SOC Research Institute

Goyang, South Korea

SOC Research Institute

Goyang, South Korea
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Min D.-J.,Sungkyunkwan University | Kwon S.-D.,Chonbuk National University | Kwark J.-W.,SOC Research Institute | Kim M.-Y.,Sungkyunkwan University
Shock and Vibration | Year: 2017

The purpose of this paper is to present a framework to analyze the interaction between an actively controlled magnetic levitation vehicle and a guideway structure under gusty wind. The equation of motion is presented for a 30-dof maglev vehicle model consisting of one cabin and four bogies. In addition, a lateral electromagnetic suspension (EMS) system is introduced to improve the running safety and ride quality of the maglev vehicle subjected to turbulent crosswind. By using the developed simulation tools, the effects of various parameters on the dynamic response of the vehicle and guideway are investigated in the case of the UTM maglev vehicle running on a simply supported guideway and cable-stayed guideway. The simulation results show that the independent lateral EMS and associated control scheme are definitely helpful in improving the running safety and ride quality of the vehicle under gusty wind. In the case of the cable-stayed guideway, at low wind speed, vehicle speed is the dominant factor influencing the dynamic responses of the maglev vehicle and the guideway, but at wind speed over 10 m/s, wind becomes the dominant factor. For the ride quality of the maglev vehicle, wind is also the most influential factor. © 2017 Dong-Ju Min et al.


Kim Y.J.,University of Colorado at Denver | Kang J.-Y.,SOC Research Institute | Park J.-S.,SOC Research Institute | Jung W.-T.,SOC Research Institute
Journal of Physics: Conference Series | Year: 2017

This paper presents the condition evaluation of bridge girders upgraded using post-tensioned near-surface-mounted (NSM) carbon fiber reinforced polymer (CFRP) strips subjected to corrosion damage. Computational models are developed to predict the behavior of the girders over a 100-year service period. Dynamic analysis exhibits that damage localization takes place, in conjunction with various mode shapes. As the extent of damage rises, the effectiveness of the NSM CFRP increases and the flexural stiffness of the girders decreases. © Published under licence by IOP Publishing Ltd.


Kim Y.J.,University of Colorado at Denver | Kang J.-Y.,SOC Research Institute | Park J.-S.,SOC Research Institute | Jung W.-T.,SOC Research Institute
Journal of Bridge Engineering | Year: 2016

This paper presents the effect of corrosion damage on the service response of prestressed concrete bridge girders strengthened with posttensioned near-surface-mounted (NSM) carbon fiber-reinforced polymer (CFRP) strips. Three-dimensional finite-element modeling, validated against experimental data, is conducted to deterministically study the static and dynamic behavior of the girders subjected to chloride-induced corrosion for a period of 100 years. With an increase in corrosion damage, the efficacy of the posttensioned NSM CFRP augments from a serviceability perspective. Modal analysis identifies critical regions along the girder where strain localization occurs at certain dynamic excitation frequencies. The unstrengthened girders are more reactive to dynamic responses than their strengthened counterparts; however, both exhibit similar ride quality. Corrosion damage significantly decreases the equivalent flexural rigidity of the decrepit girders up to 30% relative to that of the control girders. The level of damage and the extent of the total potential for the strengthened girders are correlated with the magnitude of their fundamental frequencies. © 2015 American Society of Civil Engineers.


Cho J.-R.,SOC Research Institute | Jung K.,SOC Research Institute | Cho K.,SOC Research Institute | Kwark J.-W.,SOC Research Institute | And 2 more authors.
Proceedings of the Institution of Mechanical Engineers, Part F: Journal of Rail and Rapid Transit | Year: 2016

This paper revisits the creation and cancellation of the dynamic resonance phenomenon that occurs in bridge structures on high-speed lines when crossed by wheel loads. The resonance and its cancellation are mathematically formulated for a Bernoulli-type beam with general boundary conditions and subjected to loads moving at a regular spacing. The resonance of the bridge caused by the travelling loads occurs, regardless of the mode shape, when the natural frequency of the structure coincides with the loading frequency produced by the loads moving at a constant speed. In this study, the dependency of the cancellation phenomenon on the mode shape is determined based on the boundary conditions of the structure. In addition, the optimal span length that suppresses the response at resonance is proposed using the cancellation phenomenon for a simple beam with pinned-pinned, clamped-clamped and clamped-pinned boundary conditions; and a simply supported continuous beam. © IMechE 2014.


Cho J.-R.,SOC Research Institute | Jung K.,SOC Research Institute | Cho K.,SOC Research Institute | Kwark J.-W.,SOC Research Institute | And 2 more authors.
Proceedings of the Institution of Mechanical Engineers, Part F: Journal of Rail and Rapid Transit | Year: 2016

This paper proposes a method that can be used during the preliminary design stage to determine the optimal span length of a railway bridge that minimizes its dynamic responses to the passage of high-speed trains. Since the designed speed for passage over a railway bridge is generally higher than the speed at which the resonance phenomenon occurs, the peak dynamic responses of the bridge are likely to occur when a train travels across a bridge. Therefore, this study suggests inertia and elastic spectra that represent the inertial force and elastic force per unit length of the bridge at the resonance condition, respectively. These spectra are defined as functions of the span length of the bridge, for which the type of train and damping ratio are fixed, and based on the relationship between the dynamic responses of two different railway bridges that was used as theoretical basis for the design diagram proposed by the European Rail Research Institute. The optimal span length of the bridge that produces the smallest responses is determined using the suggested spectra by quantitatively comparing the responses at resonance under various train loads as a function of the span length of the bridge. The proposed method is validated using numerical examples that consider the computation of the optimal span length of a simply supported single-span bridge crossed by individual KTX, HEMU and ICE 2 trains and combinations of these trains. © IMechE 2014.


Kim J.-H.,GEO C and I Co. | Gang S.-M.,U and G I and T Co. | Kim J.-M.,SOC Research Institute | Jang S.-H.,GEO C and I Co.
ACRS 2015 - 36th Asian Conference on Remote Sensing: Fostering Resilient Growth in Asia, Proceedings | Year: 2015

The recent construction of geographic information system (GIS) is developed in the 3D direction. 3D analysis and development of GIS are supported by XDworld, JoyMap and other domestic commercial engines, as well as by diverse overseas commercial engines. Also, open-source 3D display engines, including World Wind provided by NASA, are increasingly used for the development of GIS. Open-source-based GIS engines are cheap, and offer high freedom of development, giving them an advantage, while they are difficult to manage after development and require the developer itself to shoot troubles, giving them a disadvantage. Also, commercial GIS development engines are convenient to manage after development, and possible problems can be resolved in association with the developers of the engines, while they are expensive and the development scope is limited by the developers of engines. The most important thing for the development of system is the freedom of development and follow-up management of the system, and as such, conventional engines cannot possibly cover all these requirements. To overcome these limitations, game engine-based GIS development is recently in the spot, because game engines are cheap and offer high freedom of development. Thus, this study examines existing game engine-linked GIS development cases and presents the method of implementing the game engine-based GIS. 3D GI-linked game engines can be used to simulate a wealth of information, and to employ multi-layered mash-up technology, etc.


Kim Y.J.,University of Colorado at Denver | Kang J.-Y.,SOC Research Institute | Park J.-S.,SOC Research Institute | Jung W.-T.,SOC Research Institute
ACI Structural Journal | Year: 2016

This paper presents the performance reliability and functional complexity of prestressed concrete girders strengthened with an emerging rehabilitation method using post-tensioned near-surfacemounted (NSM) carbon fiber-reinforced polymer (CFRP) strips. The influence of corrosion damage on the flexural capacity of the girders is theoretically predicted based on a stochastic approach, including an emphasis on chloride diffusion and concentration. A total of 1,650,000 cases having various CFRP-post-tensioning levels from 0 to 60% of the strength of CFRP are simulated, and corresponding results are analyzed. Predictive results indicate that the effect of corrosion becomes distressful with a time gap of 13.7 years after the initiation of corrosion from a practical point of view. The efficacy of the post-tensioned NSM CFRP in terms of preserving flexural strength and reducing vulnerability to deterioration is more pronounced with an increase in service year, based on a robust stress redistribution mechanism. Functional complexity is also reduced after strengthening, which can better achieve the given functional requirements of constructed bridge girders. Performance-based design factors are proposed, depending on service categories that are a function of traffic volume. © 2016, American Concrete Institute. All rights reserved.


Lee C.,SOC Research Institute | Park S.,Korea University | Lee D.,Korea University | Lee I.-M.,Korea University | Choi H.,Korea University
Applied Clay Science | Year: 2014

Due to its high swelling potential and low hydraulic conductivity, the bentonite-based grout has been popularly used to backfill a borehole constructed for a closed-loop vertical ground heat exchanger in a geothermal heat pump system. In this study, three types of bentonites were compared in terms of viscosity and thermal conductivity. With the consideration of the groundwater inflow, the viscosity and thermal conductivity of the bentonite grouts having bentonite contents of 5%, 10%, 15%, 20% and 25% by weight were also examined. To evaluate the effect of salinity in the coastal area on the swelling potential of the bentonite, volume reduction tests were performed. And in order to reproduce the particle segregation of bentonite-sand mixture when the bentonite-based grout has relatively low viscosity, the segregation was observed using a ring-type separable test apparatus. © 2014 Elsevier B.V.


Min D.-J.,Sungkyunkwan University | Jung M.-R.,Sungkyunkwan University | Kim M.-Y.,Sungkyunkwan University | Kwark J.-W.,SOC Research Institute
International Journal of Structural Stability and Dynamics | Year: 2016

The purpose of this paper is to develop a detailed 3D maglev vehicle and guideway model and investigate the dynamic response characteristics of the coupled system. For this, the maglev vehicle is modeled as one cabin and four bogies having eight electromagnetics, four sensors, and four secondary suspensions based on the Urban Transit Maglev (UTM) system in Korea. The 3D dynamic equilibrium equations of the cabin and bogies are derived by considering the actively controlled electromagnetic forces. Also, the equations of motion for the guideway are derived using the modal superposition method for vertical, lateral, and torsional modes. The resulting coupled equations of motion are then solved using a predictor–corrector iterative algorithm. Finally, through the numerical simulation of the developed system, the responses using the 3D maglev vehicle model are compared with those obtained by the corresponding 2D model. The effects of surface irregularity on the dynamic interaction behaviors are then evaluated for increasing vehicle speeds. Particularly, the 3D resonance conditions of the guideway girder and the maglev vehicle are presented considering the resonance conditions due to equidistant moving loads. In addition, some resonance phenomena are rigorously explored, including the lateral resonance by a series of vehicles running on a girder. © 2016 World Scientific Publishing Company


Min J.,SOC Research Institute | Yi J.-H.,Korea Advanced Institute of Science and Technology | Yi J.-H.,Korea Maritime and Ocean University | Yun C.-B.,Ulsan National Institute of Science and Technology
Smart Structures and Systems | Year: 2015

Jacket-type offshore structures are always exposed to severe environmental conditions such as salt, high speed of current, wave, and wind compared with other onshore structures. In spite of the importance of maintaining the structural integrity for an offshore structure, there are few cases to apply a structural health monitoring (SHM) system in practice. The impedance-based SHM is a kind of local SHM techniques and to date, numerous techniques and algorithms have been proposed for local SHM of real-scale structures. However, it still requires a significant challenge for practical applications to compensate unknown environmental effects and to extract only damage features from impedance signals. In this study, the impedance-based SHM was carried out on a 1/20-scaled model of an Uldolmok current power plant structure in Korea under changes in temperature and transverse loadings. Principal component analysis (PCA)-based approach was applied with a conventional damage index to eliminate environmental changes by removing principal components sensitive to them. Experimental results showed that the proposed approach is an effective tool for long-term SHM under significant environmental changes. Copyright © 2015 Techno-Press, Ltd.

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