Dépouillements

Mode II fracture localization in concrete loaded in compression / Jan G. M. Van Mier in Journal of engineering mechanics, Vol. 135 N°1 (Janvier 2009) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 135 N°1 (Janvier 2009) . - pp. 1-8 Titre : Mode II fracture localization in concrete loaded in compression Type de document : texte imprimé Auteurs : Jan G. M. Van Mier, Auteur Article en page(s) : pp. 1-8 Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Cracking  Localization  Axial  compression  Concrete  Deformation. Résumé : As an alternative to a series-coupling model for localization of deformations under uniaxial and confined compression, an approach based on Mode II crack growth is proposed. Such a model appears to be in closer agreement to experimental observations than the presently used series-coupling model, and has the advantage that both material and structural aspects of softening are incorporated directly. Similarities to tensile fracture exist that would make the approach universal. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JENMDT000 [...] [article] Mode II fracture localization in concrete loaded in compression [texte imprimé] / Jan G. M. Van Mier, Auteur . - pp. 1-8. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 135 N°1 (Janvier 2009) . - pp. 1-8 Mots-clés : Cracking  Localization  Axial  compression  Concrete  Deformation. Résumé : As an alternative to a series-coupling model for localization of deformations under uniaxial and confined compression, an approach based on Mode II crack growth is proposed. Such a model appears to be in closer agreement to experimental observations than the presently used series-coupling model, and has the advantage that both material and structural aspects of softening are incorporated directly. Similarities to tensile fracture exist that would make the approach universal. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JENMDT000 [...]

Monitoring corrosion of rebar embedded in mortar using high-frequency guided ultrasonic waves / Benjamin L. Ervin in Journal of engineering mechanics, Vol. 135 N°1 (Janvier 2009) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 135 N°1 (Janvier 2009) . - pp. 9-19 Titre : Monitoring corrosion of rebar embedded in mortar using high-frequency guided ultrasonic waves Type de document : texte imprimé Auteurs : Benjamin L. Ervin, Auteur ; Daniel A. Kuchma, Auteur ; Jennifer T. Bernhard, Auteur Article en page(s) : pp. 9-19 Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Ultrasonic  methods  Wave  propagation  Reinforced  concrete  Corrosion  Damage  Nondestructive  tests  Durability. Résumé : Corrosion of reinforced concrete structures creates serviceability and safety issues, costing millions of dollars for inspection, repair, and rehabilitation. Recent efforts have focused on monitoring corrosion in situ, providing accurate real-time information for decision-making. The goal of this research is the creation of an embeddable ultrasonic sensing network for assessment of reinforcement deterioration. Toward this effort, guided ultrasonic waves were used to monitor reinforced mortar specimens undergoing accelerated uniform and localized corrosion. Longitudinal waves were invoked at higher frequencies (2–9 MHz), where the attenuation is a local minimum. Using a through-transmission configuration, waveforms were sensitive to both forms of corrosion damage. Scattering, mode conversions, and reflections from irregularities at the bar surface from uniform corrosion and the severely tapered cross section from localized corrosion are thought to cause the increase in attenuation. Because localized corrosion did not yield a discontinuity that was nearly perpendicular to the bar axis, incident waves were severely scattered, mode converted, and rapidly attenuated. As evidence, this was the inability of pulse-echo testing to detect reflected waveforms for localized corrosion. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JENMDT000 [...] [article] Monitoring corrosion of rebar embedded in mortar using high-frequency guided ultrasonic waves [texte imprimé] / Benjamin L. Ervin, Auteur ; Daniel A. Kuchma, Auteur ; Jennifer T. Bernhard, Auteur . - pp. 9-19. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 135 N°1 (Janvier 2009) . - pp. 9-19 Mots-clés : Ultrasonic  methods  Wave  propagation  Reinforced  concrete  Corrosion  Damage  Nondestructive  tests  Durability. Résumé : Corrosion of reinforced concrete structures creates serviceability and safety issues, costing millions of dollars for inspection, repair, and rehabilitation. Recent efforts have focused on monitoring corrosion in situ, providing accurate real-time information for decision-making. The goal of this research is the creation of an embeddable ultrasonic sensing network for assessment of reinforcement deterioration. Toward this effort, guided ultrasonic waves were used to monitor reinforced mortar specimens undergoing accelerated uniform and localized corrosion. Longitudinal waves were invoked at higher frequencies (2–9 MHz), where the attenuation is a local minimum. Using a through-transmission configuration, waveforms were sensitive to both forms of corrosion damage. Scattering, mode conversions, and reflections from irregularities at the bar surface from uniform corrosion and the severely tapered cross section from localized corrosion are thought to cause the increase in attenuation. Because localized corrosion did not yield a discontinuity that was nearly perpendicular to the bar axis, incident waves were severely scattered, mode converted, and rapidly attenuated. As evidence, this was the inability of pulse-echo testing to detect reflected waveforms for localized corrosion. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JENMDT000 [...]

Full two-dimensional model for rolling resistance. II / Xiangjun Qiu in Journal of engineering mechanics, Vol. 135 N°1 (Janvier 2009) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 135 N°1 (Janvier 2009) . - pp. 20-30 Titre : Full two-dimensional model for rolling resistance. II : viscoelastic cylinders on rigid ground Type de document : texte imprimé Auteurs : Xiangjun Qiu, Auteur Année de publication : 2009 Article en page(s) : pp. 20-30 Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Viscoelasticity  Tires  Standing  waves  Cylinders  Two-dimensional  models. Résumé : Following the previous paper, “Full two-dimensional model for rolling resistance: Hard cylinder on viscoelastic foundation of finite thickness,” addressing modeling of rigid cylinder rolling against viscoelastic foundation of finite thickness, this paper focuses on the development of a rigorous full two-dimensional semianalytical model for viscoelastic rollers with layered structure rolling against a rigid ground. In this model, the polar coordinate system is used, the solution is expanded into a set of Fourier series corresponding to the angular coordinate, the frequency domain master curves of G[prime] and G[double-prime] characterizing the general viscoelastic properties for a viscoelastic material are used to relate Fourier coefficients, and a special condensed structure model based on the Fourier series is developed to handle viscoelasticity and the rolling contact boundary condition. Examples are given to show the model capabilities to efficiently handle rolling resistance and contact stresses, and capture major characteristics of standing-wave phenomenon, such as sharp rise of rolling resistance, emergence of standing waves and material dynamic softening as the rolling speed approaches a critical value. The methodology may be of interest to industrial roller designers. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JENMDT000 [...] [article] Full two-dimensional model for rolling resistance. II : viscoelastic cylinders on rigid ground [texte imprimé] / Xiangjun Qiu, Auteur . - 2009 . - pp. 20-30. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 135 N°1 (Janvier 2009) . - pp. 20-30 Mots-clés : Viscoelasticity  Tires  Standing  waves  Cylinders  Two-dimensional  models. Résumé : Following the previous paper, “Full two-dimensional model for rolling resistance: Hard cylinder on viscoelastic foundation of finite thickness,” addressing modeling of rigid cylinder rolling against viscoelastic foundation of finite thickness, this paper focuses on the development of a rigorous full two-dimensional semianalytical model for viscoelastic rollers with layered structure rolling against a rigid ground. In this model, the polar coordinate system is used, the solution is expanded into a set of Fourier series corresponding to the angular coordinate, the frequency domain master curves of G[prime] and G[double-prime] characterizing the general viscoelastic properties for a viscoelastic material are used to relate Fourier coefficients, and a special condensed structure model based on the Fourier series is developed to handle viscoelasticity and the rolling contact boundary condition. Examples are given to show the model capabilities to efficiently handle rolling resistance and contact stresses, and capture major characteristics of standing-wave phenomenon, such as sharp rise of rolling resistance, emergence of standing waves and material dynamic softening as the rolling speed approaches a critical value. The methodology may be of interest to industrial roller designers. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JENMDT000 [...]

Performance of a rollover protective structure for a bulldozer / D. P. Thambiratnam in Journal of engineering mechanics, Vol. 135 N°1 (Janvier 2009) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 135 N°1 (Janvier 2009) . - pp. 31-40 Titre : Performance of a rollover protective structure for a bulldozer Type de document : texte imprimé Auteurs : D. P. Thambiratnam, Auteur ; B. J. Clark, Auteur ; N. J. Perera, Auteur Article en page(s) : pp. 31-40 Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Computer  analysis  Model  studies  Energy  absorption  Plastic  hinges  Protective  structures  Vehicles. Résumé : Rollover protective structures (ROPS) are safety devices fitted to heavy vehicles to provide protection to the operator during an accidental rollover. At present, ROPS design standards require full-scale destructive testing, which can be expensive, time consuming, and unsuitable for small companies. More economical analytical methods would require an understanding on postyield behavior and energy absorption capacity of ROPS. With this in mind, this paper treats a bulldozer ROPS using experimental and analytical techniques to generate research information that will enable development of analytical design guidance and enhance safety. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JENMDT000 [...] [article] Performance of a rollover protective structure for a bulldozer [texte imprimé] / D. P. Thambiratnam, Auteur ; B. J. Clark, Auteur ; N. J. Perera, Auteur . - pp. 31-40. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 135 N°1 (Janvier 2009) . - pp. 31-40 Mots-clés : Computer  analysis  Model  studies  Energy  absorption  Plastic  hinges  Protective  structures  Vehicles. Résumé : Rollover protective structures (ROPS) are safety devices fitted to heavy vehicles to provide protection to the operator during an accidental rollover. At present, ROPS design standards require full-scale destructive testing, which can be expensive, time consuming, and unsuitable for small companies. More economical analytical methods would require an understanding on postyield behavior and energy absorption capacity of ROPS. With this in mind, this paper treats a bulldozer ROPS using experimental and analytical techniques to generate research information that will enable development of analytical design guidance and enhance safety. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JENMDT000 [...]

Cable modal parameter identification. I / Wei-Xin Ren in Journal of engineering mechanics, Vol. 135 N°1 (Janvier 2009) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 135 N°1 (Janvier 2009) . - pp. 41-50 Titre : Cable modal parameter identification. I : theory Type de document : texte imprimé Auteurs : Wei-Xin Ren, Auteur ; Wei-Hua Hu, Auteur Année de publication : 2009 Article en page(s) : pp. 41-50 Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Construction  equipment  Cables  Stiffness  Vibration  Parameters  Least  squares  method  Theories. Résumé : Cable modal parameters (natural frequencies and damping ratios) that represent the cable inherent dynamic characteristics play an important role in the construction, vibration control, condition assessment, and long-term health monitoring of cable-supported structures. The existing options to identify cable modal parameters through vibration measurements are somewhat limited. For this purpose, a cable dynamic stiffness based method is presented to effectively identify the cable modal parameters. In the first part of this two-part paper, the cable dynamic stiffness is analytically discussed for a viscously damped, uniform, inclined sagging cable supported at the lower end and subjected to a harmonically varying arbitrary angle displacement excitation in an arbitrary angle at the upper end when the cable is assumed to have a parabolic profile at its position of static equilibrium. Special attention is paid to the physical meaning and significance of every part of the frequency-dependent closed-form cable dynamic stiffness. Comprehensive numerical analyses have been carried out and a simplified cable dynamic stiffness is proposed for the purpose of identifying the cable modal parameters with a good accuracy over a wide range of frequencies. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JENMDT000 [...] [article] Cable modal parameter identification. I : theory [texte imprimé] / Wei-Xin Ren, Auteur ; Wei-Hua Hu, Auteur . - 2009 . - pp. 41-50. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 135 N°1 (Janvier 2009) . - pp. 41-50 Mots-clés : Construction  equipment  Cables  Stiffness  Vibration  Parameters  Least  squares  method  Theories. Résumé : Cable modal parameters (natural frequencies and damping ratios) that represent the cable inherent dynamic characteristics play an important role in the construction, vibration control, condition assessment, and long-term health monitoring of cable-supported structures. The existing options to identify cable modal parameters through vibration measurements are somewhat limited. For this purpose, a cable dynamic stiffness based method is presented to effectively identify the cable modal parameters. In the first part of this two-part paper, the cable dynamic stiffness is analytically discussed for a viscously damped, uniform, inclined sagging cable supported at the lower end and subjected to a harmonically varying arbitrary angle displacement excitation in an arbitrary angle at the upper end when the cable is assumed to have a parabolic profile at its position of static equilibrium. Special attention is paid to the physical meaning and significance of every part of the frequency-dependent closed-form cable dynamic stiffness. Comprehensive numerical analyses have been carried out and a simplified cable dynamic stiffness is proposed for the purpose of identifying the cable modal parameters with a good accuracy over a wide range of frequencies. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JENMDT000 [...]

Cable modal parameter identification. II / Wei-Xin Ren in Journal of engineering mechanics, Vol. 135 N°1 (Janvier 2009) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 135 N°1 (Janvier 2009) . - pp. 51-61 Titre : Cable modal parameter identification. II : modal tests Type de document : texte imprimé Auteurs : Wei-Xin Ren, Auteur ; Wei-Hua Hu, Auteur Année de publication : 2009 Article en page(s) : pp. 51-61 Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Cables  Stiffness  Vibration  Parameters  Least  squares  method. Résumé : The cable dynamic stiffness describes the load–deformation behavior that reflects the cable intrinsic dynamic characteristics. It is defined as a ratio of response to excitation and represents a very similar frequency response property to the frequency response function (FRF). Therefore, by fitting both analytical cable dynamic stiffness and measured frequency response function, the modal parameters of cables can be identified. Based on the simplified cable dynamic stiffness proposed in the first part of the two-part paper, this paper presents a cable dynamic stiffness based procedure to identify the cable modal parameters (natural frequencies and damping ratios) by modal tests. To carry out the curve fitting, a nonlinear least-squares approach is used. A numerical simulation example is first introduced to illustrate the feasibility of the proposed method. Further, a series of cable modal tests are conducted in the laboratory with different cable tensions and the frequency response functions are measured accordingly. A number of issues related to the cable modal tests have been discussed, such as accelerometer arrangement and excitation placement, frequency resolution, windowing, and averaging. It is demonstrated that the cable modal parameters can be effectively identified by using the proposed method through the cable modal tests. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JENMDT000 [...] [article] Cable modal parameter identification. II : modal tests [texte imprimé] / Wei-Xin Ren, Auteur ; Wei-Hua Hu, Auteur . - 2009 . - pp. 51-61. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 135 N°1 (Janvier 2009) . - pp. 51-61 Mots-clés : Cables  Stiffness  Vibration  Parameters  Least  squares  method. Résumé : The cable dynamic stiffness describes the load–deformation behavior that reflects the cable intrinsic dynamic characteristics. It is defined as a ratio of response to excitation and represents a very similar frequency response property to the frequency response function (FRF). Therefore, by fitting both analytical cable dynamic stiffness and measured frequency response function, the modal parameters of cables can be identified. Based on the simplified cable dynamic stiffness proposed in the first part of the two-part paper, this paper presents a cable dynamic stiffness based procedure to identify the cable modal parameters (natural frequencies and damping ratios) by modal tests. To carry out the curve fitting, a nonlinear least-squares approach is used. A numerical simulation example is first introduced to illustrate the feasibility of the proposed method. Further, a series of cable modal tests are conducted in the laboratory with different cable tensions and the frequency response functions are measured accordingly. A number of issues related to the cable modal tests have been discussed, such as accelerometer arrangement and excitation placement, frequency resolution, windowing, and averaging. It is demonstrated that the cable modal parameters can be effectively identified by using the proposed method through the cable modal tests. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JENMDT000 [...]

Isolation system for vibration control of stay cables / Inho Hwang in Journal of engineering mechanics, Vol. 135 N°1 (Janvier 2009) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 135 N°1 (Janvier 2009) . - pp. 62-66 Titre : Isolation system for vibration control of stay cables Type de document : texte imprimé Auteurs : Inho Hwang, Auteur ; Jong Seh Lee, Auteur ; Spencer Jr., B. F., Auteur Article en page(s) : pp. 62-66 Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Bridges  cable-stayed  Isolation  Vibration  Wind  loads. Résumé : Rain-wind induced cable vibration can cause serious problems in cable-stayed bridges. Externally attached dampers have been used to provide an effective means to suppress the vibration of relatively short stay cables. For very long stay cables, however, such damper systems are rendered ineffective, as the dampers need be attached near the end of the cables for aesthetic reasons. This paper investigates a new stay-cable isolation system to mitigate the cable vibration. The proposed isolation system, which consists of a laminated rubber bearing and an internal damper, may be installed inside of the cable anchorage. A simple analytical model of the cable-damper system is developed first based on the taut string representation of the cable. The response of a cable with the proposed isolation system is obtained and then compared to those of the cable with and without an external passive damper. The proposed stay-cable isolation system is shown to perform better than the optimal passive viscous damper, thereby demonstrating its applicability in large cable-stayed bridges. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JENMDT000 [...] [article] Isolation system for vibration control of stay cables [texte imprimé] / Inho Hwang, Auteur ; Jong Seh Lee, Auteur ; Spencer Jr., B. F., Auteur . - pp. 62-66. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 135 N°1 (Janvier 2009) . - pp. 62-66 Mots-clés : Bridges  cable-stayed  Isolation  Vibration  Wind  loads. Résumé : Rain-wind induced cable vibration can cause serious problems in cable-stayed bridges. Externally attached dampers have been used to provide an effective means to suppress the vibration of relatively short stay cables. For very long stay cables, however, such damper systems are rendered ineffective, as the dampers need be attached near the end of the cables for aesthetic reasons. This paper investigates a new stay-cable isolation system to mitigate the cable vibration. The proposed isolation system, which consists of a laminated rubber bearing and an internal damper, may be installed inside of the cable anchorage. A simple analytical model of the cable-damper system is developed first based on the taut string representation of the cable. The response of a cable with the proposed isolation system is obtained and then compared to those of the cable with and without an external passive damper. The proposed stay-cable isolation system is shown to perform better than the optimal passive viscous damper, thereby demonstrating its applicability in large cable-stayed bridges. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JENMDT000 [...]

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