• Journal of the Korea institute for structural maintenance and inspection
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• v.16 no.3
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• pp.51-59
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• 2012

Through this research safety factors were analyzed for concrete precast panels in road pavement which happens in lifting, moving, and installing. Two half size of full-scale precast concrete panels were made while one full-scale precast concrete panel was made. A series of strain gages for concrete and steel were installed and measured in lifting and transporting. Measurement results indicate that in case of 60 degree of lifting, small scale panel in dynamic motion produces about 3.54 times of strain compared to the static condition. However strain measurement of full-scale concrete panel in lifting and transportation does not yield any big difference compared to the small scale panels in the static condition. From this experimental results safety of the full-scale concrete panel was attained for the lifting system adopted in this research.

• Journal of the Korea institute for structural maintenance and inspection
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• v.19 no.2
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• pp.143-150
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• 2015

At present, the actual condition is that Korean modular structures are limited to a low rise detached house and military barracks. And there is no standardized structural design method of stacked modular structure. Accordingly, in general, they don't review impact force in the stage of stacking and installing a module, the effect which wind load has on a structure in the stage of lifting, and inertial force occurring in the stage of lifting or transporting a module in the process of constructing a structure. Therefore, this study investigated the construction method of modular system to be studied in stages, and decided on the position to which load was applied and boundary condition in structural analysis at each construction stage. Besides, inertial force according to each speed was calculated in the lifting and wheeled transport of module. And we calculated impact load according to lifting speed in module stacking and installation work and wind load due to instantaneous wind speed in the installation work by lifting. On the basis of the suggested method, in the modular system to be studied, it carried out review of structure by changing determining conditions of load being applied by construction stage, such as in the stage of lifting, in the stage of transport, and in the stage of installation, and drew construction conditions securing stability structurally.

• Journal of the Korea institute for structural maintenance and inspection
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• v.14 no.3
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• pp.91-99
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• 2010

In order to strengthen RC structures, various strengthening methods have been used. Particularly, external tendon strengthening method is very popular method to strengthen damaged structures in terms of efficiency, ease, economics. In this study, improved anchorage elements using the lifting hole were proposed to strengthen PSC or RC girder without any damage. Two types of anchorage elements were proposed and these elements were applied on six RC beams. Also, three types of existing anchorage elements were applied on three RC beams. Otherwise, any anchorage element was not applied on one RC beam to used as a control beam. To analyse behavior of these elements, static load tests were carried out. Test variables were anchorage shapes, prestressing level on the steel bar and tendon profiles. Deflections, strains and modes of failure were recorded to examine the strengthening effects of the beams. Ductility index and tendon stress were analyzed by comparing cracking load, yielding load and ultimate load. As a result, proposed anchorage elements using lifting hole were superior to existing anchorage elements in terms of strengthening effect and furthermore, they showed ductile behavior based on energy method.

• Journal of Magnetics
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• v.21 no.4
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• pp.586-592
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• 2016

The magnetic-jack type CRDM withdraws or inserts a control rod assembly from/to the reactor core to control the core reactivity. The CRDM housings form not only the path of the electromagnetic field but also the pressure boundary of a nuclear reactor, and a periodic in-service inspection should be carried out if there are welded or flange jointed parts on the pressure boundary. The in-service inspection is a time-consuming process during the reactor refueling, and moreover it is difficult to perform the inspection over the reactor head. A magnetic motor housing is applied for the current SMART CRDM and has several welding joints, however a nonmagnetic motor housing with fewer or no welding joints may improve the operational efficiency of the nuclear reactor by avoiding or simplifying the in-service inspection process. Prior to the development, the magnetic field transfer efficiency of the nonmagnetic housing was required to be assessed. It was verified and optimized by the electromagnetic analysis of the lifting force estimation. Magnetic flux rings were adopted to improve the efficiency. In this paper, the design and optimization process of a nonmagnetic motor housing with the magnetic flux rings for the SMART CRDM are introduced and the analyses results are discussed.

• Journal of the Korea institute for structural maintenance and inspection
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• v.12 no.4
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• pp.98-106
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• 2008

The strengthening in terms of efficiency, easy, economics is very popular method when it is applied to a damaged structures. The purpose of this study develops anchorage system that supports enough strengthening effect without any damage. In addition it is checked whether the method can be conveniently applied to structures. To verify strengthening effect a flexural experiments were performed. Four concrete beams were constructed and tested. Deflections, strains and modes of failure were recorded to examine strengthen of beams. Comparing crack load of each experimental data, yielding load, ultimate load, ductility index, and tendon stress were analyzed.

• Journal of agricultural medicine and community health
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• v.44 no.3
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• pp.138-143
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• 2019

Objectives: The purpose of this study was to assess the ergonomic risk factors in beekeeping, and to evaluate the effectiveness of assistive device hive lift. Methods: This study included 30 subjects of beekeeper in Pocheon, Korea. We assessed the ergonomic risk of main task in beekeeping with NLE, OWAS and evaluate the effectiveness of hive lift. We also surveyed prevalence of musculoskeletal symptoms among the subjects based on the Korea Working Condition Survey. Results: Moving to different floral origin, internal inspection of beehives, feeding syrup is the most burdensome to musculoskeletal system (NLE LI value=2~3. OWAS action category=4). The prevalence of musculoskeletal symptoms (lower and upper extremities) among the subjects was over 80 %. The introduction of assistive devices in the three hazardous tasks has dramatically reduced the risk by removing manual lifting hives (OWAS action category<1). Conclusions: Beekeeping is a heavy workload on the musculoskeletal system because it has a lot of manual lifting task. As a result of applying the hive lift, the burden could be reduced.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.40 no.7
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• pp.679-683
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• 2016

Boilers of large-sized coal-fired power plants are being operated under very poor conditions such as continuous operation or repeating of start-up and shutdown for a stable supply of electricity. Thus periodic inspection and maintenance are required to ensure reliability of operation. The loads of existing scaffolding systems for the maintenance of boilers are concentrated in the lower parts structurally, which may cause a serial collapse of the overall scaffolding system when there are problems in some members. Therefore, in this study, a safe furnace scaffolding system is developed by dispersing the loads in the upper part, as well as minimizing the hazards of serial collapsing. In addition, for cases where the direct installation of furnace scaffolding is challenging owing to the structure of the boiler tube, a lifting system for the installation of furnace scaffolding is developed so that furnace scaffolding can be supported to secure the integrity of the power generating facility.

• Journal of Navigation and Port Research
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• v.43 no.2
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• pp.93-100
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• 2019

In 2001, about 20 years after the introduction of the standard buoys, the natural environment and maritime traffic flow changes in the waters near Korea and the necessity of improvement of the AtoN (Aids to Navigation) maintenance was suggested. The IALA provides guidelines for maintenance and management of AtoN, and Korea provides guidelines for the management and operation of standard buoys by means of the Enforcement on the AtoN laws. The objective of this study was to investigate the installation status and the repair status of the standard type buoys by sea area in order to improve the management and operation of the steel standard buoys. In addition, a survey was conducted on the improvement of the steel buoy fouling and the improvement of the lifting inspection cycle towards on the AtoN managers and producers of the representative authority by sea area. In the case of LL-26 (M) buoy type, the standard type buoy installation status of Korea in 2017 was 57.1%, and the LL-26 (M) type was 58.9% showing the highest repair rate. According to the results of the survey on buoys fouling, 51.2% were caused by the attachment of shellfish, and 43.2% were caused by bird feces. The results of the survey on the improvement of the regular buoy inspection cycle showed that the measures are to maintain the current inspection period of 2 years regardless of the characteristics of the sea area (water depth, inside and outside port, buoy size, etc.).

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.629-636
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• 2003

The purpose of this study is localization of safety relief valves for Nuclear Service through technical development with overall design, fabrication, inspection, capacity certification test and functional qualification test of safety relief valves in accordance with ASME Section III and KEPIC Code. Safety relief valve is the important equipment used to protect the pressure vessel, the steam generator and the other pressure facility from overpressure by discharging the operating medium when the pressure of system is reaching the design pressure of the system. But we're depending on technology of the other country up to the present time. Because we don‘ have our own technologies, we have been spent the great time and money on installing and repairing safety relief valve at nuclear power plant. Therefore we have to achieve the development of safety relief valves for Nuclear Service with our own technologies.

• 유체기계공업학회:학술대회논문집
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• 2004.12a
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• pp.492-500
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• 2004

The purpose of this study is localization of safety relief valves fur Nuclear Service through technical development with overall design, fabrication, inspection, capacity certification test and functional qualification test of safety relief valves in accordance with KEPIC MN Code(or ASME Sec.III ). The safely relief valve is the important equipment used to protect the pressure vessel, the steam generator and the other pressure facility from overpressure by discharging the operating medium when the pressure of system is reaching the design pressure of the system. But we're depending on technology of the other country up to the present time. Because we don't have our own technologies, we have been spent the great time and money on installing and repairing safety relief valve at nuclear power plant. Therefore we have to achieve the development of safety relief valves for Nuclear Service with our own technologies.