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หน้าหลัก Geotechnical earthquake engineering and soil dynamics IV : May 18-22, 2008, Sacramento, California
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GEOTECHNICAL SPECIAL PUBLICATION NO. 181 GEOTECHNICAL EARTHQUAKE ENGINEERING AND SOIL DYNAMICS IV PROCEEDINGS OF THE CONFERENCE May 18–22, 2008 Sacramento, California SPONSORED BY The Geo-Institute of the American Society of Civil Engineers EDITED BY David Zeng Majid T. Manzari Dennis R. Hiltunen Published by the American Society of Civil Engineers Copyright and Disclaimer ISBN: 978-0-7844-0975-6 Any statements expressed in these materials are those of the individual authors and do not necessarily represent the views of ASCE, which takes no responsibility for any statement made herein. No reference made in this publication to any specific method, product, process or service constitutes or implies an endorsement, recommendation, or warranty thereof by ASCE. The materials are for general information only and do not represent a standard of ASCE, nor are they intended as a reference in purchase specifications, contracts, regulations, statutes, or any other legal document. ASCE makes no representation or warranty of any kind, whether express or implied, concerning the accuracy, completeness, suitability, or utility of any information, apparatus, product, or process discussed in this publication, and assumes no liability therefore. This information should not be used without first securing competent advice with respect to its suitability for any general or specific application. Anyone utilizing this information assumes all liability arising from such use, including but not limited to infringement of any patent or patents. Copyright © 2008 by the American Society of Civil Engineers. All Rights Reserved. ASCE and American Society of Civil Engineers—Registered in U.S. Patent and Trademark Office. Photocopies and reprints. You can obtain instant permission to photocopy ASCE publications by using ASCE's online permission service (www.pubs.asce.org/authors/RightslinkWelcomePage.html). Requests for 100 copies or more should be submitted to the Reprints Department, Publications Division, ASCE, (address abov; e); email: email@example.com. A reprint order form can be found at www.pubs.asce.org/authors/reprints.html. American Society of Civil Engineers ASCE International Headquarters 1801 Alexander Bell Drive Reston, VA 20191-4400 USA Call Toll-Free in the U.S.: 1-800-548-2723 (ASCE) Call from anywhere in the world: 1-703-295-6300 Internet: http://www.pubs.asce.org Preface The papers contained in this publication were prepared for presentation in GEESD IV, the 4th decennial Geotechnical Earthquake Engineering and Soil Dynamics Conference organized by the EESD Committee of the ASCE Geo-Institute. GEESD IV follows the highly successful GEESD conferences in Seattle, Washington (1998); Park City, Utah (1988); and Pasadena, California (1978). The conference covers a broad field of topics in soil dynamics and geotechnical earthquake engineering, including engineering seismology, dynamic material properties, geophysical methods, SASW benchmarking, site response, liquefaction, ground improvement, embankment dams, tailings dams, landfills, levees, lifelines and networks, mapping and zoning, NEESR research, numerical modeling, piers and wharves, retaining structures, foundation dynamics, soil-structure interaction, stability of natural slopes, and surface fault rupture. The organizing committee invited nine outstanding keynote speakers and ten theme lecturers to present papers on developments in important areas of geotechnical earthquake engineering. The committee reviewed over 400 abstracts and 260 papers. The papers received undergo a peer review before being accepted. The standards for the peer review followed those required for ASCE Geotechnical Special Publications. Each paper must receive two positive reviews to be accepted and must be revised to conform to the mandatory revisions of the reviewers. Due to a tight schedule, there was not enough time for more than one cycle of review and revision. In the end, 234 papers were accepted for publication. All the papers are eligible for discussion in the ASCE Journal of Geotechnical and Geoenvironmental Engineering and for ASCE awards. The paper review would have been impossible without the help of a group of lead reviewers, who, on behalf of the Proceedings and Publications Committee, organized and in some cases conducted the review of a group of papers. The editors would like to acknowledge the invaluable contribution of the following lead reviewers: Pedro Arduino Scott Brandenberg William Frasier Laureano Hoyos Amir Kaynia Xiang-Song Li Gopal Madabhushi George Mylonakis Adrian Rodriguez-Marek Brent Rosenblad Usama. El Shamy Joseph Wartman Liping Yan E. Zhai Dominic Assimaki Mandar Dewoolkar Russell Green Tom Holzer Mike Kalinski Jeen-Sheng Lin N. Matasovic Soheil Nazarian Ellen Rathje Raj Siddharthan Mingjian Tao Yu-Hsing Wang Bill Yu Ariyaputhirar Balakrishnan Ali Eliadorani Yousef Hashash Boris Jeremic James N. Lee Hoe I. Ling Jorge Meneses Ronald Pak Kyle Rollins Mike Sharp Thusyanthan Jerry Wu Mourad Zeghal The lead reviewers were helped by the following highly qualified reviewers in the review process: F. Abedzadeh Carlos Amante Ralph Archuleta Rajendram Arulnathan George Athanasopoulos Ariya Balakrishnan James Bay Jon Bischoff David M. Boore Scott J. Brandenberg Billy Camp Kemal Önder Çetin Qimin Chen Daniel B. Chu Brady Cox Craig A. Davis Jeffrey S. Dingrando Allison Faris Keyvan Fotoohi M. Ghannad Robert Goughnour Brian Greene Kate Gunberg Tarik Hadj-Hamou Youssef Hashash Bruce Hilton Laureano Hoyos Mahadevan Ilankatharan Hsein Juang Thangalingam Kanagalingam Stephanie A. King Ramachandran Kulasingam Christian Ledezma X.S. Li Nina Liu Barbara Luke Nicolas Malasavage Neven Matasovic Claudia Medina H.Y. Ming Kanthasamy K. Muraleetharan Erfan Nezami Ronald Pak Achilleas Papadimitriou Bashar Alramahi Donald Anderson Pedro Arduino Dominic Assimaki Laurie Baise Paola Bandini Michael Beaty Antonio Bobet Ross Boulanger Andrew Brennan Antonio Carraro C. Yoga Chandran Xin Chen Ulas Cilingir Karina Dahl Anirban De Jiwei Duan Americo Fernandez Mahmoud El Gamal James Gingery Vladimir Grazier Nenad Gucunski Marte Gutierrez Stuart Haigh Chunmei He Sahadat Hossain Roman Hryciw Allen Jones Michael Kalinski Pirooz Kashighandi Tadahiro Kishida Dominik Lang Jong-Sub Lee Chi-Tseng Ted Liu Yan Liu Alan J. Lutenegger Erik Malvick John McCartney Jorge Meneses Robb E. Moss George Mylonakis Guney Olgun Aasha Pancha Aris Papadopoulos Jorge Alva Scott Anderson Richie Armstrong Adda Athanasopoulos Jack Baker Steven F. Bartlett Victoria Bennet Fabian Bonilla Aaron Bradshaw Peter M. Byrne Gonzalo Castro Nien Chang Deepankar Choudhury Ryan Cole Panos Dakoulas Christopher M. Dietel Cedric Fairbanks Jon B. P. Fletcher Louis Ge Eric Gottheld Russell Green Simon Gudina B.B. Guzina Curt Haselton Greg Hempen Jeffery Howard Jianping Hu Shawn O. Jones Ronnie Kamai Dong-Soo Kim Alexander Kozak Hubert Law Anne Lemnitzer Gang Liu Thomas Lok B.K. Maheshwari Geoffrey R. Martin Nason McCullough Paul Michaels Charles S. Mueller Erik J. Newman Rolando Orense Miguel Pando Duhee Park Richard Pearce Arben Pitarka Anand Puppala N. (Ravi) Ravichandran Adrian Rodriguez-Marek Dario Rosidi Rodolfo B. Sancio Hassan Sedarat Anastasios Sextos Lisheng Shao Francisco Silva-Tulla Shin-Tai Song William J Stephenson Luis Suez Mahdi Taiebat Salih Tileylioglu Andrew Tolleson Chi-Chin Tsai Roberto Vasallo Jui-pin Wang Lei Wei Dharma Wijewickreme Ching-Liu Wu J. Yang Xinbao Yu Dimitris Zekkos Feng Zhang Michael Pender Dimitrios Pitilakis Tong Qiu Michael Reichle Stefan Romanoschi David Saftner Marika Santagata Hope A. Seligman Anoosh Shamsabadi Thevachandran Shenthan Siva Sivathayalan Alan Stadler Patrick Strenk Erwin Supranata Payman Kahili Tehrani John C. Tinsley, III Aurel Trandafir Wen Tseng Christos Vrettos Yu-Hsing Wang Daniel Whang Robert A Williams Min-hao Wu Zhaohui Yang Xiong (Bill) Yu Aspa Zerva Jian Zhang Zhigang Peng Carmine Polito Alan Rauch Glenn Rix Brent Rosenblad Pijush Samui Sireesh Saride Kallol Sett Usama El Shamy Parisa Shokouhi Darin Sjoblom Konstantin Stamatopoulos D. Su Ertugrul Taciroglu Eric Thompson Binod Tiwari Thaleia Travasarou Javier Ubilla Judith Wang Joseph Wartman David White Chris J. Wills Horng-Jyh Yang Sungmin Yoon Zia Zafir Jinxing Zha Jie Zhang The editors would like to thank the conference chairman, Ross Boulanger, for his tireless efforts and invaluable contribution. Also, we would like to acknowledge the significant assistance by Ms. Sheana Singletary, Program Administrator of ASCE Conference and Meetings Services. Finally, we would like to express our sincere appreciation to all the authors for their significant contributions to the success of the conference. Xiangwu (David) Zeng Case Western Reserve University Majid Manzari George Washington University Dennis Hiltunen University of Florida Geotechnical Special Publications 1 Terzaghi Lectures 2 Geotechnical Aspects of Stiff and Hard Clays 3 Landslide Dams: Processes, Risk, and Mitigation 7 Timber Bulkheads 9 Foundations & Excavations in Decomposed Rock of the Piedmont Province 11 Dynamic Response of Pile FoundationsExperiment, Analysis and Observation 14 Geotechnical Aspects of Karst Terrains 15 Measured Performance Shallow Foundations 16 Special Topics in Foundations 17 Soil Properties Evaluation from Centrifugal Models 18 Geosynthetics for Soil Improvement 19 Mine Induced Subsidence: Effects on Engineered Structures 21 Hydraulic Fill Structures 22 Foundation Engineering 23 Predicted and Observed Axial Behavior of Piles 24 Resilient Moduli of Soils: Laboratory Conditions 25 Design and Performance of Earth Retaining Structures 27 Geotechnical Engineering Congress 28 Detection of and Construction at the Soil/Rock Interface 29 Recent Advances in Instrumentation, Data Acquisition and Testing in Soil Dynamics 32 Embankment of Dams-James L. Sherard Contributions 33 Excavation and Support for the Urban Infrastructure 34 Piles Under Dynamic Loads 35 Geotechnical Practice in Dam Rehabilitation 37 Advances in Site Characterization: Data Acquisition, Data Management and Data Interpretation 39 Unsaturated Soils 40 Vertical and Horizontal Deformations of Foundations and Embankments 41 Predicted and Measured Behavior of Five Spread Footings on Sand 42 Serviceability of Earth Retaining Structures 43 Fracture Mechanics Applied to Geotechnical Engineering 44 Ground Failures Under Seismic Conditions 45 In Situ Deep Soil Improvement 46 Geoenvironment 2000 47 Geo-Environmental Issues Facing the Americas 48 Soil Suction Applications in Geotechnical Engineering 49 Soil Improvement for Earthquake Hazard Mitigation 50 Foundation Upgrading and Repair for Infrastructure Improvement 51 Performance of Deep Foundations under Seismic Loading 52 Landslides under Static and Dynamic Conditions-Analysis, Monitoring, and Mitigation 53 Landfill Closures-Environmental Protection and Land Recovery 54 Earthquake Design and Performance of Solid Waste Landfills 55 Earthquake-Induced Movements and Seismic Remediation of Existing Foundations and Abutments 56 Static and Dynamic Properties of Gravelly Soils 57 Verification of Geotechnical Grouting 58 Uncertainty in the Geologic Environment 59 Engineered Contaminated Soils and Interaction of Soil Geomembranes 60 Analysis and Design of Retaining Structures Against Earthquakes 61 Measuring and Modeling Time Dependent Soil Behavior 62 Case Histories of Geophysics Applied to Civil Engineering and Public Policy 63 Design with Residual Materials: Geotechnical and Construction Considerations 64 Observation and Modeling in Numerical Analysis and Model Tests in Dynamic SoilStructure Interaction Problems 65 Dredging and Management of Dredged Material 66 Grouting: Compaction, Remediation and Testing 67 Spatial Analysis in Soil Dynamics and Earthquake Engineering 68 Unsaturated Soil Engineering Practice 69 Ground Improvement, Ground Reinforcement, Ground Treatment: Developments 1987-1997 70 Seismic Analysis and Design for Soil-PileStructure Interactions 71 In Situ Remediation of the Geoenvironment 72 Degradation of Natural Building Stone 73 Innovative Design and Construction for Foundations and Substructures Subject to Freezing and Frost 74 Guidelines of Engineering Practice for Braced and Tied-Back Excavations 75 Geotechnical Earthquake Engineering and Soil Dynamics III 76 Geosynthetics in Foundation Reinforcement and Erosion Control Systems 77 Stability of Natural Slopes in the Coastal Plain 78 Filtration and Drainage in Geotechnical/Geoenvironmental Engineering 79 Recycled Materials in Geotechnical Applications 80 Grouts and Grouting: A Potpourri of Projects 81 Soil Improvement for Big Digs 82 Risk-Based Corrective Action and Brownfields Restorations 83 Design and Construction of Earth Retaining Systems 84 Effects of Construction on Structures 85 Application of Geotechnical Principles in Pavement Engineering 86 Big Digs Around the World 87 Jacked Tunnel Design and Construction 88 Analysis, Design, Construction, and Testing of Deep Foundations 89 Recent Advances in the Characterization of Transportation Geo-Materials 90 Geo-Engineering for Underground Facilities 91 Special Geotechnical Testing: Central Artery/Tunnel Project in Boston, Massachusetts 94 Performance Confirmation of Constructed Geotechnical Facilities 95 Soil-Cement and Other Construction Practices in Geotechnical Engineering 96 Numerical Methods in Geotechnical Engineering: Recent Developments 97 Innovations and Applications in Geotechnical Site Characterization 98 Pavement Subgrade, Unbound Materials, and Nondestructive Testing 99 Advances in Unsaturated Geotechnics 100 New Technological and Design Developments in Deep Foundations 101 Slope Stability 2000 102 Trends in Rock Mechanics 103 Advances in Transportation and Geoenvironmental Systems Using Geosynthetics 104 Advances in Grouting and Ground Modification 105 Environmental Geotechnics 106 Geotechnical Measurements: Lab & Field 107 Soil Dynamics and Liquefaction 2000 108 Use of Geophysical Methods in Construction 109 Educational Issues in Geotechnical Engineering 110 Computer Simulation of Earthquake Effects 111 Judgment and Innovation: The Heritage and Future of the Geotechnical Engineering Profession 112 Soft Ground Technology 114 Soils Magic 115 Expansive Clay Soils and Vegetative Influence on Shallow Foundations 116 Deep Foundations 2002: An International Perspective on Theory, Design, Construction, and Performance 117 Discrete Element Methods: Numerical Modeling of Discontinua 118 A History of Progress: Selected U.S. Papers in Geotechnical Engineering 119 Soil Behavior and Soft Ground Construction 120 Grouting and Ground Treatment 121 Probabilistic Site Characterization at the National Geotechnical Experimentation Sites 122 Sinkholes and the Engineering and Environmental Impacts of Karst 123 Recent Advances in Materials Characterization and Modeling of Pavement Systems 124 GeoSupport 2004: Drilled Shafts, Micropiling, Deep Mixing, Remedial and Specialty Foundation Systems 125 Current Practices and Future Trends in Deep Foundations 126 Geotechnical Engineering for Transportation Projects 127 Recycled Materials in Geotechnics 128 Soil Constitutive Models: Evaluation, Selection, and Calibration 129 Advances in Designing and Testing Deep Foundations 130 Advances in Pavement Engineering 131 Contemporary Issues in Foundation Engineering 132 Advances in Deep Foundations: In Memory of Michael W. O'Neill 133 Earthquake Engineering and Soil Dynamics 134 Soil Dynamics Symposium in Honor of Professor Richard D. Woods 135 Erosion of Soils and Scour of Foundations 136 Innovations in Grouting and Soil Improvement 137 Legal and Liability Issues in Geotechnical Engineering 138 Site Characterization and Modeling 139 Calibration of Constitutive Models 140 Slopes and Retaining Structures under Seismic and Static Conditions 141 International Perspectives on Soil Reinforcement Applications 142 Waste Containment and Remediation 143 Geomechanics: Testing, Modeling, and Simulation 144 Sinkholes and the Engineering and Environmental Impacts of Karst 145 Seismic Performance and Simulation of Pile Foundations in Liquefied and Laterally Spreading Ground 146 Asphalt Concrete: Simulation, Modeling and Experimental Characterization 147 Unsaturated Soils 2006 148 Advances in Unsaturated Soil, Seepage, and Environmental Geotechnics 149 Site and Geomaterial Characterization 150 Soil and Rock Behavior and Modeling 151 Advances in Earth Structures: Research to Practice 152 Ground Modification and Seismic Mitigation 153 Foundation Analysis and Design: Innovative Methods 154 Pavement Mechanics and Performance 155 Underground Construction and Ground Movement 156 Geomechanics II: Testing, Modeling, and Simulation 157 Computer Applications in Geotechnical Engineering 158 Contemporary Issues in Deep Foundations 159 Case Studies in Earth Retaining Structures 160 Dynamic Response and Soil Properties 161 Embankments, Dams, and Slopes: Lessons from the New Orleans Levee Failures and Other Issues 162 Problematic Soils and Rocks and In Situ Characterization 163 Geoenvironmental Engineering 164 Innovative Applications of Geophysics in Civil Engineering 165 Geosynthetics in Reinforcement and Hydraulic Applications 166 Educational Activities in Geotechnical Engineering 167 Geotechnics of Soil Erosion 168 Grouting for Ground Improvement: Innovative Concepts and Applications 169 Soil and Material Inputs for Mechanistic-Empirical Pavement Design 170 Probabilistic Applications in Geotechnical Engineering 171 Advances in Shallow Foundations 172 Soil Improvement 173 Advances in Measurement and Modeling of Soil Behavior 174 Designing Our Underground Space 175 Field Measurements in Geomechanics 2007 176 Analysis of Asphalt Pavement Materials and Systems: Emerging Methods 177 GeoCongress 2008: Geotechnics of Waste Management and Remediation 178 GeoCongress 2008: Geosustainability and Geohazard Mitigation 179 GeoCongress 2008: Characterization, Monitoring, and Modeling of GeoSystems 180 From Research to Practice in Geotechnical Engineering Ground Motions Keynote—Nonlinear Seismic Ground Response Analysis: Code Usage Protocols and Verification against Vertical Array Data Jonathan P. Stewart and Annie O. L. Kwok Assessment of Ground Motion Selection and Modification (GMSM) Methods for NonLinear Dynamic Analyses of Structures Christine A. Goulet, Jennie Watson-Lamprey, Jack Baker, Curt Haselton, and Nico Luco Identification of Near-Fault Velocity Pulses and Prediction of Resulting Response Spectra Jack W. Baker Preliminary Estimation of Seismically Induced Ground Strains from Spatially Variable Ground Motions Timothy D. Ancheta, Jonathan P. Stewart, Norman A. Abrahamson, and Robert L. Nigbor Probabilistic Use of Arias Intensity in Geotechnical Earthquake Engineering J. K. Howard, W. A. Fraser, and M. G. Schultz Seismic Design Criteria Ground Motions Joe Litehiser and James E. Marrone Seismic Hazard Analysis and Probabilistic Ground Motions in the Upper Mississippi Embayment J. Alfredo Fernandez and Glenn J. Rix Site Response A Simplified Constitutive Model to Simultaneously Match Modulus Reduction and Damping Soil Curves for Nonlinear Site Response Analysis Camilo Phillips and Youssef M. A. Hashash Basin Effects in the Upper Mississippi Embayment J. Alfredo Fernandez and Glenn J. Rix Comparing Weak- and Strong-Motion Spectral Ratios at the Turkey Flat Site Effects Test Area, Parkfield, California: Possible Nonlinear Soil Behavior Chris H. Cramer Consequences of Solution Non-Uniqueness in Surface Wave Tests for Seismic Response Studies Sebastiano Foti, Cesare Comina, Deniele Boiero, and Laura Valentina Socco Developing Site-Specific Design Response Spectra for a Type F Site Due to Liquefaction Endi Zhai Dynamic Response of Unsaturated Non-Collapsible and Collapsible Deposits Claudia Medina and Mourad Zeghal Evaluation of Site Response for Deepwater Field Fabrizio Ardoino, Chiara M. Traverso, and Eric J. Parker Hysteretic Damping Correction and Its Effect on Non-Linear Site Response Analyses Zhi-Liang Wang, C. Y. Chang, and C. C. Chin Influence of Rate Dependent Soil Behavior on Propagated Ground Motion Dong-Yup Kwak, Jae-Kwang Ahn, Duhee Park, and Youssef M. A. Hashash Modeling Nonlinear Site Response Uncertainty in the Los Angeles Basin Dominic Assimaki, Wei Li, Jamison M. Steidl, and Jan Schmedes Nonlinear Shear Wave Propagation in Strain Stiffening and Strain Softening Soil Jui-Ching Chou and Bruce Kutter Parametric Analysis of the Seismic Response of Irregular Topographic Features Arash Razmkhah, Mohsen Kamalian, and Roham Golrokh Seismic Response of the San Francisco International Airport Airfield during the 1989 Loma Prieta Earthquake Lelio H. Mejia, Jiaer Wu, Zhaohui Yang, and Jim Chiu Site Response Analysis for Tito Scalo Area (PZ) in the Basilicata Region, Italy Antonio Cavallaro, Salvatore Grasso, and Michele Maugeri Site Response to Vertical Earthquake Motion J. Yang and X. R. Yan Spatial Analysis of Damage Distribution in the 2001 Southern Peru Earthquake Nicholas E. Malasavage and Joseph Wartman Strain-Dependent Soil Properties Estimated from Downhole Array Recordings at Kashiwazaki-Kariwa Nuclear Power Plant during the 2007 Niigata-Ken Chuetsu-Oki Earthquake Kohji Tokimatsu and Ryosuke Sugimoto The Turkey Flat Blind Prediction Experiment for the September 28, 2004 Parkfield Earthquake: Comparison with Other Turkey Flat Recordings Hamid R. Haddadi, Anthony F. Shakal, and Charles R. Real The Turkey Flat Blind Prediction Experiment for the September 28, 2004 Parkfield Earthquake: General Overview and Models Tested Charles R. Real, Anthony F. Shakal, and Brian E. Tucker Two Dimensional Evaluation of Site Effect in Rectangular Valleys Nima Tafazzoli, Mohammad Hassan Baziar, and Habib Shahnazari Mapping and Faulting Theme Paper—Probabilistic Liquefaction Hazard Mapping Thomas L. Holzer A Deformation-Based Approach for Mapping Earthquake-Induced Liquefaction Hazard Charles R. Real, Keith L. Knudsen, and Marvin O. Woods A New Site Classification System Based on Strong Motion Analysis in Iran M. R. Ghayamghamian and A. R. Nojavan An Evaluation of Site Classification for National Strong-Motion Recording Stations in Turkey M. A. Sandkkaya, M. T. Ylmaz, B. S. Bakr, and S. Akkar Earthquake Loss Estimation Tool for Urban Areas Atilla Ansal, Asli Kurtulus, and Gökce Tönük Geological and Microtremor Survey, Damage Distribution, and Reconstruction of Muzaffarabad and Surroundings after the 2005 Kashmir Earthquake Kazuo Konagai, Jorgen Johansson, Atsunori Numata, Shigeki Takatsu, and Takaaki Ikeda Incorporating the Effects of Site Geology in CEUS Hazard Maps Chris H. Cramer Seismic Microzonation of Shiraz City, Southwest of Iran A. Ghalandarzadeh, S. Sahraeian, A. Kavand, and B. Kamrani Moghaddam The Effect of Shallow Foundation Position on Their Interaction with Reverse Faults Waqas Ahmed, Fraser Bransby, and Shuichi Nagaoka Dynamic Properties of Soils Cyclic Shear Tests of Municipal Waste in Large Triaxial Device for Identification of Its Dynamic Properties Ikuo Towhata and Masaaki Uno Density Effects on the Aging Behavior of Sands and the Anisotropy of Aging-Induced Stiffness Increases Yu-Hsing Wang and King-Yuen Tsui Development of a P-Wave Measurement System for Laboratory Specimens Sajjad Maqbool and Junchi Koseki Development of Buried Sensors for Stiffness Measurements of Soft Clays Using Bender Elements Jae Woo Jung, Chul Soo Park, and Young Jin Mok Development of Methods to Predict the Dynamic Behavior of Fine Coal Refuse: Preliminary Results from Two Sites in Appalachia Michael E. Kalinski and Joshua L. Phillips Dynamic Performance of Toyoura Sand Reinforced with Randomly Distributed Carpet Waste Strips H. Ghiassian, R. Jamshidi, and A. R. Tabarsa Dynamic Properties of Coal Waste Refuse in a Tailings Dam Xiangwu Zeng, James A. Goble, and Lei Fu Dynamic Properties of Saturated Compacted Soils Chia-Pin Wu, Jin-Hung Hwang, and Tsai-Kuey Chien Dynamic Response of Unsaturated Soils Using Resonant Column and Bender Element Testing Techniques L. R. Hoyos, P. Takkabutr, A. J. Puppala, and Md. S. Hossain Effective Soil Density for Small Strain Shear Wave Propagation Tong Qiu and Patrick J. Fox Effects of Cyclic Rotation of Principal Stress Axes and Intermediate Principal Stress Parameter on the Deformation Behavior of Sands Jian-Min Zhang, Zhao-Xia Tong, and Yi-Lin Yu Evaluation of Dynamic Properties of a Calcite Cemented Gravely Sand S. Mohsen Haeri, Mohammad Reza Shakeri, and S. Ali Shahcheraghi Pore Fluid Induced Damping of Saturated Soil in Resonant Column Tests Tong Qiu Sand Aging Field Study R. A. Green, R. D. Hryciw, D. A. Saftner, C. D. P. Baxter, Y. Jung, and T. Jirathanathaworn Stress Integration Approach for Soil Damping Measurements in Torsional Testing Inthuorn Sasanakul, James A. Bay, and Yoon-Shin Bae Water, Inertial Damping, and the Complex Shear Modulus Paul Michaels Dynamic Properties of Naturally-Cemented Silts Ravi Murthy, Soheil Nazarian, and Miguel Picornell Geophysical Measurement Techniques A Comparison of Shear Wave Velocity Profiles from SASW, MASW, and ReMi Techniques Khiem T. Tran and Dennis R. Hiltunen Deep Shear Wave Velocity Profiling of Poorly Characterized Soils Using the NEES LowFrequency Vibrator Brent L. Rosenblad, Kenneth H. Stokoe II, Jianhua Li, Brad Wilder, and Farn-Yuh Menq Development and Applications of In-Hole Seismic Method to Measure Shear Wave Velocity of Subsurface Materials Chul Soo Park, Jae Woo Jung, and Young Jin Mok Use of Shear Wave Velocity to Estimate Settlement Potential in Mine Spoils Michael E. Kalinski Inversion Algorithm to Evaluate Velocity Profiles from Downhole Seismic Tests J. Alfredo Fernandez, Glenn J. Rix, and Savannah Gowdy Liquefaction General Characterizing the Liquefaction Resistance of Aged Soils Hossein Hayati, Ronald D. Andrus, Sarah L. Gassman, Michael Hasek, William M. Camp, and Pradeep Talwani Comparison of Recently Developed Liquefaction Analysis Methods at Two Fluvial Sand Sites Tianfei Liao, John R. Davie, Hazem A. Sarhan, and Emre Biringen Cyclic Response of a Sand with Thixotropic Pore Fluid C. S. El Mohtar, J. Clarke, A. Bobet, M. Santagata, V. Drnevich, and C. Johnston Effect of High Confining Stresses on Static and Cyclic Strengths of Mine Tailing Materials Michael Riemer, Yoshi Moriwaki, and James Obermeyer Effects of Mica Content on Cyclic Resistance of Poorly-Graded Sand Kimberly Schmidt Effects of Stress Reduction Factors on Liquefaction Analysis Gökce Tönük and Atilla Ansal Influence of Aging on Liquefaction Potential: Preliminary Results Robb Eric S. Moss, David M. Thornhill, Ashley I. Nelson, and Darcie A. Levulett Investigating the Critical State Using Laboratory Ring Shear Tests Abouzar Sadrekarimi and Scott M. Olson Liquefaction Resistance Recovered From "On-the-Fly" CPTu-Measured Pore Pressures Michael Fitzgerald and Derek Elsworth Numerical and Physical Modeling of Liquefaction Mechanisms in Layered Sands Pelin Tohumcu zener, Kutay zaydn, and Mehmet Berilgen Observations on Sand Boils from Simple Model Tests Andrew Brennan Pore Structure Variation of Porous Media under Vibrations Ming Xiao and Lakshmi N. Reddi The Effect of the Hammer Energy Efficiency Ratio on SPT-Based Liquefaction Evaluation Troy Hull, Jason Butler-Brown, and Travis Willis The Rigidity Recovery of Post Liquefied Soils Seiji Kano, Hiroshi Kidera, Yasushi Sasaki, Takashi Ikeoka, and Koichi Ichii The Seismic Dilatometer Marchetti Test (SDMT) for Evaluating Liquefaction Potential under Cyclic Loading S. Grasso and M. Maugeri Using Decision-Tree Learning to Assess Liquefaction Potential from CPT and Vs Gary Livingston, Michael Piantedosi, Pradeep Kurup, and T. G. Sitharam Effects on Structures and Foundations An Experimental Study of the Effect of Seepage Force on Liquefaction of Soil in Embankments Gang Liu, Xiangwu Zeng, and Xiangsong Li Assessment of Structure-Induced Liquefaction Triggering Berna Unutmaz and K. Onder Cetin Centrifuge Experimentation of Building Performance on Liquefied Ground Shideh Dashti, Jonathan Bray, Michael Riemer, and Dan Wilson Components of Dynamic Subgrade Reaction on Pile in Saturated Sand Hideki Funahara Effect of Soil Liquefaction on Flexural Behavior of Axially and Laterally Loaded Piles R. S. Meera and P. K. Basudhar FD Solutions for Static and Dynamic Winkler Models with Lateral Spread Induced Earth Pressures on Piles D. W. Chang, B. S. Lin, C. H. Yeh, and S. H. Cheng Mechanism of Pile Group Settlement in Liquefiable Soils Jonathan Knappett and Gopal Madabhushi Performance-Based Seismic Response of Pile Foundations Brendon A. Bradley, Misko Cubrinovski, and Rajesh P. Dhakal Plastic Hinge Formation in Pile Foundations Due to Liquefaction-Induced Loads S. R. Rajaparthy, Z. Zhang, T. C. Hutchinson, and F. Lang The Role of Soil Compressibility in Centrifuge Model Tests of Piles Foundation Undergoing Lateral Spreading of Liquefied Soil Marcelo Gonzles, Javier Ubilla, Tarek Abdoun, and Ricardo Dobry Liquefaction of Silty Soils Cyclic Failure of Fine-Grained Soils during the 1999 Kocaeli Earthquake Volkan Okur, Selim Altun, and Atilla Ansal Cyclic Shear Response of Undisturbed and Reconstituted Low-Plastic Fraser River Silt Dharma Wijewickreme and Maria V. Sann Effect of Fines on Sand Residual Strength after Liquefaction Pedro de Alba and Thomas P. Ballestero Effect of Sand Gradation and Fines Type on Liquefaction Behaviour of Sand-Fines Mixture Md. Mizanur Rahman and Sik-Cheung Robert Lo Effects of Fines on Undrained Behaviour of Sands Misko Cubrinovski and Sean Rees Effects of Permeability on Liquefaction Resistance and Cone Resistance S. Thevanayagam and N. Ecemis Liquefaction Behavior of Mississippi River Silts Ali M. Izadi, Ronaldo Luna, and Richard W. Stephenson Liquefaction Resistance of Sands Containing Varying Amounts of Fines G. A. Athanasopoulos and V. C. Xenaki Post-Liquefaction Shear Behavior of Bonneville Silty-Sand Zahra A. Amini and Aurelian C. Trandafir Probabilistic Assessment of Cyclic Soil Straining in Fine-Grained Soils H. Tolga Bilge and K. Onder Cetin Shaking Table Test on a Large Specimen of Mailiao Silty Sand Tzou-Shin Ueng, Chia-Han Chen, Cheng-Fu Tsou, and Yi-Cheng Chen Ground Improvement Keynote—Recent Developments in Ground Improvement for Mitigation of Seismic Risk to Existing Embankment Dams James K. Mitchell Application of Deep Dynamic Compaction to U.S. Route 44 Relocation Project Yong Tan Centrifuge Testing of Prefabricated Vertical Drains for Liquefaction Remediation Antonio Marinucci, Ellen Rathje, Seiji Kano, Ronnie Kamai, Carolyn Conlee, Rachelle Howell, Ross Boulanger, and Patricia Gallagher Colloidal Silica Gel and Sand Mixture Dynamic Properties Laura Spencer, Glenn J. Rix, and Patricia Gallagher Compaction Grouting to Mitigate Liquefaction for a New Medical Retail Building Mark Russell, Jeff Geraci, and David Murray Cone Penetration Resistance Variation with Time after Blast Liquefaction Testing Kyle M. Rollins and Joshua K. S. Anderson Cone Penetration Testing before, during, and after Blast-Induced Liquefaction William M. Camp III, Paul W. Mayne, and Kyle M. Rollins Dynamic Response of an Embankment during Stone-Column Piling Dario Rosidi, Areq Gharabegian, and Deh-Jeng Jang Evaluation of a Geogrid-Reinforced Soil Mat to Mitigate Post-Liquefaction SettlementsA Case Study James R. Gingery and Scott M. Merry First Applications of the SAVE Compozer Method (Non-Vibratory Stone Columns) for Soil Densification in the U.S. Jun Mukai, Masaru Sakakibara, Juan I. Baez, Sean G. Callan, and Hideo Tsuboi Imaging a Grouted Column in a Centrifuge Model Using Shear Wave Velocity Tomography Scott J. Brandenberg Increase in Cyclic Liquefaction Resistance of Sandy Soil Due to Installation of Drilled Displacement Piles Timothy C. Siegel, Willie M. NeSmith, and W. Morgan NeSmith Liquefaction Potential Mitigation Using Rapid Impact Compaction Lori A. Simpson, Serena T. Jang, Cary E. Ronan, and Lisa M. Splitter Monitoring for Successful Site Improvement Brian D. Bauldry, Lisheng Shao, and Francis B. Gularte Numerical Modeling of the Seismic Response of Columnar Reinforced Ground C. Guney Olgun and James R. Martin II Relations between Penetration Resistance and Cyclic Strength to Liquefaction as Affected by KC-Conditions Kenji Harada, Kenji Ishihara, Rolando P. Orense, and Jun Mukai Seismic Response Evaluation of an Onshore Building Site Improved by Deep Mixed Foundation System Raj V. Siddharthan and Ali Porbaha Shear Stress Redistribution as a Mechanism to Mitigate the Risk of Liquefaction Russell A. Green, C. Guney Olgun, and Kord J. Wissmann Study on Uplift Behaviour of Plate Anchor in Geogrid Reinforced Sand Bed K. Ilamparuthi, P. T. Ravichandran, and M. Mohammed Toufeeq Uplift Testing of Rammed Aggregate Pier Systems Tom Farrell, Brendan FitzPatrick, and William Kenney Numerical Modeling DEM Simulation of the Seismic Response of Shallow Foundation on Liquefiable Soil U. El Shamay Efficient Numerical Modeling of Liquefaction-Induced Deformations of Soil Structures Achilleas Papadimitriou, Konstantinos Andrianopoulos, and George Bouckovalas Numerical Simulation of Seismic Ground Motion Isolation Using Fully Coupled Nonlinear Response in Saturated Sands Mahdi Taiebat, Boris Jeremi, Zhao Cheng, and Yannis Dafalias Transient Boundary Integral Equation of Dynamic Unsaturated Poroelastic Media Iman Ashayeri, Mohsen Kamalian, and Mohammad Kazem Jafari Soil-Structure Interaction (SSI) General Determination of Soil-Structure Interaction Effects for a Model Test Structure Using Parametric System Identification Procedures Salih Tileylioglu, Robert L. Nigbor, and Jonathan P. Stewart Dimensional Analysis of Soil-Foundation-Structure System Subjected to Near Fault Ground Motions Jian Zhang and Yuchuan Tang Dimensional Response Analysis of Inelastic Structures Nicos Makris and Theodoros Psychogios Dynamic Effects of Impact Machine Foundations Mark R. Svinkin Physical and Numerical Modeling of Dynamic Soil-Structure Interaction Mohammad H. T. Rayhani and Hesham El Naggar Response Sensitivity Analysis of Soil-Structure Interaction (SSI) Systems Quan Gu and Joel P. Conte Seasonally Frozen Soil Effects on the Nonlinear Behavior of a Parking Garage Feng Xiong, Zhaohui (Joey) Yang, Feifei Bai, and He Liu Sliding Blocks under Near-Fault Pulses: Closed-Form Solutions Elia Voyagaki, George Mylonakis, and Ioannis N. Psycharis SSI and Shallow Foundations Advanced 3-D Seismic Soil-Structure Interaction Analysis of a Cellular-Raft Foundation in Soft Clay Juan M. Mayoral, Miguel P. Romo, and Sergio Martinez Dynamic Soil-Structure Interaction for SDOF Structures on Footings and Piles Andreas Maravas, George Mylonakis, and Dimitris L. Karabalis Effect of Critical Contact Area Ratio on Moment Capacity of Rocking Shallow Footings Sivapalan Gajan and Bruce L. Kutter Material Model Parameters for Shallow Foundation Numerical Analysis Prishati Raychowdhury and Tara Hutchinson Numerical Simulation of a Soil Model-Model Container-Centrifuge Shaking Table System Mahadevan Ilankatharan and Bruce Kutter Numerical Simulation of Displacement Functions of Strip Footings Abir Jendoubi, Frdric Legeron, and Mourad Karray Wave Propagation under Vertically Excited Surface Foundation Jaehun Ahn, Giovanna Biscontin, and Jose M. Rosset SSI and Pile Foundations Analysis of Statnamic Behavior of Full-Scale Pile Group in Soft Clays and Silts Tetsuo Tobita, Gi Cheon Kang, Susumu Iai, and Kyle M. Rollins Cyclic P-Y Curves for a Pile in Cohesive Soil Travis M. Gerber and Kyle M. Rollins E-Defense Facility: A Frontier in Geotechnical Physical Modeling Ramin Motamed, Ikuo Towhata, and Tsuyoshi Honda Nonlinear Behavior of Single Piles Vibrating Vertically Jin-xing Zha and George Gazetas Non-Linear Dynamic Response of Deepwater Suction Pile Foundation Fabrizio Ardoino, Chiara M. Traverso, and Eric J. Parker Piles under Earthquake Loads Shamsher Prakash and Vijay K. Puri Response of Clay-Pile System under Earthquake Loading Subhadeep Banerjeer, Siang Huat Goh, and Fook Hou Lee Static and Dynamic Lateral Load Tests on a Pile Cap with Partial Gravel Backfill Kyle M. Rollins, Ku Hyun Kwon, and Travis M. Gerber Undrained Tip Response of Drilled Shaft in Cohesionless Soils Sherif Elfass and Gary Norris SSI and Retaining Structures Analysis of the Seismic Behaviour of Propped Retaining Structures Luigi Callisto, Fabio M. Soccodato, and Riccardo Conti Distribution of Seismic Earth Pressures on Gravity Walls by Wave-Based Stress Limit Analysis Panos Kloukinas, George Mylonakis, and Costas Papantonopoulos Dynamic Centrifuge Study of Seismically Induced Lateral Earth Pressures on Retaining Structures Nicholas Sitar and Linda Al Atik Excitation and Flexibility Effects on Dynamic Response of Cantilever Retaining Walls zgr L. Erturul, Selman Salam, and M. Yener zkan Extended Veletsos-Younan Model for Geofoam Compressible Inclusions behind Rigid, Non-Yielding Earth-Retaining Structures John S. Horvath Lateral Seismic Soil Pressures on Soldier Pile Walls Jin-xing Zha Permanent Seismic Deformation of MSE Walls with Uneven Reinforcement Raj V. Siddharthan and Gopalan Vishnan Seismic Earth Pressures behind Retaining Walls: Effects of Rigid-Body Motions Chulmin Jung and Antonio Bobet Seismic Lateral Earth Pressure Reduction on Earth-Retaining Structures Using Geofoams John S. Horvath Seismic Modeling of a 135-Foot-Tall MSE Wall D. D. Lindquist The Effect of Amplification on the Seismic Stability of Reinforced Soil Slopes Using Horizontal Slice Method Hamid Reza Nouri and Ali Fakher Bridges Centrifuge Modeling of Pile Pinning Effects R. J. Armstrong, R. W. Boulanger, U. Gulerce, B. L. Kutter, and D. W. Wilson Closed-Form Force-Displacement Backbone Curves for Bridge Abutment-Backfill Systems Anoosh Shamsabadi and Liping Yan Development of Innovative Foundation Systems to Optimize Seismic Behavior of Bridge Structures Lijun Deng, Emrah Erduran, Jose Ugalde, Sivapalan Gajan, Sashi Kunnath, and Bruce Kutter Factors that Affect the Performance of Bridge Foundations Undergoing LiquefactionInduced Lateral Spreading Christian Ledezma and Jonathan D. Bray Proposed Changes to AASHTO LRFD Bridge Design Specifications for the Seismic Design of Retaining Walls Donald G. Anderson, Geoffrey R. Martin, I. P. Lam, and J. N. Wang Seismic Soil-Foundation Investigation of the Brooklyn Bridge M. K. Yegian, S. Arzoumanidis, K. Kishore, J. Patel, S. K. Jain, B. P. Strohman, and N. Edwards Seismic Response of a Typical Highway Bridge in Liquefiable Soil HyungSuk Shin, Pedro Arduino, Steven L. Kramer, and Kevin Mackie Sensitivity Study of an Older-Vintage Bridge Subjected to Lateral Spreading Scott J. Brandenberg, Pirooz Kashighandi, Jian Zhang, Yili Huo, and Minxing Zhao Soil-Structure Interaction Analysis of Bridge Columns Supported on CISS Piles Pedro F. Silva and Majid T. Manzari Geoscience and Geotechnical Aspects of Recent Earthquakes Robert C. Lo and Yumei Wang Effect of Backfill Soil Type on Stiffness and Ultimate Capacity of Bridge Abutments A. Bozorgzadeh, S. A. Ashford, and J. I. Restrepo Seismic Behavior of 2D Topographic Features Subjected to Vertically Propagating Incident SV at High Frequencies Arash Razmkhah, Mohsen Kamalian, and Hamid Alielahi Dams and Levees Characterizing the Earthquake Ground Shaking Hazard in the Sacramento-San Joaquin Delta, California Ivan Wong, Patricia Thomas, Jeffrey Unruh, Kathryn Hanson, and Robert Youngs Damage Assessment and Seismic Modeling of Dams in Connection with the 2006 Hawaii Earthquakes Horst G. Brandes, Peter G. Nicholson, and Ian N. Robertson Deformation Analysis for Seismic Retrofit of an Embankment Dam Vlad Perlea, David Serafini, Ethan Dawson, and Michael Beaty Dynamic Behavior for Lightweight Spillway with Geosynthetics on Small Earth Dam Toshinori Kawabata, Kazunori Uchida, Tomohiro Kitano, Koji Watanabe, and Yoshiyuki Mohri Earthquake-Induced Deformations of Partially Saturated Embankments Rolando P. Orense, Masayuki Hyodo, Norimasa Yoshimoto, and Junya Ohashi Effect of Heterogeneous Soil Strength on the Seismic Residual Displacement of Embankments Yoshiya Hata, Koji Ichii, Takashi Tsuchida, Seiji Kano, and Norihiko Yamashita Geotechnical Investigations and Site Characterization of the Success Dam Seismic Remediation Project David C. Serafini and Mathew G. Allen Motion Characteristics of Compacted Earth Dams under Small Earthquake Excitations in Taiwan Jin-Hung Hwang, Chia-Pin Wu, and Jui-Te Chou Nonlinear Dynamic SSI Analyses of a Concrete Water Reservoir Wolfgang Roth, Bei Su, Ethan Dawson, Allan Porush, Meang Hassel, Lynn Shutt, and Mohsen Beikae Seismic Characterization and Its Limited Implication for San Pablo Dam Yoshi Moriwaki, Andrew Dinsick, John Barneich, Guilaine Roussel, Atta Yiadom, Fred Starr, and Phalkun Tan Seismic Deformation Analyses of the New Coquitlam Dam Li Yan, Alex Sy, and T. Thavaraj Seismic Rehabilitations of Miyun Reservoir Lei Fu Seismic Vulnerability of the Sacramento-San Joaquin Delta Levees Said Salah-Mars, Arulnathan Rajendram, Ram Kulkarni, Martin W. McCann, Jr., Segaran Logeswaran, Kanagalingam Thangalingam, Ralph Svetich, and Sean Bagheban Using ShakeMap and ShakeCast to Prioritize Post-Earthquake Dam Inspections William A. Fraser, David J. Wald, and Kuo-Wan Lin Walnut Canyon Dam Seismic Performance Evaluation John Barneich, Yoojoong Choi, David Shen, Yoshi Moriwaki, and Phalkun Tan Wavelet Signal Processing Technique in Analyzing Earthquake Records of Masjed Soleyman Embankment Dam M. Davoodi and M. Amel Sakhi Embankments and Slopes Centrifuge Modeling of Earthquake-Induced Failure Process of Soil Slopes Ga Zhang, Jiyun Qian, and Jian-Min Zhang Constructing Hillside Ozone Facilities in a High Seismic Zone M. Hassel, A. Woo, and M. Beikae Displacement-Based Seismic Stability Analyses of Reinforced and Unreinforced Slopes Using Planar Failure Surfaces Deepankar Choudhury and Deepa Modi Energy-Based Evaluation of Earthquake-Induced Slope Failure and Its Application Takaji Kokusho and Tomohiro Ishizawa Failure Mechanisms of Landfills under Dynamic Loading Varvara Zania, Yiannis Tsompanakis, Prodromos Psarropoulos, and Achilleas Papadimitriou Validation of Generic Municipal Solid Waste Material Properties for Seismic Design of Landfills Adda Athanasopoulos-Zekkos, Dimitrios Zekkos, and Neven Matasovic Pipelines Assessing Geotechnical Hazards for Water Pipes with Uniform Confidence Level Craig A. Davis Characteristics of Uplifting Velocity of a Buried Pipe in Liquefied Ground Koji Ichii, Nobuyasu Seto, and Hiroshi Kidera Shake-Table Testing and FLAC Modeling of Liquefaction-Induced Slope Failure and Damage to Buried Pipelines Lei Qiao, Chang Yuan, Masakatsu Miyajima, and Endi Zhai Soil-Pipeline Interaction Behavior under Strike-Slip Faulting Da Ha, Tarek H. Abdoun, and Michael J. ORourke Ports Theme Paper—Seismic Performance and Design of Port Structures Susumu Iai, Tetsuo Tobita, and Yukio Tamari Comparison of Panama Wharf Performance Using Numerical Analysis and Limit Equilibrium Methods King H. Chin, Daniel W. Mageau, and Scott T. Peterson Full-Scale Lateral Pile Load Test in Rock Fill Yohsuke Kawamata, Scott A. Ashford, and Nontapat Nimityongskul Geotechnical Considerations and Soil-Structure Interaction: Proposed ASCE Standards for Seismic Design of Piers and Wharves Arul K. Arulmoli, Gayle S. Johnson, Peter Yin, Omar A. Jaradat, and Timothy W. Mays Integrating Soil-Structure Interaction Analyses of Pile-Supported Wharfs in Seismic Risk Management of Port Systems Varun and Dominic Assimaki Seismic Retrofit and Improvement of Alpha-Bravo Wharves in Guam (Raj) S. Varatharaj, Arul K. Arulmoli, Dick Chan, Kijun Ahn, and Ukrit Siriprusanan Tunnels and Other Underground Structures Keynote—Centrifuge Testing of the Seismic Performance of a Submerged Cut-andCover Tunnel in Liquefiable Soil Bruce L. Kutter, Jui-Ching Chou, and Thaleia Travasarou Theme Paper—Earthquake Engineering for Tunnels and Large Underground Structures: A Case History Ignacio Arango Cut-and-Cover Structures: Seismic Response and Design Ching L. Wu, Farhang Ostadan, Wen S. Tseng, and James Chai Damage of New Sanyi Railway Tunnel during the 1999 Chi-Chi Earthquake Chih-Chieh Lu and Jin-Hung Hwang Seismic Analyses for the Fourth Bore of Caldecott Tunnel Chien-Tai Yang, Hubert Law, and Anoosh Shamsabadi Seismic Analyses of the Bay Tunnel Yiming Sun, Steve Klein, John Caulfield, Victor Romero, and Johanna Wong Seismic Response Analyses for the Silicon Valley Rapid Transit Project Peter Chiu, Daniel E. Pradel, Annie On-Lei Kwok, and Jonathan P. Stewart Development and Verification of a Pseudo-Static Solution for Evaluation of SeismicInduced Deformations of Rectangular Tunnels Hongbin Huo Other Topics in Geotechnical Earthquake Engineering and Soil Dynamics Keynote—Performance-Based Earthquake Engineering: Opportunities and Implications for Geotechnical Engineering Practice Steven L. Kramer Full-Scale Laboratory Tests Using a Shape-Acceleration Array System T. Abdoun, V. Bennett, R. Dobry, S. Thevanayagam, and L. Danisch Recent Improvements in MOC for Earthquake Response Richard P. Ray Some Characteristics of Ground Vibration as Induced by High-Speed Trains Yit-Jin Chen, Yi-Jiun Shen, Kuo-Yen Chen, and Shih-Ming Chang Geotechnical Earthquake Engineering and Soil Dynamics IV GSP 181 © 2008 ASCE Nonlinear Seismic Ground Response Analysis: Code Usage Protocols and Verification against Vertical Array Data Jonathan P. Stewart1, M. ASCE and Annie O.L. Kwok2, M. ASCE 1 Professor and Vice Chair, Dept. of Civil & Environmental Engr., Univ. of Calif., Los Angeles, 5731 Boelter Hall, Los Angeles, CA 90095; firstname.lastname@example.com 2 Project Engineer, Praad Geotechnical, Inc., 5465 S. Centinela Avenue, Los Angeles, CA 90066; firstname.lastname@example.com ABSTRACT: One-dimensional seismic ground response analyses are often performed using equivalent-linear procedures, which require few, generally well-known parameters. Nonlinear analyses have the potential to more accurately simulate soil behavior, but their implementation in practice has been limited because of poorly documented and unclear parameter selection and code usage protocols as well as inadequate documentation of the benefits of nonlinear modeling relative to equivalent linear modeling. Regarding code usage/parameter selection protocols, the following are described: (1) when input motions are from ground surface recordings, we show that the full outcropping motion should be used without converting to a "within" condition; (2) Rayleigh damping should be specified using at least two matching frequencies with a target level equal to the small strain soil damping; (3) the "target" soil backbone curves used in analysis can be parameterized to capture either the soil's dynamic shear strength when large-strain soil response is expected (strains approaching 1%), relatively small-strain response (i.e., < 0.3%) as inferred from cyclic laboratory tests, or a hybrid of the two; (4) models used in nonlinear codes inevitably represent a compromise between the optimal fitting of the shapes of backbone and hysteretic damping curves, and we present two alternatives for model parameterization. The parameter selection and code usage protocols are tested by comparing predictions to data from vertical arrays. We find site amplification to be generally underpredicted at high frequencies and overpredicted at the elastic site period, where a strong local resonance occurs that is not seen in the data. We speculate that this bias results from over-damping. INTRODUCTION Nonlinear ground response analysis is seldom used in practice by non-expert users because parameter selection and code usage protocols are poorly documented and understood, the effect of parametric variability on the analysis results is generally unknown, and the benefits of nonlinear analysis relative to the widely-used equivalent-linear analysis are generally unquantified and unclear. We report results of a Page 1 Geotechnical Earthquake Engineering and Soil Dynamics IV GSP 181 © 2008 ASCE benchmarking project for nonlinear ground response analysis codes organized through the Pacific Earthquake Engineering Research (PEER) center Lifelines program (Stewart et al. 2007). The objective of the project was to "de-mystify" nonlinear ground response analysis routines for practicing engineers by providing clear and well documented code usage protocols, to verify the codes as implemented with the usage protocols against vertical array data, and to investigate the differences between predictions provided by nonlinear and equivalent-linear analyses. This paper provides an overview of the principal results of benchmarking project. The topics covered include the following: 1. Suppose that ground response analyses are to be performed using a given control motion accelerogram. We address whether that motion should be used as-recorded of if it should be modified to a "within" condition. 2. Most nonlinear codes utilize Rayleigh damping so that a finite level of damping is present regardless of the backbone curve. We address the manner by which Rayleigh damping should be specified. 3. Material behavior is described by a nonlinear backbone curve along with rules for constructing unloading and reloading rules (e.g. Masing's rules). We review the parameters describing the backbone curve and provide guidelines for evaluating those parameters given the information typically available from geotechnical site investigations. Issues related to the simultaneous matching of modulus reduction and damping curves are also discussed. 4. Using available vertical array data, nonlinear codes are applied using recorded downhole motions along with the code usage protocols from (1)-(3). We evaluate residuals between recorded and calculated ground surface motions to assess the codes' performance. 5. The results from (4), along with additional simulations run at stronger levels of shaking, are compared to similar results from equivalent-linear analysis to investigate differences between results provided by the two methods of analysis. Issues (1)-(2) are presented in detail by Kwok et al. (2007) and hence are discussed here only briefly. NONLINEAR TIME DOMAIN METHODS OF ANALYSIS Equivalent-linear methods of analysis, which operate in the frequency domain, use for each layer of the site time-invariant soil properties (shear modulus G and soil hysteretic damping ). Time-domain analysis methods allow soil properties within a given layer to change with time as the strains in that layer change. Modified frequency-domain methods have also been developed (Kausel and Assimaki, 2002; Assimaki and Kausel, 2002) in which soil properties in individual layers are adjusted on a frequency-to-frequency basis to account for the strong variation of shear strain amplitude with frequency. Since the frequencies present in a ground motion record vary with time, this can provide a reasonable approximation of the results that would be obtained from a truly nonlinear, time-stepping procedure. Nonetheless, the present focus is on true, time-stepping procedures. Page 2 Geotechnical Earthquake Engineering and Soil Dynamics IV GSP 181 © 2008 ASCE The method of analysis employed in time-stepping procedures can in some respects be compared to the analysis of a structural response to input ground motion (Clough and Penzien, 1993; Chopra, 2000). As shown in Figure 1, the layered soil column is idealized either as a multiple degree of freedom lumped mass system or a continuum discretized into finite elements with distributed mass. Whereas frequency-domain methods are derived from the solution of the wave equation with specified boundary conditions, time domain methods solve a system of coupled equations that are assembled from the equation of motion. Table 1 summarizes the manner in which mass is distributed and nonlinear behavior is simulated FIG. 1. (a) lumped mass system; for the five nonlinear codes (b) distributed mass system considered here. The system of coupled equations is discretized temporally and a time-stepping scheme such as the Newmark method is employed to solve the system of equations and to obtain the response at each time step. TESS utilizes an explicit finite difference solution of the wave propagation problem that is the same as the solution scheme used in FLAC developed by HCItasca. Unlike in frequency-domain analysis where the control motion could be specified anywhere within the soil column, in time domain analysis the control motion must be specified at the bottom of the system of lumped masses or finite elements. Table 1. Mass representation and constitutive models used in nonlinear codes Nonlinear Code Mass Representation Constitutive Model D-MOD_2 Lumped Mass MKZ (Matasovic and Vucetic , 1993) DEEPSOIL Lumped Mass Extended MKZ (Hashash and Park, 2001) OpenSees Distributed Mass Multi-yield surface plasticity (Ragheb, 1994; Parra, 1996; Yang, 2000) SUMDES Distributed Mass Bounding surface plasticity (Wang, 1990) and other models TESS Distributed Mass HDCP (EPRI, 1993) Page 3 Geotechnical Earthquake Engineering and Soil Dynamics IV GSP 181 © 2008 ASCE NONLINEAR CODE USAGE AND PARAMETER SELECTION PROTOCOLS Specification of Input Motion Input motions are specified at the bottom of the 1D site profile in nonlinear analyses. There has been confusion regarding whether the motions specified at the base of the profile should represent an outcropping condition (i.e., equivalent free-surface motions that are twice the amplitude of the incident wave due to full reflection) or a within condition (i.e., the sum of the incident waves and downward propagating waves reflected from overlying layer interfaces). A closely related question is whether the base condition (representing the material below the site column) should be elastic or rigid. For some of the codes used in this research, past practice had been to calculate within motions at the profile base using equivalent-linear analyses, and specify those motions as the input for nonlinear analysis along with an elastic base. For other codes, full outcropping motions were used with an elastic base. Input W ithin A cc. O utcropping from Surface A cc.(g) SH A K E04 (g) A cc.(g) SHAKE04 Nonlinear Code (Outcropping Motion as Input + Elastic Base) Nonlinear Code (Within Motion as Input + Elastic Base) Nonlinear Code (Within Motion as Input + Rigid Base) Nonlinear Code (Outcropping Motion as Input + Rigid Base) 0.2 (a) 0 -0.2 0.2 (b) 0 -0.2 0.2 Frequency = 2.5 Hz (c) 0 -0.2 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6 6.5 Tim e (s) FIG. 2. Acceleration histories for the one-layer problem (Kwok et al. 2007) To clarify this issue, we exercised nonlinear codes for cases with known elastic solutions. An illustrative example of those calculations is a single soil layer (thickness = 30 m; Vs = 300 m/s) overlying an elastic half-space with Vs = 600 m/s. All soil properties were taken as elastic, and viscous damping was set to zero (i.e., the nonlinear codes Page 4 Geotechnical Earthquake Engineering and Soil Dynamics IV GSP 181 © 2008 ASCE were used with linear backbone curves). A sinusoidal acceleration history matching the site frequency of 2.5 Hz was specified at the top of the halfspace for time domain analyses. The same motion was specified as outcropping for linear frequency domain analyses (SHAKE04, Youngs, 2004). Figure 2 (bottom frame) shows the input acceleration history, while the middle frame shows the resulting within motion at the layer interface from frequency-domain analyses. Since the 2.5 Hz motion has a node (i.e., zero amplitude at all times) at the interface depth, the within motion decays to null upon achieving a steady state condition. As shown in Figure 2 (top frame), surface acceleration histories obtained from both frequency and time domain analyses match well. These and other similar results suggest that input motions should be specified for an outcropping condition in time domain analyses, and used with an elastic base. Other work has similarly shown that within motions can be used with a rigid base, which would be appropriate practice for applying recorded downhole motions in time domain analyses (Kwok et al., 2007). Specification of Viscous Damping Viscous D am ping R atio In most nonlinear codes, some form of viscous damping is used to provide for damping in the analysis at very small strains where the hysteretic damping from the non-linear soil models is nearly zero (an exception is TESS, which does not require viscous damping). There are a number of options for modeling viscous damping. As illustrated in Figure 3, there are three principal issues: (1) the form of the damping formulation (simplified versus full or extended Rayleigh damping; Park and Hashash, 2004); (2) the target viscous damping ratio (labeled tar in Figure 3) that is matched at specified target frequencies; and (3) the matching frequencies (one, two, and four for simplified, full, and extended Rayleigh damping, respectively). The current versions of all the aforementioned codes except TESS allow use of simplified and full Rayleigh damping. Extended Rayleigh damping is available in DEEPSOIL. TESS does not use Rayleigh damping, instead utilizing unload-reload rules that provide hysteretic damping even at small strains. Simplified Rayleigh Damping Full Rayleigh Damping Extended Rayleigh Damping tar f1 f2 f3 f4 Frequency FIG. 3. Illustration of viscous damping models (after Park and Hashash, 2004) Page 5 Geotechnical Earthquake Engineering and Soil Dynamics IV GSP 181 © 2008 ASCE Few protocols are available for guiding users in the selection of the model-type and parameters described above. One set of guidelines has been presented by Park and Hashash (2004) in which the model parameters are selected through an iterative process in which frequency and time domain elastic solutions are matched over a frequency range of interest (because frequency domain analyses using equivalent viscous damping provide a "correct" response against which the viscous damping formulation for the time domain can be calibrated). The procedure is implemented through a user interface. Kwok et al. (2007) compared results of linear time domain analyses for three site profiles to solutions from linear frequency domain analyses with a specified amount of equivalent viscous damping (fixed at 5%). The three selected sites represent a broad range of site conditions: shallow stiff soil over rock, soft clay overlying stiffer sediments and rock, and very deep soils typical of the Los Angeles basin. A representative example of these results is shown in Figure 4 for a deep soil site (La Cienega). In Figure 4, the red spectrum (equivalent linear) represents the "correct" result to which the time domain results are compared. Equivalent-linear analyses are exact in this case because the analyses are linear visco-elastic. 1.2 Input Outcropping Surface (SHAKE04) 1 Sa (g) 0.8 0.6 Surface (DEEPSOIL, Simplified, fs, tar =5%) Surface (DEEPSOIL, Simplified, fp, tar =5%) Surface (DEEPSOIL, Full, fs+9*fs, tar =5%) Surface (DEEPSOIL, Full, fs+9*fs, tar =0.5%) 0.4 0.2 0 0.01 0.1 1 10 Period (sec) FIG. 4. Comparison of response spectra for La Cienega. Results are shown for DEEPSOIL, but similar results were obtained for D-MOD_2 and OPENSEES. The principal results of these simulations, most of which are illustrated in Figure 4, are as follows: • Full Rayleigh damping is preferred to simplified. Figure 4 shows examples of significant misfit in the simplified Rayleigh damping results – a low matching frequency (fs=site frequency) produces overdamping while a high matching frequency (fp=predominant frequency of input motion) produces underdamping. The point is that a good match over a wide frequency range is generally not possible with a simplified Rayleigh damping model. The full Rayleigh damping result in Figure 4 (blue line) is based on matching frequencies iterated on to Page 6 Geotechnical Earthquake Engineering and Soil Dynamics IV • • GSP 181 © 2008 ASCE optimize the fit per the Park and Hashash (2004) procedure; it is seen that the second matching frequency is able to significantly improve the fit. The target damping level should match the small-strain soil damping (5% in Figure 4). The use of a much smaller damping value has been advocated by some users. As shown in Figure 4 (result for 0.5%, pink spectrum) produces underdamping. For applications where a non-iterative procedure is desired for specification of full Rayleigh damping target frequencies, the site frequency and five times the site frequency will usually suffice (not illustrated in Figure 4). Parameterization of Nonlinear Material Behavior Backbone Curve Figure 5 shows a typical nonlinear backbone curve for a soil element, which has a hyperbolic shape defined by initial small strain secant shear modulus (Gmax) and shear strength ( ff). The classical definition of reference strain is the ratio ref = ff /Gmax (Hardin and Drnevich, 1972). The parametric description of the nonlinear backbone curve in the past has generally required the specification of this reference strain along with a number of curve fitting parameters. A practical problem with this approach is that the shear strength at rapid strain rate, needed to define FIG. 5. Schematic illustration reference strain, is often not available. Another of backbone curve used for problem is that the shape of the backbone curve at nonlinear ground response small strains may be inconsistent with laboratory l test data. At least for problems involving low to moderate strain levels, a "pseudo-reference strain" ( r) can be used in lieu of the strength-based reference strain. The term pseudo-reference strain is used to avoid confusion with reference strain as defined by Hardin and Drnevich (1972). Pseudo reference strain is defined from a laboratory modulus reduction curve as the shear strain at which G/Gmax = 0.5. This definition arises from hyperbolic fits of G/Gmax curves according to G / Gmax = 1 1+ ( r) a (1) where and a are fitting parameters generally taken as 1 and 0.92, respectively (Darendeli, 2001). The advantages of using pseudo reference strain are that (1) r can be readily evaluated from material-specific modulus reduction curves evaluated from laboratory testing and (2) lacking material-specific testing, empirical relationships exist to predict r as a function of basic parameters such as PI, overburden stress, and overconsolidation ratio (Darendeli, 2001; Zhang et al., 2005). Page 7 Geotechnical Earthquake Engineering and Soil Dynamics IV GSP 181 © 2008 ASCE Because pseudo reference strains are determined from modulus reduction curves that are typically defined for strains less than 1%, a backbone curve described by a hyperbolic curve fit using r would not necessarily be expected to accurately represent soil behavior at large strain, including the shear strength. We investigate this problem by examining the degree to which the shear strength implied by the use of Eq. 1 (approximately Gmax × r) is realistic. This is done using ratios of Gmax to shear strength, for which empirical relationships are available from Weiler (1988). The ratios from Weiler are for soils with OCR=1-5, confining pressures = 100-500 kPa and PI=15-45. Weiler's undrained shear strengths (Su) are based on direct simple shear testing. Weiler's Gmax / Su ratio is compared to the inverse of Darendeli's (2001) estimate of r (which is approximately the ratio of Gmax to the large-strain asymptote of the hyperbolic curve, taken as shear strength). As observed from Figure 6, the Gmax/effective-strength ratios implied by pseudo reference strain r are significantly higher than those from Weiler for an overburden =100 kPa. This bias implies that the shear strength implied by r is stress of underestimated by Darendeli's relationships at =100 kPa. This bias disappears at larger overburden pressures ( =500 kPa). Accordingly, at relatively shallow depths, the use of backbone curves derived from the pseudo reference strain parameter may overestimate the soil nonlinearity at large strains. FIG. 6. Comparison of Gmax/Su ratio from Weiler (1988) to inverse of pseudo reference strain (1/ r) from Darendeli (2001). Quantity 1/ r is approximately the ratio of Gmax to the shear strength implied by the use of pseudo reference strain for fitting nonlinear backbone curves. Recommendations for the evaluation of backbone curve parameters are given in a subsequent section following a discussion of material damping. Page 8 Geotechnical Earthquake Engineering and Soil Dynamics IV GSP 181 © 2008 ASCE Material Damping Masing's rules (Masing, 1926) and extended Masing rules (Vucetic, 1990; Pyke, 1979) are employed in nonlinear analysis in conjunction with the backbone curve to describe unloading, reloading and cyclic degradation behavior of soil. Material damping is directly proportional to the area contained within a cyclic stress-strain loop, and hence is sensitive to the shape of the backbone curve and unload/reload rules. The damping at large strain that results from the use of Masing or extended Masing rules tends to be over-estimated relative to laboratory measurements. There are three schools of thought on managing the over-estimation of damping. One approach is to select model parameters for the backbone curve (and hence modulus reduction curves) that optimally fit the target data and accept the resulting overestimation of damping using Masing's rules. A second approach is to select model parameters that optimize the fitting of modulus reduction and damping curves simultaneously (across the strain range of interest). The third approach is to introduce an additional parameter that changes the shape of the unload/reload curves so that both modulus reduction and damping curves can be fit simultaneously. Lo Presti et al. (2006) allows unloading and reloading curves to have a shape scaled from that of the backbone curve by a factor of n (for the original Masing criteria, n = 2). Lo Presti et al. provide recommendations for estimating n as a function of soil type, strain level and number of cycles for the motion. Wang et al. (1980) suggest an approach in which a damping correction factor is applied to the Masing rule damping. These unload/reload rules are not yet implemented in the nonlinear codes listed in Table 1, and hence this approach is not discussed further. Parameter Selection for Backbone Curves and Damping There are two basic elements to the specification of parameters describing the nonlinear backbone curve and damping. The first element is to select the target shape of the backbone curve (equivalently, the modulus reduction curve) and the damping curve. The second element is to select model parameters that describe the target relationships within a reasonable degree of approximation for the problem at hand. Element (1) – Target Curves: The ideal characterization would involve materialspecific cyclic testing across the strain range of interest. This testing would include characterization of the material's dynamic shear strength for large-strain problems. However, material specific testing is usually not available, requiring the nonlinear behavior to be described using published correlations relating soil index properties, stress state, and stress history to parameters describing modulus reduction and damping curves (e.g., Darendeli, 2001; Zhang et al., 2005). Those relationships are usually well defined to shear strains of approximately 0.3-0.7%. This is illustrated in Figure 7, which shows the modulus reduction-strain values in the database used by Darendeli (2001). As described previously, those relationships do not typically provide an adequate representation of the shear strength. Guidelines for undrained shear strength evaluation and estimation are given in Ladd (1991); those estimates should be adjusted in consideration of rate effects, as described for example by Sheahan et al. (1996). Page 9 GSP 181 © 2008 ASCE G /G m ax Geotechnical Earthquake Engineering and Soil Dynamics IV ShearStrain (% ) FIG. 7. Modulus-reduction-strain values in the database used by Darendeli (2001) For problems involving large strain soil response, traditional practice has been to use a hyperbolic stress-strain curve (Eq. 1) with the strength-based reference strain. However, as shown in Figure 8, because of the misfit of reference strain and pseudo reference strain, this approach provides a poor match to small-strain modulus reduction behavior from laboratory tests. Accordingly, we recommend an alternative approach illustrated in Figure 8 and explained in the following: (1) use cyclic test results or correlation relationships to define the shape of the backbone curve to strain level 1 (typically taken as 0.1-0.3%); (2) estimate the material shear strength ( ff) for simple shear conditions with appropriate adjustment for rate effects; (3) estimate modulus reduction ordinates between strain 1 and the shear strength with the following hyperbolic relationship: 1 G /G 1 = (applies for > 1 only) (2) 1+ G 1 ( 1 ) / ff where G 1=secant shear modulus from Step (1) at = 1. An example application of this procedure is given by Chiu et al. (2008). At present, only OpenSees allows the input of the G/Gmax curve ordinates so that this formulation could be directly applied. ShearStress (kPa) 1 G /G m ax 0.8 0.6 0.4 0.2 1 0 0.0001 0.001 0.01 0.1 1 10 40 30 20 Ps. Ref. Strain Ref. Strain with ff/ v'=0.28 Adjusted 10 1 0 0.0001 0.001 0.01 0.1 1 10 Shear Strain (% ) Shear Strain (% ) FIG. 8. Modulus reduction and stress-strain curves implied by pseudo reference strain from Darendeli (2001), reference strain model, and proposed procedure (PI=20, OCR=1, v'= 100 kPa, Vs=135 m/s) Page 10 Geotechnical Earthquake Engineering and Soil Dynamics IV GSP 181 © 2008 ASCE Element (2) – Approximation of Target Curves: As noted above, an exact match of target curves is not possible when Masing rules or extended Masing rules are used to describe the unload-reload relationship. Until nonlinear codes implement the capability to simultaneously match both modulus reduction and damping curves, mis-match of one or both of these curves is unavoidable. As mentioned previously, one approach is to match the target modulus reduction curve as accurately as possible and accept the misfit of damping. Another is to optimize the fit of both simultaneously. We have worked with Hashash and Phillips (pers. comm., 2006) to devise a scheme to search for model parameters to achieve the aforementioned fitting approaches (in addition, the scheme allows optimization of the fitting of the damping curve only, although this approach is usually not considered). The scheme requires the specification of target material curves at (user-) predetermined strain levels. The fitting error is considered up to a maximum strain level (usually between 0.1 and 1%). The best combination of model parameters would be the one that gives the least error between the target curves and model curves. This error is quantified as: = ( wG / Gmax × where G / Gmax G / Gmax and )2 + (w × )2 (3) represent the mean error for the fitting of modulus reduction and damping curves respectively. Error term G / Gmax ( = G / Gmax ( i) ) G / Gmax is calculated as: 2 (4) N The numerator in Eq. 4 is the summation of fitting error from the lowest specified strain level to the maximum strain level. N is the number of strain levels included in the is calculated in a similar way as for G / Gmax . Terms wG / Gmax summation. Error term and w in Eq. 3 are weight factors whose values depend on the choice of fitting approach. Table 2 summarizes the values of weight factors under different fitting approaches. Figure 9 shows the difference in the fitted modulus reduction and damping curves (relative to target data) when different fitting approaches are employed. Table 2. Weight criterion for different fitting approaches Fitting Approach Weight Criterion MR wG / Gmax = 1; w = 0 MRD ( wG / Gmax ) 2 + ( w ) 2 = 1 1, wG / Gmax w D max > 25% 0.25 max , 10%< max < 25% 0.15 2, max < 10% = 1+ wG / Gmax = 0; w = 1 Page 11 Geotechnical Earthquake Engineering and Soil Dynamics IV GSP 181 © 2008 ASCE 1 G /G m ax 0.8 0.6 0.4 0.2 D am ping (% ) 0 30 20 Target - Lab Data Optimizing MR fit only ("MR" Fit) Trade off between MR and damping fits ("MRD" Fit) Optimizing damping only ("D" Fit) 10 0 0.0001 0.001 0.01 C yclic Strain (% ) 0.1 1 FIG. 9. Different approaches in fitting modulus reduction and damping curves in nonlinear analysis To illustrate how different fitting approaches may influence ground motion predictions, nonlinear ground response analyses are performed for two strong motion sites with different fitting of target curves. The two sites are Apeel 2 in Redwood City, which is a soft clay site consisting of Bay Mud, and Sepulveda VA hospital in Los Angeles, which is a relatively stiff soil site. The calculations were performed using the DEEPSOIL code. The target nonlinear modulus reduction and damping curves were taken as Seed and Idriss (1970) upper bound for modulus reduction and lower bound for damping in shallow sand layers, EPRI (1993) deep curves (251-500 ft) for deep sand (depth > 60 m), Sun et al. (1988) for Bay Mud at Apeel 2, and Vucetic and Dobry (1991) for other clayey soils. Scaled versions of an outcropping broadband synthetic motion (Silva, pers. comm., 2004) are used as input. Figure 10 shows predicted ground surface motions for Apeel 2 and Sepulveda, respectively. It is observed that when the input motion is relatively low-amplitude (about 0.2 g), predictions for all three fitting approaches are similar. When the shaking is relatively strong (about 0.7 g), predictions for the "MR" fitting approach are smaller than those from the other approaches, which is due to the larger high-strain damping ratio associated with the "MR" fitting approach. Another observation is that the soft site is more sensitive to the different fitting approaches than the stiff site. This occurs because the softer site has larger strains for a given input motion amplitude. Page 12 Geotechnical Earthquake Engineering and Soil Dynamics IV SoftC lay Site:A peel2 PHAr = 0.17g 0.6 0.4 PHAr = 0.17g 0.8 0.6 0.2 0 2.4 0 2.4 PHAr = 0.68g 2 1.6 1.2 1.2 0.8 0.4 0.4 0.1 1 Period (s) 10 PHAr = 0.68g 1.6 0.8 0 0.01 Input Motion "MR" Fitting "MRD" Fitting "D" Fitting 0.4 0.2 2 StiffSoilSite:Sepulveda 1 Sa (g) Sa (g) 0.8 Input Motion "MR" Fitting "MRD" Fitting "D" Fitting Sa (g) 1 Sa (g) GSP 181 © 2008 ASCE 0 0.01 0.1 1 10 Period (s) FIG. 10. Prediction results for soft clay site (Apeel 2) and stiff soil site (Sepulveda) with model curves obtained from different approaches to fitting modulus reduction and damping curves in nonlinear analysis VALIDATION OF CODE PREDICTIONS AGAINST VERTICAL ARRAY DATA Having developed the parameter selection protocols, it is necessary to test the effectiveness of those protocols by comparing code predictions to data. It is also important to study the uncertainties in predictions due to various sources of variability (material properties and modeling schemes). We utilize data from vertical array sites for this purpose. Four vertical array sites have been considered to date: Turkey Flat, California; La Cienega, California; KGWH02, Japan (Kiknet site); and Lotung, Taiwan. Analyses are preformed using an equivalent-linear procedure (SHAKE04) and the nonlinear codes listed in Table 1. We describe the results for the La Cienega site in some detail. Brief overviews of the principal findings from the other sites are then provided. La Cienega Site Site Model and Strong Motion Data We define "baseline" dynamic properties for the site along with a representation of material property variability. The baseline shear wave velocity (Vs) profile was developed from site-specific SASW and suspension logging data. Baseline modulus reduction and damping curves are derived from material-specific testing for 13 depth intervals. Log-normal, depth-dependent standard deviations on Vs are taken from an Page 13 Geotechnical Earthquake Engineering and Soil Dynamics IV GSP 181 © 2008 ASCE empirical model (Toro, 1997). Log-normal standard deviations on modulus reduction and damping curves are taken as the standard deviations of the Darendeli (2001) model residuals. Additional details on the selected soil properties are given in Stewart et al. (2007). Strong motion data are taken from a Mw=4.2 event that occurred 2.7 km from the site on 09/09/2001. Comparison of Model Predictions to Data Figure 11 shows 5% damped acceleration response spectra of the horizontal recorded surface motions and prediction results obtained using the baseline geotechnical model while Figure 12 compares the predicted acceleration histories with the recordings (DEEPSOIL predictions only). Residuals are calculated as: R(T ) = ln(S a (T ) )data ln(S a (T ) ) pre (5) where ln ( Sa (T ) ) data is the natural log of the recording's spectral acceleration at period T and ln ( S a (T ) ) pre is the natural log of the predicted spectral acceleration. 1.6 1.4 Downhole rock record (252.1 m) Surface Record (a) Surface-EW Sa (g) 1.2 (b) Surface-NS 1.0 0.8 0.6 0.4 0.2 Residual, R (ln units) 0.0 1.6 DEEPSOIL D-MOD_2 OpenSees SUMDES TESS SHAKE2004 (c) Surface-EW 1.2 0.8 0.4 (d) Surface-NS 0.0 -0.4 -0.8 0.01 0.1 Period (sec) 1 0.01 0.1 1 Period (sec) FIG. 11. Acceleration response spectra for data and simulation results compared through direct spectral ordinates and prediction residuals for ground surface. Results shown for two horizontal directions. Results shown to a maximum period of 1/(1.25´fHP), where fHP = high pass corner frequency. As shown in Figure 12, the general comparison of the acceleration histories to data is quite favorable, although there is some bias towards over-prediction of the largest pulses in the record in the EW direction and under-prediction in the NS direction. The error appears to be related to the shape of the pulses near their tips. Those errors in the acceleration histories translate into errors in spectra as well. For the Page 14 Geotechnical Earthquake Engineering and Soil Dynamics IV GSP 181 © 2008 ASCE A cc.(g) A cc.(g) A cc.(g) A cc.(g) EW component at the ground surface, predictions from codes DEEPSOIL and D-MOD_2 are similar to each other and are generally close to the data, although they are underpredicting at periods between 0.07 and 0.12 sec. Predictions from codes OpenSees and TESS have similar trends and are also close to the data, except for overprediction near the period of 0.15 sec. SUMDES is underpredicting at periods below 0.5 sec which is probably due to the use of a simplified Rayleigh damping formulation in the version of this code that was used. Close examination of the spectra and residuals reveals that predictions from all codes have bumps near T=2 sec, which corresponds to the elastic period of the site from the base recording to the ground surface. For the NS component at the ground surface, all nonlinear codes are underpredicting at periods below 0.5 sec. Although not shown here for brevity, similar misfits of predictions relative to data occur at depths of 18.3 m and 100.6 m. Surface - EW 0.2 0 Recorded Predicted by DEEPSOIL -0.2 0.2 252.1 m - EW 0 -0.2 Surface - NS 0.2 0 -0.2 0.2 252.1 m - NS 0 -0.2 5 10 15 Tim e (sec) FIG. 12. Acceleration histories for data and simulation results from DEEPSOIL for ground surface Contributions to the uncertainty in simulation results from model-to-model variability and material variability are considered. To evaluate model-to-model variability, we first take the median estimate ln (S a (T ) ) from the five nonlinear model predictions using baseline properties. Model variability, m, is then calculated from the variance as follows: Page 15 Geotechnical Earthquake Engineering and Soil Dynamics IV 2 m (T ) = Var ( S a (T ) ) pre = GSP 181 © 2008 ASCE ln ( S a (T ) ) pre ,i ln ( S a (T ) ) 2 i (6) N 1 where N = number of predictions (five) and ln ( S a (T ) ) pre ,i = natural log of predicted spectral acceleration from code i. Figure 13 shows the variation of m with period. Estimated standard deviation in prediction (ln unit) 1 0.9 0.8 0.7 Material Curve variability, G Velocity variability, v Model variability, m Overall variability, 0.6 0.5 Ts = 2.0 sec 0.4 0.3 0.2 0.1 0 0.01 0.1 1 Period (sec) FIG. 13. Standard deviation terms associated with geometric mean acceleration response spectral ordinates for ground surface. Ts = elastic site period. Variability in predictions from uncertain shear wave velocity and uncertain modulus reduction and damping curves is considered using only the DEEPSOIL code. To calculate the standard deviation due to velocity variability, ground motions are predicted based on two non-baseline velocity profiles (mean ± 3 standard deviation velocities). The standard deviation of the ground motions due to the variability in velocity (denoted v) is estimated according to the first-order second moment (FOSM) method (Baker and Cornell, 2003; Melchers, 1999) as follows: v 3 = i =1 wi (ln( S a (T )i ln( S a (T )) 2 (7) where Page 16 Geotechnical Earthquake Engineering and Soil Dynamics IV GSP 181 © 2008 ASCE Sa (T )1 = S a (T )Vs :µ Sa (T ) 2 = Sa (T )V :µ + 3 S a (T )3 = Sa (T )V :µ 3 s s ln( Sa (T )) = Vs (8) Vs 3 i =1 wi ln( Sa (T )i ) w1 = 2 / 3; w 2 = w 3 = 1/ 6 A F (T = 0.3 sec) 10 1 0.1 10 1 0.001 Recorded DEEPSOIL D-MOD_2 OpenSees 0.01 SUMDES TESS SHAKE2004 0.1 PH A r (g) A F (T = 2 sec) A F (T = 1 sec) A F (T = 0 sec) The standard deviation due to the variability in material curves (denoted G) is estimated similarly to v. Figure 13 shows the estimated standard deviation in prediction due to different sources of variability. For T < 0.4 sec, the model and material curve variability dominate while for T > 0.4 sec velocity variability is strongest. To study site response at different levels of input motion, site amplification factors are compiled from ground motions recorded at La Cienega from 1999-2005. Predicted amplification factors of geometric mean response spectral accelerations are derived at specified periods using the baseline geotechnical model for all codes. To estimate amplification factors for different amplitudes of input motions, the recording shown in Figure 12 is scaled down to various degrees. Figure 14 shows that the predicted amplification factors demonstrate a similar trend with respect to base motion peak acceleration (PGAr) as those observed from data. This suggests that nonlinearity is modeled well by nonlinear codes over this range of input motions. The level of predicted amplification is biased at multiple periods. For example, at the elastic site period (2 sec), the predicted amplification is larger than suggested by data. 1 10 1 10 1 0.001 0.01 0.1 1 PH A r (g) FIG. 14. Theoretical and observed amplification factors at the La Cienega site. Page 17 Geotechnical Earthquake Engineering and Soil Dynamics IV GSP 181 © 2008 ASCE Other Sites Three other vertical array sites were analyzed in a manner similar to La Cienega – Turkey Flat, KGWH02 (Kiknet), and Lotung. Results for all sites are given in Stewart et al. (2007). Results for the Turkey Flat site, which were originally provided as part of a blind prediction exercise, are also given in Kwok et al. (2008 – in press). For all sites except Turkey Flat, residuals for very low periods (reflecting PGA) are positive, indicating that the models are underpredicting high frequency components of ground motion. Near the elastic site period (Ts), the models produce a local "bump" in the spectrum that results in overprediction. At periods significantly greater than Ts, residuals disappear due to the lack of a significant site effect. The above misfits can have many sources. In general, there are two possible sources of misfit – error in the input data (velocity profiles or nonlinear curves) or error in the models and their parameter selection protocols. Errors in velocity profile were checked by comparing observed (small amplitude) shear wave travel time to the time implied the model. With the exception of the Kiknet site, these checks confirm the velocity profile used in the analysis. For Kiknet, observed travel times are less than model travel time, which may be due to waves entering from the side of the relatively narrow basin in which the site is located. Apart from velocity, other possible sources of error include incorrect modeling of material curves (modulus reduction and damping) or the presence of site response physics that cannot be captured by a 1D model. Because modulus reduction effects are likely relatively modest given the low strain levels excited by the subject earthquakes, error in the modeling in modulus reduction is not likely the source of the misfit. Given that site amplification is under-predicted for all three sites considered across a broad frequency range, a likely source of bias is overdamping in the models. This overdamping could reflect bias in the material damping curves or excessive Rayleigh damping. Further research is needed to resolve these possible sources of bias. We next discuss trends in the period-dependence of the standard deviation terms. In Figure 15, uncertainties in predictions due to different sources of variability are plotted as a function of period (left frame) and period ratio (right frame; period ratio = T/Ts, where Ts = elastic site period). Variability of predictions due to material curve uncertainty seems to be most pronounced at periods less than 0.5 sec and has no clear association with the site period. Moreover, material curve uncertainty only produces significant response variability for relatively thick site profiles – it is not a significant issue for Turkey Flat, which is a shallow soil site. The effect of velocity variability can have a strong influence on the predictions near the elastic site period. However, this strong influence is only observed for sites with large impedance contrast (Turkey Flat and KGWH02), which dominates the site response in those cases. This is shown in Figure 15 by a peak in the v term near T/Ts = 1.0. Such a peak does not occur for the Lotung or La Cienega sites, which have a gradual variation of velocity with depth and no pronounced impedance contrast. Model-to-model variability is most pronounced at low periods, where the differences result principally from different damping formulations. Given the modest ground motions at the investigated sites, it is expected that variations in the viscous damping Page 18 Geotechnical Earthquake Engineering and Soil Dynamics IV GSP 181 © 2008 ASCE formulations are principally driving this variability. As noted previously, predictions from SUMDES, which had only the simplified Rayleigh damping formulation at the time these predictions were made, are much lower than the predictions from codes with full Rayleigh damping formulation. This is a major contributor to the model-to-model variability at low periods. 0.8 0.6 0.4 0.2 0 1 0.8 0.6 0.4 0.2 0 1 Velocity Variability, (ln unit) V M aterialC urve Variability, G (ln unit) O verallVariability, (ln unit) 1 0.8 0.6 0.4 0.2 0 1 M odelVariability, (ln unit) m Turkey Flat Kiknet KGWH02 La Cienega Lotung 0.8 0.6 0.4 0.2 0 0.01 0.1 1 Period,T (sec) 10 0.001 0.01 0.1 1 10 100 Period R atio,T/Ts FIG. 15. Comparison of variabilities across four vertical array sites COMPARISON OF EQUIVALENT LINEAR AND NONLINEAR RESULTS The predictions of ground motions at vertical array sites described in the previous section were made using both equivalent-linear and nonlinear codes. The aforementioned comparisons of model predictions to data showed similar trends for Page 19 Geotechnical Earthquake Engineering and Soil Dynamics IV GSP 181 © 2008 ASCE both methods of analysis, although the positive residuals at short periods were generally smaller for equivalent-linear. More meaningful insight into the differences between equivalent-linear and nonlinear ground motion predictions can be made when the codes are exercised at relatively strong shaking levels that induce large strains. Representative results are shown in Figure 16, which shows for the La Cienega site geometric mean horizontal component predicted spectra, amplification factors (=surface/input outcropping spectral accelerations), and spectral shapes (Sa/PGA) for a low-strain condition (left side, which corresponds to observed motions during 2001 event) and a large-strain condition produced through the use of a large amplitude synthetic input motion (right side). The results shown in Figure 16 apply for the baseline geotechnical model described previously. Also shown for reference purposes are predictions of empirical models for amplification (middle frames; Choi and Stewart, 2005) and spectral shape (bottom frames; Campbell and Bozorgnia, 2007). The empirical amplification model is exercised for the site's Vs30 (260 m/s) and corresponding input PGA. The empirical spectrum from which spectral shape is evaluated is calculated using Mw=7.5, site-source distance=10 km, and strike-slip focal mechanism (for synthetic). Mw = 4.2, 09/09/2001 (PHAr = 0.19 g) DEEPSOIL D-MOD_2 OPENSEES SUMDES 1 0.5 3 2.5 Synthetic Motion (PHAr = 0.65 g) TESS SHAKE2004 Input Motion 2 1.5 1 0 2.5 0.5 0 2.5 2 2 1.5 1.5 1 1 0.5 0.5 0 4 0 4 3 3 2 2 1 1 SpectralShape AF Sa (g) 1.5 Choi and Stewart (2005) Campbell and Bozorgnia (2007) 0 0.01 0.1 1 Period (sec) 0 10 0.01 0.1 1 10 Period (sec) FIG. 16. Comparison of computed spectra, amplification factors, and spectral shapes of predicted motions at La Cienga site As shown in the bottom frames of Figure 16, the spectral shapes from equivalent-linear and nonlinear models are similar to each other for the 2001 input motion that induces relatively low strain but are significantly different for the large amplitude synthetic Page 20 Geotechnical Earthquake Engineering and Soil Dynamics IV GSP 181 © 2008 ASCE motion. For the large-strain simulation, the spectral shapes at low periods (< 0.2 sec) from equivalent linear analyses are flatter and have less period-to-period fluctuations than those from nonlinear analyses or empirical models. This aspect of equivalent-linear results is believed to be non-physical and can be overcome with nonlinear analysis. As shown in the middle frames, the flatness of the equivalent linear spectrum is associated with a dip in the amplification factors between periods of approximately 0.03 and 0.3 sec. That dip is less pronounced in the nonlinear codes, which produce amplification factor shapes more compatible with the empirical model. RECOMMENDATIONS AND CONCLUSIONS In this article, we present the principal findings of a large, multi-investigatory project directed towards establishing consensus guidelines for the use of nonlinear ground response analyses in engineering practice. Our intent is to make nonlinear analyses more accessible to engineering practitioners and enhance their usage for situations where it is justified. We recognize that the nonlinear codes considered here are one-dimensional, which has its own set of limitations for situations where the site response may be influenced by relatively complex basin geometry or topography. Nonlinear analyses may provide an improved estimate of ground motion relative to equivalent-linear when ground strains become "large." This can be judged for a given application by examining response spectra and amplification factors from equivalent-linear analysis – caution should be exercised if they exhibit a flat spectrum or a "hole" in the amplification factors at short periods. We speculate that this is caused by overdamping of high-frequency components of ground motion, which occurs principally early in the record (p-waves) when the amplitude of shaking (and material damping) are low. This certainly occurs when shear strains approach 1%, although in deep soil sites it has been observed to occur for peak strains as low as 0.2-0.3%. When nonlinear analyses are performed, the following guidelines are recommended for code usage and parameter selection: 1. Input motions should be used as-recorded (without modification). Outcropping recorded motions should be applied at the base of a site model with an elastic base. Downhole recorded motions should be applied with a rigid base. 2. For codes that require it, viscous damping should be specified using a full Rayleigh damping formulation with the target damping level tar=small strain soil hysteretic damping. The first matching frequency should be the site frequency. The second frequency should be selected so as to optimize the match of elastic frequency- and time-domain analysis for the site. A reasonable approximation for many applications is to take the second frequency as approximately five times the site frequency. 3. The target backbone curve for a site is best determined through material specific cyclic testing along with dynamic strength testing. If this is not available, the shape of the backbone curve at small- to modest-strains (up to approximately 0.1-0.3%) can be estimated using empirical relationships that take index properties, confining pressure, and stress history as input. Procedures to estimate undrained shear strength through stress Page 21 Geotechnical Earthquake Engineering and Soil Dynamics IV GSP 181 © 2008 ASCE normalization are well established (Ladd, 1991), but require modification for rate effects (e.g., Sheahan et al., 1996). 4. For problems involving small-strain response, target backbone curves can be defined using modulus reduction relationships without consideration of shear strength. For problems involving moderate to large strain response, a hybrid representation that accounts for the shape of the modulus reduction curve at small strains and shear strength at large strain is recommended (see Eq. 2 and Figure 8). 5. Ultimately it is hoped that procedures for simultaneously matching target modulus reduction and material damping curves will be implemented in nonlinear codes, but this is not currently available. At present, users can choose to match the modulus reduction curve only (MR fitting) or modulus reduction and damping curves simultaneously (MRD fitting). We recommend the use of both approaches for large strain problems to bound the solution. When applied to vertical array sites, these protocols generally produce reasonable results, although there is some indication of possible overdamping at high frequencies and overestimation of site amplification at the resonant frequency of the site model. Additional work to validate and further refine these procedures is ongoing by the project team. ACKNOWLEDGMENTS Financial support for the benchmarking of nonlinear ground response analysis procedures was provided by PEER Lifelines project 2G02, which is sponsored by the Pacific Earthquake Engineering Research Center's Program of Applied Earthquake Engineering Research of Lifeline Systems. The PEER Lifelines program, in turn, is supposed by the State Energy Resources Conservation and Development Commission and the Pacific Gas and Electric Company. This work made use of Earthquake Engineering Research Centers Shared Facilities supported by the National Science Foundation under Award #EEC-9701568. In addition, the support of the California Department of Transportation's PEARL program is acknowledged. This work would not have been possible without close collaboration with a number of code developers including Youssef Hashash, Neven Matasovic, Robert Pyke, Zhiliang Wang, and Zhaohio Yang. Their insights and spirit of collaboration are truly appreciated. This project has also benefited from the helpful suggestions of an advisory panel consisting of Drs. Yousef Bozorgnia, Susan Chang, Brian Chiou, Ramin Golesorkhi, I.M. Idriss, Erol Kalkan, Robert Kayen, Steven Kramer, Faiz Makdisi, Geoff Martin, Lelio Mejia, Tom Shantz, Walter Silva, and Joseph Sun. 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