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Effect of seismic uplift pressure on the behavior of concrete gravity dams with a penetrated crack / Pekau, O. A. in Journal of engineering mechanics, Vol. 134 n°11 (Novembre 2008) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 134 n°11 (Novembre 2008) . - pp. 991–999. Titre : Effect of seismic uplift pressure on the behavior of concrete gravity dams with a penetrated crack Type de document : texte imprimé Auteurs : Pekau, O. A., Auteur ; Zhu, Xueye, Auteur Année de publication : 2008 Article en page(s) : pp. 991–999. Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Dams  gravity  Seismic  effects  Pressure  Cracking  Dam  safety Résumé : Proper consideration of the uplift pressure at the base of a concrete gravity dam is of great importance in practical engineering, since it is crucial to the safety of the dam, specifically for a cracked dam under seismic conditions. However, constant uplift pressure, which is suitable for the static case only, was adopted in almost all the seismic analyses of cracked concrete gravity dams. To adequately estimate the seismic behavior of cracked concrete gravity dams, a seismic uplift pressure model is proposed for a penetrated crack. In this model, the amount and the distribution of the uplift pressure along the assumed rigid crack walls are determined by the earthquake acceleration, the water heads, the aperture of the crack, and the opening/closing velocity. Application of the model to a typical concrete gravity dam with a penetrated crack at the base reveals that the seismic behavior of the dam is markedly affected by the seismic uplift pressure. In general, the residual downstream sliding is considerably enlarged compared to that of constant uplift pressure. Computations show that the seismic uplift pressure can be several times higher than the constant one, increasing the dynamic instability of the cracked dam. It is also revealed that the dynamic water flow plays the role of a wedge while the upper mouth of the crack is closing. When the dam rocks back to upstream, the uplift pressure increases until it is so high that the pivot at the toe is raised up and the whole dam loses its contact. Then the resultant uplift pressure remains constant until the dam is inclined to the upstream. During this period of time, the cracked dam is normally drifting towards the downstream due to the hydro pressure. ISSN : 0733-9399 En ligne : Dams, gravity, Seismic effects, Pressure, Crackinghttp://ascelibrary.org/doi/abs [...] [article] Effect of seismic uplift pressure on the behavior of concrete gravity dams with a penetrated crack [texte imprimé] / Pekau, O. A., Auteur ; Zhu, Xueye, Auteur . - 2008 . - pp. 991–999. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 134 n°11 (Novembre 2008) . - pp. 991–999. Mots-clés : Dams  gravity  Seismic  effects  Pressure  Cracking  Dam  safety Résumé : Proper consideration of the uplift pressure at the base of a concrete gravity dam is of great importance in practical engineering, since it is crucial to the safety of the dam, specifically for a cracked dam under seismic conditions. However, constant uplift pressure, which is suitable for the static case only, was adopted in almost all the seismic analyses of cracked concrete gravity dams. To adequately estimate the seismic behavior of cracked concrete gravity dams, a seismic uplift pressure model is proposed for a penetrated crack. In this model, the amount and the distribution of the uplift pressure along the assumed rigid crack walls are determined by the earthquake acceleration, the water heads, the aperture of the crack, and the opening/closing velocity. Application of the model to a typical concrete gravity dam with a penetrated crack at the base reveals that the seismic behavior of the dam is markedly affected by the seismic uplift pressure. In general, the residual downstream sliding is considerably enlarged compared to that of constant uplift pressure. Computations show that the seismic uplift pressure can be several times higher than the constant one, increasing the dynamic instability of the cracked dam. It is also revealed that the dynamic water flow plays the role of a wedge while the upper mouth of the crack is closing. When the dam rocks back to upstream, the uplift pressure increases until it is so high that the pivot at the toe is raised up and the whole dam loses its contact. Then the resultant uplift pressure remains constant until the dam is inclined to the upstream. During this period of time, the cracked dam is normally drifting towards the downstream due to the hydro pressure. ISSN : 0733-9399 En ligne : Dams, gravity, Seismic effects, Pressure, Crackinghttp://ascelibrary.org/doi/abs [...]

Three-Degree-of-Freedom Rigid Model for Seismic Analysis of Cracked Concrete Gravity Dams / Pekau, O. A. in Journal of engineering mechanics, Vol. 132 N°9 (Septembre 2006) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 132 N°9 (Septembre 2006) . - 979-989 p. Titre : Three-Degree-of-Freedom Rigid Model for Seismic Analysis of Cracked Concrete Gravity Dams Titre original : Trois Degrés de Modèle Rigide de Liberté pour l'Analyse Séismique des Barrages Concrets Criqués de Pesanteur Type de document : texte imprimé Auteurs : Pekau, O. A., Auteur ; Zhu, Xueye, Auteur Article en page(s) : 979-989 p. Note générale : Génie Mécanique Langues : Anglais (eng) Mots-clés : Earthquake  engineering  Seismic  analysis  Dams  Rigid-body  dynamics  Sliding  Contacts  Impact  Rotation  Tremblement  de  terre  Analyse  séismique  Barrages  Dynamique  de  corps  rigide  Glissement Index. décimale : 621.34/624 Résumé : A Rigid model with three-degrees-of-freedom is proposed for the purpose of seismic analysis of cracked concrete gravity dams. The model considers the geometry of the dam and all its possible modes of motion: sliding, rocking, rock-sliding, and drifting. The governing equations for all the modes are derived with the Mohr-Coulomb friction assumption at the crack, and corresponding conditions to initiate and maintain the modes are also given. For impact that follows rocking and drifting modes, postimpact velocities of the model are explicitly determined according to the momentum principle and the concept of restitution from classical point collision. Studies with the proposed model on rectangular blocks demonstrate two different types of rocking according to the slenderness. Applications to dams indicate that a large coefficient of friction does not necessarily prevent sliding, and rocking and drifting modes should not be neglected in estimating the stability of concrete gravity dams cracked at the base or at a height. On propose un modèle rigide avec trois degrés de liberté afin de l'analyse séismique des barrages concrets criqués de pesanteur. Le modèle considère la géométrie du barrage et tous ses modes possibles de mouvement : glissant, basculant, roche-glissant, et dérivant. Les équations régissantes pour tous les modes sont dérivées avec les conditions de prétention à la fente, et de correspondance de frottement de Mohr-Coulomb à l'initié et maintiennent les modes sont également données. Pour l'impact qui suit des modes basculants et dérivants, des vitesses de postimpact du modèle sont explicitement déterminées selon le principe d'élan et le concept de la restitution à partir de la collision classique de point. Les études avec le modèle proposé sur les blocs rectangulaires démontrent deux types différents de basculer selon le slenderness. Les applications aux barrages indiquent qu'un grand coefficient de frottement n'empêche pas nécessairement le glissement, et basculant et des modes dérivants ne devraient pas être négligés en estimant la stabilité des barrages concrets de pesanteur fendus à la base ou à une taille. En ligne : oapekau@civil.concordia.ca, xue_zhu@civil.concordia.ca [article] Three-Degree-of-Freedom Rigid Model for Seismic Analysis of Cracked Concrete Gravity Dams = Trois Degrés de Modèle Rigide de Liberté pour l'Analyse Séismique des Barrages Concrets Criqués de Pesanteur [texte imprimé] / Pekau, O. A., Auteur ; Zhu, Xueye, Auteur . - 979-989 p. Génie Mécanique Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 132 N°9 (Septembre 2006) . - 979-989 p. Mots-clés : Earthquake  engineering  Seismic  analysis  Dams  Rigid-body  dynamics  Sliding  Contacts  Impact  Rotation  Tremblement  de  terre  Analyse  séismique  Barrages  Dynamique  de  corps  rigide  Glissement Index. décimale : 621.34/624 Résumé : A Rigid model with three-degrees-of-freedom is proposed for the purpose of seismic analysis of cracked concrete gravity dams. The model considers the geometry of the dam and all its possible modes of motion: sliding, rocking, rock-sliding, and drifting. The governing equations for all the modes are derived with the Mohr-Coulomb friction assumption at the crack, and corresponding conditions to initiate and maintain the modes are also given. For impact that follows rocking and drifting modes, postimpact velocities of the model are explicitly determined according to the momentum principle and the concept of restitution from classical point collision. Studies with the proposed model on rectangular blocks demonstrate two different types of rocking according to the slenderness. Applications to dams indicate that a large coefficient of friction does not necessarily prevent sliding, and rocking and drifting modes should not be neglected in estimating the stability of concrete gravity dams cracked at the base or at a height. On propose un modèle rigide avec trois degrés de liberté afin de l'analyse séismique des barrages concrets criqués de pesanteur. Le modèle considère la géométrie du barrage et tous ses modes possibles de mouvement : glissant, basculant, roche-glissant, et dérivant. Les équations régissantes pour tous les modes sont dérivées avec les conditions de prétention à la fente, et de correspondance de frottement de Mohr-Coulomb à l'initié et maintiennent les modes sont également données. Pour l'impact qui suit des modes basculants et dérivants, des vitesses de postimpact du modèle sont explicitement déterminées selon le principe d'élan et le concept de la restitution à partir de la collision classique de point. Les études avec le modèle proposé sur les blocs rectangulaires démontrent deux types différents de basculer selon le slenderness. Les applications aux barrages indiquent qu'un grand coefficient de frottement n'empêche pas nécessairement le glissement, et basculant et des modes dérivants ne devraient pas être négligés en estimant la stabilité des barrages concrets de pesanteur fendus à la base ou à une taille. En ligne : oapekau@civil.concordia.ca, xue_zhu@civil.concordia.ca