• Journal of the Korean Society of Hazard Mitigation
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• v.7 no.5
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• pp.47-60
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• 2007

In this paper, we investigate the natural frequencies and buckling loads of functionally graded material (FGM) plates and shells, using a quasi-conforming shell element that accounts for the transverse shear strains and rotary inertia. The eigenvalue of the FGM plates and shells are calculated by varying the volume fraction of the ceramic and metallic constituents using a sigmoid function, but their Poisson's ratios of the FGM plates and shells are assumed to be constant. The expressions of the membrane, bending and shear stiffness of FGM shell element are more complicated combination of material properties than a homogeneous element. In order to validate the finite element numerical solutions, the Navier's solutions of rectangular plates based on the first-order shear deformation theory are presented. The present numerical solutions of composite and sigmoid FGM (S-FGM) plates are proved by the Navier's solutionsand various examples of composite and FGM structures are presented. The present results are in good agreement with the Navier's theoretical solutions.

• Journal of the Korean Society of Hazard Mitigation
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• v.7 no.5
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• pp.61-71
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• 2007

Navier's and Finite element solutions based on the first-order shear deformation theory are presented for the analysis of through-thickness functionally graded plates and shells. The functionally graded materials are considered: a sigmoid function is utilized for the mechanical properties through the thickness of the isotropic structure which varies smoothly through the plate and shell thickness. The formulation of a nonlinear 9-node Element-based Lagrangian shell element is presented for the geometrically nonlinear analysis. Natural-coordinate-based strains are used in present shell element. Numerical results of the linear and nonlinear analysis are presented to show the effect of the different top/bottom elastic modulus, loading conditions, aspect ratios and side-to-thickness ratios on the mechanical behaviors. Besides, the result according to the variation of the power-law index of isotropic functionally graded structures is investigated.

• Journal of the Korean Society of Hazard Mitigation
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• v.4 no.1 s.12
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• pp.65-75
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• 2004

Roadbed failure due to the natural disaster may bring out social and economic damage such as the loss of life and property, the consumption of time and cost for recovery, and the delay of logistics in railway In this study, the method using geosynthetic soilbag was applied to rehabilitation of the railway roadbed which was failed by disaster. The full scale tests with the simulated train loading were performed in order to evaluate the static and dynamic performance at the railway roadbed using geosynthetic soilbag. The results of these tests were compared with unreinforced and reinforced cases with geosynthetic soilbag, respectively The data gathered by various measurement devices from these full scale tests would be useful to evaluate and understand the roadbed with geosynthetic soilbag. In conclusion, geosynthetic soilbag was evaluated as a permanent restoration method to reinforce the roadbed of railway.

• Journal of the Korean Society of Hazard Mitigation
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• v.8 no.4
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• pp.17-22
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• 2008

Including heat wave, Climate change caused 150,000 casualty in 2000 and heat waves are meteorological events that pose a serious threat to human health. A heat wave is defined as "a period of abnormally and uncomfortably hot and usually humid weather". There is a need for the prevention of health effects due to weather and climate extremes. This study intends to propose the necessity of Response System to correspond to extreme heat. And this research focused on Cooling Center manual of facility and maintenance for extreme heat disaster. It would be useful to be planned based on community and to be taken a role as an E.O.C.(Emergency Operating Center). As a conclusion elderly watching system and the requirements regional cooling center facility was proposed.

• Journal of the Korean Society of Hazard Mitigation
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• v.8 no.3
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• pp.11-21
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• 2008

A linear and non-linear analysis for plates and shells with arbitrary edge supports subjected to various loading was presented. The 9-node ANS(Assumed Natural Strain) hell element was employed and the spring element, which could express an arbitrary edge support using the six degrees of freedom, was introduced. For the application of his analysis, the plates and shells with various edge supports were analyzed, and the ending behavior with these edge supports were obtained accurately. For these edge supports, particularly elastic edge support was simulated by six springs and reasonable results were obtained. The results show that the present method can be widely used to analyze the bending behavior of plates and shells with arbitrary edge conditions.

• Journal of the Korean Society of Hazard Mitigation
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• v.10 no.6
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• pp.35-43
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• 2010

This study was carried out to find reliable relations between various concrete strength properties which are used as input data in concrete pavement design program. Concretes were made from different sources of coarse grained(granite, limestone and sandstone) and fine grained aggregates such as natural sand, washed sand and crushed sand. From strength test results, model equations were obtained based on the relation between strengths. For each coarse grained aggregate, models for compression-flexural strengths, compression-split tensile strengths, compressive strength-modulus and flexural-split tensile strengths with age were obtained. For concrete mixed with gneiss granite aggregates, concrete strengths were obtained from numerical mean values of concrete strengths mixed with fine grained aggregates. In addition models for concrete split tensile strengths and modulus values were provide by averaging numerically the estimated values obtained from the derived relationship and the experimental values. This is due to more scattered values of split tensile strengths and modulus values than other strength properties. Finally criteria for drying shrinkage strain as well as Poisson's ratio for concrete used in pavement were presented for all mixes with differed coarse grained aggregates.

• Journal of the Korean Society of Hazard Mitigation
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• v.7 no.2 s.25
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• pp.35-44
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• 2007

Plowable fill is generally a mixture of sand, fly ash, a small amount of cement and water. Sand is the major component of most flowable fill mixes. Marine dredged soil was adopted for flowable fill instead of fly ash. Natural sea sand and in-situ soil were used for comparison. The flow behavior, hardening characteristics, and ultimate strength behavior of flowable fill were investigated. The unconfined compression test necessary to sustain walkability as the fresh flowble fill hardens was determined and the strength at 3-days appeared to correlate well with the water-to-cement ratio. The strength parameters, like cohesion and internal friction angle, was determined along the curing time. The creep test for settlement potential was conducted. Also, potable falling weight deflectometer(PFWD) test has been carried out for elastic modulus of each controlled low strength materials(CLSM). The data presented show that marine dredged soil and in-situ soil can be successfully used in CLSM.

• Korean Security Journal
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• no.3
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• pp.83-116
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• 2000

Many concerns have been raised for importance of disaster management after 1990's numerous urban disasters in Korea. When the primary function of government is to protect lives and property of citizens, disaster management should be included in the mainstream of public administration and many hazard countermeasures should be carried out for that purpose. The principal purpose of this research is to establish ways and means needed to improve the disaster management system in Korea. This paper is split into five chapters. Chapter I is the introduction part. Chapter II introduces the reader to a disaster management theory, and deals with various disaster management systems of foreign countries such as the U.S.A. and Japan, Chapter III describes and characterizes the Korea's current disaster management system. The Korean disaster management system has been reestablished through the enactment of the Disaster Management Act of 1995 and the full revision of Natural Hazards Management Act of 1995 after series of catastrophic man-made disasters since 1993. Chapter IV is devoted to the establishment of an effective disaster management system in Korea. In this chapter, I discusses measures needed to improve the quality of CDMB(Central Disaster Management Bureau)'s service to the people. I strongly reemphasize the effectiveness of a comprehensive risk-based, all-hazard national emergency management system that addresses preparedness, mitigation, response, and recovery. To that end the Administration should develop legislation, new policies, and organizational plans to invigorate the agency with a refocussed mission. Chapter V is a conclusion. As the demand for citizens'welfare has been continuously increased in the localization, the importance of disaster management is emerging subject in the public sector. The disaster management carries out complicated affairs and manages diverse objects, the cooperation/connection system of the central-local government and citizens, and non-governmental organization should be established.

• Journal of Korea Water Resources Association
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• v.48 no.12
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• pp.1037-1049
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• 2015

The most of natural disasters that occur in North Korea are flood, typhoon and damage from heavy rain. The damage caused by those disasters since the mid-1990s is aggravating North Korea's economic difficulties every year. By recognizing the seriousness of the damages from the floods, the North Korean government has carried out the river maintenance, farmland restoration, land readjustment and afforestation projects since the last-1990s, but it has failed preventing the damages. In order to estimate the degree of flood risk regarding damage from chronic floods that occur inveterately in North Korea, this research conducted an additional simulation for rainfall-runoff analysis to reflect the characteristics of the ungauged area that make foreign countries hard to obtain the hydrological data and do not open the topographical data to public. In addition, this research estimates the degree of flood risk by selecting the factors of the hazard, exposure and vulnerability by following the standards of the Intergovernmental Panel on Climate Change (IPCC).

• The Journal of Engineering Geology
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• v.18 no.3
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• pp.303-309
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• 2008

A probability of slope hazards was predicted at a natural terrain around the stone relics of Jinjeon-saji area, which is located in Yangyang, Kangwon Province. As the analyzing results of field investigation, laboratory test and geology and geomorphology data, the effect factors of landslides occurrence were evaluated. Also, the landslides prediction map was made up using the prediction model by the effect factors. The landslide susceptibility of stone relics was investigated as the grading classification of occurrence probability. In the landslides prediction map, the high probability area was $3,489m^2$ and it was 10.1% of total prediction area. The high probability area has over 70% of occurrence probability. If landslides are occurred at the predicted area, the three stories stone pagoda of Jinjeon-saji(National treasure No. 122) and the stone lantern of Jinjeon-saji(Treasure No.439) will be collapsed by debris flow.