• Structural Engineering and Mechanics
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• 제50권5호
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• pp.617-633
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• 2014

Because the elevated temperature degrades the mechanical properties of materials used in containments, the global behavior of containments subjected to the internal pressure under high temperature is remarkably different from that subjected to the internal pressure only. This paper concentrates on the nonlinear finite element analyses of the nuclear power plant containment structures, and the importance for the consideration of the elevated temperature effect has been emphasized because severe accident usually accompanies internal high pressure together with a high temperature increase. In addition to the consideration of nonlinear effects in the containment structure such as the tension stiffening and bond-slip effects, the change in material properties under elevated temperature is also taken into account. This paper, accordingly, focuses on the three-dimensional nonlinear analyses with thermal effects. Upon the comparison of experiment data with numerical results for the SNL 1/4 PCCV tested by internal pressure only, three-dimensional analyses for the same structure have been performed by considering internal pressure and temperature loadings designed for two kinds of severe accidents of Saturated Station Condition (SSC) and Station Black-out Scenario (SBO). Through the difference in the structural behavior of containment structures according to the addition of temperature loading, the importance of elevated temperature effect on the ultimate resisting capacity of PCCV has been emphasized.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 1998년도 추계 학술발표회 논문집 Proceedings of EESK Conference-Spring 1998
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• pp.335-342
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• 1998

A soil-structure interaction (SSI) experiment is being conducted in a seismically active region in Hualien, Taiwan. To obtain earthquake data for quantifying SSI effects and providing a basis to benchmark analysis methods, a 1/4-th scale cylindrical concrete containment model similar in shape to that of a nuclear power plant containment was constructed in the field where both the containment model and its surrounding soil, surface and sub-surface, are extensively instrumented to record earthquake data. In between September 1993 and May 1996, fifteen earthquakes with Richter magnitudes ranging from 4.2 to 6.2 were recorded. The recorded data were analyzed to provide information on the response characteristics of the Hualien soil-structure system, the SSI effects and the ground motion characteristics. The ground response data were analyzed for their variations with depth, with distance from the model structure, and at the same depths along downhole arrays. Variations of soil stiffness and soil-structure system frequencies were also evaluated against maximum ground motion. In addition, the site soil properties were derived based on correlation analysis of the recorded data and then correlated with those from the geotechnical investigation data.

• 한국지반신소재학회논문집
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• 제7권3호
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• pp.1-7
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• 2008

본 연구에서 검토한 지오텍스타일 컨테이너와 튜브를 활용한 수로구조물은 UAE에서 수행한 프로젝트로 수심이 4.0m 이하인 경우 지오텍스타일 컨테이너를 저개식 바지로부터 해저바닥에 착지시키는 방법으로 시공하고 그 윗부분은 지오텍스타일 튜브로 시공을 수행하였다. 따라서, 본 연구에서는 지오텍스타일 컨테이너와 튜브를 활용하여 해상의 발전소 방파제 수로구조물 축조 시 고려된 구조물의 개별 및 다단구조물의 안정성, 지오텍스타일 재질 선택에 관련한 설계인자를 분석하였다. 또한, 방파제 구조물이 위치한 현장이 발전소의 용수의 유입과 유출이 발생하는 구역으로 발전소 유출입수의 온도가 방파제 구조물 내부의 온도변화에 미치는 영향에 대하여 분석하였다.

• Structural Engineering and Mechanics
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• 제41권4호
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• pp.559-573
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• 2012

An adaptive modeling and simulation technique is introduced for the effective and reliable fluid-structure interaction analysis using MSC/Dytran for large-scale complex pressurized liquid containment. The proposed method is composed of a series of the global rigid sloshing analysis and the locally detailed fluid-structure analysis. The critical time at which the system exhibits the severe liquid sloshing response is sought through the former analysis, while the fluid-structure interaction in the local region of interest at the critical time is analyzed by the latter analysis. Differing from the global coarse model, the local fine model considers not only the complex geometry and flexibility of structure but the effect of internal pressure. The locally detailed FSI problem is solved in terms of multi-material volume fractions and the flow and pressure fields obtained by the global analysis at the critical time are specified as the initial conditions. An in-house program for mapping the global analysis results onto the fine-scale local FSI model is developed. The validity and effectiveness of the proposed method are verified through an illustrative numerical experiment.

• 한국전산구조공학회논문집
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• 제25권5호
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• pp.381-388
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• 2012

본 연구에서는 Steel Fiber를 원전 격납건물에 적용하기 위한 적용성 평가를 위해서 Steel Fiber가 삽입된 격납건물에 대한 지진위험도 평가를 수행하였다. Steel Fiber를 콘크리트에 삽입함으로써 콘크리트의 구조적 성능에서 취약점인 인장성능을 향상시킬 수 있고, 압축강도 및 전단강도도 증가시킬 수 있는 장점이 있기 때문이다. 그러나 아직까지 원전 격납건물에 Steel Fiber를 적용하기 위한 노력은 진행되고 있지 않다. 재료적 우수성에도 불구하고 원전에 적용하기 위해서는 좀 더 많은 사용경험과 성능검증이 이루어져야 가능할 것이다. 따라서 본 연구에서는 원자력발전소 격납건물에 Steel Fiber를 사용하였을 경우, 격납건물의 지진안전성의 변화를 살펴보기 위하여 기존의 실험자료를 이용하여 취약도 평가를 수행하였다. 분석결과 Steel Fiber의 함유로 인하여 전단성능과 연성능력이 증가하여 지진취약도의 향상으로 나타났다. Steel Fiber함유량이 1.0%인 경우 지진내력이 10%가량 증가하는 효과를 얻을 수 있었다. 그러나 본 연구의 결과는 제한된 기존의 실험결과를 이용한 예비해석이므로 Steel Fiber의 실제 적용성을 적확하게 분석하기 위해서는 Steel Fiber가 함유된 다양한 콘크리트 부재실험을 통하여 그 물성의 변화를 파악하여야 할 것이다.

• 한국가스학회지
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• 제12권1호
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• pp.36-41
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• 2008

본 논문에서는 완전밀폐식 LNG 저장탱크의 외부탱크 측벽면과 지붕 구조물에 대한 강도안전성을 유한요소법으로 해석하였다. 예응력 콘크리트 구조물로 건설된 외부탱크는 내부탱크의 붕괴로 인해 발생하는 LNG 유체정압과 유체동압, 그리고 태풍을 포함한 외부의 풍압하중을 받는다. FEM 해석결과에 의하면, 외부탱크의 측벽면과 지붕 구조물이 서로 연결되는 링빔 구조물은 저장탱크에 작용하는 대부분의 내 외부 하중을 담당하고 있다. 이러한 해석결과는 외부탱크의 설계 포인트를 링빔에 두고, 그 다음은 지붕구조물의 중심부에 대한 설계 안전성을 검토하는 것이다. 완전밀폐식 LNG 저장탱크 해석에서 사용한 해석모델은 LNG 누설에 의한 내부압력 및 태풍과 같은 외부압력이 결합된 복합하중에서도 안전한 강도안전성을 유지하고 있음을 알 수 있다.

• 한국정보과학회논문지:데이타베이스
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• 제32권3호
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• pp.326-333
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• 2005

많은 XML 응용들은 XML 문서에 대한 질의 언어로 XPath 패턴을 사용한다. XPath 패턴들 사이에는 포함 관계가 존재할 수 있으며, 하나의 XPath 패턴이 다른 XPath 패턴을 포함하는지를 결정하는 문제를 포함 문제라고 한다. 포함 문제는 많은 응용들에서 발생하고 있지만 co-NP complete 문제로 알려져 있다. 한편 XPath 패턴들 사이의 준동형 관계는 포함 관계의 충분 조건이면서 다항 시간에 얻을수 있다. 본 논문에서는 준동형 문제가 포함 문제를 대체하여 유용하게 쓰일 수 있는 응용들에 대해 논의하고, XPath 패턴들 사이의 준동형 정보를 유지하면 많은 이점을 얻을 수 있다는 사실에 대해 논의한다. 그리고 XPath 패턴들 사이의 준동형 관계를 유지하기 위하여 POX(Partially Ordered Set of XPath Patterns)라는 래티스 구조를 제안하고, 그것을 유지할 수 있는 알고리즘을 개발한다. 알고리즘 분석을 보면 알 수 있듯이, 본 논문에서 제안하는 알고리즘은 다항 시간에 POX를 효율적으로 유지할 수 있다.

• International Journal of Naval Architecture and Ocean Engineering
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• 제5권2호
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• pp.227-245
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• 2013

Reliable strength assessment of the Liquefied Natural Gas (LNG) cargo containment system under the sloshing impact load is very difficult task due to the complexity of the physics involved in, both in terms of the hydrodynamics and structural mechanics. Out of all those complexities, the proper selection of the design sloshing load which is applied to the structural model of the LNG cargo containment system, is one of the most challenging one due to its inherent randomness as well as the statistical analysis which is tightly linked to the design sloshing load selection. In this study, the response based strength assessment procedure of LNG cargo containment system has been developed and proposed as an alternative design methodology. Sloshing pressure time history, measured from the model test, is decomposed into wavelet basis function targeting the minimization of the number of the basis function together with the maximization of the numerical efficiency. Then the response of the structure is obtained using the finite element method under each wavelet basis function of different scale. Finally, the response of the structure under entire sloshing impact time history is rapidly calculated by synthesizing the structural response under wavelet basis function. Through this analysis, more realistic response of the system under sloshing impact pressure can be obtained without missing the details of pressure time history such as rising pattern, oscillation due to air entrapment and decay pattern and so on. The strength assessment of the cargo containment system is then performed based on the statistical analysis of the stress peaks selected out of the obtained stress time history.

• Structural Engineering and Mechanics
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• 제36권6호
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• pp.729-744
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• 2010

There is world wide concern for safety of nuclear power installations after the terrorist attack on World Trade Center in 2001 and several other civilian structures in the last decade. The nuclear containment structure in many countries is a double shell structure (outer shell a RCC and inner a prestressed concrete). The outer reinforced concrete shell protects the inner shell and is designed for external loading like impact and blast. A comparative study of non-linear response of reinforced concrete nuclear containment cylindrical shell subjected to impact of an aircraft (Phantom) and explosion of different amounts of blast charges have been presented here. A material model which takes into account the strain rate sensitivity in dynamic loading situations, plastic and visco-plastic behavior in three dimensional stress state and cracking in tension has been developed earlier and implemented into a finite element code which has been validated with published literature. The analysis has been made using the developed software. Significant conclusions have been drawn for dissimilarity in response (deflections, stresses, cracks etc.) of the shell for impact and blast loading.

• 한국압력기기공학회 논문집
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• 제16권1호
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• pp.37-41
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• 2020

The Nuclear containment building is a main safety-related structure that performs shielding and conservation functions to prevent highly radioactive materials from leakage to the outside environment in the case of various environmental conditions and postulated accidents. The containment building contains a reactor, steam generator, pressurizer, tank, reactor coolant system, auxiliary system and engineering safety system, and is designed so that highly radioactive materials above the limits specified in 10 CFR 100 do not escape to the outside environment in the case of LOCA(Loss of Coolant Accident) for instance. The containment metal liner plate(CLP) is a carbon steel plate with a nominal plate thickness of 6 mm, which functions as a mold for the wall and dome of the containment building when concrete is filled, fulfills airtightness to prevent leakage of seriously radioactive materials. In recent years, backside corrosion was found on the liner plate in some domestic nuclear power plants. The main cause of backside corrosion was unfilled concrete. In this paper, an inspection technique of assessing filling suitability for CLP backside concrete is developed. Results show that the validity of inspection technique for CLP backside concrete using vibration sensor is successfully verified.