Hyung-Jo Jung

Smart passive system based on magnetorheological damper

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.

MR damper-based smart passive control system for seismic protection of building structures

This paper investigates the feasibility and efficacy of an MR damper-based control system introducing an electromagnetic induction (EMI) part, for suppressing vibration of building structures subjected to seismic loadings. In the proposed control system, the EMI part composed of a permanent magnet and a coil converts the kinetic energy of the relative motion between a building and a damper into the electric energy, which is used for a change in damping characteristics of the MR damper. Since the EMI part can be used as a controller, which determines the command voltage input according to structural responses, as well as a power source, the proposed control system can be much more compact, convenient, and economic than a conventional active/semiactive system that needs a power supply, a controller and sensors. To verify the feasibility and efficacy of the proposed control system, a shaking table test of a small-scale building model employing the MR damper with the EMI part is conducted. The performance of the proposed control system is compared with that of conventional semiactive control systems using an MR damper.

A smart passive damping system for stay cables

This paper presents a smart passive damping system (SPDS) for reducing stay cable vibrations. Stay cables, such as used in cable-stayed bridges, are prone to vibration due to their low inherent damping characteristics. Recently some studies have shown that semiactive control systems using Magnetorheological(MR) dampers can potentially achieve higher performance levels and adaptability with few of the detractions as compared their passive counterparts. However, most semi-active and active control systems that use MR dampers require additional power supplies, controllers, and sensors, adding complexity into the system. The complexity may not be desirable to effectively control many large civil structures. This paper proposes a novel SPDS with MR dampers. The smart passive device includes an electromagnetic induction (EMI) system to power the MR damper and adjust itself to external loadings. Thus, SPDS dose not require any control system. The numerical study considered 12.56m stay cable to evaluate the dynamic performance of the SPDS for mitigating the vibration of stay cables. Moreover, the performances of the smart passive damping system are compared with those of an equivalent linear viscous damper and an MR damper operated in a pssive-mode. Results showed SPDS has competitive performance with others despite of its simplicity.