• Korean Journal of Health Education and Promotion
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• v.24 no.3
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• pp.61-71
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• 2007

Objectives: The research was conducted to evaluate the socio-demographic, life style and work related factors of stress and fatigue, and correlation between them in the white collar workers. Methods: This study was targeted on white collar workers of medium-sized company in Kimhae city including 249 people; 167 of males, 82 of females. The data was collected by structured questionnaires and analyzed using t-test, ANOVA, Pearson correlation and stepwise multiple regression with SPSS 12.0. Result: Both stress and fatigue levels were higher for female of gender, 20s of age, single of marital status in socio-demographic factors. The stress level was higher for current smokers and lower frequency of regular exercise per week, and both stress and fatigue levels were higher for unsatisfied sleeping in lifestyle factors. The stress level was lower for 5-day workweek system and experience of downsizing, and both stress and fatigue levels were higher far lower period of employment in work related factors. The correlation coefficient(r) between stress and fatigue level was 0.578, which was highly statistically significant. According to stepwise multiple regression analysis, factors affecting stress were unsatisfied sleeping, female and lower frequency of regular exercise per week, and those affecting fatigue were younger age and unsatisfied sleeping. Conclusion: This study provided strong support for associations between stress and fatigue, and we suggest that modifiable factors such as regular exercise and satisfied sleeping would be important for white collar workers to reduce their stress and fatigue.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2002.05a
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• pp.104-109
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• 2002

In this paper, a statistical analysis of fatigue crack growth behavior under constant amplitude loads has been carried out. Fatigue crack growth tests were conducted on sixteen pre-cracked compact tension (CT) specimens of the pressure vessel (SPV50) steel in controlled identical load and environmental conditions. The assessment of the statistical distribution of fatigue crack growth experimental data obtained from SPV50 steel was studied and also the correlation of the parameter C and m in the Paris-Erdogan law was discussed. The probability distribution function of fatigue crack growth life seems to follow the 3-parameter Weibull. The fatigue crack growth rate seems to follow the 3-parameter Weibull and the log-normal distribution. The coefficient of variation (COV) of fatigue crack growth life was observed to decrease as the crack grows. A strong negative linear correlation exists between the coefficient C and the exponent m in Paris model. Fatigue crack growth rate data shows a normal distribution for both m and logC.

• Korean Journal of Materials Research
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• v.25 no.10
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• pp.516-522
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• 2015

Aging aircraft structures are inevitably exposed to environment for a long time facing many potential problems, including corrosion and wide spread fatigue damage, which in turn cause the degradation of flight safety. In this study, the environmental surface damages on aging aircraft structures induced during service were quantitatively analyzed. Additionally, S-N fatigue tests were performed with center hole specimens extracted from aging aircraft structures. From the results of quantitative analyses of the surface damages and fatigue tests, it is concluded that corrosion pits initiated during service reduce the fatigue life significantly. Finally, using the fracture mechanics and the EIFS (equivalent initial flaw size) concepts, the remaining fatigue life was predicted based on actual fatigue test results.

• Steel and Composite Structures
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• v.43 no.3
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• pp.363-373
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• 2022

As a key reinforcement connection between a tower and a substructure in offshore wind turbine system, the transition piece is inevitably subjected to cyclic dynamic environmental loads such as wind, current and wave. Therefore, well designed transition piece with high strength and good fatigue resistance is of great significance to the structural safety and reliability of offshore wind power systems. In this study, the structural behavior of the transition piece was studied by an extensive sets of finite element analyses. Three widely used types of transition piece were considered. The characteristics of stress development, fatigue life and weight depending on the type of the transition piece were investigated in the ultimate limit state (ULS) and the fatigue limit state (FLS) of a 5-MW offshore wind turbine to be placed in Korea. An optimal form of the transition piece was proposed based on this parametric study.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.18 no.3
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• pp.216-223
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• 2008

Objectives : To investigate the effect of overtime work on fatigue symptoms among Korean female workers. Methods : A total of 1,875 subjects were analyzed using the structured questionnaire, which was composed of overtime work, fatigue symptom, and background characteristics. Data analysis included multiple regression to test for a relationship of overtime work with fatigue symptom while statistically controlling for demographic and occupational variables. Results : Overtime work was more common in those with shorter work years of 3 or less than in those with longer work years. Overtime work was more popular in day workers than in shift workers. No significant difference of smoking and drinking state was observed between two groups. Subjective fatigue symptoms were significantly higher in overtime workers than in workers without overtime work. In a multiple regression analysis with significant control variables, overtime work was associated with 0.31 more fatigue symptom(p<0.001). Conclusion : Our findings suggest that overtime work may increase risks for fatigue symptom. Therefore, preventive strategies will be needed to control the negative effect of overtime work on health status of female workers.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2001.10a
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• pp.73-78
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• 2001

In this paper, overall planning and design procedure for the marine transportation are examined. For this purpose, marine transportation analysis for the North Nemba deck structure has been carried out. The results of analysis with the rigid barge transportation are compared to those with the barge considering its flexibility. The environmental conditions, especially waves, are shown to be the most important factor which affected on the structural strength, deformation and fatigue damage.

• Journal of Korean Society of Steel Construction
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• v.29 no.1
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• pp.49-60
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• 2017

As well as the strength check, fatigue life check is also mainly required for designing mooring lines of the floating structures. In general, forces which induce dynamic structural response significantly affect to fatigue design of the mooring lines. So, waves are mainly considered as the governing loading for fatigue design of the mooring lines. In this study, characteristics of the fatigue damage of the mooring lines for submerged floating tunnels (SFT) under irregular waves are investigated. For this study time domain hydrodynamic analysis is used to obtain motion of the tunnel and tension and stresses of the mooring lines under the specific environmental conditions. Also, the Rainflow-counting method, the Palmgren-Miner's rule, and S-N curves for floating offshore structures presented by DNV recommendation is applied to calculate the fatigue damage due to the fluctuating stresses. Referring to the design plactice of the tendon pipes for TLP (tension-leg platform), which is very similar structural system to SFT, it is assumed that a 100 year return period wave attacks the SFT systems during 48 hours and the fatigue damages due to the environmental loading are calculated. Following the analysis sequence, the effects of the tunnel draft, spacing and initial inclination angle of the mooring lines on the fatigue damage under the specific environmental loadings are investigated.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.35 no.5
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• pp.1191-1198
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• 2015

In this study, vehicle/track interaction analysis by the Saemaul powered vehicle was carried out. The prediction equation for the bending stress of rail was estimated using the rail bending stress by the rail surface irregularities at welds. Also, the fatigue analysis using a S-N curve of welds in the conventional railway was carried out. We estimated the fatigue life of CWR by the fracture probability. By the rail grinding, the fatigue life of CWR was evaluated in consideration to reduce the rail bending stress through removing the rail surface irregularities. Therefore, it presented the fatigue life of CWR according to the rail grinding execution plan in the conventional railway.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.6 no.2
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• pp.103-109
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• 1986

The distributions of fatigue life of concrete for various applied fatigue stress levels are investigated. The concrete beam specimens are tested in four-point flexural loading conditions. Three different levels of applied fatigue stresses are considered. They are 85%. 75%. 65%, respectively, of the static flexural strength of concrete. The present study indicates that the shapes of the probability distribution of fatigue lives are rather different for different levels of applied fatigue stress. This necessitates the consideration of the effects of applied fatigue stress levels on fatigue life distributions of concrete in order to conduct a realistic fatigue reliability analysis. The graphical method, the method of moments, and the method of maximum likelihood estimation are used to evaluate the distribution parameters of fatigue lives. It was found that the shape parameter of Weibull distribution for the fatigue life of concrete ranges from 2.0 to 4.0 according to the level of applied fatigue stress.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.29 no.3
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• pp.245-252
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• 2016

The development of Top-Mounted In-Core Instrumentation(TM-ICI) is an ongoing project to reduce the risk due to severe accidents by inserting the instrumentation into a reactor closure head instead of a reactor bottom head. As part of this project, environmental fatigue analyses for TM-ICI nozzle have been performed using two methods of NUREG/CR-6909 and Code Case N-761. TM-ICI nozzle is subjected to transient loads for level A, level B and test conditions that should be evaluated for a fatigue analysis. It is found that a cumulative usage factor considering reactor coolant environment for TM-ICI nozzle is evaluated as less than 1, which is ASME Code allowable criteria of a fatigue analysis.