Analysis of frequency nonstationarity via continuous wavelet transform in the response of primary-secondary systems / Arunasis Chakraborty in Journal of structural engineering, Vol. 136 N° 12 (Décembre 2010)  

Public ISBD [article]  inJournal of structural engineering > Vol. 136 N° 12 (Décembre 2010) . - pp. 1608-1612 Titre : Analysis of frequency nonstationarity via continuous wavelet transform in the response of primary-secondary systems Type de document : texte imprimé Auteurs : Arunasis Chakraborty, Auteur ; Biswajit Basu, Auteur Année de publication : 2011 Article en page(s) : pp. 1608-1612 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : P-S systems Frequency nonstationarity Dynamic coupling Nonclassical damping Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : An investigation into the frequency nonstationarity in the response of primary-secondary (P-S) systems and the impact it could have in the analysis of such structures has been presented in this note. For this purpose, a torsionally coupled P-S system subjected to nonstationary support motion is considered here. Simulated time history records of relative displacement of the secondary system are used to evaluate the time varying power spectral density functions. This is achieved by using a wavelet-based time-frequency analysis, which shows the temporal variations in the frequency content. The numerical results presented in this study advocate the use of nonstationary analysis of the P-S system for their proper design as conventional methods using cascading approximation may fail to capture this phenomenon, especially in the light of tuning and torsional coupling. System parameters such as mass ratio and radius of gyration are also observed to have a significant impact on the time varying frequency content of the response which is evidenced from the constructed time varying power spectrum. DEWEY : 624.17 ISSN : 0733-9445 En ligne : http://ascelibrary.org/sto/resource/1/jsendh/v136/i12/p1608_s1?isAuthorized=no [article] Analysis of frequency nonstationarity via continuous wavelet transform in the response of primary-secondary systems [texte imprimé] / Arunasis Chakraborty, Auteur ; Biswajit Basu, Auteur . - 2011 . - pp. 1608-1612. Génie Civil Langues : Anglais (eng) in Journal of structural engineering > Vol. 136 N° 12 (Décembre 2010) . - pp. 1608-1612 Mots-clés : P-S systems Frequency nonstationarity Dynamic coupling Nonclassical damping Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : An investigation into the frequency nonstationarity in the response of primary-secondary (P-S) systems and the impact it could have in the analysis of such structures has been presented in this note. For this purpose, a torsionally coupled P-S system subjected to nonstationary support motion is considered here. Simulated time history records of relative displacement of the secondary system are used to evaluate the time varying power spectral density functions. This is achieved by using a wavelet-based time-frequency analysis, which shows the temporal variations in the frequency content. The numerical results presented in this study advocate the use of nonstationary analysis of the P-S system for their proper design as conventional methods using cascading approximation may fail to capture this phenomenon, especially in the light of tuning and torsional coupling. System parameters such as mass ratio and radius of gyration are also observed to have a significant impact on the time varying frequency content of the response which is evidenced from the constructed time varying power spectrum. DEWEY : 624.17 ISSN : 0733-9445 En ligne : http://ascelibrary.org/sto/resource/1/jsendh/v136/i12/p1608_s1?isAuthorized=no

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Nonstationary response analysis of long span bridges under spatially varying differential support otions using continuous wavelet transform / Arunasis Chakraborty in Journal of engineering mechanics, Vol. 134 N°2 (Fevrier 2008)  

Public ISBD [article]  inJournal of engineering mechanics > Vol. 134 N°2 (Fevrier 2008) . - pp.155–162. Titre : Nonstationary response analysis of long span bridges under spatially varying differential support otions using continuous wavelet transform Type de document : texte imprimé Auteurs : Arunasis Chakraborty, Auteur ; Biswajit Basu, Auteur Année de publication : 2008 Article en page(s) : pp.155–162. Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Stationary processes Bridges span Motion Seismic effects Résumé : An input-output relation for the nonstationary response of long-span bridges subjected to random differential support motions is proposed in the present study. The proposed methodology is more general than the existing ones, in the sense that it can evaluate nonstationarity in both the intensity and frequency content of the response statistics for spatially correlated multipoint random excitations. Furthermore, because the input-output relation is established through the transfer functions of dynamic systems, the proposed wavelet-based methodology can easily be used to predict the stochastic response of any structural systems in conjunction with available finite-element software. The input-output formulation is also not restricted to a particular wavelet basis function, since it has been derived by following a general wavelet-based description of input nonstationary processes. The bridge has been modeled as a simply supported beam with multispans in a finite-element framework to obtain the dynamic properties. With a modified form of the Littlewood-Paley (real part of harmonic) wavelet basis function, the support motion has been modeled as a summation of independent random processes in different nonoverlapping frequency bands. At each frequency band, the random process is expressed as a product of a stationary orthogonal process and a deterministic envelope function that depends on the scale. An exponential coherence function is used to model the spatial variation of the ground motion. The response statistics are obtained by using a random vibration formulation in the wavelet domain. The results demonstrate the effects of frequency nonstationarity on the response of a multispan bridge with closely spaced modes and excitation of higher modes locally in time. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282008%29134%3A2%2815 [...] [article] Nonstationary response analysis of long span bridges under spatially varying differential support otions using continuous wavelet transform [texte imprimé] / Arunasis Chakraborty, Auteur ; Biswajit Basu, Auteur . - 2008 . - pp.155–162. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 134 N°2 (Fevrier 2008) . - pp.155–162. Mots-clés : Stationary processes Bridges span Motion Seismic effects Résumé : An input-output relation for the nonstationary response of long-span bridges subjected to random differential support motions is proposed in the present study. The proposed methodology is more general than the existing ones, in the sense that it can evaluate nonstationarity in both the intensity and frequency content of the response statistics for spatially correlated multipoint random excitations. Furthermore, because the input-output relation is established through the transfer functions of dynamic systems, the proposed wavelet-based methodology can easily be used to predict the stochastic response of any structural systems in conjunction with available finite-element software. The input-output formulation is also not restricted to a particular wavelet basis function, since it has been derived by following a general wavelet-based description of input nonstationary processes. The bridge has been modeled as a simply supported beam with multispans in a finite-element framework to obtain the dynamic properties. With a modified form of the Littlewood-Paley (real part of harmonic) wavelet basis function, the support motion has been modeled as a summation of independent random processes in different nonoverlapping frequency bands. At each frequency band, the random process is expressed as a product of a stationary orthogonal process and a deterministic envelope function that depends on the scale. An exponential coherence function is used to model the spatial variation of the ground motion. The response statistics are obtained by using a random vibration formulation in the wavelet domain. The results demonstrate the effects of frequency nonstationarity on the response of a multispan bridge with closely spaced modes and excitation of higher modes locally in time. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282008%29134%3A2%2815 [...]

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