• Journal of Korean Society of Environmental Engineers
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• v.39 no.12
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• pp.733-740
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• 2017

'The facilities standards of water supply' issued by the Ministry of Environment in 2004 indicates that expansion joints cannot be used in welding water supply steel pipes. However, their reason is not clear and it is difficult to confirm the stability of the steel pipe for a water supply pipeline. The purpose of this study is to determine whether or not an expansion joint is necessary to improve the stability of water supply in steel pipe through a displacement analysis of the pipework. The test results are as follows. Firstly, it was found that expansion and contraction of the water supply steel pipe (D 2,400 mm) occur repeatedly in 4 cycles per year, and the maximum expansion and contraction amount of the pipe is 13.03 mm in 1.24 km pipelines. Secondly, the thermal stress caused by expansion and contraction of the steel pipe is $13.7{\sim}36.1kgf/cm^2$ according to the burial depth (0~4 m). The main comparison factors to determine the stability of the steel pipe (STWW 400) were the allowable tensile strength and the fatigue limit, which were computed to be $4,100kgf/cm^2$ and $1,840kgf/cm^2$, respectively. Finally, the thermal stress of the steel pipe is very small compared to the allowable tensile stress and fatigue stress. Therefore, thermal stress does not affect the stability of the steel pipe, although the expansion and contraction of the steel pipe occurs by temperature changes. In conclusion, the study demonstrated that expansion joints are not required in water supply steel pipelines.

• Proceedings of the KSR Conference
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• 2007.11a
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• pp.595-600
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• 2007

Greater expansion and more frequent operation of the railroad transportation system anticipated due to its characteristics including low cost, safety and mass transportation. Recently, effects on the railway structures due to expansion of newly constructed road, construction of subway, city gas pipeline, communication network, electric power network and construction of other railway underground crossing in accordance with urban planning and organization has influenced safe operation of trains. Accordingly, standard for selection of construction method that will enable construction of more economical and rational subway underground crossing structures by preventing problems occurring at the time of above construction works and accidents in safe operation of trains due to construction in advance is definitively necessary. Although there are numerous construction methods that can be applied at the time of construction of railway underground crossing, there are much difficulties in selection of appropriate construction method that considers characteristics of each construction method on non-excavation type construction method, train operation plan of number of operational routes and on-site circumstances. Therefore, this research aims to present rational standard for selection of construction method for such, and standard for slowdown speed and interception of train when passing the areas of slowdown in sectors under construction.

• 대한공업교육학회지
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• v.34 no.1
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• pp.274-286
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• 2009

Fiber optic sensor is widely used in measuring acoustic and vibration. Especially interferometric sensors are more suitable to measure the acoustic signal. In this paper, a Fabry-Perot interferometric fiber optic sensor was used to measure flow induced vibration. This vibration also measured using an accelerometer, and the data was compared to one other. The venture, nozzle, drop barrel, and rapid expansion in the pipeline are the measuring objects. The flow rate is changed from 50 L/min to 150 L/min and the average flow velocity was about 7 m/s. Based on the experimental results the suggested fiber optic sensor detects flow induced vibration effectively. Therefore, this kind of fiber optic sensor can be applied to the monitoring the flow induced noise and vibration such as pipelines, cables, buildings.

• Journal of the Korean housing association
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• v.27 no.4
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• pp.59-66
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• 2016

The purpose of this study is to examine the necessity of 'emergency plumbing equipment for preventing the spread of water leakage'. It reviews social and economic costs when there is spread of water leakage and finds out that those are enormous. Expansion of water leakage causes conflicts between neighbors, economic loss and inconvenience from damages on facilities like elevator and power failure. Next, it examines the inability of existing plumbing equipment when it comes to spread of water leakage. Newly defined 'Surface Leakage' means rapid leak in the surface, and 'Internal Leakage' means seeping out slowly and gradually buried in the pipeline. It will also be analyzed by separating the concept of a leak in the two concepts of a 'Surface Leakage' and 'Internal Leakage'. It proposes emergency plumbing equipment for preventing the spread of water leakage as a solution for the expansion of water leakage. It explains general concepts of emergency plumbing equipment for preventing the spread of water leakage. It will also examine the effectiveness of the user by performing a survey of 420 multi-level building their opinion on the effects of an emergency plumbing equipments to prevent the spread of water leakage.

• Journal of the Korean Society of Industry Convergence
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• v.23 no.4_2
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• pp.653-659
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• 2020

In this study, seismic verification of the bellows used in the plant field was conducted. The pressure used in the analysis was analyzed by applying the design pressure of 15.7bar. For the seismic analysis, the natural frequency of the bellows system was obtained and the stability of the system was evaluated by static seismic analysis comparing the lowest order natural frequency with the dominant frequency of 33 Hz. The material of the bellows system is STS304, and the safety factor is obtained in comparison with the allowable stress. For the seismic analysis, the design response spectrum was prepared and the maximum acceleration was applied to the static seismic analysis and the stability of the entire system was confirmed. Compared to the structural analysis results, the maximum stress of the bellows system increased by about 16.4% and the maximum strain increased by about 3 times when seismic analysis was performed.

• Bulletin of the Korea Photovoltaic Society
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• v.4 no.2
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• pp.45-53
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• 2018

Natural gas demand for power generation continued to increase until 2013 due to the expansion of large-scale LNG power plants after the black-out of 2011. However, natural gas demand for power generation has decreased sharply due to the increase of nuclear power and coal power generation. But demand for power generation has increased again as energy policies have changed, such as reducing nuclear power and coal power plants, and abnormal high temperatures and cold waves have occurred. If the gas pipeline pressure can be properly maintained by predicting these fluctuations, it can contribute to enhancement of operation efficiency by minimizing the operation time of facilities required for production and supply. In this study, we have developed a regression model with daily power demand and base power generation capacity as explanatory variables considering characteristics by day of week. The model was constructed using data from January 2013 to December 2016, and it was confirmed that the error rate was 4.12% and the error rate in the 90th percentile was below 8.85%.

• Journal of the Korea Safety Management & Science
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• v.9 no.1
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• pp.1-8
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• 2007

To improve the practical application of the thermal expansion of closed long pipeline exposing to external heating sources such as solar energy, safety engineering and system optimization for relief valve in the closed piping system are suggested through theoretical approach, correlation in view of temperature and pressure increase caused by external solar energy in the closed piping system. The profile for thermal relief valve including relieving capacity, influx heat energy, sizing criteria, set pressure, selection against back pressure is also presented. It is noted that following topic on solar relief valve should be applied to engineering, installation and commissioning.

• Tunnel and Underground Space
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• v.30 no.2
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• pp.149-163
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• 2020

This paper presents a logistic regression and GIS based urban ground sink susceptibility assessment using underground facility information considering soil particle loss. In the underground environment, the particle loss due to water flow or groundwater level change leads to the occurrence and expansion of cavities, which directly affect the ground sink. Four different contributory factors were selected according to the two underground facility domains (water pipeline area, sewer pipeline area) and subway line area. The logistic regression method was used to analyze the correlation and to derive the regression equation between the ground sink inventory and the contributory factors. Based on these results, three ground sink susceptibility maps were generated. The results obtained from this study are expected to provide basic data on the area susceptible to ground sink and needed to safety monitoring.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2005.11a
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• pp.220-221
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• 2005

Sub-bottom profiler(SBP) has been used extensively for the mapping of basement in the foundation design of offshore structure, for pre- and post-dredging operations within harbors and channels, for selection of pipeline routes, sitting of drilling platforms, and in the exploration for an aggregates such as sands and gravels. During the construction of Siwha embankment for irrigation water and the expansion of arable land, the breaking of an embankment unfortunately occurred so that a lot of riprap was swept away and widely dispersed by the tide and strong current. The feasibility study for the construction of the tidal-powered electric plant in Siwha embankment was performed quite recently. Therefore we made use of SBP survey to investigate the distribution of the lost riprap. We could successfully map out the distribution of the lost riprap from the reflection amplitude characteristics of the sediments in SBP data set. We demonstrated the variation of reflection amplitude versus the sediments with and/or without riprap by means of the numerical modeling of acoustic wave equation using finite difference method. Also we examined an amplitude anomaly of the ripraped area through the physical modeling using ultrasonic.

• Journal of the Korea institute for structural maintenance and inspection
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• v.27 no.4
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• pp.23-32
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• 2023

The seismic performance of buried PE pipes is reported to be favorable due to their exceptional elongation capacity at break. Although a seismic performance evaluation procedure based on the response displacement method has been summarized in Korea for fusion-bonded PE pipes, there is currently no procedure available for mechanically jointed PE pipes. This article aims to present a seismic performance evaluation procedure based on the response displacement method specifically designed for mechanically jointed PE pipes in Korea. When employing the mechanical joining method for PE pipes, it is recommended to adhere to the evaluation procedure established for segment-type pipes. This involves assessing the stress induced by the pipe, the expansion and contraction strain of the joint, and the bending angle of the pipe joint. Furthermore, the coefficient of inhomogeneity of the soil, which is necessary for estimating the axial strain of the ground, is introduced. Additionally, a computation method for determining lateral displacement and reconsolidation settlement in soil susceptible to liquefaction is proposed. As a result of the sensitivity analysis considering the typical soil condition in Korea, the mechanically jointed PE pipe with a certain quality was shown to have good structural seismic safety when soil liquefaction was not considered. This procedure serves as a valuable tool for seismic design and evaluating the seismic performance of mechanically joined buried PE pipes, which are primarily utilized for connecting small-diameter pipes.