• KSCE Journal of Civil and Environmental Engineering Research
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• v.1 no.1
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• pp.33-42
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• 1981

Current standard code for R.C. design consists of two conventional design parts, so called WSD and USD, which are based on ACI 318-63 and 318-71 code provisions. The safety factors of our WSD and USD design criteria which are taken primarily from ACI 318-63 code are considered to be not appropriate compared to out country's design and construction practices. Furthermore, even the ACI safety factors are not determined from probabilistic study but merely from experiences and practices. This study investigates the safety level of R.C. flexural members designed by the current WSD safety provisions based on Second Moment Reliability theory, and proposes a rational but efficient way of determining the nominal safety factors and the associated flexural allowable stresses of steel bars and concretes in order to provide a consistent level of target reliability. Cornell's Mean First-Order Second Moment Method formulae by a log normal transformation of resistance and load output variables are adopted as the reliability analysis method for this study. The compressive allowable stress formulae are derived by a unique approach in which the balanced steel ratios of the resulting design are chosen to be the corresponding under-reinforced sections designed by strength design method with an optimum reinforcing ratio. The target reliability index for the safety provisions are considered to be ${\beta}=4$ that is well suited for our level of construction and design practices. From a series of numerical applications to investigate the safety and reliability of R.C. flexural members designed by current WSD code, it has been found that the design based on WSD provision results in uneconomical design because of unusual and inconsistent reliability. A rational set of reliability based safety factors and allowable stress of steel bars and concrete for flexural members is proposed by providing the appropriate target reliability ${\beta}=4$.

• Proceedings of the KIEE Conference
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• 2005.05a
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• pp.84-86
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• 2005

The digital systems such as PLC or DCS have been applied to non-safety systems of nuclear power plants because of many difficulties in using analog systems. Nowadays, digital systems have been applied to safety systems of the plants such as reactor protection system. One of the main advantages of digital systems is applicability of automatic testing methods to the systems. The protection system requires high-reliability and high-availability because it shall minimize the propagation of abnormal or accident conditions of nuclear power plants. The calculation of reliability and availability of systems depends on the maintenance period of the system. In general, the maintenance period of the protection system is one-month in case of the manual test. However, the cycle of test can be shortened in several hours by using automatic periodic testing. The reliability and availability of the system is better when test period is shortened because the reliability and availability is inverse proportion to the test period. In this research, we developed the automatic periodic testing method for KNICS Reactor Protection System, which can test the system automatically without an operator or a tester. The automatic testing contained all functions of reaction protection systems from analog-to-digital conversion function of the bistable Processor to the coincident trip function of the coincident processor. By applying the automatic periodic testing to reaction system, the maintenance cost can be cut down and the reliability can be increased.

• Journal of Institute of Control, Robotics and Systems
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• v.19 no.4
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• pp.328-333
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• 2013

Since a slight malfunction of control systems in a nuclear power plant may cause huge catastrophes, such control systems usually have multiple redundancy and reliable features, and their reliability and availability should be analyzed and verified thoroughly. This paper performed the reliability analysis of the SPLC (Safety Programmable Logic Controller) that is under developed as the control systems for the next generation nuclear power plant. One of the key features of SPLC is that it has multiple redundancy modes as faults happen, which means the reliability analysis for one fixed redundant model is not enough to analyze the reliability of SPLC. With considering this reconfigurable concept, FTA (Fault Tree Analysis) was used to capture fault-relationship among sub-modules. The analysis results show that MTTF (Mean Time to Fault) of SPLC is 45,080 hours, which is a about 4.5 times longer than the regulation, 10,000 hours.

• Proceedings of the KSR Conference
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• 2007.05a
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• pp.45-57
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• 2007

During the design phase of a system, which requires high reliability and safety such as aircraft, high speed train and nuclear power plant, reliability engineer must set up the target system reliability. To meet a reliability goal for the system, reliability allocation should be done gradually from the system to its element. For this end, first of all, we need to construct functional block diagram based on the design output and PWBS(Project Work Breakdown System). Another important input data for reliability allocation is the relationship between the cost and the reliability. In this study we investigate various reliability allocation models, which can be applicable to aircraft, vehicle, and power plant, and etc. And we suggest a proper reliability allocation model which can be effectively applicable to KTX-II high speed train to achieve the target system reliability.

• Proceedings of the Safety Management and Science Conference
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• 2012.04a
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• pp.293-300
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• 2012

Reliability measures of questionnaire and ${\chi}^2$ contingency tests of categorized responses are most practical tools to analyze the characteristics of subjects of survey study. This research evaluates the Cronbaha's reliability measures by using Repeated Measure Design (RMD) with illustrated MINITAB examples. In addition, ${\chi}^2$ statistics of each cell of categorized tables can be effectively interpreted with the symmetric plot of correspondence analysis. The practical example is also discussed to provide comprehensive understanding of topic.

• Smart Structures and Systems
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• v.33 no.4
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• pp.313-323
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• 2024

Deterioration of buildings is one of the biggest problems in modern society, and the importance of a safety diagnosis for old buildings is increasing. Therefore, most countries have legal maintenance and safety diagnosis regulations. However, the reliability of the existing safety diagnostic processes is reduced because they involve subjective judgments in the data collection. In addition, unstructured tasks increase rework rates, which are time-consuming and not cost-effective. Therefore, This paper proposed the method that can calculate the safety grade of deterioration automatically. For this, a DNN structure is generated by using existing precision inspection data and precision safety diagnostic data, and an objective building safety grade is calculated by applying status evaluation data obtained with a UAV, a laser scanner, and reverse engineering 3D models. This automated process is applied to 20 old buildings, taking about 40% less time than needed for a safety diagnosis from the existing manual operation based on the same building area. Subsequently, this study compares the resulting value for the safety grade with the already existing value to verify the accuracy of the grade calculation process, constructing the DNN with high accuracy at about 90%. This is expected to improve the reliability of aging buildings in the future, saving money and time compared to existing technologies, improving economic efficiency.

• 한국가스학회:학술대회논문집
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• 2003.10a
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• pp.14-31
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• 2003

• Proceedings of the Safety Management and Science Conference
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• 2000.11a
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• pp.27-30
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• 2000

• Journal of the Ergonomics Society of Korea
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• v.35 no.2
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• pp.75-84
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• 2016

Objective: The aim of this study is to suggest some improvement ideas based on the validity and the reliability analyses of the current safety culture measurement method applied to the Korean nuclear power industry. Background: Wrong safety culture is known as one of the major causes of the disasters such as the space shuttle Columbia disaster or the Fukushima Nuclear Power Plant accident. Assessment of safety culture of an organization is important to build a safer organizational environment as well as to identify the risks hidden in the organization. Method: A face validity of the current safety culture measurement method was analyzed by comparison of the key factors of safety culture in the Korean nuclear power industry with those factors reviewed in the previous studies. The current interview method was analyzed to identify the problems which degrade the consistency of evaluation. Results: Most safety culture factors reviewed in the literatures are covered in the list of the Korean nuclear power industry safety culture factors. However the unstructured questions used in the interview may result in inconsistency of safety culture evaluation among interviewers. Conclusion: This study suggests some examples which might improve the consistency of interviewers' evaluation on safety culture such as a post interview evaluation form. Application: An extended post interview evaluation form might help to increase the accuracy of the interviewing method for Korean nuclear industry safety culture evaluation.

• Proceedings of the KSR Conference
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• 2011.10a
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• pp.1412-1417
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• 2011

Safety is soaring up as a core value in accordance with the recent improvement of operating speed & incidents. rolling stock is a kind of system which works together with several components. one component has an effect on the sub-system, which can cause to the train safety operation, therefore reliability management of the major components of rolling stock is a kind of solution to the safety operation of train, but realistically maintenance in korea performed based on period rather than TBO of major components, but Japan does new maintenance system based on the major components, which optimizes maintenance tasks. actually Japan can apply to new maintenance system because they are ready in planning step but in this study, making a reliability data of major components and review the adaptability of new maintenance system to the rolling stock operating in Ansan line.