Selecting and Scaling Earthquake Ground Motions for Performing Response-History Analyses
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NIST GCR 11-917-15 Selecting and Scaling Earthquake Ground Motions for Performing Response-History Analyses NEHRP Consultants Joint Venture A partnership of the Applied Technology Council and the Consortium of Universities for Research in Earthquake Engineering Disclaimers This report was prepared for the Engineering Laboratory of the National Institute of Standards and Technology (NIST) under the National Earthquake Hazards Reduction Program (NEHRP) Earthquake Structural and Engineering Research Contract SB134107CQ0019, Task Order 69220. The statements and conclusions contained herein are those of the authors and do not necessarily reflect the views and policies of NIST or the U.S. Government. This report was produced by the NEHRP Consultants Joint Venture, a joint venture of the Applied Technology Council (ATC) and the Consortium of Universities for Research in Earthquake Engineering (CUREE). While endeavoring to provide practical and accurate information, the NEHRP Consultants Joint Venture, the authors, and the reviewers assume no liability for, nor express or imply any warranty with regard to, the information contained herein. Users of information contained in this report assume all liability arising from such use. Certain commercial software, equipment, instruments, or materials may have been used in the preparation of information contributing to this report. Identification in this report is not intended to imply recommendation or endorsement by NIST, nor is it intended to imply that such software, equipment, instruments, or materials are necessarily the best available for the purpose. NIST policy is to use the International System of Units (metric units) in all its publications. In this report, however, information is presented in U.S. Customary Units (inch-pound), as this is the preferred system of units in the U.S. earthquake engineering industry. Cover photo – Illustration of example Conditional Spectrum for the Palo Alto, California site, anchored for 2% in 50 year motions at T = 2.6s. NIST GCR 11-917-15 Selecting and Scaling Earthquake Ground Motions for Performing Response-History Analyses Prepared for U.S. Department of Commerce National Institute of Standards and Technology Engineering Laboratory Gaithersburg, Maryland By NEHRP Consultants Joint Venture A partnership of the Applied Technology Council and the Consortium of Universities for Research in Earthquake Engineering November 2011 U.S. Department of Commerce John Bryson, Secretary National Institute of Standards and Technology Patrick D. Gallagher, Under Secretary of Commerce for Standards and Technology and Director NIST GCR 11-917-15 Participants National Institute of Standards and Technology John (Jack) R. Hayes, Jr., Director, National Earthquake Hazards Reduction Program Steven L. McCabe, Deputy Director, National Earthquake Hazards Reduction Program Kevin K. F. Wong, Project Manager NEHRP Consultants Joint Venture Applied Technology Council Consortium of Universities for 201 Redwood Shores Parkway, Suite 240 Research in Earthquake Engineering Redwood City, California 94065 1301 S. 46th Street, Building 420 www.ATCouncil.org Richmond, California 94804 www.CUREE.org Joint Venture Management Joint Venture Program Committee Committee Jon A. Heintz (Program Manager) James R. Harris Michael Constantinou Robert Reitherman C.B. Crouse Christopher Rojahn James R. Harris Andrew Whittaker William T. Holmes Jack Moehle Andrew Whittaker Project Technical Committee Project Review Panel Andrew Whittaker (Project Director) John Egan Gail M. Atkinson Robert Kennedy Jack W. Baker Charles Kircher Jonathan Bray Nicolas Luco Damian N. Grant Robin McGuire Ronald Hamburger Jack Moehle Curt Haselton Michael Willford Paul Somerville Project Manager Working Group Members Ayse Hortacsu Norman Abrahamson Ana Luz Acevedo-Cabrera FEMA Representative Riccardo Diaferia Helmut Krawinkler Connor Hayden Ting Lin Preface The NEHRP Consultants Joint Venture is a partnership between the Applied Technology Council (ATC) and the Consortium of Universities for Research in Earthquake Engineering (CUREE). In 2007, the National Institute of Standards and Technology (NIST) awarded a National Earthquake Hazards Reduction Program (NEHRP) “Earthquake Structural and Engineering Research” contract (SB1341-07- CQ-0019) to the NEHRP Consultants Joint Venture to conduct a variety of tasks, including Task Order 69220 entitled “Improved Procedures for Selecting and Scaling Earthquake Ground Motions for Performing Response History Analysis.” The primary objective of this task was to develop guidance for selecting, generating, and scaling earthquake ground motions for effective use in performing response- history analyses for use in performance-based seismic engineering. The need for such guidance was identified in the ATC-57 report, The Missing Piece: Improving Seismic Design and Construction Practices (ATC, 2003), which defines a roadmap for the NIST problem-focused research and development program in earthquake engineering. Following a thorough study of the state of the practice with regard to selecting and scaling ground motions for nonlinear response-history analysis of buildings, the project team developed a list of key challenges facing design professionals tasked with selecting and scaling earthquake ground motions. Based on the findings identified, and considering the potential for impacting design practice in the near- term, the following topics were chosen for study: (1) selection of ground motions based on the Conditional Spectrum; (2) response-spectrum matching; and (3) near- fault ground motions and fault-rupture directivity. To encourage consensus and consistency in the state of the practice going forward, recommendations related to selecting and scaling ground motions for design and performance assessment of low- and medium-rise buildings, and a discussion on best practices for applying the current rules in building codes and standards, are provided. The NEHRP Consultants Joint Venture is indebted to the leadership of Andrew Whittaker, Project Director, and to the members of the project team for their efforts in developing this report. The Project Technical Committee, consisting of Gail Atkinson, Jack Baker, Jonathan Bray, Damian Grant, Ronald Hamburger, Curt Haselton, and Paul Somerville performed, monitored, and guided the technical work on the project. The Working Groups, including Norman Abrahamson, Ana Luz GCR 11-917-15 Preface iii Acevedo-Cabrera, Riccardo Diaferia, Connor Hayden, and Ting Lin conducted the problem-focused studies. The Project Review Panel, consisting of John Egan, Robert Kennedy, Charles Kircher, Nicolas Luco, Robin McGuire, Jack Moehle, and Michael Willford provided technical review, advice, and consultation at key stages of the work. A workshop of invited experts was convened to obtain feedback on the preliminary findings and recommendations, and input from this group was instrumental in shaping the final report. The names and affiliations of all who contributed to this report are provided in the list of Project Participants. The NEHRP Consultants Joint Venture also gratefully acknowledges Jack Hayes (NEHRP Director), Steven McCabe (NEHRP Deputy Director), Kevin Wong (NIST Project Manager), and Helmut Krawinkler (FEMA Technical Monitor) for their input and guidance in the preparation of this report, Ayse Hortacsu for ATC project management, and Peter N. Mork for ATC report production services. Jon A. Heintz Program Manager iv Preface GCR 11-917-15 Table of Contents Preface ................................................................................. iii List of Figures ........................................................................ xi List of Tables ........................................................................ xvii 1. Introduction ................................................................ 1-1 1.1 Project Motivation .......................................................................... 1-1 1.2 Project Objectives and Scope .......................................................... 1-2 1.3 Report Organization and Content ................................................... 1-2 2. Goals of Response-History Analysis ................................... 2-1 2.1 Introduction ..................................................................................... 2-1 2.2 Use of Response-History Analysis ................................................. 2-1 2.2.1 Goals of Design and Performance Assessment .................. 2-1 2.2.2 Evaluation of Goals ........................................................... 2-2 2.3 Types of Performance Assessment ................................................. 2-3 2.3.1 Intensity-Based Assessments ............................................. 2-3 2.3.2 Scenario-Based Assessments ............................................. 2-3 2.3.3 Risk-Based Assessments .................................................... 2-3 2.4 Response Parameters ...................................................................... 2-4 3. State of Practice .......................................................... 3-1 3.1 Introduction ..................................................................................... 3-1 3.2 New Buildings, ASCE/SEI Standard 7-05 ...................................... 3-2 3.2.1 Performance Expectations ................................................. 3-2 3.2.2 Rules for Selecting and Scaling Ground Motions .............. 3-2 3.2.3 Calculation of Demands for Component Checking ..........