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Case studies of damage to tall steel moment-frame buildings in southern California during large San Andreas earthquakes / Krishnan, Swaminathan in Bulletin of the seismological society of America, Vol. 96 N° 4 Part A (Aôut 2006) 

Public ISBD [article]  in Bulletin of the seismological society of America > Vol. 96 N° 4 Part A (Aôut 2006) . - 1523-1537 p. Titre : Case studies of damage to tall steel moment-frame buildings in southern California during large San Andreas earthquakes Titre original : Etudes de cas des dommages aux bâtiments en acier grands d'armature de moment en Californie méridionale pendant de grands tremblements de terre de San Andreas Type de document : texte imprimé Auteurs : Krishnan, Swaminathan, Auteur ; Ji, Chen, Auteur ; Komatitsch, Dimitri, Auteur Article en page(s) : 1523-1537 p. Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Grand  séisme  Bâtiments  Séismologie  Californie  méridionale  Bassin Index. décimale : 551.2 Résumé : On 9 January 1857, a large earthquake of magnitude 7.9 occurred on the San Andreas fault, with rupture initiating at Parkfield in central California and propagating in a southeasterly direction over a distance of more than 360 km. Such a unilateral rupture produces significant directivity toward the San Fernando and Los Angeles basins. Indeed, newspaper reports of sloshing observed in the Los Angeles river point to long-duration (1–2 min) and long-period (2–8 sec) shaking. If such an earthquake were to happen today, it could impose significant seismic demand on present-day tall buildings. Using state-of-the-art computational tools in seismology and structural engineering, validated using data from the 17 January 1994, magnitude 6.7 Northridge earthquake, we determine the damage to an existing and a new 18- story steel moment-frame building in southern California due to ground motion from two hypothetical magnitude 7.9 earthquakes on the San Andreas fault. Our study indicates that serious damage occurs in these buildings at many locations in the region in one of the two scenarios. For a north-to-south rupture scenario, the peak velocity is of the order of 1 m·sec–1 in the Los Angeles basin, including downtown Los Angeles, and 2 m·sec–1 in the San Fernando valley, while the peak displacements are of the order of 1 m and 2 m in the Los Angeles basin and San Fernando valley, respectively. For a south-to-north rupture scenario the peak velocities and displacements are reduced by a factor of roughly 2. 9 janvier 1857, un grand tremblement de terre de la grandeur 7.9 s'est produit sur le défaut de San Andreas, avec la rupture lançant chez Parkfield en Californie centrale et propageant dans une direction de sud-est au-dessus d'une distance de plus de 360 kilomètres. Une rupture si unilatérale produit la directivité significative vers les bassins de San Fernando et de Los Angeles. En effet, rapports de journal de tremper observés dans le point de fleuve de Los Angeles pour désirer ardemment durée (1-2 minutes) et longue secousse de la période (2-8 sec). Si un tel tremblement de terre devaient se produire aujourd'hui, il pourrait imposer une demande séismique significative aux bâtiments grands de nos jours. Utilisant les outils informatiques du dernier cri dans la séismologie et la technologie structurale, validées en utilisant des données à partir de 17 janvier 1994, tremblement de terre de Northridge de la grandeur 6.7, nous déterminons les dommages à exister et un bâtiment en acier d'armature de moment de la nouvelle histoire 18- en Californie méridionale due au mouvement au sol à partir de deux tremblements de terre hypothétiques de la grandeur 7.9 sur le défaut de San Andreas. Notre étude indique que les dommages sérieux se produisent dans ces bâtiments à beaucoup d'endroits dans la région dans un des deux scénarios. Pour un nord au scénario du sud de rupture, la vitesse maximale est de l'ordre de 1 m·sec-1 dans le bassin de Los Angeles, incluant Los Angeles du centre, et 2 m·sec-1 dans la vallée de San Fernando, alors que les déplacements maximaux sont de l'ordre de 1 m et de 2 m en bassin de Los Angeles et vallée de San Fernando, respectivement. Pour un sud au scénario du nord de rupture les vitesses et les déplacements maximaux sont réduits par un facteur approximativement de 2. DEWEY : 551.2 ISSN : 0037-1106 En ligne : krishnan@caltech.edu [article] Case studies of damage to tall steel moment-frame buildings in southern California during large San Andreas earthquakes = Etudes de cas des dommages aux bâtiments en acier grands d'armature de moment en Californie méridionale pendant de grands tremblements de terre de San Andreas [texte imprimé] / Krishnan, Swaminathan, Auteur ; Ji, Chen, Auteur ; Komatitsch, Dimitri, Auteur . - 1523-1537 p. Génie Civil Langues : Anglais (eng) in Bulletin of the seismological society of America > Vol. 96 N° 4 Part A (Aôut 2006) . - 1523-1537 p. Mots-clés : Grand  séisme  Bâtiments  Séismologie  Californie  méridionale  Bassin Index. décimale : 551.2 Résumé : On 9 January 1857, a large earthquake of magnitude 7.9 occurred on the San Andreas fault, with rupture initiating at Parkfield in central California and propagating in a southeasterly direction over a distance of more than 360 km. Such a unilateral rupture produces significant directivity toward the San Fernando and Los Angeles basins. Indeed, newspaper reports of sloshing observed in the Los Angeles river point to long-duration (1–2 min) and long-period (2–8 sec) shaking. If such an earthquake were to happen today, it could impose significant seismic demand on present-day tall buildings. Using state-of-the-art computational tools in seismology and structural engineering, validated using data from the 17 January 1994, magnitude 6.7 Northridge earthquake, we determine the damage to an existing and a new 18- story steel moment-frame building in southern California due to ground motion from two hypothetical magnitude 7.9 earthquakes on the San Andreas fault. Our study indicates that serious damage occurs in these buildings at many locations in the region in one of the two scenarios. For a north-to-south rupture scenario, the peak velocity is of the order of 1 m·sec–1 in the Los Angeles basin, including downtown Los Angeles, and 2 m·sec–1 in the San Fernando valley, while the peak displacements are of the order of 1 m and 2 m in the Los Angeles basin and San Fernando valley, respectively. For a south-to-north rupture scenario the peak velocities and displacements are reduced by a factor of roughly 2. 9 janvier 1857, un grand tremblement de terre de la grandeur 7.9 s'est produit sur le défaut de San Andreas, avec la rupture lançant chez Parkfield en Californie centrale et propageant dans une direction de sud-est au-dessus d'une distance de plus de 360 kilomètres. Une rupture si unilatérale produit la directivité significative vers les bassins de San Fernando et de Los Angeles. En effet, rapports de journal de tremper observés dans le point de fleuve de Los Angeles pour désirer ardemment durée (1-2 minutes) et longue secousse de la période (2-8 sec). Si un tel tremblement de terre devaient se produire aujourd'hui, il pourrait imposer une demande séismique significative aux bâtiments grands de nos jours. Utilisant les outils informatiques du dernier cri dans la séismologie et la technologie structurale, validées en utilisant des données à partir de 17 janvier 1994, tremblement de terre de Northridge de la grandeur 6.7, nous déterminons les dommages à exister et un bâtiment en acier d'armature de moment de la nouvelle histoire 18- en Californie méridionale due au mouvement au sol à partir de deux tremblements de terre hypothétiques de la grandeur 7.9 sur le défaut de San Andreas. Notre étude indique que les dommages sérieux se produisent dans ces bâtiments à beaucoup d'endroits dans la région dans un des deux scénarios. Pour un nord au scénario du sud de rupture, la vitesse maximale est de l'ordre de 1 m·sec-1 dans le bassin de Los Angeles, incluant Los Angeles du centre, et 2 m·sec-1 dans la vallée de San Fernando, alors que les déplacements maximaux sont de l'ordre de 1 m et de 2 m en bassin de Los Angeles et vallée de San Fernando, respectivement. Pour un sud au scénario du nord de rupture les vitesses et les déplacements maximaux sont réduits par un facteur approximativement de 2. DEWEY : 551.2 ISSN : 0037-1106 En ligne : krishnan@caltech.edu

Mechanism of collapse of tall steel moment-frame buildings under earthquake excitation / Krishnan, Swaminathan in Journal of structural engineering, Vol. 138 N° 11 (Novembre 2012) 

Public ISBD [article]  in Journal of structural engineering > Vol. 138 N° 11 (Novembre 2012) . - pp. 1361-1387 Titre : Mechanism of collapse of tall steel moment-frame buildings under earthquake excitation Type de document : texte imprimé Auteurs : Krishnan, Swaminathan, Auteur ; Matthew Muto, Auteur Année de publication : 2013 Article en page(s) : pp. 1361-1387 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Collapse  mechanism  Moment-frame  buildings  Quasi-shear  band  Plastic  analysis  Principle  of  virtual  work  Damage  localization  Tall  buildings  Shear  wave  propagation  Shear  beam  Earthquake  excitation Résumé : The mechanism of collapse of tall steel moment-frame buildings is explored through three-dimensional nonlinear analyses of two 18-story steel moment-frame buildings under earthquake excitation. Both fracture-susceptible and perfect-connection conditions are investigated. Classical energy-balance analysis shows that only long-period excitation imparts energy to tall buildings large enough to cause collapse. Under such long-period motion, the shear-beam analogy alludes to the existence of a characteristic mechanism of collapse or a few preferred mechanisms of collapse for these buildings. Numerical evidence from parametric analyses of the buildings under a suite of idealized sawtooth-like ground-motion time histories, with varying period (T), amplitude (peak ground velocity, PGV), and duration (number of cycles, N), is presented to support this hypothesis. Damage localizes to form a quasi-shear band over a few stories. When the band is destabilized, sidesway collapse is initiated, and gravity takes over. Only one to five collapse mechanisms occur out of a possible 153 mechanisms in either principal direction of the buildings considered. Where two or more preferred mechanisms do exist, they have significant story-overlap, typically separated by just 1 story. It is shown that a simple work-energy relation applied to all possible quasi-shear bands combined with plastic analysis principles can systematically identify all the preferred collapse mechanisms. ISSN : 0733-9445 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29ST.1943-541X.0000573 [article] Mechanism of collapse of tall steel moment-frame buildings under earthquake excitation [texte imprimé] / Krishnan, Swaminathan, Auteur ; Matthew Muto, Auteur . - 2013 . - pp. 1361-1387. Génie Civil Langues : Anglais (eng) in Journal of structural engineering > Vol. 138 N° 11 (Novembre 2012) . - pp. 1361-1387 Mots-clés : Collapse  mechanism  Moment-frame  buildings  Quasi-shear  band  Plastic  analysis  Principle  of  virtual  work  Damage  localization  Tall  buildings  Shear  wave  propagation  Shear  beam  Earthquake  excitation Résumé : The mechanism of collapse of tall steel moment-frame buildings is explored through three-dimensional nonlinear analyses of two 18-story steel moment-frame buildings under earthquake excitation. Both fracture-susceptible and perfect-connection conditions are investigated. Classical energy-balance analysis shows that only long-period excitation imparts energy to tall buildings large enough to cause collapse. Under such long-period motion, the shear-beam analogy alludes to the existence of a characteristic mechanism of collapse or a few preferred mechanisms of collapse for these buildings. Numerical evidence from parametric analyses of the buildings under a suite of idealized sawtooth-like ground-motion time histories, with varying period (T), amplitude (peak ground velocity, PGV), and duration (number of cycles, N), is presented to support this hypothesis. Damage localizes to form a quasi-shear band over a few stories. When the band is destabilized, sidesway collapse is initiated, and gravity takes over. Only one to five collapse mechanisms occur out of a possible 153 mechanisms in either principal direction of the buildings considered. Where two or more preferred mechanisms do exist, they have significant story-overlap, typically separated by just 1 story. It is shown that a simple work-energy relation applied to all possible quasi-shear bands combined with plastic analysis principles can systematically identify all the preferred collapse mechanisms. ISSN : 0733-9445 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29ST.1943-541X.0000573

Modified elastofiber element for steel slender column and brace modeling / Krishnan, Swaminathan in Journal of structural engineering, Vol. 136 N° 11 (Novembre 2010) 

Public ISBD [article]  in Journal of structural engineering > Vol. 136 N° 11 (Novembre 2010) . - pp. 1350-1366 Titre : Modified elastofiber element for steel slender column and brace modeling Type de document : texte imprimé Auteurs : Krishnan, Swaminathan, Auteur Année de publication : 2011 Article en page(s) : pp. 1350-1366 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Elastic  and  inelastic  buckling  Beam-column  modeling  Brace  modeling  Fracture  Instability  Collapse  simulation  Cyclic  tests  on  struts  Plastic  hinge  element  Fiber  element,  Material  and  geometric  nonlinearity Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : An efficient beam element, the modified elastofiber (MEF) element, has been developed to capture the overall features of the elastic and inelastic responses of slender columns and braces under axial cyclic loading without unduly heavy discretization. It consists of three fiber segments, two at the member ends and one at midspan, with two elastic segments sandwiched in between. The segments are demarcated by two exterior nodes and four interior nodes. The fiber segments are divided into 20 fibers in the cross section that run the length of the segment. The fibers exhibit nonlinear axial stress-strain behavior akin to that observed in a standard tension test of a rod in the laboratory, with a linear elastic portion, a yield plateau, and a strain-hardening portion consisting of a segment of an ellipse. All the control points on the stress-strain law are user defined. The elastic buckling of a member is tracked by updating both exterior and interior nodal coordinates at each iteration of a time step and checking force equilibrium in the updated configuration. Inelastic postbuckling response is captured by fiber yielding, fracturing, and/or rupturing in the nonlinear segments. The key features of the element include the ability to model each member using a single element, easy incorporation of geometric imperfection, partial fixity support conditions, member susceptibility to fracture defined in a probabilistic manner, and fiber rupture leading to complete severing of the member. The element is calibrated to accurately predict the Euler critical buckling load of box and I sections with a wide range of slenderness ratios (L/r = 40, 80, 120, 160, and 200) and support conditions (pinned-pinned, pinned-fixed, and fixed-fixed). Elastic postbuckling of the Koiter-Roorda L frame (tubes and I sections) with various member slenderness ratios (L/r = 40, 80, 120, 160, and 200) is simulated and shown to compare well against second-order analytical approximations to the solution even when using a single-MEF element to model each leg of the frame. The inelastic behavior of struts under cyclic loading observed in the experiments of Black et al., Fell et al., and Tremblay et al. is accurately captured by single-MEF-element models. A FRAME3D model (using MEF elements for braces) of a full-scale six-story braced frame structure that was pseudodynamically tested at the Building Research Institute of Japan subjected to the 1978 Miyagi-Ken-Oki earthquake record is analyzed and shown to closely mimic the experimentally observed behavior. DEWEY : 624.17 ISSN : 0733-9445 En ligne : http://ascelibrary.org/sto/resource/1/jsendh/v136/i11/p1350_s1?isAuthorized=no [article] Modified elastofiber element for steel slender column and brace modeling [texte imprimé] / Krishnan, Swaminathan, Auteur . - 2011 . - pp. 1350-1366. Génie Civil Langues : Anglais (eng) in Journal of structural engineering > Vol. 136 N° 11 (Novembre 2010) . - pp. 1350-1366 Mots-clés : Elastic  and  inelastic  buckling  Beam-column  modeling  Brace  modeling  Fracture  Instability  Collapse  simulation  Cyclic  tests  on  struts  Plastic  hinge  element  Fiber  element,  Material  and  geometric  nonlinearity Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : An efficient beam element, the modified elastofiber (MEF) element, has been developed to capture the overall features of the elastic and inelastic responses of slender columns and braces under axial cyclic loading without unduly heavy discretization. It consists of three fiber segments, two at the member ends and one at midspan, with two elastic segments sandwiched in between. The segments are demarcated by two exterior nodes and four interior nodes. The fiber segments are divided into 20 fibers in the cross section that run the length of the segment. The fibers exhibit nonlinear axial stress-strain behavior akin to that observed in a standard tension test of a rod in the laboratory, with a linear elastic portion, a yield plateau, and a strain-hardening portion consisting of a segment of an ellipse. All the control points on the stress-strain law are user defined. The elastic buckling of a member is tracked by updating both exterior and interior nodal coordinates at each iteration of a time step and checking force equilibrium in the updated configuration. Inelastic postbuckling response is captured by fiber yielding, fracturing, and/or rupturing in the nonlinear segments. The key features of the element include the ability to model each member using a single element, easy incorporation of geometric imperfection, partial fixity support conditions, member susceptibility to fracture defined in a probabilistic manner, and fiber rupture leading to complete severing of the member. The element is calibrated to accurately predict the Euler critical buckling load of box and I sections with a wide range of slenderness ratios (L/r = 40, 80, 120, 160, and 200) and support conditions (pinned-pinned, pinned-fixed, and fixed-fixed). Elastic postbuckling of the Koiter-Roorda L frame (tubes and I sections) with various member slenderness ratios (L/r = 40, 80, 120, 160, and 200) is simulated and shown to compare well against second-order analytical approximations to the solution even when using a single-MEF element to model each leg of the frame. The inelastic behavior of struts under cyclic loading observed in the experiments of Black et al., Fell et al., and Tremblay et al. is accurately captured by single-MEF-element models. A FRAME3D model (using MEF elements for braces) of a full-scale six-story braced frame structure that was pseudodynamically tested at the Building Research Institute of Japan subjected to the 1978 Miyagi-Ken-Oki earthquake record is analyzed and shown to closely mimic the experimentally observed behavior. DEWEY : 624.17 ISSN : 0733-9445 En ligne : http://ascelibrary.org/sto/resource/1/jsendh/v136/i11/p1350_s1?isAuthorized=no