Structural Dynamics & Vibration Control Lab 1 December Department of Civil & Environmental Engineering K orea A dvanced I nstitute of S cience and T echnology. Experimental Study on Smart Passive System Based on MR Damper The 18 th KKCNN Symposium Jung-Hyun Hong, Graduate Student, KAIST, Korea Kang-Min Choi, Ph.D. Candidate, KAIST, Korea Jong-Heon Lee, Professor, Kyungil University, Korea Ju-Won Oh, Professor, Hannam University, Korea In-Won Lee, Professor, KAIST, Korea

Structural Dynamics & Vibration Control Lab 2 CONTENTS I.Introduction II. Smart Passive Control System III. Experimental Verification IV. Conclusions Contents

Structural Dynamics & Vibration Control Lab 3 - Viscous fluid out of magnetic field - Solid-like in a magnetic field - Proportional strength to magnitude of magnetism Magnetorheological (MR) fluid Introduction Semiactive MR Dampers Introduction Without Magnetic Fields With Magnetic Fields

Structural Dynamics & Vibration Control Lab 4 -Damping coefficient depending on electric current -Requirements : External power for current supply Sensors for feedback control MR fluid damper Introduction Limitation for large-scale structures

Structural Dynamics & Vibration Control Lab 5 Introduction Cho, S.W., Jung, H.J., Lee, I.W. (2005) “Smart passive system based on magnetorheological damper.” Smart Materials and Structures, 14, Change characteristics of MR damper with electromagnetic induction (EMI) system - Control without external power and control algorithm Need for experimental verification Smart Passive Control System

Structural Dynamics & Vibration Control Lab 6 Faraday’s law of electromagnetic induction Smart Passive Control System EMI System for MR Damper Smart Passive Control System : Electromotive force (EMF) N : Number of turns of coil : Magnetic flux B : Magnetic field A : Area of cross section (1)

Structural Dynamics & Vibration Control Lab 7 Smart Passive Control System Faster MR damper movement Higher EMF  EMI system is a source of power supply and has adaptability. MR Damper damper deformation magnetic field induced current EMI system Schematic of the Smart Passive System

Structural Dynamics & Vibration Control Lab 8 Performance Verification Experimental Setup Performance Verification V DAQ Board Computer MR damper EMI system

Structural Dynamics & Vibration Control Lab 9 Performance Verification Shear building model - Height: 105 cm - Total weight: kg - First three natural frequencies : 2.05, 5.55, 8.41 Hz - Damping ratio: 0.7%

Structural Dynamics & Vibration Control Lab 10 Performance Verification MR damper - MR controllable friction damper (RD , Lord Corporation) - Maximum force level: 100 N - Maximum command current: 0.5 A

Structural Dynamics & Vibration Control Lab 11 Performance Verification EMI system Magnets Solenoid

Structural Dynamics & Vibration Control Lab 12 Performance Verification - Electromotive force (EMF) Magnetic Field Solenoid Movement of Solenoid Change of Area (2) (3) - Magnetic field: - Width of magnets: - Number of turns: 

Structural Dynamics & Vibration Control Lab 13 Performance Verification Input Ground Motion -Time scale: 2 times the recorded rate -Amplitude scale: 40% El Centro earthquake (PGA: g) 20% El Centro earthquake (PGA: g) 30% Hachinohe earthquake (PGA: g) 20% Kobe earthquake (PGA: g) 10% Northridge earthquake (PGA: g)

Structural Dynamics & Vibration Control Lab 14 Experimental Results Performance Verification Evaluation Criteria -J d1 : normalized maximum interstory drift between the base and 1 st floors -J d2 : normalized maximum interstory drift between the 1 st and 2 nd floors -J a1 : normalized maximum 1 st floor acceleration -J a3 : normalized maximum 3 rd floor acceleration

Structural Dynamics & Vibration Control Lab 15 Performance Verification Optimal Passive Control System -Scaled El Centro earthquake (0.14 g) Passive voltage value (V) Normalized value Passive voltage value (V) Optimal Optimal passive voltage : 0.85 V Sum of normalized values J d1 J d2 J a1 J a3

Structural Dynamics & Vibration Control Lab 16 -Scaled El Centro earthquake (0.14 g) Performance Verification Time (sec) d 2 (mm) a 3 (m/s 2 ) Voltage (V) Results

Structural Dynamics & Vibration Control Lab 17 -Performance comparisons Performance Verification Normalized maximum interstory drifts El Centro (0.14 g) El Centro (0.07 g) Hachinohe (0.08 g) Kobe (0.16 g) Northridge (0.08 g) Passive off Passive on Optimal passive Smart passive

Structural Dynamics & Vibration Control Lab 18 Performance Verification Normalized value Optimal Smart passive passive Passive off Passive on - Better than the passive off case - Similar to the optimal passive case

Structural Dynamics & Vibration Control Lab 19 Performance Verification Normalized maximum accelerations El Centro (0.14 g) El Centro (0.07 g) Hachinohe (0.08 g) Kobe (0.16 g) Northridge (0.08 g) Passive off Passive on Optimal passive Smart passive

Structural Dynamics & Vibration Control Lab 20 Performance Verification Normalized value Optimal Smart passive passive Passive off Passive on - Better than the passive on case - narrow range of responses

Structural Dynamics & Vibration Control Lab 21 -Dissipated electric energy Performance Verification Passive offPassive on Optimal passive Smart passive Energy (mJ/sec)  Smart passive system has the best energy efficiency.

Structural Dynamics & Vibration Control Lab 22 - 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. Conclusions Conclusions

Structural Dynamics & Vibration Control Lab 23 Conclusions Performance verification - Smart passive system is significantly better than passive off and passive on cases. - Smart passive system is comparable with optimal passive case. : It is highly energy efficient.  Smart passive system is the superior control device.

Structural Dynamics & Vibration Control Lab 24 Thank You for Your Attention