compliance matrix. This model includes as special case incompressible materials, for which the eigenvector is hydrostatic stress. The main finding is that pressure and volumetric strain must be redefined as effective quantities. Using this idea, an energy decomposition that exactly separates deviatoric and volumetric energy follows.
Abstract
We define stress and strain splittings appropriate to linearly elastic anisotropic materials with volumetric constraints. The treatment includes rigidtropic materials, [...]
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A finite element methodology for local/global damage evaluation in civil engineering structures
A. Hanganu, E. Oñate, A. Barbat

Computers and Structures (2002). Vol. 80 (20-21), pp. 1667-1687

Abstract
The paper introduces a new global damage evaluation method which leads to a meaningful global damage index. A numerical procedure for the prediction of local and global damage in civil engineering structures using the finite element method and a continuum damage model, is presented. The method is adequate for the computation of the limit load in reinforced concrete (RC) structures and for the prediction of the failure mechanisms. Details of the applied damage model are given together with a description of the finite element implementation and the procedure for computing the global damage parameters. Examples of applications of the methodology to the nonlinear analysis of a range of RC structures, are presented.
Abstract
The paper introduces a new global damage evaluation method which leads to a meaningful global damage index. A numerical procedure for the prediction of local and [...]
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Some algorithms to correct a geometry in order to create a finite element mesh
R. Ribó, G. Bugeda, E. Oñate

Computers and Structures (2002). Vol. 80 (16-17), pp. 1399-1408

Abstract
One of the major difficulties in meshing 3D complex geometries is to deal with non-proper geometrical definitions coming from CAD systems. Typically, CAD systems do not take care of the proper definition of the geometries for the analysis purposes. In addition, the use of standard CAD files (IGES, VDA, …) for the transfer of geometries between different systems introduce some additional difficulties. In this work, a collection of algorithms to repair and/or to improve the geometry definitions are provided. The aim of these algorithms is to make as easy as possible the generation of a mesh over complex geometries given some minimum requirements of quality and correctness. The geometrical model will be considered as composed of a set of NURBS lines and trimmed surfaces. Some examples of application of the algorithms and of the meshes generated from the corrected geometry are also presented in this work.
Abstract
One of the major difficulties in meshing 3D complex geometries is to deal with non-proper geometrical definitions coming from CAD systems. Typically, [...]
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A scalar damage model with a shear retention factor for the analysis of reinforced concrete structures: theory and validation
R. Scotta, R. Vitaliani, A. Saetta, E. Oñate, A. Hanganu

Computers and Structures (2001). Vol. 79 (7), pp. 737-755

Abstract
A local isotropic single parameter scalar model that can simulate the mechanical behaviour of quasi-brittle materials, such as concrete, is described. The constitutive law needs the mechanical characteristics and the fracture energy of concrete to be completely defined. The damage parameter is obtained directly from the value of an equivalent effective stress in order to reduce the computing effort. Due to the unique damage parameter, this model is suitable for the study of quasi-static problems involving monotonically increasing loads. The problem of localisation and mesh dependency have been partially overcome by using an enhanced local method in which a characteristic internal length related to the mesh dimension is employed instead of the characteristic fracture length. In this work, the model was enriched further with the introduction of a shear retention factor that accounts for the friction between the two surfaces of a crack. These new features assure a real improvement of the damage model, maintaining nevertheless its simplicity and low computing cost and making it suitable for the practical solution of large scale problems. Several numerical simulations of experimental tests, concerning fracture tests on concrete specimens and beams failing in shear, have been performed for the validation of the model. The main results from the numerical analyses are described and compared with the experimental ones.
Abstract
A local isotropic single parameter scalar model that can simulate the mechanical behaviour of quasi-brittle materials, such as concrete, is described. [...]
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A finite point method for elasticity problems
E. Oñate, F. Perazzo, J. Canet

Computers and Structures (2001). Vol. 79 (22-25), pp. 2151-2163

Abstract
The basis of the finite point method (FPM) for the fully meshless solution of elasticity problems in structural mechanics is described. A stabilization technique based on a finite calculus procedure is used to improve the quality of the numerical solution. The efficiency and accuracy of the stabilized FPM in the meshless analysis of simple linear elastic structural problems is shown in some examples of applications.
Abstract
The basis of the finite point method (FPM) for the fully meshless solution of elasticity problems in structural mechanics is described. A stabilization [...]
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A layer-wise triangle for analysis of laminated composite plates and shells
S. Botello, E. Oñate, J. Miquel

Computers and Structures (1999). Vol. 70 (6), pp. 635-646

Abstract
The paper presents a new triangle for analysis of laminate plates and shells. The in-plane degrees of freedom are interpolated quadratically whereas a linear layer-wise approximation is chosen for the normal displacement. A substructuring technique is used to eliminate the in-plane degrees of freedom during the assembly process thus reducing substantially the computationed costs. The element performance is evaluated in the static and dynamic analysis of dierent laminate plate and shell structures
Abstract
The paper presents a new triangle for analysis of laminate plates and shells. The in-plane degrees of freedom are interpolated quadratically whereas a linear layer-wise approximation [...]
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Plate bending elements with discrete constraints: New triangular elements
O. Zienkiewicz, R. Taylor, P. Papadopoulos, E. Oñate

Computers and Structures (1990). Vol. 35 (4), pp. 505-522

Abstract
In recent years a series of elements based on Reissner-Mindlin assumptions and using discrete (collocation type) constraints has been introduced. These elements have proved to be very effective, however their relation to straightforward mixed approximations has not been clear. In this paper this relationship is discussed and the reasons for their success explained. This allows new and effective triangular elements to be developed. The presentation shows the close relationships with the DKT (Discrete Kirchhoff Theory) element previously available only for thin plates and allows extension of their applications.
Abstract
In recent years a series of elements based on Reissner-Mindlin assumptions and using discrete (collocation type) constraints has been introduced. These elements have [...]
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Dynamic analysis of structures using a Reissner-Mindlin finite strip formulation
J. Canet, B. Suarez, E. Oñate

Computers and Structures (1989). Vol. 31 (6), pp. 967-975

Abstract
In this paper a finite strip formulation based on Reissner-Mindlin plate theory for dynamic analysis of prismatic shell type structure is presented. Detailed expressions of the relevant strip matrices for a variety of structures using the simple two node linear strip element are given. Examples of the good performance of the linear strip element for free and forced vibration analysis of plates, bridges and axisymmetric shells are presented.
Abstract
In this paper a finite strip formulation based on Reissner-Mindlin plate theory for dynamic analysis of prismatic shell type structure is presented. Detailed expressions of [...]
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A comparison of the linear, quadratic and cubic mindlin strip elements for the analysis of thick and thin plates
E. Oñate, B. Suarez

Computers and Structures (1983). Vol. 17 (3), pp. 427-439

Abstract
The behaviour of the linear, quadratic and cubic elements of the Mindlin plate strip family for thick and very thin plate analysis is investigated in this paper. Selective integration techniques are used to ensure the good behaviour of the elements when dealing with thin plates. Numerical results showing the convergence and accuracy of the elements for the analysis of plates of a wide range of thicknesses are given. The general performance of the three elements is discussed in detail. In particular, the linear element with a single integration point seems to be the best value strip element for practical purposes.
Abstract
The behaviour of the linear, quadratic and cubic elements of the Mindlin plate strip family for thick and very thin plate analysis is investigated in this paper. Selective [...]
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A unified approach for the analysis of bridges, plates and axisymmetric shells using the linear mindlin strip element
E. Oñate, B. Suarez

Computers and Structures (1983). Vol. 17 (3), pp. 407-426

Abstract
In this paper a finite strip formulation which allows to treat bridges, axisymmetric shells or plate structures of constant transverse cross section in an easily and unified manner is presented. The formulation is based on Mindlin's shell plate theory. One dimensional finite elements are used to discretize the transverse section and Fourier expansions are used to define the longitudinal/circumferential behavior of the structure. The element used is the simple two noded strip element with just one single integrating point. This allows to obtain all the element matrices in an explicit and economical form. Numerical examples for a variety of straight and curve bridges, axisymmetric shells and plate structures which show the efficiency of the formulation and accuracy of the linear strip element are given.
Abstract
In this paper a finite strip formulation which allows to treat bridges, axisymmetric shells or plate structures of constant transverse cross section in an easily and unified [...]
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2D particle contact-based meshfree method in CDEM and its application in geotechnical problems
C. Feng, S. Li, E. Oñate

Engineering Computations (2015). Vol. 32 (4), pp. 1080-1103

Abstract
Purpose – Continuum-based discrete element method is an explicit numerical method, which is a combination of block discrete element method (DEM) and FEM. When simulating large deformation problems, such as cutting, blasting, water-like material flowing, the distortion of elements will lead to no convergence of the numerical system. To solve the convergence problem, a particle contact-based meshfree method (PCMM) is introduced in. The paper aims to discuss this issue. Design/methodology/approach – PCMM is based on traditional particle DEM, and use particle contacts to generate triangular elements. If three particles are contact with each other, the element will be created. Once elements are created, the macroscopic constitutive law could be introduced in. When large deformation of element occurs, the contact relationship between particles will be changed. Those elements that do not meet the contact condition will be deleted, and new elements that coincide with the relationship will be generated. By the deletion and creation of elements, the convergence problem induced by element distortion will be eliminated. To solve FEM and PCMM coupled problems, a point-edge contact model is introduced in, and normal and tangential springs are adopted to transfer the contact force between particles and blocks. Findings – According to the deletion and recreation of elements based on particle contacts, PCMM could simulate large deformation problems. Some numerical cases (i.e. elastic field testing, uniaxial compression analysis and wave propagation simulation) show the accuracy of PCMM, and others (i.e. soil cutting, contact burst and water-like material flowing) show the rationality of PCMM. Originality/value – In traditional particle DEM, contact relationships are used to calculate contact forces. But in PCMM, contact relationships are adopted to generate elements. Compared to other meshfree methods, in PCMM, the element automatic deletion and recreation technique is used to solve large deformation problems.
Abstract
Purpose – Continuum-based discrete element method is an explicit numerical method, which is a combination of block discrete element method (DEM) [...]
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Validation of the particle finite element method (PFEM) for simulation of free surface flows
A. Larese, R. Rossi, E. Oñate, S. Idelsohn

Engineering Computations (2008). Vol. 25 (3-4), pp. 385-425

Abstract
Purpose – The purpose of this paper is to evaluate the possibilities of the particle finite element method for simulation of free surface flows. Design/methodology/approach – A numerical simulation of a number of examples for which experimental data are available is performed. The simulations are run using the same scale as the experiment in order to minimize errors due to scale effects. Some examples are chosen from the civil engineering field: a study of the flow over a flip bucket is analyzed for both 2D and 3D models, and the flow under a planar sluice gate is studied in 2D. Other examples, such as a 2D and 3D “dam break” with an obstacle are taken from the smooth particle hydrodynamics literature. Findings – Different scenarios are simulated by changing the boundary conditions for reproducing flows with the desired characteristics. Different mesh sizes are considered for evaluating their influence on the final solution. Originality/value – Details of the input data for all the examples studied are given. The aim is to identify benchmark problems for future comparisons between different numerical approaches for free surface flows.
Abstract
Purpose – The purpose of this paper is to evaluate the possibilities of the particle finite element method for simulation of free surface flows. Design/methodology/approach [...]
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Non‐linear explicit dynamic analysis of shells using the BST rotation‐free triangle
E. Oñate, P. Cendonya, J. Canet

Engineering Computations (2002). Vol. 19 (5-6), pp. 662-706

Abstract
The paper describes the application of the simple rotation‐free basic shell triangle (BST) to the non‐linear analysis of shell structures using an explicit dynamic formulation. The derivation of the BST element involving translational degrees of freedom only using a combined finite element–finite volume formulation is briefly presented. Details of the treatment of geometrical and material non linearities for the dynamic solution using an updated Lagrangian description and an hypoelastic constitutive law are given. The efficiency of the BST element for the non linear transient analysis of shells using an explicit dynamic integration scheme is shown in a number of examples of application including problems with frictional contact situations.
Abstract
The paper describes the application of the simple rotation‐free basic shell triangle (BST) to the non‐linear analysis of shell structures using an explicit dynamic formulation. [...]
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A residual correction method based on finite calculus
E. Oñate, R. Taylor, O. Zienkiewicz, J. Rojek

Engineering Computations (2003). Vol. 20 (5-6), pp. 629-658

Abstract
In this paper, a residual correction method based upon an extension of the finite calculus concept is presented. The method is described and applied to the solution of a scalar convection‐diffusion problem and the problem of elasticity at the incompressible or quasi‐incompressible limit. The formulation permits the use of equal interpolation for displacements and pressure on linear triangles and tetrahedra as well as any low order element type. To add additional stability in the solution, pressure gradient corrections are introduced as suggested from developments of sub‐scale methods. Numerical examples are included to demonstrate the performance of the method when applied to typical test problems.
Abstract
In this paper, a residual correction method based upon an extension of the finite calculus concept is presented. The method is described and applied to the solution of a scalar [...]
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Direct computation of instability points with inequality constraints using the FEM
H. Tschöpe, P. Wriggers, E. Oñate

Engineering Computations (2003). Vol. 20 (5-6), pp. 611-628

Abstract
The subject of this paper is the computation of instability points in mechanical problems with the finite element method. The objective is to extend the application of critical point detection methods to problems with inequality constraints originating from damage and contact. A simple bilinear model is considered for the damage problems. A bilateral, frictionless contact formulation is used for the contact problems. Among the critical point detection methods the focus is laid on the critical displacement method and the extended system. At first a possible combination of both methods is evaluated by applying them to damage problems. A prediction method based on the extended system is developed to facilitate the comparison of both methods. Secondly, the extended system is used as a computation method for critical points in two‐dimensional contact problems.
Abstract
The subject of this paper is the computation of instability points in mechanical problems with the finite element method. The objective is to extend the application of critical [...]
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Direct computation of instability points with inequality constraints using the FEM
H. Tschöpe, P. Wriggers, E. Oñate

Engineering Computations (2003). Vol. 20 (5-6), pp. 611-628

Abstract
The subject of this paper is the computation of instability points in mechanical problems with the finite element method. The objective is to extend the application of critical point detection methods to problems with inequality constraints originating from damage and contact. A simple bilinear model is considered for the damage problems. A bilateral, frictionless contact formulation is used for the contact problems. Among the critical point detection methods the focus is laid on the critical displacement method and the extended system. At first a possible combination of both methods is evaluated by applying them to damage problems. A prediction method based on the extended system is developed to facilitate the comparison of both methods. Secondly, the extended system is used as a computation method for critical points in two‐dimensional contact problems.
Abstract
The subject of this paper is the computation of instability points in mechanical problems with the finite element method. The objective is to extend the application of critical [...]
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The extended Delaunay tessellation
N. Calvo, S. Idelsohn, E. Oñate

Engineering Computations (2003). Vol. 20 (5-6), pp. 583-600

Abstract
The extended Delaunay tessellation (EDT) is presented in this paper as the unique partition of a node set into polyhedral regions defined by nodes lying on the nearby Voronoï spheres. Until recently, all the FEM mesh generators were limited to the generation of tetrahedral or hexahedral elements (or triangular and quadrangular in 2D problems). The reason for this limitation was the lack of any acceptable shape function to be used in other kind of geometrical elements. Nowadays, there are several acceptable shape functions for a very large class of polyhedra. These new shape functions, together with the EDT, gives an optimal combination and a powerful tool to solve a large variety of physical problems by numerical methods. The domain partition into polyhedra presented here does not introduce any new node nor change any node position. This makes this process suitable for Lagrangian problems and meshless methods in which only the connectivity information is used and there is no need for any expensive smoothing process.
Abstract
The extended Delaunay tessellation (EDT) is presented in this paper as the unique partition of a node set into polyhedral regions defined by nodes lying on the nearby Voronoï [...]
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Numerical modelling and simulation of frictional contact using a generalised coulomb law
A. Heege, P. Alart, E. Oñate

Engineering Computations (1995). Vol. 12 (7), pp. 641-656

Abstract
A consistent formulation for unilateral contact problems including frictional work hardening or softening is proposed. The approach is based on an augmented Lagrangian approach coupled to an implicit quasi‐static Finite Element Method. Analogous to classical work hardening theory in elasto‐plasticity, the frictional work is chosen as the internal variable for formulating the evolution of the friction convex. In order to facilitate the implementation of a wide range of phenomenological models, the friction coefficient is defined in a parametrised form in terms of Bernstein polynomials. Numerical simulation of a 3D deep‐drawing operation demonstrates the performance of the methods for predicting frictional contact phenomena in the case of large sliding paths including high curvatures.
Abstract
A consistent formulation for unilateral contact problems including frictional work hardening or softening is proposed. The approach is based on an augmented Lagrangian approach [...]
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An anisotropic elastoplastic model based on an isotropic formulation
S. Oller, S. Botello, J. Canet, E. Oñate

Engineering Computations (1995). Vol. 12 (3), pp. 245-262

Abstract
This paper shows a generalization of the classic isotropic plasticity theory to be applied to orthotropic or anisotropic materials. This approach assumes the existence of a real anisotropic space, and other fictitious isotropic space where a mapped fictitious problem is solved. Both spaces are related by means of a linear transformation using a fourth order transformation tensor that contains all the information concerning the real anisotropic material. The paper describes the basis of the spaces transformation proposed and the expressions of the resulting secant and tangent constitutive equations. Also details of the numerical integration of the constitutive equation are provided. Examples of application showing the good performance of the model for analysis of orthotropic materials and fibre‐reinforced composites are given.
Abstract
This paper shows a generalization of the classic isotropic plasticity theory to be applied to orthotropic or anisotropic materials. This approach assumes the existence of [...]
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Derivation of thin plate bending elements with one degree of freedom per node: a simple three node triangle
E. Oñate, M. Cervera

Engineering Computations (1993). Vol. 10 (6), pp. 543-561

Abstract
A general methodology for deriving thin plate bending elements with a single degree of freedom per node is presented. The formulation is based on the combination of a standard C0 finite element interpolation for the deflection field with an independent approximation of the curvatures which are expressed in terms of the deflection gradient along the sides using a finite volume‐like approach. The formulation is particularized for the simplest element of the family, i.e. the three node triangle with three degrees of freedom. The potential of the new element is shown through different examples of application.
Abstract
A general methodology for deriving thin plate bending elements with a single degree of freedom per node is presented. The formulation is based on the combination of a standard C0 [...]
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Analysis of some partitioned algorithms for fluid-structure interaction
R. Rossi, E. Oñate

Engineering Computations (2010). Vol. 27 (1), pp. 20-56

Abstract
The field of fluid-structure interaction (FSI) has important applications ranging from the bio-medical to the civil and aeronautical engineering fields. Despite the different approaches developed over recent years the general solution of FSI problems remains however far from being closed. This paper addresses the theoretical analysis of a several partitioned solution schemes for FSI. This is achieved by choosing a simple but representative model problem which allows to obtain analytical results. A loose coupling partitioned procedure is presented first. An iterative version of the same algorithm is presented next together with an analysis of its convergence properties and a brief discussion of a possible acceleration strategy. Finally a new iterative strategy based on solving a modified equation is described. Some examples of application of the partitioned algorithms considered are presented including the aeroelastic analysis of a bridge.
Abstract
The field of fluid-structure interaction (FSI) has important applications ranging from the bio-medical to the civil and aeronautical engineering fields. Despite the different [...]
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A study of mesh optimality criteria in adaptive finite element analysis
E. Oñate, G. Bugeda

Engineering Computations (1993). Vol. 10 (4), pp. 307-321

Abstract
The concepts of solution error and optimal mesh in adaptive finite element analysis are revisited. It is shown that the correct evaluation of the convergence rate of the error norms involved in the error measure and the optimal mesh criteria chosen are essential to avoid oscillations in the refinement process. Two mesh optimality criteria based on: (a) the equal distribution of global error, and (b) the specific error over the elements are studied and compared in detail through some examples of application.
Abstract
The concepts of solution error and optimal mesh in adaptive finite element analysis are revisited. It is shown that the correct evaluation of the convergence rate of the error [...]
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Combination of the critical displacement method with a damage model for structural instability analysis
E. Oñate, H. Tschöpe, P. Wriggers

Engineering Computations (2001). Vol. 18 (3-4), pp. 642-662

Abstract
The paper describes the extension of the critical displacement method (CDM), presented by Oñate and Matias in 1996, to the instability analysis of structures with non-linear material behaviour using a simple damage model. The extended CDM is useful to detect instability points using a prediction of the critical displacement field and a secant load-displacement relationship accounting for material non-linearities. Examples of application of CDM to the instability analysis of structures using bar and solid finite elements are presented.
Abstract
The paper describes the extension of the critical displacement method (CDM), presented by Oñate and Matias in 1996, to the instability analysis of structures with [...]
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Free vibration analysis of plates, bridges and axisymmetric shells using a thick finite strip method
B. Suarez, J. Canet, E. Oñate

Engineering Computations (1988). Vol. 5 (2), pp. 158-164

Abstract
A unified approach for the vibration analysis of curved or straight prismatic plates and bridges and axisymmetric shells using a finite strip method based in Reissner—Mindlin shell theory is presented. Details of obtaining all relevant strip matrices and vectors are given. It is also shown how the use of the simple linear two node strip with reduced integration leads to direct explicit forms of all relevant matrices. Examples of application which show the accuracy of the linear strip for free vibration analysis of structures are presented.
Abstract
A unified approach for the vibration analysis of curved or straight prismatic plates and bridges and axisymmetric shells using a finite strip method based in Reissner—Mindlin [...]
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A constitutive model for cracking of concrete based on the incremental theory of plasticity
E. Oñate, S. Oller, J. Oliver, J. Lubliner

Engineering Computations (1988). Vol. 5 (4), pp. 309-319

Abstract
A constitutive model based on classical plasticity theory for non‐linear analysis of concrete structures using finite elements is presented. The model uses the typical parameters of non‐associated plasticity theory for frictional materials and a modified Mohr‐Coulomb yield surface is suggested. Onset and amount of cracking at a point are controlled by the values of the effective plastic strain and thus it can be studied by a posteriori postprocessing of numerical results. The accuracy and objectivity of the model is checked out with some examples of application.
Abstract
A constitutive model based on classical plasticity theory for non‐linear analysis of concrete structures using finite elements is presented. The model uses the typical parameters [...]
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A stabilized mixed implicit Material Point Method for non-linear incompressible solid mechanics
I. Iaconeta, A. Larese, R. Rossi, E. Oñate

Computational Mechanics (2018). Published online

Abstract
In this work a stabilized mixed formulation for the solution of non-linear solid mechanics problems in nearly-incompressible conditions is presented. In order to deal with high material deformation, an implicit Material Point Method is chosen. Such choice allows avoiding the classical limitations of the Finite Element Method, e.g., element tangling and extreme mesh distortion. The proposed mixed formulation, with displacement and pressure as primary variables, is tested through classical benchmarks in solid and geo-mechanics where a Neo-Hookean, a J2 and a Mohr-Coulomb plastic law are employed. Further, the stabilized mixed formulation is compared with a displacement-based formulation to demonstrate how the proposed approach gets better results in terms of accuracy, not only when incompressible materials are simulated, but also in the case of compressible ones.
Abstract
In this work a stabilized mixed formulation for the solution of non-linear solid mechanics problems in nearly-incompressible conditions is presented. In order to deal with [...]
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A new formulation for air-blast fluid–structure interaction using an immersed approach. Part I: basic methodology and FEM-based simulations
Y. Bazilevs, K. Kamran, G. Moutsanidis, D. Benson, E. Oñate

Computational Mechanics (2017). Vol. 60 (1), pp. 83-100

Abstract
In this two-part paper we begin the development of a new class of methods for modeling fluid–structure interaction (FSI) phenomena for air blast. We aim to develop accurate, robust, and practical computational methodology, which is capable of modeling the dynamics of air blast coupled with the structure response, where the latter involves large, inelastic deformations and disintegration into fragments. An immersed approach is adopted, which leads to an a-priori monolithic FSI formulation with intrinsic contact detection between solid objects, and without formal restrictions on the solid motions. In Part I of this paper, the core air-blast FSI methodology suitable for a variety of discretizations is presented and tested using standard finite elements. Part II of this paper focuses on a particular instantiation of the proposed framework, which couples isogeometric analysis (IGA) based on non-uniform rational B-splines and a reproducing-kernel particle method (RKPM), which is a Meshfree technique. The combination of IGA and RKPM is felt to be particularly attractive for the problem class of interest due to the higher-order accuracy and smoothness of both discretizations, and relative simplicity of RKPM in handling fragmentation scenarios. A collection of mostly 2D numerical examples is presented in each of the parts to illustrate the good performance of the proposed air-blast FSI framework.
Abstract
In this two-part paper we begin the development of a new class of methods for modeling fluid–structure interaction (FSI) phenomena for air blast. We aim to develop accurate, [...]
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A-posteriori error estimation for the finite point method with applications to compressible flow
E. Ortega, R. Flores, E. Oñate, S. Idelsohn

Computational Mechanics (2017). Vol. 60 (2), pp. 219-233

Abstract
An a-posteriori error estimate with application to inviscid compressible flow problems is presented. The estimate is a surrogate measure of the discretization error, obtained from an approximation to the truncation terms of the governing equations. This approximation is calculated from the discrete nodal differential residuals using a reconstructed solution field on a modified stencil of points. Both the error estimation methodology and the flow solution scheme are implemented using the Finite Point Method, a meshless technique enabling higher-order approximations and reconstruction procedures on general unstructured discretizations. The performance of the proposed error indicator is studied and applications to adaptive grid refinement are presented.
Abstract
An a-posteriori error estimate with application to inviscid compressible flow problems is presented. The estimate is a surrogate measure of the discretization error, obtained [...]
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Numerically stable formulas for a particle-based explicit exponential integrator
P. Nadukandi, E. Oñate

Computational Mechanics (2015). Vol. 55 (5), pp. 903-920

Abstract
Numerically stable formulas are presented for the closed-form analytical solution of the X-IVAS scheme in 3D. This scheme is a state-of-the-art particle-based explicit exponential integrator developed for the particle finite element method. Algebraically, this scheme involves two steps: (1) the solution of tangent curves for piecewise linear vector fields defined on simplicial meshes and (2) the solution of line integrals of piecewise linear vector-valued functions along these tangent curves. Hence, the stable formulas presented here have general applicability, e.g. exact integration of trajectories in particle-based (Lagrangian-type) methods, flow visualization and computer graphics. The Newton form of the polynomial interpolation definition is used to express exponential functions of matrices which appear in the analytical solution of the X-IVAS scheme. The divided difference coefficients in these expressions are defined in a piecewise manner, i.e. in a prescribed neighbourhood of removable singularities their series approximations are computed. An optimal series approximation of divided differences is presented which plays a critical role in this methodology. At least ten significant decimal digits in the formula computations are guaranteed to be exact using double-precision floating-point arithmetic. The worst case scenarios occur in the neighbourhood of removable singularities found in fourth-order divided differences of the exponential function.
Abstract
Numerically stable formulas are presented for the closed-form analytical solution of the X-IVAS scheme in 3D. This scheme is a state-of-the-art particle-based explicit exponential [...]
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Determining the micro film of hexyl alcohol in laminar condition on a rotating drum
C. Trang

Rev. int. métodos numér. cálc. diseño ing. (2019). Vol. 35, (2), 28

Abstract
In this research, the free surface of micro film of hexyl alcohol on a partially submerged rotating drum has been predicted using CFD (computational fluid dynamics) and compared with experimental data and analytical solution. The trend of has been found very comparable with experimental and analytical solution. A Matlab code was used to model the flow and film dynamics. Computationally it was an unsteady state problem and semi-steady state was achieved. No surfactant was present on the surface. The speed of the moving rotating drum was set a ''rpm''. With the increase of rotating drum, the minimum film thickness increases with ''rpm'' (for \alpha _o = 47^{0} and for \alpha _o = 58^{0}).
Abstract
In this research, the free surface of micro film of hexyl alcohol on a partially submerged rotating drum has been predicted using CFD (computational fluid dynamics) and compared [...]
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Numerical analysis of particulate flows with the finite element method
G. Casas, E. Oñate, R. Rossi

Monograph CIMNE (2018). M181

Abstract
In this work we study the numerical simulation of particle-laden fluids, with an emphasis on Newtonian fluids and spherical, rigid particles. Our general strategy consists in using the discrete element method (DEM) to model the particles and the finite element method (FEM) to discretize the continuous phase, such that the fluid is not resolved around the particles, but rather averaged over them. The effect of the particles on the fluid is taken into account by averaging (filtering) their individual volumes and particle-fluid interaction forces. In the first part of the work we study the Maxey–Riley equation of motion for an isolated particle in a nonuniform flow; the equation used to calculate the trajectory of the DEM particles. In particular, we perform a detailed theoretical study of its range of applicability, reviewing the initial effects of breaking its fundamental hypotheses, such as small Reynolds number, sphericity of the particle, isolation etc. The output of this study is a set of tables containing order-of-magnitude inequalities to assess the validity of the method in practice. The second part of the work deals with the numerical discretization of the MRE and, in particular, the study of different techniques for the treatment of the history-dependent term, which is difficult to calculate efficiently. We provide improvements on an existing method, proposed by van Hinsberg et al. (2011), and demonstrate its accuracy and efficiency in a sequence of tests of increasing complexity. In the final part of the work we give three application examples representative of different regimes that may be encountered in the industry, demonstrating the versatility of our numerical tool. For that, we describe necessary generalizations to the MRE to cover problems outside its range of applicability. Furthermore, we give a detailed account of the stabilized FEM algorithm used to discretize the fluid phase and compare several derivative recovery tools necessary to calculate some of the interphase coupling terms. Finally, we generalize the algorithm to include the backward-coupling effects according to the theory of multicomponent continua, allowing the code to deal with arbitrarily dense flow regimes.
Abstract
In this work we study the numerical simulation of particle-laden fluids, with an emphasis on Newtonian fluids and spherical, rigid particles. Our general strategy consists [...]
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Application of optimization techniques to the determination of modal parameters in civil structures by the identification method
L. VILLA GARCIA

Rev. int. métodos numér. cálc. diseño ing. (2019). Vol. 35, (3), 45

Abstract
In the present paper, the application of optimization techniques –via FRF– is developed for determining modal parameters by means of the identification method that are exclusively limited to: systems with viscous damping, low levels of damping, and methods that work within the frequency domain. Decomposition techniques are proposed for working with complex magnitudes that allow the real and imaginary parts to be treated separately (which can, in this way, be implemented in commercial optimization programs), even in matrix product operations. The influence of high and low modes is rigorously taken into consideration via the selfsame optimization algorithm. To illustrate this work we have analyzed a structure unique in its slenderness, La Cartuja Bridge (Seville, Spain), which also constitutes a very light structure with very little damping. Its design contributed in its day a new structural framework of complicated geometries through the use of a new material: high yield strength steel.
Abstract
In the present paper, the application of optimization techniques –via FRF– is developed for determining modal parameters by means of the identification method [...]
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Comparison of Wind Loads on Flat and Gabled Roofs calculated with the Colombian Building Code and Numerical Results using CFD
M. OSORIO, L. Cordoba Florez, A. Cruz, J. Marulanda, P. Thomson

Rev. int. métodos numér. cálc. diseño ing. (2019). Vol. 35, (2), 29

Abstract
The Colombian building code, NSR-10, specifies three methods for estimating wind loads on structures: a) a Simplified Method, b) an Analytical Method and c) Wind Tunnel Testing. The first two of these methods are widely used by structural engineers in Colombia, as wind tunnel testing is comparatively expensive and time consuming, and only mandatory in special cases. Although the Simplified Method is only valid for buildings with regular shaped roofs and overall heights less than 18 m, the Analytical Method can be used for any regular building, regardless of the height. However, when these two methods are used to estimate wind loads for buildings with heights less than 18 m, they often produce very different results and, at times, contradictory values. In this study, Computational Fluids Dynamic (CFD) analyses were performed on flat and gabled roofed building models in order to compare the pressures on the roofs with those calculated using the standard design methods specified by the Colombian building code. The results illustrate the significant differences produced from the Simplified and Analytical methods of the NSR-10 and highlight the need of conducting wind tunnel tests in order to propose a more consistent method for estimating design wind loads in Colombia
Abstract
The Colombian building code, NSR-10, specifies three methods for estimating wind loads on structures: a) a Simplified Method, b) an Analytical Method and c) Wind Tunnel Testing. [...]
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Experimental and numerical fracture tests in concrete. Towards the Virtual Laboratory
F. Zarate, A. Gomez, E. Oñate

Rev. int. métodos numér. cálc. diseño ing. (2019). Vol. 35, (1), 14

Abstract
This paper describes a computation methodology to evaluate the ultimate strength and fracture of concrete samples and structures and its application to four typical tests of experimental laboratories of strength of materials. The tests results are compared and analysed from the experimental and numerical points of view in order to highlight the need for experimental trials to use the information derived from numerical results and, in turn, to validate that numerical models follow the behaviour and physics that occur in laboratory tests This comparison allows to explain the different mechanisms that occur throughout the experiments.
Abstract
This paper describes a computation methodology to evaluate the ultimate strength and fracture of concrete samples and structures and its application to four typical tests [...]
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Simulation of resistance and deformability of rocks via discrete elements with cemented particles
L. Medina, M. Farias, L. Rasmussen, C. Recarey

Rev. int. métodos numér. cálc. diseño ing. (2019). Vol. 35, (1), 18

Abstract
The Discrete Element Method (DEM) appears as one of the most attractive methods for understanding general geotechnical problems and specifically the behavior of rocks due to their unique advantages in dealing with fracturing processes. In this work, unconfined compression and indirect tensile tests were performed for a magmatic rock, known as Lac du Bonnet granite, based on a discrete approach using DEM and a specific contact and cementation model between the particles. Concluding, a parametric analysis of the influence of Young's modulus on some macroscopic properties of the rock’s numerical model was carried out, with the objective of generating contributions as to the understanding of the deformability and strength behavior of hard rocks.
Abstract
The Discrete Element Method (DEM) appears as one of the most attractive methods for understanding general geotechnical problems and specifically the behavior of rocks due [...]
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Comparative Analysis of Slender Columns by Approximate Methods
L. ARAUJO

Análise comparativa dos Métodos Aproximados de Dimensionamento de Pilares Esbeltos de Concreto (2018). ARAUJO, L, J.; Dos Santos ; BARBOSA, W. C. S. . ANÁLISE COMPARATIVA DOS MÉTODOS APROXIMADOS DE DIMENSIONAMENTO DE PILARES ESBELTOS DE CONCRETO. In: 60º Congresso Brasileiro do Concreto, 2018, Foz do Iguaçu. 60º Congresso Brasileiro do Concreto, 2018.

Abstract
The present work seeks to analyze the simplified procedures described in ABNT NBR 6118: 2014 for the design of slender columns of reinforced concrete. The standard presents the "Standard abutment method with approximate curvature" and "Standard abutment method with rough stiffness", which is intended for columns with slenderness> 90. The comparative studies of these methods found in the literature have divergent conclusions when it comes to choosing which method best fits the experimental results. Also discussed are proposals for improvements to methods for simplifying the sizing process. Finally, the authors present their conclusions about the methods studied.
Abstract
The present work seeks to analyze the simplified procedures described in ABNT NBR 6118: 2014 for the design of slender columns of reinforced concrete. The standard presents [...]
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Mono-objective minimization of operation cost for a microgrid with renewable power generation, energy storage and electric vehicles
C. Baron, S. Rivera

Rev. int. métodos numér. cálc. diseño ing. (2019). Vol. 35, (3), 34

Abstract
The term Microgrid refers to a power system in a small scale, made of active elements operating between them, namely renewable and traditional generation, energy storage and controllable charges. Previous studies have evaluated and modelled the operation cost of many elements that make up the Microgrid, in order to identify the correct point of operation. In this study, the researchers evaluated a model of Microgrid with diesel as traditional generator, a park of photovoltaic generation, two wind generators, one battery bank and two aggregators that manage electric vehicles. The objective of this research is to propose an equation capable of describing the operation cost of a Microgrid as a set, taking into account the modelling of the operation cost of photovoltaic energy, wind energy, and energy storage in battery banks and electric vehicles. This equation also seeks to obtain the best possible cost efficiency, i.e., decreasing the operation cost of the Microgrid. For this purpose, the Metauristic method DEEPSO (Differential Evolutionary Particle Swarm Optimization) was used, recognized for its performance for applications in power systems. Through this method, and determinate the conditions of operation of the different elements in the Microgrid. Taking into account all the parameters, the behavior of each one of the elements of the Microgrid in a 24-hour lapse was found and visualized.
Abstract
The term Microgrid refers to a power system in a small scale, made of active elements operating between them, namely renewable and traditional generation, energy storage and [...]
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Optimization Study For The Cross-Section Of A Concrete Gravity Dam: Genetic Algorithm Model And Application.
L. ARAUJO, A. Vieira, D. Gutstein

Rev. int. métodos numér. cálc. diseño ing. (2019). Vol. 35, (3), 35

Abstract
Concrete gravity dams have trapezoidal shape in their cross section and shall guarantee the global stability against acting loads like hydrostatic and uplift pressures through his gravitational actions (self-weight and others). This study focuses on the shape optimization of concrete gravity dams using genetic algorithms. In this case, the dam cross section area is considered as the objective function and the design variables are the geometric parameters of the gravity dam. The optimum cross-section of a concrete gravity dam is achieved by the Genetic Algorithm (GA) through a Matlab routine developed by the author. Sliding, overturning and floating verifications are implemented in the program. In order to assess the efficiency of the proposed methodology for gravity dams optimization, one application is presented adopting the concrete gravity dam of Belo Monte Hydropower Plant (HPP), considering normal loading condition and others assumptions presented.
Abstract
Concrete gravity dams have trapezoidal shape in their cross section and shall guarantee the global stability against acting loads like hydrostatic and uplift pressures through [...]
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Mathematical Formulation and Numerical Validation of Uncertainty Costs for Controllable Loads
S. Vargas, D. Rodriguez, S. Rivera

Rev. int. métodos numér. cálc. diseño ing. (2019). Vol. 35, (1), 16

Abstract
This document presents an analysis in the development of a new mathematical formulation with which it will be possible to determine, through probabilistic approaches, the cost that can be generated if a diversified electricity market existed, in which the demand is able to actively participate. For this, it is considered that the electrical demand in a moment of time has associated a probability distribution and a system that makes it controllable. The cost of uncertainty of demand is mathematically developed by calculating the expected cost of supplying the most convenient demand value for the power system. The validation of the analytical formula is done through the Monte Carlo method, which allows us to compare the penalty costs in the case of underestimating or overestimating the demand for electrical energy.
Abstract
This document presents an analysis in the development of a new mathematical formulation with which it will be possible to determine, through probabilistic approaches, the [...]
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CROSS-SECTION OPTIMIZATION OF CONCRETE GRAVITY DAMS USING GENETIC ALGORITHMS
L. ARAUJO

CROSS-SECTION OPTIMIZATION OF CONCRETE GRAVITY DAMS USING GENETIC ALGORITHMS (2017). XXXVIII Ibero-Latin American Congress on Computational Methods in Engineering

Abstract
Concrete gravity dams are the most commonly used hydraulic structures in engineering, for the designer these structures, the overall stability (external forces) must be guaranteed as well as the internal stresses that element is subjected to. The scaling mechanisms these structures are presented in the manual Critérios de Projeto Civil de Usinas Hidroelétricas (2003) from Eletrobras, which is strongly influenced by the U.S. Bureau of Reclamation (1976). After an analysis of the proposed design forms, it was observed a tendency to oversize these structures, in order to reduce this oversizing and to obtain slender forms of dam, the present work brings an optimization study for the cross sections of concrete gravity dams, this optimization will be made by means of routines used in Matlab software, the genetic algorithm technique will be used to reduce the cross-section of this type of dam and consequently reduce the volume of concrete used in its construction.
Abstract
Concrete gravity dams are the most commonly used hydraulic structures in engineering, for the designer these structures, the overall stability (external forces) must be guaranteed [...]
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Efficient combined SSIM- and landmark-driven image registration in a variational framework
J. Larrey-Ruiz, J. Morales-Sánchez, L. Larrey-Ruiz

Rev. int. métodos numér. cálc. diseño ing. (2019). Vol. 35, (1), 27

Abstract
Image registration methods are used to establish geometrical correspondences between different datasets. Various characteristics of image data can be exploited to drive image registration algorithms. Thus, the currently available schemes can be roughly divided into two classes: intensity-based and feature-based registration schemes. In this paper, we present a mathematical framework, based on the calculus of variations, for combining these two classes in order to benefit from the advantages of both strategies. The goal is to obtain a registration algorithm which achieves a good matching of datasets near landmark locations but also away from them (by matching the corresponding intensities). The proposed approach includes the novel formulation of a disparity term which simultaneously takes into account the structural similarity index (a similarity measure which considers spatial dependencies in the images) and the location of outstanding points. Since the iteration which results of the variational formulation is translated into the frequency domain, the implementation of the proposed algorithm offers a good speed-performance trade-off when compared to other state-of-the-art image registration implementations. Experimental results show the advantages, in the medical setting, of the combined SSIM- and landmark-based approach over well-established registration techniques which use either landmark or intensity information alone. In particular, the registration of triple-phase 3D computed tomographies of the liver under injection of a contrast agent has been chosen for such a comparison. The datasets are acquired at different times depending on the arrival time of the contrast agent in arteries, portal and hepatic veins, so they have to be registered in order to show the liver structures acquired at each phase in a common framework. These multi-phase studies provide tumor enhancement on the arterial and portal venous phases that support differential diagnosis of lesions in the liver.
Abstract
Image registration methods are used to establish geometrical correspondences between different datasets. Various characteristics of image data can be exploited to drive image [...]
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Análisis del comportamiento del contrato de distribución de ingresos en una cadena de abastecimiento frutícola
D. Peña Orozco, S. Agudelo, L. Rivera

Rev. int. métodos numér. cálc. diseño ing. (2019). Vol. 35, (2), 31

Abstract
Supply chains are systems characterized by inter-organizational and inter-functional relationships where the markets dynamics and lack of will towards collaborative relationships, lead to each member attempting to maximize their individual performance, generating inefficient global results. To address this problem, it is necessary to adopt appropriate coordination mechanisms to improve the global performance of the decentralized supply chain [10]. Among the coordination mechanisms are information technologies, information exchange and data, joint decision-making and supply contracts [2]. Among the types of contracts, the shared revenue is highlighted, which in addition to promoting coordination in the chain, is concerned with better distribution of income between its echelons [6] by modifying two values to be defined, the wholesale price and income distribution coefficient. In this paper, a mathematical model that represents the revenue sharing contract that attempt to maximize the performance of the supply chain is developed. Finally, a case study in a fruit supply chain composed by three echelons is formulated and the comparative economic results between the current scenario and the scenario using the revenue sharing contract as a coordination mechanism are shown.
Abstract
Supply chains are systems characterized by inter-organizational and inter-functional relationships where the markets dynamics and lack of will towards collaborative relationships, [...]
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Estimation of the transverse sway motion of a biped robot during the march
R. Portillo Vélez, L. Marín-Urias, J. Vazquez-Santacruz, A. Miguelena, A. Marin-Hernandez

Rev. int. métodos numér. cálc. diseño ing. (2019). Vol. 35, (1), 25

Abstract
Due to the balancing generated by the natural dynamics and disturbances during the march of a biped robot, it is difficult to predict its position at a certain moment along the same, thus complicating the development of tasks like manipulation, cooperation, obstacles, avoidance, servo-visual feedback, among others. In this document, we describe a methodology to predict the sway motion in the transverse plane of a biped robot, given the trajectory of a fixed point in its mechanical structure. It is considered the study of two mathematical models to approximate the rolling movement of the robot: approximation by means of a sinusoidal function and approximation by Fourier series. In both cases, it is necessary to know the parameters involved in each mathematical model, so three parametric approximation techniques are implemented: least squares indentification and algebraic identification for the case of the sinusoidal approach, and the calculation of coefficients for the case of the Fourier series. To validate the methodology, real-time monitoring of a biped robot is carried out since the trajectory of the point of interest is affected by various factors such as friction, inclination and imperfections of the surface, the state of conservation of the robot, among others. From different experiments, a quantitative comparison between the different approaches is developed to verify the one that best reproduces the dynamis of the robot's sway.
Abstract
Due to the balancing generated by the natural dynamics and disturbances during the march of a biped robot, it is difficult to predict its position at a certain moment along [...]
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Experimental evaluation of correlations used to calculate friction factor for turbulent flow in cylindrical pipes
A. Olivares, R. Guerra, M. Alfaro, E. Notte-cuello, L. Puentes

Rev. int. métodos numér. cálc. diseño ing. (2019). Vol. 35, (1), 15

Abstract
The hydraulic systems that distribute water to users have an important role in their quality of life. For this reason, the precise determination of the friction factor in pipes is of great importance in the design of water distribution networks because it directly influences the calculation of pressure drop (head losses) in hydraulic systems. The objective of the present work was to evaluate in an experimental manner different correlations that describe, in an explicit form, the friction factor in a pipe under turbulent flow and the implicit Colebrook-White correlation. This was done by comparing the numerical values predicted by the correlations in regard to the experimental value, finding that the Colebrook-White correlation predicts the friction factor with the lowest error percentage among the 27 correlations studied. For the solution of the Colebrook-White equation the Newton-Raphson method was used, given that it presents a recurrent structure that can be taken to algorithms and quickly solved by computer programs. In this work, a tool was developed in the C ++ programming language to solve the Colebrook-White equation.
Abstract
The hydraulic systems that distribute water to users have an important role in their quality of life. For this reason, the precise determination of the friction factor in [...]
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Approximation of the scalar convection-diffusion-reaction equation with stabilized finite element formulations of high order
A. Villota, R. Codina

Rev. int. métodos numér. cálc. diseño ing. (2019). Vol. 35, (1), 6

Abstract
In this paper we present stabilized finite element formulations to solve the scalar convection-diffusion-reaction equation in the case of small diffusion. On the one hand, we summarize the application of the ASGS and OSS formulations based on the concept of variational multiscale methods. On the other hand, we discuss aspects of the use of high order elements, focusing our numerical experiments on quadratic, cubic and fourth order elements. Likewise, the application of the OSS method requires the introduction of a projection, for which we introduce a modification of the fourth order simplicial element with an associated numerical integration rule.
Abstract
In this paper we present stabilized finite element formulations to solve the scalar convection-diffusion-reaction equation in the case of small diffusion. On the one hand, [...]
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Efficiency Maximization of a Jet Pump for an Hydraulic Artificial Lift System
R. Portillo Vélez, J. Vásquez-Santacruz, L. Marín-Urías, A. Vargas, P. García-Ramírez, J. Morales-de-la-Mora, A. Vite-Morales, E. Gutierrez-Domínguez

Rev. int. métodos numér. cálc. diseño ing. (2019). Vol. 35, (1), 12

Abstract
This work presents a simpler numerical design method for efficiency maximization of an Hydraulic Jet Pump (HJP) for oil-well extraction process, considering its hydraulic and geometric parameters. The design process consists in setting and solving a constrained non-linear optimization problem by taking into account the hydraulic model of the HJP in terms four design variables: throat area, nozzle area, injection flow, and injection pressure to the oil-well. The objective function of this case aims to maximize the HJP's efficiency avoiding to approach cavitation condition as well fulfilling technical constraints. A numerical technique, Differential Evolution Algorithm (DEA), has been implemented to solve the optimization problem. The proposed methodology leads to a solution set by considering only commercial geometries and feasible operating conditions for the HJP, which facilitates its practical implementation. A set of ten oil-wells with land production data, operating in the southeaster of Mexico, is used to compare and validate several Jet pump designs, i. e., through comparison with actual oil-well's operation condition.
Abstract
This work presents a simpler numerical design method for efficiency maximization of an Hydraulic Jet Pump (HJP) for oil-well extraction process, considering its hydraulic [...]
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Analysis of an experimental composited joint of rc column and beams-steel column for frames using correlation of digital images
N. López, R. Ugel, R. Herrera

Gaceta Técnica (2019). Vol. 19, 4

Abstract
This research presents the behavior of a real scale experimental column-beam joint formed by three reinforced concrete elements, 1 column and 2 beams, attached to a structural steel column in the upper level is studied. The specimen in question was subjected to the action of cyclic loads in a single direction, in a pseudostatic test for 5000 s, in order to observe which element of the specimen failed and which the failure mode was. The investigation was based on the use of digital images taken throughout the test, during the loading and unloading cycles, each photo being analyzed with the CORRELI-Q4 subroutine, in order to visualize the places where cracking occurs in the concrete. The use of the application allowed to reveal how cracking in the reinforced concrete occurred during the test, and that the column of reinforced concrete was the one that was most affected by cracking, with cracks just below the concrete beams.
Abstract
This research presents the behavior of a real scale experimental column-beam joint formed by three reinforced concrete elements, 1 column and 2 beams, attached to a structural [...]
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A geometric description of Discrete Exterior Calculus for general triangulations
R. Herrera, S. Botello, H. Esqueda, M. Moreles

Rev. int. métodos numér. cálc. diseño ing. (2019). Vol. 35, (1), 2

Abstract
We revisit the theory of Discrete Exterior Calculus (DEC) in 2D for general triangulations, relying only on Vector Calculus and Matrix Algebra. We present DEC numerical solutions of the Poisson equation and compare them against those found using the Finite Element Method with linear elements (FEML).
Abstract
We revisit the theory of Discrete Exterior Calculus (DEC) in 2D for general triangulations, relying only on Vector Calculus and Matrix Algebra. We present DEC numerical solutions [...]
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A methodology for the design of dam spillways with wedge shaped blocks based on numerical modeling
J. San Mauro, M. Toledo, F. Salazar, F. Caballero

Rev. int. métodos numér. cálc. diseño ing. (2019). Vol. 35, (1), 3

Abstract
Wedge shaped blocks spillways are an innovative solution that allows spilling over the downstream shoulder of earth and rock-fill dams in a safe way. However, they have been barely used as main spillway due to the lack of practical design criteria. An innovative procedure for computer-aided design of wedge shaped blocks spillways is presented in this paper. It includes the design of the drainage and supporting layer considering its seepage capacity and stability. The leakage flow through the joints between blocks is estimated by means of a numerical model calibrated and validated from experimental results. Stability against sliding of the downstream shoulder or the drainage layer is ensured, considering the properties of the granular material selected by the designer and non-linear resistance laws. The procedure will also suggest the shape of a toe protection.
Abstract
Wedge shaped blocks spillways are an innovative solution that allows spilling over the downstream shoulder of earth and rock-fill dams in a safe way. However, they have been [...]
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The effect of the mesh refinement on a multiscale domain decomposition method for the non-linear simulation of composite structures
J. Fernandez, K. Saavedra, J. Hinojosa, P. Flores

Rev. int. métodos numér. cálc. diseño ing. (2019). Vol. 35, (1), 24

Abstract
This article is focused on the study of a micro-macro LaTIn based Domain Decomposition Method (LaTIn-DDM) for the prediction of the nonlinear behavior of slender composite structures subjected to bending, buckling and delamination. Previous studies have shown that an adequate selection of the iterative parameters (search directions and macroscopic space) allow to improve the convergence rate and ensure scalability (i.e. number of iterations is independent of the number of subdomains) of the iterative schema. To obtain precise solutions, only the size reduction of the subdomains' discretization has been addressed (h-refinement), disregarding the option of increasing the polynomial degree of the finite elements (p-refinement) and ignoring their underlying effects on the information's transmission through the interfaces between subdomains. In this work and using linear and quadratic finite elements, h and p refinements on the subdomains and local h-refinement only along the edges of the subdomains were investigated. It is conclude that the p-refinement in the whole subdomain not only enables to reach more exact solutions than using global or local h-refinement, but also the convergence rate is improved. These enhancements allow more complex simulations but using less degrees of freedom and less calculation time, even up to 97% faster.
Abstract
This article is focused on the study of a micro-macro LaTIn based Domain Decomposition Method (LaTIn-DDM) for the prediction of the nonlinear behavior of slender composite [...]
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Dynamic Analysis of Hypar Membrane Structures Subjected to Seismic Excitations
J. Valdes-Vazquez, A. García-Soto, A. Hernández-Martínez

Rev. int. métodos numér. cálc. diseño ing. (2019). Vol. 35, (1), 11

Abstract
The seismic response of tensile membrane structures (TMS) is investigated. To the authors knowledge, this is the first study on TMSs subjected to a seismic record reported in the literature. A type of membrane structures usually considered as a reference in other works are employed in the present study. The selected hyperbolic-paraboloid fabric structures, also referred as hypar TMSs, are subjected to an earthquake accelerogram from a relatively large earthquake recorded at Norcia, Italy. To obtain the TMSs seismic re- sponse, a finite element formulation reported in a previous study, and which accounts for wrinkling phenomena, orthotropic material modeling, and geometrical nonlinearity, is employed. The analyses are performed in two stages; first for the prestressed case and then the seismic loading is added. It is found that the seismic response of TMSs should not be disregarded by designers beforehand, since important increments in the dynamic response of the displacements produce an incremet of around 9% for stresses. However, a very important increment of around 80% for support reaction forces is computed, when compared with the static case. It is also found that the orientation of the frame-supporting structure has a significant impact on the computed seismic reactions.
Abstract
The seismic response of tensile membrane structures (TMS) is investigated. To the authors knowledge, this is the first study on TMSs subjected to a seismic record reported [...]
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On the robustness of the multigrid method combining ILU and Partial Weight applied in an orthotropic diffusion problem
G. Vassoler Rutz, M. Augusto Villela Pinto, S. de Fátima Tomazzoni Gonçalves

Rev. int. métodos numér. cálc. diseño ing. (2019). Vol. 35, (1), 23

Abstract
This paper proposes an efficient and robust algorithm for solving a physical orthotropy problem. The algorithm is based on choosing the most efficient restriction operator and on an incomplete LU decomposition suited for each orthotropy direction. Local Fourier Analysis (LFA) is carried out in order to increase the efficiency of the multigrid method. Pure diffusion with orthotropy aligned to the coordinate axis x is the model considered. Equations are discretized by Finite Difference Method with uniform grid and second-order numerical scheme. Problems are solved with geometric multigrid method, correction scheme, V-cycle and standard coarsening ratio. The asymptotic convergence factor is calculated for different multigrid components, such as restriction operators, prolongation operators and solvers. Based on the optimum components obtained by LFA, we carried out experiments to analyze the complexity and computational cost of the algorithm proposed. The main conclusion is that the methodology proposed is efficient for the resolution of problems with strong orthotropy.
Abstract
This paper proposes an efficient and robust algorithm for solving a physical orthotropy problem. The algorithm is based on choosing the most efficient restriction operator [...]
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Modified simulated annealing algorithm for optimal design of steel structures
C. Millan, J. Filho

Rev. int. métodos numér. cálc. diseño ing. (2019). Vol. 35, (1), 26

Abstract
Structural optimization aims to design structures under certain constraints to achieve better behavior and have a proper manufacturing cost. This type of optimization corresponds to highly non-linear and non-convex problems including several local optima. Therefore, to solve such problems effectively, designers need to use adequate optimization methods which can make a good balance between the computational cost and the quality of solutions. In this paper the modified simulated annealing algorithm (MSAA) is employed to solve optimal design of steel structures. MSSA is a newly improved version of the simulated annealing (SA) algorithm with three modiﬁcations: preliminary exploration, search step and a new probability of acceptance. The performance, robustness and applicability of the MSAA are demonstrated through six structural optimization problems. Obtained results in all considered examples indicate that the MSAA is superior to several other methods in existing literature in terms of the quality of solution and convergence speed.
Abstract
Structural optimization aims to design structures under certain constraints to achieve better behavior and have a proper manufacturing cost. This type of optimization corresponds [...]
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Optimum design of composite twin-girder road bridges
J. Baraibar, E. Baraibar

Rev. int. métodos numér. cálc. diseño ing. (2019). Vol. 35, (3), 41

Abstract
Composite structures have not been able to compete in Spain with more conventional prestressed concrete bridges in the lower range of medium spans (30 - 90 m.). In this context, twin-girder sections are revealed as a more competent typology because of its sobriety, ease of construction and good structural performance. At present the optimal character of the designs in structural projects is rarely challenged. The present study undertakes an in-depth analysis of the twin-girder section, involving a complete optimisation for the deck. To this end a specific 2D grillage model has been developed, integrating the composite and evolutive character of twin-girder decks, as well as the instability phenomena inherent to thin-walled structures. Several conclusions are drawn after a parametric calculation using this model, regarding the optimum dimensions of all the variables that define the twin-girder section. These conclusions crystallise in a series of formulas that can be used as a design guide.
Abstract
Composite structures have not been able to compete in Spain with more conventional prestressed concrete bridges in the lower range of medium spans (30 - 90 m.). In this context, [...]
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Dynamic analysis in the domain of frequency by the method of the harmonic balance
R. Zaltron, F. Neves

Rev. int. métodos numér. cálc. diseño ing. (2019). Vol. 35, (1), 10

Abstract
The analysis of structures in the frequency domain has been gaining ground in the last decades, first, because of the computational development and strategies to evaluate the Discrete Fourier Transform more efficiently. The advantages of evaluating the frequency response are that there is no need to know the initial conditions, and the response to systems with frequency-dependent properties can be evaluated more accurately, eg, soil-structure interaction. This work aims to evaluate the dynamic response of a discrete structural system in the frequency domain through the resonance curves using the Harmonic Balance Method HBM. The response is evaluated in the permanent phase for actions and / or harmonic loads for systems with proportional and non-proportional viscous damping. The properties of the system, such as mass and rigidity, are taken as constants. For the models developed and analyzed in this study are presented the respective spectra of frequency response and history of displacement in time through the HBM. The system responses obtained through the HBM are compared with two other methods also based on the frequency domain (ImFT and PseudoForces), allowing to evaluate the amplitudes and critical frequencies of the system.
Abstract
The analysis of structures in the frequency domain has been gaining ground in the last decades, first, because of the computational development and strategies to evaluate [...]
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A rapid aeroelasticity optimization method based on the stiffness characteristics
Z. Yuan, S. Huo, J. Ren

Rev. int. métodos numér. cálc. diseño ing. (2019). Vol. 35, (1), 4

Abstract
A rapid aeroelasticity optimization method based on the stiffness characteristics was proposed in the present study. Large time expense in static aeroelasticity analysis based on traditional time domain aeroelasticity method is solved. Elastic axis location and torsional stiffness are discussed firstly. Both torsional stiffness and the distance between stiffness center and aerodynamic center have a direct impact on divergent velocity. The divergent velocity can be adjusted by changing the correlative structural parameters. The relation between structural parameters and divergent velocity is introduced to aeroelasticity optimization design as a constraint condition. After optimization, the structural and aerodynamic characteristics have a large improvement while satisfying the constraint conditions. The optimization method can be well used in high aspect ratio wing and has great computational efficiency.
Abstract
A rapid aeroelasticity optimization method based on the stiffness characteristics was proposed in the present study. Large time expense in static aeroelasticity analysis based [...]
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Interval-based Recording of Generated Pseudorandom Numbers
V. Tomašević, M. Tomašević, S. Bojanic

Rev. int. métodos numér. cálc. diseño ing. (2019). Vol. 35, (2), 33

Abstract
For some applications that use pseudorandom numbers it is essential to keep the record of numbers generated so far. Such a representative example is cryptanalytic TMTO approach. In order to save the space, instead of straightforward recording of individual numbers generated, an ordered tree-like data structure which tracks the intervals of generated numbers is proposed. For estimating the memory requirements of this structure as a function of pseudorandom numbers range size, an analytical probabilistic model is established and used. This model determines the maximum number of intervals during recording which corresponds to the tree size. The result obtained from analytical model is fully validated experimentally by means of simulation for a wide spectrum of range sizes.
Abstract
For some applications that use pseudorandom numbers it is essential to keep the record of numbers generated so far. Such a representative example is cryptanalytic TMTO approach. [...]
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Structural health monitoring by combining machine learning and dimensionality reduction techniques
G. Quaranta, E. Lopez, E. Abisset-Chavanne, J. Duval, A. Huerta, F. Chinesta

Rev. int. métodos numér. cálc. diseño ing. (2019). Vol. 35, (1), 20

Abstract
Structural Health Monitoring is of major interest in many areas of structural mechanics. This paper presents a new approach based on the combination of dimensionality reduction and data-mining techniques able to differentiate damaged and undamaged regions in a given structure. Indeed, existence, severity (size) and location of damage can be efficiently estimated from collected data at some locations from which the fields of interest are completed before the analysis based on machine learning and dimensionality reduction techniques proceed.
Abstract
Structural Health Monitoring is of major interest in many areas of structural mechanics. This paper presents a new approach based on the combination of dimensionality reduction [...]
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Design and manufacture of a customised temporomandibular prosthesis
C. Miguel, J. Hernández-Gómez, G. Urriolagoitia-Sosa, B. Romero-Ángeles, L. Martínez-Sáez

Rev. int. métodos numér. cálc. diseño ing. (2019). Vol. 35, (1), 22

Abstract
In this work, design, manufacture and surgical success of a personalised temporomandibular prosthesis is featured. A fused deposition modelling technique and Die forging process constitute the methodology used in a patient who had an amputation in the upper third branch of the mandible, without considering the joint capsule. The implant was designed using a processed resection image of a computational tomography and using the methodology of Özkaya and Nordin. The jaw operating conditions were simulated by the finite element method (FEM). The main considered factors were the morphological geometry of the patient, implant fixation in the first third of the branch, implant fixation on the chin, dental post for placement of the teeth, and the form of the sub-lingual fossa weight optimisation. Special consideration was to preserve the patients facial aesthetics.
Abstract
In this work, design, manufacture and surgical success of a personalised temporomandibular prosthesis is featured. A fused deposition modelling technique and Die forging process [...]
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Damping performance of viscoelastic material applied to blades
F. Wang, Z. Wei, B. Xu

Rev. int. métodos numér. cálc. diseño ing. (2019). Vol. 35, (1), 9

Abstract
'''High-frequency vibration can result in failure of the working blades. So suppressing vibration failure of blades becomes more and more important. Damping performance of viscoelastic block on blades is researched based on principle of finite element method, contact theory of elastic body and the solving equations of natural frequency. Modal and harmonic response is analyzed to obtain natural frequency, vibration displacement and stress, in which different finite element models of blade are established. Effects of different adding position and thickness of viscoelastic block on damping performance are analyzed. Elastic modulus and loss factor of viscoelastic material is also changed to study their influence on damping performance. The results show that viscoelastic block applied to blades has excellent performance in reducing blade vibration. When viscoelastic block is added to mortise side, the damping performance of blade is the best. In addition, thickness of viscoelastic block and parameters of viscoelastic material have a significant effect on vibration reduction of blade. '''Key words''': Viscoelastic damping material, blades, vibration reduction, modal analysis, harmonic response Corresponding author. E-mail: [mailto:fswang@nwpu.edu.cn fswang@nwpu.edu.cn] (Fusheng Wang)
Abstract
'''High-frequency vibration can result in failure of the working blades. So suppressing vibration failure of blades becomes more and more important. Damping performance [...]
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Assessment of methods of identification of dynamic properties based on measured seismic response of a building
P. Alcaíno, H. Santa-María

Rev. int. métodos numér. cálc. diseño ing. (2019). Vol. 35, (1), 7

Abstract
The structural monitoring, which is becoming increasingly common, makes it necessary to choose one or more methods of processing and analyzing the obtained data. This choice is key to meeting the objectives of this monitoring. Considering that there are many methods with different capacities and requirements, this choice is a complex problem. This paper presents a methodology for the assessment and selection of methods for the identification of dynamic response properties of buildings using vibration monitoring. In this work, well-known methods based on time domain analysis (subspace-state) and non-parametric methods based on the frequency domain are studied when applied to seismic vibration records for a reinforced concrete building instrumented with a network of tri-axial force-balance accelerometers. For two and a half years, the sensor network has recorded close to 500 sensitive earthquakes. Nonetheless, it only includes those with a magnitude higher than 4.8 (ML or MW) and that occurred between September, 2015 and September, 2016. Using six versions of identification methods, modal response parameters are determined for each of the two main directions of the building, considering different levels of information acquired by the sensor network (floor information). An assessment of the performance of each method is conducted based on the number of identified modal frequencies and damping ratios; their variability (coefficient of variation); and the processing time of each method. As a result and conclusion regarding the use of this methodology, it is not only possible to choose the most convenient method for processing vibration records applied to structural health monitoring (SHM) according to its own objective, but also to progressively improve the design of the sensor network.
Abstract
The structural monitoring, which is becoming increasingly common, makes it necessary to choose one or more methods of processing and analyzing the obtained data. This choice [...]
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Elasto-plastic finite element analysis of reinforced concrete T-shaped column frame joint
Y. Liu, X. Ren, H. Liu

Rev. int. métodos numér. cálc. diseño ing. (2019). Vol. 35, (1), 13

Abstract
By the integral finite element analysis of elasto-plastic constitutive relationship, the process of crack formation and development of the T-shaped frame joint in reinforced concrete and its stress distribution under monotonic and low-cycle repeated loading were studied . The nonlinear constitutive relation of concrete and the failure mechanism of T-shaped column joint were further discussed. The work of this paper provides a reference to the design and construction of T-shaped column joints.
Abstract
By the integral finite element analysis of elasto-plastic constitutive relationship, the process of crack formation and development of the T-shaped frame joint in reinforced [...]
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Structural assessment of gravity dams by means of a semi-discrete approach
F. Peña

Rev. int. métodos numér. cálc. diseño ing. (2019). Vol. 35, (1), 19

Abstract
A new numerical model for the structural assessment of gravity dams by means of a semi-discrete approach is proposed. Gravity dams are massive structures, which their stability depends on the gravity loads applied into the structure. Mainly, its structural assessment is performed by means of a gravity approach. However, this approach is too conservative and mostly does not reflect the real structural behaviour of the dam. In this context, there is the need of models that are simplified enough to allow a simple and fast parametric analyses. The proposed model idealizes the dam as a set of rigid elements, where the damage and the deformation are concentrated in the contact sides between adjacent elements. Thus, the elements are rigid, but the material is considered as deformable. As the proposed model is semi-discrete, it can detect separation or sliding between elements. However, initial contacts do not change during the analyisis and a relative continuity among elements exists, in order to simplify the computational effort. The effective performance of the proposed model is demonstrated by numerical validation and by comparisons with some numerical models presented in the literature.
Abstract
A new numerical model for the structural assessment of gravity dams by means of a semi-discrete approach is proposed. Gravity dams are massive structures, which their stability [...]
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Positioning system for 3D scans inside objects
S. Cano-Rodríguez, J. Gonzalez-Barbosa, F. Ornelas-Rodríguez, J. Hurtado-Ramos, O. Icasio-Hernández

Rev. int. métodos numér. cálc. diseño ing. (2019). Vol. 35, (1), 17

Abstract
In this work we present an active positioning system for 3D scan of interior parts. The design of the proposed system consists of two modules: an active 2D dimensional system and positional system based on active vision. The active 2D dimensional system is able to determine the depth of the 2D dimensional system inside the object to be scanned using several sensors. The main contributions of this work are the characterization of the 2D dimensional system and the development of active light positioning algorithms with emphasis on the modeling and fusion of the sensors. The system can be used as a dimensional system in industrial applications such as the metal mechanical industry, aeronautics industry, medicine, quality control and computer vision.
Abstract
In this work we present an active positioning system for 3D scan of interior parts. The design of the proposed system consists of two modules: an active 2D dimensional system [...]
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Annual distribution of the Sun’s angular positions, study at 21 degrees of latitude
C. Acosta, O. Carvente-Muñoz, F. Peñuñuri-Anguiano, M. Zambrano-Arjona, G. Rivadeneyra-Gutiérrez

Rev. int. métodos numér. cálc. diseño ing. (2019). Vol. 35, (1), 5

Abstract
It is well know that the Sun position, measured over the heart surface is a function of the latitude and the hour of a particular day. Usually, the Sun follows a different path from one day to the next, and this is determined by the azimuth and zenith angles. The analytical calculations for determining the angular position at any time (solar hour) are an overwhelming task. We use the Mathematica® software to write a home code for determining at any time (in intervals of one minute) and latitude, the azimuth and zenith angles of the Sun for every day of the year. In order to show general results of interest, in this work we present the annual distribution of the angular positions and the length of the day (hours of light) for the 21 degrees of latitude. This information could be used for optimizing the orientation of solar panels and collectors and for the design of cheap houses where the walls can be exposed to the minimal solar incidence.
Abstract
It is well know that the Sun position, measured over the heart surface is a function of the latitude and the hour of a particular day. Usually, the Sun follows a different [...]
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Thermal model of a solar concentration cooker: a parameter variation study to estimate thermal properties
M. Gonzalez-Aviles, J. AVILES, H. CAMPUZANO

Rev. int. métodos numér. cálc. diseño ing. (2019). Vol. 35, (1), 21

Abstract
This document describes the development of a thermal model to explain the behavior of a solar concentration cooker. The model is presented in terms of a coupled system consisting of three ordinary, differential non-lineal equations used to calculate average temperatures of the surface of the reflectors, the surface of the container, and the liquid placed inside the container. Numerical results compared to measurements from experimental tests show that good concordance was obtained. A study of variation was conducted using some of the design parameters of the solar cooker to estimate standard cooking power and thermal efficiency. We conclude that the parameter ‘emittance of selective absorbent film’ on the surface of the cooking pot exerts the greatest influence on the thermal properties assessed.
Abstract
This document describes the development of a thermal model to explain the behavior of a solar concentration cooker. The model is presented in terms of a coupled system consisting [...]
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3D printed scaled setup for smoke transport analysis in a subterranean passenger platform
L. Flores-Herrera, R. Rivera-Blas, J. Pérez-Cruz, N. Muñoz-Aguirre, C. Torres-Martínez, M. Carbajal-Romero, R. Vargas-Carmona, M. Funes-Lora

Rev. int. métodos numér. cálc. diseño ing. (2019). Vol. 35, (1), 1

Abstract
In this work, the study of smoke fire transportation inside of a subway passenger platform is presented. The study includes a set of numerical simulations to observe the behavior of the air inside the platform. Two smoke transport simulations using the FDS program are also included. Subsequently, the development of a 3D - 1:100 scale model is described and it was used to perform an experimental observation of the phenomenon. The model was built by using a 3D printer which allowed to include more architectural details of the real scenario. The inclusion of these details allowed to observe qualitative similarity between the results of the simulation and the experimental work. Although there are clear differences between what could happen in a real scenario and what was observed in the scale model, it was identified that the model is an important complement to the simulations. In addition to the simulations, the use of this type of 3D models allows the observation of the phenomenon by different specialists such as firefighters, policeman, medical personnel, etc., in the same place and its intention is to provide a more interactive tool to the observation group, increasing the time devoted to the development of contingency actions and reducing the costs associated with the logistics of a real simulacrum. The model allows to better identify the strengths, opportunities, weaknesses and threats of the contingency procedures developed by the safety and hygiene groups and to make their corresponding adjustments if necessary.
Abstract
In this work, the study of smoke fire transportation inside of a subway passenger platform is presented. The study includes a set of numerical simulations to observe the behavior [...]
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Analysis and design of concrete structures using strut and tie model by FEM: Application in foundation blocks, short consoles, wall beams and rigid shoes
M. LIMA, P. ROCHA, R. SILVEIRA, K. SILVA

Rev. int. métodos numér. cálc. diseño ing. (2019). Vol. 35, (2), 30

Abstract
The present work has as main objective to perform elastic-linear analyzes through a computational program with numerical approach of the strut-and-tie model using a formulation based on the Finite Element Method (FEM). In this model, it is possible to analyze the behavior of structural elements such as foundation blocks, wall beams, short consoles, also represent the values of tensions, deformations and displacements in the region of a beam represented as the Model of cranks developed by MONTOYA et al. [1], besides numerically modeling via FEM a wall beam with a large aperture, developed by SCHLAICH et al. [2]. In order to validate the numerical implementations, the results were compared with numerical modeling performed with the aid of ANSYS software 17 and with normative expressions.
Abstract
The present work has as main objective to perform elastic-linear analyzes through a computational program with numerical approach of the strut-and-tie model using a formulation [...]
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Change of effective properties of concrete by alkali-silica reaction
G. Augusto Pianezzer, L. Gramani, E. Kaviski

Rev. int. métodos numér. cálc. diseño ing. (2019). Vol. 35, (1), 8

Abstract
The present work develops a model of computer simulation of the actual properties of concrete under the action of alkali-silica reaction. Obtains a computational representation from the analysis of the chemical reaction and homogenenization techniques. Alkali-Silica reaction forms a gel that changes the effective properties of concrete and can lead to damage to structures, especially of hydroelectric dams. The model consists of three phases, generation of representative element of concrete, gel formation and dissemination by alkali-silica reaction and homogeneization of the final material. The first stage is the development of representative concrete element that is simulated from the granulometric curve and uses a computacional collision detection algorithm to ellipses. To model the behavior of chemical evolution, it uses a system based on equations of chemical kinetics, known as Guldberg - Waage Law and uses a gel diffusion model developed to mesh of representative element of concrete. To model the variation of the effective properties, it uses homogenization schemes (Reuss method, Voigt Method, Self-Consistent method and Mori-Tanaka method) to provide, thus, elasticity coefficientes of the composite material. The combination of the models allowed to predict the evolution and damage to the material over time and analyze the influence of the volume fraction of agregates in the lifetime of concrete.
Abstract
The present work develops a model of computer simulation of the actual properties of concrete under the action of alkali-silica reaction. Obtains a computational representation [...]
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Contribution to the fluid-structure interaction analysis of ultra-lightweight structures using an embedded approach
D. Baumgärtner, J. Wolf, R. Rossi, R. Wüchner, P. Dadvand

Monograph CIMNE (2015). M152

Abstract
Designing large ultra-lightweight structures within a fluid flow, such as inflatable hangars in an atmospheric environment, requires an analysis of the naturally occurring fluid-structure interaction (FSI). To this end multidisciplinary simulation techniques may be used. The latter, though, have to be capable of dealing with complex shapes and large deformations as well as challenging phenomena like wrinkling or folding of the structure. To overcome such problems the method of embedded domains may be used. In this work we discuss a new solution procedure for FSI analyses based on the method of embedded domains. In doing so, we are in particular answering the questions: How to track the interface in the embedded approach, how does the subsequent solution procedure look like and how does both compare to the well-known Arbitrary Lagrangian-Eulerian (ALE) approach? In this context a level set technique as well as different mapping and mesh-updating strategies are developed and evaluated. Furthermore the solution procedure of a completely embedded FSI analysis is established and tested using different small- and large-scale examples. All results are finally compared to results from an ALE approach. It is shown that the embedded approach offers a powerful and robust alternative in terms of the FSI analysis of ultra-lightweight structures with complex shapes and large deformations. With regard to the solution accuracy, however, clear restrictions are elaborated.
Abstract
Designing large ultra-lightweight structures within a fluid flow, such as inflatable hangars in an atmospheric environment, requires an analysis of the naturally occurring [...]
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