Documents disponibles écrits par cet auteur

Adaptive compensation for detuning in pendulum tuned mass dampers / A. J. Roffel in Journal of structural engineering, Vol. 137 N° 2 (Fevrier 2011) 

Public ISBD [article]  in Journal of structural engineering > Vol. 137 N° 2 (Fevrier 2011) . - pp. 242-251 Titre : Adaptive compensation for detuning in pendulum tuned mass dampers Type de document : texte imprimé Auteurs : A. J. Roffel, Auteur ; R. Lourenco, Auteur ; S. Narasimhan, Auteur Année de publication : 2011 Article en page(s) : pp. 242-251 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Tuned  mass  dampers  Adaptive  TMDs  Passive  vibration  control  Structure  vibration  control Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : Detuning, resulting from deterioration, inadvertent changes to structure properties, and design forecasting, can lead to a significant loss of performance in tuned mass dampers (TMDs). To overcome this issue, an adaptive compensation mechanism for suspended pendulum TMDs is proposed. The adaptive pendulum mass damper is a three-dimensional pendulum, augmented with a tuning frame to adjust its natural frequency, and two adjustable air dampers adjust damping. The adjustments for the natural frequency and damping compensation are achieved using a system of stepper motors and a microcontroller. There are two major components in the proposed methodology: identification and control, one followed by the other, in that order. The identification is carried out using spectral information obtained from the structural acceleration responses. The performance of the adaptive pendulum system is studied via both experiments and simulations. The main contribution of this paper is to develop an effective means of compensation for detuning in TMDs, while retaining the simplicity of passive pendulum TMDs. The proposed methodology allows pendulum TMDs to be tuned in place using relatively simple hardware and algorithms, based on ambient vibration measurements only. DEWEY : 624.17 ISSN : 0733-9445 En ligne : http://ascelibrary.org/sto/resource/1/jsendh/v137/i2/p242_s1?isAuthorized=no [article] Adaptive compensation for detuning in pendulum tuned mass dampers [texte imprimé] / A. J. Roffel, Auteur ; R. Lourenco, Auteur ; S. Narasimhan, Auteur . - 2011 . - pp. 242-251. Génie Civil Langues : Anglais (eng) in Journal of structural engineering > Vol. 137 N° 2 (Fevrier 2011) . - pp. 242-251 Mots-clés : Tuned  mass  dampers  Adaptive  TMDs  Passive  vibration  control  Structure  vibration  control Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : Detuning, resulting from deterioration, inadvertent changes to structure properties, and design forecasting, can lead to a significant loss of performance in tuned mass dampers (TMDs). To overcome this issue, an adaptive compensation mechanism for suspended pendulum TMDs is proposed. The adaptive pendulum mass damper is a three-dimensional pendulum, augmented with a tuning frame to adjust its natural frequency, and two adjustable air dampers adjust damping. The adjustments for the natural frequency and damping compensation are achieved using a system of stepper motors and a microcontroller. There are two major components in the proposed methodology: identification and control, one followed by the other, in that order. The identification is carried out using spectral information obtained from the structural acceleration responses. The performance of the adaptive pendulum system is studied via both experiments and simulations. The main contribution of this paper is to develop an effective means of compensation for detuning in TMDs, while retaining the simplicity of passive pendulum TMDs. The proposed methodology allows pendulum TMDs to be tuned in place using relatively simple hardware and algorithms, based on ambient vibration measurements only. DEWEY : 624.17 ISSN : 0733-9445 En ligne : http://ascelibrary.org/sto/resource/1/jsendh/v137/i2/p242_s1?isAuthorized=no

Modified cross-correlation method for the blind identification of structures / B. Hazra in Journal of engineering mechanics, Vol. 136 N° 7 (Juillet 2010) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 136 N° 7 (Juillet 2010) . - pp. 889-897 Titre : Modified cross-correlation method for the blind identification of structures Type de document : texte imprimé Auteurs : B. Hazra, Auteur ; A. J. Roffel, Auteur ; S. Narasimhan, Auteur Article en page(s) : pp. 889-897 Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Vibration  Monitoring  Identification  Correlation  Signal  processing. Résumé : Recently, blind source separation (BSS) methods have gained significant attention in the area of signal processing. Independent component analysis (ICA) and second-order blind identification (SOBI) are two popular BSS methods that have been applied to modal identification of mechanical and structural systems. Published results by several researchers have shown that ICA performs satisfactorily for systems with very low levels of structural damping, for example, for damping ratios of the order of 1% critical. For practical structural applications with higher levels of damping, methods based on SOBI have shown significant improvement over ICA methods. However, traditional SOBI methods suffer when nonstationary sources are present, such as those that occur during earthquakes and other transient excitations. In this paper, a new technique based on SOBI, called the modified cross-correlation method, is proposed to address these shortcomings. The conditions in which the problem of structural system identification can be posed as a BSS problem is also discussed. The results of simulation described in terms of identified natural frequencies, mode shapes, and damping ratios are presented for the cases of synthetic wind and recorded earthquake excitations. The results of identification show that the proposed method achieves better performance over traditional ICA and SOBI methods. Both experimental and large-scale structural simulation results are included to demonstrate the applicability of the newly proposed method to structural identification problems. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JENMDT000 [...] [article] Modified cross-correlation method for the blind identification of structures [texte imprimé] / B. Hazra, Auteur ; A. J. Roffel, Auteur ; S. Narasimhan, Auteur . - pp. 889-897. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 136 N° 7 (Juillet 2010) . - pp. 889-897 Mots-clés : Vibration  Monitoring  Identification  Correlation  Signal  processing. Résumé : Recently, blind source separation (BSS) methods have gained significant attention in the area of signal processing. Independent component analysis (ICA) and second-order blind identification (SOBI) are two popular BSS methods that have been applied to modal identification of mechanical and structural systems. Published results by several researchers have shown that ICA performs satisfactorily for systems with very low levels of structural damping, for example, for damping ratios of the order of 1% critical. For practical structural applications with higher levels of damping, methods based on SOBI have shown significant improvement over ICA methods. However, traditional SOBI methods suffer when nonstationary sources are present, such as those that occur during earthquakes and other transient excitations. In this paper, a new technique based on SOBI, called the modified cross-correlation method, is proposed to address these shortcomings. The conditions in which the problem of structural system identification can be posed as a BSS problem is also discussed. The results of simulation described in terms of identified natural frequencies, mode shapes, and damping ratios are presented for the cases of synthetic wind and recorded earthquake excitations. The results of identification show that the proposed method achieves better performance over traditional ICA and SOBI methods. Both experimental and large-scale structural simulation results are included to demonstrate the applicability of the newly proposed method to structural identification problems. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JENMDT000 [...]