• Journal of the Korea institute for structural maintenance and inspection
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• v.17 no.2
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• pp.33-44
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• 2013

Although many studies have been performed for the structural details of orthotropic steel deck, most of them were focused on the trough rib of standard type, but not for orthotropic steel deck with longitudinal rib of open section used at beginning of the deck. In order to investigate the cause of fatigue crack for orthotropic steel deck bridge serviced 31 years with longitudinal rib of open section, in this study, the behavior characteristics of target structural details were analyzed based on measurement data under real traffic condition. Also the typical loading truck passing the target bridges was estimated with the structural analysis detailed, and the stresses and deformation patterns of target structural details were analyzed by performing the detailed structural analysis. Based upon the analysis, retrofitting methods of the fatigue crack were suggested and its validation was examined. From this study, it was clarified that fatigue crack of longitudinal rib with open section were affected with the stress increment by shear deformation in the rib and the occurrence of alternative stress due to moving vehicle. In addition, it was known that it is important to perform fatigue design reflected the local behavior of the structural details.

• Korean Security Journal
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• no.21
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• pp.121-134
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• 2009

The purpose of present study was to examine the effects of working time on fatigue and immune function in private security. The number of private guard on which this study has been conducted in 153, who work at large companies, medium or small companies and the like as located in Seoul and kyonggi. In this study blood T-lympocyte, Natural T-Killer cell and immunoglobulin(IgG, IgA and IgM) were measured to see the level of working hours. There was significant difference in Natural T-Killer cell and immunoglobulin(IgG, IgA and IgM) and fatigue between working hours(P<0.05). in view of the results of this study, it can be thought that fatigue and immune function is more affected by working hours In summary, these results are interpreted to mean that fatigue levels and immune function (Natural T-Killer cell, and immunoglobulin) decrease due to a rise in working hours.

• Journal of Korean Society of Steel Construction
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• v.18 no.1
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• pp.23-32
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• 2006

This study was conducted to improve the design and construction technique of orthotropic steel-deck bridges. After conducting an F.E.M. analysis of the various rib types of the connection details, static and fatigue tests were conducted, using a three-dimensional, full-scaled, orthotropic, steel-deck-plate model with internal diaphrams, to check the fatigue strength depending on the types of details. The model structure was made of two types of longitudinal ribs: the domestic standard and the European rabbit types. The fatigue strength of the steel-deck system was found to have improved through the installation of an internal diaphram, as no cracks were found on the bottom round part of the scallop with a diaphram. There were no differences between the domestic and the European types of details in terms of strength may be partially influenced by the shape of the scallop and by the installation of an internal diaphram, but it can be improved more significantly according to the quality of the welding that will be done.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.1
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• pp.8-14
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• 2015

Plastics have brought a significant progress in reducing the weight of automotive parts and improving gas emissions by replacing steel parts. The front end module (FEM) carrier, which was made from long glass fiber reinforced polypropylene (PP-LFT), is one of the most successful examples. On the other hand, more research on the fatigue behavior and vibration durability of automotive plastic parts will be needed to improve the long-term reliability. This paper analyzed the durability of the PP-LFT, which is fundamental to fatigue design and analysis of FEM carrier. Various fatigue tests were conducted at different stress ratios to evaluate the relationship between the fatigue life and stress amplitude or mean stress level. In the case of a fixed stress amplitude, the change in fatigue life with the stress ratio was 2~6% larger than the case of fixed maximum stress. Furthermore, this study observed the mechanism of initiation and propagation of the fatigue cracks in PP-LFT by scanning electron microscopy.

• Journal of Korean Society of Steel Construction
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• v.18 no.4
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• pp.417-426
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• 2006

Various fatigue damages have been reported in orthotropic steel deck structures put upon girders. These damages are caused by complex behaviors of the deck, which is directly subjected to vehicle loads. To estimate the causes of fatigue cracks at the welded connected parts of the trough rib and the flor beam, and the trough rib and the deck plate, in orthotropic steel deck structures, FE analyses were first, performed in this study. Parameter studies were carried out to suggest effective structural details that consider fatigue, in which the main parameters are the thickness of the deck plate, the shape of the connection of the trough rib and the flor beam such as the slit form, and the welding length. This study suggests that the effective structural details improved the fatigue strength and discusses.

• The Journal of the Korea Contents Association
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• v.13 no.12
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• pp.291-298
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• 2013

This study is a cross-sectional descriptive survey done to identify the relationship between job stress and fatigue in operating room nurses. Data were collected by surveying 124 operating room nurses who were working in operating rooms at two advanced general hospitals and five general hospitals in G city in the province of C, and the survey was conducted by questionnaires. The data were analyzed by descriptive statistics, t-test, ANOVA, and Pearson's correlation coefficient. The level of job stress and fatigue were 3.64(0.45), and 3.46(0.60). In case of job stress in operating room nurses, there was statistically meaningful difference according to hospital type, and their fatigue levels showed statistically meaningful difference according to types of hospital, work motivation, and subjective health condition. There was positive correlation(r=0.47, p=<.001) between operating room nurses' job stress and fatigue. Therefore, this study has significance in the respect that it identified the relationship of job stress and fatigue in operating room nurses, and it will be used as the basis to develop job stress intervention program for operating room nurses.

• The Journal of the Korea Contents Association
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• v.16 no.2
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• pp.456-466
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• 2016

The purpose of this study was to identify factors affecting clinical practice-related fatigue among undergraduate nursing students. The data were collected from a questionnaire distributed among 129 juniors and seniors (3rd and 4th year students) in nursing college at the G city, who were at the end of clinical practice. Multiple regression analysis found that the significant major predictors of clinical practice-related fatigue among nursing students were sleep quality (${\beta}=.30$), anxiety (${\beta}=.26$), exercise frequency (${\beta}=-.21$) and clinical practice stress (${\beta}=.19$). These variable factors could explain 33.6% of clinical practice-related fatigue among nursing students. This study suggests that sleep quality, anxiety, exercise frequency, and clinical practice stress are significant factors of clinical practice-related fatigue among nursing students. Therefore, strategies improving sleep quality and exercise and managing anxiety and stress should be developed to reduce the fatigue for nursing students during clinical exposure.

• Composites Research
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• v.17 no.6
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• pp.22-27
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• 2004

The objective of this work is to design Surface Antenna Structure (SAS) and investigate fatigue behavior of SAS that is asymmetric sandwich structure. This term, SAS, indicates that structural surface becomes antenna. Constituent materials are selected considering electrical properties, dielectric constant and tangent loss as well as mechanical properties. For the antenna performance, SSSFIP elements inserted into structural layers were designed fur satellite communication at a resonant frequency of 12.5 GHz and final demonstration article was $16{\;}{\tiems}{\;}8$ array antenna. From electrical measurements, it was shown that antenna performances were in good agreement with design requirements. In cyclic 4-point bending, flexure behavior was investigated by static and fatigue test. Fatigue life curve of SAS was obtained. The fatigue load was determined experimentally at a 0.75 (1.875kN) load level, Experimental results were compared with single load level fatigue life prediction equations (SFLPE) and in good agreement with SFLPE. SAS concept is the first serious attempt at integration fur both antenna and composite engineers and promises innovative future communication technology.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.41 no.9
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• pp.853-860
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• 2017

To evaluate the effects of mode II on the crack initiation and propagation stages, the effects in the fatigue threshold region under a mixed-mode I+II loading state was experimentally investigated. In the case of mixed-mode I + II, during the crack initiation stage, as the loading application angle (${\theta}$) increased, cracks occurred in the lower load owing to the effects of mode II, while the crack propagation rate decreased. The effects of mode II were experimentally investigated in the crack propagation stage by means of multilevel loading direction variation. Following mixed-mode I+II ($0^{\circ}{\rightarrow}{\theta}{\rightarrow}60^{\circ}$), as the load application angle increased, the fatigue crack propagation rate decreased, as did the fatigue crack propagation rate, which occurred later. Following mixed-mode I + II in case of(${\theta}{\geq}75^{\circ}$), the fatigue crack propagation rate was found to increase, while the fatigue life decreased.

• Proceedings of the KSR Conference
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• 2010.06a
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• pp.64-71
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• 2010

It is suggested that the service life of the continuous welded rail(CWR) is estimated by the relationship between the rail surface irregularity according to the accumulated passing tonnage and bending fatigue of welded part in CWR. In this study, based on the results of bending fatigue tests of rail and results of measuring tests in situ of rail bending stress, this study estimated the bending fatigue life of welded rail in concrete track, adopting a Haibach's rule. The bending fatigue life of CWR considered the rail surface irregularity, train speed and the S-N curve by types of rail welding. In addition, this study estimated it for the fracture probability 1%, 0.1%, 0.01%. Therefore, this study proposed bending fatigue life of CWR in concrete track.