Subsurface Investigation and Analysis of Bridges in Costa Rica Damaged by Lateral Spreading to Evaluate and Improve Design Procedures for Kinematic Loading of Piles
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Final Report for US Geological Survey Award No. G10AP00047 Subsurface Investigation and Analysis of Bridges in Costa Rica Damaged by Lateral Spreading to Evaluate and Improve Design Procedures for Kinematic Loading of Piles by Kyle M. Rollins and Kevin W. Franke 368 CB, Civil & Environmental Engineering Dept. Brigham Young University Provo, UT 84602 Performance Period: March, 1, 2010-Feb 28, 2011 Author Contact Information: Kyle Rollins: email: [email protected], phone: 801 422-6334, fax: 801 422-0159 Kevin Franke: email: [email protected], phone: 801 904-4097, fax: 801-904-4100 ABSTRACT The M7.6 earthquake that struck the Limon province of Costa Rica on April 22, 1991 killed 53 pe ople, injured another 193 pe ople, and disrupted an estimated 30-percent of the highway pavement and railways in the region due to fissures, scarps, and soil settlements resulting from liquefaction. Significant lateral spreading was observed at bridge sites throughout the eastern part of Costa Rica near Limon, and the observed structural damage ranged from moderate to severe. This study identified five such bridges where liquefaction-induced damage was either observed following the earthquake or is still visible to this day. A geotechnical investigation was performed at each of these five bridges in an attempt to back-analyze the soil conditions leading to the liquefaction and lateral spreading observed during the 1991 earthquake, and each of the five resulting case histories was developed and is summarized in this report. Modern analysis techniques for evaluating liquefaction triggering, lateral spreading displacements and kinematic pile response are summarized and evaluated against applicable Costa Rican case histories. In addition, a new performance-based kinematic pile response procedure based on t he probabilistic framework developed by the Pacific Earthquake Engineering Research Center (PEER) is presented. The procedure incorporates existing analysis methodologies familiar to most practicing geotechnical professionals including empirical computation of lateral spreading displacement and p-y soil spring methods for computing kinematic pile response. The performance-based pile response procedure is demonstrated on the applicable Costa Rican case histories, and deterministic procedures are evaluated against the probabilistic results where appropriate. The proposed objectives of this study were to (1) collect data and develop five new lateral spreading case histories from the 1991 Limon earthquake; (2) evaluate existing deterministic methods for computing lateral spreading displacements and kinematic pile response; and (3) apply principles of performance-based design to develop a new performance- based procedure for evaluating lateral spreading displacements and kinematic pile response. All of these objectives were successfully achieved, and the results, observations and conclusions are summarized in the following report. ACKNOWLEDGEMENTS This research was supported by the U.S. Geological Survey (USGS), Department of the Interior, under USGS award number G10AP00047 and this support is gratefully acknowledged. The views and conclusions contained in this document are those of the authors and should not be interpreted as necessarily representing the official policies, either expressed or implied, of the U.S. Government. We express gratitude to the Costa Rican Ministry of Transportation for allowing access to the bridge sites and for providing bridge plan and soil test data. We thank Insuma S.A. Geotechnical Consultants of San Jose, Costa Rica who performed the drilling, Standard Penetration (SPT) testing, and soil testing for each bridge site and David Anderson, Head Technician in the BYU Civil & Environmental Engineering Department who conducted the site surveys using high resolution GPS equipment. W e also express appreciation to Daniel Avila from the Utah Department of Transportation who conducted energy throughput measurements for the SPT testing and to Les Youd who served as a consultant on the study and reviewed the testing and analysis procedures at key points during the process. Finally, we express our appreciation to Norm Jones who helped develop the Monte Carlo macro used in conjunction with LPILE in this study. We express our gratitude to Kleinfelder Group, Inc. and URS Corporation who provided analysis software and spreadsheets for use in this study. TABLE OF CONTENTS LIST OF TABLES ....................................................................................................................... xi LIST OF FIGURES ................................................................................................................... xiii 1 Introduction ........................................................................................................................... 1 2 Liquefaction and Lateral Spreading ................................................................................... 2 2.1 Introduction ..................................................................................................................... 2 2.2 Liquefaction .................................................................................................................... 3 2.3 Liquefaction Susceptibility ............................................................................................. 3 2.4 Liquefaction Initiation .................................................................................................... 4 2.4.1 Flow Liquefaction and Estimating Steady State Strength .......................................... 4 2.4.2 Cyclic Mobility ........................................................................................................... 7 2.4.3 Evaluation of Initiation of Liquefaction...................................................................... 8 2.5 Lateral Spreading Displacement ................................................................................... 12 2.5.1 Experimental Studies of Lateral Spread ................................................................... 14 2.5.2 Methods for Predicting Lateral Spreading Displacements ....................................... 14 2.5.3 Youd et al. (2002) Procedure .................................................................................... 15 2.5.4 Bardet et al. (2002) Procedure .................................................................................. 18 2.5.5 Baska (2002) Procedure ............................................................................................ 19 2.6 Incorporation of Uncertainty in the Estimation of Lateral Spreading Displacements .. 21 2.7 Estimating Lateral Spreading Displacement versus Depth ........................................... 23 2.8 Depth Limitations when Developing Lateral Spreading Displacement Profiles .......... 26 3 Review of Kinematic Pile Response Analysis ................................................................... 28 vii 3.1 Introduction ................................................................................................................... 28 3.2 Computing Kinematic Pile Response ........................................................................... 28 3.3 P-Y Analysis Methodology .......................................................................................... 29 3.4 P-Y Development for Soil Layering ............................................................................. 31 3.5 Equivalent Single Pile for Kinematic Group Response ................................................ 34 3.5.1 Development of the Equivalent Single Pile .............................................................. 34 3.5.2 Resistance of the Pile Cap and Development of the Rotational Soil Spring ............ 35 3.6 Additional Discussion Regarding Kinematic Loading and the Pile Cap ...................... 38 4 Performance-Based Earthquake Engineering Design ..................................................... 41 4.1 Introduction ................................................................................................................... 41 4.2 Basic Philosophy of PBEE ........................................................................................... 41 4.3 Seismic Hazard Analysis .............................................................................................. 43 4.3.1 Estimating Earthquake Ground Motions using Attenuation Relationships .............. 43 4.3.2 Probabilistic Seismic Hazard Analysis ..................................................................... 44 4.4 Introduction to PEER PBEE Framework ...................................................................... 50 4.4.1 PEER PBEE Framework Variable Definitions ......................................................... 51 4.4.2 PEER PBEE Framework Equation ........................................................................... 51 5 Performance-Based Kinematic Pile Response .................................................................. 54 5.1 Assumptions of the Procedure ...................................................................................... 54 5.2 Soil Site Characterization ............................................................................................. 55 5.3 Characterization of Site Geometry/Topography ........................................................... 55 5.4 Characterization of Site Seismicity ............................................................................... 55 5.4.1 Liquefaction Triggering Analysis ............................................................................