• Proceedings of the Computational Structural Engineering Institute Conference
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• 1997.04a
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• pp.27-34
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• 1997

In this paper, systematic and comprehensive approaches are suggested for the application of quantitative PRA techniques especially for those risk events that cannot be easily evaluated quantitatively In addition, dominant risk events are identified based on their occurrence frequency assessed by both actual survey of construction site conditions and the statistical data related with the probable accidents. Practical FTA(Fault Tree Analysis) and ETA(Event Tree Analysis) models are used for the assessment of the identified risks. When the risk events are lack of statistical data, appropriate Bayesian models incorporating engineering judgement and test results are also introduced in this paper. Moreover, a fuzzy probability technique is used for the quantitative risk assessment of those risk components which are difficult to evaluate quantitatively.

• Proceedings of the Korea Water Resources Association Conference
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• 2012.05a
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• pp.373-373
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• 2012

위험도(risk)는 복잡성(complexity)과 불확실성(uncertainty)라는 2가지 주요 특징으로 인해 위험도를 정확하게 예측하는 것은 불가능하다. 대표적인 수공구조물인 댐이 각종 모니터링을 통해서 안전하다고 판단된다 하더라도 하류지역에 도시가 존재한다면 여전히 잔존위험도(residual risk)는 존재한다. 댐의 파괴가 일반적으로 발생하는 사상은 아니지만 대규모 인명피해, 재산 및 환경피해로 이어지기 때문에 작은 위험도라 할지라도 이에 대한 감시 및 관리가 필수적이다. 댐 위험도 분석을 위해서 Event Tree 또는 Fault Tree가 일반적인 해석 방법으로 이용되고 있으나 잠재적인 파괴모드에 대한 복잡성과 불확실성을 고려하는데 한계가 존재한다. 본 연구에서는 이러한 문제점을 개선하기 위해서 Bayesian Network 기반의 위험도 해석기법을 제안하고자 한다. 특히 수문학적 위험도와 관련된 분석을 위해서 Bayesian Network의 구성 방안, 매개변수 추정, 위험도 해석 등 기존 해석 방법을 개선한 댐 위험도 해석 기법을 개발하고자 하며 개발된 방법론을 국내 실제댐에 적용하여 적합성을 평가하였다.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2023.11a
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• pp.222-224
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• 2023

자율운항선박의 해상 운용은 인간의 개입 최소화 등 새로운 운용 방식의 적용과 첨단 디지털기술의 적용으로 기존 선박의 운용과 다른 형태의 다양한 새로운 위험요소들이 발생할 것으로 예상되며, 이러한 위험을 분석하기 위한 적절한 위험도평가 방법론의 적용이 요구될 것이다. 본 연구는 기존 선박과 달리 인간의 개입이 최소화된 상태로 운용되는 자율운항선박의 화재 사고 위험도를 실시간으로 분석하기 위한 실시간 위험도 모델의 개발을 목적으로 수행되었다. 자율운항선박 화재 위험도 모델 개발을 위하여, 먼저 자율운항선박의 화재 감지 및 제어, 비상대응 기능들을 분석하고, 기능분석 결과를 바탕으로 화재 감지 및 제어 시스템들에 대한 Fault Tree Analysis를 수행하였다. 자율운항선박의 화재 시나리오 표현을 위하여 기관구역 화재와 화물구역 화재로 분류하여 Event Tree Analysis를 수행하였다. 또한, 자율운항선박 운용 외부 조건에 따라 변화하는 변수들을 식별하여 각 변수들의 변화로 인하여 발생할 수 있는 자율운항선박 화재 위험도 변화량을 검토하였다.

• Journal of Hydrogen and New Energy
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• v.26 no.2
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• pp.192-198
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• 2015

Fault Tree Analysis to predict the lifetime in the design process of LNG compressor is considered. Fault Trees for P & ID of the compressor are created. Individual components that comprise the compressor are configured with the basic event. The failure rates in the PDS and OREDA are applied. As results, the system failure rate and the reliability over time are obtained. Further, the power transmission and the shaft seal system is confirmed to confidentially importantly contribute to the overall lifetime of the system. These techniques will help to improve the reliability of design of large scale machinery such as a plant.

• International Journal of High-Rise Buildings
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• v.3 no.4
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• pp.297-304
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• 2014

Recently, there have been some reported examples of structural collapse due to gravity, subsequent to damage from accident or an excitation that was not prepared for in the design process. A close view of new concepts, such as a redundancy and key elements, has been taken with the aim of ensuring the robustness of a structure, even in the event of an unexpected disturbance. The author previously proposed a sensitivity index of the vertical load carrying capacity to member disappearance for framed structures. The index is defined as the ratio of the load carrying capacity after a member or a set of an adjacent member disappears, to the original load carrying capacity. The member with the highest index may be regarded as a key element. The concept of bio-mimicry is being applied to various fields of engineering, and tree-shaped structures are sometimes used for the design of building structures. In this study a sensitivity analysis is applied to the irregular-framed structures such as tree-shaped structures.

• Proceedings of the Korean Institute of Industrial Safety Conference
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• 2002.05a
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• pp.339-345
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• 2002

FTA(Fault free Analysis)는 시스템 고장을 발생시키는 사상(event)과 그의 원인과의 인과관계를 논리기호(AND 와 OR)를 사용하여 나뭇가지 모양의 그림으로 나타낸 고장수목(Fault Tree)을 만들고, 이에 의거하여 시스템의 고장확률을 구함으로써 문제가 되는 부분을 찾아내어 시스템의 신뢰성을 개선하는 정량적 고장해석 및 신뢰성 평가 방법이다.(중략)

• Journal of Korean Society of Industrial and Systems Engineering
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• v.23 no.54
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• pp.155-165
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• 2000

The fault diagnosis is a systematic and unified method to find based on the observing data resulting in noises. This paper presents the fault prediction and diagnosis using fuzzy expert system technique to manipulate the uncertainties efficiently in predictive perspective. We apply a fuzzy event tree analysis to the computer system, and build up the fault prediction and diagnosis using fuzzy expert system that predicts and diagnoses the error of the system in the advance of error.

• Journal of the Korean Geosynthetics Society
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• v.16 no.4
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• pp.129-137
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• 2017

In this study, the prediction of landslide probability was performed to the study area located in ${\bigcirc}{\bigcirc}$ area of Muan-gun, Jeonnam Province around Honam railway using the computer program SHAPP ver 1.0 developed by a decision tree model. The soil samples were collected at total 8 points, and soil tests were performed to measure soil properties. The thematic maps of soil properties such as coefficient of permeability and void ratio were made on the basis of soil test results. The slope angle analysis of topography was performed using a digital map. As the prediction result of landslide probability, 435 cells among total 15,552 cells were predicted to be in the event of landslides. Therefore, the predicted area of occurring landslides may be $43,500m^2$ because the analyzed cell size was $10m{\times}10m$.

• Journal of the Korea Convergence Society
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• v.12 no.8
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• pp.39-45
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• 2021

This paper discusses how to handle incomplete data including missing values. Optimally processing the missing value means obtaining an estimate that is the closest to the original value from the information contained in the training data, and replacing the missing value with this value. The way to achieve this is to use a decision tree that is completed in the process of classifying information by the classifier. In other words, this decision tree is obtained in the process of learning by inputting only complete information that does not include loss values among all training data into the C4.5 classifier. The nodes of this decision tree have classification variable information, and the higher node closer to the root contains more information, and the leaf node forms a classification region through a path from the root. In addition, the average of classified data events is recorded in each region. Events including the missing value are input to this decision tree, and the region closest to the event is searched through a traversal process according to the information of each node. The average value recorded in this area is regarded as an estimate of the missing value, and the compensation process is completed.

• Fire Science and Engineering
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• v.15 no.1
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• pp.84-92
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• 2001

In today's world, rise in the establishment of social infrastructure resulting from population saturation in large cities has led to more extensive and frequent use of chemical materials on facilities. A result, unexpected and serious accidents, hazards, contingencies and disasters are more prevalent than ever. Such phenomenon calls for more devoted and concerted efforts towards finding ways to reduce the safety hazards that are seen to take place more often than before with the increase in the number of facilities that are prone to bring disaster and hazard coupled with the conventional safety problems that continue to exist even today. In developed countries, such challenge is addressed by various appropriate countermeasures drawn up by local professional committees on industrial facilities, whose members conduct offsite and onsite evaluation un the potential industrial disasters and its seriousness and provide their advice thereof. Against this backdrop, this study aims at identifying a comprehensive safety allowance level (safety acceptable level) when imposing limitation on the development of conventional or new facilities, for the fur pose of establishing a safety allowance level of disastrous and dangerous facilities in Korea. This is done by assessing and applying the level of danger each individual is exposed to in a randomly selected region (disastrous and dangerous areas in Seoul) based on probability of quantitative hazards, as well as simulation and calculation methods which include: i) social disaster evaluation method applying Quantified Risk Assessment of Health & Safety Executive of UK and Matrix of Risk of Evaluated Sources of Hazard; ii) Fault Tree or Event Tree Analysis and etc.