4 th World Conference on Structural Control and Monitoring

1. 4th World Conference on Structural Control and Monitoring Smart Passive System based on MR Damperfor Benchmark Structural Control Problemfor a Seismically Excited Highway Bridge Kang-Min Choi, KAIST, Korea Hyung-Jo Jung, Sejong University, Korea Sang-Won Cho, The University of Western Ontario, Canada In-Won Lee, KAIST, Korea

2. Contents CONTENTS • Introduction • Benchmark Highway Bridge Structure • Smart Passive Control System • Numerical Simulation Results • Conclusions

3. Introduction Introduction • Semiactive MR Dampers • Viscous fluid out of magnetic field • Solid-like in a magnetic field • Proportional strength to magnitude of magnetism • Magnetorheological (MR) fluid Without Magnetic Fields With Magnetic Fields

4. Introduction • MR fluid damper • Damping coefficient depending on electric current • Requirements : External power for current supply Sensors for feedback control Limitation for large-scale structures

5. Introduction Cho, S.W., Jung, H.J., Lee, I.W. (2005) “Smart passive system based on magnetorheological damper.”Smart Materials and Structures, 14, 707-714. • Change characteristics of MR damper with electromagnetic induction (EMI) system • Control without external power and control algorithm • Verified by small-scaled shaking table experiment(Jung et al. 2005) • Smart Passive Control System

6. Introduction Investigate the effectiveness of the Smart Passive Control System for Benchmark Structural Control Problem for a Seismically Excited Highway Bridge • Objective of this study:

7. Benchmark Highway Bridge Structure Benchmark Highway Bridge Structure • Structural Model • 91/5 highway bridge in southern California, USA • - Details of the bridge are presented in the definition paper • (Agrawal et al. 2005) • Isolated using four non-linear LRB on each abutment • and one bearing on each bent column at the center

8. Benchmark Highway Bridge Structure Smart Passive System MR damper LRB EMI system

9. MR Damper induced current magnetic field damper deformation EMI system Smart Passive Control System Smart Passive Control System • Schematic of the Smart Passive System Faster MR damper movement Higher EMF EMI system is a source of power supply and has adaptability.

10. Smart Passive Control System • EMI System for MR Damper • Faraday’s law of electromagnetic induction (1) : Electromotive force (EMF) N : Number of turns of coil : Magnetic flux B : Magnetic field A : Area of cross section

11. Solenoid Magnetic Field Change of Area Movement of Solenoid Smart Passive Control System (2)

12. Numerical Simulation Results Numerical Simulation Results • MR damper • Maximum force level: 1000 kN • Maximum voltage : 10 Volts • - Parameters of the MR damper are described in the sample • control design of the benchmark definition paper • (Agrawal et al. 2005)

13. Numerical Simulation Results • Input earthquakes : North Palm Springs (1986) : TCU084 component of Chi-Chi earthquake, Taiwan (1999) : El Centro component of Imperial Valley earthquake (1940) : Rinaldi component of Northridge earthquake (1994) : Bolu component of Duzce, Turkey (1999) : Nishi-Akashi component of Kobe (1995)

14. Numerical Simulation Results • Evaluation criteria • Peak response quantities • Normed response quantities J1: Pk. base shear J2: Pk. over. mom. J3: Pk. mid. disp. J4: Pk. mid. acc. J5: Pk. bear. Def. J6: Pk. ductility J9: Norm. base shear J10: Norm. over. mom. J11: Norm. mid. disp. J12: Norm. mid. acc. J13: Norm. bear. Def. J14: Norm. ductility

15. Numerical Simulation Results • Controller itself J15: Pk. control force J16: Pk. Stroke J17: Pk. instantaneous power J18: Pk. total power J19: Number of control devices J20: Number of sensors J21: Dim. of the discrete state vector

16. Numerical Simulation Results • Optimal passive control • Average of sum of evaluation criteria Optimal passive-on (5 V) Voltage (V)

17. Design of EMI system (50V·sec/m) Numerical Simulation Results • Design of EMI system • Average of sum of evaluation criteria

18. Numerical Simulation Results - Magnitude of magnetic field - Width of magnets - Number of turns of coil

19. Numerical Simulation Results • Numerical results • Average of each evaluation criteria for all earthquakes - The effectiveness of the smart passive is clearly demonstrated.

20. Numerical Simulation Results • Voltage induced at one EMI system under El Centro earthquake Voltage (V) Time (sec) - The enough voltage can be generated by EMI system designed according to structural response.

21. Numerical Simulation Results • - The smart passive system has significant advantage that it requires • no power supply during controlling structures with similar function • to other control systems • - Thus, the smart passive system was able to reduce efficiently by itselfwithout any power supply and control algorithm according to structural responses.

22. Conclusions Conclusions • Smart passive control system is based on electromagnetic induction (EMI) using MR damper. • The EMI system takes a role of power supply and has adaptability.

23. Conclusions • Performance verification of benchmark problem • Smart passive systemis significantly better than passive -off and -on cases. • Smart passive systemis comparable with passive optimal and semiactive Lyapunov control case. : It is highly energy efficient. • Smart passive system is thesuperior control device.

24. Thank You for Your Attention