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Ajouter le résultat dans votre panierAnalysis of the vertical profile of concentration in sediment-laden flows / Qing-Quan Liu in Journal of engineering mechanics, Vol. 133 N°6 (Juin 2007)
in Journal of engineering mechanics > Vol. 133 N°6 (Juin 2007) . - pp.601–607.
Titre : Analysis of the vertical profile of concentration in sediment-laden flows Type de document : texte imprimé Auteurs : Qing-Quan Liu, Auteur ; An-Ping Shu, Auteur ; Singh, Vijay P., Auteur Année de publication : 2007 Article en page(s) : pp.601–607. Note générale : Applied mechanics Langues : Anglais (eng) Mots-clés : Sediment concentration Turbulent diffusion Sediment transport Résumé : From a theoretical investigation of the sediment concentration distribution in sediment-laden flows, a relationship between the profile of sediment concentration and the intensity of vertical fluctuation of particles was established and indirectly verified using experimental data obtained in a vertical rectangular duct flow. It is shown that sediment suspension and the profile of sediment concentration are significantly influenced by the particle fluctuation. This leads to a new explanation for the mechanism of two patterns of sediment concentration profiles. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282007%29133%3A6%2860 [...] [article] Analysis of the vertical profile of concentration in sediment-laden flows [texte imprimé] / Qing-Quan Liu, Auteur ; An-Ping Shu, Auteur ; Singh, Vijay P., Auteur . - 2007 . - pp.601–607.
Applied mechanics
Langues : Anglais (eng)
in Journal of engineering mechanics > Vol. 133 N°6 (Juin 2007) . - pp.601–607.
Mots-clés : Sediment concentration Turbulent diffusion Sediment transport Résumé : From a theoretical investigation of the sediment concentration distribution in sediment-laden flows, a relationship between the profile of sediment concentration and the intensity of vertical fluctuation of particles was established and indirectly verified using experimental data obtained in a vertical rectangular duct flow. It is shown that sediment suspension and the profile of sediment concentration are significantly influenced by the particle fluctuation. This leads to a new explanation for the mechanism of two patterns of sediment concentration profiles. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282007%29133%3A6%2860 [...]
in Journal of engineering mechanics > Vol. 133 N°6 (Juin 2007) . - pp.608–615.
Titre : Comparison between hydraulic and thermal spalling in heated concrete based on numerical modeling Type de document : texte imprimé Auteurs : Msaad, Y., Auteur Année de publication : 2007 Article en page(s) : pp.608–615. Note générale : Applied mechanics Langues : Anglais (eng) Mots-clés : Numerical models Concrete Heating Thermal factors Spalling Résumé : Two spalling mechanisms are generally quoted in literature. The first one is due to pore pressure buildup (tensile stresses). The second one is generated by restrained thermal dilation (compressive stresses). This paper presents a thermoporoelastic model in order to compare the thermal effect (restrained thermal dilation) and the hydraulic one (pore pressures). An infinite heated wall is studied analytically to express the different effective stresses exerted on the skeleton. Then, the origins of these stresses are identified. By comparing the thermal contribution and the hydraulic one, it was deduced that we cannot neglect any of them in the spalling mechanism. ISSN : 0733-9399 En ligne : http://ascelibrary.org/action/showAbstract?page=608&volume=133&issue=6&journalCo [...] [article] Comparison between hydraulic and thermal spalling in heated concrete based on numerical modeling [texte imprimé] / Msaad, Y., Auteur . - 2007 . - pp.608–615.
Applied mechanics
Langues : Anglais (eng)
in Journal of engineering mechanics > Vol. 133 N°6 (Juin 2007) . - pp.608–615.
Mots-clés : Numerical models Concrete Heating Thermal factors Spalling Résumé : Two spalling mechanisms are generally quoted in literature. The first one is due to pore pressure buildup (tensile stresses). The second one is generated by restrained thermal dilation (compressive stresses). This paper presents a thermoporoelastic model in order to compare the thermal effect (restrained thermal dilation) and the hydraulic one (pore pressures). An infinite heated wall is studied analytically to express the different effective stresses exerted on the skeleton. Then, the origins of these stresses are identified. By comparing the thermal contribution and the hydraulic one, it was deduced that we cannot neglect any of them in the spalling mechanism. ISSN : 0733-9399 En ligne : http://ascelibrary.org/action/showAbstract?page=608&volume=133&issue=6&journalCo [...]
in Journal of engineering mechanics > Vol. 133 N°6 (Juin 2007) . - pp.616–627.
Titre : Simulation of nonstationary stochastic processes by spectral representation Type de document : texte imprimé Auteurs : Liang, Jianwen, Auteur ; Chaudhuri, Samit Ray, Auteur ; Masanobu Shinozuka, Auteur Année de publication : 2007 Article en page(s) : pp.616–627. Note générale : Applied mechanics Langues : Anglais (eng) Mots-clés : Stationary processes Simulation Stochastic process Fourier transform Ground motion Power spectral density Résumé : This paper presents a rigorous derivation of a previously known formula for simulation of one-dimensional, univariate, nonstationary stochastic processes integrating Priestly’s evolutionary spectral representation theory. Applying this formula, sample functions can be generated with great computational efficiency. The simulated stochastic process is asymptotically Gaussian as the number of terms tends to infinity. This paper shows that (1) these sample functions accurately reflect the prescribed probabilistic characteristics of the stochastic process when the number of terms in the cosine series is large, i.e., the ensemble averaged evolutionary power spectral density function (PSDF) or autocorrelation function approaches the corresponding target function as the sample size increases, and (2) the simulation formula, under certain conditions, can be reduced to that for nonstationary white noise process or Shinozuka’s spectral representation of stationary process. In addition to derivation of simulation formula, three methods are developed in this paper to estimate the evolutionary PSDF of a given time-history data by means of the short-time Fourier transform (STFT), the wavelet transform (WT), and the Hilbert-Huang transform (HHT). A comparison of the PSDF of the well-known El Centro earthquake record estimated by these methods shows that the STFT and the WT give similar results, whereas the HHT gives more concentrated energy at certain frequencies. Effectiveness of the proposed simulation formula for nonstationary sample functions is demonstrated by simulating time histories from the estimated evolutionary PSDFs. Mean acceleration spectrum obtained by averaging the spectra of generated time histories are then presented and compared with the target spectrum to demonstrate the usefulness of this method. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282007%29133%3A6%2861 [...] [article] Simulation of nonstationary stochastic processes by spectral representation [texte imprimé] / Liang, Jianwen, Auteur ; Chaudhuri, Samit Ray, Auteur ; Masanobu Shinozuka, Auteur . - 2007 . - pp.616–627.
Applied mechanics
Langues : Anglais (eng)
in Journal of engineering mechanics > Vol. 133 N°6 (Juin 2007) . - pp.616–627.
Mots-clés : Stationary processes Simulation Stochastic process Fourier transform Ground motion Power spectral density Résumé : This paper presents a rigorous derivation of a previously known formula for simulation of one-dimensional, univariate, nonstationary stochastic processes integrating Priestly’s evolutionary spectral representation theory. Applying this formula, sample functions can be generated with great computational efficiency. The simulated stochastic process is asymptotically Gaussian as the number of terms tends to infinity. This paper shows that (1) these sample functions accurately reflect the prescribed probabilistic characteristics of the stochastic process when the number of terms in the cosine series is large, i.e., the ensemble averaged evolutionary power spectral density function (PSDF) or autocorrelation function approaches the corresponding target function as the sample size increases, and (2) the simulation formula, under certain conditions, can be reduced to that for nonstationary white noise process or Shinozuka’s spectral representation of stationary process. In addition to derivation of simulation formula, three methods are developed in this paper to estimate the evolutionary PSDF of a given time-history data by means of the short-time Fourier transform (STFT), the wavelet transform (WT), and the Hilbert-Huang transform (HHT). A comparison of the PSDF of the well-known El Centro earthquake record estimated by these methods shows that the STFT and the WT give similar results, whereas the HHT gives more concentrated energy at certain frequencies. Effectiveness of the proposed simulation formula for nonstationary sample functions is demonstrated by simulating time histories from the estimated evolutionary PSDFs. Mean acceleration spectrum obtained by averaging the spectra of generated time histories are then presented and compared with the target spectrum to demonstrate the usefulness of this method. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282007%29133%3A6%2861 [...]
in Journal of engineering mechanics > Vol. 133 N°6 (Juin 2007) . - pp.628–640.
Titre : Imaging concrete structures using air-coupled impact-echo Type de document : texte imprimé Auteurs : Jinying Zhu, Auteur ; John S. Popovics, Auteur Année de publication : 2007 Article en page(s) : pp.628–640. Note générale : Applied mechanics Langues : Anglais (eng) Mots-clés : Concrete structures Ducts Imaging techniques Nondestructive tests Sensors Résumé : In this paper, air-coupled impact-echo is successfully applied for nondestructive evaluation of concrete. The air-coupled sensor is a small ( [Math Processing Error] diameter) measurement microphone located several centimeters above the top surface of the concrete being evaluated. Unwanted ambient acoustic noise is attenuated by a specially designed sound insulation enclosure. Test results show that air-coupled sensors are effective for impact-echo when appropriate impactors are used. Impact-echo data obtained by air-coupled sensors are equivalent to those obtained by conventional contact sensors. Test results from concrete slabs containing artificial delaminations and voids are reported, where an air-coupled impact-echo scan is conducted over the entire slab area. Defects are located in the generated two-dimensional contour image. The areal size of defects are accurately determined when the measurement point spacing in the scan is smaller than half of the expected defect size. Test results from air-coupled impact-echo scans carried out over internal metal and plastic ducts within another concrete slab are also reported. The goal of the experiment is to investigate the grouting condition inside the ducts. Impact-echo line scan images differentiate poorly grouted sections from the well-grouted sections within the metal duct. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282007%29133%3A6%2862 [...] [article] Imaging concrete structures using air-coupled impact-echo [texte imprimé] / Jinying Zhu, Auteur ; John S. Popovics, Auteur . - 2007 . - pp.628–640.
Applied mechanics
Langues : Anglais (eng)
in Journal of engineering mechanics > Vol. 133 N°6 (Juin 2007) . - pp.628–640.
Mots-clés : Concrete structures Ducts Imaging techniques Nondestructive tests Sensors Résumé : In this paper, air-coupled impact-echo is successfully applied for nondestructive evaluation of concrete. The air-coupled sensor is a small ( [Math Processing Error] diameter) measurement microphone located several centimeters above the top surface of the concrete being evaluated. Unwanted ambient acoustic noise is attenuated by a specially designed sound insulation enclosure. Test results show that air-coupled sensors are effective for impact-echo when appropriate impactors are used. Impact-echo data obtained by air-coupled sensors are equivalent to those obtained by conventional contact sensors. Test results from concrete slabs containing artificial delaminations and voids are reported, where an air-coupled impact-echo scan is conducted over the entire slab area. Defects are located in the generated two-dimensional contour image. The areal size of defects are accurately determined when the measurement point spacing in the scan is smaller than half of the expected defect size. Test results from air-coupled impact-echo scans carried out over internal metal and plastic ducts within another concrete slab are also reported. The goal of the experiment is to investigate the grouting condition inside the ducts. Impact-echo line scan images differentiate poorly grouted sections from the well-grouted sections within the metal duct. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282007%29133%3A6%2862 [...]
in Journal of engineering mechanics > Vol. 133 N°6 (Juin 2007) . - pp.641–655.
Titre : Variational solutions for externally induced sloshing in horizontal-cylindrical and spherical vessels Type de document : texte imprimé Auteurs : Lazaros A. Patkas, Auteur ; Spyros A. Karamanos, Auteur Année de publication : 2007 Article en page(s) : pp.641–655. Note générale : Applied mechanics Langues : Anglais (eng) Mots-clés : Earthquakes Mathematical models Excitation Seismic analysis Résumé : A mathematical model is developed for calculating linear sloshing effects in the dynamic response of horizontal-cylindrical and spherical liquid containers under external excitation, with emphasis on earthquake excitation. The velocity potential is expressed in a series form, where each term is the product of a time function and the associated spatial function. Because of the configuration of the containers, the associated spatial functions are nonorthogonal and the problem is not separable, resulting in a system of coupled nonhomogeneous ordinary linear differential equations of motion. The solution can be obtained through either direct integration or modal analysis. Particular emphasis is given on the rate of convergence of the solution. The cases of half-full cylinders and spheres are examined in detail, where explicit expressions for the coefficients of the governing equations are derived. Using the proposed methodology, sloshing frequencies and masses are calculated rigorously for arbitrary liquid height of horizontal-cylindrical or spherical containers, and the response under two characteristic seismic events is obtained. The results describe the linear dynamic response of such containers and can be used for an efficient seismic analysis and design of industrial pressure vessels. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282007%29133%3A6%2864 [...] [article] Variational solutions for externally induced sloshing in horizontal-cylindrical and spherical vessels [texte imprimé] / Lazaros A. Patkas, Auteur ; Spyros A. Karamanos, Auteur . - 2007 . - pp.641–655.
Applied mechanics
Langues : Anglais (eng)
in Journal of engineering mechanics > Vol. 133 N°6 (Juin 2007) . - pp.641–655.
Mots-clés : Earthquakes Mathematical models Excitation Seismic analysis Résumé : A mathematical model is developed for calculating linear sloshing effects in the dynamic response of horizontal-cylindrical and spherical liquid containers under external excitation, with emphasis on earthquake excitation. The velocity potential is expressed in a series form, where each term is the product of a time function and the associated spatial function. Because of the configuration of the containers, the associated spatial functions are nonorthogonal and the problem is not separable, resulting in a system of coupled nonhomogeneous ordinary linear differential equations of motion. The solution can be obtained through either direct integration or modal analysis. Particular emphasis is given on the rate of convergence of the solution. The cases of half-full cylinders and spheres are examined in detail, where explicit expressions for the coefficients of the governing equations are derived. Using the proposed methodology, sloshing frequencies and masses are calculated rigorously for arbitrary liquid height of horizontal-cylindrical or spherical containers, and the response under two characteristic seismic events is obtained. The results describe the linear dynamic response of such containers and can be used for an efficient seismic analysis and design of industrial pressure vessels. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282007%29133%3A6%2864 [...]
in Journal of engineering mechanics > Vol. 133 N°6 (Juin 2007) . - pp.656–664.
Titre : Flexible videogrammetric technique for three-dimensional structural vibration measurement Type de document : texte imprimé Auteurs : C. C. Chang, Auteur ; Y. F. Ji, Auteur Année de publication : 2007 Article en page(s) : pp.656–664. Note générale : Applied mechanics Langues : Anglais (eng) Mots-clés : Photogrammetry Vibration Dynamic response Measurement Imaging techniques. Résumé : A videogrammetric technique is proposed for measuring three-dimensional structural vibration response in the laboratory. The technique is based on the principles of close-range digital photogrammetry and computer vision. Two commercial-grade digital video cameras are used for image acquisition. To calibrate these cameras and to overcome potential lens distortion problems, an innovative two-step calibration process including individual and stereo calibration is proposed. These calibrations are efficiently done using a planar pattern arbitrarily shown at a few different orientations. This special characteristic makes it possible to perform an on-site calibration that provides flexibility in terms of using different camera settings to suit various application conditions. To validate the proposed technique, three tests, including sinusoidal motion of a point, wind tunnel test of a cross-section bridge model, and a three-story building model under earthquake excitation, are performed. Results indicate that the proposed videogrammetric technique can provide fairly accurate displacement measurement for all three tests. The proposed technique is shown to be a good complement to the traditional sensors for measuring two- or three-dimensional vibration response in the low-frequency range. ISSN : 0733-9399 En ligne : http://ascelibrary.org/action/showAbstract?page=656&volume=133&issue=6&journalCo [...] [article] Flexible videogrammetric technique for three-dimensional structural vibration measurement [texte imprimé] / C. C. Chang, Auteur ; Y. F. Ji, Auteur . - 2007 . - pp.656–664.
Applied mechanics
Langues : Anglais (eng)
in Journal of engineering mechanics > Vol. 133 N°6 (Juin 2007) . - pp.656–664.
Mots-clés : Photogrammetry Vibration Dynamic response Measurement Imaging techniques. Résumé : A videogrammetric technique is proposed for measuring three-dimensional structural vibration response in the laboratory. The technique is based on the principles of close-range digital photogrammetry and computer vision. Two commercial-grade digital video cameras are used for image acquisition. To calibrate these cameras and to overcome potential lens distortion problems, an innovative two-step calibration process including individual and stereo calibration is proposed. These calibrations are efficiently done using a planar pattern arbitrarily shown at a few different orientations. This special characteristic makes it possible to perform an on-site calibration that provides flexibility in terms of using different camera settings to suit various application conditions. To validate the proposed technique, three tests, including sinusoidal motion of a point, wind tunnel test of a cross-section bridge model, and a three-story building model under earthquake excitation, are performed. Results indicate that the proposed videogrammetric technique can provide fairly accurate displacement measurement for all three tests. The proposed technique is shown to be a good complement to the traditional sensors for measuring two- or three-dimensional vibration response in the low-frequency range. ISSN : 0733-9399 En ligne : http://ascelibrary.org/action/showAbstract?page=656&volume=133&issue=6&journalCo [...]
in Journal of engineering mechanics > Vol. 133 N°6 (Juin 2007) . - pp.665–676.
Titre : Particle image velocimetry measurements of the mean flow characteristics in a bubble plume Type de document : texte imprimé Auteurs : Dong-Guan Seol, Auteur ; Tirtharaj Bhaumik, Auteur ; Christian Bergmann, Auteur Année de publication : 2007 Article en page(s) : pp.665–676. Note générale : Applied mechanics Langues : Anglais (eng) Mots-clés : Bubbles Plumes Two phase flow Entrainment Laboratory tests Experimental data Velocity distribution Dimensional analysis Résumé : A direct measurement method for the velocity field in multiphase flows using the particle image velocimetry (PIV) and particle tracking velocimetry (PTV) methods is developed to study the flow characteristics of an unbounded bubble plume in quiescent, unstratified ambient conditions. A single camera is used to obtain images containing both bubbles and fluid tracer particles. Using gray-scale thresholding, phase-separated images of the bubbles are produced, and bubble velocities are obtained from these images using the standard PTV method. Regular PIV is applied to the mixed fluid images, and bubble vectors are removed using a velocity threshold and vector median filter that is calibrated to the PTV result. From the separate velocity fields, the time-averaged flow characteristics of a bubble plume are studied. Gaussian velocity profiles match the entrained fluid velocity, and top-hat velocity profiles match the bubble velocity. Time-averaged values are also presented of velocity, plume width, entrained fluid volume flux, and void fraction as a function of height. From these data, the entrainment coefficient for the entrained ambient fluid is calculated and lies between 0.08 near the plume source and 0.05 in the upper reaches. The results for the entrainment coefficient, together with those from the literature, are correlated to a nondimensional velocity, given by the ratio of the bubble slip velocity us to a characteristic velocity in the plume (B/z)1/3 , where B=kinematic buoyancy flux and z is the height above the source. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282007%29133%3A6%2866 [...] [article] Particle image velocimetry measurements of the mean flow characteristics in a bubble plume [texte imprimé] / Dong-Guan Seol, Auteur ; Tirtharaj Bhaumik, Auteur ; Christian Bergmann, Auteur . - 2007 . - pp.665–676.
Applied mechanics
Langues : Anglais (eng)
in Journal of engineering mechanics > Vol. 133 N°6 (Juin 2007) . - pp.665–676.
Mots-clés : Bubbles Plumes Two phase flow Entrainment Laboratory tests Experimental data Velocity distribution Dimensional analysis Résumé : A direct measurement method for the velocity field in multiphase flows using the particle image velocimetry (PIV) and particle tracking velocimetry (PTV) methods is developed to study the flow characteristics of an unbounded bubble plume in quiescent, unstratified ambient conditions. A single camera is used to obtain images containing both bubbles and fluid tracer particles. Using gray-scale thresholding, phase-separated images of the bubbles are produced, and bubble velocities are obtained from these images using the standard PTV method. Regular PIV is applied to the mixed fluid images, and bubble vectors are removed using a velocity threshold and vector median filter that is calibrated to the PTV result. From the separate velocity fields, the time-averaged flow characteristics of a bubble plume are studied. Gaussian velocity profiles match the entrained fluid velocity, and top-hat velocity profiles match the bubble velocity. Time-averaged values are also presented of velocity, plume width, entrained fluid volume flux, and void fraction as a function of height. From these data, the entrainment coefficient for the entrained ambient fluid is calculated and lies between 0.08 near the plume source and 0.05 in the upper reaches. The results for the entrainment coefficient, together with those from the literature, are correlated to a nondimensional velocity, given by the ratio of the bubble slip velocity us to a characteristic velocity in the plume (B/z)1/3 , where B=kinematic buoyancy flux and z is the height above the source. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282007%29133%3A6%2866 [...]
in Journal of engineering mechanics > Vol. 133 N°6 (Juin 2007) . - pp.677–687.
Titre : Modeling cracking in shell-type reinforced concrete structures Type de document : texte imprimé Auteurs : Wenyuan Wang, Auteur ; Susanto Teng, Auteur Année de publication : 2007 Article en page(s) : pp.677–687. Note générale : Applied mechanics Langues : Anglais (eng) Mots-clés : Concrete structures Cracking Concrete reinforced Finite element method Shell structures Numerical analysis Résumé : A three-dimensional (3D) hypoelastic material model for modeling material properties of cracked reinforced concrete is proposed. Material properties of multidirectionally cracked reinforced concrete are represented by the material properties of intact concrete and a number of uniaxially cracked concrete with their coupling solids. Cracking effects due to multiple nonorthogonal cracks are traced in each uniaxially cracked concrete. Tension softening and aggregate interlock occurring at the crack interface as well as tension stiffening and compression softening initiated in concrete between cracks due to multiple nonorthogonal cracks are all incorporated explicitly. RC panels under in-plane loading and RC slab under pure torsion have been analyzed. The developed 3D hypoelastic material model has been proved to be efficient and effective in modeling the material behaviors of cracked reinforced concrete in shell-type RC structures. The deformational response, the ultimate strength, and failure mode can be captured reasonably well. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282007%29133%3A6%2867 [...] [article] Modeling cracking in shell-type reinforced concrete structures [texte imprimé] / Wenyuan Wang, Auteur ; Susanto Teng, Auteur . - 2007 . - pp.677–687.
Applied mechanics
Langues : Anglais (eng)
in Journal of engineering mechanics > Vol. 133 N°6 (Juin 2007) . - pp.677–687.
Mots-clés : Concrete structures Cracking Concrete reinforced Finite element method Shell structures Numerical analysis Résumé : A three-dimensional (3D) hypoelastic material model for modeling material properties of cracked reinforced concrete is proposed. Material properties of multidirectionally cracked reinforced concrete are represented by the material properties of intact concrete and a number of uniaxially cracked concrete with their coupling solids. Cracking effects due to multiple nonorthogonal cracks are traced in each uniaxially cracked concrete. Tension softening and aggregate interlock occurring at the crack interface as well as tension stiffening and compression softening initiated in concrete between cracks due to multiple nonorthogonal cracks are all incorporated explicitly. RC panels under in-plane loading and RC slab under pure torsion have been analyzed. The developed 3D hypoelastic material model has been proved to be efficient and effective in modeling the material behaviors of cracked reinforced concrete in shell-type RC structures. The deformational response, the ultimate strength, and failure mode can be captured reasonably well. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282007%29133%3A6%2867 [...]
in Journal of engineering mechanics > Vol. 133 N°6 (Juin 2007) . - pp.688–700.
Titre : Temperature prediction of concrete-filled rectangular hollow sections in fire using green’s function method Type de document : texte imprimé Auteurs : Zhi-Hua Wang, Auteur ; Kang Hai Tan, Auteur Année de publication : 2007 Article en page(s) : pp.688–700. Note générale : Applied mechanics Langues : Anglais (eng) Mots-clés : Heat transfer Greens function Fires Temperature Predictions Résumé : An efficient numerical approach using the Green’s function solutions of transient heat conduction for predictions of thermal response inside a concrete-filled rectangular hollow section subjected to fire is proposed in this paper. Thermal properties of construction materials are assumed to be isotropic and homogeneous. The Green’s function approach adopts different series expansions for small and large time solutions, therefore the desirable convergence properties can be achieved at any range of time by using the time partitioning strategy. A useful analytical relation in terms of step Green’s functions is derived in this paper to incorporate the multidimensional effect, in particular, for Neumann (prescribed flux) boundary conditions. A modified lumped capacitance method, together with an “orthogonal flux” concept, are employed to deal with spatially varying heat flux at the steel–concrete interface, where Duhamel’s theorem is applied in piecewise manner along the interface to incorporate the fire boundary conditions. No spatial discretization is required in the numerical algorithms based on the Green’s function approach. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282007%29133%3A6%2868 [...] [article] Temperature prediction of concrete-filled rectangular hollow sections in fire using green’s function method [texte imprimé] / Zhi-Hua Wang, Auteur ; Kang Hai Tan, Auteur . - 2007 . - pp.688–700.
Applied mechanics
Langues : Anglais (eng)
in Journal of engineering mechanics > Vol. 133 N°6 (Juin 2007) . - pp.688–700.
Mots-clés : Heat transfer Greens function Fires Temperature Predictions Résumé : An efficient numerical approach using the Green’s function solutions of transient heat conduction for predictions of thermal response inside a concrete-filled rectangular hollow section subjected to fire is proposed in this paper. Thermal properties of construction materials are assumed to be isotropic and homogeneous. The Green’s function approach adopts different series expansions for small and large time solutions, therefore the desirable convergence properties can be achieved at any range of time by using the time partitioning strategy. A useful analytical relation in terms of step Green’s functions is derived in this paper to incorporate the multidimensional effect, in particular, for Neumann (prescribed flux) boundary conditions. A modified lumped capacitance method, together with an “orthogonal flux” concept, are employed to deal with spatially varying heat flux at the steel–concrete interface, where Duhamel’s theorem is applied in piecewise manner along the interface to incorporate the fire boundary conditions. No spatial discretization is required in the numerical algorithms based on the Green’s function approach. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282007%29133%3A6%2868 [...]
in Journal of engineering mechanics > Vol. 133 N°6 (Juin 2007) . - pp.701–712.
Titre : Cyclic void growth model to assess ductile fracture initiation in structural steels due to ultra low cycle fatigue Type de document : texte imprimé Auteurs : A. M. Kanvinde, Auteur ; G. G. Deierlein, Auteur Année de publication : 2007 Article en page(s) : pp.701–712. Note générale : Applied mechanics Langues : Anglais (eng) Mots-clés : Voids Steel Fatigue Steel structures Earthquakes Résumé : A new model is proposed to simulate ductile fracture initiation due to large amplitude cyclic straining in structural steels, which is often the governing limit state in steel structures subjected to earthquakes. Termed the cyclic void growth model (CVGM), the proposed technique is an extension to previously published models that simulate ductile fracture caused by void growth and coalescence under monotonic loading. The CVGM aims to capture ultra low cycle fatigue (ductile fracture) behavior, which is characterized by a few (generally, less than 20) reverse loading cycles to large inelastic strain amplitudes (several times the yield strain). The underlying mechanisms of low-cycle fracture involve cyclic void growth, collapse, and distortion, which are distinct from those associated with more conventional fatigue. The CVGM represents these underlying fracture mechanisms through plastic strain and stress triaxiality histories that can be modeled at the material continuum level by finite-element analyses. Development and validation of the CVGM is substantiated by about 100 notched bar tests, with accompanying finite-element analyses, metallurgical tests, and fractographic examinations of seven varieties of structural steels. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282007%29133%3A6%2870 [...] [article] Cyclic void growth model to assess ductile fracture initiation in structural steels due to ultra low cycle fatigue [texte imprimé] / A. M. Kanvinde, Auteur ; G. G. Deierlein, Auteur . - 2007 . - pp.701–712.
Applied mechanics
Langues : Anglais (eng)
in Journal of engineering mechanics > Vol. 133 N°6 (Juin 2007) . - pp.701–712.
Mots-clés : Voids Steel Fatigue Steel structures Earthquakes Résumé : A new model is proposed to simulate ductile fracture initiation due to large amplitude cyclic straining in structural steels, which is often the governing limit state in steel structures subjected to earthquakes. Termed the cyclic void growth model (CVGM), the proposed technique is an extension to previously published models that simulate ductile fracture caused by void growth and coalescence under monotonic loading. The CVGM aims to capture ultra low cycle fatigue (ductile fracture) behavior, which is characterized by a few (generally, less than 20) reverse loading cycles to large inelastic strain amplitudes (several times the yield strain). The underlying mechanisms of low-cycle fracture involve cyclic void growth, collapse, and distortion, which are distinct from those associated with more conventional fatigue. The CVGM represents these underlying fracture mechanisms through plastic strain and stress triaxiality histories that can be modeled at the material continuum level by finite-element analyses. Development and validation of the CVGM is substantiated by about 100 notched bar tests, with accompanying finite-element analyses, metallurgical tests, and fractographic examinations of seven varieties of structural steels. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282007%29133%3A6%2870 [...]
in Journal of engineering mechanics > Vol. 133 N°6 (Juin 2007) . - pp.713–722.
Titre : Dissolution-seepage coupled analysis through formations containing soluble materials Type de document : texte imprimé Auteurs : Arvin M. Farid, Auteur ; Ghasem Habibagahi, Auteur Année de publication : 2007 Article en page(s) : pp.713–722. Note générale : Applied mechanics Langues : Anglais (eng) Mots-clés : Finite elements Differential equation Seepage Porosity Contaminats Résumé : Seepage flow can dissolve particulate soluble materials contained in soil layers and rock formations. The above-mentioned dissolution increases the porosity of the formation and hence seepage flow, which in turn progressively increases the dissolution rate. Due to progressive dissolution, several dams around the world have lost functionality or even failed. Dissolution propagation can be modeled as progress of a solution front, with its progression and resulting excess seepage coupled in the analysis. This is made possible in this paper by simultaneously solving the governing differential equation of seepage and the equation expressing progress of the solution front. The outcome (coupled differential equation) is nonlinear and transient, since both porosity and coefficient of permeability vary with the advancement of the solution front through the medium. The finite-element method is used to solve the resulting nonlinear partial differential equation. Using several examples, influence of material properties and geometry characteristics on the solution front progress and the resulting excess seepage loss is evaluated. Furthermore, effectiveness of different countermeasures (e.g., positive cutoffs and their positions) in dam foundations are studied. Contaminant transport can also be easily modeled and analyzed after applying some modifications into the approach. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282007%29133%3A6%2871 [...] [article] Dissolution-seepage coupled analysis through formations containing soluble materials [texte imprimé] / Arvin M. Farid, Auteur ; Ghasem Habibagahi, Auteur . - 2007 . - pp.713–722.
Applied mechanics
Langues : Anglais (eng)
in Journal of engineering mechanics > Vol. 133 N°6 (Juin 2007) . - pp.713–722.
Mots-clés : Finite elements Differential equation Seepage Porosity Contaminats Résumé : Seepage flow can dissolve particulate soluble materials contained in soil layers and rock formations. The above-mentioned dissolution increases the porosity of the formation and hence seepage flow, which in turn progressively increases the dissolution rate. Due to progressive dissolution, several dams around the world have lost functionality or even failed. Dissolution propagation can be modeled as progress of a solution front, with its progression and resulting excess seepage coupled in the analysis. This is made possible in this paper by simultaneously solving the governing differential equation of seepage and the equation expressing progress of the solution front. The outcome (coupled differential equation) is nonlinear and transient, since both porosity and coefficient of permeability vary with the advancement of the solution front through the medium. The finite-element method is used to solve the resulting nonlinear partial differential equation. Using several examples, influence of material properties and geometry characteristics on the solution front progress and the resulting excess seepage loss is evaluated. Furthermore, effectiveness of different countermeasures (e.g., positive cutoffs and their positions) in dam foundations are studied. Contaminant transport can also be easily modeled and analyzed after applying some modifications into the approach. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282007%29133%3A6%2871 [...]
in Journal of engineering mechanics > Vol. 133 N°6 (Juin 2007) . - pp.723–727.
Titre : Viscoelastic state for the solutions of spherically symmetric viscoelasticity problems Type de document : texte imprimé Auteurs : Necla Kadioglu, Auteur ; Senol Ataoglu, Auteur ; Cuneyt Ozturk, Auteur Année de publication : 2007 Article en page(s) : pp.723–727. Note générale : Applied mechanics Langues : Anglais (eng) Mots-clés : Dynamic response Elasticity Viscoelasticity Transient loads Integral equations Laplace transform Résumé : The solutions of the spherically symmetric, linear, isothermal, and transient viscoelasticity problems via reciprocity theorem have been investigated for a specific material. The integral form of stress–strain relations has been used. The Laplace transform of a viscoelastic state, which is necessary for the integral equation arising as a result of reciprocity theorem, has been derived. This integral equation has been solved by Laplace transform. A sample problem has been solved to test the presented formulation. A numerical application of the analytic solution of this problem has been given. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282007%29133%3A6%2872 [...] [article] Viscoelastic state for the solutions of spherically symmetric viscoelasticity problems [texte imprimé] / Necla Kadioglu, Auteur ; Senol Ataoglu, Auteur ; Cuneyt Ozturk, Auteur . - 2007 . - pp.723–727.
Applied mechanics
Langues : Anglais (eng)
in Journal of engineering mechanics > Vol. 133 N°6 (Juin 2007) . - pp.723–727.
Mots-clés : Dynamic response Elasticity Viscoelasticity Transient loads Integral equations Laplace transform Résumé : The solutions of the spherically symmetric, linear, isothermal, and transient viscoelasticity problems via reciprocity theorem have been investigated for a specific material. The integral form of stress–strain relations has been used. The Laplace transform of a viscoelastic state, which is necessary for the integral equation arising as a result of reciprocity theorem, has been derived. This integral equation has been solved by Laplace transform. A sample problem has been solved to test the presented formulation. A numerical application of the analytic solution of this problem has been given. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282007%29133%3A6%2872 [...]
in Journal of engineering mechanics > Vol. 133 N°6 (Juin 2007) . - pp.728–733.
Titre : Free vibrations of cylindrical storage tanks : finite-element analysis and experiments Type de document : texte imprimé Auteurs : Mariana R. Kruntcheva, Auteur Année de publication : 2007 Article en page(s) : pp.728–733. Note générale : Applied mechanics Langues : Anglais (eng) Mots-clés : Cylindrical tanks Fluid-structure interaction Finite element method Parameters Résumé : This note summarizes a theoretical and experimental study undertaken to provide a deeper understanding of the effect of different parameters on the coupled modal characteristics of circular cylindrical tanks. First, the most common case of clamped-free tanks resting on rigid foundations is investigated by using finite-element (FE) modeling and holographic experiments. A good agreement between experimental and numerical results is a basis to draw a number of conclusions. For both tank geometries investigated, the frequencies for modes of circumferential parameter n=1 (the “beam” modes) are found to be reduced most significantly by the presence of liquid. Very significant dependence of the radial shell mode shapes on the filling ratio is confirmed both by the FE and experimental results. In addition, nonclassical vibration patterns for radial shell modes were extracted numerically and recorded experimentally. Special attention is paid to the pairs of shell modes. Second, the effects of a flexible foundation and axial compression are investigated using holographic interferometry. The modal responses of this shell–liquid system are found to be different from those of the existing theoretical models. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282007%29133%3A6%2872 [...] [article] Free vibrations of cylindrical storage tanks : finite-element analysis and experiments [texte imprimé] / Mariana R. Kruntcheva, Auteur . - 2007 . - pp.728–733.
Applied mechanics
Langues : Anglais (eng)
in Journal of engineering mechanics > Vol. 133 N°6 (Juin 2007) . - pp.728–733.
Mots-clés : Cylindrical tanks Fluid-structure interaction Finite element method Parameters Résumé : This note summarizes a theoretical and experimental study undertaken to provide a deeper understanding of the effect of different parameters on the coupled modal characteristics of circular cylindrical tanks. First, the most common case of clamped-free tanks resting on rigid foundations is investigated by using finite-element (FE) modeling and holographic experiments. A good agreement between experimental and numerical results is a basis to draw a number of conclusions. For both tank geometries investigated, the frequencies for modes of circumferential parameter n=1 (the “beam” modes) are found to be reduced most significantly by the presence of liquid. Very significant dependence of the radial shell mode shapes on the filling ratio is confirmed both by the FE and experimental results. In addition, nonclassical vibration patterns for radial shell modes were extracted numerically and recorded experimentally. Special attention is paid to the pairs of shell modes. Second, the effects of a flexible foundation and axial compression are investigated using holographic interferometry. The modal responses of this shell–liquid system are found to be different from those of the existing theoretical models. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282007%29133%3A6%2872 [...]
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