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Damping of taut-cable systems / Zhenhua Huang in Journal of engineering mechanics, Vol. 137 N° 7 (Juillet 2011) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 137 N° 7 (Juillet 2011) . - pp.512-518 Titre : Damping of taut-cable systems : effects of linear elastic spring support Type de document : texte imprimé Auteurs : Zhenhua Huang, Auteur ; Nicholas P. Jones, Auteur Année de publication : 2011 Article en page(s) : pp.512-518 Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Damping  Cables  Vibration  Cable-stayed  bridges Résumé : The influence of linear elastic support on the damper effectiveness of a cable-damper system was investigated by modeling the system as a taut string, an intermediate damper, and a spring in series. Two types of damper were analyzed in this study: (1) the linear elastic damper; and (2) the friction threshold. An exact formulation for the free vibration of the system was developed for the linear viscous damping system, and a complex eigenfrequencies equation was worked to obtain the explicit solution for the frequency shift. A damping ratio equation for different modes, which depicts the effect of the spring, was developed from the frequency shift. An effective flexibility coefficient was introduced to investigate the effect of different values of support stiffness on the effectiveness of the linear viscous damper. A universal curve family diagram was constructed, which indicated that linear elastic support reduces the effectiveness of the linear viscous damper. The universal curve obtained previously by Main and Jones was a special case of this universal curve family for the case in which the stiffness of the support approached infinity. The equation of maximum force introduced to the spring was also derived and was shown to be positively related to the cable tension force and the cable vibration amplitude at the damper attachment location. The influence of the linear elastic support on a cable-damper system with a friction threshold was also investigated by using the result of the linear viscous damper and the equivalent energy method. The result showed that the linear elastic support also reduces the effectiveness of the friction threshold. An equation showing how to select an optimal friction threshold for a stay cable was also proposed. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.org/emo/resource/1/jenmdt/v137/i7/p512_s1?isAuthorized=no [article] Damping of taut-cable systems : effects of linear elastic spring support [texte imprimé] / Zhenhua Huang, Auteur ; Nicholas P. Jones, Auteur . - 2011 . - pp.512-518. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 137 N° 7 (Juillet 2011) . - pp.512-518 Mots-clés : Damping  Cables  Vibration  Cable-stayed  bridges Résumé : The influence of linear elastic support on the damper effectiveness of a cable-damper system was investigated by modeling the system as a taut string, an intermediate damper, and a spring in series. Two types of damper were analyzed in this study: (1) the linear elastic damper; and (2) the friction threshold. An exact formulation for the free vibration of the system was developed for the linear viscous damping system, and a complex eigenfrequencies equation was worked to obtain the explicit solution for the frequency shift. A damping ratio equation for different modes, which depicts the effect of the spring, was developed from the frequency shift. An effective flexibility coefficient was introduced to investigate the effect of different values of support stiffness on the effectiveness of the linear viscous damper. A universal curve family diagram was constructed, which indicated that linear elastic support reduces the effectiveness of the linear viscous damper. The universal curve obtained previously by Main and Jones was a special case of this universal curve family for the case in which the stiffness of the support approached infinity. The equation of maximum force introduced to the spring was also derived and was shown to be positively related to the cable tension force and the cable vibration amplitude at the damper attachment location. The influence of the linear elastic support on a cable-damper system with a friction threshold was also investigated by using the result of the linear viscous damper and the equivalent energy method. The result showed that the linear elastic support also reduces the effectiveness of the friction threshold. An equation showing how to select an optimal friction threshold for a stay cable was also proposed. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.org/emo/resource/1/jenmdt/v137/i7/p512_s1?isAuthorized=no

Damping of taut-cable systems: / Luca Caracoglia in Journal of engineering mechanics, Vol. 133 N°10 (Octobre 2007) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 133 N°10 (Octobre 2007) Titre : Damping of taut-cable systems: : Two dampers on a single stay Type de document : texte imprimé Auteurs : Luca Caracoglia, Auteur ; Nicholas P. Jones, Auteur Année de publication : 2007 Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Bridges  cable-stayed  Cables  Vibration  Damping Résumé : The mitigation of in-plane stay oscillation in cable-stayed bridges is commonly addressed by placing an external mechanical damper, linear or nonlinear, on each stay or by introducing transverse cross-ties among cables. Although the problem of a cable with a single external damper has found significant attention in the past and different techniques have been proposed for the solution of the free-vibration problem, limitations are related to the fact that the location of the damper is usually very close to the cable end (on the bridge deck side) due to geometric constraints, leading to inherently low modal damping in the fundamental modes. In this paper the installation of more than one damper on an individual stay is considered to overcome such limitations and to increase the overall performance of the system. An existing procedure, based on the linearized taut-string theory, was modified to allow for the presence of multiple external discrete viscous dampers. The case of two devices with arbitrary location has been solved, identifying advantages and disadvantages of the proposed solution. In addition, extensions of the practical “universal curve” and the interpretation thereof are presented. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282007%29133%3A10%281 [...] [article] Damping of taut-cable systems: : Two dampers on a single stay [texte imprimé] / Luca Caracoglia, Auteur ; Nicholas P. Jones, Auteur . - 2007. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 133 N°10 (Octobre 2007) Mots-clés : Bridges  cable-stayed  Cables  Vibration  Damping Résumé : The mitigation of in-plane stay oscillation in cable-stayed bridges is commonly addressed by placing an external mechanical damper, linear or nonlinear, on each stay or by introducing transverse cross-ties among cables. Although the problem of a cable with a single external damper has found significant attention in the past and different techniques have been proposed for the solution of the free-vibration problem, limitations are related to the fact that the location of the damper is usually very close to the cable end (on the bridge deck side) due to geometric constraints, leading to inherently low modal damping in the fundamental modes. In this paper the installation of more than one damper on an individual stay is considered to overcome such limitations and to increase the overall performance of the system. An existing procedure, based on the linearized taut-string theory, was modified to allow for the presence of multiple external discrete viscous dampers. The case of two devices with arbitrary location has been solved, identifying advantages and disadvantages of the proposed solution. In addition, extensions of the practical “universal curve” and the interpretation thereof are presented. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282007%29133%3A10%281 [...]

Vibration of tensioned beams with intermediate damper. I / Joseph A. Main in Journal of engineering mechanics, Vol. 133 N°4 (Avril 2007) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 133 N°4 (Avril 2007) . - pp.369–378. Titre : Vibration of tensioned beams with intermediate damper. I : formulation, influence of damper location Type de document : texte imprimé Auteurs : Joseph A. Main, Auteur ; Nicholas P. Jones, Auteur Année de publication : 2007 Article en page(s) : pp.369–378. Note générale : Applied mechanics Langues : Anglais (eng) Mots-clés : Vibration  Damping  Modal  analysis  Eigenvalues  Beams Résumé : Exact analytical solutions are formulated for free vibrations of tensioned beams with an intermediate viscous damper. The dynamic stiffness method is used in the problem formulation, and characteristic equations are obtained for both clamped and pinned supports. The complex eigenfrequencies form loci in the complex plane that originate at the undamped eigenfrequencies and terminate at the eigenfrequencies of the fully locked system, in which the damper acts as an intermediate pin support. The fully locked eigenfrequencies exhibit “curve veering,” in which adjacent eigenfrequencies approach and then veer apart as the damper passes a node of an undamped mode shape. Consideration of the evolution of the eigenfrequency loci with varying damper location reveals three distinct regimes of behavior, which prevail from the taut-string limit to the case of a beam without tension. The second regime corresponds to damper locations near the first antinode of a given undamped mode shape; in this regime, the loci bend backwards to intersect the imaginary axis, and two distinct nonoscillatory decaying solutions emerge when the damper coefficient exceeds a critical value. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282007%29133%3A4%2836 [...] [article] Vibration of tensioned beams with intermediate damper. I : formulation, influence of damper location [texte imprimé] / Joseph A. Main, Auteur ; Nicholas P. Jones, Auteur . - 2007 . - pp.369–378. Applied mechanics Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 133 N°4 (Avril 2007) . - pp.369–378. Mots-clés : Vibration  Damping  Modal  analysis  Eigenvalues  Beams Résumé : Exact analytical solutions are formulated for free vibrations of tensioned beams with an intermediate viscous damper. The dynamic stiffness method is used in the problem formulation, and characteristic equations are obtained for both clamped and pinned supports. The complex eigenfrequencies form loci in the complex plane that originate at the undamped eigenfrequencies and terminate at the eigenfrequencies of the fully locked system, in which the damper acts as an intermediate pin support. The fully locked eigenfrequencies exhibit “curve veering,” in which adjacent eigenfrequencies approach and then veer apart as the damper passes a node of an undamped mode shape. Consideration of the evolution of the eigenfrequency loci with varying damper location reveals three distinct regimes of behavior, which prevail from the taut-string limit to the case of a beam without tension. The second regime corresponds to damper locations near the first antinode of a given undamped mode shape; in this regime, the loci bend backwards to intersect the imaginary axis, and two distinct nonoscillatory decaying solutions emerge when the damper coefficient exceeds a critical value. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282007%29133%3A4%2836 [...]

Vibration of tensioned beams with intermediate damper. II / Joseph A. Main in Journal of engineering mechanics, Vol. 133 N°4 (Avril 2007) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 133 N°4 (Avril 2007) . - pp.379–388. Titre : Vibration of tensioned beams with intermediate damper. II : damper near a support Type de document : texte imprimé Auteurs : Joseph A. Main, Auteur ; Nicholas P. Jones, Auteur Année de publication : 2007 Article en page(s) : pp.379–388. Note générale : Applied mechanics Langues : Anglais (eng) Mots-clés : Vibration  Damping  Beams  Cables  Bridges  cable-stayed  Optimization Résumé : Analytical solutions are used to investigate the free vibrations of tensioned beams with a viscous damper attached transversely near a support. This problem is of particular relevance for stay-cable vibration suppression, but no restrictions on the level of axial load are introduced, and the results are quite broadly applicable. Characteristic equations for both clamped and pinned supports are rearranged into forms suitable for numerical solution by fixed-point iteration, whereby the complex eigenfrequencies and corresponding damping ratios can be accurately computed within a few iterations. Explicit asymptotic approximations for the complex eigenfrequencies are also obtained, subject to restrictions on the closeness of the eigenfrequencies to their undamped values. These asymptotic approximations are expressed in the same “universal” form identified in previous studies. It is observed that the maximum attainable modal damping ratios and the corresponding optimal values of the damper coefficient can be significantly affected by bending stiffness and by the nature of the support conditions, and a nondimensional parameter grouping is identified that enables an assessment of when bending stiffness should be considered. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282007%29133%3A4%2837 [...] [article] Vibration of tensioned beams with intermediate damper. II : damper near a support [texte imprimé] / Joseph A. Main, Auteur ; Nicholas P. Jones, Auteur . - 2007 . - pp.379–388. Applied mechanics Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 133 N°4 (Avril 2007) . - pp.379–388. Mots-clés : Vibration  Damping  Beams  Cables  Bridges  cable-stayed  Optimization Résumé : Analytical solutions are used to investigate the free vibrations of tensioned beams with a viscous damper attached transversely near a support. This problem is of particular relevance for stay-cable vibration suppression, but no restrictions on the level of axial load are introduced, and the results are quite broadly applicable. Characteristic equations for both clamped and pinned supports are rearranged into forms suitable for numerical solution by fixed-point iteration, whereby the complex eigenfrequencies and corresponding damping ratios can be accurately computed within a few iterations. Explicit asymptotic approximations for the complex eigenfrequencies are also obtained, subject to restrictions on the closeness of the eigenfrequencies to their undamped values. These asymptotic approximations are expressed in the same “universal” form identified in previous studies. It is observed that the maximum attainable modal damping ratios and the corresponding optimal values of the damper coefficient can be significantly affected by bending stiffness and by the nature of the support conditions, and a nondimensional parameter grouping is identified that enables an assessment of when bending stiffness should be considered. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282007%29133%3A4%2837 [...]