Documents disponibles écrits par cet auteur

Earthquake safety evaluation of gravity dams considering aftershocks and reduced drainage efficiency / Pierre-Marie Alliard in Journal of engineering mechanics, Vol. 134 N°1 (Janvier 2008) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 134 N°1 (Janvier 2008) . - pp.12–22. Titre : Earthquake safety evaluation of gravity dams considering aftershocks and reduced drainage efficiency Type de document : texte imprimé Auteurs : Pierre-Marie Alliard, Auteur ; Pierre Léger, Auteur Année de publication : 2008 Article en page(s) : pp.12–22. Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Dam  safety  Uplift  pressure  Sliding  Displacement  Seismic  effects  Dilatancy  Hydromechanics Résumé : This paper develops a methodology to perform seismic response analyses of concrete gravity dams considering aftershocks, and reduced drainage efficiency due to disruption of the drainage system. A database of earthquake records has been assembled to characterize main shocks and aftershocks. A drain finite difference hydraulic model considering laminar or turbulent two-dimensional flow in connecting cracks, geometrical distortions due to joint dilatancy while sliding, and misaligned drain segments is developed and validated. Coupled-hydromechanical analyses on the seismic response of a drained 90m gravity dam are used to show the importance of cumulative displacements on the increase in uplift pressures, drain flow, and reduced sliding safety factors. Aftershock response is especially sensitive to the drainage system dimensions and model parameters, such as the foundation stiffness, and the number of potentially sliding joints. The proposed methodology forms the basis to develop displacement based performance criteria in stability evaluation of existing dams reevaluated for much higher ground motions intensities that they have been designed for many years ago. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282008%29134%3A1%2812 [...] [article] Earthquake safety evaluation of gravity dams considering aftershocks and reduced drainage efficiency [texte imprimé] / Pierre-Marie Alliard, Auteur ; Pierre Léger, Auteur . - 2008 . - pp.12–22. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 134 N°1 (Janvier 2008) . - pp.12–22. Mots-clés : Dam  safety  Uplift  pressure  Sliding  Displacement  Seismic  effects  Dilatancy  Hydromechanics Résumé : This paper develops a methodology to perform seismic response analyses of concrete gravity dams considering aftershocks, and reduced drainage efficiency due to disruption of the drainage system. A database of earthquake records has been assembled to characterize main shocks and aftershocks. A drain finite difference hydraulic model considering laminar or turbulent two-dimensional flow in connecting cracks, geometrical distortions due to joint dilatancy while sliding, and misaligned drain segments is developed and validated. Coupled-hydromechanical analyses on the seismic response of a drained 90m gravity dam are used to show the importance of cumulative displacements on the increase in uplift pressures, drain flow, and reduced sliding safety factors. Aftershock response is especially sensitive to the drainage system dimensions and model parameters, such as the foundation stiffness, and the number of potentially sliding joints. The proposed methodology forms the basis to develop displacement based performance criteria in stability evaluation of existing dams reevaluated for much higher ground motions intensities that they have been designed for many years ago. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282008%29134%3A1%2812 [...]

Gyroscopes mécaniques vibrants / Pierre Léger

Public ISBD in Techniques de l'ingénieur : mesures mécanique et dimensionnelles Ti673. Grandeurs mécaniques / Jean-Luc Bodnar  Titre : Gyroscopes mécaniques vibrants : réf. internet R1942 Type de document : texte imprimé Auteurs : Pierre Léger, Auteur Année de publication : 1999 Importance : p.183-190 Note générale : Bibliogr. p.189 Langues : Français (fre) Mots-clés : Gyroscope Corps  vibrant Note de contenu : Sommaire: 1. Définitions et principes 2. Les deux classes de gyroscopes vibrants 3. Oscillateur linéaire deux axes. Coefficient de bryan 4. Electronique de contrôle des gyroscopes vibrants 5. Exemples d’appareils in Techniques de l'ingénieur : mesures mécanique et dimensionnelles Ti673. Grandeurs mécaniques / Jean-Luc Bodnar  Gyroscopes mécaniques vibrants : réf. internet R1942 [texte imprimé] / Pierre Léger, Auteur . - 1999 . - p.183-190. Bibliogr. p.189 Langues : Français (fre) Mots-clés : Gyroscope Corps  vibrant Note de contenu : Sommaire: 1. Définitions et principes 2. Les deux classes de gyroscopes vibrants 3. Oscillateur linéaire deux axes. Coefficient de bryan 4. Electronique de contrôle des gyroscopes vibrants 5. Exemples d’appareils

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Hydrostatic, temperature, time-displacement model for concrete dams / Pierre Léger in Journal of engineering mechanics, Vol. 133 N°3 (Mars 2007) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 133 N°3 (Mars 2007) . - pp.267–277. Titre : Hydrostatic, temperature, time-displacement model for concrete dams Type de document : texte imprimé Auteurs : Pierre Léger, Auteur ; Martin Leclerc, Auteur Année de publication : 2007 Article en page(s) : pp.267–277. Note générale : Applied mechanics Langues : Anglais (eng) Mots-clés : Dams  concrete  Thermal  factors  Heat  transfer  Displacement  Instrumentation Résumé : This paper presents frequency domain solution algorithms of the one-dimensional transient heat transfer equation that describes temperature variations in arch dam cross sections. Algorithms are developed to compute the temperature T(x,t) , spatial distribution, and time evolution for the “direct” problem, where the temperature variations are specified at the upstream and downstream faces, and for the “inverse” problem, where temperatures have been measured at thermometers located inside instrumented dam sections. The resulting nonlinear temperature field is decomposed in an effective average temperature, Tm(t) , and a linear temperature difference, Tg(x,t) , from which the dam thermal displacement response can be deducted. The proposed frequency domain solution procedures are able to reproduce an arbitrary transient heat response by appending trailing temperatures at the end of thermal signals, thus transforming a periodic heat transfer problem in a transient one. The frequency domain solution procedures are used to develop the HTT (hydrostatic, temperature, time) statistical model to interpret concrete dam-recorded pendulum displacements. In the HTT model, the thermal loads are arbitrary and can contain temperature drift or unusual temperature conditions. The explicit use of Tm(t) and Tg(x,t) in the HTT dam displacement model allows extrapolation for temperature conditions that have never been experienced by the dam before (within the assumption of elastic behavior). The HTT model is applied to the 131-m-high Schlegeis arch dam, and the results are compared with the HST (hydrostatic, seasonal, time) displacement model that is widely used in practice. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282007%29133%3A3%2826 [...] [article] Hydrostatic, temperature, time-displacement model for concrete dams [texte imprimé] / Pierre Léger, Auteur ; Martin Leclerc, Auteur . - 2007 . - pp.267–277. Applied mechanics Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 133 N°3 (Mars 2007) . - pp.267–277. Mots-clés : Dams  concrete  Thermal  factors  Heat  transfer  Displacement  Instrumentation Résumé : This paper presents frequency domain solution algorithms of the one-dimensional transient heat transfer equation that describes temperature variations in arch dam cross sections. Algorithms are developed to compute the temperature T(x,t) , spatial distribution, and time evolution for the “direct” problem, where the temperature variations are specified at the upstream and downstream faces, and for the “inverse” problem, where temperatures have been measured at thermometers located inside instrumented dam sections. The resulting nonlinear temperature field is decomposed in an effective average temperature, Tm(t) , and a linear temperature difference, Tg(x,t) , from which the dam thermal displacement response can be deducted. The proposed frequency domain solution procedures are able to reproduce an arbitrary transient heat response by appending trailing temperatures at the end of thermal signals, thus transforming a periodic heat transfer problem in a transient one. The frequency domain solution procedures are used to develop the HTT (hydrostatic, temperature, time) statistical model to interpret concrete dam-recorded pendulum displacements. In the HTT model, the thermal loads are arbitrary and can contain temperature drift or unusual temperature conditions. The explicit use of Tm(t) and Tg(x,t) in the HTT dam displacement model allows extrapolation for temperature conditions that have never been experienced by the dam before (within the assumption of elastic behavior). The HTT model is applied to the 131-m-high Schlegeis arch dam, and the results are compared with the HST (hydrostatic, seasonal, time) displacement model that is widely used in practice. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282007%29133%3A3%2826 [...]

Shake table testing of slender RC shear walls subjected to eastern north america seismic ground motions / Iman Ghorbanirenani in Journal of structural engineering, Vol. 138 N° 12 (Décembre 2012) 

Public ISBD [article]  in Journal of structural engineering > Vol. 138 N° 12 (Décembre 2012) . - pp. 1515–1529 Titre : Shake table testing of slender RC shear walls subjected to eastern north america seismic ground motions Type de document : texte imprimé Auteurs : Iman Ghorbanirenani, Auteur ; Robert Tremblay, Auteur ; Pierre Léger, Auteur Année de publication : 2013 Article en page(s) : pp. 1515–1529 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Ductility  Dynamic  Experimental  tests  Higher  modes  Inelastic  response  Seismic  responses  Shear  wall Résumé : This paper presents shake table test results on two identical 1:0.429 scaled, 8-story moderately ductile RC shear wall specimens under the expected high-frequency ground motion in eastern North America. The walls were designed and detailed according to the seismic provisions of the NBCC 2005 and CSA-A23.3-04 standards. The objectives were to validate and understand the inelastic responses and interaction of shear and flexure and axial loads in the plastic hinge zones of the walls taking into consideration the higher-mode effects. One specimen was tested under incremental ground motion intensities ranging from 40 to 120% of the design level. The intensity range was increased from 100 to 200% for the second specimen. The response of the walls was significantly affected by the second mode, causing an inelastic flexural response to develop at the base as well as at the sixth level. Dynamic amplification of the base shear forces was also observed in both walls. In the second wall, which was tested in the undamaged condition, peak base shear forces occurred prior to significant inelastic rotation and the contribution to concrete of shear resistance exceeded the value used in the design. Once inelastic rotation had developed that contribution corresponded to the value obtained using a value of 0.18 for the reduction factor accounting for concrete cracking. Inelastic rotation in the upper wall region was found to limit the force demand imposed by the higher-mode response. ISSN : 0733-9445 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29ST.1943-541X.0000581 [article] Shake table testing of slender RC shear walls subjected to eastern north america seismic ground motions [texte imprimé] / Iman Ghorbanirenani, Auteur ; Robert Tremblay, Auteur ; Pierre Léger, Auteur . - 2013 . - pp. 1515–1529. Génie Civil Langues : Anglais (eng) in Journal of structural engineering > Vol. 138 N° 12 (Décembre 2012) . - pp. 1515–1529 Mots-clés : Ductility  Dynamic  Experimental  tests  Higher  modes  Inelastic  response  Seismic  responses  Shear  wall Résumé : This paper presents shake table test results on two identical 1:0.429 scaled, 8-story moderately ductile RC shear wall specimens under the expected high-frequency ground motion in eastern North America. The walls were designed and detailed according to the seismic provisions of the NBCC 2005 and CSA-A23.3-04 standards. The objectives were to validate and understand the inelastic responses and interaction of shear and flexure and axial loads in the plastic hinge zones of the walls taking into consideration the higher-mode effects. One specimen was tested under incremental ground motion intensities ranging from 40 to 120% of the design level. The intensity range was increased from 100 to 200% for the second specimen. The response of the walls was significantly affected by the second mode, causing an inelastic flexural response to develop at the base as well as at the sixth level. Dynamic amplification of the base shear forces was also observed in both walls. In the second wall, which was tested in the undamaged condition, peak base shear forces occurred prior to significant inelastic rotation and the contribution to concrete of shear resistance exceeded the value used in the design. Once inelastic rotation had developed that contribution corresponded to the value obtained using a value of 0.18 for the reduction factor accounting for concrete cracking. Inelastic rotation in the upper wall region was found to limit the force demand imposed by the higher-mode response. ISSN : 0733-9445 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29ST.1943-541X.0000581

Three-dimensional hydromechanical sectional analysis of cracked nonprismatic concrete spillway piers / Lucian Stefan in Journal of structural engineering, Vol. 138 N° 11 (Novembre 2012) 

Public ISBD [article]  in Journal of structural engineering > Vol. 138 N° 11 (Novembre 2012) . - pp. 1310–1320 Titre : Three-dimensional hydromechanical sectional analysis of cracked nonprismatic concrete spillway piers Type de document : texte imprimé Auteurs : Lucian Stefan, Auteur ; Pierre Léger, Auteur Année de publication : 2013 Article en page(s) : pp. 1310–1320 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Hydraulic  structures  Concrete  structures  Three-dimensional  models  Stress  analysis  Cracking  Bending  Shear  forces  Torsion Résumé : Several concrete hydraulic structures, such as spillway piers, must be considered three-dimensional (3D) components subjected to 3D loads. A very convenient approach to perform stability analysis of concrete dams is the so-called gravity method, leading to the solution of a PMM problem (axial force P and biaxial bending moments Mx, My) assuming linear normal stress distribution. If cracking takes place, water penetrates into the cracks, inducing the development of full uplift pressures (UPs). Sliding safety factors (SSFs) are computed using shear force resultants Vx, Vy, and a Mohr-Coulomb failure criterion while ignoring torsion T (VVT). This paper presents a 3D extension of the gravity method for cracked planar concrete sections of arbitrary geometry subjected to arbitrary loads (PMM-VVT). To compute the shear stress distribution, a VVT sectional analysis algorithm has been developed based on the theory of elasticity (TE), including Saint-Venant and warping torsional components combined with triangular 2D finite elements (FEs). Afterward, the SSF on the failure plane is computed from the integration of normal stresses on the remaining uncracked area where the Mohr-Coulomb criterion (considering the shear stresses from the VVT solution) has not been locally exceeded. Two validation examples and a case study of an actual pier are presented to illustrate the accuracy and efficiency of the proposed approach compared with full 3D FE analyses. ISSN : 0733-9445 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29ST.1943-541X.0000579 [article] Three-dimensional hydromechanical sectional analysis of cracked nonprismatic concrete spillway piers [texte imprimé] / Lucian Stefan, Auteur ; Pierre Léger, Auteur . - 2013 . - pp. 1310–1320. Génie Civil Langues : Anglais (eng) in Journal of structural engineering > Vol. 138 N° 11 (Novembre 2012) . - pp. 1310–1320 Mots-clés : Hydraulic  structures  Concrete  structures  Three-dimensional  models  Stress  analysis  Cracking  Bending  Shear  forces  Torsion Résumé : Several concrete hydraulic structures, such as spillway piers, must be considered three-dimensional (3D) components subjected to 3D loads. A very convenient approach to perform stability analysis of concrete dams is the so-called gravity method, leading to the solution of a PMM problem (axial force P and biaxial bending moments Mx, My) assuming linear normal stress distribution. If cracking takes place, water penetrates into the cracks, inducing the development of full uplift pressures (UPs). Sliding safety factors (SSFs) are computed using shear force resultants Vx, Vy, and a Mohr-Coulomb failure criterion while ignoring torsion T (VVT). This paper presents a 3D extension of the gravity method for cracked planar concrete sections of arbitrary geometry subjected to arbitrary loads (PMM-VVT). To compute the shear stress distribution, a VVT sectional analysis algorithm has been developed based on the theory of elasticity (TE), including Saint-Venant and warping torsional components combined with triangular 2D finite elements (FEs). Afterward, the SSF on the failure plane is computed from the integration of normal stresses on the remaining uncracked area where the Mohr-Coulomb criterion (considering the shear stresses from the VVT solution) has not been locally exceeded. Two validation examples and a case study of an actual pier are presented to illustrate the accuracy and efficiency of the proposed approach compared with full 3D FE analyses. ISSN : 0733-9445 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29ST.1943-541X.0000579