Documents published in 2020 : Scipedia

Statical and dynamical behaviour of thin fibre reinforced composite laminates with different shapes
L. Nallim, S. Oller, R. Grossi

Comput. Methods Appl. Mech. Engrg., (2005). Vol. 194 (17), pp. 1797-1822

Abstract
Based on the classical laminated plate theory, a variational approach for the study of the statical and dynamical behaviour of arbitrary quadrilateral anisotropic plates with various boundary conditions is developed. The analytical formulation uses the Ritz method in conjunction with natural coordinates to express the geometry of general plates in a simple form. The deflection of the plate is approximated by a set of beam characteristic orthogonal polynomials generated using the Gram–Schmidt procedure. The algorithm developed is quite general and can be used to study fibre reinforced composite laminates with symmetric lay-ups, which may have general anisotropy and any combinations of clamped, simply supported and free edge support conditions. Various numerical applications are presented and some results are compared with existing values in the literature to demonstrate the accuracy and flexibility of the present method. New results were also determined for plates with different geometrical shapes, combinations of boundary conditions, several stacking sequences and various angles of fibre orientation.
Abstract
Based on the classical laminated plate theory, a variational approach for the study of the statical and dynamical behaviour of arbitrary quadrilateral anisotropic [...]
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Estudio numérico del comportamiento de los hormigones reforzados con fibras cortas
S. Oller, A. Barbat

Hormigón y Acero (2004). Vol. 55 (232), pp. 113-123

Abstract
En este trabajo se presenta un acercamiento al estudio del comportamiento de los hormigones reforzados con fibras cortas. Se establece una formulación basada en una modificación de la teoría de mezclas clásica para determinar sus parámetros mecánicos a partir de las características de los materiales componentes (hormigón fibras cortas). También se muestran resultados numéricos obtenidos mediante el método de los elementos finitos y se comentan las posibilidades de un método analítico simplificado para el estudio de su comportamiento. El desarrollo del trabajo trata sobre el comportamiento del hormigón reforzado con fibras y las características que justifican su utilización. Se estudia el equilibrio interno y mecanismo de transmisión de tensiones entre el hormigón y las fibras cortas y la formulación general del problema e inserción dentro de la técnica de los elementos finitos. Se hace un breve comentario sobre el tratamiento simplificado del comportamiento de los hormigones reforzados con fibras cortas y se presenta un ejemplo de comprobación.
Abstract
En este trabajo se presenta un acercamiento al estudio del comportamiento de los hormigones reforzados con fibras cortas. Se establece una formulación basada en una [...]
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Definition of a general implicit orthotropic yield criterion
S. Oller, E. Car, J. Lubliner

Comput. Methods Appl. Mech. Engrg., (2003). Vol. 192 (7-8), pp. 895-912

Abstract
The definition of an orthotropic yield criterion presents a serious challenge in the formulation of constitutive models based on such theories as elastoplasticity, viscoplasticity, damage, etc. The need to model the behavior of a real orthotropic material requires the formulation of orthotropic yield criteria, and these may be difficult to obtain. For metals, orthotropic yield functions have been formulated by Hill [Proc. Roy. Soc. Lon. Ser. A 193 (1948) 281; J. Mech. Phys. Solids 38(3) (1990) 200], Barlat [Int. J. Plasticity 5 (1989) 51; 7 (1991) 693], Chu [NUMISHEET 93 (1993) 199] and Dutko et al. [Comput. Methods Appl. Mech. Engrg. 109 (1993) 73], but in many cases these functions do not describe the true behavior of the metal. The situation is worse when one attempts to represent a nonmetal such as a polymer, ceramic or composite. In this paper, we present a general definition of an explicit orthotropic yield criterion together with a general method for defining implicit orthotropic yield functions. The latter formulation is based on the transformed-tensor method, whose principal advantage lies in the possibility of adjusting an arbitrary isotropic yield criterion to the behavior of an anisotropic material. As example we choose the adjustment to the Hill, Hoffman [J. Comp. Materials 1 (1967) 200] and Tsai–Wu [J. Comp. Materials 5 (1971) 58] criteria, but these particular cases serve to establish the methodology for achieving the desired function adjustment for any other well-known criterion or experimental set of data obtained from laboratory.
Abstract
The definition of an orthotropic yield criterion presents a serious challenge in the formulation of constitutive models based on such theories as elastoplasticity, viscoplasticity, [...]
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Life prediction of structures. Numerical study and treatment of structural durability, a brief report
S. Oller, E. Oñate

Temes de Disseny (2002). Vol. 20, pp. 85-99

Abstract
This work is a brief report about the problem of life -or, durability study- of structural materials, undergoing mechanical, thermal and chemical actions. This document is approached from numerical techniques and, it highlights the potential of these types of tools un the study of structures undergoing very complex and coupled phenomena.
Abstract
This work is a brief report about the problem of life -or, durability study- of structural materials, undergoing mechanical, thermal and chemical actions. This document is [...]
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A general framework for continuum damage models. II. Integration algorithms, with applications to the numerical simulation of porous metals
F. Armero, S. Oller

Int. J. Solids and Structures (2000). Vol. 37 (48-50), pp. 7437-7464

Abstract
In this paper, we develop numerical algorithms for the integration of the continuum plastic damage models formulated in the general framework identified in Part I of this work. More specifically, we focus our attention on a particular plastic damage model of porous metals, involving a classical von Mises yield criterion coupled with a pressure dependent damage surface to model the nucleation and growth of voids in the metallic matrix. Unilateral damage leading to a sudden change of stiffness in the material's response due to the closing/opening of these voids is also incorporated through the imposition of the unilateral constraint of a positive void fraction, thus, illustrating the clear physical significance added by this framework in the resulting constitutive models. The proposed integration algorithms fully use the modularity of the identified framework, leading in this way to independent integration algorithms for the elastoplastic part and each damage mechanism. Remarkably, all these individual integration schemes share the same formal structure as the classical return mapping algorithms employed in the numerical integration of elastoplastic models, namely an operator split structure consisting of a trial state and the return map imposing the plastic and damage consistency, respectively. A Newton iterative scheme imposes the equilibrium (equal stresses) among the different mechanisms of the response of the material. This modular structure allows to obtain the closed-form consistent linearization, involving in a simple form the algorithmic consistent tangents corresponding to each independent mechanism, thus resulting in a very modular and efficient computational implementation. The performance of the proposed algorithms is illustrated in several representative numerical simulations.
Abstract
In this paper, we develop numerical algorithms for the integration of the continuum plastic damage models formulated in the general framework identified in Part I of this [...]
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A general framework for continuum damage models. I. Infinitesimal plastic damage models in stress space
F. Armero, S. Oller

Int. J. Solids and Structures (2000). Vol. 37 (48-50), pp. 7409-7436

Abstract
We identify in this paper a general framework for the development of continuum damage models in their fully coupled plastic damage form. The focus of this paper is directed to the general formulation of infinitesimal models defined by yield and damage surfaces in stress space. The main feature of the proposed formulation is the direct and independent consideration of the damage mechanisms (isotropic damage, cracking, etc.) degrading the stiffness of the material, thus allowing for a complete physical characterization of these effects. This modular structure is accomplished by a kinematic decomposition of the strains in an elastic, plastic and multiple damage parts, as belonging to each activated damage mechanism. An additive decomposition in the infinitesimal range of interest is considered. Based on this decomposition, the constitutive characterization alluded to above for each damage mechanism is carried out in a complete thermodynamically consistent framework. One of the virtues of the considered framework is the fact that it includes many of the diverse damage models existing in the literature as particular cases. In this way, the developments presented herein furnish a unified framework for the formulation of continuum damage models, including isotropic damage, compliance based formulations, effective stress anisotropic models, smeared crack models and the related formulations of cracking and damage based on strong discontinuities. Besides the clear physical significance added to these existing formulations, the proposed framework also defines a very convenient context for the efficient numerical integration of the resulting models. This aspect is explored in Part II of this work, as it is the application of the framework proposed herein to the numerical simulation of porous metals.
Abstract
We identify in this paper a general framework for the development of continuum damage models in their fully coupled plastic damage form. The focus of this paper is directed [...]
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The use of particle methods for the simulations of additive manufacturing processes
P. Wriggers

Videos of Plenary Lectures presented at VI International Conference on Particle-Based Methods (PARTICLES 2019) (2020). 7
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Massively parallel methods for immersed boundary simulations of particles in viscoelastic fluids
E. Shaqfeh

Videos of Plenary Lectures presented at VI International Conference on Particle-Based Methods (PARTICLES 2019) (2020). 6
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Particle scale modelling in soil mechanics: Stiffness, strength, and seepage
C. O´Sullivan

Videos of Plenary Lectures presented at VI International Conference on Particle-Based Methods (PARTICLES 2019) (2020). 5
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Coupled plastic-damaged model
B. Luccioni, S. Oller, R. Danesi

Comput. Methods Appl. Mech. Engrg., (1996). Vol. 129 (1-2), pp. 81-89

Abstract
A constitutive model that couples plasticity and damage is presented. The model is thermodynamically consistent and comes from a generalization of classical plasticity theory and isotropic damage theory of Kachanov. Coupling between plasticity and damage is achieved through a simultaneous solution of the plastic and the damage problem. After a description of the model, a numerical algorithm for the integration of the resulting constitutive equations is presented. It is an Euler Backward type of algorithm that is particularly suitable to solve plain stress non-linear problems with a 2D finite element program. The consistent stiffness matrix is also derived. The paper is completed with some application examples that show that the model presented accurately reproduces the behaviour of elastic-plastic-damaged materials.
Abstract
A constitutive model that couples plasticity and damage is presented. The model is thermodynamically consistent and comes from a generalization of classical plasticity theory [...]
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Is particle and mesh a promissory combination for stable and high order schemes
N. Nigro

Videos of Plenary Lectures presented at VI International Conference on Particle-Based Methods (PARTICLES 2019) (2020). 4
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Discrete element modelling in granular mechanics, Recent breakthroughs
F. Darve

Videos of Plenary Lectures presented at VI International Conference on Particle-Based Methods (PARTICLES 2019) (2020). 3
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The bonded DEM. Strength and weakness
M. Celigueta

Videos of Plenary Lectures presented at VI International Conference on Particle-Based Methods (PARTICLES 2019) (2020). 2
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A plasticity model for simulation of industrial powder compaction processes
J. Oliver, S. Oller, J. Cante

Int. J. Solids and Structures (1996). Vol. 33 (20-22), 3161-3178

Abstract
A constitutive model, based on large strain plasticity, for simulation of industrial powder compaction processes is presented. The elastic response is stated in terms of a hyperelastic model based on a hookean elastic free energy. Plastic response is defined in terms of a two parameter yield surface that evolves in terms of the relative density. Two different flow rules are considered and tested in front of some available experimental results. Application to the simulation of an actual powder-metallurgy compaction process is also shown.
Abstract
A constitutive model, based on large strain plasticity, for simulation of industrial powder compaction processes is presented. The elastic response is stated in terms of a [...]
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Granular flows and particle-laden fluids interacting with thin flexible structures
E. Campello

Videos of Plenary Lectures presented at VI International Conference on Particle-Based Methods (PARTICLES 2019) (2020). 1
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Evaluation of the damage degree in buildings structures subjected to earthquakes
A. Barbat, A. Hanganu, S. Oller

Revue de méchanique appliquée (1994). Vol. 39 (1), pp. 23-36

Abstract
This paper represents an overview of the investigation pursued by the authors in the field of damage evaluation of concrete structures. A procedure to evaluate the damage of reinforced concrete structures subjected to static and dynamic actions has been developed, which is based on a local damage constitutive model using Kachanov’s theory. The constitutive model is used within a finite element frame, a non-linear Newmark-type tangent incremental time integration scheme is employed and finally, an overall global damage index, based on potential energy criteria, is developed and justified.
Abstract
This paper represents an overview of the investigation pursued by the authors in the field of damage evaluation of concrete structures. A procedure to evaluate the damage [...]
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Sustainable Configuration Management Implementation on Industrial Environments
E. Environments, J. LARUMBE

JAIME LARUMBE's personal collection (2020). 1

Abstract
Configuration Management [CM] is a Systems Engineering process for establishing and maintaining consistency of a product´s performance, functional, and physical attributes with its requirements, design, and operational information throughout its life. However, nor a scientific method neither systematically structured knowledge is followed in its application. Besides, the lack of a proper Configuration Management, or its insufficient implementation, can be very expensive and sometimes can have catastrophic consequences in Industrial constructions such as failure of equipment or loss of life. Hence, the aim of this research is to define a systematically structured procedure for the practical implementation of Configuration Management in Industrial engineering programs. This is done via the definition of a standardized procedure for identifying, selecting and categorizing the Configuration Items that will lead to the practical and sustainable implementation of Configuration Management. As a result, the proposed methodology guarantees quality, reproducibility and sustainability on Configuration Management implementation in any system or subsystem of a Industrial engineering project.
Abstract
Configuration Management [CM] is a Systems Engineering process for establishing and maintaining consistency of a product´s performance, functional, and physical attributes [...]
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Experiments on reinforced brick masonry vaulted light roofs
F. López-Almansa, P. Roca, V. Sarrablo, X. Cahís, J. Canet

Structural Journal (2010). Vol. 107 (3), pp. 355-363

Abstract
This paper describes structural tests of thin vaults made of reinforced brick masonry. The experiments consist of concentrated loading tests of 14 full-scale laboratory vaults. These vaults are designed to include common situations such as short- to midspan length, low-mid-high rise, rigid-flexible-sliding supports, instantaneous-sustained loading, low-high strength mortar, point-line loading, central-eccentric loading, point-line supports, hinged-clamped supports, symmetric-asymmetric shape, double layer versus single layer reinforcement, and uniaxial-biaxial bending, among others. The tests mainly aim to obtain the collapse loads and to characterize the pre- and post-peak response. The results show satisfactory structural performance, both in terms of ductility and strength. Moreover, it is possible to predict the structural response with numerical models developed specifically for this purpose. Flat specimens were also tested to determine the punching shear strength of the vaults. This work is part of a larger research project aimed at promoting innovative semi-prefabrication techniques for reinforced brick masonry vaulted light roofs.
Abstract
This paper describes structural tests of thin vaults made of reinforced brick masonry. The experiments consist of concentrated loading tests of 14 full-scale laboratory vaults. [...]
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A numerical-experimental method for characterizing recycled asphalt mixtures
R. Miró, F. Pérez, S. Oller, J. Canet, J. González

Road materials and pavement design (2008). Vol. 9 (4), pp. 711-730

Abstract
Experimental techniques usually employed in the characterization of conventional mixes are not able to clearly describe some specific properties of the recycled mixes, which are determinant in the material's mechanical response like cracking strength or tenacity. These new specific properties demands new methods of testing to know the really conditioning mechanical variables taking part in the process, so that being able to characterize and design new recycled mixes in an optimum way. In this paper, the direct tensile test is analyzed as a suitable method for evaluating the properties of recycled asphalt mixtures for different percentages of reclaimed asphalt pavement. A constitutive formulation has been developed to simulate the experimental results and can be used in conjunction with the experimental analysis of the recycled asphalt properties to provide an accurate characterization of the material.
Abstract
Experimental techniques usually employed in the characterization of conventional mixes are not able to clearly describe some specific properties of the recycled mixes, which [...]
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Limit analysis of reinforced masonry vaults
P. Roca, F. López-Almansa, J. Canet, A. Hanganu

Engineering Structures (2007). Vol. 23 (3), pp. 431-439

Abstract
Reinforced brick masonry has experienced only scarce use as a fully structural material due to, among other reasons, the lack of design criteria and calculation tools allowing a scientific, but also practical, engineering approach to design and assessment. Aiming at contributing to a more widespread use of this material, a simplified method for the ultimate analysis of reinforced masonry arches and cylindrical vaults, based on the lower-bound theorem (or static approach) of plasticity, has been developed. This approach has been satisfactorily validated by comparison with experimental and numerical results obtained by more accurate numerical models.
Abstract
Reinforced brick masonry has experienced only scarce use as a fully structural material due to, among other reasons, the lack of design criteria and calculation tools [...]
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A viscoplastic constitutive model with strain rate variables for asphalt mixtures—numerical simulation
J. González, J. Canet, S. Oller, R. Miró

Computational Materials Science (2007). Vol. 38 (4), pp. 543-560

Abstract
The study and development of recycling techniques for pavements is an increasing activity in engineering nowadays. This research line demands a more realistic characterization of the material properties with the aim of simulate the asphalt mixture’s response placed into a multilayered system over granular bases, under dynamic loads, considering also temperature variation or strength reduction for cyclic loads. In order to improve the current formulations, a new viscoplastic model has been developed assuming the strain rate dependency of the material’s response observed in the experimental tests. The strain rate variable affects in a significant way the Young modulus and the viscosity parameter of the model. According to this hypothesis a constitutive equations have been formulated. The mechanical variables involved have been calibrated according to experimental results, developing new expressions for the strain rate dependent parameters. The new viscoplastic model permits us to characterize the material’s response with a few mechanical values, easily obtained from standard laboratory tests. The results obtained show a good approximation to experimental laboratory curves for different rates of loading and temperatures. The model has been applied to simulate the response of a real flexible pavement structure conformed by two asphalt layers over two granular bases, that’s materials with different constitutive behaviors. Experimental tests in the recycled track have been made obtaining the horizontal strain evolution under dynamic load. Different loading rates and temperatures, as well as cracked and continuum pavement responses have been considered in the study. Strains were measured in the interface between the two asphalt layers and simulated using the here proposed model offering a fairly good approximation of the real response observed in the track, although the degree of variation even in the experimental curves is quite high. The results of this study represent a proper base for further developments in structural analysis of pavement layers, considering more complex phenomena, determinant in the long term material’s response, to develop a numerical tool for pavements’ design and lifetime prediction.
Abstract
The study and development of recycling techniques for pavements is an increasing activity in engineering nowadays. This research line demands a more realistic characterization [...]
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Composite material behavior using a homogenization double scale method
S. Oller, J. Canet, F. Zalamea

Journal of Engineering Mechanics (2005). Vol. 131 (1), pp. 65-79

Abstract
In this paper, we present a two-scale numerical method in which structures made up of composite materials are simulated. The method proposed lies within the context of homogenization theory and assumes the periodicity of the internal structure of the material. The problem is divided into two scales of different orders of magnitude: A macroscopic scale in which the body and structure of the composite material is simulated, and a microscopic scale in which an elemental volume called a “cell” simulates the material. In this work, the homogenized strain tensor is related to the transformation of the periodicity vectors. The problem of composite materials is posed as a coupled, two-scale problem, in which the constitutive equation of the composite material becomes the solution of the boundary-value problem in the cell domain. Solving various examples found in the bibliography on this subject demonstrates the validity of the method.
Abstract
In this paper, we present a two-scale numerical method in which structures made up of composite materials are simulated. The method proposed lies within the context of homogenization [...]
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Numerical study of the behaviour of concrete reinforced with short fibers
S. Oller, A. Barbat, J. Canet

Hormigón y Acero (2004). Vol. 55 (232), pp. 113-123

Abstract
An approach for the short fibers reinforced concrete behavior is presented in this work. A formulation based on a modification of the classical mixing theory to obtain the composite mechanical properties starting from the single compounding characteristics (concrete−short fibers) is developed. Numerical results obtained by means of the finite element method are also shown and the possibilities of using a simplified analytical method in the study of the short fibers reinforced concrete are commented. The development of the work studies the behavior of the concrete reinforced with short fibers and the characteristics that justify its use. It studies the internal balance and the stress transmission mechanism between the concrete and the short fibers as well as the general formulation of the problem and its insertion within the frame of the finite element technique. A brief comment is made on the simplified treatment of the behavior of the concrete reinforced with short fibers and a validation example is presented.
Abstract
An approach for the short fibers reinforced concrete behavior is presented in this work. A formulation based on a modification of the classical mixing theory to obtain the [...]
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Use of dampers and seismic connectors in bridges
J. Forment, J. Canet, A. Aparicio

Hormigón y Acero (2000). Vol. 51 (217), pp. 81-100

Abstract
The earthquakes have always represented on of the most dread destructive phenomena, for they affect the last stability of the structures. The modern societies are not prepared any more to accept then as a fatility, and the trend is now to provide, for structures situated in critical seismic zones, specific devices which nullify, or at least reduce the effect of the earthquakes. In this paper we are going to present the effects that the establishment of two similar seismic devices - the dampers and the seismic connectors - produces in different kinds of bridges.
Abstract
The earthquakes have always represented on of the most dread destructive phenomena, for they affect the last stability of the structures. The modern societies are not prepared [...]
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Matching user accounts based on location verification across social networks
X. Zhou, J. Yang, Z. lin, H. Xu

Rev. int. métodos numér. cálc. diseño ing. (2020). Vol. 36, (1), 8

Abstract
Social network has become the main platform for people to obtain information and connect with each other. Matching user accounts can help us build better users’ profiles and benefit many applications. It has attracted much attention from both industry and academia. At present, cross-platform user identification can be divided into three categories: based on user basic attribute information, user online social structure relationship and user behavior. Research on mobile social networks is a kind of dynamic mixed data analysis. Due to the remarkable heterogeneity of its data across platforms and the incomplete and untrue information caused by users’ concealment behavior, the recognition rate of the algorithm is relatively low. The paper provides a new matching user accounts method based on location verification. First, the self-centered network algorithm is applied to find cross-network edges in the respective networks of the two users to be matched, which is taken as the initial similarity value of the two users. Secondly, the longitude, latitude and time coordinates of a single platform node were used to modify the similarity. Specific 5 time points were selected within 24 hours and the error range of 10min was taken as the calculation method of great circle distance. Thirdly, since the user did not log in a certain social platform in a certain period of time, the convolutional neural network algorithm was adopted to mark the trajectory. Finally, all users in the whole network are identified by iterative operation. Experimental results on artificial random networks and real social networks show that the proposed algorithm has a high readiness rate and recall rate.
Abstract
Social network has become the main platform for people to obtain information and connect with each other. Matching user accounts can help us build better users’ profiles [...]
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Study of the aerodynamic forces on a simplified shape X-43 aircraft under supersonic conditions, design optimization
L. Caros, C. Jané, M. Coma, J. Pons Prats, J. Bergadà

Rev. int. métodos numér. cálc. diseño ing. (2020). Vol. 36, (1), 4

Abstract
The paper focuses on the shape optimization, based on the resultant aerodynamic forces, of a simplified X-43 aircraft. The equations of oblique shock waves and Prandtl-Meyer expansion waves, along with the improvement of the aircraft geometry using a genetic algorithm optimisation, will allow to shape and optimize the external dimensions of the bi-dimensional simplified aircraft design. The main purpose of the optimisation is the reduction of the drag force while maintaining a sufficient lift to hold the weight of the aircraft. The optimization is undertaken at four different altitudes, obtaining for each altitude the most favourable aircraft shape to maximize the aircraft efficiency. The study can be extended to various possible aircraft weight configurations.
Abstract
The paper focuses on the shape optimization, based on the resultant aerodynamic forces, of a simplified X-43 aircraft. The equations of oblique shock waves and Prandtl-Meyer [...]
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Pipeline Information Modeling: A New Tool for Pipeline Engineering
B. Tian, Z. Liang, L. Zhang

Rev. int. métodos numér. cálc. diseño ing. (2020). Vol. 36, (1), 6

Abstract
Pipeline Engineering is a comprehensive system project with huge investment, high complexity, strong technical and strict security requirements. The conventional construction and management mode for pipeline project has encountered a variety of bottlenecks in the development, and digital informatization of pipeline is the inevitable trend for the future pipeline industry development. Therefore, combining with the existing technical achievements, this paper puts forward and defines a new concept- “Pipeline Information Modeling (PIM)”, which can use digital model for the whole life-cycle of pipeline management. Its characteristics and architecture are expounded, and the relationship and difference are summarized between PIM and other related theories such as BIM, pipeline integrity management, and digital pipeline. Meanwhile, a case study of several applications in long-distance oil & gas transmission pipeline engineering is analyzed. Finally, the challenges PIM will face in the future development are discussed. PIM is still in its infancy, and theoretical system and technical method still need to be constantly perfected. But its emergence has important significance for improving pipeline engineering scientific and technological level and accelerating transformation of industry informatization, which will have great application foreground. '''Key words:''' Pipeline engineering; Life-cycle; Digital model; Long-distance pipeline;
Abstract
Pipeline Engineering is a comprehensive system project with huge investment, high complexity, strong technical and strict security requirements. The conventional construction [...]
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Time-scale analysis based modal identification using mobile sensors
M. Marmolejo, J. Marulanda, P. Thomson

Rev. int. métodos numér. cálc. diseño ing. (2020). Vol. 36, (1), 7

Abstract
'Civil structures, once built and released for use, are expected to fulfil operational standards for extended periods. The fact, a civil structure´s life, is determined by temporary deterioration, harsh ambient, misuse, destruction, and, eventual rehabilitation for current use or conservation for historical reasons. Initially, vibrational analysis with stationary sensors, broad logistics and a large array of sensors to provide densely detailed data were required. The next evolutionary step; the simplification of the while-under-use data-acquisition stage; better, faster, more detailed parameters for diagnosis. With the structure under normal operation, a stationary reference sensor, a mobile sensor able to travel through specific trajectories over the structure, deep computational data analysis provides better, deeper, clearer frequencies, mode shapes and damping ratios. A structural health monitoring system should be able to reliably assess structural wellness under operational conditions. Such are the benefits of a mobile sensor monitoring and diagnosis system. This paper utilizes the time–scale analysis method and the Continuous Wavelet Transform (CWT) through a complex Morlet wavelet to extract modal parameters from the signal responses. The theoretical development is validated by numeric simulations on a simply supported beam and by double experimental confirmation on a pedestrian bridge at Universidad del Valle, in Cali (Colombia), by the technique herein, and by a stationary sensor scheme.
Abstract
'Civil structures, once built and released for use, are expected to fulfil operational standards for extended periods. The fact, a civil structure´s life, is determined [...]
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Evaluation of the optical contamination of open path CO2 gas analyzers in measurements on a freshwater surface
F. Armani, N. Dias, D. Junior

Rev. int. métodos numér. cálc. diseño ing. (2020). Vol. 36, (1), 11

Abstract
Measurements of air-sea CO2 fluxes with Eddy Covariance (EC) are generally affected by the optical contamination of open path gas analyzers. Since the conditions of saltwater environments may be similar to those of freshwater environments, in this work we evaluate whether this contamination is occurring in the LI-7500 open path CO2 gas analyzer (''LI-COR Biosciences Ltd''), used in an experiment to measure greenhouse gas fluxes over the reservoir of the Itaipu Hydroelectric Power Plant. We evaluated the optical contamination indicators in the CO2 measurements and two corrections for this: the numerical method called PKT method, proposed for CO2 flux correction over ocean, and a multiple linear regression model. We find that the PKT method does not produce physically plausible results and that, contrary to what has been reported in ocean measurements, the measurements of the Itaipu experiment suffer less interference in more humid conditions. CO2 correction by the regression model preserved the pattern of CO2 flux daily variation, but it attenuated the magnitude of the fluxes: the average of the uncorrected fluxes was <math>-24.35</math>μgm-2s-1, while the average of the fluxes corrected by the statistical model was <math>-11.73</math>μgm-2s-1.
Abstract
Measurements of air-sea CO2 fluxes with Eddy Covariance (EC) are generally affected by the optical contamination of open path gas analyzers. Since the [...]
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Numerical approach to determine the capacity curves of clay masonry walls with openings
J. Campbell, V. Silva, R. Balboa, M. Durán

Rev. int. métodos numér. cálc. diseño ing. (2020). Vol. 36, (1), 12

Abstract
In this work a numerical model to obtain the pushover curves of clay masonry walls with openings is presented. These curves represent the non-linear structural behavior of masonry walls with openings subjected to loads in their own plane. The openings represent non-structural elements like doors, windows, among others. These walls can be considered as reinforced or confined masonry and the opening must be rectangular and may have different dimensions and a variable position inside the wall. The main result of the model was a pushover curve, which is compared with the curves obtained from laboratory tests (for walls with and without openings). The model was developed using the software ANSYS [1] version 14.5, based on the model proposed by Campbell and Durán [2].
Abstract
In this work a numerical model to obtain the pushover curves of clay masonry walls with openings is presented. These curves represent the non-linear structural behavior of [...]
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Thermal-conductive model algorithm for the accurate calculation of temperatures in electrical power conductors
D. Cardenas

Rev. int. métodos numér. cálc. diseño ing. (2020). Vol. 36, (1), 10

Abstract
The thermal-conductive models for the calculation of the electrical conductors and their energy dissipations have been able to solve doubts about the power conductors, which has been permanently unsuspected. Before thinking about thermally characterizing an electrical conductor, it was enough with the application of simple Joule-type equations, with constant resistive intrinsic properties in the conductor, as well as invariable considerations in the conditions that surround the conductor. In fact, just as is exposed, this has been published on the top of the best known electrical standards, such as those issued by the National Fire Protection Association (NFPA), as well as those edited by the International Electrotechnical Commission (IEC). It has been demonstrated that electric cables with higher electrical intensities, move away from the behavior predicted by the Joule type models, sometimes with energy dissipations 50% higher than those predicted by Joule. This is due to the non-linearities of the intrinsic properties of the cable, and the inconsistency of the environmental conditions surrounding the cable at the time it is going to heat. The novel thermal-conductive models with just ten years of development, are today a very complete solution with unparalleled accuracy (errors less than 0.01% in energy and temperature) in the thermal predictions of conductors; but due to its high degree of mathematical complexity requires in the most of cases to use numerical methods to obtain practical solutions. In this paper a new general algorithm is shown, which stands out for its simplicity compared to the first thermoconductive models, solving the models in thermal predictions of power electrical cables, without the need of huge databases, with simplicity, maneuverability and excellent practical results.
Abstract
The thermal-conductive models for the calculation of the electrical conductors and their energy dissipations have been able to solve doubts about the power conductors, which [...]
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Nonlinear Parametric Vibration Analysis of Radial Gates
S. Wu, Z. Wang, H. Jiang

Rev. int. métodos numér. cálc. diseño ing. (2020). Vol. 36, (1), 9

Abstract
In this work, based on dynamic characteristics of radial gates, a nonlinear diﬀerential equation of motion for the radial gate arm is established. Excitation conditions of principal parametric resonance and subharmonic parametric resonance are obtained by using multi-scale method and numerical method. The parameter analysis shows that: comparing with traditional calculation method of dynamic instability region division, the presented method is more suitable to analysis of parametric vibration for radial gates as considering the end moment, vibration duration and amplitude. The vibration amplitudes of arm increase with the increase of its length and excitation amplitude, as well as the decrease of arm inclination angle. Moreover, the parametric resonance is easier to be excited and its resonance region become wider with the initial end moment increasing. Since the vibration response of the arm is influenced by the nonlinear term in the equation, the damping effect is limited. Thus, energy transfer method (e.g. tuned mass damper) can be adopted to achieve vibration control.
Abstract
In this work, based on dynamic characteristics of radial gates, a nonlinear diﬀerential equation of motion for the radial gate arm is established. Excitation [...]
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Virtual modelling of stress paths CKoU and CKoD on collapsible porous clayey soils
J. Ruge, E. Martinez, S. Bañol, J. León, F. Molina-Gómez

Rev. int. métodos numér. cálc. diseño ing. (2020). Vol. 36, (1), 3

Abstract
In geotechnical engineering one of the challenges is the soil characterization. Nevertheless, currently it exists computational tools, which permits estimate the soil behaviour from information obtained in the laboratory. This document addresses the numerical modelling of triaxial tests set with Ko consolidation during its shear stage by means of single element test tool. The work methodology was based on the stress paths comparison between lab data and numerical simulations with three different constitutive models: (i) Mohr-Coulomb, (ii) Cam-Clay Modified, (iii) Hypoplastic. Such stress paths were obtained in drained and undrained conditions. The soil material corresponds to a porous collapsible clay from Brasilia (Brazil). Results show the calibration of the parameters for each constitutive model. Besides, presents the stress-strain curves until achieving the critical state condition in the simulations. Finally, it was established the constitutive model that presents the best fitting to the real behaviour of this kind of material, under specific conditions for advanced triaxial tests.
Abstract
In geotechnical engineering one of the challenges is the soil characterization. Nevertheless, currently it exists computational tools, which permits estimate the soil behaviour [...]
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Fragility curves based on the numerical analysis of masonry walls against subsidence, using the Abaqus / CAE software and relying on the pulldown technique
Y. Chávez Pérez, J. Ortiz-Lozano

Rev. int. métodos numér. cálc. diseño ing. (2020). Vol. 36, (1), 5

Abstract
This research uses Abaqus / CAE software as a computational tool, to obtain numerical models that correctly describe the behavior of masonry walls against subsidence. To do this, a mathematical calibration process is performed, the angular distortion values are obtained for different load states and compared with the experimental results presented by the researcher Charry Ablanque in 2010, the influence of the dimensions of the wall is studied in its resistance and the fragility curves of the material are constructed to evaluate the state of damage of the element, for a certain value of angular distortion.
Abstract
This research uses Abaqus / CAE software as a computational tool, to obtain numerical models that correctly describe the behavior of masonry walls against subsidence. To do [...]
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Elastic dynamics analysis in steel tubular towers for horizontal axis wind turbines
D. Lima, P. López-Yánez

Rev. int. métodos numér. cálc. diseño ing. (2020). Vol. 36, (1), 2

Abstract
Este artigo tem por objetivo a análise dinâmica elástica de uma torre tubular de aço para aerogerador de eixo horizontal utilizando elementos finitos de barra (código próprio) e elementos finitos de casca e sólidos (modelagem feita no ANSYS). Para tal, apresenta-se uma fundamentação teórica que consiste no desenvolvimento da equação de movimento a partir da equação de Lagrange. Em seguida, mostra-se o método de superposição modal para resolução da equação de movimento matricial e obtenção da resposta dinâmica da torre. Na segunda parte deste artigo, apresenta-se o desenvolvimento para montagem das matrizes de massa e de amortecimento da torre modelada com código próprio em elementos finitos de barra. Na parte de resultados, inicialmente, expõem-se as matrizes de rigidez, de massa e de amortecimento para certo nível de discretização da torre modelada com elementos finitos de barra. Em seguida, foram mostrados os resultados da análise modal feita tanto para o modelo com elementos finitos de casca, com e sem base flexível, quanto para o modelo de elementos finitos de barra; em que se apresentam os modos e as frequências de vibração da torre em todos os modelos. Por fim, foram analisadas as respostas da torre: na direção do fluxo de vento, quando submetida por um vetor de forças ressonantes, com o 1º modo de vibração desta, que representam a parcela flutuante do vento; e, na direção transversal ao fluxo de vento em decorrência do desprendimento cadenciado de vórtices de von Kárman. Os resultados da análise modal feita, tanto para o modelo com elementos finitos de casca, com e sem base flexível, quanto para o modelo de elementos finitos de barra mostram-se similares, principalmente com relação ao 1º modo de vibração da torre. Portanto, o modelo constituído por Elementos Finitos (EF) de barra pode ser utilizado como representativo do comportamento dinâmico da torre quando esta é submetida às excitações ressonantes à sua frequência fundamental.
Abstract
Este artigo tem por objetivo a análise dinâmica elástica de uma torre tubular de aço para aerogerador de eixo horizontal utilizando elementos finitos [...]
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Setting of the parameters to capacity spectra of steel buildings
C. Bermúdez, L. Pujades, A. Barbat

Rev. int. métodos numér. cálc. diseño ing. (2020). Vol. 36, (1), 1

Abstract
The first part of this paper provides a theoretical framework on the subject of capacity spectra and its usefulness in studying the seismic vulnerability of buildings. Then, the works of some researchers, which have moved forward in the direction of setting the parameters of those curves, are reported and theirs most important conclusions are highlighted. After that, the models that have been used in this research together with theirs capacity spectra are introduced. Finally, techniques for setting parameters are applied on those curves and the most important results and conclusions are presented.
Abstract
The first part of this paper provides a theoretical framework on the subject of capacity spectra and its usefulness in studying the seismic vulnerability of buildings. Then, [...]
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