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Author

Sang-Won Cho

Other affiliations: Samsung SDS, KAIST
Bio: Sang-Won Cho is an academic researcher from University of Western Ontario. The author has contributed to research in topics: Damper & Magnetorheological fluid. The author has an hindex of 14, co-authored 24 publications receiving 609 citations. Previous affiliations of Sang-Won Cho include Samsung SDS & KAIST.

Papers
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Journal ArticleDOI
TL;DR: In this article, a smart passive system is proposed, which is based on an MR damper system and an electromagnetic induction (EMI) system that uses a permanent magnet and a coil.
Abstract: Magnetorheological (MR) dampers are one of the most promising control devices for civil engineering applications to earthquake hazard mitigation, because they have many advantages such as small power requirement, reliability, and low price to manufacture. To reduce the responses of the controlled structure by using MR dampers, a control system including a power supply, controller, and sensors is needed. However, when a lot of MR dampers are applied to large-scale civil structures, such as cable-stayed bridges and high-rise buildings, the control system becomes complex. Thus, it is not easy to install and to maintain the MR damper-based control system. In this paper, to resolve the above difficulties, a smart passive system is proposed, which is based on an MR damper system. The smart passive system consists of an MR damper and an electromagnetic induction (EMI) system that uses a permanent magnet and a coil. According to the Faraday law of induction, the EMI system that is attached to the MR damper produces electric energy. The produced energy is applied to the MR damper to vary the damping characteristics of the damper. Thus, the smart passive system does not require any power at all. Furthermore, the output of electric energy is proportional to input loads such as earthquakes, which means the smart passive system has adaptability by itself without any controller or corresponding sensors. Therefore, it is easy to build up and maintain the proposed smart passive system. To verify the effectiveness of the proposed smart passive system, the performance is compared with that of the normal MR damper-based control system. The numerical results show that the smart passive system has comparable performance to the normal MR damper-based control system.

131 citations

Journal ArticleDOI
TL;DR: In this article, a semi-active fuzzy control strategy for seismic response reduction using a magnetorheological (MR) damper is presented, which is fail-safe in that the bounded-input, bounded-output stability of the controlled structure is guaranteed.
Abstract: A semi-active fuzzy control strategy for seismic response reduction using a magnetorheological (MR) damper is presented. When a control method based on fuzzy set theory for a structure with a MR damper is used for vibration reduction of a structure, it has an inherent robustness, and easiness to treat the uncertainties of input data from the ground motion and structural vibration sensors, and the ability to handle the non-linear behavior of the structure because there is no longer the need for an exact mathematical model of the structure. For a clipped-optimal control algorithm, the command voltage of a MR damper is set at either zero or the maximum level. However, a semi-active fuzzy control system has benefit to produce the required voltage to be input to the damper so that a desirable damper force can be produced and thus decrease the control force to reduce the structural response. Moreover, the proposed control strategy is fail-safe in that the bounded-input, bounded-output stability of the controlled structure is guaranteed. The results of the numerical simulations show that the proposed semi-active control system consisting of a fuzzy controller and a MR damper can be beneficial in reducing seismic responses of structures.

123 citations

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TL;DR: In this paper, the feasibility of a newly developed smart passive control system equipped with an electromagnetic induction device is experimentally investigated, which is composed of a permanent magnet and a solenoid.
Abstract: The feasibility of a newly developed smart passive control system equipped electromagnetic induction device is experimentally investigated. An electromagnetic induction device consists of a permanent magnet and a solenoid, which produces electrical energy (i.e. induced current) according to Faraday's law of electromagnetic induction. The produced energy is applied to the magnetorheological (i.e. MR) damper to change the damping characteristics by itself without any controller or corresponding sensors for reducing structural responses. Recently, the smart passive control system was conceptually and numerically introduced without consideration of its practical applicability. This paper describes the design of an electromagnetic inductive device which is composed of a permanent magnet and a solenoid, and experiments with the MR damper-based smart passive control system on a shaking table which produces various sinusoidal and random excitations. The experimental results demonstrate that it is feasible to apply the smart passive control system equipped electromagnetic induction device for changing the damping characteristics of an MR damper.

64 citations

Journal ArticleDOI
TL;DR: In this paper, a smart passive system based on an MR damper system without including a power supply, controller, and sensors consists of an MR Damper and an electromagnetic induction (i.e., EMI) system that uses a permanent magnet and a coil.
Abstract: Magnetorheological (i.e., MR) dampers are one of the most prospective semiactive control devices for civil engineering applications to earthquake hazard mitigation, because they have many advantages such as small power requirement, reliability, and low price to manufacture. A smart passive system based on an MR damper system without including a power supply, controller, and sensors consists of an MR damper and an electromagnetic induction (i.e., EMI) system that uses a permanent magnet and a coil. The electromotive force induced by movement of a structure can control MR damper effectively without any external power supply and control algorithm. This smart passive control system is implemented to verify the effectiveness for seismic protection of benchmark structural control problem for the seismically excited highway bridge, which is based on the newly constructed 91/5 highway over-crossing in Southern California. The results of the numerical simulations show that the presented control system can be beneficial in reducing seismic responses of benchmark bridge structure.

39 citations

Journal ArticleDOI
TL;DR: In this article, a simplified method for the computation of first-, second-and higher-order derivatives of eigenvalues and eigenvectors associated with repeated eigen values is presented.

35 citations


Cited by
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Journal ArticleDOI

[...]

08 Dec 2001-BMJ
TL;DR: There is, I think, something ethereal about i —the square root of minus one, which seems an odd beast at that time—an intruder hovering on the edge of reality.
Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

33,785 citations

Journal ArticleDOI
TL;DR: A review of the past, recent developments and implementations of the Bouc-Wen model which is used extensively in modeling the hysteresis phenomenon in the dynamically excited nonlinear structures can be found in this paper.
Abstract: Structural systems often show nonlinear behavior under severe excitations generated by natural hazards. In that condition, the restoring force becomes highly nonlinear showing significant hysteresis. The hereditary nature of this nonlinear restoring force indicates that the force cannot be described as a function of the instantaneous displacement and velocity. Accordingly, many hysteretic restoring force models were developed to include the time dependent nature using a set of differential equations. This survey contains a review of the past, recent developments and implementations of the Bouc-Wen model which is used extensively in modeling the hysteresis phenomenon in the dynamically excited nonlinear structures.

602 citations

Journal ArticleDOI
TL;DR: The magnetorheological fluid dampers could offer an outstanding capability in semiactive vibration control due to excellent dynamical features such as fast response, environmentally robust characteristics, large force capacity, low power consumption, and simple interfaces between electronic input and mechanical output as mentioned in this paper.
Abstract: Magnetorheological fluid technology has gained significant development during the past decades. The application of magnetorheological fluids has grown rapidly in civil engineering, safety engineering, transportation, and life science with the development of magnetorheological fluid–based devices, especially magnetorheological fluid dampers. The magnetorheological fluid dampers could offer an outstanding capability in semiactive vibration control due to excellent dynamical features such as fast response, environmentally robust characteristics, large force capacity, low power consumption, and simple interfaces between electronic input and mechanical output. To address the fast growing demand on magnetorheological fluid damping technology in extensive engineering practices, the state-of-the-art development is presented in this article, which provides a comprehensive review on the structure design and its analysis of magnetorheological fluid dampers (or systems). This can be regarded as a useful complement to...

298 citations

Journal ArticleDOI
TL;DR: The state-of-the-art review indicates to what extent ML has been applied in four topic areas of earthquake engineering, including seismic hazard analysis, system identification and damage detection, seismic fragility assessment, and structural control for earthquake mitigation.
Abstract: Machine learning (ML) has evolved rapidly over recent years with the promise to substantially alter and enhance the role of data science in a variety of disciplines. Compared with traditional appro...

185 citations

Journal ArticleDOI
TL;DR: Recently developed methods and theories in the developing direction for applications of artificial intelligence in civil engineering, including evolutionary computation, neural networks, fuzzy systems, expert system, reasoning, classification, and learning, are summarized.
Abstract: Artificial intelligence is a branch of computer science, involved in the research, design, and application of intelligent computer. Traditional methods for modeling and optimizing complex structure systems require huge amounts of computing resources, and artificial-intelligence-based solutions can often provide valuable alternatives for efficiently solving problems in the civil engineering. This paper summarizes recently developed methods and theories in the developing direction for applications of artificial intelligence in civil engineering, including evolutionary computation, neural networks, fuzzy systems, expert system, reasoning, classification, and learning, as well as others like chaos theory, cuckoo search, firefly algorithm, knowledge-based engineering, and simulated annealing. The main research trends are also pointed out in the end. The paper provides an overview of the advances of artificial intelligence applied in civil engineering.

164 citations