• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1995년도 봄 학술발표회 논문집
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• pp.286-291
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• 1995

The deterioration of PC box girder may cause serious effect on the durability of PC structure compared to that of RC structures. In the durability assessment of PC box girder bridges, a quantitive model on crack width is considered as a measure of durability. This study suggests a durability limit state model for PC box girder bridges. This durability limit state model in formulated based on the conventional models on the cracks in concrete. And the allowable crack width is taken as an assumed value established by the design specification or provided by the maintenance authority of the structure.

• Geomechanics and Engineering
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• 제19권6호
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• pp.499-511
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• 2019

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.

• 보존과학회지
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• 제35권1호
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• pp.19-31
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• 2019

To study the cleaning effects and post-treatment stability assessment of various methods of cleaning textiles with metal thread, six naturally-soiled historical textiles with metal thread were investigated at the Metropolitan Museum of Art, New York. Prior to the cleaning of fabricated gold, silver, and copper thread that had been glued onto a paper substrate, the artificial deterioration was carried out in a controlled environment with light(UV and daylight), and temperature and humidity factors which would weaken and damage the samples. A synthetic soil mixture was applied to the samples to imitate soil found on the historic and archaeological textiles with metal thread; the cleaning effect and post-treatment assessment were investigated by use of three textile cleaning methods: mechanical cleaning, wet cleaning, and solvent cleaning. While investigating the naturally-soiled textiles with metal thread, it was determined that the soil colors and sizes of contaminating particles of each textile were different due to the diversity of original environmental factors and conditions. After cleaning with kneaded rubber, Stoddard solvent, n-decane or n-hexane, a bright, clean effect was apparent. Kneaded rubber was successful in picking up both large and small particles, but its stickiness caused some of the metal leaf to peel off. Stoddard solvent produced a good cleaning effect, but after use of n-hexane and n-decane in the cleaning process, a white layer of residue remained on the textile's surface. Wet cleaning was not effective and the rapid humidity changes between wet and dry conditions caused the edges of the paper substrate to lose their original shape.

• Structural Monitoring and Maintenance
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• 제2권1호
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• pp.19-34
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• 2015

One of the main causes of a limited use of nondestructive evaluation (NDE) technologies in bridge deck assessment is the speed of data collection and analysis. The paper describes development and implementation of the RABIT (Robotics Assisted Bridge Inspection Tool) for data collection using multiple NDE technologies. The system is designed to characterize three most common deterioration types in concrete bridge decks: rebar corrosion, delamination, and concrete degradation. It implements four NDE technologies: electrical resistivity (ER), impact echo (IE), ground-penetrating radar (GPR), and ultrasonic surface waves (USW) method. The technologies are used in a complementary way to enhance the interpretation. In addition, the system utilizes advanced vision to complement traditional visual inspection. Finally, the RABIT collects data at a significantly higher speed than it is done using traditional NDE equipment. The robotic system is complemented by an advanced data interpretation. The associated platform for the enhanced interpretation of condition assessment in concrete bridge decks utilizes data integration, fusion, and deterioration and defect visualization. This paper concentrates on the validation and field implementation of two NDE technologies. The first one is IE used in the delamination detection and characterization, while the second one is the USW method used in the assessment of concrete quality. The validation of performance of the two methods was conducted on a 9 m long and 3.6 m wide fabricated bridge structure with numerous artificial defects embedded in the deck.

• 암석학회지
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• 제27권4호
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• pp.207-222
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• 2018

국립고궁박물관 소장 천상열차분야지도 각석 및 복각천상열차분야지도 각석은 우리나라의 전통 천문학 수준을 실증하는 대표적인 과학문화유산이다. 태조본 각석은 암갈색 점판암, 숙종본 각석은 회백색 백운암으로 서로 다른 암석으로 제작되었다. 태조본 점판암은 석영, 백운모, 백운석의 광물조성을 보였으며, 숙종본 백운암은 백운석, 고토감람석, 방해석으로 구성되어 있다. 태조본 각석은 숙종본에 비해 손상이 심화되어 있으며 주요한 손상인자는 균열 및 탈락이다. 숙종본에서는 긁힘과 인위적인 오염물이 관찰되었다. 태조본 및 숙종본 각석 측면과 후면에 나타나는 녹색 및 흑색 표면오염물은 수지 기반의 페인트 물질로 해석된다. 한편, 초음파 물성평가에서 태조본 각석은 좌측면 상부가, 숙종본 각석은 전면 우측부가 저속도대를 보인다. 태조본각석의 안정성을 저해하는 주요 균열에 대해 To-Tc법으로 발달 상태를 조사한 결과, 균열의 전개부 및 중심부에서 가장 깊은 심도가 측정되었다.

• Smart Structures and Systems
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• 제5권2호
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• pp.173-191
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• 2009

Civil infrastructures are always subjected to various types of hazard and deterioration. These conditions require systematic efforts to assess the exposure and vulnerability of infrastructure, as well as producing strategic countermeasures to reduce the risks. This paper describes the needs for and concept of advanced sensor technologies for risk assessment of civil infrastructure in Japan. Backgrounds of the infrastructure problems such as natural disasters, difficult environment, limited resource for maintenance, and increasing requirement for safety are discussed. The paper presents a concept of risk assessment, which is defined as a combination of hazard and structural vulnerability assessment. An overview of current practices and research activities toward implementing the concept is presented. This includes implementation of structural health monitoring (SHM) systems for environment and natural disaster prevention, improvement of stock management, and prevention of structural failure.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제48권11호
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• pp.735-741
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• 1999

The monitoring and assessment on the insulation condition of generator stator windings have been an important task of utility companies. The interest for the assessment of insulation condition has been increasing due to the need to keep old generating equipment reliable in order to extend the equipment life and to increase the generating capacity. Even though many developments and research activities for the condition assessment of generator insulation have been performed for decades, the assessment criterion in order to consistently predict the actual insulation condition is still in question. In this paper, the correlation between the parameters and the insulation condition is analyzed through the various non-destructive diagnostic tests in order to establish the assessment criterion on insulation deterioration of generator stator windings. By analyzing the correlation, PDI(Partial Discharge Index) as a novel parameter for the assessment criterion on insulation diagnosis of stator winding is proposed and verified.

• 한국조명전기설비학회:학술대회논문집
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• 한국조명전기설비학회 2007년도 춘계학술대회 논문집
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• pp.458-462
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• 2007

It is necessary to study a conductive characteristics of electrical facilities covered with particulate for the analysis of electrical accidents in vulnerable area where are included market place, a sawmill and so on. Therefore, there are studied on risk assessment and contact angle measure(CAM) according to surface deterioration of PVC and phenolic resin Through the contact angle measure of samples, there are ascertain whether hydrophobicity or not. These data would used to be judged by the causes of electrical accidents.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2008년도 추계 학술발표회
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• pp.1549-1554
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• 2008

In this paper, The evaluation of durability of the PC Panel lining for tunnel structure was examined through the rapid test by carbonation and freezing and thawing. Also for the purpose of improvement of durability. Namely, the durable characteristics of PC Panel lining by carbonation and freezing and thawing, was evaluated by rapid test and long-term field exposure test and main influence factors were derived. As a result of test, Correlation of accelerating test in deterioration chamber and long-term field exposure test, it will be expected that the proposed correlation well to the prediction of life expectancy of structure and is contributed greatly in the future.

• Archives of Plastic Surgery
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• 제39권3호
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• pp.198-202
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• 2012

Background : Maxillary hypoplasia refers to a deficiency in the growth of the maxilla commonly seen in patients with a repaired cleft palate. Those who develop maxillary hypoplasia can be offered a repositioning of the maxilla to a functional and esthetic position. Velopharyngeal dysfunction is one of the important problems affecting speech after maxillary advancement surgery. The aim of this study was to investigate the impact of maxillary advancement on repaired cleft palate patients without preoperative deterioration in speech compared with non-cleft palate patients. Methods : Eighteen patients underwent Le Fort I osteotomy between 2005 and 2011. One patient was excluded due to preoperative deterioration in speech. Eight repaired cleft palate patients belonged to group A, and 9 non-cleft palate patients belonged to group B. Speech assessments were performed preoperatively and postoperatively by using a speech screening protocol that consisted of a list of single words designed by Ok-Ran Jung. Wilcoxon signed rank test was used to determine if there were significant differences between the preoperative and postoperative outcomes in each group A and B. And Mann-Whitney U test was used to determine if there were significant differences in the change of score between groups A and B. Results : No patients had any noticeable change in speech production on perceptual assessment after maxillary advancement in our study. Furthermore, there were no significant differences between groups A and B. Conclusions : Repaired cleft palate patients without preoperative velopharyngeal dysfunction would not have greater risk of deterioration of velopharyngeal function after maxillary advancement compared to non-cleft palate patients.