Detection of stiffness reductions in concrete decks with arbitrary damage shapes using incomplete dynamic measurements / Sang-Youl Lee in Journal of engineering mechanics, Vol. 134 N° 7 (Juillet 2008)  

Public ISBD [article]  inJournal of engineering mechanics > Vol. 134 N° 7 (Juillet 2008) . - pp.567-577 Titre : Detection of stiffness reductions in concrete decks with arbitrary damage shapes using incomplete dynamic measurements Type de document : texte imprimé Auteurs : Sang-Youl Lee, Auteur ; Taehyo Park, Auteur ; George Z. Voyiadjis, Auteur Année de publication : 2010 Article en page(s) : pp.567-577 Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Damage Dynamic response Finite element method Measurement Stiffness Decks Concrete. Résumé : A new refined nondestructive evaluation technique for concrete decks with arbitrary damage shapes is presented, and its utility in detecting the location and extent of the damage using only a single dynamic measurement signal is demonstrated. Six unknown parameters are considered to determine the damage distribution, which is a modified form of the bivariate Gaussian distribution function. Using a combination of the combined finite-element method (FEM) and the advanced uniform microgenetic algorithm, the various influences of different measurement locations on the damage detection are studied. In addition, the effect of noise is simulated in order to study the influence of the measurement errors and the uncertainty of the method. The sample studies demonstrate the excellence of the proposed method from the standpoints of its computation efficiency as well as its ability to investigate the complex distribution of an arbitrary stiffness reduction. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.org/emo/resource/1/jenmdt/v134/i7/p567_s1?isAuthorized=no [article] Detection of stiffness reductions in concrete decks with arbitrary damage shapes using incomplete dynamic measurements [texte imprimé] / Sang-Youl Lee, Auteur ; Taehyo Park, Auteur ; George Z. Voyiadjis, Auteur . - 2010 . - pp.567-577. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 134 N° 7 (Juillet 2008) . - pp.567-577 Mots-clés : Damage Dynamic response Finite element method Measurement Stiffness Decks Concrete. Résumé : A new refined nondestructive evaluation technique for concrete decks with arbitrary damage shapes is presented, and its utility in detecting the location and extent of the damage using only a single dynamic measurement signal is demonstrated. Six unknown parameters are considered to determine the damage distribution, which is a modified form of the bivariate Gaussian distribution function. Using a combination of the combined finite-element method (FEM) and the advanced uniform microgenetic algorithm, the various influences of different measurement locations on the damage detection are studied. In addition, the effect of noise is simulated in order to study the influence of the measurement errors and the uncertainty of the method. The sample studies demonstrate the excellence of the proposed method from the standpoints of its computation efficiency as well as its ability to investigate the complex distribution of an arbitrary stiffness reduction. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.org/emo/resource/1/jenmdt/v134/i7/p567_s1?isAuthorized=no

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Detection of stiffness reductions in concrete decks with arbitrary damage shapes using incomplete dynamic measurements / Sang-Youl Lee in Journal of engineering mechanics, Vol 134 n° 7 (Juillet 2008)  

Public ISBD [article]  inJournal of engineering mechanics > Vol 134 n° 7 (Juillet 2008) . - pp.567–577. Titre : Detection of stiffness reductions in concrete decks with arbitrary damage shapes using incomplete dynamic measurements Type de document : texte imprimé Auteurs : Sang-Youl Lee, Auteur ; Taehyo Park, Auteur ; George Z. Voyiadjis, Auteur Année de publication : 2013 Article en page(s) : pp.567–577. Note générale : Mécaniqua appliquée Langues : Anglais (eng) Mots-clés : Damage Dynamic response Finite element method Measurement Stiffness Decks Concrete Résumé : A new refined nondestructive evaluation technique for concrete decks with arbitrary damage shapes is presented, and its utility in detecting the location and extent of the damage using only a single dynamic measurement signal is demonstrated. Six unknown parameters are considered to determine the damage distribution, which is a modified form of the bivariate Gaussian distribution function. Using a combination of the combined finite-element method (FEM) and the advanced uniform microgenetic algorithm, the various influences of different measurement locations on the damage detection are studied. In addition, the effect of noise is simulated in order to study the influence of the measurement errors and the uncertainty of the method. The sample studies demonstrate the excellence of the proposed method from the standpoints of its computation efficiency as well as its ability to investigate the complex distribution of an arbitrary stiffness reduction. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282008%29134%3A7%2856 [...] [article] Detection of stiffness reductions in concrete decks with arbitrary damage shapes using incomplete dynamic measurements [texte imprimé] / Sang-Youl Lee, Auteur ; Taehyo Park, Auteur ; George Z. Voyiadjis, Auteur . - 2013 . - pp.567–577. Mécaniqua appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol 134 n° 7 (Juillet 2008) . - pp.567–577. Mots-clés : Damage Dynamic response Finite element method Measurement Stiffness Decks Concrete Résumé : A new refined nondestructive evaluation technique for concrete decks with arbitrary damage shapes is presented, and its utility in detecting the location and extent of the damage using only a single dynamic measurement signal is demonstrated. Six unknown parameters are considered to determine the damage distribution, which is a modified form of the bivariate Gaussian distribution function. Using a combination of the combined finite-element method (FEM) and the advanced uniform microgenetic algorithm, the various influences of different measurement locations on the damage detection are studied. In addition, the effect of noise is simulated in order to study the influence of the measurement errors and the uncertainty of the method. The sample studies demonstrate the excellence of the proposed method from the standpoints of its computation efficiency as well as its ability to investigate the complex distribution of an arbitrary stiffness reduction. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282008%29134%3A7%2856 [...]

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Development and Validation of a Generalized Biaxial Hysteresis Model / Wang, Chi-Hsiang in Journal of engineering mechanics, Vol. 133 N°2 (Fevrier 2007)  

Public ISBD [article]  inJournal of engineering mechanics > Vol. 133 N°2 (Fevrier 2007) . - 141-152 p. Titre : Development and Validation of a Generalized Biaxial Hysteresis Model Titre original : Développement et Validation d'un Modèle Biaxiale Généralisé d'Hystérésis Type de document : texte imprimé Auteurs : Wang, Chi-Hsiang, Auteur ; George Z. Voyiadjis, Éditeur scientifique ; Shuenn-Yih Chang, Auteur Année de publication : 2007 Article en page(s) : 141-152 p. Note générale : Génie Mécanique Langues : Anglais (eng) Mots-clés : Biaxial loads Earthquake Inelastic action Hysteresis Degradation Dynamic analysis Charges biaxiales de tremblement terre Action non élastique Hystérésis Analyse dynamique Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Biaxial flexural interaction has been known to significantly affect, in many cases magnify, structural response in the inelastic range. Compared to uniaxial cases, the distinct characteristics of biaxial hysteresis curves often observed are negative stiffness and rounded corners of the curves near the time instants of unloading. Developed based on the widely used Bouc-Wen model, this paper presents a generalized biaxial smooth hysteresis model that takes into account the commonly observed hysteretic characteristics of strength and stiffness degradation, asymmetry in ultimate positive and negative forces, pinching, and those exclusively found in biaxial interaction. The capabilities of the developed model are illustrated by comparing the model results to the results of two cyclic and two quasi-static reinforced concrete column tests. L'interaction flexurale biaxiale a été connue pour affecter de manière significative, magnifient dans beaucoup de cas, réponse structurale dans la gamme non élastique. Comparé aux cas uniaxiaux, les caractéristiques distinctes des courbes biaxiales d'hystérésis souvent observées sont rigidité négative et coins arrondis des courbes près des instants de temps du déchargement. Développé basé sur le modèle employé couramment de Bouc Wen, cet article présente un modèle doux biaxial généralisé d'hystérésis qui tient compte des caractéristiques par hystérésis généralement observées de la dégradation de force et de rigidité, asymétrie dans les forces positives et négatives finales, pinçant, et ceux exclusivement trouvées dans l'interaction biaxiale. Les possibilités du modèle développé sont illustrées en comparant les résultats modèles aux résultats de deux essais concrets renforcés cycliques et deux quasistatiques de colonne. DEWEY : 620.1 ISSN : 0733-9399 En ligne : Chi-hsiang.Wang@csiro.au, changsy@ntut.edu.tw [article] Development and Validation of a Generalized Biaxial Hysteresis Model = Développement et Validation d'un Modèle Biaxiale Généralisé d'Hystérésis [texte imprimé] / Wang, Chi-Hsiang, Auteur ; George Z. Voyiadjis, Éditeur scientifique ; Shuenn-Yih Chang, Auteur . - 2007 . - 141-152 p. Génie Mécanique Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 133 N°2 (Fevrier 2007) . - 141-152 p. Mots-clés : Biaxial loads Earthquake Inelastic action Hysteresis Degradation Dynamic analysis Charges biaxiales de tremblement terre Action non élastique Hystérésis Analyse dynamique Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Biaxial flexural interaction has been known to significantly affect, in many cases magnify, structural response in the inelastic range. Compared to uniaxial cases, the distinct characteristics of biaxial hysteresis curves often observed are negative stiffness and rounded corners of the curves near the time instants of unloading. Developed based on the widely used Bouc-Wen model, this paper presents a generalized biaxial smooth hysteresis model that takes into account the commonly observed hysteretic characteristics of strength and stiffness degradation, asymmetry in ultimate positive and negative forces, pinching, and those exclusively found in biaxial interaction. The capabilities of the developed model are illustrated by comparing the model results to the results of two cyclic and two quasi-static reinforced concrete column tests. L'interaction flexurale biaxiale a été connue pour affecter de manière significative, magnifient dans beaucoup de cas, réponse structurale dans la gamme non élastique. Comparé aux cas uniaxiaux, les caractéristiques distinctes des courbes biaxiales d'hystérésis souvent observées sont rigidité négative et coins arrondis des courbes près des instants de temps du déchargement. Développé basé sur le modèle employé couramment de Bouc Wen, cet article présente un modèle doux biaxial généralisé d'hystérésis qui tient compte des caractéristiques par hystérésis généralement observées de la dégradation de force et de rigidité, asymétrie dans les forces positives et négatives finales, pinçant, et ceux exclusivement trouvées dans l'interaction biaxiale. Les possibilités du modèle développé sont illustrées en comparant les résultats modèles aux résultats de deux essais concrets renforcés cycliques et deux quasistatiques de colonne. DEWEY : 620.1 ISSN : 0733-9399 En ligne : Chi-hsiang.Wang@csiro.au, changsy@ntut.edu.tw

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Formulation and verification of a concrete model with strong coupling between isotropic damage and elastoplasticity and comparison to a weak coupling model / Ziad N. Taqieddin in Journal of engineering mechanics, Vol. 138 N° 5 (Mai 2012)  

Public ISBD [article]  inJournal of engineering mechanics > Vol. 138 N° 5 (Mai 2012) . - pp.530-541 Titre : Formulation and verification of a concrete model with strong coupling between isotropic damage and elastoplasticity and comparison to a weak coupling model Type de document : texte imprimé Auteurs : Ziad N. Taqieddin, Auteur ; George Z. Voyiadjis, Auteur ; Amin H. Almasri, Auteur Année de publication : 2012 Article en page(s) : pp.530-541 Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Nonlinear finite element analysis (FEA) Fracture energy based continuum damage mechanics Elastic-plastic-damage coupling Concrete material model Résumé : In this work, a new concrete model that strongly couples continuum-damage-mechanics to elastoplasticity is presented. The model incorporates a plasticity yield criterion written in terms of the nominal/damaged, rather than effective, stress space. Tensile and compressive behaviors are modeled through the damage-affected-multi-hardening nature of the plasticity yield criterion and the introduction of two (tensile and compressive) plasticity-affected isotropic damage initiation/growth criteria, where plasticity variables are added to the definition of the tensile and compressive growth functions of damage. A nonassociative plastic flow rule is used to control inelastic dilatancy. Specific expressions of the elastic/damage and plastic/damage components of the Helmholtz free energy function are presented. The constitutive equations of the model are consistently derived within a sound framework of irreversible thermodynamics. These free energy expressions are used to define three plasticity and damage interconnected dissipation mechanisms, one plasticity mechanism and two damage mechanisms. The elastic-plastic-damage, elastic-plastic, and elastic-damage tangent operators are also derived. A computational algorithm for the numerical integration of the constitutive equations is proposed on the basis of the doubly passive predictor–plastic-damage corrector approach. The model is implemented in the Finite Element (FE) analysis software ABAQUS through a user defined material subroutine (UMAT). Two- and three-dimensional verification examples are carried out to demonstrate the effectiveness and robustness of the proposed model in producing results that depict experimentally observed concrete behaviors. The results of the proposed model are compared with those of a weak coupling concrete model recently presented by the authors, in which damage was incorporated in the elastic formulation whereas plasticity remained in the effective stress space. The comparison shows the effect of strong-coupling on increasing/accelerating the degradation of concrete when the same material parameters of the weak coupling model are used. The results of the proposed model are also compared with those of well known strong-coupling models available in contemporary literature. To reduce the sensitivity of the nonlinear FE analysis of concrete structures to the refinement of the FE meshes, the damage density parameters are defined to include embedded dimensionless coefficients that are related to concrete’s fracture energies (in tension and compression) and to the geometrical characteristic length provided by ABAQUS software during the analysis. The conclusions drawn from this work clearly indicate the adequacy of the model to describe the different stages of concrete behavior and stiffness and strength degradations attributable to elastoplasticity-affected damage growth. They also show that the model can be further improved and equipped with nonlocal measures to enhance its future performance. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29EM.1943-7889.0000344 [article] Formulation and verification of a concrete model with strong coupling between isotropic damage and elastoplasticity and comparison to a weak coupling model [texte imprimé] / Ziad N. Taqieddin, Auteur ; George Z. Voyiadjis, Auteur ; Amin H. Almasri, Auteur . - 2012 . - pp.530-541. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 138 N° 5 (Mai 2012) . - pp.530-541 Mots-clés : Nonlinear finite element analysis (FEA) Fracture energy based continuum damage mechanics Elastic-plastic-damage coupling Concrete material model Résumé : In this work, a new concrete model that strongly couples continuum-damage-mechanics to elastoplasticity is presented. The model incorporates a plasticity yield criterion written in terms of the nominal/damaged, rather than effective, stress space. Tensile and compressive behaviors are modeled through the damage-affected-multi-hardening nature of the plasticity yield criterion and the introduction of two (tensile and compressive) plasticity-affected isotropic damage initiation/growth criteria, where plasticity variables are added to the definition of the tensile and compressive growth functions of damage. A nonassociative plastic flow rule is used to control inelastic dilatancy. Specific expressions of the elastic/damage and plastic/damage components of the Helmholtz free energy function are presented. The constitutive equations of the model are consistently derived within a sound framework of irreversible thermodynamics. These free energy expressions are used to define three plasticity and damage interconnected dissipation mechanisms, one plasticity mechanism and two damage mechanisms. The elastic-plastic-damage, elastic-plastic, and elastic-damage tangent operators are also derived. A computational algorithm for the numerical integration of the constitutive equations is proposed on the basis of the doubly passive predictor–plastic-damage corrector approach. The model is implemented in the Finite Element (FE) analysis software ABAQUS through a user defined material subroutine (UMAT). Two- and three-dimensional verification examples are carried out to demonstrate the effectiveness and robustness of the proposed model in producing results that depict experimentally observed concrete behaviors. The results of the proposed model are compared with those of a weak coupling concrete model recently presented by the authors, in which damage was incorporated in the elastic formulation whereas plasticity remained in the effective stress space. The comparison shows the effect of strong-coupling on increasing/accelerating the degradation of concrete when the same material parameters of the weak coupling model are used. The results of the proposed model are also compared with those of well known strong-coupling models available in contemporary literature. To reduce the sensitivity of the nonlinear FE analysis of concrete structures to the refinement of the FE meshes, the damage density parameters are defined to include embedded dimensionless coefficients that are related to concrete’s fracture energies (in tension and compression) and to the geometrical characteristic length provided by ABAQUS software during the analysis. The conclusions drawn from this work clearly indicate the adequacy of the model to describe the different stages of concrete behavior and stiffness and strength degradations attributable to elastoplasticity-affected damage growth. They also show that the model can be further improved and equipped with nonlocal measures to enhance its future performance. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29EM.1943-7889.0000344

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Physically based constitutive model for body centered cubic metals with applications to iron / Amin Almasri in Journal of engineering mechanics, Vol. 134 N° 7 (Juillet 2008)  

Public ISBD [article]  inJournal of engineering mechanics > Vol. 134 N° 7 (Juillet 2008) . - pp.521-529 Titre : Physically based constitutive model for body centered cubic metals with applications to iron Type de document : texte imprimé Auteurs : Amin Almasri, Auteur ; George Z. Voyiadjis, Auteur Année de publication : 2010 Article en page(s) : pp.521-529 Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Constitute models Strain rate Temperature Iron. Résumé : A constitutive model is developed in this work to describe the mechanical behavior of body centered cubic metals under a wide range of strain rates and temperatures. The model is based on macromechanical state variables such as stress, strain, and material constants that include threshold and transition temperature as well as micromechanical terms such as mobile dislocation density and burgers vector. The principle of the activation energy and its dependence on temperature, strain rate, and stress is the key point in this proposed model. The model is used to simulate the experimental behavior of pure iron at various temperatures and strain rates in order to obtain the different model parameters. The model shows good capability in capturing the coupling between strain rate and temperature, plastic strain and strain rate, and plastic strain and temperature. The model is used to characterize the hardness of iron at low and high strain rates for a representative strain of 8%. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.org/emo/resource/1/jenmdt/v134/i7/p521_s1?isAuthorized=no [article] Physically based constitutive model for body centered cubic metals with applications to iron [texte imprimé] / Amin Almasri, Auteur ; George Z. Voyiadjis, Auteur . - 2010 . - pp.521-529. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 134 N° 7 (Juillet 2008) . - pp.521-529 Mots-clés : Constitute models Strain rate Temperature Iron. Résumé : A constitutive model is developed in this work to describe the mechanical behavior of body centered cubic metals under a wide range of strain rates and temperatures. The model is based on macromechanical state variables such as stress, strain, and material constants that include threshold and transition temperature as well as micromechanical terms such as mobile dislocation density and burgers vector. The principle of the activation energy and its dependence on temperature, strain rate, and stress is the key point in this proposed model. The model is used to simulate the experimental behavior of pure iron at various temperatures and strain rates in order to obtain the different model parameters. The model shows good capability in capturing the coupling between strain rate and temperature, plastic strain and strain rate, and plastic strain and temperature. The model is used to characterize the hardness of iron at low and high strain rates for a representative strain of 8%. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.org/emo/resource/1/jenmdt/v134/i7/p521_s1?isAuthorized=no

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Physically based constitutive model for body centered cubic metals with applications to iron / Amin Almasri in Journal of engineering mechanics, Vol 134 n° 7 (Juillet 2008)  

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Recurrent Single Delaminated Beam Model for Vibration Analysis of Multidelaminated Beams / Taehyo Park in Journal of engineering mechanics, Vol. 130 N°9 (Septembre 2004)

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Thermodynamic Consistent Formulations of Viscoplastic Deformations in FCC Metals / Abed, Farid in Journal of engineering mechanics, Vol. 133 N°1 (Janvier 2007)  

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Unified Sand Model Based on the Critical State and Generalized Plasticity / Hoe I. Ling in Journal of engineering mechanics, Vol. 132 N°12 (Decembre 2006)  

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Upper-Bound Solutions for Rigid-Plastic Beams and Plates of Large Deflections by Variation Principles / Belenkiy, L. M. in Journal of engineering mechanics, Vol. 133 N°1 (Janvier 2007)  

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Variable material length scale associated with nanoindentation experiments / George Z. Voyiadjis in Journal of engineering mechanics, Vol. 135 N°3 (Mars 2009)  

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