Seismic protection of a building complex using variable friction damper / Y. L. Xu in Journal of engineering mechanics, Vol. 134 n°8 (Août 2008)  

Public ISBD [article]  inJournal of engineering mechanics > Vol. 134 n°8 (Août 2008) . - pp. 637-649 Titre : Seismic protection of a building complex using variable friction damper : Experimental investigation Type de document : texte imprimé Auteurs : Y. L. Xu, Auteur ; C. L. Ng, Auteur Année de publication : 2008 Article en page(s) : pp. 637-649 Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Structural control Damping Algorithms Shake table tests Piezoelectricity Seismic effects Experimentation Résumé : This study presents an experimental investigation of seismic control of a building complex using variable friction damper. The laboratory-scale building complex was composed of a 12-story building and a three-story podium structure coupled in different configurations. The laboratory-scale variable friction damper was tailor made with a piezoelectric actuator. The performance test of the piezoelectric actuator was carried out to identify its characteristics. The performance test was then conducted on the piezo-driven variable friction damper under either constant or varying voltage to identify its motion-independent characteristics. Based on the characterization results, a close-loop operating scheme was proposed together with two classes of semiactive controllers: local-feedback controller and global-feedback controller, for real-time manipulation of the damper. The building complex was finally tested in uncoupled, rigid-coupled, passive damper-coupled, and semiactive damper-coupled configurations. The control performance of variable friction damper for the building complex was examined and compared with other cases. The test results showed that semiactive coupling control was promising for reducing seismic responses of both buildings. ISSN : 0733-9399 En ligne : http://cedb.asce.org/cgi/WWWdisplay.cgi?166078 [article] Seismic protection of a building complex using variable friction damper : Experimental investigation [texte imprimé] / Y. L. Xu, Auteur ; C. L. Ng, Auteur . - 2008 . - pp. 637-649. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 134 n°8 (Août 2008) . - pp. 637-649 Mots-clés : Structural control Damping Algorithms Shake table tests Piezoelectricity Seismic effects Experimentation Résumé : This study presents an experimental investigation of seismic control of a building complex using variable friction damper. The laboratory-scale building complex was composed of a 12-story building and a three-story podium structure coupled in different configurations. The laboratory-scale variable friction damper was tailor made with a piezoelectric actuator. The performance test of the piezoelectric actuator was carried out to identify its characteristics. The performance test was then conducted on the piezo-driven variable friction damper under either constant or varying voltage to identify its motion-independent characteristics. Based on the characterization results, a close-loop operating scheme was proposed together with two classes of semiactive controllers: local-feedback controller and global-feedback controller, for real-time manipulation of the damper. The building complex was finally tested in uncoupled, rigid-coupled, passive damper-coupled, and semiactive damper-coupled configurations. The control performance of variable friction damper for the building complex was examined and compared with other cases. The test results showed that semiactive coupling control was promising for reducing seismic responses of both buildings. ISSN : 0733-9399 En ligne : http://cedb.asce.org/cgi/WWWdisplay.cgi?166078

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SHMS-based fatigue reliability analysis of multiloading suspension bridges / Z. W. Chen in Journal of structural engineering, Vol. 138 N° 3 (Mars 2012)  

Public ISBD [article]  inJournal of structural engineering > Vol. 138 N° 3 (Mars 2012) . - pp. 299-307 Titre : SHMS-based fatigue reliability analysis of multiloading suspension bridges Type de document : texte imprimé Auteurs : Z. W. Chen, Auteur ; Y. L. Xu, Auteur ; X. M. Wang, Auteur Année de publication : 2012 Article en page(s) : pp. 299-307 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Fatigue Reliability Suspension bridges Structural health monitoring Wind loading Railway Highway Résumé : Long-span suspension bridges carrying both highway and railway have been built in wind-prone regions. The estimation of fatigue damage of such bridges under the long-term combined action of railway, highway, and wind loading represents a challenging task in consideration of randomness in multiple types of loading. This study presents a framework for fatigue reliability analysis of multiloading long-span suspension bridges equipped with structural health monitoring systems (SHMS), and the Tsing Ma suspension bridge in Hong Kong is taken as a case study. A limit-state function in the daily sum of m-power stress ranges is first defined for fatigue reliability analysis. Probabilistic models of railway, highway, and wind loading are established on the basis of the measurement data acquired from the SHMS. The daily stochastic stress responses induced by the multiple types of loading are simulated at the fatigue-critical locations of the bridge deck by using the finite-element method and Monte Carlo simulation (MCS) together with the loading probabilistic models established. The probability distribution of the daily sum of m-power stress ranges is estimated on the basis of the daily stochastic stress responses. The probability distribution of the sum of m-power stress ranges for a given time period is then evaluated in consideration of future traffic growth patterns. Finally, the fatigue failure probabilities of the bridge at the fatigue-critical locations are calculated for different time periods. The results demonstrate that the health condition of the Tsing Ma Bridge at the end of its design life will be satisfactory under current traffic conditions without growth but that attention should be paid to future traffic growth because it may lead to a much greater fatigue failure probability. DEWEY : 624.17 ISSN : 0733-9445 En ligne : http://ascelibrary.org/sto/resource/1/jsendh/v138/i3/p299_s1?isAuthorized=no [article] SHMS-based fatigue reliability analysis of multiloading suspension bridges [texte imprimé] / Z. W. Chen, Auteur ; Y. L. Xu, Auteur ; X. M. Wang, Auteur . - 2012 . - pp. 299-307. Génie Civil Langues : Anglais (eng) in Journal of structural engineering > Vol. 138 N° 3 (Mars 2012) . - pp. 299-307 Mots-clés : Fatigue Reliability Suspension bridges Structural health monitoring Wind loading Railway Highway Résumé : Long-span suspension bridges carrying both highway and railway have been built in wind-prone regions. The estimation of fatigue damage of such bridges under the long-term combined action of railway, highway, and wind loading represents a challenging task in consideration of randomness in multiple types of loading. This study presents a framework for fatigue reliability analysis of multiloading long-span suspension bridges equipped with structural health monitoring systems (SHMS), and the Tsing Ma suspension bridge in Hong Kong is taken as a case study. A limit-state function in the daily sum of m-power stress ranges is first defined for fatigue reliability analysis. Probabilistic models of railway, highway, and wind loading are established on the basis of the measurement data acquired from the SHMS. The daily stochastic stress responses induced by the multiple types of loading are simulated at the fatigue-critical locations of the bridge deck by using the finite-element method and Monte Carlo simulation (MCS) together with the loading probabilistic models established. The probability distribution of the daily sum of m-power stress ranges is estimated on the basis of the daily stochastic stress responses. The probability distribution of the sum of m-power stress ranges for a given time period is then evaluated in consideration of future traffic growth patterns. Finally, the fatigue failure probabilities of the bridge at the fatigue-critical locations are calculated for different time periods. The results demonstrate that the health condition of the Tsing Ma Bridge at the end of its design life will be satisfactory under current traffic conditions without growth but that attention should be paid to future traffic growth because it may lead to a much greater fatigue failure probability. DEWEY : 624.17 ISSN : 0733-9445 En ligne : http://ascelibrary.org/sto/resource/1/jsendh/v138/i3/p299_s1?isAuthorized=no

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Structural Damage DEtection using Empirical Mode Decomposition: Experimental investigation / Y. L. Xu in Journal of engineering mechanics, Vol. 130 N°11 (Novembre 2004)  

Public ISBD [article]  inJournal of engineering mechanics > Vol. 130 N°11 (Novembre 2004) . - 1279-1288 p. Titre : Structural Damage DEtection using Empirical Mode Decomposition: Experimental investigation Titre original : Détection Structurale de Dommages en Utilisant Mode de Décomposition Empirique : Recherche Expérimentale Type de document : texte imprimé Auteurs : Y. L. Xu, Auteur ; Chen, J., Auteur ; Ghanem, Roger G., Éditeur scientifique Année de publication : 2006 Article en page(s) : 1279-1288 p. Note générale : Génie Mécanique Langues : Anglais (eng) Mots-clés : Vibration Damage assesssment Data analysis Decomposition Structural safety Stiffness Evaluation de dommages Analyse données Sûreté structurale Rigidité Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : This paper presents an experimental investigation on the applicability of the empirical mode decomposition (EMD) for identifying structural damage caused by a sudden change of structural stiffness. A three-story shear building model was constructed and installed on a shaking table with two springs horizontally connected to the first floor of the building to provide additional structural stiffness. Structural damage was simulated by suddenly releasing two pretensioned springs either simultaneously or successively. Various damage severities were produced using springs of different stiffness. A series of free vibration, random vibration, and earthquake simulation tests were performed on the building with sudden stiffness changes. Dynamic responses including floor accelerations and displacements, column strains, and spring releasing time instants were measured. The EMD was then applied to measured time histories to identify damage time instant and damage location for various test cases. The comparison of identified results with measured ones showed that damage time instants could be accurately detected in terms of damage spikes extracted directly from the measurement data by EMD. The damage location could be determined by the spatial distribution of the spikes along the building. The influence of damage severity, sampling frequency, and measured quantities on the performance of EMD for damage detection was also discussed. Cet article présente une recherche expérimentale sur l'applicabilité de la décomposition empirique de mode (EMD) pour identifier des dommages structuraux provoqués par un changement soudain de rigidité structurale. Un modèle de bâtiment de cisaillement de trois histoires a été construit et installé sur une table de secousse avec deux ressorts horizontalement reliés au premier étage du bâtiment pour fournir la rigidité structurale additionnelle. Des dommages structuraux ont été simulés en libérant soudainement deux ressorts prétendus simultanément ou successivement. De divers severities de dommages ont été produits à l'aide des ressorts de rigidité différente. Une série de vibration libre, de vibration aléatoire, et d'essais de simulation de tremblement de terre a été effectuée sur le bâtiment avec les changements soudains de rigidité. Des réponses dynamiques comprenant des accélérations et des déplacements de plancher, des contraintes de colonne, et ressort libérant des instants de temps ont été mesurées. L'EMD a été alors appliqué aux histoires mesurées de temps pour identifier l'instant de temps de dommages et l'endroit de dommages pour différents cas d'espèce. La comparaison des résultats identifiés avec mesuré a prouvé que des instants de temps de dommages pourraient être exactement détectés en termes de transitoires de dommages extraites directement à partir des données de mesure par EMD. L'endroit de dommages a pu être déterminé par la distribution spatiale des transitoires le long du bâtiment. L'influence de la sévérité de dommages, de la fréquence de prélèvement, et des quantités mesurées sur l'exécution d'EMD pour la détection de dommages a été également discutée. DEWEY : 620.1 ISSN : 0733-9399 En ligne : ceylxu@polyu.edu.hk [article] Structural Damage DEtection using Empirical Mode Decomposition: Experimental investigation = Détection Structurale de Dommages en Utilisant Mode de Décomposition Empirique : Recherche Expérimentale [texte imprimé] / Y. L. Xu, Auteur ; Chen, J., Auteur ; Ghanem, Roger G., Éditeur scientifique . - 2006 . - 1279-1288 p. Génie Mécanique Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 130 N°11 (Novembre 2004) . - 1279-1288 p. Mots-clés : Vibration Damage assesssment Data analysis Decomposition Structural safety Stiffness Evaluation de dommages Analyse données Sûreté structurale Rigidité Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : This paper presents an experimental investigation on the applicability of the empirical mode decomposition (EMD) for identifying structural damage caused by a sudden change of structural stiffness. A three-story shear building model was constructed and installed on a shaking table with two springs horizontally connected to the first floor of the building to provide additional structural stiffness. Structural damage was simulated by suddenly releasing two pretensioned springs either simultaneously or successively. Various damage severities were produced using springs of different stiffness. A series of free vibration, random vibration, and earthquake simulation tests were performed on the building with sudden stiffness changes. Dynamic responses including floor accelerations and displacements, column strains, and spring releasing time instants were measured. The EMD was then applied to measured time histories to identify damage time instant and damage location for various test cases. The comparison of identified results with measured ones showed that damage time instants could be accurately detected in terms of damage spikes extracted directly from the measurement data by EMD. The damage location could be determined by the spatial distribution of the spikes along the building. The influence of damage severity, sampling frequency, and measured quantities on the performance of EMD for damage detection was also discussed. Cet article présente une recherche expérimentale sur l'applicabilité de la décomposition empirique de mode (EMD) pour identifier des dommages structuraux provoqués par un changement soudain de rigidité structurale. Un modèle de bâtiment de cisaillement de trois histoires a été construit et installé sur une table de secousse avec deux ressorts horizontalement reliés au premier étage du bâtiment pour fournir la rigidité structurale additionnelle. Des dommages structuraux ont été simulés en libérant soudainement deux ressorts prétendus simultanément ou successivement. De divers severities de dommages ont été produits à l'aide des ressorts de rigidité différente. Une série de vibration libre, de vibration aléatoire, et d'essais de simulation de tremblement de terre a été effectuée sur le bâtiment avec les changements soudains de rigidité. Des réponses dynamiques comprenant des accélérations et des déplacements de plancher, des contraintes de colonne, et ressort libérant des instants de temps ont été mesurées. L'EMD a été alors appliqué aux histoires mesurées de temps pour identifier l'instant de temps de dommages et l'endroit de dommages pour différents cas d'espèce. La comparaison des résultats identifiés avec mesuré a prouvé que des instants de temps de dommages pourraient être exactement détectés en termes de transitoires de dommages extraites directement à partir des données de mesure par EMD. L'endroit de dommages a pu être déterminé par la distribution spatiale des transitoires le long du bâtiment. L'influence de la sévérité de dommages, de la fréquence de prélèvement, et des quantités mesurées sur l'exécution d'EMD pour la détection de dommages a été également discutée. DEWEY : 620.1 ISSN : 0733-9399 En ligne : ceylxu@polyu.edu.hk

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