• Smart Structures and Systems
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• v.26 no.1
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• pp.89-102
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• 2020

Shape memory alloy (SMA)-based Superelasticity-assisted Slider (SSS) is proposed as an engineering solution to practically exploit the well-accepted advantages of both sliding isolation and SMA-based recentering. Self-centering capability in SSS is provided by austenitic SMA cables (or wire ropes), recently attracting a lot of interest and attention in earthquake engineering and seismic isolation. The cables are arranged in various novel and conventional configurations to make SSS versatile for aseismic design and retrofit of structures. All the configurations are detailed with thorough technical drawings. It is shown that SSS is applicable without the need for Isolation Units (IUs). IUs, at the same time, are devised for industrialized applications. The proof-of-concept study is carried out through the examination of mechanical behavior in all the alternative configurations. Force-displacement relations are determined. Isolation capabilities are predicted based on the decreases in seismic demands, estimated by the increases in effective periods and equivalent damping ratios. Restoring forces normalized relative to resisting forces are assessed as the criteria for self-centering capabilities. Lengths of SMA cables required in each configuration are calculated to assess the cost and practicality. Practical implementation is realized by setting up a small-scale IU. The effectiveness of SSS under seismic actions is evaluated using an innovative computer model and compared to those of well-known Isolation Systems (ISs) protecting a reference building. Comparisons show that SSS seems to be an effective IS and suitable for earthquake protection of both structural and non-structural elements. Further research aimed at additional validation of the system are outlined.

• Smart Structures and Systems
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• v.8 no.2
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• pp.173-190
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• 2011

As a practical and effective seismic resisting technology, the base isolation system has seen extensive applications in buildings and bridges. However, a few problems associated with conventional lead-rubber bearings have been identified after historical strong earthquakes, e.g., excessive permanent deformations of bearings and potential unseating of bridge decks. Recently the applications of shape memory alloys (SMA) have received growing interest in the area of seismic response mitigation. As a result, a variety of SMA-based base isolators have been developed. These novel isolators often lead to minimal permanent deformations due to the self-centering feature of SMA materials. However, a rational design approach is still missing because of the fact that conventional design method cannot be directly applied to these novel devices. In light of this limitation, a displacement-based design approach for highway bridges with SMA isolators is proposed in this paper. Nonlinear response spectra, derived from typical hysteretic models for SMA, are employed in the design procedure. SMA isolators and bridge piers are designed according to the prescribed performance objectives. A prototype reinforced concrete (RC) highway bridge is designed using the proposed design approach. Nonlinear dynamic analyses for different seismic intensity levels are carried out using a computer program called "OpenSees". The efficacy of the displacement-based design approach is validated by numerical simulations. Results indicate that a properly designed RC highway bridge with novel SMA isolators may achieve minor damage and minimal residual deformations under frequent and rare earthquakes. Nonlinear static analysis is also carried out to investigate the failure mechanism and the self-centering ability of the designed highway bridge.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.9
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• pp.1549-1559
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• 2010

Modern power system is operated and managed in closed network environment with treating a great variety of data, and requirement of real time power system data is more increasing. However, it is difficult for operators to fast evaluate the condition of power system using only isolation network system such as SCADA or EMS regarding unexpecting situations occurring. Recent technology achievement in areas of distributed computing, networking high speed communications and digital control as well as the availability of accurate GPS time source are rapidly becoming the enabling factors for the development of a new generation of real time power grid monitoring tools. In this paper, architecture of WAMAC which is the wide area monitoring and control system not only to control but also to monitoring in real time is proposed and the plan of integration interface with legacy system such as EMS for providing power system analysis base data effectively is suggested.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2005.03a
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• pp.469-476
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• 2005

To date, many viable smart base isolation systems have been proposed. In this study, a novel friction pendulum system (FPS) and an MR damper are employed as the isolator and supplemental damping device, respectively. A fuzzy logic controller (FLC) is used to modulate the MR damper. A genetic algorithm (GA) is used for optimization of the FLC. The main purpose of employing a GA is to determine appropriate fuzzy control rules as well to adjust parameters of the membership functions. To this end, a GA with a local improvement mechanism is applied. Neuro-fuzzy models are used to represent dynamic behavior of the MR damper and FPS. Effectiveness of the proposed method for optimal design of the FLC is judged based on computed responses to several historical earthquakes. It has been shown that the proposed method can find appropriate fuzzy rules and the GA-optimized FLC outperforms not only a passive control strategy but also a human-designed FLC and a conventional semi-active control algorithm.