Seismic Collapse Safety of Reinforced Concrete Buildings. I: Assessment of Ductile Moment Frames
Publication: Journal of Structural Engineering
Volume 137, Issue 4
Abstract
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 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 The study finds that the reduction in the minimum base shear, introduced in ASCE 7-05 and subsequently rescinded, dramatically increases the collapse risk of tall (long-period) frame buildings in high-seismic regions.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 (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.
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Acknowledgments
This work was supported by the Pacific Earthquake Engineering Research (PEER) Center through the Earthquake Engineering Research Centers Program of the National Science Foundation (under award number NSFEEC-9701568). Additional support was provided by the Applied Technology Council (ATC) through the FEMA P-695 (ATC-63) project, which was funded by FEMA. The writers further acknowledge the contributions of collaborators from PEER and ATC, including but not limited to Jack Baker, John Hooper, Charlie Kircher, Helmut Krawinkler, Eduardo Miranda, Marc Ramirez, and Sarah Taylor Lange. The writers are solely responsible for the accuracy of statements or interpretations contained in this paper, and no warranty is offered by PEER, FEMA, or ATC (its directors, members, or employees) with regard to the results, findings, and recommendations. These organizations and individuals do not assume any legal liability or responsibility for the accuracy, completeness, or usefulness of any of the information, product, or processes included in this paper.
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Information & Authors
Information
Published In
Journal of Structural Engineering
Volume 137 • Issue 4 • April 2011
Pages: 481 - 491
Copyright
© 2011 American Society of Civil Engineers.
History
Received: Jul 14, 2009
Accepted: Sep 12, 2010
Published online: Sep 22, 2010
Published in print: Apr 1, 2011
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