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Accounting for ground-motion spectral shape characteristics in structural collapse assessment through an adjustment for epsilon / Curt B. Haselton in Journal of structural engineering, Vol. 137 N° 3 (Mars 2011) 

Public ISBD [article]  in Journal of structural engineering > Vol. 137 N° 3 (Mars 2011) . - pp. 332-344 Titre : Accounting for ground-motion spectral shape characteristics in structural collapse assessment through an adjustment for epsilon Type de document : texte imprimé Auteurs : Curt B. Haselton, Auteur ; Jack W. Baker, Auteur ; Abbie B. Liel, Auteur Année de publication : 2011 Article en page(s) : pp. 332-344 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Ground  motions  Spectral  shape  Epsilon  Collapse  assessment  Performance  assessment  ATC-63  FEMA  P695 Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : One of the challenges of assessing structural collapse performance is the appropriate selection of ground motions for use in the nonlinear dynamic collapse simulation. The ground motions should represent characteristics of extreme ground motions that exceed the ground-motion intensities considered in the original building design. For modern buildings in the western United States, ground motions that cause collapse are expected to be rare high-intensity motions associated with a large magnitude earthquake. Recent research has shown that rare high-intensity ground motions have a peaked spectral shape that should be considered in ground-motion selection and scaling. One method to account for this spectral shape effect is through the selection of a set of ground motions that is specific to the building’s fundamental period and the site hazard characteristics. This selection presents a significant challenge when assessing the collapse capacity of a large number of buildings or for developing systematic procedures because it implies the need to assemble specific ground-motion sets for each building. This paper proposes an alternative method, whereby a general set of far-field ground motions is used for collapse simulation, and the resulting collapse capacity is adjusted to account for the spectral shape effects that are not reflected in the ground-motion selection. The simplified method is compared with the more direct record selection strategy, and results of the two approaches show good agreement. DEWEY : 624.17 ISSN : 0733-9445 En ligne : http://ascelibrary.org/sto/resource/1/jsendh/v137/i3/p332_s1?isAuthorized=no [article] Accounting for ground-motion spectral shape characteristics in structural collapse assessment through an adjustment for epsilon [texte imprimé] / Curt B. Haselton, Auteur ; Jack W. Baker, Auteur ; Abbie B. Liel, Auteur . - 2011 . - pp. 332-344. Génie Civil Langues : Anglais (eng) in Journal of structural engineering > Vol. 137 N° 3 (Mars 2011) . - pp. 332-344 Mots-clés : Ground  motions  Spectral  shape  Epsilon  Collapse  assessment  Performance  assessment  ATC-63  FEMA  P695 Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : One of the challenges of assessing structural collapse performance is the appropriate selection of ground motions for use in the nonlinear dynamic collapse simulation. The ground motions should represent characteristics of extreme ground motions that exceed the ground-motion intensities considered in the original building design. For modern buildings in the western United States, ground motions that cause collapse are expected to be rare high-intensity motions associated with a large magnitude earthquake. Recent research has shown that rare high-intensity ground motions have a peaked spectral shape that should be considered in ground-motion selection and scaling. One method to account for this spectral shape effect is through the selection of a set of ground motions that is specific to the building’s fundamental period and the site hazard characteristics. This selection presents a significant challenge when assessing the collapse capacity of a large number of buildings or for developing systematic procedures because it implies the need to assemble specific ground-motion sets for each building. This paper proposes an alternative method, whereby a general set of far-field ground motions is used for collapse simulation, and the resulting collapse capacity is adjusted to account for the spectral shape effects that are not reflected in the ground-motion selection. The simplified method is compared with the more direct record selection strategy, and results of the two approaches show good agreement. DEWEY : 624.17 ISSN : 0733-9445 En ligne : http://ascelibrary.org/sto/resource/1/jsendh/v137/i3/p332_s1?isAuthorized=no

Seismic collapse safety of reinforced concrete buildings. I, Assessment of ductile moment frames / Curt B. Haselton in Journal of structural engineering, Vol. 137 N° 4 (Avril 2011) 

Public ISBD [article]  in Journal of structural engineering > Vol. 137 N° 4 (Avril 2011) . - pp. 481-491 Titre : Seismic collapse safety of reinforced concrete buildings. I, Assessment of ductile moment frames Type de document : texte imprimé Auteurs : Curt B. Haselton, Auteur ; Abbie B. Liel, Auteur ; Gregory G. Deierlein, Auteur Année de publication : 2011 Article en page(s) : pp. 481-491 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Collapse  Earthquake  engineerin  Seismic  effects  Reinforced  concrete  structures  Structural  reliability Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : This study applies nonlinear dynamic analyses to assess the risk of collapse of RC special moment-frame (SMF) buildings to quantify the seismic safety implied by modern building codes. Thirty archetypical RC SMF buildings, ranging in height from 1 to 20 stories, are designed according to ASCE 7-02 and ACI 318-05 for a high-seismic region. The results of performance-based seismic assessments show that, on average, these buildings have an 11% probability of collapse under ground motion intensities with a 2% probability of exceedance in 50 years. The average mean annual rate of collapse of 3.1×10-4 collapses per year corresponds to an average of 1.5% probability of collapse in 50 years. The study further examines the influence of specific design provisions on collapse safety. In particular, changes to the minimum seismic base shear requirement between 2002 and 2005 editions of ASCE 7 and variations in ACI 318 strong-column weak-beam (SCWB) design requirements are investigated. The study finds that the reduction in the minimum base shear, introduced in ASCE 7-05 and subsequently rescinded, dramatically increases the collapse risk of tall (long-period) frame buildings in high-seismic regions. An investigation of the SCWB requirements shows that the current ACI 318 provisions delay, but do not prevent, column yielding and the formation of story collapse mechanisms. An increase in the SCWB ratio above 6/5 (1.2) does not significantly improve performance of low-rise frame buildings but may reduce collapse risk for midrise and taller buildings. This study of modern RC buildings is contrasted with the collapse safety of older (nonductile) RC moment-frame buildings in the companion paper. DEWEY : 624.17 ISSN : 0733-9445 En ligne : http://ascelibrary.org/sto/resource/1/jsendh/v137/i4/p481_s1?isAuthorized=no [article] Seismic collapse safety of reinforced concrete buildings. I, Assessment of ductile moment frames [texte imprimé] / Curt B. Haselton, Auteur ; Abbie B. Liel, Auteur ; Gregory G. Deierlein, Auteur . - 2011 . - pp. 481-491. Génie Civil Langues : Anglais (eng) in Journal of structural engineering > Vol. 137 N° 4 (Avril 2011) . - pp. 481-491 Mots-clés : Collapse  Earthquake  engineerin  Seismic  effects  Reinforced  concrete  structures  Structural  reliability Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : This study applies nonlinear dynamic analyses to assess the risk of collapse of RC special moment-frame (SMF) buildings to quantify the seismic safety implied by modern building codes. Thirty archetypical RC SMF buildings, ranging in height from 1 to 20 stories, are designed according to ASCE 7-02 and ACI 318-05 for a high-seismic region. The results of performance-based seismic assessments show that, on average, these buildings have an 11% probability of collapse under ground motion intensities with a 2% probability of exceedance in 50 years. The average mean annual rate of collapse of 3.1×10-4 collapses per year corresponds to an average of 1.5% probability of collapse in 50 years. The study further examines the influence of specific design provisions on collapse safety. In particular, changes to the minimum seismic base shear requirement between 2002 and 2005 editions of ASCE 7 and variations in ACI 318 strong-column weak-beam (SCWB) design requirements are investigated. The study finds that the reduction in the minimum base shear, introduced in ASCE 7-05 and subsequently rescinded, dramatically increases the collapse risk of tall (long-period) frame buildings in high-seismic regions. An investigation of the SCWB requirements shows that the current ACI 318 provisions delay, but do not prevent, column yielding and the formation of story collapse mechanisms. An increase in the SCWB ratio above 6/5 (1.2) does not significantly improve performance of low-rise frame buildings but may reduce collapse risk for midrise and taller buildings. This study of modern RC buildings is contrasted with the collapse safety of older (nonductile) RC moment-frame buildings in the companion paper. DEWEY : 624.17 ISSN : 0733-9445 En ligne : http://ascelibrary.org/sto/resource/1/jsendh/v137/i4/p481_s1?isAuthorized=no

Seismic collapse safety of reinforced concrete buildings. II, Comparative assessment of nonductile and ductile moment frames / Abbie B. Liel in Journal of structural engineering, Vol. 137 N° 4 (Avril 2011) 

Public ISBD [article]  in Journal of structural engineering > Vol. 137 N° 4 (Avril 2011) . - pp. 492-502 Titre : Seismic collapse safety of reinforced concrete buildings. II, Comparative assessment of nonductile and ductile moment frames Type de document : texte imprimé Auteurs : Abbie B. Liel, Auteur ; Curt B. Haselton, Auteur ; Gregory G. Deierlein, Auteur Année de publication : 2011 Article en page(s) : pp. 492-502 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Collapse  Earthquake  engineering  Structural  reliability  Reinforced  concrete  structures  Buildings  Commercial  Seismic  effects Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : This study is the second of two companion papers to examine the seismic collapse safety of reinforced concrete frame buildings, and examines nonductile moment frames that are representative of those built before the mid-1970s in California. The probabilistic assessment relies on nonlinear dynamic simulation of structural response to calculate the collapse risk, accounting for uncertainties in ground-motion characteristics and structural modeling. The evaluation considers a set of archetypical nonductile RC frame structures of varying height that are designed according to the seismic provisions of the 1967 Uniform Building Code. The results indicate that nonductile RC frame structures have a mean annual frequency of collapse ranging from 5 to 14×10-3 at a typical high-seismic California site, which is approximately 40 times higher than corresponding results for modern code-conforming special RC moment frames. These metrics demonstrate the effectiveness of ductile detailing and capacity design requirements, which have been introduced over the past 30 years to improve the safety of RC buildings. Data on comparative safety between nonductile and ductile frames may also inform the development of policies for appraising and mitigating seismic collapse risk of existing RC frame buildings. DEWEY : 624.17 ISSN : 0733-9445 En ligne : http://ascelibrary.org/sto/resource/1/jsendh/v137/i4/p492_s1?isAuthorized=no [article] Seismic collapse safety of reinforced concrete buildings. II, Comparative assessment of nonductile and ductile moment frames [texte imprimé] / Abbie B. Liel, Auteur ; Curt B. Haselton, Auteur ; Gregory G. Deierlein, Auteur . - 2011 . - pp. 492-502. Génie Civil Langues : Anglais (eng) in Journal of structural engineering > Vol. 137 N° 4 (Avril 2011) . - pp. 492-502 Mots-clés : Collapse  Earthquake  engineering  Structural  reliability  Reinforced  concrete  structures  Buildings  Commercial  Seismic  effects Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : This study is the second of two companion papers to examine the seismic collapse safety of reinforced concrete frame buildings, and examines nonductile moment frames that are representative of those built before the mid-1970s in California. The probabilistic assessment relies on nonlinear dynamic simulation of structural response to calculate the collapse risk, accounting for uncertainties in ground-motion characteristics and structural modeling. The evaluation considers a set of archetypical nonductile RC frame structures of varying height that are designed according to the seismic provisions of the 1967 Uniform Building Code. The results indicate that nonductile RC frame structures have a mean annual frequency of collapse ranging from 5 to 14×10-3 at a typical high-seismic California site, which is approximately 40 times higher than corresponding results for modern code-conforming special RC moment frames. These metrics demonstrate the effectiveness of ductile detailing and capacity design requirements, which have been introduced over the past 30 years to improve the safety of RC buildings. Data on comparative safety between nonductile and ductile frames may also inform the development of policies for appraising and mitigating seismic collapse risk of existing RC frame buildings. DEWEY : 624.17 ISSN : 0733-9445 En ligne : http://ascelibrary.org/sto/resource/1/jsendh/v137/i4/p492_s1?isAuthorized=no