Acceleration tracking performance of the UCSD-NEES shake table / J. Enrique Luco in Journal of structural engineering, Vol. 136 N° 5 (Mai 2010)  

Public ISBD [article]  inJournal of structural engineering > Vol. 136 N° 5 (Mai 2010) . - pp. 481-490 Titre : Acceleration tracking performance of the UCSD-NEES shake table Type de document : texte imprimé Auteurs : J. Enrique Luco, Auteur ; Ozcelik, O., Auteur ; Joel P. Conte, Auteur Année de publication : 2011 Article en page(s) : pp. 481-490 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Dynamics Shake table Control Full-scale structural tests Earthquake simulation Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : The main objective of this paper is to investigate the tracking (signal reproduction) capability of the UCSD-NEES shake table system through a series of broadband and harmonic experiments with different tuning and test amplitudes. The second objective is to obtain quantitative relations between different measures of the signal reproduction error and the amplitude of the reference excitation used to tune the shake table controller. These relations can be used as guidelines in planning of future seismic tests on the UCSD-NEES shake table or on large shake tables with similar controllers. The third objective is to evaluate the effectiveness of the existing iterative correction/tuning procedure for the UCSD-NEES shake table. The final objective of the paper is to propose some improvements to the current shake table tuning practice. DEWEY : 624.17 ISSN : 0733-9445 En ligne : http://ascelibrary.org/sto/resource/1/jsendh/v136/i5/p481_s1?isAuthorized=no [article] Acceleration tracking performance of the UCSD-NEES shake table [texte imprimé] / J. Enrique Luco, Auteur ; Ozcelik, O., Auteur ; Joel P. Conte, Auteur . - 2011 . - pp. 481-490. Génie Civil Langues : Anglais (eng) in Journal of structural engineering > Vol. 136 N° 5 (Mai 2010) . - pp. 481-490 Mots-clés : Dynamics Shake table Control Full-scale structural tests Earthquake simulation Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : The main objective of this paper is to investigate the tracking (signal reproduction) capability of the UCSD-NEES shake table system through a series of broadband and harmonic experiments with different tuning and test amplitudes. The second objective is to obtain quantitative relations between different measures of the signal reproduction error and the amplitude of the reference excitation used to tune the shake table controller. These relations can be used as guidelines in planning of future seismic tests on the UCSD-NEES shake table or on large shake tables with similar controllers. The third objective is to evaluate the effectiveness of the existing iterative correction/tuning procedure for the UCSD-NEES shake table. The final objective of the paper is to propose some improvements to the current shake table tuning practice. DEWEY : 624.17 ISSN : 0733-9445 En ligne : http://ascelibrary.org/sto/resource/1/jsendh/v136/i5/p481_s1?isAuthorized=no

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Approximate boundaries for finite - element models of static soil – foundation interaction problems / Carlos M. Mozos in Journal of engineering mechanics, Vol. 137 N° 10 (Octobre 2011)  

Public ISBD [article]  inJournal of engineering mechanics > Vol. 137 N° 10 (Octobre 2011) . - pp.648-659 Titre : Approximate boundaries for finite - element models of static soil – foundation interaction problems Type de document : texte imprimé Auteurs : Carlos M. Mozos, Auteur ; J. Enrique Luco, Auteur Année de publication : 2012 Article en page(s) : pp.648-659 Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Soil-structure interactions Soil-pile Finite element method Boundaries Résumé : In this paper, we examine the use of boundary springs as approximate external boundary conditions for the typical soil islands encountered in finite-element (FE) models of soil–foundation interaction problems. We present a set of simple uniformly distributed boundary springs and a set of variable boundary springs that account for the lateral distribution of contact forces between the foundation and the soil. We evaluate the accuracy of the approach for shallow foundations resting on soil islands of different dimensions. It is shown that significantly smaller errors can be achieved with these boundary springs than those obtained when fixed-fixed or fixed-free external boundary conditions are used. We present an iterative approach to determine the boundary springs for cases in which extremely small soil islands are required. Although the approach suggested to determine the boundary springs is best suited to shallow foundations, good results are also obtained for pile foundations. The approach presented applies to a uniform elastic half-space, but extensions to layered media are possible. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.org/emo/resource/1/jenmdt/v137/i10/p648_s1?isAuthorized=no [article] Approximate boundaries for finite - element models of static soil – foundation interaction problems [texte imprimé] / Carlos M. Mozos, Auteur ; J. Enrique Luco, Auteur . - 2012 . - pp.648-659. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 137 N° 10 (Octobre 2011) . - pp.648-659 Mots-clés : Soil-structure interactions Soil-pile Finite element method Boundaries Résumé : In this paper, we examine the use of boundary springs as approximate external boundary conditions for the typical soil islands encountered in finite-element (FE) models of soil–foundation interaction problems. We present a set of simple uniformly distributed boundary springs and a set of variable boundary springs that account for the lateral distribution of contact forces between the foundation and the soil. We evaluate the accuracy of the approach for shallow foundations resting on soil islands of different dimensions. It is shown that significantly smaller errors can be achieved with these boundary springs than those obtained when fixed-fixed or fixed-free external boundary conditions are used. We present an iterative approach to determine the boundary springs for cases in which extremely small soil islands are required. Although the approach suggested to determine the boundary springs is best suited to shallow foundations, good results are also obtained for pile foundations. The approach presented applies to a uniform elastic half-space, but extensions to layered media are possible. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.org/emo/resource/1/jenmdt/v137/i10/p648_s1?isAuthorized=no

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Effect of hanger flexibility on dynamic response of suspension bridges / José Turmo in Journal of engineering mechanics, Vol. 136 N° 12 (Décembre 2010)  

Public ISBD [article]  inJournal of engineering mechanics > Vol. 136 N° 12 (Décembre 2010) . - pp.1444-1459 Titre : Effect of hanger flexibility on dynamic response of suspension bridges Type de document : texte imprimé Auteurs : José Turmo, Auteur ; J. Enrique Luco, Auteur Année de publication : 2011 Article en page(s) : pp.1444-1459 Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Dynamic loads Bridges suspension Continuum mechanics Vibration. Résumé : Linearized continuum models of a suspended span with unloaded backstays and of a symmetric three-span suspension bridge are used to study the effects of the flexibility of the hangers on the vertical vibrations of suspension bridges. The models include elastic parabolic cables, flexible distributed hangers with variable length, and a stiffening girder represented by an elastic beam. It is shown that the free vibrations of a suspended span with unloaded backstays are controlled by five dimensionless parameters, while six dimensionless parameters control the response of a symmetric three-span suspension bridge. The results indicate that the flexibility of the hangers has a significant effect on the natural frequencies of the higher modes only when the relative stiffness of the girder is very high. The effects of hanger flexibility on the response of a suspension bridge to localized impulsive loads are also found to be small. These findings confirm the traditional, albeit previously untested, assumption of inextensible hangers. Finally, the threshold amplitudes of free vibrations that would result in the incipient slackening of the hangers are determined. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.org/emo/resource/1/jenmdt/v136/i12/p1444_s1?isAuthorized=no [article] Effect of hanger flexibility on dynamic response of suspension bridges [texte imprimé] / José Turmo, Auteur ; J. Enrique Luco, Auteur . - 2011 . - pp.1444-1459. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 136 N° 12 (Décembre 2010) . - pp.1444-1459 Mots-clés : Dynamic loads Bridges suspension Continuum mechanics Vibration. Résumé : Linearized continuum models of a suspended span with unloaded backstays and of a symmetric three-span suspension bridge are used to study the effects of the flexibility of the hangers on the vertical vibrations of suspension bridges. The models include elastic parabolic cables, flexible distributed hangers with variable length, and a stiffening girder represented by an elastic beam. It is shown that the free vibrations of a suspended span with unloaded backstays are controlled by five dimensionless parameters, while six dimensionless parameters control the response of a symmetric three-span suspension bridge. The results indicate that the flexibility of the hangers has a significant effect on the natural frequencies of the higher modes only when the relative stiffness of the girder is very high. The effects of hanger flexibility on the response of a suspension bridge to localized impulsive loads are also found to be small. These findings confirm the traditional, albeit previously untested, assumption of inextensible hangers. Finally, the threshold amplitudes of free vibrations that would result in the incipient slackening of the hangers are determined. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.org/emo/resource/1/jenmdt/v136/i12/p1444_s1?isAuthorized=no

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Experimental characterization, modeling and identification of the NEES-UCSD shake table mechanical system / Ozcelik, O. in Earthquake engineering structural dynamics, Vol. 37 N°2 (Fevrier 2008)  

Public ISBD [article]  inEarthquake engineering structural dynamics > Vol. 37 N°2 (Fevrier 2008) . - 243 - 264 p. Titre : Experimental characterization, modeling and identification of the NEES-UCSD shake table mechanical system Type de document : texte imprimé Auteurs : Ozcelik, O., Auteur ; Restrepo, J. I., Auteur ; Trombetti, T. L., Auteur ; Joel P. Conte, Auteur ; J. Enrique Luco, Auteur Année de publication : 2008 Article en page(s) : 243 - 264 p. Note générale : Génie civil Langues : Anglais (eng) Mots-clés : Shake table Dynamics Modeling Tableaux de secousse Dynamique Modélisation Index. décimale : 624.151 Résumé : This paper proposes a simple conceptual mathematical model for the mechanical components of the NEES-UCSD large high-performance outdoor shaking table and focuses on the identification of the parameters of the model by using an extensive set of experimental data. An identification approach based on the measured hysteresis response is used to determine the fundamental model parameters including the effective horizontal mass, effective horizontal stiffness of the table, and the coefficients of the classical Coulomb friction and viscous damping elements representing the various dissipative forces in the system. The effectiveness of the proposed conceptual model is verified through a comparison of analytical predictions with experimental results for various tests conducted on the system. The resulting mathematical model will be used in future studies to model the mechanical components of the shake table in a comprehensive physics-based model of the entire mechanical, hydraulic, and electronic system. Cet article propose un modèle mathématique conceptuel simple pour les composants mécaniques de la grande table de secousse extérieure à rendement élevé et des foyers de NEES-UCSD sur l'identification des paramètres du modèle en employant un ensemble étendu de données expérimentales. Une approche d'identification basée sur la réponse mesurée d'hystérésis est employée pour déterminer les paramètres modèles fondamentaux comprenant la masse horizontale efficace, la rigidité horizontale efficace de la table, et les coefficients du frottement classique de coulomb et des éléments d'atténuation visqueux représentant les diverses forces dispersives dans le système. L'efficacité du modèle conceptuel proposé est vérifiée par une comparaison des prévisions analytiques avec des résultats expérimentaux pour différents essais effectués sur le système. Le modèle mathématique résultant sera employé dans de futures études pour modeler les composants mécaniques de la table de secousse dans un modèle physique-basé complet du système mécanique, hydraulique, et électronique entier. DEWEY : 551.2 ISSN : 0098-8847 RAMEAU : Secousse -- Modélisation En ligne : http://www3.interscience.wiley.com/journal [article] Experimental characterization, modeling and identification of the NEES-UCSD shake table mechanical system [texte imprimé] / Ozcelik, O., Auteur ; Restrepo, J. I., Auteur ; Trombetti, T. L., Auteur ; Joel P. Conte, Auteur ; J. Enrique Luco, Auteur . - 2008 . - 243 - 264 p. Génie civil Langues : Anglais (eng) in Earthquake engineering structural dynamics > Vol. 37 N°2 (Fevrier 2008) . - 243 - 264 p. Mots-clés : Shake table Dynamics Modeling Tableaux de secousse Dynamique Modélisation Index. décimale : 624.151 Résumé : This paper proposes a simple conceptual mathematical model for the mechanical components of the NEES-UCSD large high-performance outdoor shaking table and focuses on the identification of the parameters of the model by using an extensive set of experimental data. An identification approach based on the measured hysteresis response is used to determine the fundamental model parameters including the effective horizontal mass, effective horizontal stiffness of the table, and the coefficients of the classical Coulomb friction and viscous damping elements representing the various dissipative forces in the system. The effectiveness of the proposed conceptual model is verified through a comparison of analytical predictions with experimental results for various tests conducted on the system. The resulting mathematical model will be used in future studies to model the mechanical components of the shake table in a comprehensive physics-based model of the entire mechanical, hydraulic, and electronic system. Cet article propose un modèle mathématique conceptuel simple pour les composants mécaniques de la grande table de secousse extérieure à rendement élevé et des foyers de NEES-UCSD sur l'identification des paramètres du modèle en employant un ensemble étendu de données expérimentales. Une approche d'identification basée sur la réponse mesurée d'hystérésis est employée pour déterminer les paramètres modèles fondamentaux comprenant la masse horizontale efficace, la rigidité horizontale efficace de la table, et les coefficients du frottement classique de coulomb et des éléments d'atténuation visqueux représentant les diverses forces dispersives dans le système. L'efficacité du modèle conceptuel proposé est vérifiée par une comparaison des prévisions analytiques avec des résultats expérimentaux pour différents essais effectués sur le système. Le modèle mathématique résultant sera employé dans de futures études pour modeler les composants mécaniques de la table de secousse dans un modèle physique-basé complet du système mécanique, hydraulique, et électronique entier. DEWEY : 551.2 ISSN : 0098-8847 RAMEAU : Secousse -- Modélisation En ligne : http://www3.interscience.wiley.com/journal

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Identification of the mechanical subsystem of the NEES-UCSD shake table by a least-squares approach / Ozcelik, O. in Journal of engineering mechanics, Vol. 134 N°1 (Janvier 2008)  

Public ISBD [article]  inJournal of engineering mechanics > Vol. 134 N°1 (Janvier 2008) . - pp.23–34. Titre : Identification of the mechanical subsystem of the NEES-UCSD shake table by a least-squares approach Type de document : texte imprimé Auteurs : Ozcelik, O., Auteur ; J. Enrique Luco, Auteur ; Joel P. Conte, Auteur Année de publication : 2008 Article en page(s) : pp.23–34. Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Shake table tests Least squares method Earthquakes Simulation. Résumé : A least-squares method is used to determine the fundamental parameters of a simple mathematical model for the mechanical subsystem of the NEES-UCSD large high performance outdoor shaking table. The parameters identified include the effective horizontal mass, the effective horizontal stiffness, and the coefficient of the classical Coulomb friction and viscous damping elements representing the various dissipative forces in the system. The values obtained for these parameters are validated by comparisons with previous results based on an alternative identification method applicable only to periodic tests and by comparisons with experimental data obtained during earthquake simulation tests and harmonic steady-state tests. The proposed identification approach works well for periodic sinusoidal and triangular tests, earthquake simulation tests, and white noise tests with table root mean square above 10% of gravity. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282008%29134%3A1%2823 [...] [article] Identification of the mechanical subsystem of the NEES-UCSD shake table by a least-squares approach [texte imprimé] / Ozcelik, O., Auteur ; J. Enrique Luco, Auteur ; Joel P. Conte, Auteur . - 2008 . - pp.23–34. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 134 N°1 (Janvier 2008) . - pp.23–34. Mots-clés : Shake table tests Least squares method Earthquakes Simulation. Résumé : A least-squares method is used to determine the fundamental parameters of a simple mathematical model for the mechanical subsystem of the NEES-UCSD large high performance outdoor shaking table. The parameters identified include the effective horizontal mass, the effective horizontal stiffness, and the coefficient of the classical Coulomb friction and viscous damping elements representing the various dissipative forces in the system. The values obtained for these parameters are validated by comparisons with previous results based on an alternative identification method applicable only to periodic tests and by comparisons with experimental data obtained during earthquake simulation tests and harmonic steady-state tests. The proposed identification approach works well for periodic sinusoidal and triangular tests, earthquake simulation tests, and white noise tests with table root mean square above 10% of gravity. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282008%29134%3A1%2823 [...]

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