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Détail de l'auteur
Auteur M. H. El Naggar
Documents disponibles écrits par cet auteur
Affiner la rechercheInfluence of pore fluid viscosity on the dynamic properties of an artificial clay / A. Turan in Journal of geotechnical and geoenvironmental engineering, Vol. 137 N° 12 (Décembre 2011)
in Journal of geotechnical and geoenvironmental engineering > Vol. 137 N° 12 (Décembre 2011) . - pp. 1190-1201
Titre : Influence of pore fluid viscosity on the dynamic properties of an artificial clay Type de document : texte imprimé Auteurs : A. Turan, Auteur ; S. D. Hinchberger, Auteur ; M. H. El Naggar, Auteur Année de publication : 2012 Article en page(s) : pp. 1190-1201 Note générale : Géotechnique Langues : Anglais (eng) Mots-clés : Geotechnical models Soil dynamics Clays Damping Shear Thermal properties Cyclic tests Résumé : This paper presents the results of vane shear, laboratory compaction, isotropic consolidation, cyclic triaxial, bender element, and resonant-column tests that were performed to characterize the dynamic properties of an artificial soil called modified glyben. Modified glyben comprises a mixture of glycerin, water, and bentonite that can be used in scaled model tests performed at 1 G or n G in a centrifuge to study seismic soil–structure interaction. The results described in this paper show that the vane shear strength, coefficient of consolidation, dynamic modulus, and damping ratio are strongly influenced by the viscosity of the pore fluid which can be varied by altering the ratio of glycerin-to-water. In addition, the properties of modified glyben are stable during prolonged exposure to air and multiple largestrain load cycles making it a suitable model soil for scaled model tests involving seismic soil–structure interaction. DEWEY : 624.1 ISSN : 1090-0241 En ligne : http://ascelibrary.org/gto/resource/1/jggefk/v137/i12/p1190_s1?isAuthorized=no [article] Influence of pore fluid viscosity on the dynamic properties of an artificial clay [texte imprimé] / A. Turan, Auteur ; S. D. Hinchberger, Auteur ; M. H. El Naggar, Auteur . - 2012 . - pp. 1190-1201.
Géotechnique
Langues : Anglais (eng)
in Journal of geotechnical and geoenvironmental engineering > Vol. 137 N° 12 (Décembre 2011) . - pp. 1190-1201
Mots-clés : Geotechnical models Soil dynamics Clays Damping Shear Thermal properties Cyclic tests Résumé : This paper presents the results of vane shear, laboratory compaction, isotropic consolidation, cyclic triaxial, bender element, and resonant-column tests that were performed to characterize the dynamic properties of an artificial soil called modified glyben. Modified glyben comprises a mixture of glycerin, water, and bentonite that can be used in scaled model tests performed at 1 G or n G in a centrifuge to study seismic soil–structure interaction. The results described in this paper show that the vane shear strength, coefficient of consolidation, dynamic modulus, and damping ratio are strongly influenced by the viscosity of the pore fluid which can be varied by altering the ratio of glycerin-to-water. In addition, the properties of modified glyben are stable during prolonged exposure to air and multiple largestrain load cycles making it a suitable model soil for scaled model tests involving seismic soil–structure interaction. DEWEY : 624.1 ISSN : 1090-0241 En ligne : http://ascelibrary.org/gto/resource/1/jggefk/v137/i12/p1190_s1?isAuthorized=no
in Journal of geotechnical and geoenvironmental engineering > Vol. 134 n°9 (Septembre 2008) . - pp. 1319–1326
Titre : Measurement of frequency-dependent dynamic properties of soils using the resonant-column device Type de document : texte imprimé Auteurs : Z. H. Khan, Auteur ; G. Cascante, Auteur ; M. H. El Naggar, Auteur Année de publication : 2008 Article en page(s) : pp. 1319–1326 Note générale : Geotechnical and geoenvironmental engineering Langues : Anglais (eng) Mots-clés : Resonance Velocity Damping Soil dynamics Soil properties Soil tests Résumé : Dynamic properties of soils are commonly evaluated at resonance; thus, their variation with frequency is difficult to measure. A nonresonance (NR) method has been recently used for testing soils at low frequencies and strain levels below the linear threshold shear strain. However, the NR method has not been validated with the standard resonant method for different shear strain levels. In this study, the NR method is used to measure the dynamic properties of soils at low and midstrain levels for a maximum frequency bandwidth between 5 and 100Hz using the resonant-column device. A new transfer function (NTF) equation is introduced to compare the dynamic properties measured using the NR method and the conventional transfer function approach. Experimental results for two sands and a sand–bentonite–mud mixture are presented for different strain and stress confinement levels. Results from the NR method compare well with the standard resonant column method at the resonant frequency if the strain levels are the same. The NTF approach can be used to measure the dependence of phase velocity of shear waves with frequency. However, the NTF method cannot be used to measure the variation of material damping with frequency. On the other hand, the NR method can be used to measure the degradation curves of wave velocity and material damping ratio as a function of frequency. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282008%29134%3A9%2813 [...] [article] Measurement of frequency-dependent dynamic properties of soils using the resonant-column device [texte imprimé] / Z. H. Khan, Auteur ; G. Cascante, Auteur ; M. H. El Naggar, Auteur . - 2008 . - pp. 1319–1326.
Geotechnical and geoenvironmental engineering
Langues : Anglais (eng)
in Journal of geotechnical and geoenvironmental engineering > Vol. 134 n°9 (Septembre 2008) . - pp. 1319–1326
Mots-clés : Resonance Velocity Damping Soil dynamics Soil properties Soil tests Résumé : Dynamic properties of soils are commonly evaluated at resonance; thus, their variation with frequency is difficult to measure. A nonresonance (NR) method has been recently used for testing soils at low frequencies and strain levels below the linear threshold shear strain. However, the NR method has not been validated with the standard resonant method for different shear strain levels. In this study, the NR method is used to measure the dynamic properties of soils at low and midstrain levels for a maximum frequency bandwidth between 5 and 100Hz using the resonant-column device. A new transfer function (NTF) equation is introduced to compare the dynamic properties measured using the NR method and the conventional transfer function approach. Experimental results for two sands and a sand–bentonite–mud mixture are presented for different strain and stress confinement levels. Results from the NR method compare well with the standard resonant column method at the resonant frequency if the strain levels are the same. The NTF approach can be used to measure the dependence of phase velocity of shear waves with frequency. However, the NTF method cannot be used to measure the variation of material damping with frequency. On the other hand, the NR method can be used to measure the degradation curves of wave velocity and material damping ratio as a function of frequency. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282008%29134%3A9%2813 [...]
in Journal of geotechnical and geoenvironmental engineering > Vol. 134 n°9 (Septembre 2008) . - pp. 1319–1326
Titre : Measurement of frequency-dependent dynamic properties of soils using the resonant-column device Type de document : texte imprimé Auteurs : Z. H. Khan, Auteur ; G. Cascante, Auteur ; M. H. El Naggar, Auteur Année de publication : 2008 Article en page(s) : pp. 1319–1326 Note générale : Geotechnical and geoenvironmental engineering Langues : Anglais (eng) Mots-clés : Resonance Velocity Damping Soil dynamics Soil properties Soil tests Résumé : Dynamic properties of soils are commonly evaluated at resonance; thus, their variation with frequency is difficult to measure. A nonresonance (NR) method has been recently used for testing soils at low frequencies and strain levels below the linear threshold shear strain. However, the NR method has not been validated with the standard resonant method for different shear strain levels. In this study, the NR method is used to measure the dynamic properties of soils at low and midstrain levels for a maximum frequency bandwidth between 5 and 100Hz using the resonant-column device. A new transfer function (NTF) equation is introduced to compare the dynamic properties measured using the NR method and the conventional transfer function approach. Experimental results for two sands and a sand–bentonite–mud mixture are presented for different strain and stress confinement levels. Results from the NR method compare well with the standard resonant column method at the resonant frequency if the strain levels are the same. The NTF approach can be used to measure the dependence of phase velocity of shear waves with frequency. However, the NTF method cannot be used to measure the variation of material damping with frequency. On the other hand, the NR method can be used to measure the degradation curves of wave velocity and material damping ratio as a function of frequency. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282008%29134%3A9%2813 [...] [article] Measurement of frequency-dependent dynamic properties of soils using the resonant-column device [texte imprimé] / Z. H. Khan, Auteur ; G. Cascante, Auteur ; M. H. El Naggar, Auteur . - 2008 . - pp. 1319–1326.
Geotechnical and geoenvironmental engineering
Langues : Anglais (eng)
in Journal of geotechnical and geoenvironmental engineering > Vol. 134 n°9 (Septembre 2008) . - pp. 1319–1326
Mots-clés : Resonance Velocity Damping Soil dynamics Soil properties Soil tests Résumé : Dynamic properties of soils are commonly evaluated at resonance; thus, their variation with frequency is difficult to measure. A nonresonance (NR) method has been recently used for testing soils at low frequencies and strain levels below the linear threshold shear strain. However, the NR method has not been validated with the standard resonant method for different shear strain levels. In this study, the NR method is used to measure the dynamic properties of soils at low and midstrain levels for a maximum frequency bandwidth between 5 and 100Hz using the resonant-column device. A new transfer function (NTF) equation is introduced to compare the dynamic properties measured using the NR method and the conventional transfer function approach. Experimental results for two sands and a sand–bentonite–mud mixture are presented for different strain and stress confinement levels. Results from the NR method compare well with the standard resonant column method at the resonant frequency if the strain levels are the same. The NTF approach can be used to measure the dependence of phase velocity of shear waves with frequency. However, the NTF method cannot be used to measure the variation of material damping with frequency. On the other hand, the NR method can be used to measure the degradation curves of wave velocity and material damping ratio as a function of frequency. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282008%29134%3A9%2813 [...]
in Journal of geotechnical and geoenvironmental engineering > Vol. 135 N°2 (Février 2009) . - pp. 280–290
Titre : Mechanical characterization of an artificial clay Type de document : texte imprimé Auteurs : A. Turan, Auteur ; S. D. Hinchberger, Auteur ; M. H. El Naggar, Auteur Année de publication : 2009 Article en page(s) : pp. 280–290 Note générale : Geotechnical and geoenvironmental engineering Langues : Anglais (eng) Mots-clés : Geotechnical models Soil dynamics Clays Damping Shear Thermal factors Cyclic tests Résumé : Glyben is an artificial soil comprising bentonite mixed with glycerin that has been used recently in scaled model tests to study seismic soil structure interaction. In spite of recent interest in glyben, factors affecting the dynamic properties of this material have not been well established. This paper presents the results of vane shear tests, cyclic triaxial tests, resonant column tests and bender element tests undertaken to characterize the dynamic properties of glyben. The results show that the modulus ratio of glyben decreases with increasing shear strain amplitude similar to that observed for natural clays. However, there are significant thixotropic changes in the properties of glyben after mixing bentonite with glycerin. In addition, glyben exhibits time-dependent volumetric compression after the application of isotropic consolidation pressure, the damping ratio of glyben is higher than that of natural clays and the dynamic properties of glyben are strongly influenced by temperature. These factors should be considered when interpreting the results of scaled physical model tests using glyben. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282009%29135%3A2%2828 [...] [article] Mechanical characterization of an artificial clay [texte imprimé] / A. Turan, Auteur ; S. D. Hinchberger, Auteur ; M. H. El Naggar, Auteur . - 2009 . - pp. 280–290.
Geotechnical and geoenvironmental engineering
Langues : Anglais (eng)
in Journal of geotechnical and geoenvironmental engineering > Vol. 135 N°2 (Février 2009) . - pp. 280–290
Mots-clés : Geotechnical models Soil dynamics Clays Damping Shear Thermal factors Cyclic tests Résumé : Glyben is an artificial soil comprising bentonite mixed with glycerin that has been used recently in scaled model tests to study seismic soil structure interaction. In spite of recent interest in glyben, factors affecting the dynamic properties of this material have not been well established. This paper presents the results of vane shear tests, cyclic triaxial tests, resonant column tests and bender element tests undertaken to characterize the dynamic properties of glyben. The results show that the modulus ratio of glyben decreases with increasing shear strain amplitude similar to that observed for natural clays. However, there are significant thixotropic changes in the properties of glyben after mixing bentonite with glycerin. In addition, glyben exhibits time-dependent volumetric compression after the application of isotropic consolidation pressure, the damping ratio of glyben is higher than that of natural clays and the dynamic properties of glyben are strongly influenced by temperature. These factors should be considered when interpreting the results of scaled physical model tests using glyben. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282009%29135%3A2%2828 [...]
in Earthquake engineering structural dynamics > Vol. 36 N°11 (Octobre 2007) . - 1581-1604 p.
Titre : On the performance of SCF in seismic isolation of the interior equipment of buildings Type de document : texte imprimé Auteurs : Moussa Hamidi, Auteur ; M. H. El Naggar, Auteur Article en page(s) : 1581-1604 p. Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : SCF • isolated raised floor • equipment response • primary structure • secondary system isolés plancher surélevé équipement de réponse structure primaire système secondaire Index. décimale : 624.151 Résumé : The dynamic response of equipment mounted on an isolated raised floor inside a building while the primary fixed base structure is subjected to harmonic and earthquake ground motions is numerically investigated. Sliding concave foundation (SCF) system is utilized for isolating the raised floor. The equations of motion for a MDOF shear building containing a SCF isolated raised floor with a mounted equipment are developed and the rigid link method is utilized to handle the non-linearity of the system. The equipment, which can be modelled as a SDOF or MDOF system, may represent a critical computer unit or telecommunication processing system. SCF can be used easily to achieve the desired long period, necessary for protecting sensitive equipment. In this investigation, the ability of SCF in reducing the acceleration level experienced by the equipment inside a building is demonstrated while the lateral displacement is still within an acceptable range. The analysis considered the case of equipment housed in the upper floors of a building where the acceleration is amplified and the motion contains strong components at long periods. For this purpose, different excitations including both harmonic and real earthquake ground motions are employed and the performance of the system is evaluated.
La réponse dynamique de l'équipement monté sur un plancher surélevé isolé dans un bâtiment alors que la première structure de base fixe est soumis à des harmoniques et les tremblements de terre mouvements du sol est numériquement une enquête. Concave de glisse de fondation (CSAH) est utilisé pour isoler le plancher surélevé. Les équations de mouvement pour un cisaillement MDOF bâtiment contenant un CSAH isolés plancher surélevé monté avec un équipement sont développés et le lien rigide méthode est utilisée pour traiter la non linéarité du système. L'équipement, qui peut être modélisée comme un SDOF ou MDOF système, mai représentent une critique ordinateur ou système de traitement des télécommunications. SCF peut être utilisé facilement pour atteindre les longue période, nécessaire pour la protection des équipements sensibles. Dans cette enquête, la capacité du SCF dans la réduction du niveau d'accélération rencontrées par les matériels à l'intérieur d'un bâtiment est démontré alors que le déplacement latéral est toujours dans une fourchette acceptable. L'analyse a examiné le cas des équipements hébergés dans les étages supérieurs d'un bâtiment où l'accélération est amplifié et la proposition contient des éléments fort à de longues périodes. À cette fin, différentes excitations comprenant à la fois harmonieuse et véritable tremblement de terre mouvements du sol sont employés et la performance du système est évalué.DEWEY : 551.2 ISSN : 0098-8847 RAMEAU : Séisme En ligne : http://www3.interscience.wiley.com/cgi-bin/abstract/114265753/ABSTRACT [article] On the performance of SCF in seismic isolation of the interior equipment of buildings [texte imprimé] / Moussa Hamidi, Auteur ; M. H. El Naggar, Auteur . - 1581-1604 p.
Génie Civil
Langues : Anglais (eng)
in Earthquake engineering structural dynamics > Vol. 36 N°11 (Octobre 2007) . - 1581-1604 p.
Mots-clés : SCF • isolated raised floor • equipment response • primary structure • secondary system isolés plancher surélevé équipement de réponse structure primaire système secondaire Index. décimale : 624.151 Résumé : The dynamic response of equipment mounted on an isolated raised floor inside a building while the primary fixed base structure is subjected to harmonic and earthquake ground motions is numerically investigated. Sliding concave foundation (SCF) system is utilized for isolating the raised floor. The equations of motion for a MDOF shear building containing a SCF isolated raised floor with a mounted equipment are developed and the rigid link method is utilized to handle the non-linearity of the system. The equipment, which can be modelled as a SDOF or MDOF system, may represent a critical computer unit or telecommunication processing system. SCF can be used easily to achieve the desired long period, necessary for protecting sensitive equipment. In this investigation, the ability of SCF in reducing the acceleration level experienced by the equipment inside a building is demonstrated while the lateral displacement is still within an acceptable range. The analysis considered the case of equipment housed in the upper floors of a building where the acceleration is amplified and the motion contains strong components at long periods. For this purpose, different excitations including both harmonic and real earthquake ground motions are employed and the performance of the system is evaluated.
La réponse dynamique de l'équipement monté sur un plancher surélevé isolé dans un bâtiment alors que la première structure de base fixe est soumis à des harmoniques et les tremblements de terre mouvements du sol est numériquement une enquête. Concave de glisse de fondation (CSAH) est utilisé pour isoler le plancher surélevé. Les équations de mouvement pour un cisaillement MDOF bâtiment contenant un CSAH isolés plancher surélevé monté avec un équipement sont développés et le lien rigide méthode est utilisée pour traiter la non linéarité du système. L'équipement, qui peut être modélisée comme un SDOF ou MDOF système, mai représentent une critique ordinateur ou système de traitement des télécommunications. SCF peut être utilisé facilement pour atteindre les longue période, nécessaire pour la protection des équipements sensibles. Dans cette enquête, la capacité du SCF dans la réduction du niveau d'accélération rencontrées par les matériels à l'intérieur d'un bâtiment est démontré alors que le déplacement latéral est toujours dans une fourchette acceptable. L'analyse a examiné le cas des équipements hébergés dans les étages supérieurs d'un bâtiment où l'accélération est amplifié et la proposition contient des éléments fort à de longues périodes. À cette fin, différentes excitations comprenant à la fois harmonieuse et véritable tremblement de terre mouvements du sol sont employés et la performance du système est évalué.DEWEY : 551.2 ISSN : 0098-8847 RAMEAU : Séisme En ligne : http://www3.interscience.wiley.com/cgi-bin/abstract/114265753/ABSTRACT
