• Proceedings of the Korea Concrete Institute Conference
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• 1995.04a
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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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• v.19 no.6
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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.

• Structural Monitoring and Maintenance
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• v.2 no.1
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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.

• Journal of Conservation Science
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• v.35 no.1
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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.

• The Journal of the Petrological Society of Korea
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• v.27 no.4
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• pp.207-222
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• 2018

Celestial Chart Stones (original and reproduction) in the National Palace Museum are representative scientific cultural heritage of Korea. Material analysis and nondestructive deterioration assessment were conducted for long-term preservation of these stones. Material analysis revealed that the original was composed of slate and the reproduction was made of dolostone. The original consists of quartz, mica, dolomite minerals, while the reproduction was made up of dolomite, calcite and forsterite. Major deterioration factors of the original stone were cracks and breakouts. In case of the reproduction, scratches and artificial materials were mainly observed. The green and black surface contaminants present at the sides and back of the two celestial chart stones were interpreted as resin-based paint materials. The physical property evaluation using ultrasonic velocity showed a low velocity in the upper left side of the original, while the front right side of the reproduction showed a weak property. Meanwhile, the To-Tc method using ultrasonic velocity was applied to major cracks that impede stability of the original. As a result, it has been calculated that the beginning and the center of the crack are the deepest.

• Smart Structures and Systems
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• v.5 no.2
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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.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.48 no.11
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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.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2007.05a
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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.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.10a
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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.

• Journal of Korean Clinical Nursing Research
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• v.19 no.1
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• pp.57-68
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• 2013

Purpose: In assessing patients' neurological status following a stroke it is very important to have a valid tool for early detection of neurological deterioration. NIHSS is considered the best tool to reflect neurological status in patients with ischemic stroke. An education program on use of NIHSS was planned for nurses caring for these patients and the effects of the program were evaluated. Methods: The NIHSS education program (NEP) which includes online and video lectures, and practical education was provided to the nurses from April to July, 2010. To examine the effect of NEP, nursing records of patients with ischemic stroke who were admitted to a stroke center were analyzed. Two groups, a historical control group (n=100) and the study group (n=115) were included. Results: Nursing records for neurologic symptoms for each patient increased (41.0% versus 100.0%, p<.001), and especially, visual disturbance, facial palsy. limb paralysis and ataxia, language disturbance, dysarthria, and neglect symptoms significantly increased (all p<.001). Nurse notification to the doctor of patients with neurological changes increased (21.0% versus 39.1%, p=.004), and nurses' neurological deterioration detection rates also increased (37.5% versus 84.6%, p=.009). Conclusion: NEP improved the quality of nursing records for neurological assessment and the detection rate of neurological deterioration.