• Structural Engineering and Mechanics
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• v.47 no.2
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• pp.167-183
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• 2013

Methods for estimating structural reliability using probability ideas are well established. When the residual ultimate strength of a buried pipeline is exceeded the limit, breakage becomes imminent and the overall reliability of the pipe distribution network is reduced. This paper is concerned with estimating structural failure of underground flexible pipes due to corrosion induced excessive deflection, buckling, wall thrust and bending stress subject to externally applied loading. With changes of pipe wall thickness due to corrosion, the moment of inertia and the cross-sectional area of pipe wall are directly changed with time. Consequently, the chance of survival or the reliability of the pipe material is decreased over time. One numerical example has been presented for a buried steel pipe to predict the probability of failure using Hasofer-Lind and Rackwitz-Fiessler algorithm and Monte Carlo simulation. Then the parametric study and sensitivity analysis have been conducted on the reliability of pipeline with different influencing factors, e.g. pipe thickness, diameter, backfill height etc.

• Journal of the Korean Society for Advanced Composite Structures
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• v.6 no.2
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• pp.91-96
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• 2015

GRP pipe (Glass-fiber Reinforced Plastic Pipe) lines making use of FRP (Fiber Reinforced Plastic) are generally thinner, lighter, and stronger than the existing concrete or steel pipe lines, and it is excellent in stiffness/strength per unit weight. In this study, we present the result of field test for buried GRP pipes with large diameter(2,400mm). The vertical and horizontal ring deflections are measured for 387 days. The short-term deflection measured by the field test is compared with the result predicted by the Iowa formula. In addition, the long-term ring deflection is predicted by using the procedure suggested in ASTM D 5365(ANNEX) in the range of 40 to 60 years of service life of the pipe based on the experimental results. From the study, it was found that the long-term vertical and horizontal ring deflection up to 60 years is less than the 5% ring deflection limitation.

• Proceedings of the Korean Geotechical Society Conference
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• 2006.03a
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• pp.1326-1333
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• 2006

Purpose of this research is a development for the curve fitted equations that can improve practical calculation and work application when seismic performance has been evaluated and this work has been made a study of the dynamic response under various boundary conditions of buried pipelines to compare the dynamic behavior of concrete pipe and steel pipe, FRP pipe. This research have been developed curve fitted equations that can be improving efficiency and practicality. Using a nonlinear least square method, and after testing several different exponential equations, Proposed the curve fitted equations to give the best result and constant value by the propagation velocities. With these results, dynamic response analysis and seismic performance evaluation have been achieved on concrete pipe, steel pipe and FRP pipe that have a various boundary conditions. Degree of a polynomial expression and coefficient value by propagation velocity have been calculated when using the curve fitting equations.

• Journal of the Korean Institute of Gas
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• v.22 no.5
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• pp.62-71
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• 2018

According to own investigation conducted by Korea Gas Safety Corporation Gas Safety Research Institute in 2017, the length of underground pipes in domestic high-pressure gas pipelines is approximately 770km, of which 84% is buried in Ulsan and Yeosu industrial complexes. In particular, 56% of underground pipelines have been in operation for more than 20 years. This suggests urgent management of buried high pressure gas pipelines. PHMSA in US and EGIG in Europe, major causes of accidents in buried gas pipelines are reported as third party damage, external corrosion and loss of pipe wall thickness. Therefore, it is important to evaluate whether the defects affect the remaining life of the pipe when defects occur in the pipe. DNV and ASME have evaluated the residual strength of pipelines through the hydraulic rupture test using pipe specimens with artifact flaws. Once the operating pressure is known through the residual strength of the pipe, the wall thickness at the point at which the pipe ruptures is calculated. If we know the accurate rate of corrosion growth, we can predict the remaining life of pipe. In the study, we carried out experiments with A53 Grade.B and A106 Grade.B, which account for 80% of domestic buried pipes. In order to modify the existing model equation, specimens with a defect depth of 80% to 90% was tested, and a formula expressing the relationship between defect and residual strength was made.

• Journal of Korean Society of Water and Wastewater
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• v.28 no.4
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• pp.491-500
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• 2014

Due to rapid urbanization and industrialization, water supply and sewer line systems are also developed relevantly. Manhole is an essential component structure of the pipeline system. Manhole is a structure constructed to accommodate the direction, dimension, differences in level, and easy of maintenance in the pipeline system. In this paper we present the result of investigations pertaining to the structural behavior of PVC sewer manhole buried underground. In the paper mechanical properties of PVC material are reported. In addition, by the finite element analysis (FEA), we confirmed that a PVC double-wall corrugated pipe manhole, when it is buried underground, is safe for the stress as well as buckling strength if the manhole is constructed within the suggested limit of buried depth.

• The Journal of the Acoustical Society of Korea
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• v.31 no.7
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• pp.449-460
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• 2012

The importance of the leak detection of a buried pipe in a power plant of Korea is being emphasized as the buried pipes of a power plant are more than 20 years old. The objective of this work is to enhance the capability of the leak detection technique in a noisy environment. For this purpose, a modified cross-correlation method that can effectively remove the rotating machinery noise component is suggested. In addition, a method for leak point detection using phase information of cross-spectrum is suggested. The validity of the proposed method is verified by performing an experiment. The experimental result demonstrates that the performance of the cross-correlation method can be enhanced by reducing the periodic noise components due to mechanical equipment.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.51 no.1
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• pp.5-14
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• 2002

In this paper, we analyze inductive interference in conductive material around 345 kV power transmission line, and evaluate the effects of mitigation wires. Finite element method (FEM) is used to numerically compute induced eddy currents as well as magnetic fields around powder transmission lines. In the analysis model, geometries and electrical properties of various elements such as power transmission line, buried pipe lines, overhead ground wire, and conducting earth are taken into accounts. The calculation shows that mitigation wire reduces fairly good amount of eddy currents in buried pipe line. To find the optimum magnetic field shielding location of mitigation wire, we applied evolution strategy algorithm, a kind of stochastic approach, to the analysis model. Finally, it was shown that we can find more effective shielding effects with optimum location of one mitigation wire than with arbitrary location of multi-mitigation wires around the buried pipe lines.

• Journal of the Korean Society for Nondestructive Testing
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• v.30 no.6
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• pp.539-547
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• 2010

In this study, characteristics of the fundamental longitudinal guided wave mode, L(0,1), which is a usual mode employed in the inspection of the above-ground pipe, of the buried pipe were numerically investigated considering property changes in the surrounding soil. Results showed that soil conditions are significantly affecting the attenuation of L(0,1) mode in the pipe embedded in soil. Especially, if the soil is partially saturated, the attenuation of L(0,1) mode is larger and is very similar regardless of the degree of water saturation in the surrounding soil. However, when the soil is fully saturated, the attenuation of L(0,1) mode is less and show different trend with its partially saturated counterparts.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.09a
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• pp.963-966
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• 2009

A Construction of pipe line foundation and railroad, buildings in a permafrost area requires engineering technology of ground stabilization. In the permafrost area, thermal siphons have been used to stabilize foundation by eliminating the heat of ground to the air. the thermal siphon is a passive heat transfer device that operates by convection through vaporization and condensation. The heat transfer from ground to the air is driven by a temperature difference across the unit. A buried part in ground working as vaporizing function and upper part work as condensing. In this study, buried thermal siphon around the pipe lines laid in the Vladivostok site and measuring temperature variation. It is found that the thermal siphons freezing ground faster and decrease temperature variation in winter season.

• Proceedings of the Korean Geotechical Society Conference
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• 2002.03a
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• pp.439-444
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• 2002

Geothermal or ground source heat pumps(GSHPs) are electrically powered systems that take advantage of the earth's relatively constant temperature to provide heating, cooling, and hot water for homes and commercial buildings. The buried pipe, or ground loop, is the most recent technical advance in heat pump technology. The idea to bury pipe in the ground to gather heat energy began in the 1940s. Only recently, however, have new heat pump designs and improved buried pipe materials been combined to make GHP systems the most efficient heating and cooling systems available. The aim of the study is application of the GSHP system in korea. Our environments for economy, politics and society are different from other countries. For a case, the progressive tax rate of home electricity is represented.