Artículos

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https://hdl.handle.net/10784/1349

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Mostrando 1 - 20 de 101

Accelerated Fatigue of Dentin with Exposure to Lactic Acid
(Elsevier BV, 2013-08-01) Orrego, Santiago; Mecánica Aplicada
Analisis Estructural de una losa vial bajo carga estática y simulación por el método de elementos finitos
(Facultad de Ingenierías del Instituto Tecnológico Metropolitano (ITM), 2009-01-01) Velez, Francisco Javier; Mecánica Aplicada
Analysis of the role of diffraction in topographic site effects using boundary element techniques
(Springer. Seismological Society of China, 2013-10) Gomez, Juan; Jaramillo, Juan Diego; Restrepo, Dorian; Valencia, Camilo; Juan Gomez (jgomezc1@eafit.edu.co); Mecánica Aplicada
The role played by the diffraction field on the problem of seismic site effects is studied. For that purpose we solve and analyze simple scattering problems under P and SV in-plane wave assumptions, using two well known direct boundary-element-based numerical methods. After establishing the difference between scattered and diffracted motions, and introducing the concept of artificious and physically based incoming fields, we obtain the amplitude of the Fourier spectra for the diffracted part of the response: this is achieved after establishing the connection between the spatial distribution of the transfer function over the studied simple topographies and the diffracted field. From the numerical simulations it is observed that this diffracted part of the response is responsible for the amplification of the surface ground motions due to the geometric effect. Furthermore, it is also found that the diffraction field sets in a fingerprint of the topographic effect in the total ground motions. These conclusions are further supported by observations in the time-domain in terms of snapshots of the propagation patterns over the complete computational model. In this sense the geometric singularities are clearly identified as sources of diffraction and for the considered range of dimensionless frequencies it is evident that larger amplifications are obtained for the geometries containing a larger number of diffraction sources thus resulting in a stronger topographic effect. The need for closed-form solutions of canonical problems to construct a robust analysis method based on the diffraction field is identified.
Analysis of the role of diffraction in topographic site effects using boundary element techniques
(Seismological Society of China, 2013-01-01) Gomez, J.; Restrepo, D.; Jaramillo, J.; Valencia, C.; Mecánica Aplicada
The role played by the diffraction field on the problem of seismic site effects is studied. For that purpose we solve and analyze simple scattering problems under PandSVin-plane wave assumptions, using two well known direct boundary-element-based numerical methods. After establishing the difference between scattered and diffracted motions, and introducing the concept of artificious and physically based incoming fields, we obtain the amplitude of the Fourier spectra for the diffracted part of the response: this is achieved after establishing the connection between the spatial distribution of the transfer function over the studied simple topographies and the diffracted field. From the numerical simulations it is observed that this diffracted part of the response is responsible for the amplification of the surface ground motions due to the geometric effect. Furthermore, it is also found that the diffraction field sets in a fingerprint of the topographic effect in the total ground motions. These conclusions are further supported by observations in the time-domain in terms of snapshots of the propagation patterns over the complete computational model. In this sense the geometric singularities are clearly identified as sources of diffraction and for the considered range of dimensionless frequencies it is evident that larger amplifications are obtained for the geometries containing a larger number of diffraction sources thus resulting in a stronger topographic effect. The need for closed-form solutions of canonical problems to construct a robust analysis method based on the diffraction field is identified. © The Seismological Society of China, Institute of Geophysics, China Earthquake Administration and Springer-Verlag Berlin Heidelberg 2013.
Analytic approximation to the scattering of antiplane shear waves by free surfaces of arbitrary shape via superposition of incident, reflected and diffracted rays
(OXFORD UNIV PRESS, 2013-03-01) Jaramillo, Juan; Gomez, Juan; Externo - Escuela - Ciencias; Vergara, Juan; Mecánica Aplicada
The scattering induced by surface topographies of arbitrary shapes, submitted to horizontally polarized shear waves (SH) is studied analytically. In particular, we propose an analysis technique based on a representation of the scattered field like the superposition of incident, reflected and diffracted rays. The diffraction contribution is the result of the interaction of the incident and reflectedwaves, with the geometric singularities present in the surface topography. This splitting of the solution into different terms, makes the difference between our method and alternative numerical/analytical approaches, where the complete field is described by a single term. The contribution from the incident and reflected fields is considered using standard techniques, while the diffracted field is obtained using the idea of a ray as was introduced by the geometrical theory of diffraction. Our final solution however, is an approximation in the sense that, surface-diffracted rays are neglected while we retain the contribution from corner-diffracted rays and its further diffraction. These surface rays are only present when the problem has smooth boundaries combined with shadow zones, which is far from being the typical scenario in far-field earthquake engineering. The proposed technique was tested in the study of a combined hill-canyon topography and the results were compared with those of a boundary element algorithm. After considering only secondary sources of diffraction, a difference of 0.09 per cent (with respect to the incident field amplitude) was observed. The proposed analysis technique can be used in the interpretation of numerical and experimental results and in the preliminary prediction of the response in complex topographies. © The Authors 2012. Published by Oxford University Press on behalf of The Royal Astronomical Society.
Aplicación de un método basado en el desempeño para el análisis y diseño sismo resistente de puentes de concreto reforzado
(Fondo Editorial Universidad EAFIT, 2013-06-01) BOTERO, JUAN CARLOS; Mecánica Aplicada
Automatic detection of building typology using deep learning methods on street level images
(PERGAMON-ELSEVIER SCIENCE LTD, 2020-03-20) Duque, J.; Gonzalez, D.; Rueda Plata, Diego; Acevedo, A.; Ramos, R.; Betancourt, A.; García, S.; Mecánica Aplicada
An exposure model is a key component for assessing potential human and economic losses from natural disasters. An exposure model consists of a spatially disaggregated description of the infrastructure and population of a region under study. Depending on the size of the settlement area, developing such models can be a costly and time-consuming task. In this paper we use a manually annotated dataset consisting of approximately 10,000 photos acquired at street level in the urban area of Medellín to explore the potential for using a convolutional neural network (CNN) to automatically detect building materials and types of lateral-load resisting systems, which are attributes that define a building's structural typology (which is a key issue in exposure models for seismic risk assessment). The results of the developed model achieved a precision of 93% and a recall of 95% when identifying nonductile buildings, which are the buildings most likely to be damaged in an earthquake. Identifying fine-grained material typology is more difficult, because many visual clues are physically hidden, but our model matches expert level performances, achieving a recall of 85% and accuracy scores ranging from 60% to 82% on the three most common building typologies, which account for 91% of the total building population in Medellín. Overall, this study shows that a CNN can make a substantial contribution to developing cost-effective exposure models. © 2020 Elsevier Ltd
Bandgap tuning in bioinspired helicoidal composites
(2019-10-01) Guarín-Zapata, Nicolás; Gómez, Juan; Kisailusc, David; D.Zavattieria, Pablo; Mecánica Aplicada
Base shear determination using response-spectrum modal analysis of multi-degree-of-freedom systems with soil–structure interaction
(Springer Netherlands, 2019-01-01) Arias H.; Jaramillo J.D.; Mecánica Aplicada
Building codes and design guidelines, e.g. FEMA (NEHRP recommended seismic provisions for new buildings and other structures, FEMA P-1050, Washington, 2015) and ASCE (Minimum design loads for buildings and other structures ASCE/SEI 7-10/2010, Reston, 2010), describe the problem of multi-degree-of-freedom systems with soil-structure interaction (SSI). These systems are modeled like those having a fundamental degree of freedom on a foundation with lateral and rotational interactions and the other vibration modes isolated and supported on a fixed foundation. This model oversimplifies the problem, neglecting the effects of having all modes coupled in the foundation with SSI. A simple, easily programmable, SSI model in which all vibration modes are coupled an attached to an infinitely rigid shallow foundation subjected to soil excitation is introduced here. Initially, the total response of the coupled system is calculated. Then, using traditional procedures to combine modal responses, a simplified alternative methodology to find the total response of this coupled system is proposed. The new methodology is verified against a robust numerical technique, i.e. boundary elements method, using a wide variety of cases that combine several types of soils, building heights and two structural typologies: bending frames and shear walls. Finally, it is clear from the parametric study that current methodologies, based only on the interaction of the fundamental mode of vibration of the structure, in some cases has a significant influence on the total base shear of buildings, particularly in tall buildings founded in soft soils. © 2019, Springer Nature B.V.
Características estructurales de escuelas colombianas de pórticos de hormigón reforzado con mampostería no reforzada
(Fondo Editorial Universidad EAFIT, 2017-05-08) Acevedo A.B.; Zora-Mejía, Faver N; Mecánica Aplicada
Assessment of the seismic vulnerability of the building stock of a region is a key issue for its seismic risk evaluation.
Caracterización de Imanes para aplicación en sistemas de sensado de posición
(Sociedad Colombiana de Física, 2010-06-25) Guarin, Nicolas; Velásquez, A. A.; Mecánica Aplicada
This paper reports the characterization of a set of Neodymium magnets with different sizes and geometries, which is devoted to determine the influence of the former parameters both in the magnitude as in the direction of the magnetic field
CFD Analysis of the Effect on Buoyancy Due to Terrain Temperature Based from an Integrated DEM and Landsat Infrared Imagery
(Fondo Editorial Universidad EAFIT, 2008-12-01) GARCIA, MANUEL JULIO; Mecánica Aplicada
CFD Numerical simulations of Francis turbines
(IMPRENTA UNIV ANTIOQUIA, 2010-02-01) GARCIA, MANUEL JULIO; Mecánica Aplicada
A comparative computational study of blood flow pattern in exemplary textile vascular grafts
(Taylor and Francis Ltd., 2018-01-01) Valencia, R.A.; García, M.J.; Bustamante, J.; Mecánica Aplicada
Textile vascular grafts are biomedical devices and play an important role serving as a solution for the partial replacement of damaged arterial vessels. It is believed that the success of a textile vascular graft, in the healing process after implantation, is due to the porous micro-structure of the wall. Although the transport of fluids through textiles is of great technical interest in biomedical applications, little is known about predicting the micro-flow pattern and cellular transport through the wall. The aim of this work is to investigate how the type of fabric, permeability and porosity affect both the local fluid dynamics at several scales and the fluid-particle interaction between platelets in textile grafts, related with the graft occlusion. This study involves both experimental and computational tests. Experimental tests are performed to characterize the permeability and porosity according to the ISO 7198 standard. The numerical process is based on a multi-scale approach where the fluid flow is solved with the Finite Element Method and the discrete particles are solved with the Molecular Dynamic Method. The results have shown that the type of fabric in textile vascular grafts and the degree of porosity and permeability affect both the local fluid dynamics and the level of penetration of platelets through the wall, thus indicating their importance as design parameters. © 2017 Informa UK Limited, trading as Taylor & Francis Group.
Computational characterization of the wave propagation behavior of multi-stable periodic cellular materials
(Elsevier Limited, 2019-01-01) Valencia, Camilo Andres; Restrepo D.; Mankame N.D.; Zavattieri P.D.; Gomez, Juan David; Mecánica Aplicada
In this work, we present a computational analysis of the planar wave propagation behavior of a one-dimensional periodic multi-stable cellular material. Wave propagation in these materials is interesting because they combine the ability of periodic cellular materials to exhibit stop and pass bands with the ability to dissipate energy through cell-level elastic instabilities. Here, we use Bloch periodic boundary conditions to compute the dispersion curves and introduce a new approach for computing wide band directionality plots. Also, we deconstruct the wave propagation behavior of this material to identify the contributions from its various structural elements by progressively building the unit cell, structural element by element, from a simple, homogeneous, isotropic primitive. Direct integration time domain analyses of a representative volume element at a few salient frequencies in the stop and pass bands are used to confirm the existence of partial band gaps in the response of the cellular material. Insights gained from the above analyses are then used to explore modifications of the unit cell that allow the user to tune the band gaps in the response of the material. We show that this material behaves like a locally resonant material that exhibits low frequency band gaps for small amplitude planar waves. Moreover, modulating the geometry or material of the central bar in the unit cell provides a path to adjust the position of the band gaps in the material response. Also, our results show that the material exhibits highly anisotropic wave propagation behavior that stems from the anisotropy in its mechanical structure. Notably, we found that unlike other multi-stable cellular materials reported in the literature, in the system studied in this work, the configurational changes in the unit cell corresponding to its different stable phases do not significantly alter the wave propagation behavior of the material. © 2019
Computational steering of CFD simulations using a grid computing environment
(Springer-Verlag France, 2015-06-08) Garcia Ruiz, Manuel Julio; Duque, J, C.; BOULANGER, PIERRE; FIGUEROA, PABLO; Mecánica Aplicada
Simulation of complex phenomena is usually a long computing process and it has been traditionally performed in batch mode on large high performance computing (HPC) systems. However, advances in computer processing and networking capabilities can now be us
Computational steering of CFD simulations using a grid computing environment
(Springer-Verlag France, 2015-01-01) García M.; Duque J.; Boulanger P.; Figueroa P.; Mecánica Aplicada
Simulation of complex phenomena is usually a long computing process and it has been traditionally performed in batch mode on large high performance computing (HPC) systems. However, advances in computer processing and networking capabilities can now be used to monitor and alter simulation parameters whilst it is running. This process is called computational steering. By combining this capability with advanced communication tools, it is now possible for a group of scientists located across the world to work collaboratively while visualising on-going simulations. This raise the possibility that researches can now share their experience and promote new ideas and solutions by exploring collaboratively the solution space of a complex simulation. In this paper, a collaborative computational steering environment specialised to solve CFD problems is presented. © 2014, Springer-Verlag France.
Construction of rational models for topographic effects and size-conditioned-response-spectra
(Elsevier Ltd, 2021-01-01) Vergara, Juan; Sierra C.; Mario Saenz; Jaramillo, Juan; Gomez, Juan; Mecánica Aplicada
We used the decay-with-distance effect of diffracted waves generated from the interaction of a plane wave with a geometric singularity, to establish the connection between the spectral response of a topographic profile and the minimum required size
Criterios sismológicos para seleccionar acelerogramas reales de la Red Nacional de Acelerógrafos de Colombia para su uso en análisis dinámicos
(Escuela de Ingeniería de Antioquia, 2012-07-01) Acevedo A.B.; Mecánica Aplicada
Utilizar acelerogramas reales para la realización de análisis dinámicos es deseable ya que contienen información real sobre la naturaleza del movimiento fuerte e indican las características variadas que diferentes sismos en lugares diversos pueden produci
Design and control of a new hydraulic test rig for small hydro turbines
(2015-01-01) BOTERO, FRANCISCO JAVIER; Mecánica Aplicada

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