• Journal of the Korean Wood Science and Technology
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• 제32권3호
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• pp.33-41
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• 2004

In ancient wooden structures, the mechanical properties of the structural members have been reduced by time-dependent degradations such as fatigue or creep. Also, the external and internal deterioration was caused by environmental condition, fungi, bacteria, or insect, and then reduced the quality of structural members. However, the previous methods for evaluating the deterioration have been mainly depended on the visual inspection. In this study, therefore, ultrasonic stress wave test, accelerometer stress wave test were used to evaluate the deterioration of structural wood members in ancient wooden structures. Based on the results, the quantitative criteria of stress wave transmitted velocity were proposed to evaluate the deterioration of structural member. The proposed criteria were related to the degree of deterioration. In accelerometer stress wave, the criteria of deterioration of wave reciprocal velocity was below 1800 ㎲/m at incipient deterioration (below 12% ratio of deterioration), between 1800 and 2200 ㎲/m at moderate deterioration (12~17%) and above 2200 ㎲/m at severe deterioration (above 17%). The ultrasonic stress wave, the criteria of deterioration were 800 and 950 ㎲/m at below 8% and above 15% of the degree of deterioration respectively.

• 전기학회논문지
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• 제62권6호
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• pp.881-885
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• 2013

In this paper, we present a deterioration judgment model of urban rail power equipment using driving history, the frequency and number of failures. In addition, we have developed a deterioration judgment program based on the derived failure rate. A deterioration judgment model of power equipments on metro system was designed to establish how much environmental factors, such as thermal cycling, humidity, overvoltage and partial discharge. The deterioration rate of the transformers followed the Arrhenius log life versus reciprocal Kelvin temperature (hotspot temperature) relation. The deterioration judgment program is linked to the online condition monitoring system of urban railway system. The deterioration judgment program is based on the user interface it is possible to apply immediately to the urban rail power equipment.

• Structural Monitoring and Maintenance
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• 제1권4호
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• pp.357-369
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• 2014

In the existing bridge management systems, assessment of the structural behavior is based on the results of visual inspections in which corresponding condition states are assigned to individual elements. In this process, limited attention is given to the correlation between bridge elements from structural perspective. Also, the uncertainty of parameters which affect the structural capacity is ignored. A system reliability-based assessment model is potentially an appropriate replacement for the existing procedures. The aim of this research is to evaluate the system reliability of existing conventional Steel-Reinforced bridge decks over time. The developed method utilizes the reliability theory and evaluates the structural safety for such bridges based on their failure mechanisms. System reliability analysis has been applied to simply-supported concrete bridge superstructures designed according to the Canadian Highway Bridge Design Code (CHBDC-S6) and the deterioration pattern is achieved based on the reliability estimates. Finally, the bridge condition index of an old existing bridge in Montreal has been estimated using the developed deterioration pattern. The results obtained from the developed reliability-based deterioration model and from the evaluation done by bridge engineers have been found to be in accordance.

• 한국환경생태학회지
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• 제16권4호
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• pp.465-474
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• 2003

최근 우리나라 주요한 생태공간인 백두대간을 이용하는 인구가 급증하면서 백두대간 마루금 등산로에서 주변 파연환경의 훼손이 심화되고 있다. 이 연구는 백두대간 마루금 등산로에 대한 보전적 측면에서의 관리전략을 마련하기 위하여 지리산 만복대에서 복성이재까지를 대상으로 등산로의 훼손실태를 파악하고자 시도되었다. 지형조건을 고려하여 7개 구간으로 구분된 총 28.4km, 232개 측점에서 등산로 상태를 조사한 바 평균노폭 106cm, 평균나지폭 65cm, 평균침식깊이 8cm, 평균물매 20%로 나타났다. 훼손유형별 발생빈도는 뿌리 노출(23%). 암석노출(14%). 노폭확대(7%) 둥의 순이었으나 건전한 지점의 출현빈도는 64%로 대단히 높았다. 훼손발생지점의 등산로 상태는 건전한 지점과 상당한 차이를 보였다. 등산로 주변으로 확산되는 훼손의 진행단계와 범위를 파악하기 위한 환경피해도는 3등급이 2.9m, 4등급 0.8m, 5등급 0.4m, 6등급 0.1m로 환경피해도 등급이 높을수록 훼손폭이 좁았으며, 4등급 이상의 폭은 1.2m이었다 종합적으로 볼 때 이 지역의 마루금 등산로의 훼손상태는 우려할만한 수준은 아니나 입지조건이나 이용압력의 증가 추세를 감안할 때 현상태에서 유지되도록 관리방안을 조속히 마련할 필요가 있다.

• 한국도로학회논문집
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• 제8권2호
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• pp.49-54
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• 2006

The purpose of this study was to determine the effect of expansion joint spacing (slab size) on the life cycle costs of owning Portland Cement Concrete (PCC) airfield pavements. Previous research has shown that slab size has a statistically significant impact on pavement performance. A probabilistic life cycle cost analysis was performed to determine if the effect of slab size on pavement performance would affect the total cost of ownership of PCC pavements. Data from 48 Pavement Condition Index (PCI) inspections of military and civilian airfields were used to develop probability-of-distress-by-condition curves, which were then used to develop probabilistic cost-of-repair-by-condition curves. A present worth life cycle cost analysis was then performed for various slab sizes, using construction costs, rehabilitation costs, and maintenance costs. Maintenance costs were determined by assuming a condition deterioration rate appropriate for each slab size and applying the cost-by-condition curves. The probabilistic cost-of-repair-by-condition curves indicated that smaller slabs are more expensive to repair on a unit cost basis. Life cycle cost analysis showed that larger slabs have a higher total cost of ownership than smaller slabs due to a faster rate of deterioration.

• Journal of Electrical Engineering and Technology
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• 제6권3호
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• pp.384-390
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• 2011

To evaluate the condition of stator winding insulation in generators that have been operated for a long period of time, diagnostic tests were performed on the stator bars of a 500 MW, 22 kV generator under accelerated thermal and electrical aging procedures. The tests included measurements of AC current (${\Delta}I$), dissipation factor ($tan{\delta}$), partial discharge (PD) magnitude, and capacitance (C). In addition, the AC current test was performed on the stator winding of a 350 MW, 24 kV generator under operation to confirm insulation deterioration. The values of ${\Delta}I$, ${\Delta}tan{\delta}$, and PD magnitude in one stator bar indicated serious insulation deterioration. In another stator bar, the ${\Delta}I$ measurements showed that the insulation was in good condition, whereas the values of ${\Delta}tan{\delta}$ and PD magnitude indicated an incipient stage of insulation deterioration. Measurements of ${\Delta}I$ and PD magnitude in all three phases (A, B, C) of the remaining generator stator windings showed that they were in good condition, although the ${\Delta}tan{\delta}$ measurements suggested that the condition of the insulation should be monitored carefully. Overall analysis of the results suggested that the generator stator windings were in good condition. The patterns of PD magnitude in all three phases (A, B, C) were attributed to internal discharge.

• 한국구조물진단유지관리공학회 논문집
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• 제5권1호
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• pp.131-140
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• 2001

In general, the deterioration induced by the freezing and thawing cyclic in concrete structures often leads to the reduction in concrete durability by the cracking or surface spalling. If it can prediction of concrete deterioration subjected to cyclic freezing and thawing, we can rationally do the design of mix proportion in view of concrete durability and the maintenance management of concrete structures. Therefore in this study a prediction method of deterioration for concrete structures subjected to the irregular freezing and thawing is proposed from the results of accelerated laboratory freezing and thawing test using the constant temperature condition and the in-situ weathering data. Furthermore, to accurately predict the concrete deterioration, a method of modification for the effect of hydration increasing during rapid freezing and thawing test is investigated.

• 한국구조물진단유지관리공학회 논문집
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• 제4권4호
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• pp.101-107
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• 2000

In this study, the Ground Penetrating Radar(GPR) was tested to evaluate the condition of concrete decks. Test results obtained by CPR were compared with values measured from drilled cores and damage mapping by the visual survey. It is shown that GPR can provide highly accurate measurements of layer properties of concrete decks and can map areas of deterioration in bridge decks by dielectric constants. The deck condition can be grouped into categories of "good" or "distressed". The ground penetrating radar data shows promise for producing rapid and accurate condition assessment for bridge decks. And these data can be used to evaluate highway bridge condition and make cost-effective bridge deck rehabilitation by accurately estimating the quantity of deteriorated concrete.

• 상하수도학회지
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• 제26권5호
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• pp.669-683
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• 2012

The water supply pipes are buried across wide range of areas, so it is hard to spot them using excavation and takes a large amount of expense. Thus, there is a high risk for direct research and application, accompanying many difficulties in implementation of them. Therefore, it is more economical and convenient to use indirect evaluation variables than direct evaluation of the buried pipes in assessing the degree of pipe deterioration. To assess the degree of pipe deterioration using the indirect evaluation variables, it should be done first to identify how and to what extent they affect the degree of deterioration. This study measured the evaluation variables for pipe deterioration using the pipe endoscope and analyzed the measurement results and the degree of impact on the pipes. In addition, this study attempted to evaluate the adequateness of the pipe deterioration evaluation using the indirect variables based on the analysis results. The evaluation variables measured through the pipe endoscope were the thickness of sediments, size of scale, degree of desquamation and condition of connections. For the indirect evaluation variables, the data such as the property data from GIS pipe network map as well as the material, diameter, age and pipe lining material of the pipe, road type, leakage frequency, average water velocity and water pressure using the leakage repair records was collected. Using the collected data, this study comparatively analyzed the indirect evaluation variables for the degree of pipe deterioration and the results from the pipe endoscope to choose appropriate variables for pipe deterioration evaluation and calculated the weights of the indirect variables on the degree of deterioration. The results showed that the order of the impact of indirect variables on deterioration was pipe age > pipe lining material > road type > leakage frequency > average water velocity with their weights of 0.45, 0.20, 0.15, 0.10, and 0.10, respectively. Conclusively, the results suggest that the measures of sediment thickness, scale size, degree of desquamation and condition of connections are appropriate for the evaluation of pipe deterioration and sufficient for the analysis of the impact of the indirect variables on deterioration.

• 한국환경생태학회지
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• 제18권2호
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• pp.175-183
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• 2004

최근 산행인구의 급증과 함께 주변 자연환경의 훼손이 심화되고 있는 백두대간 마루금 등산로에 대한 보전적 측면에서의 관리전략을 마련할 필요성이 제기되고 있다. 이 연구는 지리산 만복대에서 복성이재까지를 대상으로 한 연구(권태호와 이준우, 2003)의 후속 연구로서 남덕유산에서 소사고개까지의 마루금 등산로의 훼손실태를 파악하고자 시도되었다. 지형조건을 고려하여 7개구간으로 구분된 총 32.3km, 182개 측점에서 등산로 상태를 조사한 바 평균노폭 100cm, 평균나지폭 67cm, 평균침식깊이 13cm, 평균물매 23%로 나타났다. 훼손유형별 발생빈도는 암석노출(48%), 뿌리노출(41%), 종침식(19%)등의 순이었고, 건전한 지점의 출현빈도는 33%로 그리 높지 않았다. 또한 훼손발생지점의 등산로 상태는 건전한 지점과 상당한 차이를 보였다. 등산로 주변으로 확산되는 훼손의 진행단계와 범위를 파악하기 위한 환경피해도는 3등급이 2.1m, 4등급 0.4m, 5등급 0.4m, 6등급 0.1m로 환경피해도 등급이 높을수록 훼손폭이 좁았다. 4등급 이상의 폭은 0.9m이었고, 삼봉산∼소사고개 구간이 가장 넓었다. 이 지역의 마루금 등산로의 훼손상태는 우려 할 만한 수준은 아니나 일부 지점들은 종합적이고 체계적인 정비 복구가 필요하였으며, 이와 관련한 관리 방향을 제안하였다.