Dépouillements

Simple formulas for the dynamic stiffness of pile groups / Taherzadeh, Reza in Earthquake engineering structural dynamics, Vol. 38 N° 15 (Décembre 2009) 

Public ISBD [article]  in Earthquake engineering structural dynamics > Vol. 38 N° 15 (Décembre 2009) . - pp. 1665-1685 Titre : Simple formulas for the dynamic stiffness of pile groups Type de document : texte imprimé Auteurs : Taherzadeh, Reza, Auteur ; Clouteau, Didier, Auteur ; Cottereau, Régis, Auteur Article en page(s) : pp. 1665-1685 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Soil  impedance  matrix;  Pile  foundation;  Design  formulas;  Lumped-parameter  models;  Hiden  variables  models Index. décimale : 624.1 Infrastructures.Ouvrages en terre. Fondations. Tunnels Résumé : Simple formulas are derived for the dynamic stiffness of pile group foundations subjected to horizontal and rocking dynamic loads. The formulations are based on the construction of a general model of impedance matrices as the condensation of matrices of mass, damping, and stiffness, and on the identification of the values of these matrices on an extensive database of numerical experiments computed using coupled finite element-boundary element models. The formulations obtained can be readily used for the design of both floating piles on homogeneous half-space and end-bearing piles and are applicable for a wide range of mechanical and geometrical parameters of the soil and piles, in particular for large pile groups. For the seismic design of a building, the use of the simple formulas rather than a full computational model is shown to induce little error on the evaluation of the response spectra and time histories. ISSN : 0098-8847 En ligne : www.interscience.wiley.com/journal/eqe [article] Simple formulas for the dynamic stiffness of pile groups [texte imprimé] / Taherzadeh, Reza, Auteur ; Clouteau, Didier, Auteur ; Cottereau, Régis, Auteur . - pp. 1665-1685. Génie Civil Langues : Anglais (eng) in Earthquake engineering structural dynamics > Vol. 38 N° 15 (Décembre 2009) . - pp. 1665-1685 Mots-clés : Soil  impedance  matrix;  Pile  foundation;  Design  formulas;  Lumped-parameter  models;  Hiden  variables  models Index. décimale : 624.1 Infrastructures.Ouvrages en terre. Fondations. Tunnels Résumé : Simple formulas are derived for the dynamic stiffness of pile group foundations subjected to horizontal and rocking dynamic loads. The formulations are based on the construction of a general model of impedance matrices as the condensation of matrices of mass, damping, and stiffness, and on the identification of the values of these matrices on an extensive database of numerical experiments computed using coupled finite element-boundary element models. The formulations obtained can be readily used for the design of both floating piles on homogeneous half-space and end-bearing piles and are applicable for a wide range of mechanical and geometrical parameters of the soil and piles, in particular for large pile groups. For the seismic design of a building, the use of the simple formulas rather than a full computational model is shown to induce little error on the evaluation of the response spectra and time histories. ISSN : 0098-8847 En ligne : www.interscience.wiley.com/journal/eqe

Correlation model for spatially distributed ground-motion intensities / Jayaram, Nirmal in Earthquake engineering structural dynamics, Vol. 38 N° 15 (Décembre 2009) 

Public ISBD [article]  in Earthquake engineering structural dynamics > Vol. 38 N° 15 (Décembre 2009) . - pp. 1687-1707 Titre : Correlation model for spatially distributed ground-motion intensities Type de document : texte imprimé Auteurs : Jayaram, Nirmal, Auteur ; Jack W. Baker, Auteur Article en page(s) : pp. 1687-1707 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Patial  correlation;  Spectral  accelerations;  Coherency;  Risk  assessement;  Infrastructure  systems Index. décimale : 624.1 Infrastructures.Ouvrages en terre. Fondations. Tunnels Résumé : Risk assessment of spatially distributed building portfolios or infrastructure systems requires quantification of the joint occurrence of ground-motion intensities at several sites, during the same earthquake. The ground-motion models that are used for site-specific hazard analysis do not provide information on the spatial correlation between ground-motion intensities, which is required for the joint prediction of intensities at multiple sites. Moreover, researchers who have previously computed these correlations using observed ground-motion recordings differ in their estimates of spatial correlation. In this paper, ground motions observed during seven past earthquakes are used to estimate correlations between spatially distributed spectral accelerations at various spectral periods. Geostatistical tools are used to quantify and express the observed correlations in a standard format. The estimated correlation model is also compared with previously published results, and apparent discrepancies among the previous results are explained. The analysis shows that the spatial correlation reduces with increasing separation between the sites of interest. The rate of decay of correlation typically decreases with increasing spectral acceleration period. At periods longer than 2 s, the correlations were similar for all the earthquake ground motions considered. At shorter periods, however, the correlations were found to be related to the local-site conditions (as indicated by site Vs30 values) at the ground-motion recording stations. The research work also investigates the assumption of isotropy used in developing the spatial correlation models. It is seen using the Northridge and Chi-Chi earthquake time histories that the isotropy assumption is reasonable at both long and short periods. Based on the factors identified as influencing the spatial correlation, a model is developed that can be used to select appropriate correlation estimates for use in practical risk assessment problems. ISSN : 0098-8847 En ligne : www.interscience.wiley.com/journal/eqe [article] Correlation model for spatially distributed ground-motion intensities [texte imprimé] / Jayaram, Nirmal, Auteur ; Jack W. Baker, Auteur . - pp. 1687-1707. Génie Civil Langues : Anglais (eng) in Earthquake engineering structural dynamics > Vol. 38 N° 15 (Décembre 2009) . - pp. 1687-1707 Mots-clés : Patial  correlation;  Spectral  accelerations;  Coherency;  Risk  assessement;  Infrastructure  systems Index. décimale : 624.1 Infrastructures.Ouvrages en terre. Fondations. Tunnels Résumé : Risk assessment of spatially distributed building portfolios or infrastructure systems requires quantification of the joint occurrence of ground-motion intensities at several sites, during the same earthquake. The ground-motion models that are used for site-specific hazard analysis do not provide information on the spatial correlation between ground-motion intensities, which is required for the joint prediction of intensities at multiple sites. Moreover, researchers who have previously computed these correlations using observed ground-motion recordings differ in their estimates of spatial correlation. In this paper, ground motions observed during seven past earthquakes are used to estimate correlations between spatially distributed spectral accelerations at various spectral periods. Geostatistical tools are used to quantify and express the observed correlations in a standard format. The estimated correlation model is also compared with previously published results, and apparent discrepancies among the previous results are explained. The analysis shows that the spatial correlation reduces with increasing separation between the sites of interest. The rate of decay of correlation typically decreases with increasing spectral acceleration period. At periods longer than 2 s, the correlations were similar for all the earthquake ground motions considered. At shorter periods, however, the correlations were found to be related to the local-site conditions (as indicated by site Vs30 values) at the ground-motion recording stations. The research work also investigates the assumption of isotropy used in developing the spatial correlation models. It is seen using the Northridge and Chi-Chi earthquake time histories that the isotropy assumption is reasonable at both long and short periods. Based on the factors identified as influencing the spatial correlation, a model is developed that can be used to select appropriate correlation estimates for use in practical risk assessment problems. ISSN : 0098-8847 En ligne : www.interscience.wiley.com/journal/eqe

Probabilistic estimate of seismic response design values of RC frames / D'Ambrisi, Angelo in Earthquake engineering structural dynamics, Vol. 38 N° 15 (Décembre 2009) 

Public ISBD [article]  in Earthquake engineering structural dynamics > Vol. 38 N° 15 (Décembre 2009) . - pp. 1709-1727 Titre : Probabilistic estimate of seismic response design values of RC frames Type de document : texte imprimé Auteurs : D'Ambrisi, Angelo, Auteur ; Mezzi, Marco, Auteur Article en page(s) : pp. 1709-1727 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Reinforced  concrete  frames;  Nonlinear  seismic  response;  Conservative  design  values;  Probabilistic  estimate Index. décimale : 624.1 Infrastructures.Ouvrages en terre. Fondations. Tunnels Résumé : Probabilistically controlled design values of the nonlinear seismic response of reinforced concrete frames are obtained using a method previously proposed by the authors. The method allows to calculate conservative design values characterized by a predefined non-exceedance probability, using a limited number of spectrum-fitting generated accelerograms. Herein the method is applied to elastic-strain hardening single degree of freedom systems representative of RC framed structures and is then assessed with reference to four reinforced concrete model frames designed according to EC8. The frames are characterized by different natural periods and aspect ratios. The results, compared with those obtained applying current EC8 recommendations, show the effectiveness of the proposed method. EC8 provides for design values of the seismic response of a structure with a nonlinear behavior computed as the mean value of the responses to seven accelerograms or as the maximum value of the responses to three accelerograms. These two criteria lead to design values characterized by very different and uncontrolled non-exceedance probability levels, while the proposed method allows the analyst to directly control the non-exceedance probability level of the calculated design values. ISSN : 0098-8847 En ligne : www.interscience.wiley.com/journal/eqe [article] Probabilistic estimate of seismic response design values of RC frames [texte imprimé] / D'Ambrisi, Angelo, Auteur ; Mezzi, Marco, Auteur . - pp. 1709-1727. Génie Civil Langues : Anglais (eng) in Earthquake engineering structural dynamics > Vol. 38 N° 15 (Décembre 2009) . - pp. 1709-1727 Mots-clés : Reinforced  concrete  frames;  Nonlinear  seismic  response;  Conservative  design  values;  Probabilistic  estimate Index. décimale : 624.1 Infrastructures.Ouvrages en terre. Fondations. Tunnels Résumé : Probabilistically controlled design values of the nonlinear seismic response of reinforced concrete frames are obtained using a method previously proposed by the authors. The method allows to calculate conservative design values characterized by a predefined non-exceedance probability, using a limited number of spectrum-fitting generated accelerograms. Herein the method is applied to elastic-strain hardening single degree of freedom systems representative of RC framed structures and is then assessed with reference to four reinforced concrete model frames designed according to EC8. The frames are characterized by different natural periods and aspect ratios. The results, compared with those obtained applying current EC8 recommendations, show the effectiveness of the proposed method. EC8 provides for design values of the seismic response of a structure with a nonlinear behavior computed as the mean value of the responses to seven accelerograms or as the maximum value of the responses to three accelerograms. These two criteria lead to design values characterized by very different and uncontrolled non-exceedance probability levels, while the proposed method allows the analyst to directly control the non-exceedance probability level of the calculated design values. ISSN : 0098-8847 En ligne : www.interscience.wiley.com/journal/eqe

A new passive rolling-pendulum vibration absorber using a non-axial-symmetrical guide to achieve bidirectional tuning / Matta, Emiliano in Earthquake engineering structural dynamics, Vol. 38 N° 15 (Décembre 2009) 

Public ISBD [article]  in Earthquake engineering structural dynamics > Vol. 38 N° 15 (Décembre 2009) . - pp. 1729-1750 Titre : A new passive rolling-pendulum vibration absorber using a non-axial-symmetrical guide to achieve bidirectional tuning Type de document : texte imprimé Auteurs : Matta, Emiliano, Auteur ; De Stefano, Alessandro, Auteur ; Spencer Jr, Billie F., Auteur Article en page(s) : pp. 1729-1750 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Passive  vibration  control;  Seismic  protection;  Rolling-pendulum  TMD;  Bidirectional  tuning;  Non-holonomic  mechanics;  Non-linearity Index. décimale : 624.1 Infrastructures.Ouvrages en terre. Fondations. Tunnels Résumé : A new, passive, vibroprotective device of the rolling-pendulum tuned mass damper type is presented that, relying on a proper three-dimensional guiding surface, can simultaneously control the response of the supporting structure in two mutually orthogonal horizontal directions. Unlike existing examples of ball vibration absorbers, mounted on spherical recesses and effective for axial-symmetrical structures, the new device is bidirectionally tuneable, by virtue of the optimum shape of the rolling cavity, to both fundamental structural modes, even when the corresponding natural frequencies are different, in such a case recurring to an innovative non-axial-symmetrical rolling guide. Based on Appell's non-holonomic mechanics, a non-linear dynamic model is first derived for the bidirectional absorber mounted on a 1-storey 3-degrees-of-freedom linear structure translating under the effect of both imparted base motion and applied dynamic forces. A laboratory-scaled prototype of the device is then tested to experimentally demonstrate the bidirectional tuning capability and to validate the mathematical model. The design procedure and the seismic performance of the absorber are finally exemplified through numerical simulation. ISSN : 0098-8847 En ligne : www.interscience.wiley.com/journal/eqe [article] A new passive rolling-pendulum vibration absorber using a non-axial-symmetrical guide to achieve bidirectional tuning [texte imprimé] / Matta, Emiliano, Auteur ; De Stefano, Alessandro, Auteur ; Spencer Jr, Billie F., Auteur . - pp. 1729-1750. Génie Civil Langues : Anglais (eng) in Earthquake engineering structural dynamics > Vol. 38 N° 15 (Décembre 2009) . - pp. 1729-1750 Mots-clés : Passive  vibration  control;  Seismic  protection;  Rolling-pendulum  TMD;  Bidirectional  tuning;  Non-holonomic  mechanics;  Non-linearity Index. décimale : 624.1 Infrastructures.Ouvrages en terre. Fondations. Tunnels Résumé : A new, passive, vibroprotective device of the rolling-pendulum tuned mass damper type is presented that, relying on a proper three-dimensional guiding surface, can simultaneously control the response of the supporting structure in two mutually orthogonal horizontal directions. Unlike existing examples of ball vibration absorbers, mounted on spherical recesses and effective for axial-symmetrical structures, the new device is bidirectionally tuneable, by virtue of the optimum shape of the rolling cavity, to both fundamental structural modes, even when the corresponding natural frequencies are different, in such a case recurring to an innovative non-axial-symmetrical rolling guide. Based on Appell's non-holonomic mechanics, a non-linear dynamic model is first derived for the bidirectional absorber mounted on a 1-storey 3-degrees-of-freedom linear structure translating under the effect of both imparted base motion and applied dynamic forces. A laboratory-scaled prototype of the device is then tested to experimentally demonstrate the bidirectional tuning capability and to validate the mathematical model. The design procedure and the seismic performance of the absorber are finally exemplified through numerical simulation. ISSN : 0098-8847 En ligne : www.interscience.wiley.com/journal/eqe

FDE index for goodness-of-fit between measured and calculated response signals / Dragovich, Jeff J. in Earthquake engineering structural dynamics, Vol. 38 N° 15 (Décembre 2009) 

Public ISBD [article]  in Earthquake engineering structural dynamics > Vol. 38 N° 15 (Décembre 2009) . - pp.1751-1758 Titre : FDE index for goodness-of-fit between measured and calculated response signals Type de document : texte imprimé Auteurs : Dragovich, Jeff J., Auteur ; Lepage, Andres, Auteur Article en page(s) : pp.1751-1758 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Model  validation;  Comparison  metrics;  FFT Index. décimale : 624.1 Infrastructures.Ouvrages en terre. Fondations. Tunnels Résumé : A method is presented for determining the goodness-of-fit between measured and calculated structural response signals. The method is termed as the frequency domain error (FDE) index, which is a value between 0 and 1 where zero indicates a perfect correlation. The FDE is calculated from the Fourier spectra of the measured and calculated waveforms, using a relatively simple calculation procedure, readily implemented using standard fast Fourier transform (FFT) libraries. The FDE is demonstrated herein using three different types of problems: simple harmonic waves, a large number of earthquake response simulations, and a set of limited simulations. Along with the FDE concept, effective methods for displaying the results are presented. ISSN : 0098-8847 En ligne : www.interscience.wiley.com/journal/eqe [article] FDE index for goodness-of-fit between measured and calculated response signals [texte imprimé] / Dragovich, Jeff J., Auteur ; Lepage, Andres, Auteur . - pp.1751-1758. Génie Civil Langues : Anglais (eng) in Earthquake engineering structural dynamics > Vol. 38 N° 15 (Décembre 2009) . - pp.1751-1758 Mots-clés : Model  validation;  Comparison  metrics;  FFT Index. décimale : 624.1 Infrastructures.Ouvrages en terre. Fondations. Tunnels Résumé : A method is presented for determining the goodness-of-fit between measured and calculated structural response signals. The method is termed as the frequency domain error (FDE) index, which is a value between 0 and 1 where zero indicates a perfect correlation. The FDE is calculated from the Fourier spectra of the measured and calculated waveforms, using a relatively simple calculation procedure, readily implemented using standard fast Fourier transform (FFT) libraries. The FDE is demonstrated herein using three different types of problems: simple harmonic waves, a large number of earthquake response simulations, and a set of limited simulations. Along with the FDE concept, effective methods for displaying the results are presented. ISSN : 0098-8847 En ligne : www.interscience.wiley.com/journal/eqe

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