Documents disponibles écrits par cet auteur

Asymmetric ‘Newmark' sliding caused by motions containing severe ‘directivity' and ‘fling' pulses / E. Garini in Géotechnique, Vol. 61 N° 9 (Septembre 2011) 

Public ISBD [article]  in Géotechnique > Vol. 61 N° 9 (Septembre 2011) . - pp. 733-756 Titre : Asymmetric ‘Newmark' sliding caused by motions containing severe ‘directivity' and ‘fling' pulses Type de document : texte imprimé Auteurs : E. Garini, Auteur ; G. Gazetas, Auteur ; I. Anastasopoulos, Auteur Année de publication : 2011 Article en page(s) : pp. 733-756 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Embankments  Earthquakes  Retaining  walls  Slopes Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : Sliding of a rigid mass supported on an inclined, seismically shaking plane serves as a conceptual and computational model for a variety of problems in geotechnical earthquake engineering. A series of parametric analyses are presented in the paper using as excitation numerous near-fault-recorded severe ground motions and idealised wavelets, bearing the effects of ‘forward-directivity' and ‘fling-step'. Using as key parameters the angle β of the sloping plane (mimicking the sliding surface), as well as the frequency content, intensity, nature and polarity of the excitation, the paper aims at developing a deeper insight into the mechanics of the asymmetric sliding process and the role of key parameters of the excitation. It is shown that ‘directivity' and ‘fling' affected motions containing long-period acceleration pulses and large velocity steps, are particularly ‘destructive' for the examined systems. The amount of accumulating slip on a steep slope is particularly sensitive to reversal of the polarity of excitation. With some special ground motions, in particular (such as the Sakarya and Yarimca accelerograms, both recorded 3 km from the surface expression of the North Anatolian Fault that ruptured in the 1999 Kocaeli earthquake), what might at first glance appear elusively as ‘small details' in the record may turn out to exert a profound influence on the magnitude of slippage – far outweighing the effects of peak acceleration, peak velocity and Arias intensity. The results are compiled in both dimensionless and dimensional charts, and compared with classical charts from the literature. Finally, it is shown that no convincingly robust correlation could exist between accumulated slip and the Arias intensity of excitation. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.9.p.070 [article] Asymmetric ‘Newmark' sliding caused by motions containing severe ‘directivity' and ‘fling' pulses [texte imprimé] / E. Garini, Auteur ; G. Gazetas, Auteur ; I. Anastasopoulos, Auteur . - 2011 . - pp. 733-756. Génie Civil Langues : Anglais (eng) in Géotechnique > Vol. 61 N° 9 (Septembre 2011) . - pp. 733-756 Mots-clés : Embankments  Earthquakes  Retaining  walls  Slopes Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : Sliding of a rigid mass supported on an inclined, seismically shaking plane serves as a conceptual and computational model for a variety of problems in geotechnical earthquake engineering. A series of parametric analyses are presented in the paper using as excitation numerous near-fault-recorded severe ground motions and idealised wavelets, bearing the effects of ‘forward-directivity' and ‘fling-step'. Using as key parameters the angle β of the sloping plane (mimicking the sliding surface), as well as the frequency content, intensity, nature and polarity of the excitation, the paper aims at developing a deeper insight into the mechanics of the asymmetric sliding process and the role of key parameters of the excitation. It is shown that ‘directivity' and ‘fling' affected motions containing long-period acceleration pulses and large velocity steps, are particularly ‘destructive' for the examined systems. The amount of accumulating slip on a steep slope is particularly sensitive to reversal of the polarity of excitation. With some special ground motions, in particular (such as the Sakarya and Yarimca accelerograms, both recorded 3 km from the surface expression of the North Anatolian Fault that ruptured in the 1999 Kocaeli earthquake), what might at first glance appear elusively as ‘small details' in the record may turn out to exert a profound influence on the magnitude of slippage – far outweighing the effects of peak acceleration, peak velocity and Arias intensity. The results are compiled in both dimensionless and dimensional charts, and compared with classical charts from the literature. Finally, it is shown that no convincingly robust correlation could exist between accumulated slip and the Arias intensity of excitation. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.9.p.070

Closure to “Seismic behavior of batter piles: elastic response” by A. Giannakou, N. Gerolymos, G. Gazetas, T. Tazoh, and I. Anastasopoulos / A. Giannakou in Journal of geotechnical and geoenvironmental engineering, Vol. 139 N° 1 (Janvier 2013) 

Public ISBD [article]  in Journal of geotechnical and geoenvironmental engineering > Vol. 139 N° 1 (Janvier 2013) . - pp. 186–187 Titre : Closure to “Seismic behavior of batter piles: elastic response” by A. Giannakou, N. Gerolymos, G. Gazetas, T. Tazoh, and I. Anastasopoulos Type de document : texte imprimé Auteurs : A. Giannakou, Auteur ; N. Gerolymos, Auteur ; G. Gazetas, Auteur Année de publication : 2013 Article en page(s) : pp. 186–187 Note générale : geotechnique Langues : Anglais (eng) En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29GT.1943-5606.0000673 [article] Closure to “Seismic behavior of batter piles: elastic response” by A. Giannakou, N. Gerolymos, G. Gazetas, T. Tazoh, and I. Anastasopoulos [texte imprimé] / A. Giannakou, Auteur ; N. Gerolymos, Auteur ; G. Gazetas, Auteur . - 2013 . - pp. 186–187. geotechnique Langues : Anglais (eng) in Journal of geotechnical and geoenvironmental engineering > Vol. 139 N° 1 (Janvier 2013) . - pp. 186–187 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29GT.1943-5606.0000673

Effects of near-fault ground shaking on sliding systems / G. Gazetas in Journal of geotechnical and geoenvironmental engineering, Vol. 135 N° 12 (Décembre 2009) 

Public ISBD [article]  in Journal of geotechnical and geoenvironmental engineering > Vol. 135 N° 12 (Décembre 2009) . - pp. 1906–1921 Titre : Effects of near-fault ground shaking on sliding systems Type de document : texte imprimé Auteurs : G. Gazetas, Auteur ; E. Garini, Auteur ; I. Anastasopoulos, Auteur Année de publication : 2010 Article en page(s) : pp. 1906–1921 Note générale : Geotechnical and geoenvironmental engineering Langues : Anglais (eng) Mots-clés : SlidingSeismic  effectsGround  motionSymmetryAsymmetry Résumé : A numerical study is presented for a rigid block supported through a frictional contact surface on a horizontal or an inclined plane, and subjected to horizontal or slope-parallel excitation. The latter is described with idealized pulses and near-fault seismic records strongly influenced by forward-directivity or fling-step effects (from Northridge, Kobe, Kocaeli, Chi-Chi, Aegion). In addition to the well known dependence of the resulting block slippage on variables such as the peak base velocity, the peak base acceleration, and the critical acceleration ratio, our study has consistently and repeatedly revealed a profound sensitivity of both maximum and residual slippage: (1) on the sequence and even the details of the pulses contained in the excitation and (2) on the direction ( + or −) in which the shaking of the inclined plane is imposed. By contrast, the slippage is not affected to any measurable degree by even the strongest vertical components of the accelerograms. Moreover, the slippage from a specific record may often be poorly correlated with its Arias intensity. These findings may contradict some of the prevailing beliefs that emanate from statistical correlation studies. The upper-bound sliding displacements from near-fault excitations may substantially exceed the values obtained from some of the currently available design charts. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29GT.1943-5606.0000174 [article] Effects of near-fault ground shaking on sliding systems [texte imprimé] / G. Gazetas, Auteur ; E. Garini, Auteur ; I. Anastasopoulos, Auteur . - 2010 . - pp. 1906–1921. Geotechnical and geoenvironmental engineering Langues : Anglais (eng) in Journal of geotechnical and geoenvironmental engineering > Vol. 135 N° 12 (Décembre 2009) . - pp. 1906–1921 Mots-clés : SlidingSeismic  effectsGround  motionSymmetryAsymmetry Résumé : A numerical study is presented for a rigid block supported through a frictional contact surface on a horizontal or an inclined plane, and subjected to horizontal or slope-parallel excitation. The latter is described with idealized pulses and near-fault seismic records strongly influenced by forward-directivity or fling-step effects (from Northridge, Kobe, Kocaeli, Chi-Chi, Aegion). In addition to the well known dependence of the resulting block slippage on variables such as the peak base velocity, the peak base acceleration, and the critical acceleration ratio, our study has consistently and repeatedly revealed a profound sensitivity of both maximum and residual slippage: (1) on the sequence and even the details of the pulses contained in the excitation and (2) on the direction ( + or −) in which the shaking of the inclined plane is imposed. By contrast, the slippage is not affected to any measurable degree by even the strongest vertical components of the accelerograms. Moreover, the slippage from a specific record may often be poorly correlated with its Arias intensity. These findings may contradict some of the prevailing beliefs that emanate from statistical correlation studies. The upper-bound sliding displacements from near-fault excitations may substantially exceed the values obtained from some of the currently available design charts. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29GT.1943-5606.0000174

Normal fault rupture interaction with strip foundations / I. Anastasopoulos in Journal of geotechnical and geoenvironmental engineering, Vol. 135 N°3 (Mars 2009) 

Public ISBD [article]  in Journal of geotechnical and geoenvironmental engineering > Vol. 135 N°3 (Mars 2009) . - pp. 359–370 Titre : Normal fault rupture interaction with strip foundations Type de document : texte imprimé Auteurs : I. Anastasopoulos, Auteur ; G. Gazetas, Auteur ; M. F. Bransby, Auteur Année de publication : 2009 Article en page(s) : pp. 359–370 Note générale : Geotechnical and geoenvironmental engineering Langues : Anglais (eng) Mots-clés : Geological  faults  Soil-structure  interaction  Finite  element  method  Centrifuge  models  Seismic  effects  Foundations Résumé : Observations after earthquakes where surface fault ruptures crossed engineering facilities reveal that some structures survived the rupture almost unscathed. In some cases, the rupture path appears to divert, “avoiding” the structure. Such observations point to an interaction between the propagating rupture, the soil, and the foundation. This paper (i) develops a two-step nonlinear finite-element methodology to study rupture propagation and its interaction with strip foundations; (ii) provides validation through successful Class “A” predictions of centrifuge model tests; and (iii) conducts a parameter study on the interaction of strip foundations with normal fault ruptures. It is shown that a heavily loaded foundation can substantially divert the rupture path, which may avoid outcropping underneath the foundation. The latter undergoes rigid body rotation, often detaching from the soil. Its distress arises mainly from the ensuing loss of support that takes place either at the edges or around its center. The average pressure q on the foundation largely dictates the width of such unsupported spans. Increasing q decreases the unsupported width, reducing foundation distress. The role of q is dual: (1) it compresses the soil, “flattening” fault-induced surface “anomalies”; and (2) it changes the stress field underneath the foundation, facilitating rupture diversion. However, even if the rupture is diverted, the foundation may undergo significant stressing, depending on its position relative to the fault outcrop. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282009%29135%3A3%2835 [...] [article] Normal fault rupture interaction with strip foundations [texte imprimé] / I. Anastasopoulos, Auteur ; G. Gazetas, Auteur ; M. F. Bransby, Auteur . - 2009 . - pp. 359–370. Geotechnical and geoenvironmental engineering Langues : Anglais (eng) in Journal of geotechnical and geoenvironmental engineering > Vol. 135 N°3 (Mars 2009) . - pp. 359–370 Mots-clés : Geological  faults  Soil-structure  interaction  Finite  element  method  Centrifuge  models  Seismic  effects  Foundations Résumé : Observations after earthquakes where surface fault ruptures crossed engineering facilities reveal that some structures survived the rupture almost unscathed. In some cases, the rupture path appears to divert, “avoiding” the structure. Such observations point to an interaction between the propagating rupture, the soil, and the foundation. This paper (i) develops a two-step nonlinear finite-element methodology to study rupture propagation and its interaction with strip foundations; (ii) provides validation through successful Class “A” predictions of centrifuge model tests; and (iii) conducts a parameter study on the interaction of strip foundations with normal fault ruptures. It is shown that a heavily loaded foundation can substantially divert the rupture path, which may avoid outcropping underneath the foundation. The latter undergoes rigid body rotation, often detaching from the soil. Its distress arises mainly from the ensuing loss of support that takes place either at the edges or around its center. The average pressure q on the foundation largely dictates the width of such unsupported spans. Increasing q decreases the unsupported width, reducing foundation distress. The role of q is dual: (1) it compresses the soil, “flattening” fault-induced surface “anomalies”; and (2) it changes the stress field underneath the foundation, facilitating rupture diversion. However, even if the rupture is diverted, the foundation may undergo significant stressing, depending on its position relative to the fault outcrop. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282009%29135%3A3%2835 [...]

Seismic behavior of batter piles / A. Giannakou in Journal of geotechnical and geoenvironmental engineering, Vol. 136 N° 9 (Septembre 2010) 

Public ISBD [article]  in Journal of geotechnical and geoenvironmental engineering > Vol. 136 N° 9 (Septembre 2010) . - pp. 1187-1199 Titre : Seismic behavior of batter piles : elastic response Type de document : texte imprimé Auteurs : A. Giannakou, Auteur ; N. Gerolymos, Auteur ; G. Gazetas, Auteur Année de publication : 2010 Article en page(s) : pp. 1187-1199 Note générale : Géotechnique Langues : Anglais (eng) Mots-clés : Batter  piles  Lateral  loading  Seismic  response  Numerical  modeling  Kinematic  response  Inertial  response  Soil-structure  interaction Index. décimale : 624.1 Infrastructures.Ouvrages en terre. Fondations. Tunnels Résumé : Several aspects of the seismic response of groups containing nonvertical piles are studied, including the lateral pile-head stiffnesses, the “kinematic” pile deformation, and the “inertial” soil-pile-structure response. A key goal is to explore the conditions under which the presence of batter piles is beneficial, indifferent, or detrimental. Parametric analyses are carried out using three-dimensional finite-element modeling, assuming elastic behavior of soil, piles, and superstructure. The model is first used to obtain the lateral stiffnesses of single batter piles and to show that its results converge to the available solutions from the literature. Then, real accelerograms covering a broad range of frequency characteristics are employed as base excitation of simple fixed-head two-pile group configurations, embedded in homogeneous, inhomogeneous, and layered soil profiles, while supporting very tall or very short structures. Five pile inclinations are considered while the corresponding vertical-pile group results serve as reference. It is found that in purely kinematic seismic loading, batter piles tend to confirm their negative reputation, as had also been found recently for a group subjected to static horizontal ground deformation. However, the total (kinematic plus inertial) response of structural systems founded on groups of batter piles offers many reasons for optimism. Batter piles may indeed be beneficial (or detrimental) depending on, among other parameters, the relative size of the overturning moment versus the shear force transmitted onto them from the superstructure. DEWEY : 624.1 ISSN : 1090-0241 En ligne : http://ascelibrary.org/gto/resource/1/jggefk/v136/i9/p1187_s1?isAuthorized=no [article] Seismic behavior of batter piles : elastic response [texte imprimé] / A. Giannakou, Auteur ; N. Gerolymos, Auteur ; G. Gazetas, Auteur . - 2010 . - pp. 1187-1199. Géotechnique Langues : Anglais (eng) in Journal of geotechnical and geoenvironmental engineering > Vol. 136 N° 9 (Septembre 2010) . - pp. 1187-1199 Mots-clés : Batter  piles  Lateral  loading  Seismic  response  Numerical  modeling  Kinematic  response  Inertial  response  Soil-structure  interaction Index. décimale : 624.1 Infrastructures.Ouvrages en terre. Fondations. Tunnels Résumé : Several aspects of the seismic response of groups containing nonvertical piles are studied, including the lateral pile-head stiffnesses, the “kinematic” pile deformation, and the “inertial” soil-pile-structure response. A key goal is to explore the conditions under which the presence of batter piles is beneficial, indifferent, or detrimental. Parametric analyses are carried out using three-dimensional finite-element modeling, assuming elastic behavior of soil, piles, and superstructure. The model is first used to obtain the lateral stiffnesses of single batter piles and to show that its results converge to the available solutions from the literature. Then, real accelerograms covering a broad range of frequency characteristics are employed as base excitation of simple fixed-head two-pile group configurations, embedded in homogeneous, inhomogeneous, and layered soil profiles, while supporting very tall or very short structures. Five pile inclinations are considered while the corresponding vertical-pile group results serve as reference. It is found that in purely kinematic seismic loading, batter piles tend to confirm their negative reputation, as had also been found recently for a group subjected to static horizontal ground deformation. However, the total (kinematic plus inertial) response of structural systems founded on groups of batter piles offers many reasons for optimism. Batter piles may indeed be beneficial (or detrimental) depending on, among other parameters, the relative size of the overturning moment versus the shear force transmitted onto them from the superstructure. DEWEY : 624.1 ISSN : 1090-0241 En ligne : http://ascelibrary.org/gto/resource/1/jggefk/v136/i9/p1187_s1?isAuthorized=no