• Journal of the Korea institute for structural maintenance and inspection
• /
• v.7 no.1
• /
• pp.157-163
• /
• 2003

Recently, the number of Prestressed Concrete(PSC) bridges needed repair and retrofit because of the increase of heavy traffic loads and aging of concrete materials. But there are a few related researches about strengthening PSC bridges. In this study, the practicability of strengthening methods for PSC beam were studied by the static experimental method. PSC beams in length of 6m were made with concrete slabs. Glass fiber sheeting and external post-tensioning methods were used for strengthening PSC beams. Some beams were strengthened after cracks to investigate the applicability for cracked bridges. As a result, there strengthening methods were efficient at increasing the cracking loads and the failure load, to decrease deflection and prevent cracks. In the case of using glass fiber retrofit methods, it should be careful in the anchorage problems for preventing the bonding failure.

• Nuclear Engineering and Technology
• /
• v.27 no.3
• /
• pp.327-335
• /
• 1995

The normal shutdown and maintenance period of a nuclear power plant can be remarkably shortened when the examination and maintenance works in steam generator tubes are simultaneously carried out with refueling job. There are nozzle dams to Hock the coolant How from reactor to steam generator. Workers are reluctant to install nozzle dam because of the high radiation exposure and the limited working space in steam generator. Moreover, the heavy weight of present nozzle dam makes it installation and removal works much difficult. In this paper, a lighter KAERI nozzle dam with increased flexural rigidity-to-weight was designed and manufactured by changing the structure design of the present nozzle dam and by selecting new material, carbon fiber-reinforced plastic.

• International conference on construction engineering and project management
• /
• 2009.05a
• /
• pp.1189-1194
• /
• 2009

A gutter-shaped U grating is a facility that is installed at the sides of a road to provide pedestrians with a rainwater-free road. The previous studies on this facility focused mainly on the progress of the efforts that are being made to improve its performance and interception efficiency so as to prevent damages in regional areas due to the heavy rains caused by climate change. The studies on its maintenance, however, are still inadequate. Therefore, this study was conducted to analyze and compare the life cycle costs and performance evaluations of the steel and magic gratings, which are installed in apartments. The results of the study show that the replacement period and rate of gratings differ depending on where they are installed. The initial capital investment cost of a magic grating installed at a road where many vehicles pass is quite high, but in terms of its maintenance and entire-life-cycle costs, its total expenses are lower than those of a steel grating. The results of this study are expected to serve as preliminary data for the selection of an adequate grating that is suitable for particular places in the design phase of construction projects.

• Journal of the Korea Safety Management & Science
• /
• v.26 no.2
• /
• pp.43-53
• /
• 2024

This study analyzes the importance-performance analysis (IPA) of the 10 dimensions of the smart construction safety management system, and analyzes which dimensions are important and which dimensions are performing to determine key improvement tasks, incremental improvement tasks, Maintenance and reinforcement tasks and continuous maintenance tasks were derived. Among the 10 dimensions of the smart construction safety management system, the dimensions that are recognized as important by all field managers and field workers and have high performance are the automatic risk displacement measurement system, smart environmental sensor system, and heavy equipment seizure prevention system. However, areas that were perceived as having high importance but low performance were worker location tracking systems, smart safety helmet chin muscles, and smart safety ring fastening. Among the smart construction safety management systems perceived by field managers, areas for key improvement with high importance and low performance included worker location tracking system and smart safety ring fastening. Among the smart construction safety management systems perceived by field workers, the area for key improvement with high importance and low performance was the automatic risk displacement measurement system.

• Transactions of the KSME C: Technology and Education
• /
• v.1 no.1
• /
• pp.49-57
• /
• 2013

The dimensioning accidental loads have been selected through suitable quantitative risk assessment and generally utilized important factors for offshore facility design. The fire hazard can be quantified with dimensioning fire loads. The main purposes of fire protection are to maintain the functionality of safety systems within evacuation period and to prevent the escalation from initial fire to uncontrolled catastrophic fire. This paper introduces the applications and the design methods of active and passive fire protections as representative measures of fire protection of offshore facilities. The passive fire protection requires the high initial installation cost and much difficulty on the operation of facilities and their maintenance. The oil major clients have asked the design contractors of offshore facilities to optimize the amount of passive fire protection with relevant engineering technology recently.

• Journal of Wetlands Research
• /
• v.19 no.4
• /
• pp.501-507
• /
• 2017

The heavy metal such as Nikel (Ni) in industrial wastewater is one of the major reasons of decreasing nitrification efficiency in municipal wastewater treatment plants (MWTPs). In this study, laboratory scale reactors were operated in order to analyse of nitrification efficiency and improvement measures. As a result, nitrification efficiency during high Ni concentration (0.295 mg/L) was about 20%. However nitrification efficiency during low Ni concentration (0.114 mg/L) was over 70%. The changes of the micro-organism activity according to Ni concentration was investigated as being the major reason behind the gap of nitrification efficiency through analysing AUR and SNR. Increasing the HRT in high Ni concentration also increased the nitrification efficiency. Thus, maintenance of microorganisms and increasing the HRT in nitrification reactors suggests that measures taken to treat wastewater is positively correlated with high concentration of heavy metal.

• Journal of the Korean Society of Environmental Restoration Technology
• /
• v.15 no.6
• /
• pp.53-59
• /
• 2012

This this study was conducted with the aim of doing experiment on the effect of water purification by using an artificially built plant island, which is one of the eco-techniques, and aquatic plants as a plan for the reuse of water for obtaining water resources, thereby analyzing the removed quantity, and applying the experimental results to the reuse of water. As a result of doing experiments, this study obtained a good measured value of BOD (biochemical oxygen demand) 4.7mg/L, and COD (chemical oxygen demand) 7.2mg/L below the heavy water standard of BOD 10mg/L and COD 20mg/L, respectively. The chromaticity showed 89.2% removal efficiency, but final treated wastewater was found to show chromaticity 58 degrees exceeding chromaticity 20 degrees which are the water quality standard of the reuse of water. The results revealed that T-N produced 27% removal efficiency on an average while T-P produced 38% removal efficiency on an average, showing that the removal effect of N & P wasn't big. According to the currently enforced "Water Quality Standard of Heavy Water by Use", the use of water for sprinkling and landscaping was found to be available. Accordingly, this study suggested a nature-friendly, economically-efficient, and eco-technological water treatment technique which will make it possible to overcome the limit of the existing physio-chemical water treatment technology, reduce the costs for maintenance and facilities, and also reduce the limit of space restraint for installation of facilities.

• Journal of Electrical Engineering and Technology
• /
• v.13 no.3
• /
• pp.1166-1172
• /
• 2018

Degradation due to delamination occurs frequently in the high temperature superconductors (HTS) coil of rotating machines made with 2nd generation (2G) HTS wire, and the authors have observed other similar cases. Since an HTS field coil for a rotating machine is required to have stable current control and maintain a steady state, co-winding techniques for insulation material and epoxy resin for shape retention and heat transfer improvement are applied during coil fabrication. However, the most important limiting factor of this technique is delamination, which is known to be caused by the difference in thermal expansion between the epoxy resin and 2G HTS wire. Therefore, in this study, the experimental results of mixing the ratio of epoxy resin and alumina ($Al_2O3$) filler were applied to the fabrication of small and large test coils to solve the problem of degradation. For the verification of this scheme, eight prototypes of single pancake coils with different shapes were fabricated. They showed good results. The energization and operation maintenance tests of the stacked coils were carried out under liquid neon conditions similar to the operation temperature of an MW-class rotating machine. In conclusion, it was confirmed that the alumina powder mixed with epoxy resin in an appropriate ratio is an effective solution of de-lamination problem of 2G HTS coil.

• Journal of the Korean Society of Hazard Mitigation
• /
• v.9 no.1
• /
• pp.99-105
• /
• 2009

The main purpose of this work is to analyse damages caused by debris flows during the heavy rainfalls at Inje of Kangwon Province, Korea. A series of site investigations have been carried out to survey the characteristics of debris flows occurred during the summer season of 2006. It has been found that major losses in human life and property are caused by discharge of soil and rock fragments from landslides. During the rainfall high precipitation rate of 113.5 mm/hour and 355 mm/day was recorded, which could happen at 80-500 year period. Comparing the rainfall record with the time of landslides being occurred, occurrence of the landslides is directly related to heavy rainfalls. At present, several debris barriers have been built at the valleys and natural slopes have been protected by the seed spray method. It is intended to propose an alternative of restoration of landslide damages and maintenance based on findings from the current study.

• Journal of Korean Society of Rural Planning
• /
• v.17 no.2
• /
• pp.23-32
• /
• 2011

The purpose of this study is to produce basic planning criteria required in ecological restoration and improvement works of streams in rural area through the application of stream assessment methods (water quality, soil environment, and ecological function assessment) at 6 study sites of Han River basin. The investigation results were as followings; 1) There were the evaluation items like a manure use, salt degree, river peripheral tree, which did not fitted to apply to domestic streams, in the SVAP (Stream Visual Assessment Protocol) and NRCS Riparian Assessment that were evaluation models developed in USDA. The area inhabitants with a little knowledge and education personally seems to utilize the evaluation methods through improvement partly with an aspect that evaluation is slightly easy. 2) From the stream assessment results, the construction of diverse pools, large woody debris and isolated backwater pool are needed to improve a few of problems observed at the mostly study sites. The result of NRCS Riparian Assessment showed that the improvement of stream bank vegetative communities is needed by planting tree with deep-binding root masses, and managing of noxious weeds and exotic undesirable plants. 3) Summing up, the assessment results showed that the assessment scores were higher at upstream than downstream, the stream with totally maintenance than that with partly maintenance, the stream with slope bank than that with vertical bank, and the stream with a flood plain than that without a flood plain. So, the direction of stream maintenance projects must be set by consideration of those results.