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Investigation of the IBC Proposed Force Reduction Factor for Base Isolated Structures
Rafinazari, Amir | 2010
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- Type of Document: M.Sc. Thesis
- Language: English
- Document No: 40264 (53)
- University: Sharif University of Technology, International Campus, Kish Island
- Department: Science and Engineering
- Advisor(s): Rahimzadeh Rofooei, Fayaz
- Abstract:
- General strategies for seismic design of structure include increasing the rigidity and strength, increasing the energy absorption capacity by implementing energy dissipating devices and reducing the seismic demand by isolating the structure from its base. Isolation system provides the required ductility of the structural system by concentrating its displacements mainly on the isolator level, and separates the structure from the horizontal components of the ground motion. That would create a system whose its main frequency is much lower than the dominant frequency of the earthquake records and the natural frequency of the equivalent fixed-base structure. Because of growing tendency towards using these systems in recent years, different guidelines have been proposed to analyze and design these types of structures, such as ASCE 7-05, IBC and FEMA356. In spite of different studies that have been carried out in recent years on the performance of base isolation systems, more attempts is still needed to investigate the existing force reduction factor. In this study in addition to evaluation of the different types of base isolation systems and their fundamentals, the IBC proposed force reduction factor for base isolated structures is investigated by performing extensive nonlinear dynamic analysis of 3-D structural models designed with different R factors and different eccentricities under a variety of earthquake excitations. Column axial forces, storey shears, storey drifts and storey accelerations calculated to compare the response of different base isolated structures. For 3-D modeling and nonlinear dynamic time history analysis SAP2000 program is used.
- Keywords:
- Seismic Design ; Natural Frequency ; Strength Reduction Factor ; Nonlinear Dynamic Analysis ; Base Isolation
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- AUTHOR'S DECLARATION
- Abstract
- Acknowledgements
- Dedication
- Table of Contents
- List of Figures
- List of Tables
- CHAPTER 1 INTRODUCTION
- CHAPTER 2 BASE ISOLATION
- 2.1. Introduction
- 2.2. Overview on Creation and Development of Base Isolation Systems
- 2.3. Different Types of Isolation Systems
- 2.3.1. Rubber Bearing Systems
- 2.3.2. Laminated Rubber Bearing Systems
- 2.3.2.1. Low Damping Natural and Synthetic Rubber Bearings
- 2.3.2.2. High Damping Natural Rubber (HDNR)
- 2.3.3. NZ Systems
- 2.3.4. Friction Pendulum Systems
- 2.3.5. R- FBI Systems
- 2.3.6. EDF Systems (Electricite De France)
- 2.3.7. Sliding Resilient Friction (SR-F) Systems
- 2.3.8. Spring Systems (GERB)
- 2.4. Investigation on Technical Studies about Base Isolation Systems
- CHAPTER 3 ISOLATED STRUCTURES CODE PROVISONS
- 3.1. Introduction
- 3.2. Modeling
- 3.3. Seismic Design Level
- 3.4. Analysis Methods
- 3.4.1. Selecting Analysis Method
- 3.4.2. Equivalent Static Analysis
- 3.4.2.1. Properties of Isolation System
- 3.4.2.2. Minimum Lateral Displacement
- 3.4.2.3. Minimum Lateral Forces
- 3.4.2.4. Lateral Force Distribution in Structure Height
- 3.4.3. Response Spectrum Analysis
- 3.4.3.1. Design Spectrum
- 3.4.3.2. Modal Damping
- 3.4.3.3. Combination of Ground Motion Pairs
- 3.4.3.4. Results Scaling
- 3.4.4. Time History Analysis
- 3.4.4.1. Scaling Method
- 3.5. Required Isolation System Details
- 3.6. Determination of Force – Displacement Curve Properties of Isolation System
- CHAPTER 4 MODELING, ANALYSIS ASSUMPTIONS, ...
- CHAPTER 5 NONLINEAR TIME HISTOREY ANALYSIS RESULTS
- 5.1. Introduction
- 5.2. Comparison of Maximum Base Shears and Maximum Storey Shears
- 5.3. Comparison of Maximum Storey Drifts
- 5.4. Comparison of Maximum Uplift Forces in Corner Columns
- 5.5. Comparison of Maximum Storey Rotations
- 5.6. Comparison of Maximum Storey Absolute Accelerations
- 5.7. Comparison of Plastic Hinge Status
- CHAPTER 6 CONCLUTIONS AND FUTURE WORKS
- References
- Amir