Dépouillements

Artificial ground freezing of fully saturated soil: / Roman Lackner 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.1–11. Titre : Artificial ground freezing of fully saturated soil: : Viscoelastic behavior Type de document : texte imprimé Auteurs : Roman Lackner, Auteur ; Christian Pichler, Auteur ; Andreas Kloiber, Auteur Année de publication : 2008 Article en page(s) : pp.1–11. Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Ice  Frozen  soils  Saturated  soils  Viscoplasticity  Micromechanics  Creep  Triaxial  tests Résumé : The transport and mechanical properties of saturated soil drastically change when temperatures drop below the freezing temperature of water. During artificial ground freezing, this change of properties is exploited in order to minimize deformations during construction work and for groundwater control. Whereas for the latter only the size of the frozen-soil body is relevant, which is obtained by solving the thermal problem, the design of the ground-freezing work for support purposes requires information about the mechanical behavior of frozen soil. In addition to the quantification of the improvement of mechanical properties during freezing, information about the dilation associated with the 9% volume increase of water during freezing is required in order to assess the risk of damage to surface infrastructure caused by frost heave. In this paper, a micromechanics-based model for the prediction of both the aforementioned phase-change dilation and the elastic and viscous properties of freezing saturated soil is presented. Hereby, the macroscopic material behavior is related to the behavior of the different constituents such as soil particles, water, and ice. Combined with the solution of the thermal problem, the proposed model provides the basis for predictions of the performance of support structures composed of frozen soil. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282008%29134%3A1%281% [...] [article] Artificial ground freezing of fully saturated soil: : Viscoelastic behavior [texte imprimé] / Roman Lackner, Auteur ; Christian Pichler, Auteur ; Andreas Kloiber, Auteur . - 2008 . - pp.1–11. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 134 N°1 (Janvier 2008) . - pp.1–11. Mots-clés : Ice  Frozen  soils  Saturated  soils  Viscoplasticity  Micromechanics  Creep  Triaxial  tests Résumé : The transport and mechanical properties of saturated soil drastically change when temperatures drop below the freezing temperature of water. During artificial ground freezing, this change of properties is exploited in order to minimize deformations during construction work and for groundwater control. Whereas for the latter only the size of the frozen-soil body is relevant, which is obtained by solving the thermal problem, the design of the ground-freezing work for support purposes requires information about the mechanical behavior of frozen soil. In addition to the quantification of the improvement of mechanical properties during freezing, information about the dilation associated with the 9% volume increase of water during freezing is required in order to assess the risk of damage to surface infrastructure caused by frost heave. In this paper, a micromechanics-based model for the prediction of both the aforementioned phase-change dilation and the elastic and viscous properties of freezing saturated soil is presented. Hereby, the macroscopic material behavior is related to the behavior of the different constituents such as soil particles, water, and ice. Combined with the solution of the thermal problem, the proposed model provides the basis for predictions of the performance of support structures composed of frozen soil. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282008%29134%3A1%281% [...]

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 [...]

Identification of the mechanical subsystem of the NEES-UCSD shake table by a least-squares approach / Ozcelik, O. 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.23–34. Titre : Identification of the mechanical subsystem of the NEES-UCSD shake table by a least-squares approach Type de document : texte imprimé Auteurs : Ozcelik, O., Auteur ; J. E. Luco, Auteur ; J. P. Conte, Auteur Année de publication : 2008 Article en page(s) : pp.23–34. Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Shake  table  tests  Least  squares  method  Earthquakes  Simulation. Résumé : A least-squares method is used to determine the fundamental parameters of a simple mathematical model for the mechanical subsystem of the NEES-UCSD large high performance outdoor shaking table. The parameters identified include the effective horizontal mass, the effective horizontal stiffness, and the coefficient of the classical Coulomb friction and viscous damping elements representing the various dissipative forces in the system. The values obtained for these parameters are validated by comparisons with previous results based on an alternative identification method applicable only to periodic tests and by comparisons with experimental data obtained during earthquake simulation tests and harmonic steady-state tests. The proposed identification approach works well for periodic sinusoidal and triangular tests, earthquake simulation tests, and white noise tests with table root mean square above 10% of gravity. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282008%29134%3A1%2823 [...] [article] Identification of the mechanical subsystem of the NEES-UCSD shake table by a least-squares approach [texte imprimé] / Ozcelik, O., Auteur ; J. E. Luco, Auteur ; J. P. Conte, Auteur . - 2008 . - pp.23–34. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 134 N°1 (Janvier 2008) . - pp.23–34. Mots-clés : Shake  table  tests  Least  squares  method  Earthquakes  Simulation. Résumé : A least-squares method is used to determine the fundamental parameters of a simple mathematical model for the mechanical subsystem of the NEES-UCSD large high performance outdoor shaking table. The parameters identified include the effective horizontal mass, the effective horizontal stiffness, and the coefficient of the classical Coulomb friction and viscous damping elements representing the various dissipative forces in the system. The values obtained for these parameters are validated by comparisons with previous results based on an alternative identification method applicable only to periodic tests and by comparisons with experimental data obtained during earthquake simulation tests and harmonic steady-state tests. The proposed identification approach works well for periodic sinusoidal and triangular tests, earthquake simulation tests, and white noise tests with table root mean square above 10% of gravity. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282008%29134%3A1%2823 [...]

Deterministic excitation forces for simulation and identification of nonlinear hysteretic SDOF systems / Jin-Song Pei 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.35–48. Titre : Deterministic excitation forces for simulation and identification of nonlinear hysteretic SDOF systems Type de document : texte imprimé Auteurs : Jin-Song Pei, Auteur ; Krisda Piyawat, Auteur Année de publication : 2008 Article en page(s) : pp.35–48. Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Excitation  Simulation  Hysteresis  Stiffness  Degradation Résumé : This paper investigates how to design deterministic excitation forces in studying nonlinear single-degree-of-freedom systems, especially those with rate and path dependency and strength and stiffness degradation. One frequency-modulated periodic excitation and its amplitude-modulated counterpart are proposed as a solution, and a series of numerical exercises are carried out to show that these forces can be designed for sufficient forcing functions to study the complex nonlinear hysteresis. To rapidly reveal the underlying characteristics of the system and also to further lead to an effective system identification, four evaluation tools are proposed to be utilized together with the proposed excitation forces. These tools include the response curves, force-state map, intercycle drift, and intercycle pattern change, based on which some distinctive “patterns” are obtained to reveal the existence of nonlinearities, types of nonlinearities, existence of memory, and degradation. By using both Bouc-Wen and Bouc-Wen-Baber-Noori models for the system in all the simulations, the writers compare the commonly used forces with the proposed excitation forces to further demonstrate the advantages of the proposed excitation forces and evaluation tools. The writers also explore challenges in terms of implementing the proposed excitation forces. The results of this study are expected to benefit both physical testing and numerical simulation of complex nonlinear hysteretic systems in a time- and cost-effective manner, as well as leading to efficient schemes for system identification. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282008%29134%3A1%2835 [...] [article] Deterministic excitation forces for simulation and identification of nonlinear hysteretic SDOF systems [texte imprimé] / Jin-Song Pei, Auteur ; Krisda Piyawat, Auteur . - 2008 . - pp.35–48. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 134 N°1 (Janvier 2008) . - pp.35–48. Mots-clés : Excitation  Simulation  Hysteresis  Stiffness  Degradation Résumé : This paper investigates how to design deterministic excitation forces in studying nonlinear single-degree-of-freedom systems, especially those with rate and path dependency and strength and stiffness degradation. One frequency-modulated periodic excitation and its amplitude-modulated counterpart are proposed as a solution, and a series of numerical exercises are carried out to show that these forces can be designed for sufficient forcing functions to study the complex nonlinear hysteresis. To rapidly reveal the underlying characteristics of the system and also to further lead to an effective system identification, four evaluation tools are proposed to be utilized together with the proposed excitation forces. These tools include the response curves, force-state map, intercycle drift, and intercycle pattern change, based on which some distinctive “patterns” are obtained to reveal the existence of nonlinearities, types of nonlinearities, existence of memory, and degradation. By using both Bouc-Wen and Bouc-Wen-Baber-Noori models for the system in all the simulations, the writers compare the commonly used forces with the proposed excitation forces to further demonstrate the advantages of the proposed excitation forces and evaluation tools. The writers also explore challenges in terms of implementing the proposed excitation forces. The results of this study are expected to benefit both physical testing and numerical simulation of complex nonlinear hysteretic systems in a time- and cost-effective manner, as well as leading to efficient schemes for system identification. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282008%29134%3A1%2835 [...]

Characteristics of turbulent flow in submerged jumps on rough beds / Subhasish Dey 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.49–59. Titre : Characteristics of turbulent flow in submerged jumps on rough beds Type de document : texte imprimé Auteurs : Subhasish Dey, Auteur ; Sarkar, Arindam, Auteur Année de publication : 2008 Article en page(s) : pp.49–59. Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Boundary  layers  Hydraulic  jumps  Open  channels  Steady  flow  Submerged  jets  Turbulent  flow  Channel  beds Résumé : The results of an experimental investigation on the flow field in submerged jumps on horizontal rough beds, detected by an acoustic Doppler velocimeter, are presented. Experiments were conducted for the conditions of submerged jumps, having submergence factors from 0.96 to 1.85 and jet Froude numbers from 2.58 to 4.87, over rough beds of Nikuradse’s equivalent sand roughness equaling 0.49, 0.8, 1.86, and 3mm . The vertical distributions of time-averaged velocity components, turbulence intensity components, and Reynolds stress at different streamwise distances from the sluice opening and the horizontal distribution of bed-shear stress are plotted. Vector plots of the flow field show that the rate of decay of jet velocity in a submerged jump increases with increase in bed roughness. The flow characteristics on rough beds, being different from those on smooth bed, are discussed from the point of view of similarity, growth of the length scale, and decay of the velocity and turbulence characteristics scales. The most important observation is that the flow in the fully developed zone is found to be self-preserving. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282008%29134%3A1%2849 [...] [article] Characteristics of turbulent flow in submerged jumps on rough beds [texte imprimé] / Subhasish Dey, Auteur ; Sarkar, Arindam, Auteur . - 2008 . - pp.49–59. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 134 N°1 (Janvier 2008) . - pp.49–59. Mots-clés : Boundary  layers  Hydraulic  jumps  Open  channels  Steady  flow  Submerged  jets  Turbulent  flow  Channel  beds Résumé : The results of an experimental investigation on the flow field in submerged jumps on horizontal rough beds, detected by an acoustic Doppler velocimeter, are presented. Experiments were conducted for the conditions of submerged jumps, having submergence factors from 0.96 to 1.85 and jet Froude numbers from 2.58 to 4.87, over rough beds of Nikuradse’s equivalent sand roughness equaling 0.49, 0.8, 1.86, and 3mm . The vertical distributions of time-averaged velocity components, turbulence intensity components, and Reynolds stress at different streamwise distances from the sluice opening and the horizontal distribution of bed-shear stress are plotted. Vector plots of the flow field show that the rate of decay of jet velocity in a submerged jump increases with increase in bed roughness. The flow characteristics on rough beds, being different from those on smooth bed, are discussed from the point of view of similarity, growth of the length scale, and decay of the velocity and turbulence characteristics scales. The most important observation is that the flow in the fully developed zone is found to be self-preserving. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282008%29134%3A1%2849 [...]

Flow around cylinders in open channels / M. A. Sadeque 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.60–71. Titre : Flow around cylinders in open channels Type de document : texte imprimé Auteurs : M. A. Sadeque, Auteur ; Rajaratnam, N., Auteur ; M. R. Loewen, Auteur Année de publication : 2008 Article en page(s) : pp.60–71. Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Open  channel  flow  Boundary  layers  Flow  visualization  Shear  stress  Fish  management  Cylinders Résumé : This paper presents the results of an experimental study of flow around cylindrical objects in an open channel. Cylindrical objects of equal diameter and four heights were tested under similar flow conditions producing four different levels of submergence, including a surface piercing bridge-pier-like cylinder. Different flow elements and their locations were identified using a set of flow visualization tests. Observations made from the flow visualization tests were then verified by measurements of bed-shear stress and deflected flow velocity around the cylinders. Horse-shoe vortex systems were found to appear closer to the submerged cylinders compared to a surface piercing cylinder. The increase in dimensionless bed-shear stress is found to be inversely related to the level of submergence of the cylinders. Bed-shear stress results presented in this paper will be valuable for a qualitative understanding of the scour potential of flow around submerged cylinders. Mean velocity profiles in the deflected flow region were analyzed in terms of the theories of three-dimensional turbulent boundary layer. Submergence of a cylinder has been found to suppress alternate vortex shedding and produce stronger three-dimensional flows in the downstream wake. Perry and Joubert’s model was found to be sufficiently accurate to predict the deflected velocity magnitudes around submerged cylinders. Overall, the present study will provide valuable knowledge of hydraulics of flow around submerged structures (e.g., simple fish habitat structures). ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282008%29134%3A1%2860 [...] [article] Flow around cylinders in open channels [texte imprimé] / M. A. Sadeque, Auteur ; Rajaratnam, N., Auteur ; M. R. Loewen, Auteur . - 2008 . - pp.60–71. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 134 N°1 (Janvier 2008) . - pp.60–71. Mots-clés : Open  channel  flow  Boundary  layers  Flow  visualization  Shear  stress  Fish  management  Cylinders Résumé : This paper presents the results of an experimental study of flow around cylindrical objects in an open channel. Cylindrical objects of equal diameter and four heights were tested under similar flow conditions producing four different levels of submergence, including a surface piercing bridge-pier-like cylinder. Different flow elements and their locations were identified using a set of flow visualization tests. Observations made from the flow visualization tests were then verified by measurements of bed-shear stress and deflected flow velocity around the cylinders. Horse-shoe vortex systems were found to appear closer to the submerged cylinders compared to a surface piercing cylinder. The increase in dimensionless bed-shear stress is found to be inversely related to the level of submergence of the cylinders. Bed-shear stress results presented in this paper will be valuable for a qualitative understanding of the scour potential of flow around submerged cylinders. Mean velocity profiles in the deflected flow region were analyzed in terms of the theories of three-dimensional turbulent boundary layer. Submergence of a cylinder has been found to suppress alternate vortex shedding and produce stronger three-dimensional flows in the downstream wake. Perry and Joubert’s model was found to be sufficiently accurate to predict the deflected velocity magnitudes around submerged cylinders. Overall, the present study will provide valuable knowledge of hydraulics of flow around submerged structures (e.g., simple fish habitat structures). ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282008%29134%3A1%2860 [...]

Three-dimensional damage model for concrete. I / Yu Liu 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) Titre : Three-dimensional damage model for concrete. I : Theory Type de document : texte imprimé Auteurs : Yu Liu, Auteur ; Susanto Teng, Auteur ; Chee-Kiong Soh, Auteur Année de publication : 2008 Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Concrete  Constitutive  models  Cracking  Damage  Three-dimensional  models Résumé : A damage model for concrete is proposed based on the existing displacement equivalence-based model for brittle materials. The model is established in a randomly selected coordinate system so as to consider the cases where the principal directions of damage do not coincide with those of stress and strain. The effect of shear stress is also considered. The slipping cracks of concrete under triaxial compression and the stiffness reduction under hydrostatic compression are also taken into account. The friction at crack tips has been introduced to account for the permanent deformation and a blend of elastic and secant unloading/reloading routine is obtained. The evolution rule of damage is combined with the predefined basic damage evolution patterns. ISSN : 0733-9399 En ligne : http://cedb.asce.org/cgi/WWWdisplay.cgi?161981 [article] Three-dimensional damage model for concrete. I : Theory [texte imprimé] / Yu Liu, Auteur ; Susanto Teng, Auteur ; Chee-Kiong Soh, Auteur . - 2008. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 134 N°1 (Janvier 2008) Mots-clés : Concrete  Constitutive  models  Cracking  Damage  Three-dimensional  models Résumé : A damage model for concrete is proposed based on the existing displacement equivalence-based model for brittle materials. The model is established in a randomly selected coordinate system so as to consider the cases where the principal directions of damage do not coincide with those of stress and strain. The effect of shear stress is also considered. The slipping cracks of concrete under triaxial compression and the stiffness reduction under hydrostatic compression are also taken into account. The friction at crack tips has been introduced to account for the permanent deformation and a blend of elastic and secant unloading/reloading routine is obtained. The evolution rule of damage is combined with the predefined basic damage evolution patterns. ISSN : 0733-9399 En ligne : http://cedb.asce.org/cgi/WWWdisplay.cgi?161981

Three-dimensional damage model for concrete. II / Yu Liu 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.82-89 Titre : Three-dimensional damage model for concrete. II : Verification Type de document : texte imprimé Auteurs : Yu Liu, Auteur ; Susanto Teng, Auteur ; Chee-Kiong Soh, Auteur Année de publication : 2008 Article en page(s) : pp.82-89 Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Concrete  Constitutive  models  Cracking  Three-dimensional  models  Damage Résumé : A three-dimensional damage model for concrete has been proposed in the preceding paper, Part I: Theory. This paper focuses on the application of the damage model for quasi-brittle materials such as concrete. The determination of model parameters for the evolution rule of damage is discussed. The model parameters to consider the frictional stress and the stiffness reduction under hydrostatic compression are also studied. For verification, the proposed model is applied to concrete subjected to confined compression, triaxial, loading, and cyclic loading. Consistent results, as compared with other researchers’ experimental data, were obtained, and the proposed model is considered worthy of further research work. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282008%29134%3A1%2882 [...] [article] Three-dimensional damage model for concrete. II : Verification [texte imprimé] / Yu Liu, Auteur ; Susanto Teng, Auteur ; Chee-Kiong Soh, Auteur . - 2008 . - pp.82-89. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 134 N°1 (Janvier 2008) . - pp.82-89 Mots-clés : Concrete  Constitutive  models  Cracking  Three-dimensional  models  Damage Résumé : A three-dimensional damage model for concrete has been proposed in the preceding paper, Part I: Theory. This paper focuses on the application of the damage model for quasi-brittle materials such as concrete. The determination of model parameters for the evolution rule of damage is discussed. The model parameters to consider the frictional stress and the stiffness reduction under hydrostatic compression are also studied. For verification, the proposed model is applied to concrete subjected to confined compression, triaxial, loading, and cyclic loading. Consistent results, as compared with other researchers’ experimental data, were obtained, and the proposed model is considered worthy of further research work. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282008%29134%3A1%2882 [...]

Multicrack detection on semirigidly connected beams utilizing dynamic data / Heung Fai Lam 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. 90–99. Titre : Multicrack detection on semirigidly connected beams utilizing dynamic data Type de document : texte imprimé Auteurs : Heung Fai Lam, Auteur ; Ching Tai Ng, Auteur ; Andrew Yee Leung, Auteur Année de publication : 2008 Article en page(s) : pp. 90–99. Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Connections  Beams  Data  analysis  Cracking Résumé : The problem of crack detection has been studied by many researchers, and many methods of approaching the problem have been developed. To quantify the crack extent, most methods follow the model updating approach. This approach treats the crack location and extent as model parameters, which are then identified by minimizing the discrepancy between the modeled and the measured dynamic responses. Most methods following this approach focus on the detection of a single crack or multicracks in situations in which the number of cracks is known. The main objective of this paper is to address the crack detection problem in a general situation in which the number of cracks is not known in advance. The crack detection methodology proposed in this paper consists of two phases. In the first phase, different classes of models are employed to model the beam with different numbers of cracks, and the Bayesian model class selection method is then employed to identify the most plausible class of models based on the set of measured dynamic data in order to identify the number of cracks on the beam. In the second phase, the posterior (updated) probability density function of the crack locations and the corresponding extents is calculated using the Bayesian statistical framework. As a result, the uncertainties that may have been introduced by measurement noise and modeling error can be explicitly dealt with. The methodology proposed herein has been verified by and demonstrated through a comprehensive series of numerical case studies, in which noisy data were generated by a Bernoulli–Euler beam with semirigid connections. The results of these studies show that the proposed methodology can correctly identify the number of cracks even when the crack extent is small. The effects of measurement noise, modeling error, and the complexity of the class of identification model on the crack detection results have also been studied and are discussed in this paper. ISSN : 0733-9399 En ligne : http://ascelibrary.org/action/showAbstract?page=90&volume=134&issue=1&journalCod [...] [article] Multicrack detection on semirigidly connected beams utilizing dynamic data [texte imprimé] / Heung Fai Lam, Auteur ; Ching Tai Ng, Auteur ; Andrew Yee Leung, Auteur . - 2008 . - pp. 90–99. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 134 N°1 (Janvier 2008) . - pp. 90–99. Mots-clés : Connections  Beams  Data  analysis  Cracking Résumé : The problem of crack detection has been studied by many researchers, and many methods of approaching the problem have been developed. To quantify the crack extent, most methods follow the model updating approach. This approach treats the crack location and extent as model parameters, which are then identified by minimizing the discrepancy between the modeled and the measured dynamic responses. Most methods following this approach focus on the detection of a single crack or multicracks in situations in which the number of cracks is known. The main objective of this paper is to address the crack detection problem in a general situation in which the number of cracks is not known in advance. The crack detection methodology proposed in this paper consists of two phases. In the first phase, different classes of models are employed to model the beam with different numbers of cracks, and the Bayesian model class selection method is then employed to identify the most plausible class of models based on the set of measured dynamic data in order to identify the number of cracks on the beam. In the second phase, the posterior (updated) probability density function of the crack locations and the corresponding extents is calculated using the Bayesian statistical framework. As a result, the uncertainties that may have been introduced by measurement noise and modeling error can be explicitly dealt with. The methodology proposed herein has been verified by and demonstrated through a comprehensive series of numerical case studies, in which noisy data were generated by a Bernoulli–Euler beam with semirigid connections. The results of these studies show that the proposed methodology can correctly identify the number of cracks even when the crack extent is small. The effects of measurement noise, modeling error, and the complexity of the class of identification model on the crack detection results have also been studied and are discussed in this paper. ISSN : 0733-9399 En ligne : http://ascelibrary.org/action/showAbstract?page=90&volume=134&issue=1&journalCod [...]

Crack-tip parameters in polycrystalline plates with soft grain boundaries / Yuping Wang 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.100–109. Titre : Crack-tip parameters in polycrystalline plates with soft grain boundaries Type de document : texte imprimé Auteurs : Yuping Wang, Auteur ; Roberto Ballarini, Auteur ; Gregory J. Rodin, Auteur Année de publication : 2008 Article en page(s) : pp.100–109. Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Cracking  Plates  Parameters  Grains  material  Finite  element  method Résumé : Two micromechanical models are used to calculate the statistical distributions of the stress intensity factor of a crack in a polycrystalline plate containing stiff grains and soft grain boundaries. The first is a finite-element method based Monte Carlo procedure where the microstructure is represented by a Poisson–Voronoi tessellation. The effective elastic moduli of the uncracked plate and the stress intensity factor of the cracked plate are calculated for selected values of the parameters that quantify the level of elastic mismatch between the grains and grain boundaries. It is shown that the stress intensity factor is independent of the expected number of grains, and that it can be estimated using an analytical model involving a long crack whose tip is contained within a circular inhomogeneity surrounded by an infinitely extended homogenized material. The stress intensity factor distributions of this auxiliary problem, obtained using the method of continuously distributed dislocations, are in excellent agreement with those corresponding to the polycrystalline microstructure, and are very sensitive to the position within the inhomogeneity of the crack tip. These results suggest that fracture toughness experiments on polycrystalline plates can be considered experiments on the single grain containing the crack tip, and in turn reflect the a/w effects typical of finite-geometry specimens. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282008%29134%3A1%2810 [...] [article] Crack-tip parameters in polycrystalline plates with soft grain boundaries [texte imprimé] / Yuping Wang, Auteur ; Roberto Ballarini, Auteur ; Gregory J. Rodin, Auteur . - 2008 . - pp.100–109. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 134 N°1 (Janvier 2008) . - pp.100–109. Mots-clés : Cracking  Plates  Parameters  Grains  material  Finite  element  method Résumé : Two micromechanical models are used to calculate the statistical distributions of the stress intensity factor of a crack in a polycrystalline plate containing stiff grains and soft grain boundaries. The first is a finite-element method based Monte Carlo procedure where the microstructure is represented by a Poisson–Voronoi tessellation. The effective elastic moduli of the uncracked plate and the stress intensity factor of the cracked plate are calculated for selected values of the parameters that quantify the level of elastic mismatch between the grains and grain boundaries. It is shown that the stress intensity factor is independent of the expected number of grains, and that it can be estimated using an analytical model involving a long crack whose tip is contained within a circular inhomogeneity surrounded by an infinitely extended homogenized material. The stress intensity factor distributions of this auxiliary problem, obtained using the method of continuously distributed dislocations, are in excellent agreement with those corresponding to the polycrystalline microstructure, and are very sensitive to the position within the inhomogeneity of the crack tip. These results suggest that fracture toughness experiments on polycrystalline plates can be considered experiments on the single grain containing the crack tip, and in turn reflect the a/w effects typical of finite-geometry specimens. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282008%29134%3A1%2810 [...]

Simple formulation for the flexure of plates on nonlinear foundation / S. Arul Jayachandran 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.110–115. Titre : Simple formulation for the flexure of plates on nonlinear foundation Type de document : texte imprimé Auteurs : S. Arul Jayachandran, Auteur ; S. Seetharaman, Auteur ; Susan Abraham, Auteur Année de publication : 2008 Article en page(s) : pp.110–115. Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Foundation  Finite  element  analysis  Plates  Elasticity Résumé : Plates resting on an elastic medium are normally analyzed in a simplified way using the linear Winkler foundation approach. Nevertheless, plates resting on layered medium with vast differences in their moduli exhibit nonlinear behavior under pressure. The present technical note deals with a nonlinear finite-element procedure to analyze plates with linear strain displacement relations resting on a nonlinear elastic media. The coupled problem is formulated using the total potential energy (TPE) concept. The nonlinear foundation stiffness matrices have been derived using the Taylor expansion of the TPE at equilibrium and a symbolism of grouping the energy contributions. The nonlinear foundation stiffness matrices derived in the present technical note have been demonstrated to yield results that agree well with published results in the literature. A brief parametric study on the effects of nonlinearity of the foundation is also presented using the proposed foundation stiffness matrices. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282008%29134%3A1%2811 [...] [article] Simple formulation for the flexure of plates on nonlinear foundation [texte imprimé] / S. Arul Jayachandran, Auteur ; S. Seetharaman, Auteur ; Susan Abraham, Auteur . - 2008 . - pp.110–115. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 134 N°1 (Janvier 2008) . - pp.110–115. Mots-clés : Foundation  Finite  element  analysis  Plates  Elasticity Résumé : Plates resting on an elastic medium are normally analyzed in a simplified way using the linear Winkler foundation approach. Nevertheless, plates resting on layered medium with vast differences in their moduli exhibit nonlinear behavior under pressure. The present technical note deals with a nonlinear finite-element procedure to analyze plates with linear strain displacement relations resting on a nonlinear elastic media. The coupled problem is formulated using the total potential energy (TPE) concept. The nonlinear foundation stiffness matrices have been derived using the Taylor expansion of the TPE at equilibrium and a symbolism of grouping the energy contributions. The nonlinear foundation stiffness matrices derived in the present technical note have been demonstrated to yield results that agree well with published results in the literature. A brief parametric study on the effects of nonlinearity of the foundation is also presented using the proposed foundation stiffness matrices. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282008%29134%3A1%2811 [...]

Exact solution for buckling of columns including self-weight / W. H. Duan 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.116–119. Titre : Exact solution for buckling of columns including self-weight Type de document : texte imprimé Auteurs : W. H. Duan, Auteur ; C. M. Wang, Auteur Année de publication : 2008 Article en page(s) : pp.116–119. Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Columns  Buckling  Numerical  models  Axial  loads  Weight Résumé : In this technical note, analytical solutions for the elastic buckling of heavy columns with various combinations of end conditions are derived, for the first time, in terms of generalized hypergeometric functions. The benchmark solutions may be used to assess the accuracy of approximate formulas and numerical solutions. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282008%29134%3A1%2811 [...] [article] Exact solution for buckling of columns including self-weight [texte imprimé] / W. H. Duan, Auteur ; C. M. Wang, Auteur . - 2008 . - pp.116–119. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 134 N°1 (Janvier 2008) . - pp.116–119. Mots-clés : Columns  Buckling  Numerical  models  Axial  loads  Weight Résumé : In this technical note, analytical solutions for the elastic buckling of heavy columns with various combinations of end conditions are derived, for the first time, in terms of generalized hypergeometric functions. The benchmark solutions may be used to assess the accuracy of approximate formulas and numerical solutions. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282008%29134%3A1%2811 [...]

Mathematical Prediction of Cylinder Wake during Synchronization / M. K. Kwan 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.120–123. Titre : Mathematical Prediction of Cylinder Wake during Synchronization Type de document : texte imprimé Auteurs : M. K. Kwan, Auteur ; R. R. Hwang, Auteur Année de publication : 2008 Article en page(s) : pp.120–123. Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Oscillatory  flow  Flow  control  Hysteresis  Mathematics  Predictions. Résumé : For flows past a cylinder with a transversely oscillatory external forcing, a rapid phase change of π during synchronization has been noted in experimental studies in both laminar and turbulent regimes. In the present analysis, the Stuart–Landau (SL) model that was validated in unforced vortex shedding proves to be a feasible way in predicting this phase change. In addition, using this model other phenomena observed in experimental studies are also noted. These include the possible occurrence of hysteresis, and the broadening of frequency range undergoing phase change with the increase of forcing amplitu ISSN : 0733-9399 En ligne : ascelibrary.org/doi/abs/10.1061/(ASCE)0733-9399(2008)134%3A1(116) [article] Mathematical Prediction of Cylinder Wake during Synchronization [texte imprimé] / M. K. Kwan, Auteur ; R. R. Hwang, Auteur . - 2008 . - pp.120–123. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 134 N°1 (Janvier 2008) . - pp.120–123. Mots-clés : Oscillatory  flow  Flow  control  Hysteresis  Mathematics  Predictions. Résumé : For flows past a cylinder with a transversely oscillatory external forcing, a rapid phase change of π during synchronization has been noted in experimental studies in both laminar and turbulent regimes. In the present analysis, the Stuart–Landau (SL) model that was validated in unforced vortex shedding proves to be a feasible way in predicting this phase change. In addition, using this model other phenomena observed in experimental studies are also noted. These include the possible occurrence of hysteresis, and the broadening of frequency range undergoing phase change with the increase of forcing amplitu ISSN : 0733-9399 En ligne : ascelibrary.org/doi/abs/10.1061/(ASCE)0733-9399(2008)134%3A1(116)

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