• Journal of the Korean Geotechnical Society
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• v.30 no.6
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• pp.5-21
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• 2014

It has been pointed out that the collapses of unsaturated road embankments caused by earthquake are attributed to high water content caused by the seepage of the underground water and/or the rainfall infiltration. Hence, it is important to study influences of water content on the dynamic stability and deformation mode of unsaturated road embankments for development of a proper design scheme including an effective reinforcement to prevent severe damage. This study demonstrates dynamic centrifugal model tests with different water contents to investigate the effect of water content on deformation and failure behaviors of unsaturated road embankments. Based on the measurement of displacement, the pore water pressure and the acceleration during dynamic loading, dynamic behavior of the unsaturated road embankments with about optimum water content and the higher water content than the optimum one have been examined. In addition, an image analysis has revealed the displacement field and the distributions of strains in the road embankment, by which deformation mode of the road embankment with higher water content has been clarified. It has been confirmed that in the case of higher water content the settlement of the crown is large mainly owing to the volume compression underneath the crown, while the small confining pressure at the toe and near the slope surface induces large shear deformation with volume expansion.

• Journal of the Korea Concrete Institute
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• v.15 no.4
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• pp.594-605
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• 2003

Pinching is an important property of reinforced concrete member which characterizes its cyclic behavior. In the present study, numerical studies were performed to investigate the characteristics of pinching behavior and the energy dissipation capacity of flexure-dominated reinforced concrete members. By investigating existing experiments and numerical results, it was found that flexural pinching which has no relation with shear action appears in RC members subject to axial compression force. However, members with specific arrangement and amount of re-bars, have the same energy dissipation capacity regardless of the magnitude of the axial force applied even though the shape of the cyclic curve varies due to the effect of the axial force. This indicates that concrete as a brittle material does not significantly contribute to the energy dissipation capacity though its effect on the behavior increases as the axial force increases, and that energy dissipation occurs primarily by re-bars. Therefore, the energy dissipation capacity of flexure-dominated member can be calculated by the analysis on the cross-section subject to pure bending, regardless of the actual compressive force applied. Based on the findings, a practical method and the related design equations for estimating energy dissipation capacity and damping modification factor was developed, and their validity was verified by the comparisons with existing experiments. The proposed method can be conveniently used in design practice because it accurately estimates energy dissipation capacity with general design parameters.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.5 no.1
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• pp.13-20
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• 1985

Two Cable-Stayed bridge on south coast in Korea has not constructed until a quarter of a century past since the beginning of it's own era. Our country is about to be interested in such a type of bridge. It has succeeded in constructing the 500 m spanned bridge against wind and earthquake in other several countries. Many contries are striving for designning a long spanned bridge to 1000m. For the realization of such a long spanned bridge in Korea clues to the problems, "How to design it", should be solved one by one. One of difficulties is in analysing the mechanical system because of multi-orter indeterminacy. In this study one of the numerical methods is proposed in order to eliminate the troublesome.

• Journal of the Korea Concrete Institute
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• v.22 no.5
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• pp.719-725
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• 2010

The analysis and experimental program of reinforced concrete (RC) structures for resistance against such extreme loads as earthquake, blast, and impact have been carried by many researchers and designers. Under the extreme loads, a large amount of energy is suddenly exerted to the structure, hence if the structure fails to absorb the impact energy, catastrophic collapse may occur. To prevent catastrophic collapse of structures, reinforced concrete must have adeguate toughness or it needs to be strengthened. The FRP strengthening method and SFRC are studied widely in resistance of impact load because of their high energy absorption capacity. In this study, drop weight impact tests were implemented to evaluate the impact resistance of SFRC and FRP strengthened RC beam while the total steel fiber volume fractions was fixed at 0.75% carbon FRP flexural strengthened RC beams. Futhermore, to prevent the shear-plug cracks when the impact load strikes the beams, additional FRP shear strengthening method are applied. The experimental, results showed that the FRP strengthened RC SFRC beams has high resistance of shear-plug cracks and crack width and SFRC has high resistance of concrete spalling failure compared to normal RC beams. The FRP flexural and shear strengthening RC beams has weakness in the spalling failure because the impact load concentrated the concrete face which is not strengthened with FRP sheets.

• Journal of the Korean earth science society
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• v.28 no.2
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• pp.147-158
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• 2007

The purpose of this study was to investigate research trends of Japanese earth science education published in Chigakukyouiku by the Japan Society of Earth Science Education. A total of 129 articles published in the Journal between 1998 and 2003 were analyzed. The Journal published six issues each year, and each issue contained about four articles that were fewer numbers than Journal of the Korean Earth Science Society's. About Sixty percent of the papers were written by a single author. Analyzing the content of the papers, it was noted that the most articles were geology-related (41.1%) followed by oceanography-related (1.6%) and general science education papers (1.6%). In summary, the characteristics of research trends of Japanese earth science education are as follows: First, the most topics of the papers were related to environmental sciences including earthquake, volcano, and tsunami. This trend seems natural because Japanese schools are situated within the reach of these environmental events. Second, there found many papers that dealt with geological field trip or fossils adjacent to the local community. Third, there were several papers that established a relationship between environmental education and earth science education. Obviously these papers tried to incorporate environmental education into earth science education at the school level. Last but not least, there found an effort to introduce computer into earth science education as an innovative educational method, for example, 'computer and earth science education'.

• The Journal of Art Theory & Practice
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• no.13
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• pp.35-71
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• 2012

The purpose of this essay is to examine the responses of artists on nuclear experiences through an analysis of the nuclear images represented in contemporary Japanese art. Japan has previously as twice experienced nuclear disaster in 20th century. The first atomic bombs were dropped in 1945 as well as the 5th Fukuryumaru, Japanese pelagic fishing boat, exposed by hydrogen bomb test operated by the US in 1954 nearby Bikini atoll. Due to Tsunami taken place by the great earthquake that caused the meltdown of Fukushima Nuclear Power Plant in March 2010, Japan is being experienced a nuclear disaster again. Despite practical experiences, comtemporary Japanese art has avoided the subject of nuclear disasters since the end of the Asia-Pacific War for a variety of reasons. Firstly, GHQ prohibited to record or depict the terrible effect of atomic bomb until 1946. Secondly, Japanese government has tried to sweep the affair under the carpet quite a while a fact of nuclear damage to their people. Because Japan has produced numerous war record paintings during the Second World War, in the aftermath of the defeated war, most of Japanese artists thought that dealing with politics, economics, and social subject was irrelevant to art as well as style of amateur in order to erase their melancholic memory on it. In addition, silence that was intended to inhibit victims of nuclear disasters from being provoked psychologically has continued the oblivion on nuclear disasters. For these reasons, to speak on nuclear bombs has been a kind of taboo in Japan. However, shortly after the atomic bomb dropped on Hiroshima, the artist couple Iri and Toshi Maruki visited to ruin site as a volunteer for Victim Relief. They portrayed the horrible scenes of the legacy of nuclear bomb since 1950 based on their observation. Under the condition of rapid economical growth in 1960s and 1970s, Japanese subculture such as comics, TV animations, plastic model, and games produced a variety of post apocalyptic images recalling the war between the USA and Japanese militarism, and battle simulation based on nuclear energy. While having grown up watching subculture emerged as Japan Neo-Pop in 1990s, New generation appreciate atomic images such as mushroom cloud which symbolizes atomic bomb of Hiroshima. Takashi Murakami and other Neo-Pop artists appropriate mushroom cloud image in their work. Murakami curated three exhibitions including and persists in superflat and infantilism as an evidence in order to analyze contemporary Japanese society. However, his concept, which is based on atomic bomb radiation exposure experience only claimed on damage and sacrifice, does not reflect Japan as the harmer. Japan has been constructing nuclear power plants since 1954 in the same year when the 5th Fukuryumaru has exposed until the meltdown of Fukushima Nuclear Plant although took place of nuclear radiation exposures of Three Mile and Chernobyl. Due to the exploding of Fukushima Nuclear Power Plant, Japan reconsiders the danger of nuclear disaster. In conclusion, the purpose of this paper may be found that the sense of victim which flowed in contemporary art is able to inquire into the response of artist on the subject of nuclear as well as the relationship between society, politics, culture, and modern history of Japan and international political situation.

• Tunnel and Underground Space
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• v.27 no.6
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• pp.343-350
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• 2017

Amid increasingly saturated ground space, development of underground space has been booming throughout the world and excavation has been underway near the structure above or under the ground level. But the ground subsidence caused by improper or poor construction technologies, underground water leakage, sudden changes of stratum and the problem with earth retaining system component has been emerged as hot social issue. To deal with such problems nationwide, establishment of preventive and proactive disaster management and rapid restoration system has been pushed now. In this study, collection of the data on technology development trend to secure the underground safety was made, taking into account of internal change elements (changing groundwater level, damage to underground utilities, etc) and external change elements (vehicle load, earthquake and ground excavation, etc) during excavation. Amid the growing need of ground behavior analysis, ground subsidence evaluation technology, safe excavation to prevent ground subsidence and reinforcement technology, improvement of rapid restoration technology in preparation for ground subsidence and development of independent capability, this study is intended to introduce the technology development in a bid to prevent the ground subsidence during excavation. It's categorized into prediction/evaluation technology, complex detect technology, waterproof reinforcement technology, rapid restoration technology and excavation technology which, in part, has been in process now.

• Journal of Korean Society of Disaster and Security
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• v.13 no.1
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• pp.13-23
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• 2020

In 2005, Urban railway seismic design was introduced in Rep. Of Korea, and many studies on seismic performance evaluation and reinforcement methods were conducted. In accordance with the Enforcement Decree of the Earthquake Disaster Countermeasures Act issued in March 2009, during April 2010 to October 2013, some of local governments established detailed evaluation and reinforcement measures for seismic performance of the urban railway underground structure. Afterwards, the seismic performance reinforcement of the existing urban railway structures was conducted for the sections that a long period of used until the end of 2018, and the reinforcement works are carried out by various methods using the previously studied methods. However, various reinforcing materials and construction methods using have been studied, but the classification research on the construction methods currently applied to reinforcement construction of urban railways is insufficient. The purpose of study is to analysis the cases currently applied to seismic reinforcement construction and to show the characteristics of each construction method, the reasons for its application and problems.

• Atmosphere
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• v.16 no.1
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• pp.19-31
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• 2006

The purpose of this study is to develop the statistical model to predict sea level pressure of typhoon period in south coast of the Korean Peninsula. Seven typhoons, which struck south coast of the Korean Peninsula, are selected for this study, and the data for analysis include the central pressure and location of typhoon, and sea level pressure and location of 19 observing site. Models employed in this study are the first order regression, the second order regression and the neural network. The dependent variable of each model is a 3-hr interval sea level pressure at each station. The cause variables are the central pressure of typhoon, distance between typhoon center and observing site, and sea level pressure of 3 hrs before, whereas the indicative variable reveals whether it is before or after typhoon passing. The data are classified into two groups - one is the full data obtained during typhoon period and the other is the data that sea level pressure is less than 1000 hPa. The stepwise selection method is used in the regression model while the node number is selected in the neural network by the Schwarz's Bayesian Criterion. The performance of each model is compared in terms of the root-mean square error. It turns out that the neural network shows better performance than other models, and the case using the full data produces similar or better results than the case using the other data.

• Journal of the Korean Geotechnical Society
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• v.20 no.2
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• pp.115-124
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• 2004

Granular compaction pile has the load bearing capacity of the soft ground increase and has the settlement of foundation built on the reinforced soil reduce. The granular compaction group piles also have the consolidation of the soft ground accelerate and prevent the liquefaction caused by earthquake using the granular materials such as sand, gravel, stone etc. However, this method is not widely used in Korea. The granular compaction piles are constructed by grouping them with a raft system. The confining pressure at the center of bulging failure depth is a major variable in estimating the ultimate bearing capacity of the granular compaction piles. Therefore, a share of loading is determined considering the effect of load concentration ratio between the granular compaction piles and surrounding soils, and the variation of the magnitude of the confining pressure. In this study, a method for the determination of the ultimate bearing capacity is proposed to apply a change of the horizontal pressure considering bulging failure depth, surcharge, and loaded area. Also, the ultimate bearing capacity of the granular compaction pile is evaluated on the basis of previous study(Kim et al., 1998) on the estimation of the ultimate bearing capacity and compared with the results obtained from laboratory scale model tests and DEM numerical analysis using the PFC-2D program.