Dépouillements

On the evaluation of seismic response of structures by nonlinear static methods / Bosco, Melina in Earthquake engineering structural dynamics, Vol. 38 N° 13 (Octobre 2009) 

Public ISBD [article]  in Earthquake engineering structural dynamics > Vol. 38 N° 13 (Octobre 2009) . - pp. 1465-1482 Titre : On the evaluation of seismic response of structures by nonlinear static methods Type de document : texte imprimé Auteurs : Bosco, Melina, Auteur ; Ghersi, Aurelio, Auteur ; Marino, Edoardo M., Auteur Article en page(s) : pp. 1465-1482 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Displacement-based  design;  Inelastic  seismic  analysis;  Earthquake-resistant  structures Index. décimale : 624.1 Infrastructures.Ouvrages en terre. Fondations. Tunnels Résumé : In the most recent seismic codes, the assessment of the seismic response of structures may be carried out by comparing the displacement capacity, provided by nonlinear static analysis, with the displacement demand. In many cases the code approach is based on the N2 method proposed by Fajfar, which evaluates the displacement demand by defining, as an intermediate step, a single degree-of-freedom (SDOF) system equivalent to the examined structure. Other codes suggest simpler approaches, which do not require equivalent SDOF systems, but they give slightly different estimation of the seismic displacement demand. The paper points out the differences between the methods and suggests an operative approach that provides the same accuracy as the N2 method without requiring the evaluation of an equivalent SDOF system. A wide parametric investigation allows an accurate comparison of the different methods and demonstrates the effectiveness of the proposed operative approach. ISSN : 0098-8847 En ligne : www.interscience.wiley.com/journal/eqe [article] On the evaluation of seismic response of structures by nonlinear static methods [texte imprimé] / Bosco, Melina, Auteur ; Ghersi, Aurelio, Auteur ; Marino, Edoardo M., Auteur . - pp. 1465-1482. Génie Civil Langues : Anglais (eng) in Earthquake engineering structural dynamics > Vol. 38 N° 13 (Octobre 2009) . - pp. 1465-1482 Mots-clés : Displacement-based  design;  Inelastic  seismic  analysis;  Earthquake-resistant  structures Index. décimale : 624.1 Infrastructures.Ouvrages en terre. Fondations. Tunnels Résumé : In the most recent seismic codes, the assessment of the seismic response of structures may be carried out by comparing the displacement capacity, provided by nonlinear static analysis, with the displacement demand. In many cases the code approach is based on the N2 method proposed by Fajfar, which evaluates the displacement demand by defining, as an intermediate step, a single degree-of-freedom (SDOF) system equivalent to the examined structure. Other codes suggest simpler approaches, which do not require equivalent SDOF systems, but they give slightly different estimation of the seismic displacement demand. The paper points out the differences between the methods and suggests an operative approach that provides the same accuracy as the N2 method without requiring the evaluation of an equivalent SDOF system. A wide parametric investigation allows an accurate comparison of the different methods and demonstrates the effectiveness of the proposed operative approach. ISSN : 0098-8847 En ligne : www.interscience.wiley.com/journal/eqe

Progressive collapse analysis through strength degradation and fracture in the mixed lagrangian formulation / Lavan, O. in Earthquake engineering structural dynamics, Vol. 38 N° 13 (Octobre 2009) 

Public ISBD [article]  in Earthquake engineering structural dynamics > Vol. 38 N° 13 (Octobre 2009) . - pp. 1483-1504 Titre : Progressive collapse analysis through strength degradation and fracture in the mixed lagrangian formulation Type de document : texte imprimé Auteurs : Lavan, O., Auteur ; Sivaselvan, M. V., Auteur ; Reinhorn, A. M., Auteur ; Dargush, G. F. Article en page(s) : pp. 1483-1504 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Nonlinear  structural  dynamics;  fracture;  Deterioration;  Mixed  Lagrangian  Formulation;  Mixed  variational  method Index. décimale : 624.1 Infrastructures.Ouvrages en terre. Fondations. Tunnels Résumé : The dynamic analysis of progressive collapse faces a great number of obstacles that often lead to the collapse of the analysis prior to the actual analysis of collapse. Hence, the Mixed Lagrangian Formulation that has been shown to be very robust was adopted as a framework to accommodate such analysis. By modifying the loading function and the numerical scheme, the capabilities of this framework were extended to account for strength degradation and fracture, while some insight to its behavior is introduced as well. The examples presented show a very robust and stable behavior of the numerical scheme in terms of the time step size required, even in cases where a sudden fracture takes place. ISSN : 0098-8847 En ligne : www.interscience.wiley.com/journal/eqe [article] Progressive collapse analysis through strength degradation and fracture in the mixed lagrangian formulation [texte imprimé] / Lavan, O., Auteur ; Sivaselvan, M. V., Auteur ; Reinhorn, A. M., Auteur ; Dargush, G. F. . - pp. 1483-1504. Génie Civil Langues : Anglais (eng) in Earthquake engineering structural dynamics > Vol. 38 N° 13 (Octobre 2009) . - pp. 1483-1504 Mots-clés : Nonlinear  structural  dynamics;  fracture;  Deterioration;  Mixed  Lagrangian  Formulation;  Mixed  variational  method Index. décimale : 624.1 Infrastructures.Ouvrages en terre. Fondations. Tunnels Résumé : The dynamic analysis of progressive collapse faces a great number of obstacles that often lead to the collapse of the analysis prior to the actual analysis of collapse. Hence, the Mixed Lagrangian Formulation that has been shown to be very robust was adopted as a framework to accommodate such analysis. By modifying the loading function and the numerical scheme, the capabilities of this framework were extended to account for strength degradation and fracture, while some insight to its behavior is introduced as well. The examples presented show a very robust and stable behavior of the numerical scheme in terms of the time step size required, even in cases where a sudden fracture takes place. ISSN : 0098-8847 En ligne : www.interscience.wiley.com/journal/eqe

Vertical vibration isolator having piecewise-constant restoring force / Araki, Yoshikazu in Earthquake engineering structural dynamics, Vol. 38 N° 13 (Octobre 2009) 

Public ISBD [article]  in Earthquake engineering structural dynamics > Vol. 38 N° 13 (Octobre 2009) . - pp. 1505-1523 Titre : Vertical vibration isolator having piecewise-constant restoring force Type de document : texte imprimé Auteurs : Araki, Yoshikazu, Auteur ; Asai, Takehiko, Auteur ; Masui, Takeshi, Auteur Article en page(s) : pp. 1505-1523 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Vertical  seismic  isolation;  Constant-force  spring;  Shaking  table  experiment;  Time  history  analysis Index. décimale : 624.1 Infrastructures.Ouvrages en terre. Fondations. Tunnels Résumé : We present a vertical vibration isolator having a piecewise-constant restoring force, which belongs to a class of passive and nonlinear vibration isolators. In vertical vibration isolation, direct use of low-stiffness elements leads to unacceptably large deformations due to self-weight. To overcome the difficulty, we apply a combination of constant-force springs, each of which sustains a constant load regardless of its stretch. By arranging the constant-force springs, so that the isolator has a piecewise-constant restoring force, we alleviate the problem of the excessive deformation caused by self-weight, provide stability at the static equilibrium state along with the self-centering capability, and realize a large stroke while keeping the mechanism simple and compact. Further, we attempt to limit the response acceleration within a tolerance regardless of the frequency spectrum and the magnitude of earthquake ground motions. We demonstrate the effectiveness of the present isolator through shaking table tests and numerical simulations. ISSN : 0098-8847 En ligne : www.interscience.wiley.com/journal/eqe [article] Vertical vibration isolator having piecewise-constant restoring force [texte imprimé] / Araki, Yoshikazu, Auteur ; Asai, Takehiko, Auteur ; Masui, Takeshi, Auteur . - pp. 1505-1523. Génie Civil Langues : Anglais (eng) in Earthquake engineering structural dynamics > Vol. 38 N° 13 (Octobre 2009) . - pp. 1505-1523 Mots-clés : Vertical  seismic  isolation;  Constant-force  spring;  Shaking  table  experiment;  Time  history  analysis Index. décimale : 624.1 Infrastructures.Ouvrages en terre. Fondations. Tunnels Résumé : We present a vertical vibration isolator having a piecewise-constant restoring force, which belongs to a class of passive and nonlinear vibration isolators. In vertical vibration isolation, direct use of low-stiffness elements leads to unacceptably large deformations due to self-weight. To overcome the difficulty, we apply a combination of constant-force springs, each of which sustains a constant load regardless of its stretch. By arranging the constant-force springs, so that the isolator has a piecewise-constant restoring force, we alleviate the problem of the excessive deformation caused by self-weight, provide stability at the static equilibrium state along with the self-centering capability, and realize a large stroke while keeping the mechanism simple and compact. Further, we attempt to limit the response acceleration within a tolerance regardless of the frequency spectrum and the magnitude of earthquake ground motions. We demonstrate the effectiveness of the present isolator through shaking table tests and numerical simulations. ISSN : 0098-8847 En ligne : www.interscience.wiley.com/journal/eqe

Pounding force assessment in performance-based design of bridges in Earthquake engineering structural dynamics, Vol. 38 N° 13 (Octobre 2009) 

Public ISBD [article]  in Earthquake engineering structural dynamics > Vol. 38 N° 13 (Octobre 2009) . - pp. 1525-1544 Titre : Pounding force assessment in performance-based design of bridges Type de document : texte imprimé Article en page(s) : pp. 1525-1544 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Seismic  performance;  Pounding;  PEER  formula Index. décimale : 624.1 Infrastructures.Ouvrages en terre. Fondations. Tunnels Résumé : Bridges with deck supported on either sliding or elastomeric bearings are very common in mid-seismicity regions. Their main seismic vulnerabilities are related to the pounding of the deck against abutments or between the different deck elements. A simplified model of the longitudinal behavior of those bridges will allow to characterize the reaction forces developed during pounding using the Pacific Earthquake Engineering Research Center framework formula. In order to ensure the general applicability of the results obtained, a large number of system parameter combinations will be considered. The heart of the formula is the identification of suitable intermediate variables. First, the pseudo acceleration spectral value for the fundamental period of the system (Sa(Ts)) will be used as an intensity measure (IM). This IM will result in a very large non-explained variability of the engineering demand parameter. A portion of this variability will be proved to be related to the relative content of high-frequency energy in the input motion. Two vector-valued IMs including a second parameter taking this energy content into account will then be considered. For both of them, a suitable form for the conditional intensity dependence of the response will be obtained. The question of which one to choose will also be analyzed. Finally, additional issues related to the IM will be studied: its applicability to pulse-type records, the validity of scaling records and the sufficiency of the IM. ISSN : 0098-8847 En ligne : www.interscience.wiley.com/journal/eqe [article] Pounding force assessment in performance-based design of bridges [texte imprimé] . - pp. 1525-1544. Génie Civil Langues : Anglais (eng) in Earthquake engineering structural dynamics > Vol. 38 N° 13 (Octobre 2009) . - pp. 1525-1544 Mots-clés : Seismic  performance;  Pounding;  PEER  formula Index. décimale : 624.1 Infrastructures.Ouvrages en terre. Fondations. Tunnels Résumé : Bridges with deck supported on either sliding or elastomeric bearings are very common in mid-seismicity regions. Their main seismic vulnerabilities are related to the pounding of the deck against abutments or between the different deck elements. A simplified model of the longitudinal behavior of those bridges will allow to characterize the reaction forces developed during pounding using the Pacific Earthquake Engineering Research Center framework formula. In order to ensure the general applicability of the results obtained, a large number of system parameter combinations will be considered. The heart of the formula is the identification of suitable intermediate variables. First, the pseudo acceleration spectral value for the fundamental period of the system (Sa(Ts)) will be used as an intensity measure (IM). This IM will result in a very large non-explained variability of the engineering demand parameter. A portion of this variability will be proved to be related to the relative content of high-frequency energy in the input motion. Two vector-valued IMs including a second parameter taking this energy content into account will then be considered. For both of them, a suitable form for the conditional intensity dependence of the response will be obtained. The question of which one to choose will also be analyzed. Finally, additional issues related to the IM will be studied: its applicability to pulse-type records, the validity of scaling records and the sufficiency of the IM. ISSN : 0098-8847 En ligne : www.interscience.wiley.com/journal/eqe

Full operator algorithm for hybrid simulation / Chung-Chan Hung in Earthquake engineering structural dynamics, Vol. 38 N° 13 (Octobre 2009) 

Public ISBD [article]  in Earthquake engineering structural dynamics > Vol. 38 N° 13 (Octobre 2009) . - pp. 1545-1561 Titre : Full operator algorithm for hybrid simulation Type de document : texte imprimé Auteurs : Chung-Chan Hung, Auteur ; Sherif El-Tawil, Auteur Article en page(s) : pp. 1545-1561 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Hybrid  simulation;  Tangent  stiffness;  Corrector  step;  Nonlinear  model;  Dynamics;  OpenSees;  Error  control Index. décimale : 624.1 Infrastructures.Ouvrages en terre. Fondations. Tunnels Résumé : One of the weaknesses of the operator splitting method (OSM) is that its corrector step employs the approximation that incremental forces are linearly related to the tested structure's initial stiffness matrix. This paper presents a new predictor-corrector technique in which the assumptions about the tested structure's response are shifted to the predictor step, which results in an enhancement in overall simulation accuracy, especially for nonlinear structures. Unlike OSM, which splits the displacement and velocity operators into explicit and implicit terms, the new method uses predicted accelerations to compute fully explicit displacement and velocity values in the predictor step. Another advantage of the proposed technique, termed the full operator method (FOM) is that its formulation makes it suitable for both quasi-static and real-time hybrid simulation. The effectiveness of FOM is first evaluated by investigating error propagation in an undamped single degree-of-freedom model. It is shown that the corrector step in FOM is able to significantly suppress aberrant simulation results caused by incorrect estimation of the structure's stiffness matrix. The performance of FOM is demonstrated by exercising two additional models, which exhibit significant inelastic behavior under the prescribed excitation. The simulation results show that the proposed FOM algorithm is capable of producing accurate solutions and that the corrector step is influential in effectively reducing simulation errors. It is also shown that FOM suppresses actuator displacement control errors because of its reliance on measured quantities in the corrector step. ISSN : 0098-8847 En ligne : www.interscience.wiley.com/journal/eqe [article] Full operator algorithm for hybrid simulation [texte imprimé] / Chung-Chan Hung, Auteur ; Sherif El-Tawil, Auteur . - pp. 1545-1561. Génie Civil Langues : Anglais (eng) in Earthquake engineering structural dynamics > Vol. 38 N° 13 (Octobre 2009) . - pp. 1545-1561 Mots-clés : Hybrid  simulation;  Tangent  stiffness;  Corrector  step;  Nonlinear  model;  Dynamics;  OpenSees;  Error  control Index. décimale : 624.1 Infrastructures.Ouvrages en terre. Fondations. Tunnels Résumé : One of the weaknesses of the operator splitting method (OSM) is that its corrector step employs the approximation that incremental forces are linearly related to the tested structure's initial stiffness matrix. This paper presents a new predictor-corrector technique in which the assumptions about the tested structure's response are shifted to the predictor step, which results in an enhancement in overall simulation accuracy, especially for nonlinear structures. Unlike OSM, which splits the displacement and velocity operators into explicit and implicit terms, the new method uses predicted accelerations to compute fully explicit displacement and velocity values in the predictor step. Another advantage of the proposed technique, termed the full operator method (FOM) is that its formulation makes it suitable for both quasi-static and real-time hybrid simulation. The effectiveness of FOM is first evaluated by investigating error propagation in an undamped single degree-of-freedom model. It is shown that the corrector step in FOM is able to significantly suppress aberrant simulation results caused by incorrect estimation of the structure's stiffness matrix. The performance of FOM is demonstrated by exercising two additional models, which exhibit significant inelastic behavior under the prescribed excitation. The simulation results show that the proposed FOM algorithm is capable of producing accurate solutions and that the corrector step is influential in effectively reducing simulation errors. It is also shown that FOM suppresses actuator displacement control errors because of its reliance on measured quantities in the corrector step. ISSN : 0098-8847 En ligne : www.interscience.wiley.com/journal/eqe

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