Dépouillements

Bending of composite stiffened hypar shell roofs under point load / Sarmila Sahoo in Journal of engineering mechanics, Vol. 134 n°6 (Juin 2008) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 134 n°6 (Juin 2008) . - pp. 441-454 Titre : Bending of composite stiffened hypar shell roofs under point load Type de document : texte imprimé Auteurs : Sarmila Sahoo, Auteur ; Dipankar Chakravorty, Auteur Année de publication : 2008 Article en page(s) : pp. 441-454 Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Shells  Composite  materials  Finite  element  method  Stiffness  Static  structural  analysis  Concentrated  loads  Bending  Roofs Résumé : The present paper applies a combination of an eight noded shell element with a three noded beam element, both curved and isoparametric to solve a bending problem of a composite stiffened hypar shell subjected to a concentrated load. Benchmark problems are solved to validate the suitability of the approach and a wide spectrum of stiffened hypar shell problems are solved by varying the lamination and curvature of simply supported and clamped shell surfaces. Different positions of stiffeners, both in plan and section, are considered together with variation of stiffener depth. Both static deflections and force/moment resultants are examined thoroughly. The performances of the different shell options are studied by arranging them rankwise and through a typical relative performance matrix, which will enable a designer to make a rational choice between a number of options. ISSN : 0733-9399 En ligne : http://cedb.asce.org/cgi/WWWdisplay.cgi?164542 [article] Bending of composite stiffened hypar shell roofs under point load [texte imprimé] / Sarmila Sahoo, Auteur ; Dipankar Chakravorty, Auteur . - 2008 . - pp. 441-454. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 134 n°6 (Juin 2008) . - pp. 441-454 Mots-clés : Shells  Composite  materials  Finite  element  method  Stiffness  Static  structural  analysis  Concentrated  loads  Bending  Roofs Résumé : The present paper applies a combination of an eight noded shell element with a three noded beam element, both curved and isoparametric to solve a bending problem of a composite stiffened hypar shell subjected to a concentrated load. Benchmark problems are solved to validate the suitability of the approach and a wide spectrum of stiffened hypar shell problems are solved by varying the lamination and curvature of simply supported and clamped shell surfaces. Different positions of stiffeners, both in plan and section, are considered together with variation of stiffener depth. Both static deflections and force/moment resultants are examined thoroughly. The performances of the different shell options are studied by arranging them rankwise and through a typical relative performance matrix, which will enable a designer to make a rational choice between a number of options. ISSN : 0733-9399 En ligne : http://cedb.asce.org/cgi/WWWdisplay.cgi?164542

Wrinkling and edge buckling in orthotropic sandwich beams / Wooseok Ji in Journal of engineering mechanics, Vol. 134 n°6 (Juin 2008) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 134 n°6 (Juin 2008) . - pp.455–461. Titre : Wrinkling and edge buckling in orthotropic sandwich beams Type de document : texte imprimé Auteurs : Wooseok Ji, Auteur ; Anthony M. Waas, Auteur Année de publication : 2008 Article en page(s) : pp.455–461. Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Sandwich  structures  Axial  compression  Elastic  analysis  Edge  effects  Finite  element  method  Buckling  Beams  Orthotropism Résumé : A sandwich beam buckling problem is studied here using two-dimensional elasticity to model the beam constituents. The global and local instability of such a beam with orthotropic constituents under various boundary conditions are investigated. The face sheet and the core are assumed to be linear elastic orthotropic continua. General buckling deformation modes of the sandwich beam subjected to uniaxial compressive loading are considered. The appropriate incremental stress and conjugate incremental finite-strain measure for the instability problem of the sandwich beam, and the corresponding constitutive model are addressed. It is shown that a sandwich beam having a core with a negligible stiffness compared to the face sheets is prone to fail by edge buckling. The present analysis is compared with several previous analytical studies and corresponding experimental results. Finite-element analyses are carried out for comparison against the theoretical predictions. The formulation used in the finite-element code is discussed in relation to the formulation adopted in the theoretical derivation. ISSN : 0733-9399 En ligne : http://ascelibrary.org/action/showAbstract?page=455&volume=134&issue=6&journalCo [...] [article] Wrinkling and edge buckling in orthotropic sandwich beams [texte imprimé] / Wooseok Ji, Auteur ; Anthony M. Waas, Auteur . - 2008 . - pp.455–461. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 134 n°6 (Juin 2008) . - pp.455–461. Mots-clés : Sandwich  structures  Axial  compression  Elastic  analysis  Edge  effects  Finite  element  method  Buckling  Beams  Orthotropism Résumé : A sandwich beam buckling problem is studied here using two-dimensional elasticity to model the beam constituents. The global and local instability of such a beam with orthotropic constituents under various boundary conditions are investigated. The face sheet and the core are assumed to be linear elastic orthotropic continua. General buckling deformation modes of the sandwich beam subjected to uniaxial compressive loading are considered. The appropriate incremental stress and conjugate incremental finite-strain measure for the instability problem of the sandwich beam, and the corresponding constitutive model are addressed. It is shown that a sandwich beam having a core with a negligible stiffness compared to the face sheets is prone to fail by edge buckling. The present analysis is compared with several previous analytical studies and corresponding experimental results. Finite-element analyses are carried out for comparison against the theoretical predictions. The formulation used in the finite-element code is discussed in relation to the formulation adopted in the theoretical derivation. ISSN : 0733-9399 En ligne : http://ascelibrary.org/action/showAbstract?page=455&volume=134&issue=6&journalCo [...]

Influence of structural design on the aeroelastic stability of brancusi 's endless column / R. D. Gabbai in Journal of engineering mechanics, Vol. 134 n°6 (Juin 2008) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 134 n°6 (Juin 2008) . - pp. 462–465. Titre : Influence of structural design on the aeroelastic stability of brancusi 's endless column Type de document : texte imprimé Auteurs : R. D. Gabbai, Auteur Année de publication : 2008 Article en page(s) : pp. 462–465. Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Aeroelasticity  Vortex  shedding  Wind  loads  Structural  engineering  Columns Résumé : Brancusi’s Endless Column (Târgu-Jiu, Romania) is an interesting case study in bluff body aeroelasticity. It has been referred to as aeroelastically indifferent owing to its remarkable aeroelastic stability. This stability has been attributed to its unconventional shape. Calculations are presented which show that this strictly aerodynamic view of the column behavior is incomplete, and that the structural dynamics characteristics of the column have a powerful role in ensuring its aeroelastic stability. The calculations show that the column’s design, which provided for significant damping and mass, would assure its aeroelastic stability even if the column had a conventional and aeroelastically less favorable shape, i.e., if it were a circular cylinder (a shape that is unfavorable from the point of view of vortex-induced response) or a square cylinder (a shape that is unfavorable from the point of view of galloping). ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282008%29134%3A6%2846 [...] [article] Influence of structural design on the aeroelastic stability of brancusi 's endless column [texte imprimé] / R. D. Gabbai, Auteur . - 2008 . - pp. 462–465. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 134 n°6 (Juin 2008) . - pp. 462–465. Mots-clés : Aeroelasticity  Vortex  shedding  Wind  loads  Structural  engineering  Columns Résumé : Brancusi’s Endless Column (Târgu-Jiu, Romania) is an interesting case study in bluff body aeroelasticity. It has been referred to as aeroelastically indifferent owing to its remarkable aeroelastic stability. This stability has been attributed to its unconventional shape. Calculations are presented which show that this strictly aerodynamic view of the column behavior is incomplete, and that the structural dynamics characteristics of the column have a powerful role in ensuring its aeroelastic stability. The calculations show that the column’s design, which provided for significant damping and mass, would assure its aeroelastic stability even if the column had a conventional and aeroelastically less favorable shape, i.e., if it were a circular cylinder (a shape that is unfavorable from the point of view of vortex-induced response) or a square cylinder (a shape that is unfavorable from the point of view of galloping). ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282008%29134%3A6%2846 [...]

Nontarget stereo vision technique for spatiotemporal response measurement of line-like structures / Y. F. Ji in Journal of engineering mechanics, Vol. 134 n°6 (Juin 2008) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 134 n°6 (Juin 2008) . - pp.466–474. Titre : Nontarget stereo vision technique for spatiotemporal response measurement of line-like structures Type de document : texte imprimé Auteurs : Y. F. Ji, Auteur ; C. C. Chang, Auteur Année de publication : 2008 Article en page(s) : pp.466–474. Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Measurement  Imaging  techniques  Displacement  Structural  response Résumé : With continuous advancement in optical, electronics, and computer technology, commercial digital cameras now are equipped with a high pixel resolution at a reasonable cost. Image sequences recorded by these cameras contain both spatial and temporal information of the target object; hence they can be used to extract the object’s dynamic responses and characteristics. This paper presents a nontarget stereo vision technique to measure response of a line-like structure simultaneously in both spatial and temporal domain. The technique uses two digital cameras to acquire image sequences of a line-like structure. It adopts a simple nondimensional length matching approach and the epipolar geometry to establish point correspondences within an image sequence and between two image sequences, respectively. After reconstructing a spatio-temporal displacement response from the two image sequences, wavelet transform is then used to extract the modal characteristics of the structure. The technique is illustrated using two free vibration tests: a steel cantilever beam and a bridge stay cable. Results show that the technique can measure the spatiotemporal responses, natural frequencies, and mode shapes of the two structures quite accurately. This image-based technique is a low-cost and simple-to-use approach that not only can complement current response measurement sensors but also offer special advantages which are hard to obtain using these traditional sensors. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282008%29134%3A6%2846 [...] [article] Nontarget stereo vision technique for spatiotemporal response measurement of line-like structures [texte imprimé] / Y. F. Ji, Auteur ; C. C. Chang, Auteur . - 2008 . - pp.466–474. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 134 n°6 (Juin 2008) . - pp.466–474. Mots-clés : Measurement  Imaging  techniques  Displacement  Structural  response Résumé : With continuous advancement in optical, electronics, and computer technology, commercial digital cameras now are equipped with a high pixel resolution at a reasonable cost. Image sequences recorded by these cameras contain both spatial and temporal information of the target object; hence they can be used to extract the object’s dynamic responses and characteristics. This paper presents a nontarget stereo vision technique to measure response of a line-like structure simultaneously in both spatial and temporal domain. The technique uses two digital cameras to acquire image sequences of a line-like structure. It adopts a simple nondimensional length matching approach and the epipolar geometry to establish point correspondences within an image sequence and between two image sequences, respectively. After reconstructing a spatio-temporal displacement response from the two image sequences, wavelet transform is then used to extract the modal characteristics of the structure. The technique is illustrated using two free vibration tests: a steel cantilever beam and a bridge stay cable. Results show that the technique can measure the spatiotemporal responses, natural frequencies, and mode shapes of the two structures quite accurately. This image-based technique is a low-cost and simple-to-use approach that not only can complement current response measurement sensors but also offer special advantages which are hard to obtain using these traditional sensors. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282008%29134%3A6%2846 [...]

Beam bending solutions based on nonlocal timoshenko beam theory / Wang, C. M. in Journal of engineering mechanics, Vol. 134 n°6 (Juin 2008) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 134 n°6 (Juin 2008) . - pp.475–481. Titre : Beam bending solutions based on nonlocal timoshenko beam theory Type de document : texte imprimé Auteurs : Wang, C. M., Auteur ; S. Kitipornchai, Auteur ; C. W. Lim, Auteur Année de publication : 2008 Article en page(s) : pp.475–481. Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Beams  Bending  Elasticity Résumé : This paper is concerned with the bending problem of micro- and nanobeams based on the Eringen nonlocal elasticity theory and Timoshenko beam theory. In the former theory, the small-scale effect is taken into consideration while the effect of transverse shear deformation is accounted for in the latter theory. The governing equations and the boundary conditions are derived using the principle of virtual work. General solutions for the deflection, rotation, and stress resultants are presented for transversely loaded beams. In addition, specialized bending solutions are given for beams with various end conditions. These solutions account for a better representation of the bending behavior of short, stubby, micro- and nanobeams where the small-scale effect and transverse shear deformation are significant. Considering particular loading and boundary conditions, the effects of small-scale and shear deformation on the bending results may be observed because of the analytical forms of the solutions. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282008%29134%3A6%2847 [...] [article] Beam bending solutions based on nonlocal timoshenko beam theory [texte imprimé] / Wang, C. M., Auteur ; S. Kitipornchai, Auteur ; C. W. Lim, Auteur . - 2008 . - pp.475–481. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 134 n°6 (Juin 2008) . - pp.475–481. Mots-clés : Beams  Bending  Elasticity Résumé : This paper is concerned with the bending problem of micro- and nanobeams based on the Eringen nonlocal elasticity theory and Timoshenko beam theory. In the former theory, the small-scale effect is taken into consideration while the effect of transverse shear deformation is accounted for in the latter theory. The governing equations and the boundary conditions are derived using the principle of virtual work. General solutions for the deflection, rotation, and stress resultants are presented for transversely loaded beams. In addition, specialized bending solutions are given for beams with various end conditions. These solutions account for a better representation of the bending behavior of short, stubby, micro- and nanobeams where the small-scale effect and transverse shear deformation are significant. Considering particular loading and boundary conditions, the effects of small-scale and shear deformation on the bending results may be observed because of the analytical forms of the solutions. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282008%29134%3A6%2847 [...]

Adaptive parametric identification scheme for a class of nondeteriorating and deteriorating nonlinear hysteretic behavior / Seyed Ali Ashrafi in Journal of engineering mechanics, Vol. 134 n°6 (Juin 2008) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 134 n°6 (Juin 2008) . - pp.482–494. Titre : Adaptive parametric identification scheme for a class of nondeteriorating and deteriorating nonlinear hysteretic behavior Type de document : texte imprimé Auteurs : Seyed Ali Ashrafi, Auteur ; Andrew W. Smyth, Auteur Année de publication : 2008 Article en page(s) : pp.482–494. Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Parameters  Deterioration  Hysteresis Résumé : The adaptive parametric identification of deteriorating and nondeteriorating nonlinear hysteretic phenomena is considered using a generalization of Masing model based on the observed memory behavior of distributed element models. The model permits a parametric identification to be performed using nonlinear optimization techniques for arbitrary response time histories. A changing objective function, defined as the normalized force estimation error over a shifting window of recent data, is employed so that classic nonlinear optimization techniques can be used for the adaptive identification problem. A variation of the steepest descent method is used with significant modifications. To achieve the best performance for any given problem, a set of a priori numeric tests are suggested to design the identification scheme. The design identification scheme exhibits a very good performance in identifying the correct values of the parameters and is rather robust in dealing with noise. The proposed approach has applications to adaptive identification of much wider types of nonlinear rate-dependent hysteretic behavior. Also, the set of guidelines proposed by the authors is a contribution toward having more effective autonomous identification schemes, using minimal information about the model and input. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282008%29134%3A6%2848 [...] [article] Adaptive parametric identification scheme for a class of nondeteriorating and deteriorating nonlinear hysteretic behavior [texte imprimé] / Seyed Ali Ashrafi, Auteur ; Andrew W. Smyth, Auteur . - 2008 . - pp.482–494. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 134 n°6 (Juin 2008) . - pp.482–494. Mots-clés : Parameters  Deterioration  Hysteresis Résumé : The adaptive parametric identification of deteriorating and nondeteriorating nonlinear hysteretic phenomena is considered using a generalization of Masing model based on the observed memory behavior of distributed element models. The model permits a parametric identification to be performed using nonlinear optimization techniques for arbitrary response time histories. A changing objective function, defined as the normalized force estimation error over a shifting window of recent data, is employed so that classic nonlinear optimization techniques can be used for the adaptive identification problem. A variation of the steepest descent method is used with significant modifications. To achieve the best performance for any given problem, a set of a priori numeric tests are suggested to design the identification scheme. The design identification scheme exhibits a very good performance in identifying the correct values of the parameters and is rather robust in dealing with noise. The proposed approach has applications to adaptive identification of much wider types of nonlinear rate-dependent hysteretic behavior. Also, the set of guidelines proposed by the authors is a contribution toward having more effective autonomous identification schemes, using minimal information about the model and input. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282008%29134%3A6%2848 [...]

Probabilistic seismic demand models and fragility estimates for reinforced Concrete bridges with two-column bents / Jinquan Zhong in Journal of engineering mechanics, Vol. 134 n°6 (Juin 2008) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 134 n°6 (Juin 2008) . - pp.495–504. Titre : Probabilistic seismic demand models and fragility estimates for reinforced Concrete bridges with two-column bents Type de document : texte imprimé Auteurs : Jinquan Zhong, Auteur ; Paolo Gardoni, Auteur ; Rosowsky, David, Auteur Année de publication : 2008 Article en page(s) : pp.495–504. Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Bridges  Concrete  Structural  reliability  Bayesian  analysis  Seismic  effects  Columns  Deformation Résumé : Probabilistic models are developed to predict the deformation and shear demands due to seismic excitation on reinforced concrete (RC) columns in bridges with two-column bents. A Bayesian methodology is used to develop the models. The models are unbiased and properly account for the predominant uncertainties, including model errors, arising from a potentially inaccurate model form or missing variables, measurement errors, and statistical uncertainty. The probabilistic models developed are akin to deterministic demand models and procedures commonly used in practice, but they have additional correction terms that explicitly describe the inherent systematic and random errors. Through the use of a set of “explanatory” functions, terms that correct the bias in the existing deterministic demand models are identified. These explanatory functions provide insight into the underlying behavioral phenomena and provide a means to select ground motion parameters that are most relevant to the seismic demands. The approach takes into account information gained from scientific/engineering laws, observational data from laboratory experiments, and simulated data from numerical dynamic responses. The demand models are combined with previously developed probabilistic capacity models for RC bridge columns to objectively estimate the seismic vulnerability of bridge components and systems. The vulnerability is expressed in terms of the conditional probability (or fragility) that a demand quantity (deformation or shear) will be greater than or equal to the corresponding capacity. Fragility estimates are developed for an example RC bridge with two-column bents, designed based on the current specifications for California. Fragility estimates are computed at the individual column, bent, and bridge system levels, as a function of the spectral acceleration and the ratio between the peak ground velocity and the peak ground acceleration. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282008%29134%3A6%2849 [...] [article] Probabilistic seismic demand models and fragility estimates for reinforced Concrete bridges with two-column bents [texte imprimé] / Jinquan Zhong, Auteur ; Paolo Gardoni, Auteur ; Rosowsky, David, Auteur . - 2008 . - pp.495–504. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 134 n°6 (Juin 2008) . - pp.495–504. Mots-clés : Bridges  Concrete  Structural  reliability  Bayesian  analysis  Seismic  effects  Columns  Deformation Résumé : Probabilistic models are developed to predict the deformation and shear demands due to seismic excitation on reinforced concrete (RC) columns in bridges with two-column bents. A Bayesian methodology is used to develop the models. The models are unbiased and properly account for the predominant uncertainties, including model errors, arising from a potentially inaccurate model form or missing variables, measurement errors, and statistical uncertainty. The probabilistic models developed are akin to deterministic demand models and procedures commonly used in practice, but they have additional correction terms that explicitly describe the inherent systematic and random errors. Through the use of a set of “explanatory” functions, terms that correct the bias in the existing deterministic demand models are identified. These explanatory functions provide insight into the underlying behavioral phenomena and provide a means to select ground motion parameters that are most relevant to the seismic demands. The approach takes into account information gained from scientific/engineering laws, observational data from laboratory experiments, and simulated data from numerical dynamic responses. The demand models are combined with previously developed probabilistic capacity models for RC bridge columns to objectively estimate the seismic vulnerability of bridge components and systems. The vulnerability is expressed in terms of the conditional probability (or fragility) that a demand quantity (deformation or shear) will be greater than or equal to the corresponding capacity. Fragility estimates are developed for an example RC bridge with two-column bents, designed based on the current specifications for California. Fragility estimates are computed at the individual column, bent, and bridge system levels, as a function of the spectral acceleration and the ratio between the peak ground velocity and the peak ground acceleration. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282008%29134%3A6%2849 [...]

Elastic model for partially saturated granular materials / Hicher,P.-Y. in Journal of engineering mechanics, Vol. 134 n°6 (Juin 2008) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 134 n°6 (Juin 2008) . - pp.505–513. Titre : Elastic model for partially saturated granular materials Type de document : texte imprimé Auteurs : Hicher,P.-Y., Auteur ; C. S. Chang, Auteur Année de publication : 2008 Article en page(s) : pp.505–513. Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Granular  materials  Stress  strain  relations  Elastic  deformation  Unsaturated  soils  Soil  suction  Micromechanics Résumé : This paper presents the development of an elastic model for partially saturated granular materials based on micromechanical factor consideration. A granular material is considered as an assembly of particles. The stress-strain relationship for an assembly can be determined by integrating the behavior at all interparticle contacts and by using a static hypothesis, which relates the average stress of the granular assembly to a mean field of particle contact forces. As for the nonsaturated state, capillary forces at grain contacts are added to the contact forces created by an external load. These are then calculated as a function of the degree of saturation, depending on the grain size distribution and on the void ratio of the granular assembly. Hypothesizing a Hertz-Mindlin law for the grain contacts leads to an elastic nonlinear behavior of the particulate material. The prediction of the stress-strain model is compared to experimental results obtained from several different granular materials in dry, partially saturated and fully saturated states. The numerical predictions demonstrate that the model is capable of taking into account the influence of key parameters, such as degree of saturation, void ratio, and mean stress. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282008%29134%3A6%2850 [...] [article] Elastic model for partially saturated granular materials [texte imprimé] / Hicher,P.-Y., Auteur ; C. S. Chang, Auteur . - 2008 . - pp.505–513. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 134 n°6 (Juin 2008) . - pp.505–513. Mots-clés : Granular  materials  Stress  strain  relations  Elastic  deformation  Unsaturated  soils  Soil  suction  Micromechanics Résumé : This paper presents the development of an elastic model for partially saturated granular materials based on micromechanical factor consideration. A granular material is considered as an assembly of particles. The stress-strain relationship for an assembly can be determined by integrating the behavior at all interparticle contacts and by using a static hypothesis, which relates the average stress of the granular assembly to a mean field of particle contact forces. As for the nonsaturated state, capillary forces at grain contacts are added to the contact forces created by an external load. These are then calculated as a function of the degree of saturation, depending on the grain size distribution and on the void ratio of the granular assembly. Hypothesizing a Hertz-Mindlin law for the grain contacts leads to an elastic nonlinear behavior of the particulate material. The prediction of the stress-strain model is compared to experimental results obtained from several different granular materials in dry, partially saturated and fully saturated states. The numerical predictions demonstrate that the model is capable of taking into account the influence of key parameters, such as degree of saturation, void ratio, and mean stress. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282008%29134%3A6%2850 [...]

Initial Compressive buckling of clamped plates resting on tensionless elastic or rigid foundations / Xing Ma in Journal of engineering mechanics, Vol. 134 n°6 (Juin 2008) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 134 n°6 (Juin 2008) . - pp.514–518. Titre : Initial Compressive buckling of clamped plates resting on tensionless elastic or rigid foundations Type de document : texte imprimé Auteurs : Xing Ma, Auteur ; John Butterworth, Auteur ; Charles Clifton, Auteur Année de publication : 2008 Article en page(s) : pp.514–518. Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Compression  Contacts  Buckling  Plates  Foundations Résumé : The unilateral contact buckling problem of thin plates resting on tensionless foundations is investigated. Three different plate models are considered. For a plate of limited length on a tensionless elastic foundation, the plate is first simplified to a one-dimensional mechanical model by assuming a buckling mode in terms of transverse coordinates, after which a new method is employed to determine the initially unknown boundaries of the areas in contact. Based on the continuity condition on the borderline between contact and noncontact regions, the buckling mode displacements of the whole plate may be expressed through the critical load coefficient and the first half-wavelength, reducing the buckling problem to two nonlinear algebraic equations with two unknowns. This procedure has been named the transfer function method. For a very long plate with a symmetric buckling mode, an infinite plate model with two half-waves is presented. For a plate on a rigid foundation, a single half-wave buckling model is shown to be appropriate. Comparison of limiting cases with exact solutions and with ABAQUS results showed good agreement. Finally, the influences of aspect ratio and foundation stiffness are presented. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282008%29134%3A6%2851 [...] [article] Initial Compressive buckling of clamped plates resting on tensionless elastic or rigid foundations [texte imprimé] / Xing Ma, Auteur ; John Butterworth, Auteur ; Charles Clifton, Auteur . - 2008 . - pp.514–518. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 134 n°6 (Juin 2008) . - pp.514–518. Mots-clés : Compression  Contacts  Buckling  Plates  Foundations Résumé : The unilateral contact buckling problem of thin plates resting on tensionless foundations is investigated. Three different plate models are considered. For a plate of limited length on a tensionless elastic foundation, the plate is first simplified to a one-dimensional mechanical model by assuming a buckling mode in terms of transverse coordinates, after which a new method is employed to determine the initially unknown boundaries of the areas in contact. Based on the continuity condition on the borderline between contact and noncontact regions, the buckling mode displacements of the whole plate may be expressed through the critical load coefficient and the first half-wavelength, reducing the buckling problem to two nonlinear algebraic equations with two unknowns. This procedure has been named the transfer function method. For a very long plate with a symmetric buckling mode, an infinite plate model with two half-waves is presented. For a plate on a rigid foundation, a single half-wave buckling model is shown to be appropriate. Comparison of limiting cases with exact solutions and with ABAQUS results showed good agreement. Finally, the influences of aspect ratio and foundation stiffness are presented. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282008%29134%3A6%2851 [...]

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