Hyung-Jo Jung Sejong University, Korea

1. Fourth World Conference on Structural Control and Monitoring (4WCSCM) An MR Damper-based Control System Introducing Electromagnetic Induction Part Hyung-Jo JungSejong University, Korea Kang-Min Choi Korea Advanced Inst. of Science and Tech. Sang-Won Cho Korea Advanced Inst. of Science and Tech. In-Won Lee University of Western Ontario, Canada University of San Diego, July 11-13, 2006

2. OUTLINE • Introduction • Proposed Control System • Numerical Verification • Experimental Verification • Conclusions Dynamics and Smart Structures Lab., Sejong Univ., KOREA

3. INTRODUCTION • Background • Smart damping systems (i.e., semiactive control systems): • - reliability of passive systems; adaptability of active systems • - smart damping devices: variable stiffness damper, variable • friction damper, MR/ER damper, etc. • An MR damper-based control system is one of the promising smart damping systems, because of its mechanical simplicity, high dynamic range, low operating power requirements, environmental robustness, and so on. Dynamics and Smart Structures Lab., Sejong Univ., KOREA

4. INTRODUCTION • Conventional MR Damper-based System MR damper • A control system including sensors, a controller and an external power source • Difficult to install and maintain the conventional system, especially in the cases of large-scale structures such as high-rise buildings and long-span bridges

5. INTRODUCTION • Possible Solutions • Application of advanced technologies such as power harvesting and wireless sensor networks • Development of passively operated control systems with adaptability and high performance • Etc. One of the promising systems is the smart passive control system proposed by Cho et al. (2005). * S.W. Cho, H.J. Jung, and I.W. Lee, “Smart passive system based on magnetorheological damper,” Smart Mater. Struct., 14, 707-714, 2005.

6. INTRODUCTION • Objectives • To introduce a newly developed MR damper-based control system. • To numerically and experimentally verify the • effectiveness of the proposed control • system for seismic protection of building • structures.

7. MR Damper PROPOSED CONTROL SYSTEM • Conventional MR Damper-based Control System current power source command controller sensor Control System Dynamics and Smart Structures Lab., Sejong Univ., KOREA

8. MR Damper PROPOSED CONTROL SYSTEM • Proposed MR Damper-based Control System MR damper with Electromagnetic induction (EMI) system • An EMI system consists of permanent magnet and coils. • It changes the kinetic energy of the reciprocation motion of the MR damper to the electric energy according to the Faraday’s law of induction. induced current magnetic field damper deformation EMI system

9. PROPOSED CONTROL SYSTEM • Proposed MR Damper-based Control System MR damper with Electromagnetic induction (EMI) system Proposed System Conventional System Control system including sensors, controller, and power supply EMI system consisting of permanent magnet and coils

10. PROPOSED CONTROL SYSTEM • Advantages of Proposed Control System • Adaptability : damping characteristics of • MR damper vary with • strength of external load • Simplicity : no power source, no controller, • and no sensors

11. PROPOSED CONTROL SYSTEM • Advantages of Proposed Control System • Adaptability : damping characteristics of • MR damper vary with • strength of external load • Simplicity : no power source, no controller, • and no sensors SMART

12. PROPOSED CONTROL SYSTEM • Advantages of Proposed Control System • Adaptability : damping characteristics of • MR damper vary with • strength of external load • Simplicity : no power source, no controller, • and no sensors SMART PASSIVE

13. NUMERICAL VERFICATION • Three-story Building (Dyke et al. 1996) MR damper Dynamics and Smart Structures Lab., Sejong Univ., KOREA

14. NUMERICAL VERFICATION • Control Systems Compared • Proposed MR damper-based control system - SPC-D: EMI part designed to reduce drifts - SPC-A: EMI part designed to reduce accelerations • Conventional smart damping system - CO-D: clipped-optimal algorithm to reduce drifts - CO-A: clipped-optimal algorithm to reduce accelerations

15. NUMERICAL VERFICATION • Simulation Results • Normalized peak responses under four historic earthquakes CO-D CO-A SPC-D SPC-A El Centro Hachinohe Kobe Northridge Peak Accel. Peak Drift

16. EXPERIMENTAL VERIFICATION • Three-story Building Model Installed EMI System Dynamics and Smart Structures Lab., Sejong Univ., KOREA

17. EXPERIMENTAL VERIFICATION • Ground Input Motion (Scaled El Centro Earthquake) • 40% El Centro earthquake (PGA: 0.1395 g) • 20% El Centro earthquake (PGA: 0.0697 g) • 30% Hachinohe earthquake (PGA: 0.0811 g) • 20% Kobe earthquake (PGA: 0.1643 g) • 10% Northridge earthquake (PGA: 0.0843 g) - 진동대 입력 하중:

18. EXPERIMENTAL VERIFICATION • Experimental Results: Movie Clips

19. EXPERIMENTAL VERIFICATION • Experimental Results: Passive-mode Case Peak Acceleration at 3rd floor Peak Drift between 2nd and 3rd floors • Passive-off: 0 Volt • Passive-optimal: 3 Volt • Passive-on: 10 Volt

20. EXPERIMENTAL VERIFICATION Optimal

21. EXPERIMENTAL VERIFICATION • Experimental Results: Acceleration at 3rd Floor Passive-on (10Volt) Smart passive

22. EXPERIMENTAL VERIFICATION

23. EXPERIMENTAL VERIFICATION • Experimental Results: Comparison Peak Acceleration at 3rd floor Peak Drift between 2nd and 3rd floors

24. EXPERIMENTAL VERIFICATION

25. CONCLUSIONS Proposed MR Damper-based Control System • Compact, simple, and cost-effective. • Adaptable to external loads. • Shows the comparable performance to a conventional smart system using clipped optimal algorithm in numerical simulation. • Shows the comparable performance to optimal passive case in preliminary experiment. Dynamics and Smart Structures Lab., Sejong Univ., KOREA

26. Thank You for Your Attention! Dynamics and Smart Structures Lab., Sejong Univ., KOREA

27. NUMERICAL VERFICATION • Design of EMI System • Determination of coil turns for solenoid • By varying two parameters, Sa and Si Sa : summation of peak acceleration at each floor Si : summation of peak interstory drift at each floor which are normalized by uncontrolled responses • Using envelope of maximum value of Sa and Si for El Centro, Hachinohe, Kobe earthquakes • Two EMI systems are designed: EMI-A from Sa and EMI-D from Si

28. SMART PASSIVE CONTROL SYSTEM • Estimation of induced voltages by EMI system • Faraday’s law of induction •  : induced electromotive force from EMI system • n: number of turns of coil • B : magnetic flux • B: magnetic field • A: cross area • w : width of the area covered by magnetic field • x : damper deformation (1)

29. SMART PASSIVE CONTROL SYSTEM • EMI system (15) (16) (17) where :damper deformation : width of area covered by magnetic field

30. SMART PASSIVE CONTROL SYSTEM • If we assume as below - Magnetic field : 1.2 T (Tesla) - Turns of solenoid : 900 turns/m - Area of cross section : 13.2 (cm2) - Velocity of stroke : 9 cm/s (max. value of uncontrolled) Area : 13.2cm2 Length : 5cm

31. El Centro El Centro Kobe Kobe Hachinohe Hachinohe NUMERICAL VERFICATION Max. envelope of Sa Sa EMI-A : 2.6104 Coil turns/m Coil turns/m Variations of Sa Envelope of max. responses Max. envelope of Si Si EMI-D : 2.2104 Coil turns/m Coil turns/m

32. NUMERICAL VERFICATION • Results • Induced voltages for various earthquakes by EMI system EL Centro Hachinohe Voltage (V) Kobe Northridge Voltage (V) Time (sec) Time (sec)

33. NUMERICAL VERFICATION EL Centro Hachinohe • Normalized accelerations at each floor Normalized accel. Clipped-D Clipped-A EMI-D EMI-A Kobe Northridge Normalized accel. Floor level Floor level

34. NUMERICAL VERFICATION EL Centro Hachinohe • Normalized interstory drifts at each floor Normalized accel. Clipped-D Clipped-A EMI-D EMI-A Kobe Northridge Normalized accel. Floor level Floor level