Dépouillements

Local fracture-induced phenomena in steel moment frames / Janise E. Rodgers in Earthquake engineering structural dynamics, Vol. 38 N°2 (Février 2009) 

Public ISBD [article]  in Earthquake engineering structural dynamics > Vol. 38 N°2 (Février 2009) . - pp. 135-155 Titre : Local fracture-induced phenomena in steel moment frames Type de document : texte imprimé Auteurs : Janise E. Rodgers, Auteur ; Stephen A. Mahin, Auteur Article en page(s) : pp. 135-155 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Steel;  moment  frames;  Fracture;  High  frequency;  Local  effects;  •Transient  response Index. décimale : 624.1 Infrastructures.Ouvrages en terre. Fondations. Tunnels Résumé : Brittle fractures were observed at the welded beam-to-column connections of a number of steel moment frame buildings following the M6.7 1994 Northridge earthquake. Such fractures cause a rapid loss of connection strength and stiffness, as well as a sudden release of the strain energy stored by the connection at the time of fracture. Immediately following the fracture, a number of highly transient phenomena occur locally in the members adjacent to the connection, as well as globally in the structure as a whole. Four significant local phenomena were observed locally during shaking table tests of a one-third scale, two-story, one-bay steel moment frame in which quasi-brittle beam-to-column fractures occurred: (a) change in beam deflected shape; (b) change in moment distribution in adjacent members; (c) generation and propagation of elastic waves; and (d) initiation of dynamic modal response at the member level. Owing to the highly transient nature of these phenomena, they were observed to have second-order effects on overall behavior of the system. In comparison, the reductions in local strength and stiffness caused by the fractures had much more significant effects on system behavior. ISSN : 0098-8847 En ligne : http://www3.interscience.wiley.com/journal/121372392/abstract [article] Local fracture-induced phenomena in steel moment frames [texte imprimé] / Janise E. Rodgers, Auteur ; Stephen A. Mahin, Auteur . - pp. 135-155. Génie Civil Langues : Anglais (eng) in Earthquake engineering structural dynamics > Vol. 38 N°2 (Février 2009) . - pp. 135-155 Mots-clés : Steel;  moment  frames;  Fracture;  High  frequency;  Local  effects;  •Transient  response Index. décimale : 624.1 Infrastructures.Ouvrages en terre. Fondations. Tunnels Résumé : Brittle fractures were observed at the welded beam-to-column connections of a number of steel moment frame buildings following the M6.7 1994 Northridge earthquake. Such fractures cause a rapid loss of connection strength and stiffness, as well as a sudden release of the strain energy stored by the connection at the time of fracture. Immediately following the fracture, a number of highly transient phenomena occur locally in the members adjacent to the connection, as well as globally in the structure as a whole. Four significant local phenomena were observed locally during shaking table tests of a one-third scale, two-story, one-bay steel moment frame in which quasi-brittle beam-to-column fractures occurred: (a) change in beam deflected shape; (b) change in moment distribution in adjacent members; (c) generation and propagation of elastic waves; and (d) initiation of dynamic modal response at the member level. Owing to the highly transient nature of these phenomena, they were observed to have second-order effects on overall behavior of the system. In comparison, the reductions in local strength and stiffness caused by the fractures had much more significant effects on system behavior. ISSN : 0098-8847 En ligne : http://www3.interscience.wiley.com/journal/121372392/abstract

A mechanical model for elastomeric seismic isolation bearings including the influence of axial load / Sachie Yamamoto in Earthquake engineering structural dynamics, Vol. 38 N°2 (Février 2009) 

Public ISBD [article]  in Earthquake engineering structural dynamics > Vol. 38 N°2 (Février 2009) . - pp. 157-180 Titre : A mechanical model for elastomeric seismic isolation bearings including the influence of axial load Type de document : texte imprimé Auteurs : Sachie Yamamoto, Auteur ; Masaru Kikuchi, Auteur ; Masaiki Ueda Article en page(s) : pp. 157-180 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Seismic  isolation;  Elastomeric  isolation  bearing;  Large  deformation;  Axial  force;  Nonlinear  hysteresis  model;  Seismic  response  analysis Index. décimale : 624.1 Infrastructures.Ouvrages en terre. Fondations. Tunnels Résumé : For the purpose of predicting the large-displacement response of seismically isolated buildings, an analytical model for elastomeric isolation bearings is proposed. The model comprises shear and axial springs and a series of axial springs at the top and bottom boundaries. The properties of elastomeric bearings vary with the imposed vertical load. At large shear deformations, elastomeric bearings exhibit stiffening behavior under low axial stress and buckling under high axial stress. These properties depend on the interaction between the shear and axial forces. The proposed model includes interaction between shear and axial forces, nonlinear hysteresis, and dependence on axial stress. To confirm the validity of the model, analyses are performed for actual static loading tests of lead-rubber isolation bearings. The results of analyses using the new model show very good agreement with the experimental results. Seismic response analyses with the new model are also conducted to demonstrate the behavior of isolated buildings under severe earthquake excitations. The results obtained from the analyses with the new model differ in some cases from those given by existing models. ISSN : 0098-8847 En ligne : http://www3.interscience.wiley.com/journal/121387386/abstract [article] A mechanical model for elastomeric seismic isolation bearings including the influence of axial load [texte imprimé] / Sachie Yamamoto, Auteur ; Masaru Kikuchi, Auteur ; Masaiki Ueda . - pp. 157-180. Génie Civil Langues : Anglais (eng) in Earthquake engineering structural dynamics > Vol. 38 N°2 (Février 2009) . - pp. 157-180 Mots-clés : Seismic  isolation;  Elastomeric  isolation  bearing;  Large  deformation;  Axial  force;  Nonlinear  hysteresis  model;  Seismic  response  analysis Index. décimale : 624.1 Infrastructures.Ouvrages en terre. Fondations. Tunnels Résumé : For the purpose of predicting the large-displacement response of seismically isolated buildings, an analytical model for elastomeric isolation bearings is proposed. The model comprises shear and axial springs and a series of axial springs at the top and bottom boundaries. The properties of elastomeric bearings vary with the imposed vertical load. At large shear deformations, elastomeric bearings exhibit stiffening behavior under low axial stress and buckling under high axial stress. These properties depend on the interaction between the shear and axial forces. The proposed model includes interaction between shear and axial forces, nonlinear hysteresis, and dependence on axial stress. To confirm the validity of the model, analyses are performed for actual static loading tests of lead-rubber isolation bearings. The results of analyses using the new model show very good agreement with the experimental results. Seismic response analyses with the new model are also conducted to demonstrate the behavior of isolated buildings under severe earthquake excitations. The results obtained from the analyses with the new model differ in some cases from those given by existing models. ISSN : 0098-8847 En ligne : http://www3.interscience.wiley.com/journal/121387386/abstract

Performance of a guideway seismic isolator with magnetic springs for precision machinery / George C. Yao in Earthquake engineering structural dynamics, Vol. 38 N°2 (Février 2009) 

Public ISBD [article]  in Earthquake engineering structural dynamics > Vol. 38 N°2 (Février 2009) . - pp. 181-203 Titre : Performance of a guideway seismic isolator with magnetic springs for precision machinery Type de document : texte imprimé Auteurs : George C. Yao, Auteur ; Wen-Chun Huang, Auteur Article en page(s) : pp. 181-203 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Magnetic  spring;  Guideway  isolator;  Magnet;  Repulsion;  Precision  machinery  protection Index. décimale : 624.1 Infrastructures.Ouvrages en terre. Fondations. Tunnels Résumé : This paper proposes the use of the nonlinear restoring force in an isolation system to improve the performance of a seismic isolator. Nonlinear magnetic springs applied to guideway sliding isolators (GSI) that protect precision machinery against seismic motion were studied. The magnetic springs use a non-contact magnetic repulsion force to achieve a nonlinear property. A numerical simulation model of the GSI system using step-by-step integration in the time domain was developed. A full-scale shaking table test was performed to verify the accuracy of the numerical model. Simulation and experimental results show that the GSI system with magnetic springs has good performance when subjected to floor vibrations during earthquakes. A parametric analysis of the magnetic springs in the GSI system under seismic motion was theoretically investigated. It was found that sufficient magnetic forces can diminish the system relative displacements. ISSN : 0098-8847 En ligne : http://www3.interscience.wiley.com/journal/121397336/abstract [article] Performance of a guideway seismic isolator with magnetic springs for precision machinery [texte imprimé] / George C. Yao, Auteur ; Wen-Chun Huang, Auteur . - pp. 181-203. Génie Civil Langues : Anglais (eng) in Earthquake engineering structural dynamics > Vol. 38 N°2 (Février 2009) . - pp. 181-203 Mots-clés : Magnetic  spring;  Guideway  isolator;  Magnet;  Repulsion;  Precision  machinery  protection Index. décimale : 624.1 Infrastructures.Ouvrages en terre. Fondations. Tunnels Résumé : This paper proposes the use of the nonlinear restoring force in an isolation system to improve the performance of a seismic isolator. Nonlinear magnetic springs applied to guideway sliding isolators (GSI) that protect precision machinery against seismic motion were studied. The magnetic springs use a non-contact magnetic repulsion force to achieve a nonlinear property. A numerical simulation model of the GSI system using step-by-step integration in the time domain was developed. A full-scale shaking table test was performed to verify the accuracy of the numerical model. Simulation and experimental results show that the GSI system with magnetic springs has good performance when subjected to floor vibrations during earthquakes. A parametric analysis of the magnetic springs in the GSI system under seismic motion was theoretically investigated. It was found that sufficient magnetic forces can diminish the system relative displacements. ISSN : 0098-8847 En ligne : http://www3.interscience.wiley.com/journal/121397336/abstract

Collapse of a nonductile concrete frame: Shaking table tests / Chiun-lin Wu in Earthquake engineering structural dynamics, Vol. 38 N°2 (Février 2009) 

Public ISBD [article]  in Earthquake engineering structural dynamics > Vol. 38 N°2 (Février 2009) . - pp. 205-224 Titre : Collapse of a nonductile concrete frame: Shaking table tests Type de document : texte imprimé Auteurs : Chiun-lin Wu, Auteur Article en page(s) : pp. 205-224 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Shaking  table;  Structural  collapse;  Reinforced  concrete  Columns;  Flexural  failure;  Shear  failure;  Axial  failure Index. décimale : 624.1 Infrastructures.Ouvrages en terre. Fondations. Tunnels Résumé : Post-earthquake reconnaissance has reported the vulnerability of older reinforced concrete (RC) columns lacking details for ductile response. Research was undertaken to investigate the full-range structural hysteretic behavior of older RC columns. A two-dimensional specimen frame, composed of nonductile and ductile columns to allow for load redistribution, was subjected to a unidirectional base motion on a shaking table until global collapse was observed. The test demonstrates two types of column failure, including flexure-shear and pure flexural failure. Test data are compared with various simplified assessment models commonly used by practicing engineers and researchers to identify older buildings that are at high risk of structural collapse during severe earthquake events. Comparison suggests that ASCE/SEI 41-06 produces very conservative estimates on load-deformation relations of flexure-shear columns, while the recently proposed ASCE/SEI 41-06 update imposes significant modifications on the predictive curve, so that improved accuracy has been achieved. ISSN : 0098-8847 En ligne : http://www3.interscience.wiley.com/journal/121461951/abstract [article] Collapse of a nonductile concrete frame: Shaking table tests [texte imprimé] / Chiun-lin Wu, Auteur . - pp. 205-224. Génie Civil Langues : Anglais (eng) in Earthquake engineering structural dynamics > Vol. 38 N°2 (Février 2009) . - pp. 205-224 Mots-clés : Shaking  table;  Structural  collapse;  Reinforced  concrete  Columns;  Flexural  failure;  Shear  failure;  Axial  failure Index. décimale : 624.1 Infrastructures.Ouvrages en terre. Fondations. Tunnels Résumé : Post-earthquake reconnaissance has reported the vulnerability of older reinforced concrete (RC) columns lacking details for ductile response. Research was undertaken to investigate the full-range structural hysteretic behavior of older RC columns. A two-dimensional specimen frame, composed of nonductile and ductile columns to allow for load redistribution, was subjected to a unidirectional base motion on a shaking table until global collapse was observed. The test demonstrates two types of column failure, including flexure-shear and pure flexural failure. Test data are compared with various simplified assessment models commonly used by practicing engineers and researchers to identify older buildings that are at high risk of structural collapse during severe earthquake events. Comparison suggests that ASCE/SEI 41-06 produces very conservative estimates on load-deformation relations of flexure-shear columns, while the recently proposed ASCE/SEI 41-06 update imposes significant modifications on the predictive curve, so that improved accuracy has been achieved. ISSN : 0098-8847 En ligne : http://www3.interscience.wiley.com/journal/121461951/abstract

In-plane strength of unreinforced masonry piers / Chiara Calderini in Earthquake engineering structural dynamics, Vol. 38 N°2 (Février 2009) 

Public ISBD [article]  in Earthquake engineering structural dynamics > Vol. 38 N°2 (Février 2009) . - pp. 243-267 Titre : In-plane strength of unreinforced masonry piers Type de document : texte imprimé Auteurs : Chiara Calderini, Auteur ; Serena Cattari, Auteur ; Sergio Lagomarsino, Auteur Article en page(s) : pp. 243-267 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Masonry;  Pier  strength;  In-plane  behaviour;  Seismic  capacity  ;  Failure  mechanisms;  Simplified  models Index. décimale : 624.1 Infrastructures.Ouvrages en terre. Fondations. Tunnels Résumé : The definition of adequate simplified models to assess the in-plane load-bearing capacity of masonry piers, in terms of both strength and displacement, plays a fundamental role in the seismic verification of masonry buildings. In this paper, a critical review of the most widespread strength criteria present in the literature and codes to interpret the failure modes of piers (rocking, crushing, bed joint sliding or diagonal cracking) are proposed. Models are usually based on an approximate evaluation of the stress state produced by the external forces in a few points/sections and on its assessment with reference to a limit strength domain. The aim of the review is to assess their reliability by discussing the hypotheses, which they are based on (assumed stress states; choice of reference points/sections on which to assess the pier strength; characteristics of the limit strength domain) and to verify the conditions for their proper use in practice, in terms of both stress fields (depending on the geometry of the pier, boundary conditions and applied loads) and types of masonry (i.e. regular brick masonry vs rubble stone masonry). In order to achieve these objectives, parametric nonlinear finite element analyses are performed and different experimental data available in the literature are analysed and compared. ISSN : 0098-8847 En ligne : http://www3.interscience.wiley.com/journal/121502319/abstract [article] In-plane strength of unreinforced masonry piers [texte imprimé] / Chiara Calderini, Auteur ; Serena Cattari, Auteur ; Sergio Lagomarsino, Auteur . - pp. 243-267. Génie Civil Langues : Anglais (eng) in Earthquake engineering structural dynamics > Vol. 38 N°2 (Février 2009) . - pp. 243-267 Mots-clés : Masonry;  Pier  strength;  In-plane  behaviour;  Seismic  capacity  ;  Failure  mechanisms;  Simplified  models Index. décimale : 624.1 Infrastructures.Ouvrages en terre. Fondations. Tunnels Résumé : The definition of adequate simplified models to assess the in-plane load-bearing capacity of masonry piers, in terms of both strength and displacement, plays a fundamental role in the seismic verification of masonry buildings. In this paper, a critical review of the most widespread strength criteria present in the literature and codes to interpret the failure modes of piers (rocking, crushing, bed joint sliding or diagonal cracking) are proposed. Models are usually based on an approximate evaluation of the stress state produced by the external forces in a few points/sections and on its assessment with reference to a limit strength domain. The aim of the review is to assess their reliability by discussing the hypotheses, which they are based on (assumed stress states; choice of reference points/sections on which to assess the pier strength; characteristics of the limit strength domain) and to verify the conditions for their proper use in practice, in terms of both stress fields (depending on the geometry of the pier, boundary conditions and applied loads) and types of masonry (i.e. regular brick masonry vs rubble stone masonry). In order to achieve these objectives, parametric nonlinear finite element analyses are performed and different experimental data available in the literature are analysed and compared. ISSN : 0098-8847 En ligne : http://www3.interscience.wiley.com/journal/121502319/abstract

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