Documents disponibles écrits par cet auteur

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 [...]

Underdetermined blind identification of structures by using the modified cross - correlation method / B. Hazra in Journal of engineering mechanics, Vol. 138 N° 4 (Avril 2012) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 138 N° 4 (Avril 2012) . - pp.327-337 Titre : Underdetermined blind identification of structures by using the modified cross - correlation method Type de document : texte imprimé Auteurs : B. Hazra, Auteur ; A. Sadhu, Auteur ; A. J. Roffel, Auteur Année de publication : 2012 Article en page(s) : pp.327-337 Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : BSS,  SOBI,  Modified  cross-correlation  method,  Output-only  modal  identification  System  identification  Blind  identification  Ambient  vibration  monitoring Résumé : The modified cross-correlation (MCC) blind identification method is extended to handle the underdetermined case of structural system identification. The underdetermined case is one in which the number of sensors is less than the number of identifiable modes. The basic framework of the modified cross-correlation method is retained in cases in which multiple covariance matrices constructed from the correlation of the responses are diagonalized. The solution to the underdetermined blind identification consists of two stages: the generation of intrinsic mode functions (IMFs) from the measurements by using empirical mode decomposition (EMD) and the application of the modified cross-correlation method to the decomposed signals. The available measurements are first decomposed into IMFs by using the sifting process of EMD. Subsequently, the IMFs are used as initial estimates for the sources, and the MCC method is implemented in an iterative framework. Initial estimates for the mixing matrix necessary to start the iterative process are selected using assumed shape functions that satisfy the essential boundary conditions. The need for sensor measurements at all the relevant degrees of freedom (DOF) to identify the mode shapes is alleviated in this approach. This is the main advantage of the proposed method. Vibration responses collected from the apron control tower located at the Toronto Pearson International Airport are used for demonstration. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29EM.1943-7889.0000328 [article] Underdetermined blind identification of structures by using the modified cross - correlation method [texte imprimé] / B. Hazra, Auteur ; A. Sadhu, Auteur ; A. J. Roffel, Auteur . - 2012 . - pp.327-337. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 138 N° 4 (Avril 2012) . - pp.327-337 Mots-clés : BSS,  SOBI,  Modified  cross-correlation  method,  Output-only  modal  identification  System  identification  Blind  identification  Ambient  vibration  monitoring Résumé : The modified cross-correlation (MCC) blind identification method is extended to handle the underdetermined case of structural system identification. The underdetermined case is one in which the number of sensors is less than the number of identifiable modes. The basic framework of the modified cross-correlation method is retained in cases in which multiple covariance matrices constructed from the correlation of the responses are diagonalized. The solution to the underdetermined blind identification consists of two stages: the generation of intrinsic mode functions (IMFs) from the measurements by using empirical mode decomposition (EMD) and the application of the modified cross-correlation method to the decomposed signals. The available measurements are first decomposed into IMFs by using the sifting process of EMD. Subsequently, the IMFs are used as initial estimates for the sources, and the MCC method is implemented in an iterative framework. Initial estimates for the mixing matrix necessary to start the iterative process are selected using assumed shape functions that satisfy the essential boundary conditions. The need for sensor measurements at all the relevant degrees of freedom (DOF) to identify the mode shapes is alleviated in this approach. This is the main advantage of the proposed method. Vibration responses collected from the apron control tower located at the Toronto Pearson International Airport are used for demonstration. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29EM.1943-7889.0000328