• Journal of the Korea institute for structural maintenance and inspection
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• v.1 no.2
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• pp.131-140
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• 1997

콘크리트 교량을 저렴하고 신속하게 상태 평가를 하기 위하여 성능 지수(Performance Index)를 제안한다. 이 기법은 육안 검사에 의하여 발견된 결함의 범위와 심각도를 사용하여 콘크리트 교량의 전반적인 상태를 신속하게 등급화 하고 콘크리트 교량의 노출 조건을 고려하여 콘크리트 성능을 정량적으로 평가한다. 또한 본 연구에서는 상기한 성능 지수 기법의 타당성을 증명할 수 있는 정밀 안전 진단 시험결과를 활용하여 6개의 주요 노후화 원인을 고려하는 또 다른 성능 지수를 제안한다. 이러한 두 상태 평가 방법이 영국의 실제 교량 상태 평가 자료를 바탕으로 한 상태 평가 결과를 퍼지 집합 이론(fuzzy set theory)으로 분석한 결과와 비교하여 방법의 정당성 및 신뢰성을 논의한다.

• Journal of the Korea Safety Management & Science
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• v.1 no.1
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• pp.7-17
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• 1999

As the loss from break-downs and errors, which became more frequent with the growth of elaborateness, complexity and in scale of the plant and equipments, are enormous, the improvement in the reliability, maintenance, safety, and qualify become to have interest. The fault diagnosis is a systematic and unified method to find errors, which is based on the interpretation that data, subconsciously, have noises. But, as most of the methods are inferences based on binomial logic, the uncertainty is not correctly reflected. In this study, we suggest, to manage the uncertainty in the system efficiently on the point of predictive maintenance, We should use fuzzy expert system, which make the decision considering uncertainty possible by taking linguistical variable and fixed quantity by using the fuzzy theory concepts on the basis of an expert's direct observation and experience.

• Journal of Aerospace System Engineering
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• v.8 no.4
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• pp.7-17
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• 2014

Objective of this paper is to introduce a new technology known as prognostics and health management (PHM) which enables a real-time life prediction for safety critical systems under extreme loading conditions. In the PHM, Bayesian framework is employed to account for uncertainties and probabilities arising in the overall process including condition monitoring, fault severity estimation and failure predictions. Three applications - aircraft fuselage crack, gearbox spall and battery capacity degradation are taken to illustrate the approach, in which the life is predicted and validated by end-of-life results. The PHM technology may allow new maintenance strategy that achieves higher degree of safety while reducing the cost in effective manner.

• Journal of the Korea institute for structural maintenance and inspection
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• v.5 no.4
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• pp.177-184
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• 2001

In this study, three most distinct types of general rigid connections are included in the modelling, with is implemented into a computer code. The cost, functions of connections are constructed by using the estimated unit cost of bolting, welding and connection-steel elements incorporating all the effect of materials, labor, and fabrication work. Bused on the recent developments of the reliability-based structural analysis and design as well as the extending knowledge on the probabilistic characteristics of load and resistances, the probability based design criteria have been successfully developed for many standards. Since the probabilistic characteristics depend highly on the local load and resistances, it is recognized to develop the design criterion compatible with domestic requirements. The existing optimum design methods, which are generally based on the structural theory and certain engineering experience, do not realistically consider the uncertainties of load and resistances and the basic reliability concepts.

• Journal of the Korea institute for structural maintenance and inspection
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• v.2 no.4
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• pp.217-223
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• 1998

본 논문에서는 원형연단이 단순지지 되어 있을 때 단순과 자유의 방사연단 조건을 갖는 부채꼴형 평판의 휨진동에 대한 엄밀한 해석방법을 제시한다. Ritz방법을 이용하여 수직진동변위를 두가지 적합 함수식으로 가정하였다. 이러한 두가지의 적합 함수식은 (1) 수학적으로 완전한 대수삼각다항함수와, (2) 둔각 모서리에서의 휨모멘트 특이도를 고려하는 모서리함수로 구성되어있다. 본 연구에서는 방사연단의 둔각 모서리를 이루는 부채꼴형 각도의 범위에 따른 엄밀한 진동수 및 수직진동 변위의 전형적인 등고선을 제시하였다.

• Journal of the Korea institute for structural maintenance and inspection
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• v.3 no.2
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• pp.213-220
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• 1999

The purpose of this study is to apply cathodic protection to reinforced concrete structure and provide fundamental data to prevent the corrosion. The theory of cathodic protection of steel in concrete is to apply sufficient direct current so that corroding anodes on the steel are prevented from discharging ions. Two methods are used to supply the external current. In one, the protected metal is the cathode by connecting it to a more active metal. In the second, an external direct current power source supplies the current. The first is the sacrificial-anode system and the second the impressed-current system. The study results showed that the corrosion of the reinforcing steel in concrete could be enormously decreased by using protective current. The sacrificial anode and concrete nave to be adhered closely each in order to prevent the corrosion of reinforcing steel.

• International conference on construction engineering and project management
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• 2015.10a
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• pp.357-360
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• 2015

For the last 40 years, the Korean government has built and supplied diverse public facilities. The Korean government, which has supplied diverse public facilities for the last 40 years, has maintained these public facilities as breakdown maintenance under limited budget. Because of increase of aging of public facilities and insufficient budget, it needs the total public facility maintenance. Especially, as Japan has also experienced similar issues and solved these, they are the introduction of P-FM theory and see successful examples. In this study, by comparison Analysis on the Merits and Demerits for Public Facility management (P-FM) between domestic and abroad, it would find a future direction to public facility management P-FM is to go.

• Journal of the HCI Society of Korea
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• v.13 no.3
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• pp.5-15
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• 2018

The biggest characteristic of Social Network Game(SNG) is that games are played through competition and cooperation with the actual acquaintances based on SNS. Even though such competition and challenge spirit have been dealt importantly as preceding factors having influence on the flow in games in the existing game area, it is rare to find researches deeply considering the characteristics of ranking competition between acquaintances in SNG. Moreover, it was not considered that such acquaintances could be the targets of competition and also challenge at the same time in SNG. Therefore, this study examined the achievements(big differences in ranking, small differences in ranking) of the targets for comparison and closeness(strong ties, weak ties) with the targets for comparison as factors having influence on competition and challenge spirit, and also empirically analyzed the influence of such factors and interactions between factors on players' competition and challenge spirit in the ranking competitive society, by analyzing the characteristics of ranking competition between acquaintances in the mobile puzzle, SNG based on SNS through the analysis on the preceding research on the self-evaluation maintenance model of the social comparison theory. In the results, when preferentially exposing competitors with small difference in ranking and also exposing competitors with stronger ties, players' competition is stimulated, so that it can improve their challenge spirit. Such results of this study can be expected to a lot contribute to the actual design work of SNG ranking table contents.

• International Journal of Highway Engineering
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• v.12 no.3
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• pp.37-47
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• 2010

This research is aimed at comprehensively evaluating the condition of a road surface of a highway in satisfaction of its users. This research conducted an overall evaluation of a road surface condition by adding qualitative data, or a driver's satisfaction to the existing quantitative elements, whereas the existing research put its focus on a correlation analysis with quantitative factors and qualitative factors through a statistical method. As for an evaluation method, this research conducted an overall evaluation by using Grey System Theory which makes possible an integrated evaluation. The analyzed results make it possible to diagnose the current conditions of each section of object roads and to predict the potentially changeable conditions for the time to come. In addition, these analyzed results could hopefully be applied to the maintenance of freeways through diverse methods. It is hoped that the evaluation of a road surface condition of a highway in satisfaction of its user could be helpful to keeping up the satisfaction of a driver and passenger on the highway by more than a certain level. In addition, the analyzed data on the influence of data value observed by comprehensively evaluating a variety of elements could be used as a secondary means of the decision-making process in relation to road maintenance. On top of that, it could be used as a means of improving road maintenance system and offering the improved driving environment of the highway.

• Structural Monitoring and Maintenance
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• v.7 no.2
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• pp.69-84
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• 2020

Based on differential quadrature method (DQM) and nonlocal strain gradient theory (NSGT), forced vibrations of a porous functionally graded (FG) scale-dependent beam in thermal environments have been investigated in this study. The nanobeam is assumed to be in contact with a moving point load. NSGT contains nonlocal stress field impacts together with the microstructure-dependent strains gradient impacts. The nano-size beam is constructed by functionally graded materials (FGMs) containing even and un-even pore dispersions within the material texture. The gradual material characteristics based upon pore effects have been characterized using refined power-law functions. Dynamical deflections of the nano-size beam have been calculated using DQM and Laplace transform technique. The prominence of temperature rise, nonlocal factor, strain gradient factor, travelling load speed, pore factor/distribution and elastic substrate on forced vibrational behaviors of nano-size beams have been explored.