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

Caisson foundations subjected to reverse fault rupture / M. Loli in Journal of geotechnical and geoenvironmental engineering, Vol. 137 N° 10 (Octobre 2011) 

Public ISBD [article]  in Journal of geotechnical and geoenvironmental engineering > Vol. 137 N° 10 (Octobre 2011) . - pp. 914-925 Titre : Caisson foundations subjected to reverse fault rupture : centrifuge testing and numerical analysis Type de document : texte imprimé Auteurs : M. Loli, Auteur ; I. Anastasopoulos, Auteur ; M. F. Bransby, Auteur Année de publication : 2012 Article en page(s) : pp. 914-925 Note générale : Géotechnique Langues : Anglais (eng) Mots-clés : Thrust  fault  Finite  elements  3D  analysis  Caisson  foundations  Centrifuge  modeling  Soil-caisson-rupture  interaction  Tectonic  deformation Index. décimale : 624.1 Infrastructures.Ouvrages en terre. Fondations. Tunnels Résumé : Recent large-magnitude (M>7) earthquakes have caused numerous failures induced by surface faulting, demonstrating the need to account for tectonic deformation in seismic design. Thanks to their usually high rigidity, embedded (e.g., caisson) foundations may divert the fault rupture and lead to favorable performance, whereas surface or piled foundations may fail. We present a series of centrifuge model tests to investigate the response of caisson foundations embedded in a cohesionless soil stratum, the base of which is subjected to reverse faulting. We elucidate the interplay between the propagating fault rupture and the caisson, focusing on the role of the location of the outcropping rupture relative to the caisson. The rigid-body of the caisson causes diversion and/or bifurcation of the shear localization, which is forced to develop preferentially around the edges of the caisson. The observed failure pattern and the consequent caisson response depend strongly on the exact caisson position relative to the fault. We employed three-dimensional (3D) finite-element (FE) modeling and validated it by comparing to centrifuge test results. The numerical method captures the general interaction mechanisms, showing satisfactory (if not always perfect) agreement with experiments. We then employ the validated numerical method in a parametric investigation, providing further insight into the different possible modes of foundation response. DEWEY : 624.1 ISSN : 1090-0241 En ligne : http://ascelibrary.org/gto/resource/1/jggefk/v137/i10/p914_s1?isAuthorized=no [article] Caisson foundations subjected to reverse fault rupture : centrifuge testing and numerical analysis [texte imprimé] / M. Loli, Auteur ; I. Anastasopoulos, Auteur ; M. F. Bransby, Auteur . - 2012 . - pp. 914-925. Géotechnique Langues : Anglais (eng) in Journal of geotechnical and geoenvironmental engineering > Vol. 137 N° 10 (Octobre 2011) . - pp. 914-925 Mots-clés : Thrust  fault  Finite  elements  3D  analysis  Caisson  foundations  Centrifuge  modeling  Soil-caisson-rupture  interaction  Tectonic  deformation Index. décimale : 624.1 Infrastructures.Ouvrages en terre. Fondations. Tunnels Résumé : Recent large-magnitude (M>7) earthquakes have caused numerous failures induced by surface faulting, demonstrating the need to account for tectonic deformation in seismic design. Thanks to their usually high rigidity, embedded (e.g., caisson) foundations may divert the fault rupture and lead to favorable performance, whereas surface or piled foundations may fail. We present a series of centrifuge model tests to investigate the response of caisson foundations embedded in a cohesionless soil stratum, the base of which is subjected to reverse faulting. We elucidate the interplay between the propagating fault rupture and the caisson, focusing on the role of the location of the outcropping rupture relative to the caisson. The rigid-body of the caisson causes diversion and/or bifurcation of the shear localization, which is forced to develop preferentially around the edges of the caisson. The observed failure pattern and the consequent caisson response depend strongly on the exact caisson position relative to the fault. We employed three-dimensional (3D) finite-element (FE) modeling and validated it by comparing to centrifuge test results. The numerical method captures the general interaction mechanisms, showing satisfactory (if not always perfect) agreement with experiments. We then employ the validated numerical method in a parametric investigation, providing further insight into the different possible modes of foundation response. DEWEY : 624.1 ISSN : 1090-0241 En ligne : http://ascelibrary.org/gto/resource/1/jggefk/v137/i10/p914_s1?isAuthorized=no

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

Hybrid method for analysis and design of slope stabilizing piles / R. Kourkoulis in Journal of geotechnical and geoenvironmental engineering, Vol. 138 N° 1 (Janvier 2012) 

Public ISBD [article]  in Journal of geotechnical and geoenvironmental engineering > Vol. 138 N° 1 (Janvier 2012) . - pp. 1-14 Titre : Hybrid method for analysis and design of slope stabilizing piles Type de document : texte imprimé Auteurs : R. Kourkoulis, Auteur ; F. Gelagoti, Auteur ; I. Anastasopoulos, Auteur Année de publication : 2012 Article en page(s) : pp. 1-14 Note générale : Géotechnique Langues : Anglais (eng) Mots-clés : Slope  stability  Soil-structure  interaction  Pile  groups  Validation  against  experiments  Simplified  method  Field  tests Résumé : Piles are extensively used as a means of slope stabilization. Despite the rapid advances in computing and software power, the design of such piles may still include a high degree of conservatism, stemming from the use of simplified, easy-to-apply methodologies. This paper develops a hybrid method for designing slope-stabilizing piles, combining the accuracy of rigorous three-dimensional (3D) finite-element (FE) simulation with the simplicity of widely accepted analytical techniques. It consists of two steps: (1) evaluation of the lateral resisting force (RF) needed to increase the safety factor of the precarious slope to the desired value, and (2) estimation of the optimum pile configuration that offers the required RF for a prescribed deformation level. The first step utilizes the results of conventional slope-stability analysis. A novel approach is proposed for the second step. This consists of decoupling the slope geometry from the computation of pile lateral capacity, which allows numerical simulation of only a limited region of soil around the piles. A comprehensive validation is presented against published experimental, field, and theoretical results from fully coupled 3D nonlinear FE analyses. The proposed method provides a useful, computationally efficient tool for parametric analyses and design of slope-stabilizing piles. DEWEY : 624.1 ISSN : 1090-0241 En ligne : http://ascelibrary.org/gto/resource/1/jggefk/v138/i1/p1_s1?isAuthorized=no [article] Hybrid method for analysis and design of slope stabilizing piles [texte imprimé] / R. Kourkoulis, Auteur ; F. Gelagoti, Auteur ; I. Anastasopoulos, Auteur . - 2012 . - pp. 1-14. Géotechnique Langues : Anglais (eng) in Journal of geotechnical and geoenvironmental engineering > Vol. 138 N° 1 (Janvier 2012) . - pp. 1-14 Mots-clés : Slope  stability  Soil-structure  interaction  Pile  groups  Validation  against  experiments  Simplified  method  Field  tests Résumé : Piles are extensively used as a means of slope stabilization. Despite the rapid advances in computing and software power, the design of such piles may still include a high degree of conservatism, stemming from the use of simplified, easy-to-apply methodologies. This paper develops a hybrid method for designing slope-stabilizing piles, combining the accuracy of rigorous three-dimensional (3D) finite-element (FE) simulation with the simplicity of widely accepted analytical techniques. It consists of two steps: (1) evaluation of the lateral resisting force (RF) needed to increase the safety factor of the precarious slope to the desired value, and (2) estimation of the optimum pile configuration that offers the required RF for a prescribed deformation level. The first step utilizes the results of conventional slope-stability analysis. A novel approach is proposed for the second step. This consists of decoupling the slope geometry from the computation of pile lateral capacity, which allows numerical simulation of only a limited region of soil around the piles. A comprehensive validation is presented against published experimental, field, and theoretical results from fully coupled 3D nonlinear FE analyses. The proposed method provides a useful, computationally efficient tool for parametric analyses and design of slope-stabilizing piles. DEWEY : 624.1 ISSN : 1090-0241 En ligne : http://ascelibrary.org/gto/resource/1/jggefk/v138/i1/p1_s1?isAuthorized=no

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 [...]

Simplified constitutive model for simulation of cyclic response of shallow foundations / I. Anastasopoulos in Journal of geotechnical and geoenvironmental engineering, Vol. 137 N° 12 (Décembre 2011) 

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Slope stabilizing piles and pile-groups / R. Kourkoulis in Journal of geotechnical and geoenvironmental engineering, Vol. 137 N° 7 (Juillet 2011) 

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