Documents published in 2014 : Scipedia

Automated design of prestressed concrete precast road bridges with hybrid memetic algorithms
J. Martí, V. Yepes, F. González-Vidosa, A. Luz

Rev. int. métodos numér. cálc. diseño ing. (2014). Vol. 30, (3)

Abstract
This paper deals with the minimum cost automatic design of precast bridge decks made of U-beams and an upper slab. It uses a hybrid memetic algorithm that combines the population search of solutions by genetic algorithms and a search by variable neighborhood. This algorithm is applied to a bridge made of two isostatic U-beams of 20-40 m of span and a width of 12 m. This example has 40 discrete variables. The evaluation module takes into account the service and ultimate limit states usually considered for these structures, i.e. flexure, shear, torsion, cracking, deflections, etc. The use of the memetic algorithm requires its previous calibration. Each of the heuristics is run 12 times, obtaining information about the minimum and average values, as well as the scatter. The parametric study showed a good correlation for the cost, the number of strands and the steel and concrete quantities with the span length. Savings have been found between 8 and 50% compared to other structures really executed. The presented procedure allows the practical application to the real design and its adaptation to the precast process.
Abstract
This paper deals with the minimum cost automatic design of precast bridge decks made of U-beams and an upper slab. It uses a hybrid memetic algorithm that combines the population [...]
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Numerical method for the holistic evaluation of the seismic risk based on the fuzzy sets theory
M. Carreño, A. Barbat, O. Cardona

Rev. int. métodos numér. cálc. diseño ing. (2014). Vol. 30, (1)

Abstract
The fuzzy set theory offers a bridge between the symbolic and numerical processing, allowing managing qualitative concepts useful in the decision-making process related to the seismic risk management and, in general, to the disaster risk management. Its use in the seismic risk evaluation is necessary in the cases where the data required to apply a conventional method of assessing risk are not available or are insufficient. One possible solution, considered in this article, is to replace the missing information by expert opinions and to process the resulting qualitative variables and linguistic qualifications instead of numerical values. This process is based on the fuzzy set theory. In order to achieve an effective management, the risk must be defined as the potential physical, economic, social and environmental consequences which occur due to hazards in a given period of time. From this holistic perspective and using the fuzzy set theory, the proposed numerical method calculates a level of the physical risk and level of the aggravating conditions related to social fragility and to the lack of resilience, to determine a total risk level. In the article are included two examples of application of the proposed method and the obtained results are compared with those corresponding to a conventional method of holistic evaluation.
Abstract
The fuzzy set theory offers a bridge between the symbolic and numerical processing, allowing managing qualitative concepts useful in the decision-making process related to [...]
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Torsional effects in structures on soft soil
M. Suarez, J. Avilés

Rev. int. métodos numér. cálc. diseño ing. (2014). Vol. 30, (3)

Abstract
In this work the torsional vibrations of structures on soft soil caused by the combined effects of structural asymmetry and base rotation are evaluated. A simplified soil-structure system with five degrees of freedom is analyzed. The foundation is considered to be embedded into a uniform layer resting on an elastic half-space, under the incidence of inclined SH waves. Instead of matching the maximum torsional moments due to the independent effects of structural asymmetry and base rotation, a new approach for computing the design eccentricity is applied. Specifically, torsional eccentricity coefficients compatible with the peak coupled lateral-torsional response are obtained, using an ensemble of narrow-band earthquake motions typical of soft-soil sites in Mexico City. It is shown that these coefficients are not constant along the principal axes, but they depend on the position of the resistant element. Hence, it is necessary to compute them without assuming a linear variation, as is done nowadays. The torsional eccentricity coefficients can significantly differ from the currently codified values, particularly for torsionally flexible structures for which both coefficients may be negative. This implies that the lateral displacement is reduced by the effects of torsion.
Abstract
In this work the torsional vibrations of structures on soft soil caused by the combined effects of structural asymmetry and base rotation are evaluated. A simplified soil-structure [...]
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Dynamic factors for underpasses in high speed train lines
J. Vega, L. Hermanns, E. Alarcón, A. Fraile

Rev. int. métodos numér. cálc. diseño ing. (2014). Vol. 30, (3)

Abstract
Underpasses are common in modern railway lines. Wildlife corridors and drainage conduits often fall into this category of partially buried structures. Their dynamic behavior has received far less attention than that of other structures such as bridges, but their large number makes their study an interesting challenge from the viewpoint of safety and cost savings. The bridge design rules in accordance with the Eurocode involve checks on stresses according to dynamic loading. In the case of underpasses, those checks may be as much as those for bridges. Therefore, simplified design rules may align the design effort with their cost. Such a set of rules may provide estimations of response parameters based on the key parameters influencing the result. This paper contains a proposal based on a parametric study.
Abstract
Underpasses are common in modern railway lines. Wildlife corridors and drainage conduits often fall into this category of partially buried structures. Their dynamic behavior [...]
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Optimal topology seletion for 2D structures with stress constraints via Smooth Evolutionary Structural Optimization
V. Almeida, H. Simonetti, F. Neves

Rev. int. métodos numér. cálc. diseño ing. (2014). Vol. 30, (2)

Abstract
This paper approaches the topology optimization problems in plane linear elasticity considering the minimization of the volume with restriction of the stress employing an index of performance for monitoring the meeting of the optimum region. It is used for this purpose the classical evolutionary structural optimization, or ESO ‐ evolutionary structural optimization. This procedure is based on systematic and gradual removal of the elements with lower stress compared with the maximum stress of the structure. This procedure also known as a process “hard‐kill”. It is proposed a variant of the ESO method, called SESO ‐ Smoothing ESO, which is based on the philosophy that if an element is not really necessary for the structure, its contribution to the structural stiffness will gradually diminish until it has no longer influence in the structure, so its removal is performed smoothly. That is, their removal is done smoothly, reducing the values of the constitutive matrix of the element as if it were in the process of damage. A new performance index for the monitoring of this evolutionary process smoothed is proposed herein. The applications of ESO and SESO are made with the finite element method, but considering a high order triangular element based on the free formulation. Finally, it is implemented a spatial filter in terms of stress control, which was associated with SESO technique proved to be very stable and efficient in eliminating the formation of the checkerboard.
Abstract
This paper approaches the topology optimization problems in plane linear elasticity considering the minimization of the volume with restriction of the stress employing an [...]
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Development of a global optimization algorithm in ant colonies with feasible region selection for continuous search spaces
J. Fernández-Vargas, A. Bonilla-Petriciolet

Rev. int. métodos numér. cálc. diseño ing. (2014). Vol. 30, (3)

Abstract
This study introduces a new algorithm for the ant colony optimization (ACO) method, which has been proposed to solve global optimization problems with continuous decision variables. This algorithm, namely ACO-FRS, involves a strategy for the selection of feasible regions during optimization search and it performs the exploration of the search space using a similar approach to that used by the ants during the search of food. Four variants of this algorithm have been tested in several benchmark problems and the results of this study have been compared with those reported in literature for other ACO-type methods for continuous spaces. Overall, the results show that the incorporation of the selection of feasible regions allows the performing of a global search to explore those regions with low level of pheromone, thus increasing the feasibility of ACO for finding the global optimal solution.
Abstract
This study introduces a new algorithm for the ant colony optimization (ACO) method, which has been proposed to solve global optimization problems with continuous decision [...]
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Numerical formulation for the study of the damped composite structures using First and Higher‐order Shear Deformation theories
A. Faria, A. Lima

Rev. int. métodos numér. cálc. diseño ing. (2014). Vol. 30, (2)

Abstract
Composite materials have been used in the design of the aircrafts structures because their low weight and high mechanical strength. However, structures made in composite material are exposed to dynamical and/or static loading environments. Therefore, a major research effort is undertaken in the development of tools numerical for analysis and design of composite structures. This paper presents a numerical formulation of the composite structures using the Finite Element Method (FEM ). The damped composite structures, using inserted viscoelastic devices, and undamped composite structures are formulated by FEM . Viscoelastic materials are applied as continuous layers inserted on composite structures. The intrinsic damping of the composite material is included in the studies, too. The First‐order (FSDT ) and Higher‐order Shear Deformation (HSDT ) theories are formulated. They are distinguished by order of the approximation functions used in the mechanical displacements field. Both theories are computationally implemented using the Serendipity finite element. This is a rectangular finite element with 8 nodes, 5 or 11 degrees of freedom per node. The results are compared with papers predictions. The advantages and disadvantages of using each theory in the modeling of composite (thin or thick) and thick sandwiches structures, including the intrinsic and the viscoelastic damping, are discusses.
Abstract
Composite materials have been used in the design of the aircrafts structures because their low weight and high mechanical strength. However, structures made in composite material [...]
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Discussion on the article “Numerical evaluation of the flange thickness effect on the contact stress and prying action in T-Stub steel connection” by L.M. Bezerra, C.S. de Freitas, W.T. Matias and J.E. Carmona
J. Cisneros, D. Carazo-Álvarez, J. Carazo-Álvarez

Rev. int. métodos numér. cálc. diseño ing. (2014). Vol. 30, (2)

Abstract
A discussion is proposed on the paper “Evaluación numérica del efecto del espesor de la placa de contacto en la acción de palanca en conexión de acero tipo T” by L.M. Bezerra, C.S. de Freitas, W.T. Matias and J.E. Carmona. The topics to be discussed are the definition of the T-stub model, the bibliographic references used in the work and the finite element analysis assumptions adopted in the modeling of the components.
Abstract
A discussion is proposed on the paper “Evaluación numérica del efecto del espesor de la placa de contacto en la acción de palanca en conexión de acero tipo T” by L.M. [...]
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Robust design optimization using Kriging models: Application to the robust design optimization of truss structures
J. Martínez-Frutos, P. Martí

Rev. int. métodos numér. cálc. diseño ing. (2014). Vol. 30, (2)

Abstract
Conventional methods addressing the robust design optimization problem of structures usually require high computational requirements due to the nesting of uncertainty quantification within the optimization process. In order to address such a problem, this work proposes a methodology, based on Kriging models, to efficiently assess the uncertainty quantification in the optimization process. The Kriging model approximates the structural performance both in the design domain and in the stochastic domain, which allows to decouple the uncertainty quantification process and the optimization process. In addition, an infill criterion based on the variance of the Kriging prediction is included to update the Kriging model towards the global Pareto front. Three numerical examples show the applicability and the accuracy of the proposed methodology. The results show that the proposed method is appropriate to solve the robust design optimization problem with reasonable accuracy and a considerably lower number of function calls than required by conventional methods.
Abstract
Conventional methods addressing the robust design optimization problem of structures usually require high computational requirements due to the nesting of uncertainty quantification [...]
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Numerical evaluation of the flange thickness effect on the contact stress and prying action in T-Stub steel connection
L. Bezerra, C. Freitas, W. Matias Silva, J. Carmona

Rev. int. métodos numér. cálc. diseño ing. (2014). Vol. 30, (1)

Abstract
This paper presents a numerical study of «T-Stub» steel connections using FEM analyses. In such connections prying action phenomenon may take place. Prying action effect on the bolts has been studied before but the location of the prying action forces has always been simplified. The effect of the thickness of «T-Stub» flanges on contact areas between flanges and support base is investigated in this paper. A 3D finite element model is used and interface elements are employed for the investigation. Nonlinear FE analyses are undertaken on connection with different flange thickness and bolt preload with two bolts. Nonlinear gap elements are used as interfaces. Discussion and conclusions on contact areas and stresses, prying action distributions and resultant of loads on bolts in the «T-Stub» connections are presented.
Abstract
This paper presents a numerical study of «T-Stub» steel connections using FEM analyses. In such connections prying action phenomenon may take place. Prying action [...]
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Applicability of the strategies for the elastic seismic analysis of cable-stayed bridges
A. Cámara, M. Astiz

Rev. int. métodos numér. cálc. diseño ing. (2014). Vol. 30, (1)

Abstract
Several optimized analysis and modelling strategies are provided in this work in order to address the seismic behaviour of cable-stayed bridges in the elastic range, including the expected error ranges in terms of the tower shape, the main span or the stiffness associated with the foundation soil, among other project features. This valuable information for the designer is obtained through the comparative study of different analysis methodologies applied to a large number of cable-stayed bridge models, relating the observed deviations with the simplifications introduced in their mathematical developments. Both the widespread response spectrum analysis, the modal time history analysis and the direct integration of the coupled system of dynamics have been considered. Furthermore, the direct integration has been employed to address the effect of possible contacts and impacts between the deck and the towers during the earthquake in transverse direction. It is concluded that spectrum calculations provide results that are usually 20% lower than the reference modal time history analysis, which is the most precise method.
Abstract
Several optimized analysis and modelling strategies are provided in this work in order to address the seismic behaviour of cable-stayed bridges in the elastic range, including [...]
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Modeling the hydraulic performance of the aeration system in dam bottom outlets using the particle finite element method
D. Pozo, F. Salazar, M. Toledo

Rev. int. métodos numér. cálc. diseño ing. (2014). Vol. 30, (1)

Abstract
Dam bottom are key elements to control the water surface elevation below the spillway crest level. As a consequence, they are essential in reservoir management, and play a vital role in dam safety. The convenience of installing an aeration system in dam bottom outlets is well known nowadays. Otherwise, damages due to cavitation and vibration are frequently serious, as could be observed in several dams built in the beginning of the 20th century. The intrinsic features of the phenomenon make it hard to analyze either in situ or in full scaled experimental facilities. As a consequence, most of the previous studies have been carried out in small-scale physical models. The results of these works have been used to develop empirical formulas which provide an estimation of the maximum air demand of the aeration system. The progress in the development of numerical methods allows addressing this problem using numerical modeling. The Particle Finite Element Method (PFEM) had been previously applied and validated for the analysis of the performance of other hydraulic structures. In this work, it has been used to simulate air-water interaction in free-flowing gated conduits. The objective is to avoid the scale effects of physical modeling and to study in detail the key parameters. The results clarify the behaviour of the involved fluids (air and water) and provide information about the influence of the main variables that affect their circulation.
Abstract
Dam bottom are key elements to control the water surface elevation below the spillway crest level. As a consequence, they are essential in reservoir management, and play a [...]
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Mixed optimization of power transmission structures: An application of the simulated annealing algorithm
S. Martínez, J. París, I. Colominas, F. Navarrina, M. Casteleiro

Rev. int. métodos numér. cálc. diseño ing. (2014). Vol. 30, (2)

Abstract
A general methodology to optimize the weight of power transmission structures is presented in this article. This methodology is based on the simulated annealing algorithm defined by Kirkpatrick in the early ‘80s. This algorithm consists of a stochastic approach that allows to explore and analyze solutions that do not improve the objective function in order to develop a better exploration of the design region and to obtain the global optimum. The proposed algorithm allows to consider the discrete behavior of the sectional variables for each element and the continuous behavior of the general geometry variables. Thus, an optimization methodology that can deal with a mixed optimization problem and includes both continuum and discrete design variables is developed. In addition, it does not require to study all the possible design combinations defined by discrete design variables. The algorithm proposed usually requires to develop a large number of simulations (structural analysis in this case) in practical applications. Thus, the authors have developed first order Taylor expansions and the first order sensitivity analysis involved in order to reduce the CPU time required. Exterior penalty functions have been also included to deal with the design constraints. Thus, the general methodology proposed allows to optimize real power transmission structures in acceptable CPU time.
Abstract
A general methodology to optimize the weight of power transmission structures is presented in this article. This methodology is based on the simulated annealing algorithm [...]
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Detail-preserving mesh simplification
M. Pasenau, C. Andújar

Monograph CIMNE (2014). M145

Abstract
Mesh simplification is an important problem in computer graphics. Given a polygonal mesh, the goal is to generate another mesh which approximates the underlying shape but includes less polygons, edges and vertices. Early methods focused only on preserving the overall shape of the geometric model, whereas current methods also handle meshes with attributes (normal vectors, colors, texture coordinates) so that both the mesh shape and the mesh appearance are preserved. The goal of this work is to develop, implement and test a mesh simplification algorithm able to simplify large models in-core using a vertex clustering algorithm. Several detail-preserving techniques will be examined and implemented and a new filter is proposed, taking into account geometry features and nodal defined attributes. We also review recent advances in spatial hash tables to achieve a more compact storage, and we analyze and evaluate their impact in the simplification process.
Abstract
Mesh simplification is an important problem in computer graphics. Given a polygonal mesh, the goal is to generate another mesh which approximates the underlying shape but [...]
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Unified updated Lagrangian formulation for the analysis of quasi and fully incompressible fluids and solids and their interaction via a partitioned scheme and the PFEM
A. Franci, E. Oñate, J. Carbonell

(2014). Research Report, Nº PI407

Abstract
In this work, a unified updated Lagrangian formulation for solving fluid-structure interaction (FSI) problems is derived. The mixed velocity-pressure formulation for hypoelastic solids and quasi and fully incompressible Newtonian fluids is obtained as an extension of the velocity formulation derived for a general continuum. The space discretization for the fluid domain is performed via the Particle Finite Element Method (PFEM), where for the solid domain a standard FEM is used. Linear interpolation is used for both the velocity and the pressure fields. The global FSI problem is solved using a Gauss-Seidel iterative scheme. The required stabilization for dealing with incompressible situations is given by an enhanced formulation of the Finite Calculus (FIC) technique [Oñate et al.]. The efficiency of the proposed strategy is tested by solving benchmark FSI problems.
Abstract
In this work, a unified updated Lagrangian formulation for solving fluid-structure interaction (FSI) problems is derived. The mixed velocity-pressure formulation for hypoelastic [...]
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A Particle Finite Element Method (PFEM) for coupled thermal analysis of quasi and fully incompressible flows and fluid-structure interaction
E. Oñate, A. Franci, J. Carbonell

(2014). Research Report, Nº PI403

Abstract
We present a Lagrangian formulation for coupled thermal analysis of quasi and fully incompressible flows and fluid-structure interaction (FSI) problems that has excellent mass preservation features. The success of the formulation lays on a residual-based stabilized expression of the mass balance equation obtained using the Finite Calculus (FIC) method. The governing equations are discretized with the FEM using simplicial elements with equal linear interpolation for the velocities, the pressure and the temperature. The merits of the formulation in terms of reduced mass loss and overall accuracy are verified in the solution of 2D and 3D adiabatic and thermally-coupled quasi-incompressible free-surface flow problems using the Particle Finite Element Method (PFEM). Examples include the sloshing of water in a tank and the falling of a water sphere and a cylinder into a tank containing water.
Abstract
We present a Lagrangian formulation for coupled thermal analysis of quasi and fully incompressible flows and fluid-structure interaction (FSI) problems that has excellent [...]
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Lagrangian analysis of multiscale particulate flows with the particle finite element method
E. Oñate, M. Celigueta, S. Latorre, G. Casas, R. Rossi, J. Rojek

(2014). Research Report, Nº PI405

Abstract
We present a Lagrangian numerical technique for the analysis of flows incorporating physical particles of different sizes. The numerical approach is based on the Particle Finite Element Method (PFEM) which blends concepts from particle-based techniques and the FEM. The basis of the Lagrangian formulation for particulate flows and the procedure for modelling the motion of small and large particles that are submerged in the fluid are described in detail. The numerical technique for analysis of this type of multiscale particulate flows using a stabilized mixed velocity-pressure formulation and the PFEM is also presented. Examples of application of the PFEM to several particulate flows problems are given.
Abstract
We present a Lagrangian numerical technique for the analysis of flows incorporating physical particles of different sizes. The numerical approach is based on the Particle [...]
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A particle finite element method for analysis of industrial forming processes
E. Oñate, A. Franci, J. Carbonell

(2014). Research Report, Nº PI406

Abstract
We present a generalized Lagrangian formulation for analysis of industrial forming processes involving thermally coupled interactions between deformable continua. The governing equations for the deformable bodies are written in a unified manner that holds both for fluids and solids. The success of the formulation lays on a residual-based expression of the mass conservation equation obtained using the Finite Calculus (FIC) method that provides the necessary stability for quasi/fully incompressible situations. The governing equations are discretized with the FEM via a mixed formulation using simplicial elements with equal linear interpolation for the velocities, the pressure and the temperature. The merits of the formulation are demonstrated in the solution of 2D and 3D thermally-coupled forming processes using the Particle Finite Element Method (PFEM).
Abstract
We present a generalized Lagrangian formulation for analysis of industrial forming processes involving thermally coupled interactions between deformable continua. The governing [...]
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