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Détail de l'auteur
Auteur Bray, Jonathan D.
Documents disponibles écrits par cet auteur
Affiner la rechercheCentrifuge testing to evaluate and mitigate liquefaction-induced building settlement mechanisms / Shideh Dashti in Journal of geotechnical and geoenvironmental engineering, Vol. 136 N° 7 (Juillet 2010)
in Journal of geotechnical and geoenvironmental engineering > Vol. 136 N° 7 (Juillet 2010) . - pp. 918-929
Titre : Centrifuge testing to evaluate and mitigate liquefaction-induced building settlement mechanisms Type de document : texte imprimé Auteurs : Shideh Dashti, Auteur ; Bray, Jonathan D., Auteur ; Juan M. Pestana, Auteur Année de publication : 2010 Article en page(s) : pp. 918-929 Note générale : Géotechnique Langues : Anglais (eng) Mots-clés : Centrifuge Earthquakes Liquefaction Mitigation Settlement Shallow foundation Soil structure interaction Résumé : The effective application of liquefaction mitigation techniques requires an improved understanding of the development and consequences of liquefaction. Centrifuge experiments were performed to study the dominant mechanisms of seismically induced settlement of buildings with rigid mat foundations on thin deposits of liquefiable sand. The relative importance of key settlement mechanisms was evaluated by using mitigation techniques to minimize some of their respective contributions. The relative importance of settlement mechanisms was shown to depend on the characteristics of the earthquake motion, liquefiable soil, and building. The initiation, rate, and amount of liquefaction-induced building settlement depended greatly on the rate of ground shaking. Engineering design procedures should incorporate this important feature of earthquake shaking, which may be represented by the time rate of Arias intensity (i.e., the shaking intensity rate). In these experiments, installation of an independent, in-ground, perimetrical, stiff structural wall minimized deviatoric soil deformations under the building and reduced total building settlements by approximately 50%. Use of a flexible impermeable barrier that inhibited horizontal water flow without preventing shear deformation also reduced permanent building settlements but less significantly.
DEWEY : 624.1 ISSN : 1090-0241 En ligne : http://ascelibrary.org/gto/resource/1/jggefk/v136/i7/p918_s1?isAuthorized=no [article] Centrifuge testing to evaluate and mitigate liquefaction-induced building settlement mechanisms [texte imprimé] / Shideh Dashti, Auteur ; Bray, Jonathan D., Auteur ; Juan M. Pestana, Auteur . - 2010 . - pp. 918-929.
Géotechnique
Langues : Anglais (eng)
in Journal of geotechnical and geoenvironmental engineering > Vol. 136 N° 7 (Juillet 2010) . - pp. 918-929
Mots-clés : Centrifuge Earthquakes Liquefaction Mitigation Settlement Shallow foundation Soil structure interaction Résumé : The effective application of liquefaction mitigation techniques requires an improved understanding of the development and consequences of liquefaction. Centrifuge experiments were performed to study the dominant mechanisms of seismically induced settlement of buildings with rigid mat foundations on thin deposits of liquefiable sand. The relative importance of key settlement mechanisms was evaluated by using mitigation techniques to minimize some of their respective contributions. The relative importance of settlement mechanisms was shown to depend on the characteristics of the earthquake motion, liquefiable soil, and building. The initiation, rate, and amount of liquefaction-induced building settlement depended greatly on the rate of ground shaking. Engineering design procedures should incorporate this important feature of earthquake shaking, which may be represented by the time rate of Arias intensity (i.e., the shaking intensity rate). In these experiments, installation of an independent, in-ground, perimetrical, stiff structural wall minimized deviatoric soil deformations under the building and reduced total building settlements by approximately 50%. Use of a flexible impermeable barrier that inhibited horizontal water flow without preventing shear deformation also reduced permanent building settlements but less significantly.
DEWEY : 624.1 ISSN : 1090-0241 En ligne : http://ascelibrary.org/gto/resource/1/jggefk/v136/i7/p918_s1?isAuthorized=no
in Journal of engineering mechanics > Vol. 130 N°10 (Octobre 2004) . - 1140-1150 p.
Titre : Examination of the Response of Regularly Packed Specimens of Spherical Particles using Physical Tests and Discrete Element Simulations Titre original : Examen de la Réponse des Spécimens Régulièrement Emballés des Particules Sphériques en Utilisant les Essais Physiques et les Simulations Discrètes d'Elément Type de document : texte imprimé Auteurs : O'Sullivan, Catherine, Auteur ; Bray, Jonathan D., Auteur ; Riemer, Michael ; Ooi, J. Y., Editeur scientifique Article en page(s) : 1140-1150 p. Note générale : Génie Mécanique Langues : Anglais (eng) Mots-clés : Partcles Discrete elements Simulation Compression tests Granular materials Particules Eléments discrets Essais de compressibilité Matériaux granulaires Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Significant insight into the response of granular materials can be gained by coupling accurately controlled physical tests with complementary discrete element simulations. This paper discusses a series of triaxial and plane strain laboratory compression tests on steel spheres with face-centered-cubic and rhombic packings, as well as discrete element simulations of these tests. The tests were performed on specimens of uniform-sized steel balls and on specimens of steel balls with specified distributions of ball diameters. The packing configurations are ideal and differ considerably from real sand specimens, however, studies of such idealized granular materials can yield considerable insight into the response of granular materials and the capability of discrete element simulations to capture the response. The differences in response for the two packing configurations considered illustrate the importance of fabric. The numerical simulations captured the observed laboratory response well if the particle configurations, particle sizes, and boundary conditions were accurately represented. However, the postpeak response is more difficult to capture, and it is shown to be sensitive to the coefficient of friction assumed along the specimen boundaries. The simulations of the tests on the nonuniform-sized specimens demonstrated a clear correlation between strength and coordination number.
L'aperçu significatif de la réponse des matériaux granulaires peut être gagné en couplant exactement les essais physiques commandés avec des simulations discrètes complémentaires d'élément. Cet article discute une série d'essais de compressibilité à trois axes et plats de laboratoire de contrainte sur les sphères en acier avec des emballages visage-centrer-cubiques et rhombiques, aussi bien que des simulations discrètes d'élément de ces essais. Les essais ont été réalisés sur des spécimens des boules en acier uniforme-classées et sur des spécimens des boules en acier avec des distributions indiquées des diamètres de boule. Les configurations d'emballage sont idéales et diffèrent considérablement de vrais spécimens de sable, cependant, les études de tels matériaux granulaires idéalisés peuvent rapporter l'perspicacité considérable dans la réponse des matériaux granulaires et les possibilités des simulations discrètes d'élément pour capturer la réponse. Les différences dans la réponse pour les deux configurations d'emballage considérées illustrent l'importance du tissu. Les simulations numériques ont bien capturé la réponse observée de laboratoire si les configurations de particules, les dimensions particulaires, et les conditions de frontière étaient exactement représentés. Cependant, il est plus difficile capturer la réponse de postpeak, et il s'avère sensible au coefficient de frottement supposé le long des frontières de spécimen. Les simulations des essais sur les spécimens non-uniforme-classés ont démontré une corrélation claire entre la force et le nombre de coordination.
DEWEY : 620.1 ISSN : 0733-9399 En ligne : catherine.osullivan@ucd.ie [article] Examination of the Response of Regularly Packed Specimens of Spherical Particles using Physical Tests and Discrete Element Simulations = Examen de la Réponse des Spécimens Régulièrement Emballés des Particules Sphériques en Utilisant les Essais Physiques et les Simulations Discrètes d'Elément [texte imprimé] / O'Sullivan, Catherine, Auteur ; Bray, Jonathan D., Auteur ; Riemer, Michael ; Ooi, J. Y., Editeur scientifique . - 1140-1150 p.
Génie Mécanique
Langues : Anglais (eng)
in Journal of engineering mechanics > Vol. 130 N°10 (Octobre 2004) . - 1140-1150 p.
Mots-clés : Partcles Discrete elements Simulation Compression tests Granular materials Particules Eléments discrets Essais de compressibilité Matériaux granulaires Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Significant insight into the response of granular materials can be gained by coupling accurately controlled physical tests with complementary discrete element simulations. This paper discusses a series of triaxial and plane strain laboratory compression tests on steel spheres with face-centered-cubic and rhombic packings, as well as discrete element simulations of these tests. The tests were performed on specimens of uniform-sized steel balls and on specimens of steel balls with specified distributions of ball diameters. The packing configurations are ideal and differ considerably from real sand specimens, however, studies of such idealized granular materials can yield considerable insight into the response of granular materials and the capability of discrete element simulations to capture the response. The differences in response for the two packing configurations considered illustrate the importance of fabric. The numerical simulations captured the observed laboratory response well if the particle configurations, particle sizes, and boundary conditions were accurately represented. However, the postpeak response is more difficult to capture, and it is shown to be sensitive to the coefficient of friction assumed along the specimen boundaries. The simulations of the tests on the nonuniform-sized specimens demonstrated a clear correlation between strength and coordination number.
L'aperçu significatif de la réponse des matériaux granulaires peut être gagné en couplant exactement les essais physiques commandés avec des simulations discrètes complémentaires d'élément. Cet article discute une série d'essais de compressibilité à trois axes et plats de laboratoire de contrainte sur les sphères en acier avec des emballages visage-centrer-cubiques et rhombiques, aussi bien que des simulations discrètes d'élément de ces essais. Les essais ont été réalisés sur des spécimens des boules en acier uniforme-classées et sur des spécimens des boules en acier avec des distributions indiquées des diamètres de boule. Les configurations d'emballage sont idéales et diffèrent considérablement de vrais spécimens de sable, cependant, les études de tels matériaux granulaires idéalisés peuvent rapporter l'perspicacité considérable dans la réponse des matériaux granulaires et les possibilités des simulations discrètes d'élément pour capturer la réponse. Les différences dans la réponse pour les deux configurations d'emballage considérées illustrent l'importance du tissu. Les simulations numériques ont bien capturé la réponse observée de laboratoire si les configurations de particules, les dimensions particulaires, et les conditions de frontière étaient exactement représentés. Cependant, il est plus difficile capturer la réponse de postpeak, et il s'avère sensible au coefficient de frottement supposé le long des frontières de spécimen. Les simulations des essais sur les spécimens non-uniforme-classés ont démontré une corrélation claire entre la force et le nombre de coordination.
DEWEY : 620.1 ISSN : 0733-9399 En ligne : catherine.osullivan@ucd.ie
in Journal of geotechnical and geoenvironmental engineering > Vol. 136 N° 1 (Janvier 2010) . - pp. 151-164
Titre : Mechanisms of seismically induced settlement of buildings with shallow foundations on liquefiable soil Type de document : texte imprimé Auteurs : Shideh Dashti, Auteur ; Bray, Jonathan D., Auteur ; Juan M. Pestana, Auteur Article en page(s) : pp. 151-164 Note générale : Géotechnique Langues : Anglais (eng) Mots-clés : Centrifuge Earthquakes Liquefaction Performance-based design Soil-structure interaction Settlement Index. décimale : 624.1 Infrastructures.Ouvrages en terre. Fondations. Tunnels Résumé : Seismically induced settlement of buildings with shallow foundations on liquefiable soils has resulted in significant damage in recent earthquakes. Engineers still largely estimate seismic building settlement using procedures developed to calculate postliquefaction reconsolidation settlement in the free-field. A series of centrifuge experiments involving buildings situated atop a layered soil deposit have been performed to identify the mechanisms involved in liquefaction-induced building settlement. Previous studies of this problem have identified important factors including shaking intensity, the liquefiable soil's relative density and thickness, and the building's weight and width. Centrifuge test results indicate that building settlement is not proportional to the thickness of the liquefiable layer and that most of this settlement occurs during earthquake strong shaking. Building-induced shear deformations combined with localized volumetric strains during partially drained cyclic loading are the dominant mechanisms. The development of high excess pore pressures, localized drainage in response to the high transient hydraulic gradients, and earthquake-induced ratcheting of the buildings into the softened soil are important effects that should be captured in design procedures that estimate liquefaction-induced building settlement.
DEWEY : 624.1 ISSN : 1090-0241 En ligne : http://ascelibrary.aip.org/vsearch/servlet/VerityServlet?KEY=JGGEFK&smode=strres [...] [article] Mechanisms of seismically induced settlement of buildings with shallow foundations on liquefiable soil [texte imprimé] / Shideh Dashti, Auteur ; Bray, Jonathan D., Auteur ; Juan M. Pestana, Auteur . - pp. 151-164.
Géotechnique
Langues : Anglais (eng)
in Journal of geotechnical and geoenvironmental engineering > Vol. 136 N° 1 (Janvier 2010) . - pp. 151-164
Mots-clés : Centrifuge Earthquakes Liquefaction Performance-based design Soil-structure interaction Settlement Index. décimale : 624.1 Infrastructures.Ouvrages en terre. Fondations. Tunnels Résumé : Seismically induced settlement of buildings with shallow foundations on liquefiable soils has resulted in significant damage in recent earthquakes. Engineers still largely estimate seismic building settlement using procedures developed to calculate postliquefaction reconsolidation settlement in the free-field. A series of centrifuge experiments involving buildings situated atop a layered soil deposit have been performed to identify the mechanisms involved in liquefaction-induced building settlement. Previous studies of this problem have identified important factors including shaking intensity, the liquefiable soil's relative density and thickness, and the building's weight and width. Centrifuge test results indicate that building settlement is not proportional to the thickness of the liquefiable layer and that most of this settlement occurs during earthquake strong shaking. Building-induced shear deformations combined with localized volumetric strains during partially drained cyclic loading are the dominant mechanisms. The development of high excess pore pressures, localized drainage in response to the high transient hydraulic gradients, and earthquake-induced ratcheting of the buildings into the softened soil are important effects that should be captured in design procedures that estimate liquefaction-induced building settlement.
DEWEY : 624.1 ISSN : 1090-0241 En ligne : http://ascelibrary.aip.org/vsearch/servlet/VerityServlet?KEY=JGGEFK&smode=strres [...]
in Journal of geotechnical and geoenvironmental engineering > Vol. 136 N° 9 (Septembre 2010) . - pp. 1231-1241
Titre : Physical characterization of municipal solid waste for geotechnical purposes Type de document : texte imprimé Auteurs : Dimitrios Zekkos, Auteur ; Edward Jr Kavazanjian, Auteur ; Bray, Jonathan D., Auteur Année de publication : 2010 Article en page(s) : pp. 1231-1241 Note générale : Géotechnique Langues : Anglais (eng) Mots-clés : Municipal solid waste Organic content Water content Waste classification Waste Landfills Geotechnical characterization Index. décimale : 624.1 Infrastructures.Ouvrages en terre. Fondations. Tunnels Résumé : A procedure to characterize municipal solid waste (MSW) for geotechnical engineering purposes is developed based on experience with waste characterization and testing. Existing MSW classification systems are reviewed briefly, and the field and laboratory waste characterization programs of two important projects are presented. Findings on the influence of the waste’s physical composition on its mechanical response from these projects and recent studies of MSW are integrated to develop a waste characterization procedure for efficient collection of the relevant information on landfill operation and waste physical characteristics that are most likely to affect the geotechnical properties of MSW. A phased approach to implementation of this procedure is proposed as a best practice for the physical characterization of MSW for geotechnical purposes. The scope of the phased procedure can be adjusted to optimize the effort required to collect relevant information on a project-specific basis. The procedure includes a systematic evaluation of the moisture and organic content of MSW, because they are important factors in the geotechnical characterization of MSW.
DEWEY : 624.1 ISSN : 1090-0241 En ligne : http://ascelibrary.org/gto/resource/1/jggefk/v136/i9/p1231_s1?isAuthorized=no [article] Physical characterization of municipal solid waste for geotechnical purposes [texte imprimé] / Dimitrios Zekkos, Auteur ; Edward Jr Kavazanjian, Auteur ; Bray, Jonathan D., Auteur . - 2010 . - pp. 1231-1241.
Géotechnique
Langues : Anglais (eng)
in Journal of geotechnical and geoenvironmental engineering > Vol. 136 N° 9 (Septembre 2010) . - pp. 1231-1241
Mots-clés : Municipal solid waste Organic content Water content Waste classification Waste Landfills Geotechnical characterization Index. décimale : 624.1 Infrastructures.Ouvrages en terre. Fondations. Tunnels Résumé : A procedure to characterize municipal solid waste (MSW) for geotechnical engineering purposes is developed based on experience with waste characterization and testing. Existing MSW classification systems are reviewed briefly, and the field and laboratory waste characterization programs of two important projects are presented. Findings on the influence of the waste’s physical composition on its mechanical response from these projects and recent studies of MSW are integrated to develop a waste characterization procedure for efficient collection of the relevant information on landfill operation and waste physical characteristics that are most likely to affect the geotechnical properties of MSW. A phased approach to implementation of this procedure is proposed as a best practice for the physical characterization of MSW for geotechnical purposes. The scope of the phased procedure can be adjusted to optimize the effort required to collect relevant information on a project-specific basis. The procedure includes a systematic evaluation of the moisture and organic content of MSW, because they are important factors in the geotechnical characterization of MSW.
DEWEY : 624.1 ISSN : 1090-0241 En ligne : http://ascelibrary.org/gto/resource/1/jggefk/v136/i9/p1231_s1?isAuthorized=no
in Journal of geotechnical and geoenvironmental engineering > Vol. 136 N° 3 (Mars 2010) . - pp. 464-476
Titre : Probabilistic performance-based procedure to evaluate pile foundations at sites with liquefaction-induced lateral displacement Type de document : texte imprimé Auteurs : Christian Ledezma, Auteur ; Bray, Jonathan D., Auteur Article en page(s) : pp. 464-476 Note générale : Géotechnique Langues : Anglais (eng) Mots-clés : Bridges Displacement Lateral spreading Liquefaction Performance-based design Pile foundations Index. décimale : 624.1 Infrastructures.Ouvrages en terre. Fondations. Tunnels Résumé : Liquefaction-induced ground deformation has caused major damage to bridge and wharf structures in past earthquakes. Large lateral ground displacements may induce significant forces in the foundation and superstructure, which may lead to severe damage or even collapse. A performance-based earthquake engineering (PBEE) approach can provide an objective assessment of the likely seismic performance, so that agencies can evaluate bridge or wharf structures, compare retrofit strategies, and rank them within their overall system. In this paper, a probabilistic PBEE design procedure that incorporates findings from recent research on this problem is presented. The proposed approach can provide answers in terms that are meaningful to owners, such as expected repair costs and downtimes. The methodology is validated through its application to a well-documented case history. Results show that the proposed approach provides a good estimate of the seismic performance of pile-supported structures at sites with liquefaction-induced lateral displacement.
DEWEY : 624.1 ISSN : 1090-0241 En ligne : http://ascelibrary.aip.org/vsearch/servlet/VerityServlet?KEY=JGGEFK&smode=strres [...] [article] Probabilistic performance-based procedure to evaluate pile foundations at sites with liquefaction-induced lateral displacement [texte imprimé] / Christian Ledezma, Auteur ; Bray, Jonathan D., Auteur . - pp. 464-476.
Géotechnique
Langues : Anglais (eng)
in Journal of geotechnical and geoenvironmental engineering > Vol. 136 N° 3 (Mars 2010) . - pp. 464-476
Mots-clés : Bridges Displacement Lateral spreading Liquefaction Performance-based design Pile foundations Index. décimale : 624.1 Infrastructures.Ouvrages en terre. Fondations. Tunnels Résumé : Liquefaction-induced ground deformation has caused major damage to bridge and wharf structures in past earthquakes. Large lateral ground displacements may induce significant forces in the foundation and superstructure, which may lead to severe damage or even collapse. A performance-based earthquake engineering (PBEE) approach can provide an objective assessment of the likely seismic performance, so that agencies can evaluate bridge or wharf structures, compare retrofit strategies, and rank them within their overall system. In this paper, a probabilistic PBEE design procedure that incorporates findings from recent research on this problem is presented. The proposed approach can provide answers in terms that are meaningful to owners, such as expected repair costs and downtimes. The methodology is validated through its application to a well-documented case history. Results show that the proposed approach provides a good estimate of the seismic performance of pile-supported structures at sites with liquefaction-induced lateral displacement.
DEWEY : 624.1 ISSN : 1090-0241 En ligne : http://ascelibrary.aip.org/vsearch/servlet/VerityServlet?KEY=JGGEFK&smode=strres [...]
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