• 한국주거학회:학술대회논문집
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• 한국주거학회 2008년도 춘계학술발표대회 논문집
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• pp.225-230
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• 2008

High-rise and high-density apartment complexes has been built and supplied on a large scale in the metropolis and metropolitan areas since 1980s in order to solve housing shortage in cities. Recently they are raising deterioration problems for aging more than 20 years. moreover, those problems show very special characters such as simultaneity and a large scale. The purpose of this study is to propose a direction for the development of the evaluating indicators to measure the level of deterioration of apartments. The level of deterioration of apartments can be evaluated by housing performance. In order to evaluate the deterioration comprehensively, the housing performance indicators should be developed on the social, economical, and physical dimension. This study analyzed the concept of the apartment deterioration and compared housing performance indicators through literature review. First of all, when considering various factors in the evaluation of the deteriorated apartments, such as evaluating ranges, attributes and dimensions, housing performance indicators should be structured with the hierarchical framework. Second, housing performance indicators evaluating the level of deterioration of apartments should include social, psychological, and cultural aspects of home environments in order to understand adequately the attitude of the middle class toward services that apartments provide. Third, in previous researches, most criteria have been developed and weighted based on only expert opinions regarding performance indicators. So, It is necessary to include residents' opinions in developing performance indicators since they can provide more practical and feasible aspects the experts could not experience or understand.

• Computers and Concrete
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• 제20권5호
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• pp.511-519
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• 2017

The reliability of reinforced concrete structures is frequently compromised by the deterioration caused by reinforcement corrosion. Evaluating the effect caused by reinforcement corrosion on structural behaviour of corrosion damaged concrete structures is essential for effective and reliable infrastructure management. In lifecycle management of corrosion affected reinforced concrete structures, it is difficult to correctly assess the lifecycle performance due to the uncertainties associated with structural resistance deterioration. This paper presents a stochastic deterioration modelling approach to evaluate the performance deterioration of corroded concrete structures during their service life. The flexural strength deterioration is analytically predicted on the basis of bond strength evolution caused by reinforcement corrosion, which is examined by the experimental and field data available. An assessment criterion is defined to evaluate the flexural strength deterioration for the time-dependent reliability analysis. The results from the worked examples show that the proposed approach is capable of evaluating the structural reliability of corrosion damaged concrete structures.

• Structural Engineering and Mechanics
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• 제54권2호
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• pp.319-336
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• 2015

Life cycle performance of corrosion affected RC structures is an important and challenging issue for effective infrastructure management. The accurate condition assessment of corroded RC structures mainly depends on the effective evaluation of deterioration occurring in the structures. Structural performance deterioration caused by reinforcement corrosion is a complex phenomenon which is generally uncertain and non-decreasing. Therefore, a stochastic modelling such as the gamma process can be an effective tool to consider the temporal uncertainty associated with performance deterioration. This paper presents a time-dependent reliability analysis of corrosion affected RC structures associated bond strength degradation. Initially, an analytical model to evaluate cracking in the concrete cover and the associated loss of bond between the corroded steel and the surrounding cracked concrete is developed. The analytical results of cover surface cracking and bond strength deterioration are examined by experimental data available. Then the verified analytical results are used for the stochastic deterioration modelling, presented here as gamma process. The application of the proposed approach is illustrated with a numerical example. The results from the illustrative example show that the proposed approach is capable of assessing performance of the bond strength of concrete structures affected by reinforcement corrosion during their lifecycle.

• 한국지진공학회논문집
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• 제28권4호
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• pp.223-231
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• 2024

For the OPR1000, a standard power plant in Korea, an analytical model of the containment building considering voids and deterioration was built with multilayer shell elements. Voids were placed in the vulnerable parts of the analysis model, and the deterioration effects of concrete and rebar were reflected in the material model. To check the impact of voids and deterioration on the seismic performance of the containment building, iterative push-over analysis was performed on four cases of the analytical model with and without voids and deterioration. It was found that the effect of voids with a volume ratio of 0.6% on the seismic performance of the containment building was insignificant. The effect of strength reduction and cross-sectional area loss of reinforcement due to deterioration and the impact of strength increase of concrete due to long-term hardening offset each other, resulting in a slight increase in the lateral resistance of the containment building. To determine the limit state that adequately represents the seismic performance of the containment building considering voids and deterioration, the Ogaki shear strength equation, ASCE 43-05 low shear wall allowable lateral displacement ratio, and JEAC 4601 shear strain limit were compared and examined with the analytically derived failure point (ultimate point) in this study.

• Structural Engineering and Mechanics
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• 제75권4호
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• pp.455-464
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• 2020

Reinforcement corrosion is one of the major problems in the durability of reinforced concrete structures exposed to aggressive environments. Deterioration caused by reinforcement corrosion reduces the durability and the safety margin of concrete structures, causing excessive costs in managing these structures safely. This paper aims to investigate the effects of reinforcement corrosion on the load bearing capacity deterioration of the corroded reinforced concrete structures. A new analytical method is proposed to predict the crack growth of cover concrete and evaluate the residual strength of concrete structures with corroded reinforcement failing in bond. The structural performance indicators, such as concrete crack growth and flexural strength deterioration rate, are assumed to be a stochastic process for lifetime distribution modelling of structural performance deterioration over time during the life cycle. The Weibull life evolution model is employed for analysing lifetime reliability and estimating remaining useful life of the corroded concrete structures. The results for the worked example show that the proposed approach can provide a reliable method for lifetime performance assessment of the corroded reinforced concrete structures.

• 한국항공우주학회지
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• 제35권3호
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• pp.238-247
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• 2007

유전자 알고리즘은 자연선택과 유전법칙을 적용하여 최적해를 탐색하는 방법으로, 본 연구에서 항공기용 가스터빈 엔진의 결함 진단을 위한 학습 알고리즘으로 사용되었다. 성능 저하를 고려한 구성요소는 압축기, 가스발생기 터빈, 동력 터빈이며, 설계점에서 엔진의 단일 구성요소에 대하여 각각 성능 저하 예측을 수행한 후, 이를 바탕으로 결함 진단을 수행하였다. 학습데이터 수의 증가가 유전자 알고리즘을 이용한 성능 저하 예측 및 결함 진단에 미치는 영향을 분석하였으며, 결과적으로 결함치에 대한 RMS 오차율이 모두 3% 이내로 예측됨을 확인하였다.

• 한국산학기술학회논문지
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• 제14권7호
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• pp.3482-3486
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• 2013

페이딩 채널에서 야기되는 진폭 및 위상 왜곡을 예측하여 보상하는 PSAM(Pilot Symbol Assisted Modulation)방식의 경우에는 fast 페이딩 채널에서 도플러확산에 의해 심한 성능 저하를 갖는다. 이에 대한 문제점을 분석하고, 이를 개선하기 위한 페이딩 보상 방식을 제안한다. 도플러 확산은 BER 성능을 저하시키는 주된 원인이 된다. 기존의 PSAM 방식과 비교해 보면, 한 심벌 주기 이내의 지연파의 간섭이 있는 환경에서는 기존 PSAM 방식은 도플러확산에 의해 BER이 $10^{-1}$ 정도의 매우 심각한 성능저하를 보이지만 제안된 방식은 도플러 확산이 클수록 성능저하는 발생하지만 기존 방식에 비해 BER이 $10^{-2}$ 이하로 성능이 우수함을 알 수 있다.

• Computers and Concrete
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• 제14권6호
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• pp.727-743
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• 2014

The management of existing concrete bridges has become a major social concern in many developed countries due to the large number of bridges exhibiting signs of significant deterioration. This problem has increased the demand for effective maintenance and renewal planning. In order to implement an appropriate management procedure for a structure, a wide array of corrective strategies must be evaluated with respect to not only the condition state of each defect but also safety, economy and sustainability. This paper describes a new performance evaluation system for existing concrete bridges. The system evaluates performance based on load carrying capability and durability from the results of a visual inspection and specification data, and describes the necessity of maintenance. It categorizes all girders and slabs as either unsafe, severe deterioration, moderate deterioration, mild deterioration, or safe. The technique employs an expert system with an appropriate knowledge base in the evaluation. A characteristic feature of the system is the use of neural networks to evaluate the performance and facilitate refinement of the knowledge base. The neural network proposed in the present study has the capability to prevent an inference process and knowledge base from becoming a black box. It is very important that the system is capable of detailing how the performance is calculated since the road network represents a huge investment. The effectiveness of the neural network and machine learning method is verified by comparing diagnostic results by bridge experts.

• 한국공작기계학회논문집
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• 제16권3호
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• pp.56-63
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• 2007

Modern diesel vehicle has to comply with the EURO IV, V regulation with low level of particulate matter and smoke emission Moreover, emission standards of each countries are becoming stringent in advanced countries such as USA and Europe. Because Bio-diesel is similar to diesel fuel, it is essential to judge the environmental and health effects deriving from the use of Bio-diesel in diesel engine. The deterioration characteristics of emission in accordance with aging vehicles must be regulated for Bio-diesel. Therefore, under 1200 driving hours, 220,000km driving distance condition and full load, the deterioration characteristics of emission were estimated. We could reduce sulfur contents of fuel, particulate matter and smoke emission by using Bio-diesel and conform the influence of engine performance, emission, and fuel consumption by Bio-diesel deterioration

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2005년도 추계 학술발표회 제17권2호
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• pp.563-566
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• 2005

Concrete structures have been damaged by salt, carbonization, freezing and thawing and the others. Therefore, it is needed to protect durability and performance according to the appropriate materials and methods in the concrete structures. In general, several types of polymer and silicate are used as protecting deterioration agents of concrete structures, but these agents have many problems because of low durability and properties. In this study, It developed the deterioration restraining agent using polycondensed silicate and monomer that can block a deterioration cause such as $CO_2$ gas, salt and water from the outside and enhance waterproofing ability by reinforcing the concrete surface when applying it to concrete structures. Also, it developed the systems for improving concrete performance using a deterioration restraining agent.