Dépouillements

Nearest neighbor probabilistic model for aluminum polycrystals / Mircea Grigoriu in Journal of engineering mechanics, Vol. 136 N° 7 (Juillet 2010) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 136 N° 7 (Juillet 2010) . - pp. 821-829 Titre : Nearest neighbor probabilistic model for aluminum polycrystals Type de document : texte imprimé Auteurs : Mircea Grigoriu, Auteur Article en page(s) : pp. 821-829 Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Monte  Carlo  method  Lattices  Probability  Aluminum  Measurement. Résumé : A real-valued random field {Zi,j} with piecewise constant samples and defined on a lattice L in [openface R]2 is developed to characterize two-dimensional metallic polycrystals. The subsets defined by constant values of {Zi,j} are virtual grains and the values of {Zi,j} give Euler angles at the nodes of L. The field {Zi,j} is completely defined by its marginal distribution and conditional probabilities associated with the nearest neighbor model. The defining probabilities of {Zi,j} need to be estimated from measurements of atomic lattice orientation. Random fields {Zi,j} calibrated to the measurements of crystallographic texture in two AA7075 aluminum plates have been used to generate virtual polycrystals. Virtual and actual polycrystals are similar. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JENMDT000 [...] [article] Nearest neighbor probabilistic model for aluminum polycrystals [texte imprimé] / Mircea Grigoriu, Auteur . - pp. 821-829. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 136 N° 7 (Juillet 2010) . - pp. 821-829 Mots-clés : Monte  Carlo  method  Lattices  Probability  Aluminum  Measurement. Résumé : A real-valued random field {Zi,j} with piecewise constant samples and defined on a lattice L in [openface R]2 is developed to characterize two-dimensional metallic polycrystals. The subsets defined by constant values of {Zi,j} are virtual grains and the values of {Zi,j} give Euler angles at the nodes of L. The field {Zi,j} is completely defined by its marginal distribution and conditional probabilities associated with the nearest neighbor model. The defining probabilities of {Zi,j} need to be estimated from measurements of atomic lattice orientation. Random fields {Zi,j} calibrated to the measurements of crystallographic texture in two AA7075 aluminum plates have been used to generate virtual polycrystals. Virtual and actual polycrystals are similar. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JENMDT000 [...]

Micromechanical modeling for inherent anisotropy in granular materials / Chang, Ching S. in Journal of engineering mechanics, Vol. 136 N° 7 (Juillet 2010) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 136 N° 7 (Juillet 2010) . - pp. 830-839 Titre : Micromechanical modeling for inherent anisotropy in granular materials Type de document : texte imprimé Auteurs : Chang, Ching S., Auteur ; Zhen-Yu Yin, Auteur Année de publication : 2010 Article en page(s) : pp. 830-839 Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Granular  material  Anisotropy  Triaxial  test  Micromechanics  Stress-strain  relations  Sand  Material. Résumé : In this paper, a description of inherent anisotropy of soil, based on micromechanics framework, is presented. The problem is formulated by assuming that sliding of two contact particles governed by Coulomb criterion in which the friction angle is a function of the orientation of the interparticle contact. The orientation distribution of these parameters is described by a set of symmetric second-order tensors. The formulation of the problem is illustrated by simulations of Santa Monica Beach Sand under true triaxial tests. In particular, the directional dependence of the strength characteristics is examined for samples with inherent cross anisotropy. The orientations of failure planes between particles are also examined. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JENMDT000 [...] [article] Micromechanical modeling for inherent anisotropy in granular materials [texte imprimé] / Chang, Ching S., Auteur ; Zhen-Yu Yin, Auteur . - 2010 . - pp. 830-839. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 136 N° 7 (Juillet 2010) . - pp. 830-839 Mots-clés : Granular  material  Anisotropy  Triaxial  test  Micromechanics  Stress-strain  relations  Sand  Material. Résumé : In this paper, a description of inherent anisotropy of soil, based on micromechanics framework, is presented. The problem is formulated by assuming that sliding of two contact particles governed by Coulomb criterion in which the friction angle is a function of the orientation of the interparticle contact. The orientation distribution of these parameters is described by a set of symmetric second-order tensors. The formulation of the problem is illustrated by simulations of Santa Monica Beach Sand under true triaxial tests. In particular, the directional dependence of the strength characteristics is examined for samples with inherent cross anisotropy. The orientations of failure planes between particles are also examined. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JENMDT000 [...]

Three-dimensional structural translation and rotation measurement using monocular videogrammetry / C. C. Chang in Journal of engineering mechanics, Vol. 136 N° 7 (Juillet 2010) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 136 N° 7 (Juillet 2010) . - pp. 840-848 Titre : Three-dimensional structural translation and rotation measurement using monocular videogrammetry Type de document : texte imprimé Auteurs : C. C. Chang, Auteur ; X. H. Xiao, Auteur Article en page(s) : pp. 840-848 Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Photogrammetry  Measurement  Three-dimensional  analysis  Displacement  Rotation. Résumé : Measuring displacement for large-scale structures has always been an important yet challenging task. In most applications, it is not feasible to provide a stationary platform at the location where its displacements need to be measured. Recently, image-based technique for three-dimensional (3D) displacement measurement has been developed and proven to be applicable to civil engineering structures. Most of these developments, however, use two or more cameras and require sophisticated calibration using a total station. In this paper, we present a single-camera approach that can simultaneously measure both 3D translation and rotation of a planar target attached on a structure. The intrinsic parameters of the camera are first obtained using a planar calibration board arbitrarily positioned around the target location. The obtained intrinsic parameters establish the relationship between the 3D camera coordinates and the two-dimensional image coordinates. These parameters can then be used to extract the rotation and translation of the planar target using recorded image sequence. The proposed technique is illustrated using two laboratory tests and one field test. Results show that the proposed monocular videogrammetric technique is a simple and effective alternative method to measure 3D translation and rotation for civil engineering structures. It should be noted that the proposed technique cannot measure translation along the direction perpendicular to the image plane. Hence, proper caution should be taken when placing target and camera. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JENMDT000 [...] [article] Three-dimensional structural translation and rotation measurement using monocular videogrammetry [texte imprimé] / C. C. Chang, Auteur ; X. H. Xiao, Auteur . - pp. 840-848. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 136 N° 7 (Juillet 2010) . - pp. 840-848 Mots-clés : Photogrammetry  Measurement  Three-dimensional  analysis  Displacement  Rotation. Résumé : Measuring displacement for large-scale structures has always been an important yet challenging task. In most applications, it is not feasible to provide a stationary platform at the location where its displacements need to be measured. Recently, image-based technique for three-dimensional (3D) displacement measurement has been developed and proven to be applicable to civil engineering structures. Most of these developments, however, use two or more cameras and require sophisticated calibration using a total station. In this paper, we present a single-camera approach that can simultaneously measure both 3D translation and rotation of a planar target attached on a structure. The intrinsic parameters of the camera are first obtained using a planar calibration board arbitrarily positioned around the target location. The obtained intrinsic parameters establish the relationship between the 3D camera coordinates and the two-dimensional image coordinates. These parameters can then be used to extract the rotation and translation of the planar target using recorded image sequence. The proposed technique is illustrated using two laboratory tests and one field test. Results show that the proposed monocular videogrammetric technique is a simple and effective alternative method to measure 3D translation and rotation for civil engineering structures. It should be noted that the proposed technique cannot measure translation along the direction perpendicular to the image plane. Hence, proper caution should be taken when placing target and camera. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JENMDT000 [...]

Parameter identification procedure for heterogeneous viscoelastic composites using iterative functions / Lev Khazanovich in Journal of engineering mechanics, Vol. 136 N° 7 (Juillet 2010) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 136 N° 7 (Juillet 2010) . - pp. 849-857 Titre : Parameter identification procedure for heterogeneous viscoelastic composites using iterative functions Type de document : texte imprimé Auteurs : Lev Khazanovich, Auteur ; Adam Zofka, Auteur ; Mihai Marasteanu, Auteur Article en page(s) : pp. 849-857 Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Elasticity  Viscoelasticity  Numerical  analysis  Asphalts  Mixtures  Composite  materials  Pavements. Résumé : This paper presents a new numerical procedure for the determination of the viscoelastic compliance properties of a matrix phase from a simple three-point bending test on a composite beam. The composite is modeled as elastic inclusions randomly dispersed throughout a viscoelastic matrix. It is also assumed that the spatial distribution of the inclusions in the composite is known or can be determined. Zevin's method of iterative functions is proposed for the determination of the matrix properties. Following a detailed explanation of the proposed scheme, a numerical verification is performed using three-dimensional finite-element (FE) analysis simulations. The proposed scheme was applied to the experimentally obtained creep compliance of the asphalt concrete beam. The obtained viscoelastic properties of the asphalt binder matrix phase were used as input into the FE model to simulate the behavior of the composite beam. An excellent comparison between the experimental data and the predicted beam deflections was observed. This shows that the proposed method is robust and it can be implemented to solve identification problems for viscoelastic composite materials. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JENMDT000 [...] [article] Parameter identification procedure for heterogeneous viscoelastic composites using iterative functions [texte imprimé] / Lev Khazanovich, Auteur ; Adam Zofka, Auteur ; Mihai Marasteanu, Auteur . - pp. 849-857. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 136 N° 7 (Juillet 2010) . - pp. 849-857 Mots-clés : Elasticity  Viscoelasticity  Numerical  analysis  Asphalts  Mixtures  Composite  materials  Pavements. Résumé : This paper presents a new numerical procedure for the determination of the viscoelastic compliance properties of a matrix phase from a simple three-point bending test on a composite beam. The composite is modeled as elastic inclusions randomly dispersed throughout a viscoelastic matrix. It is also assumed that the spatial distribution of the inclusions in the composite is known or can be determined. Zevin's method of iterative functions is proposed for the determination of the matrix properties. Following a detailed explanation of the proposed scheme, a numerical verification is performed using three-dimensional finite-element (FE) analysis simulations. The proposed scheme was applied to the experimentally obtained creep compliance of the asphalt concrete beam. The obtained viscoelastic properties of the asphalt binder matrix phase were used as input into the FE model to simulate the behavior of the composite beam. An excellent comparison between the experimental data and the predicted beam deflections was observed. This shows that the proposed method is robust and it can be implemented to solve identification problems for viscoelastic composite materials. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JENMDT000 [...]

Dynamic response of retrofitted masonry walls for blast loading / Girum S. Urgessa in Journal of engineering mechanics, Vol. 136 N° 7 (Juillet 2010) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 136 N° 7 (Juillet 2010) . - pp. 858-864 Titre : Dynamic response of retrofitted masonry walls for blast loading Type de document : texte imprimé Auteurs : Girum S. Urgessa, Auteur ; Arup K. Maji, Auteur Article en page(s) : pp. 858-864 Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Blast  loads  Concrete  Masonry  Finite  element  method  Fiber  reinforced  polymers  Full-Scale  tests  Walls. Résumé : A full-scale blast test was conducted on eight masonry walls reinforced with two and four layers of carbon fibers and two types of polymer matrices. The walls were then subjected to a 0.45-kg pentolite booster suspended from the ceiling of a test structure. The pressure-time history caused by the blast and the resulting displacement response were measured during the test. This paper presents a summary of the test program and the corresponding results from a nonlinear single degree of freedom analysis. The results provide a basis for determining effective means of retrofitting existing masonry walls and designing new structures to withstand blast loads. The paper also outlines a fiber-reinforced polymer retrofit design procedure for walls subjected to blast loading. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JENMDT000 [...] [article] Dynamic response of retrofitted masonry walls for blast loading [texte imprimé] / Girum S. Urgessa, Auteur ; Arup K. Maji, Auteur . - pp. 858-864. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 136 N° 7 (Juillet 2010) . - pp. 858-864 Mots-clés : Blast  loads  Concrete  Masonry  Finite  element  method  Fiber  reinforced  polymers  Full-Scale  tests  Walls. Résumé : A full-scale blast test was conducted on eight masonry walls reinforced with two and four layers of carbon fibers and two types of polymer matrices. The walls were then subjected to a 0.45-kg pentolite booster suspended from the ceiling of a test structure. The pressure-time history caused by the blast and the resulting displacement response were measured during the test. This paper presents a summary of the test program and the corresponding results from a nonlinear single degree of freedom analysis. The results provide a basis for determining effective means of retrofitting existing masonry walls and designing new structures to withstand blast loads. The paper also outlines a fiber-reinforced polymer retrofit design procedure for walls subjected to blast loading. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JENMDT000 [...]

Experimental study of particle motion on a smooth bed under shoaling waves using particle image velocimetry / Sanjay N. Havaldar in Journal of engineering mechanics, Vol. 136 N° 7 (Juillet 2010) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 136 N° 7 (Juillet 2010) . - pp. 865-876 Titre : Experimental study of particle motion on a smooth bed under shoaling waves using particle image velocimetry Type de document : texte imprimé Auteurs : Sanjay N. Havaldar, Auteur ; Francis C. K. Ting, Auteur Article en page(s) : pp. 865-876 Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Particles  Bed  loads  Two-phase  flow  Shoaling  waves  Drag  Friction  Experimentation. Résumé : The motion of spherical particles (diameter 1.58 mm, specific gravity 2.5) on 2 and 3% plane slope was studied in a laboratory wave flume for shoaling wave conditions. The range of wave-height-to-water-depth ratio was 0.24 DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JENMDT000 [...] [article] Experimental study of particle motion on a smooth bed under shoaling waves using particle image velocimetry [texte imprimé] / Sanjay N. Havaldar, Auteur ; Francis C. K. Ting, Auteur . - pp. 865-876. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 136 N° 7 (Juillet 2010) . - pp. 865-876 Mots-clés : Particles  Bed  loads  Two-phase  flow  Shoaling  waves  Drag  Friction  Experimentation. Résumé : The motion of spherical particles (diameter 1.58 mm, specific gravity 2.5) on 2 and 3% plane slope was studied in a laboratory wave flume for shoaling wave conditions. The range of wave-height-to-water-depth ratio was 0.24 DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JENMDT000 [...]

Turbulence characteristics in flows subjected to boundary injection and suction / Subhasish Dey in Journal of engineering mechanics, Vol. 136 N° 7 (Juillet 2010) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 136 N° 7 (Juillet 2010) . - pp. 877-888 Titre : Turbulence characteristics in flows subjected to boundary injection and suction Type de document : texte imprimé Auteurs : Subhasish Dey, Auteur ; Tushar K. Nath, Auteur Article en page(s) : pp. 877-888 Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Hydraulics  Open  channel  flow  Turbulent  flow  Steady  flow  River  beds  Seepage  Turbulence. Résumé : The influence of seepage (lateral flow) on the turbulence characteristics in free-surface flows over an immobile rough boundary is investigated. Steady flows having zero-pressure gradient over an immobile rough boundary created by uniform gravels of 4.1 mm in size were simulated experimentally with injection (upward seepage) and suction (downward seepage) applied through the boundary. A Vectrino (acoustic Doppler velocimeter) was used to measure the instantaneous velocities, which are analyzed to explore second- and third-order correlations, turbulent kinetic energy, turbulent energy budget, and conditional Reynolds shear stresses. It is observed that the second-order correlations decrease in presence of injection and increase in suction. The turbulent diffusivity and mixing length increase in presence of injection and decrease in suction. The third-order correlations suggest that the ejections are prevalent over the entire flow depth. The near-boundary flow is significantly influenced by the existence of upward seepage, which is manifested by a reduction in streamwise flux and the vertical advection of streamwise Reynolds normal stress. In addition, the upward flux and the streamwise advection of vertical Reynolds normal stress are also affected. The streamwise flux of turbulent kinetic is found to migrate upstream, while the vertical flux of turbulent kinetic energy is transported upward. The fluxes increase in presence of injection and decrease in suction. Energy budget evidences a lag between the turbulent dissipation and production and an opposing trend in the turbulent and pressure energy diffusions. A quadrant analysis for the conditional Reynolds shear stresses reveals that the ejection and sweep events are the primary contributions toward the total Reynolds shear stress production, with ejections dominating over the entire flow depth. The effect of seepage is shown to affect the magnitude of such events. However, in case of sweeps, this phenomenon is the opposite. The mean-time of occurrence of ejections and that of sweeps in suction are more persistent than those in no-seepage and injection. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JENMDT000 [...] [article] Turbulence characteristics in flows subjected to boundary injection and suction [texte imprimé] / Subhasish Dey, Auteur ; Tushar K. Nath, Auteur . - pp. 877-888. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 136 N° 7 (Juillet 2010) . - pp. 877-888 Mots-clés : Hydraulics  Open  channel  flow  Turbulent  flow  Steady  flow  River  beds  Seepage  Turbulence. Résumé : The influence of seepage (lateral flow) on the turbulence characteristics in free-surface flows over an immobile rough boundary is investigated. Steady flows having zero-pressure gradient over an immobile rough boundary created by uniform gravels of 4.1 mm in size were simulated experimentally with injection (upward seepage) and suction (downward seepage) applied through the boundary. A Vectrino (acoustic Doppler velocimeter) was used to measure the instantaneous velocities, which are analyzed to explore second- and third-order correlations, turbulent kinetic energy, turbulent energy budget, and conditional Reynolds shear stresses. It is observed that the second-order correlations decrease in presence of injection and increase in suction. The turbulent diffusivity and mixing length increase in presence of injection and decrease in suction. The third-order correlations suggest that the ejections are prevalent over the entire flow depth. The near-boundary flow is significantly influenced by the existence of upward seepage, which is manifested by a reduction in streamwise flux and the vertical advection of streamwise Reynolds normal stress. In addition, the upward flux and the streamwise advection of vertical Reynolds normal stress are also affected. The streamwise flux of turbulent kinetic is found to migrate upstream, while the vertical flux of turbulent kinetic energy is transported upward. The fluxes increase in presence of injection and decrease in suction. Energy budget evidences a lag between the turbulent dissipation and production and an opposing trend in the turbulent and pressure energy diffusions. A quadrant analysis for the conditional Reynolds shear stresses reveals that the ejection and sweep events are the primary contributions toward the total Reynolds shear stress production, with ejections dominating over the entire flow depth. The effect of seepage is shown to affect the magnitude of such events. However, in case of sweeps, this phenomenon is the opposite. The mean-time of occurrence of ejections and that of sweeps in suction are more persistent than those in no-seepage and injection. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JENMDT000 [...]

Modified cross-correlation method for the blind identification of structures / B. Hazra in Journal of engineering mechanics, Vol. 136 N° 7 (Juillet 2010) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 136 N° 7 (Juillet 2010) . - pp. 889-897 Titre : Modified cross-correlation method for the blind identification of structures Type de document : texte imprimé Auteurs : B. Hazra, Auteur ; A. J. Roffel, Auteur ; S. Narasimhan, Auteur Article en page(s) : pp. 889-897 Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Vibration  Monitoring  Identification  Correlation  Signal  processing. Résumé : Recently, blind source separation (BSS) methods have gained significant attention in the area of signal processing. Independent component analysis (ICA) and second-order blind identification (SOBI) are two popular BSS methods that have been applied to modal identification of mechanical and structural systems. Published results by several researchers have shown that ICA performs satisfactorily for systems with very low levels of structural damping, for example, for damping ratios of the order of 1% critical. For practical structural applications with higher levels of damping, methods based on SOBI have shown significant improvement over ICA methods. However, traditional SOBI methods suffer when nonstationary sources are present, such as those that occur during earthquakes and other transient excitations. In this paper, a new technique based on SOBI, called the modified cross-correlation method, is proposed to address these shortcomings. The conditions in which the problem of structural system identification can be posed as a BSS problem is also discussed. The results of simulation described in terms of identified natural frequencies, mode shapes, and damping ratios are presented for the cases of synthetic wind and recorded earthquake excitations. The results of identification show that the proposed method achieves better performance over traditional ICA and SOBI methods. Both experimental and large-scale structural simulation results are included to demonstrate the applicability of the newly proposed method to structural identification problems. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JENMDT000 [...] [article] Modified cross-correlation method for the blind identification of structures [texte imprimé] / B. Hazra, Auteur ; A. J. Roffel, Auteur ; S. Narasimhan, Auteur . - pp. 889-897. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 136 N° 7 (Juillet 2010) . - pp. 889-897 Mots-clés : Vibration  Monitoring  Identification  Correlation  Signal  processing. Résumé : Recently, blind source separation (BSS) methods have gained significant attention in the area of signal processing. Independent component analysis (ICA) and second-order blind identification (SOBI) are two popular BSS methods that have been applied to modal identification of mechanical and structural systems. Published results by several researchers have shown that ICA performs satisfactorily for systems with very low levels of structural damping, for example, for damping ratios of the order of 1% critical. For practical structural applications with higher levels of damping, methods based on SOBI have shown significant improvement over ICA methods. However, traditional SOBI methods suffer when nonstationary sources are present, such as those that occur during earthquakes and other transient excitations. In this paper, a new technique based on SOBI, called the modified cross-correlation method, is proposed to address these shortcomings. The conditions in which the problem of structural system identification can be posed as a BSS problem is also discussed. The results of simulation described in terms of identified natural frequencies, mode shapes, and damping ratios are presented for the cases of synthetic wind and recorded earthquake excitations. The results of identification show that the proposed method achieves better performance over traditional ICA and SOBI methods. Both experimental and large-scale structural simulation results are included to demonstrate the applicability of the newly proposed method to structural identification problems. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JENMDT000 [...]

Influence of rocking motion on vibratory roller-based measurement of soil stiffness / Norman W. Facas in Journal of engineering mechanics, Vol. 136 N° 7 (Juillet 2010) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 136 N° 7 (Juillet 2010) . - pp. 898-905 Titre : Influence of rocking motion on vibratory roller-based measurement of soil stiffness Type de document : texte imprimé Auteurs : Norman W. Facas, Auteur ; Paul J. van Susante, Auteur ; Michael A. Mooney, Auteur Article en page(s) : pp. 898-905 Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Vibration  Soil  compaction  Parameters  Models  Stiffness  Measurement  Kinematics. Résumé : Experimental data have shown that vibratory roller compactors often exhibit rotational kinematics in addition to translation during operation. This rotation is not considered in roller-integrated measurement systems that estimate soil stiffness based on drum vibration. To model and explore the effect of rotation, a lumped parameter roller/soil model was developed. The machine parameters for this model were tuned from suspended drum testing that isolated the drum from the ground. The model was then verified using field data collected over a range of excitation frequencies on spatially homogenous soil, and over transversely heterogeneous soil using one excitation frequency. Rotational motion was found to significantly influence roller-integrated measurement of soil stiffness based on single position drum vibration data. Rotational motion causes single position measurement system results to be nonunique and to vary depending on the direction of roller travel. Using the model, various alternative measurement schemes were investigated. The directional dependence was eliminated by deriving a measurement at the drum's center of gravity, and dual-sided measurement is proposed to gain a measure of heterogeneity. A more theoretical approach was also created wherein the contact force between the drum and soil are measured rather then being calculated. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JENMDT000 [...] [article] Influence of rocking motion on vibratory roller-based measurement of soil stiffness [texte imprimé] / Norman W. Facas, Auteur ; Paul J. van Susante, Auteur ; Michael A. Mooney, Auteur . - pp. 898-905. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 136 N° 7 (Juillet 2010) . - pp. 898-905 Mots-clés : Vibration  Soil  compaction  Parameters  Models  Stiffness  Measurement  Kinematics. Résumé : Experimental data have shown that vibratory roller compactors often exhibit rotational kinematics in addition to translation during operation. This rotation is not considered in roller-integrated measurement systems that estimate soil stiffness based on drum vibration. To model and explore the effect of rotation, a lumped parameter roller/soil model was developed. The machine parameters for this model were tuned from suspended drum testing that isolated the drum from the ground. The model was then verified using field data collected over a range of excitation frequencies on spatially homogenous soil, and over transversely heterogeneous soil using one excitation frequency. Rotational motion was found to significantly influence roller-integrated measurement of soil stiffness based on single position drum vibration data. Rotational motion causes single position measurement system results to be nonunique and to vary depending on the direction of roller travel. Using the model, various alternative measurement schemes were investigated. The directional dependence was eliminated by deriving a measurement at the drum's center of gravity, and dual-sided measurement is proposed to gain a measure of heterogeneity. A more theoretical approach was also created wherein the contact force between the drum and soil are measured rather then being calculated. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JENMDT000 [...]

Assessment of construction joint effect in full-scale concrete beams by acoustic emission activity / Dimitrios G. Aggelis in Journal of engineering mechanics, Vol. 136 N° 7 (Juillet 2010) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 136 N° 7 (Juillet 2010) . - pp. 906-912 Titre : Assessment of construction joint effect in full-scale concrete beams by acoustic emission activity Type de document : texte imprimé Auteurs : Dimitrios G. Aggelis, Auteur ; Tomoki Shiotani, Auteur ; Masato Terazawa, Auteur Article en page(s) : pp. 906-912 Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Acoustic  methods  Concrete  beams  cracking  Load  bearing  capacity  Reinforcement. Résumé : In the present paper the mechanical and acoustic emission (AE) behaviors of full-scale reinforced concrete beams are evaluated. One of the beams was constructed in two parts, which were assembled later in order to evaluate the effect of the joints in the structural behavior. The load was applied by means of a four-point-bending configuration. It is revealed that at initial stages of loading, the conventional measurements of strain and deflection, as well as pulse velocity, do not show any discrepancy, although the structural performance of the two beams is eventually proven to be quite different. On the contrary, AE parameters, even from early load steps, indicate that the damage accumulation is much faster in the assembled beam. This is confirmed by the calculated sources of AE events which are close to the construction joints. The results show that the AE technique is suitable to monitor the deterioration process of full-scale structures and yields valuable information that cannot be obtained at the early stages of damage by any other way. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JENMDT000 [...] [article] Assessment of construction joint effect in full-scale concrete beams by acoustic emission activity [texte imprimé] / Dimitrios G. Aggelis, Auteur ; Tomoki Shiotani, Auteur ; Masato Terazawa, Auteur . - pp. 906-912. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 136 N° 7 (Juillet 2010) . - pp. 906-912 Mots-clés : Acoustic  methods  Concrete  beams  cracking  Load  bearing  capacity  Reinforcement. Résumé : In the present paper the mechanical and acoustic emission (AE) behaviors of full-scale reinforced concrete beams are evaluated. One of the beams was constructed in two parts, which were assembled later in order to evaluate the effect of the joints in the structural behavior. The load was applied by means of a four-point-bending configuration. It is revealed that at initial stages of loading, the conventional measurements of strain and deflection, as well as pulse velocity, do not show any discrepancy, although the structural performance of the two beams is eventually proven to be quite different. On the contrary, AE parameters, even from early load steps, indicate that the damage accumulation is much faster in the assembled beam. This is confirmed by the calculated sources of AE events which are close to the construction joints. The results show that the AE technique is suitable to monitor the deterioration process of full-scale structures and yields valuable information that cannot be obtained at the early stages of damage by any other way. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JENMDT000 [...]

Forced vertical vibration of rigid circular disc on a transversely isotropic half-space / Eskandari-Ghadi, Morteza in Journal of engineering mechanics, Vol. 136 N° 7 (Juillet 2010) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 136 N° 7 (Juillet 2010) . - pp. 913-922 Titre : Forced vertical vibration of rigid circular disc on a transversely isotropic half-space Type de document : texte imprimé Auteurs : Eskandari-Ghadi, Morteza, Auteur ; Morteza Fallahi, Auteur ; Azizollah Ardeshir-Behrestaghi, Auteur Article en page(s) : pp. 913-922 Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Isotropy  Half  space  Wave  propagation  Integral  equations  Soil-structure-interactions  Vibration. Résumé : Vertical vibration of a rigid circular disc attached to the surface of a transversely isotropic half-space is considered in such a way that the axis of material symmetry is normal to the surface of the half-space and parallel to the vibration direction. By using Hankel integral transforms, the mixed boundary-value problem is transformed to a pair of integral equations termed dual integral equations in the literature, which generally can be reduced to a Fredholm integral equation of the second kind. With the aid of complex variable or contour integration the governing integral equation is numerically solved in the general dynamic case. The reduced static case of the dual integral equations is solved analytically and the vertical displacement, the contact pressure, and the static impedance/compliance function are explicitly solved. The dynamic contact pressure under the disc and the impedance function are numerically evaluated, and it is shown that the singularity that exists at the edge of the disc is the same as the one obtained for the static case. In addition, the impedance functions evaluated here are identical to the solution given by Luco and Mita for the isotropic domain. To show the effect of different material anisotropy, the numerical evaluations are given for some different transversely isotropic materials and compared. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.aip.org/vsearch/servlet/VerityServlet?KEY=JENMDT&smode=strres [...] [article] Forced vertical vibration of rigid circular disc on a transversely isotropic half-space [texte imprimé] / Eskandari-Ghadi, Morteza, Auteur ; Morteza Fallahi, Auteur ; Azizollah Ardeshir-Behrestaghi, Auteur . - pp. 913-922. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 136 N° 7 (Juillet 2010) . - pp. 913-922 Mots-clés : Isotropy  Half  space  Wave  propagation  Integral  equations  Soil-structure-interactions  Vibration. Résumé : Vertical vibration of a rigid circular disc attached to the surface of a transversely isotropic half-space is considered in such a way that the axis of material symmetry is normal to the surface of the half-space and parallel to the vibration direction. By using Hankel integral transforms, the mixed boundary-value problem is transformed to a pair of integral equations termed dual integral equations in the literature, which generally can be reduced to a Fredholm integral equation of the second kind. With the aid of complex variable or contour integration the governing integral equation is numerically solved in the general dynamic case. The reduced static case of the dual integral equations is solved analytically and the vertical displacement, the contact pressure, and the static impedance/compliance function are explicitly solved. The dynamic contact pressure under the disc and the impedance function are numerically evaluated, and it is shown that the singularity that exists at the edge of the disc is the same as the one obtained for the static case. In addition, the impedance functions evaluated here are identical to the solution given by Luco and Mita for the isotropic domain. To show the effect of different material anisotropy, the numerical evaluations are given for some different transversely isotropic materials and compared. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.aip.org/vsearch/servlet/VerityServlet?KEY=JENMDT&smode=strres [...]

Statistical moments of polynomial dimensional decomposition / Rahman, Sharif in Journal of engineering mechanics, Vol. 136 N° 7 (Juillet 2010) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 136 N° 7 (Juillet 2010) . - pp. 923-927 Titre : Statistical moments of polynomial dimensional decomposition Type de document : texte imprimé Auteurs : Rahman, Sharif, Auteur Article en page(s) : pp. 923-927 Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Stochastic  processes  Polynomials  Decomposition  Statistics. Résumé : This technical note presents explicit formulas for calculating the response moments of stochastic systems by polynomial dimensional decomposition entailing independent random input with arbitrary probability measures. The numerical results indicate that the formulas provide accurate, convergent, and computationally efficient estimates of the second-moment properties. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.aip.org/vsearch/servlet/VerityServlet?KEY=JENMDT&smode=strres [...] [article] Statistical moments of polynomial dimensional decomposition [texte imprimé] / Rahman, Sharif, Auteur . - pp. 923-927. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 136 N° 7 (Juillet 2010) . - pp. 923-927 Mots-clés : Stochastic  processes  Polynomials  Decomposition  Statistics. Résumé : This technical note presents explicit formulas for calculating the response moments of stochastic systems by polynomial dimensional decomposition entailing independent random input with arbitrary probability measures. The numerical results indicate that the formulas provide accurate, convergent, and computationally efficient estimates of the second-moment properties. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.aip.org/vsearch/servlet/VerityServlet?KEY=JENMDT&smode=strres [...]

Effect of welding on the slip damping of layered and jointed structures / Bhagat Singh in Journal of engineering mechanics, Vol. 136 N° 7 (Juillet 2010) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 136 N° 7 (Juillet 2010) . - pp. 928-932 Titre : Effect of welding on the slip damping of layered and jointed structures Type de document : texte imprimé Auteurs : Bhagat Singh, Auteur ; Bijoy Kumar Nanda, Auteur Article en page(s) : pp. 928-932 Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Welds  Spacing  Length  Thickness  Damping  Joints  Slip  Beams. Résumé : A mathematical model has been presented for the mechanism of interfacial slip damping in layered and jointed cantilever beams with continuous and tack welds. The pressure distribution at the interfaces, number of contacting layers, techniques of welding, length and thickness of the beam specimen, and amplitude and frequency of vibration are found to be the dominating factors influencing the damping capacity of such welded structures. The results can be exploited positively in the design of machine tools, aircraft, spacecraft, satellites, automobiles, missile systems, etc. for maximizing their damping capacity. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.aip.org/vsearch/servlet/VerityServlet?KEY=JENMDT&smode=strres [...] [article] Effect of welding on the slip damping of layered and jointed structures [texte imprimé] / Bhagat Singh, Auteur ; Bijoy Kumar Nanda, Auteur . - pp. 928-932. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 136 N° 7 (Juillet 2010) . - pp. 928-932 Mots-clés : Welds  Spacing  Length  Thickness  Damping  Joints  Slip  Beams. Résumé : A mathematical model has been presented for the mechanism of interfacial slip damping in layered and jointed cantilever beams with continuous and tack welds. The pressure distribution at the interfaces, number of contacting layers, techniques of welding, length and thickness of the beam specimen, and amplitude and frequency of vibration are found to be the dominating factors influencing the damping capacity of such welded structures. The results can be exploited positively in the design of machine tools, aircraft, spacecraft, satellites, automobiles, missile systems, etc. for maximizing their damping capacity. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.aip.org/vsearch/servlet/VerityServlet?KEY=JENMDT&smode=strres [...]

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