Documents disponibles écrits par cet auteur

Adaptive Configuration Tuned Mass Damper for Mitigation of Rotational Vibrations / R. Mohammadi-Ghazi in Journal of engineering mechanics, Vol. 138 N° 8 (Août 2012) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 138 N° 8 (Août 2012) . - pp.934–944 Titre : Adaptive Configuration Tuned Mass Damper for Mitigation of Rotational Vibrations Type de document : texte imprimé Auteurs : R. Mohammadi-Ghazi, Auteur ; A. K. Ghorbani-Tanha, Auteur ; M. Rahimian, Auteur Année de publication : 2012 Article en page(s) : pp.934–944 Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Adaptive  configuration  Mass  moment  of  inertia  Semiactive  vibration  absorber  Adaptive  tuned  mass  damper  Variable  stiffness  Transient  vibrations Résumé : An innovative design for an adaptive configuration tuned mass damper (ACTMD) is proposed. An ACTMD is a semiactive dynamic vibration absorber by which the undesirable rotational vibrations of a structure can be greatly suppressed. It can also be used to attenuate translational vibrations that are converted into rotation by means of an appropriate mechanism. Retuning the absorber with the instantaneous excitation frequency is accomplished by changing the configuration of the ACTMD. The device consists of both fixed and moving parts. To readjust the absorber with the new condition, the position of the moving parts should change. As a result, the device’s mass moment of inertia (MMI) alters and the ACTMD adapts to the new condition in real time. However, the device may not cover all frequency bands, because the moving parts cannot be located in all desirable places. After determining the governing equations, the other effects of alternation in the device’s configuration, such as the attenuation-amplification coefficient, are interpreted. Then, the performance of the absorber is evaluated by controlling a transient rotational vibration through numerical simulation. Finally, a sensitivity analysis is carried out to identify a suitable range of MMI for designing an ACTMD. ISSN : 0888-5885 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29EM.1943-7889.0000400 [article] Adaptive Configuration Tuned Mass Damper for Mitigation of Rotational Vibrations [texte imprimé] / R. Mohammadi-Ghazi, Auteur ; A. K. Ghorbani-Tanha, Auteur ; M. Rahimian, Auteur . - 2012 . - pp.934–944. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 138 N° 8 (Août 2012) . - pp.934–944 Mots-clés : Adaptive  configuration  Mass  moment  of  inertia  Semiactive  vibration  absorber  Adaptive  tuned  mass  damper  Variable  stiffness  Transient  vibrations Résumé : An innovative design for an adaptive configuration tuned mass damper (ACTMD) is proposed. An ACTMD is a semiactive dynamic vibration absorber by which the undesirable rotational vibrations of a structure can be greatly suppressed. It can also be used to attenuate translational vibrations that are converted into rotation by means of an appropriate mechanism. Retuning the absorber with the instantaneous excitation frequency is accomplished by changing the configuration of the ACTMD. The device consists of both fixed and moving parts. To readjust the absorber with the new condition, the position of the moving parts should change. As a result, the device’s mass moment of inertia (MMI) alters and the ACTMD adapts to the new condition in real time. However, the device may not cover all frequency bands, because the moving parts cannot be located in all desirable places. After determining the governing equations, the other effects of alternation in the device’s configuration, such as the attenuation-amplification coefficient, are interpreted. Then, the performance of the absorber is evaluated by controlling a transient rotational vibration through numerical simulation. Finally, a sensitivity analysis is carried out to identify a suitable range of MMI for designing an ACTMD. ISSN : 0888-5885 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29EM.1943-7889.0000400

Improved formulation in mixed-based state-space approach for large displacement inelastic analysis of frames / V. Jafari in Journal of engineering mechanics, Vol. 137 N° 3 (Mars 2011) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 137 N° 3 (Mars 2011) . - pp.196-204 Titre : Improved formulation in mixed-based state-space approach for large displacement inelastic analysis of frames Type de document : texte imprimé Auteurs : V. Jafari, Auteur ; M. Rahimian, Auteur ; S. H. Vahdani, Auteur Année de publication : 2011 Article en page(s) : pp.196-204 Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Force-based  method  State-space  approach  Beam-column  element. Résumé : In this research, an enhanced flexibility- (force-) based formulation is developed for a shear deformable beam-column element by using force interpolation functions. The development is derived from Reissner’s exact stress resultant theory and its finite strain field for a Timoshenko frame element. Here, the state-space approach is applied, and the differential-algebraic equation system, consisting of a conservation global system and local constitutive equations, is formed and solved simultaneously. To improve the element’s accuracy, a polynomial-based displacement field approximation is implemented to evaluate the element flexibility matrix. The proposed technique is verified by nonlinear examples, including material and geometric nonlinearities, to examine its precision. It is shown that shear-locking is alleviated by the element; therefore, shear effects can easily be considered. The proposed method is more reliable and accurate than general displacement-based methods and existing force-based formulations. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.org/emo/resource/1/jenmdt/v137/i3/p196_s1?isAuthorized=no [article] Improved formulation in mixed-based state-space approach for large displacement inelastic analysis of frames [texte imprimé] / V. Jafari, Auteur ; M. Rahimian, Auteur ; S. H. Vahdani, Auteur . - 2011 . - pp.196-204. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 137 N° 3 (Mars 2011) . - pp.196-204 Mots-clés : Force-based  method  State-space  approach  Beam-column  element. Résumé : In this research, an enhanced flexibility- (force-) based formulation is developed for a shear deformable beam-column element by using force interpolation functions. The development is derived from Reissner’s exact stress resultant theory and its finite strain field for a Timoshenko frame element. Here, the state-space approach is applied, and the differential-algebraic equation system, consisting of a conservation global system and local constitutive equations, is formed and solved simultaneously. To improve the element’s accuracy, a polynomial-based displacement field approximation is implemented to evaluate the element flexibility matrix. The proposed technique is verified by nonlinear examples, including material and geometric nonlinearities, to examine its precision. It is shown that shear-locking is alleviated by the element; therefore, shear effects can easily be considered. The proposed method is more reliable and accurate than general displacement-based methods and existing force-based formulations. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.org/emo/resource/1/jenmdt/v137/i3/p196_s1?isAuthorized=no

A novel semiactive variable stiffness device and Its application in a new semiactive tuned vibration absorber / A. K. Ghorbani-Tanha in Journal of engineering mechanics, Vol. 137 N° 6 (Juin 2011) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 137 N° 6 (Juin 2011) . - pp.390-399 Titre : A novel semiactive variable stiffness device and Its application in a new semiactive tuned vibration absorber Type de document : texte imprimé Auteurs : A. K. Ghorbani-Tanha, Auteur ; M. Rahimian, Auteur ; A. Noorzad, Auteur Année de publication : 2011 Article en page(s) : pp.390-399 Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Variable  stiffness  Semiactive  tuned  vibration  absorber  Vibration  control  Adjustable  stiffness  Adaptive  passive  Transient  response Résumé : An innovative design for a semiactive variable stiffness (SAVS) device is presented in this paper. This beamlike device is capable of altering its stiffness in a smooth manner between minimum and maximum levels by using the variations of moment of inertia of an area as it rotates around a normal axis passing through its centroid. Analytical expressions for the stiffness of the proposed device have been derived. As an application of the SAVS device in engineering, a semiactive tuned vibration absorber (SATVA) is developed that is capable of real-time retuning and operates effectively in broadband frequency excitations. A single-degree-of-freedom (SDOF) system coupled with the SATVA is considered. The excitation force is assumed to arise from a rotating unbalance whose frequency varies with a constant acceleration and then reaches a steady-state operating condition. The absorber stiffness is varied to tune the absorber’s natural frequency to the forcing frequency in real time. The effectiveness of SATVA is evaluated by comparing the system’s responses with those of the system with passive vibration absorber. The results show the salient features of the proposed SATVA in transient response reduction compared with the traditional passive vibration absorber. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.org/emo/resource/1/jenmdt/v137/i6/p390_s1?isAuthorized=no [article] A novel semiactive variable stiffness device and Its application in a new semiactive tuned vibration absorber [texte imprimé] / A. K. Ghorbani-Tanha, Auteur ; M. Rahimian, Auteur ; A. Noorzad, Auteur . - 2011 . - pp.390-399. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 137 N° 6 (Juin 2011) . - pp.390-399 Mots-clés : Variable  stiffness  Semiactive  tuned  vibration  absorber  Vibration  control  Adjustable  stiffness  Adaptive  passive  Transient  response Résumé : An innovative design for a semiactive variable stiffness (SAVS) device is presented in this paper. This beamlike device is capable of altering its stiffness in a smooth manner between minimum and maximum levels by using the variations of moment of inertia of an area as it rotates around a normal axis passing through its centroid. Analytical expressions for the stiffness of the proposed device have been derived. As an application of the SAVS device in engineering, a semiactive tuned vibration absorber (SATVA) is developed that is capable of real-time retuning and operates effectively in broadband frequency excitations. A single-degree-of-freedom (SDOF) system coupled with the SATVA is considered. The excitation force is assumed to arise from a rotating unbalance whose frequency varies with a constant acceleration and then reaches a steady-state operating condition. The absorber stiffness is varied to tune the absorber’s natural frequency to the forcing frequency in real time. The effectiveness of SATVA is evaluated by comparing the system’s responses with those of the system with passive vibration absorber. The results show the salient features of the proposed SATVA in transient response reduction compared with the traditional passive vibration absorber. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.org/emo/resource/1/jenmdt/v137/i6/p390_s1?isAuthorized=no