Kim J.T.,KAIST |
Kim D.S.,KAIST |
Park H.J.,KAIST |
Bang E.S.,Korea Institute of Geoscience and Mineral Resources |
Kim S.W.,Korea Railroad Corporation
Exploration Geophysics | Year: 2010
In current design practice, the shear wave velocity (Vs) of the core and rock-fill zone of a dam, one of the characteristics essential for seismic response design, is seldom determined by field tests. This is because the borehole seismic method is often restricted in application, due to stabilisation activities and concern for the security of the dam structure, and surface wave methods are limited by unfavourable in-situ site conditions. Consequently, seismic response design for a dam may be performed using Vs values that are assumed, or empirically determined. To estimate Vs for the core and rock-fill zone, and to find a reliable method for measuring Vs, seismic surface wave methods have been applied on the crest and sloping surface of the existing 'M' dam. Numerical analysis was also performed to verify the applicability of the surface wave method to a rock-fill dam. Through this numerical analysis and comparison with other test results, the applicability of the surface wave method to rock-fill dams was verified. © 2010 ASEG/SEGJ/KSEG.
Jung H.-S.,Korea Railroad Corporation |
Chung S.-R.,Hanyang University |
Chun B.-S.,Hanyang University |
Lee Y.-J.,Seoul National University of Science and Technology
Tunnelling and Underground Space Technology | Year: 2013
This study was dealt with clogging problems of the drain aperture in old tunnels. The precipitates in the drainage were mainly generated by degradation of the tunnel concrete lining. The degradation was made by the chemical reaction between the concrete material and groundwater. If the degree of precipitation is high in the tunnel drainage, the groundwater cannot flow easily in it. Consequently, the groundwater level will go up, and this can lead to the highest water pressure which affects to the structural risk of tunnel. The degraded drainage causes to generate not only the structural stability of tunnel, but also the additional maintenance problem. Up to this time the technical study of preventing the scale for just tunnel drain aperture was rare. However, there are some preventive technologies about the scale for the industrial facilities such as oil pipe lines etc. There are two most popular technologies. One is Quantum Stick using Brown's principle of quantum mechanics and the other one is Magnetizing device to inhibit the scale formation by changing the form of calcium carbonate particles. In this study, in order to improve the clogging problem in the tunnel drain aperture the elementary technologies were introduced. In addition, the laboratory tests were conducted to evaluate their applicability using the results from SEM and XRD analysis on the sediment generated during the test. As a result, Quantum Stick showed the reasonable effect of scale removing under the condition of more than velocity limit. © 2013 Elsevier Ltd.
Jung H.-S.,Korea Railroad Corporation |
Park J.-S.,Daewoo Shipbuilding and Marine Engineering |
Lee Y.-J.,Seoul National University of Science and Technology |
Kim S.-K.,Korea Institute of Construction Technology |
And 3 more authors.
KSCE Journal of Civil Engineering | Year: 2013
Atomized slag is a residual waste product of steel manufacturing. The use of atomized slag as a recycled material is widespread in Korea, especially for filter media, ceramic filters, coagulate, construction materials, abrasives, and desulfurizing agents. The absorptivity of atomized slag as a reactive media for a permeable reactive barrier to eliminate pollutants inflowing from landfills was investigated in this study. Physical tests were performed to analyze the engineering properties of the atomized slag. The absorptive performance of the atomized slag against heavy metals and organics was examined in batch and column tests. Pilot-scaled and field tests were performed and monitored to evaluate the absorptivity of the atomized slag in the permeable reactive barrier against heavy metals and organics. The pilot-scaled test results showed the removal efficiencies of more than 94.9% for organics and more than 99.9% for heavy metals passing into the atomized media. The field test results indicated that the removal efficiencies of the atomized slag applied in the permeable reactive barrier were measured to be from 82 to 85% for organics and from 90 to 95% for heavy metals. The implications of the results are discussed. © 2013 Korean Society of Civil Engineers and Springer-Verlag Berlin Heidelberg.
Jung H.,Korea University |
Jung H.,Korea Infrastructure Safety and Technology Corporation |
Park H.M.,Incheon Bridge Corporation IBC |
Kim J.H.,Moohan ST |
And 2 more authors.
KSCE Journal of Civil Engineering | Year: 2013
The main deterioration process jeopardizing the durability of Reinforced Concrete (RC) structures in marine environments is chloride-induced corrosion of the concrete reinforcement, which leads to high maintenance and repair costs, with the consequent concern for premature structural deterioration. The corrosion process of the concrete reinforcement has uncertainties associated with quality of concrete and exposure condition. A methodology is proposed for a probabilistic Life-Cycle Cost (LCC) model in service life through the condition assessment of RC structures against corrosion initiation based on Bayesian techniques using monitoring data. The LCC model is estimated during a structure's life by using the Monte Carlo Simulation (MCS) technique. For the application of the developed model, the LCC models of two dockyards in the Atlantic Ocean and Korea are estimated and compared during a structure's life. The LCC model is updated to consider the safety of the structure (the application time of maintenance intervention), cost efficiency and reduced uncertainty successively whenever new monitoring data of the chloride penetration is available during service time. © 2013 Korean Society of Civil Engineers and Springer-Verlag Berlin Heidelberg.
Byeon G.,Smart Distribution Research Center |
Kim J.-Y.,Smart Distribution Research Center |
Kim S.-K.,Smart Distribution Research Center |
Cho K.-H.,Smart Distribution Research Center |
Lee B.-G.,Korea Railroad Corporation
Transactions of the Korean Institute of Electrical Engineers | Year: 2016
This paper proposed a program of an energy storage system(ESS) for peak shaving of high-speed railway substations The peak shaving saves cost of equipment and demand cost of the substation. To reduce the peak load, it is very important to know when the peak load appears. The past data based load profile forecasting method is easy and applicable to customers which have relatively fixed load profiles. And an optimal scheduling method of the ESS is helpful in reducing the electricity tariff and shaving the peak load efficiently. Based on these techniques, MS. NET based peak shaving program is developed. In case study, a specific daily load profile of the local substation was applied and simulated to verify performance of the proposed program. ©The Korean Institute of Electrical Engineers.
Jun H.-K.,Korea Railroad Research Institute |
Seo J.-W.,Korea Railroad Research Institute |
Jeon I.-S.,Korea Railroad Corporation |
Lee S.-H.,Kyung Hee University |
Chang Y.-S.,Kyung Hee University
Engineering Failure Analysis | Year: 2015
Although repair by arc welding is a well-known method for damaged rail surface recovery due to its ease of application, the method is vulnerable to the creation of cracks. In this study, a series of failure analyses and crack growth analyses were carried out on a fractured weld-repaired rail to determine the cause of the rail failure and the effect of residual stress on the crack growth rate. For this purpose, the residual stress profiles of rails under various conditions were obtained by both sectioning the physical rail and simulating the weld-repair process of the rail using the finite element method. Subsequently, the fatigue crack growth in the weld-repaired rail was simulated by assuming that a semi-elliptical crack was initiated at the boundary between the weld pool and heat-affected zone. From these analyses, it was found that weld defects, such as porosity, lamella line cracks, and quick transitions in material hardness and microstructure, especially at the boundaries, could be the causes of the crack initiation. The crack growth rate was strongly influenced by the magnitude of the residual stress, while it was significantly increased in the presence of high tensile residual stress at the rail head due to the weld repair. Therefore, reducing the tensile stress magnitude and increasing the compressive stress magnitude in the rail head is crucial to solving this problem in railway rail weld repair. © 2015 Elsevier Inc.