• Journal of Ship and Ocean Technology
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• v.6 no.2
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• pp.12-22
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• 2002

Offshore pipelines play an important role in the transportation of gas, oil, water and oil products. It is common to have a group of pipelines in the oil and gas field. To reduce the installation cost and time, dual pipelines are designed. There are great advantages in the installation of dual pipelines over two separate single lines. It can greatly reduce the cost for trench, back-filling and installation. However the installation of dual pipelines often requires technical challenges. Pipelines should be placed to be stable against external loadings during installation and design life period. Dual pipelines in trench can reduce the influence of external forces. To investigate the flow patterns and forces as trench depth and slope changes, number of experiments are conducted with PIV(Particle Image Velocimetry) equipment in a Circulating Water Channel. Numerical approaches to simulate experimental conditions are also made to compare with experimental results. The velocity fields around dual pipelines in trench are investigated and analysed. Comparison of both results show similar patterns of flow around pipelines. It is proved that the trench depth contributes significantly on hydrodynamic stability. The trench slope also affects the pipeline stability. The results can be applied in the stability design of dual pipelines in trench section. The complex flow patterns can be effectively linked in the understanding of fluid motions around multi-circular bodies in trench.

• Geomechanics and Engineering
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• v.30 no.4
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• pp.383-392
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• 2022

Although pipelines are composed of segmental tubes commonly connected by rubber gasket or push-in joints, current studies mainly simplified pipelines as continuous structures. Effects of joints on three-dimensional deformation mechanisms of existing pipelines due to tunnel excavation are not fully understood. By conducting three-dimensional numerical analyses, effects of pipeline burial depth, tunnel burial depth, volume loss, pipeline stiffness and joint stiffness on bending strain and joint rotation of existing pipelines are explored. By increasing pipeline burial depth or decreasing tunnel cover depth, tunneling-induced pipeline deformations are substantially increased. As tunnel volume loss varies from 0.5% to 3%, the maximum bending strains and joint rotation angles of discontinuous pipelines increase by 1.08 and 9.20 times, respectively. By increasing flexural stiffness of pipe segment, a dramatic increase in the maximum joint rotation angles is observed in discontinuous pipelines. Thus, the safety of existing discontinuous pipelines due to tunnel excavation is controlled by joint rotation rather than bending strain. By increasing joint stiffness ratio from 0.0 (i.e., completely flexible joints) to 1.0 (i.e., continuous pipelines), tunneling-induced maximum pipeline settlements decrease by 22.8%-34.7%. If a jointed pipeline is simplified as a continuous structure, tunneling-induced settlement is thus underestimated, but bending strain is grossly overestimated. Thus, joints should be directly simulated in the analysis of tunnel-soil-pipeline interaction.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2000.10a
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• pp.184-191
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• 2000

In this research, a numerical model is developed for analysis of buried pipelines considering longitudinal permanent ground deformation(PGD) due to liquefaction induced lateral spreading. Buried pipelines and surrounding soil are medeled as continuous pipelines using the beam elements and a series of elasto-plastic springs uniformly distributed along the pipelines, respectively. Idealized various PGD patte군 based on the observation of PGD are used as a loading configuration and the length of the lateral spread zone is considered as a loading parameter. Numerical results are verified with other research results and efficient applicability of developed procedure is shown. Analyses are performed by varying different parameters such as PGD pattern, pipe diameter and pipe thickness. Results show that response of buried pipelines are more affected by pipe thickness than pipe diameter. Finally, the critical length of the lateral spread zone and the critical magnitude of PGD which cause yielding, local buckling or tension failure are proposed for the steel pipe which are normally used in Korea.

• Journal of the Korean Society of Industry Convergence
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• v.8 no.4
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• pp.197-204
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• 2005

It is well known that pipelines have the highest capacity and are the safest and least environmentally disruptive form of transporting oil and gas. However, pipeline damages caused by both internal and external corrosion is a major concern threatening the reliability of oil and gas transportation and the soundness of pipeline structure. In this study, we estimated the expected allowable damage defect by comparing the ASTM B31G code which has been developed as the evaluation method of reliability and incident prevention of damaged pipelines based on the amount of loss due to corrosion and the yield strength of materials to a modified theory considering diverse detailed corrosional forms. Furthermore, we suggested the method that estimates the expected life span of used pipelines by utilizing the reliability method based on major variables such as, the depth and length of damage and corrosional rate affecting the life expectancy of pipelines.

• Journal of the Korean Society for Precision Engineering
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• v.21 no.1
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• pp.173-180
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• 2004

This paper presents the effect of varying boundary conditions such as ground subsidence, internal pressure and temperature variation for buried pipelines on failure prediction by using a failure probability model. The first order Taylor series expansion of the limit state function incorporating with von-Mises failure criteria is used in order to estimate the probability of failure mainly associated with three cases of ground subsidence. Using stresses on the buried pipelines, we estimate the probability of pipelines with von-Mises failure criterion. The effects of varying random variables such as pipe diameter, internal pressure, temperature, settlement width, load for unit length of pipelines, material yield stress and pipe thickness on the failure probability of the buried pipelines are systematically studied by using a failure probability model for the pipeline crossing ground subsidence regions which have different soil properties.

• Proceedings of the Korean Geotechical Society Conference
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• 2000.11a
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• pp.471-478
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• 2000

Ground movements are inevitably caused by tunnel construction in soft ground. In the design and construction of tunnels in urban areas, the potential effects of buried pipelines by ground movements are one of the important design cosiderations. Generally, the most common modes of failure of buried pipelines due to ground movements are tensile fracture of main pipelines, rotation angle and pull-out displacement at joints. In the parametric study, a wide range of conditions were considered, including tunnel diameter(D), tunnel depth(Z$\sub$0/), volume loss(V$\sub$ι/) and inflection point(i). Based on this results, design charts, which are applicable to assess potential damage of buried pipelines associated ground movements due to tunnelling, are developed.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.1557-1560
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• 2003

This paper presents the effect of varying boundary conditions such as ground subsidence on failure prediction of buried pipelines. The first order Taylor series expansion of the limit state function is used in order to estimate the probability of failure associated with three cases of ground subsidence. We estimate the distribution of stresses imposed on the buried pipelines by varying boundary conditions and calculate the probability of pipelines with von-Mises failure criterion. The effects of random variables such as pipe diameter, internal pressure, temperature, settlement width, load for unit length of pipelines, material yield stress and thickness of pipeline on the failure probability of the buried pipelines are also systematically studied by using a failure probability model for the pipeline crossing a ground subsidence region.

• 유체기계공업학회:학술대회논문집
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• 2004.12a
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• pp.665-672
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• 2004

Chemical cleaning of boiler pipelines is necessary before the commissioning of thermal power plant after many years of construction. Fluid-Dynamic study for the chemical cleaning of boiler piplelines in Young-Heung thermal power plant is carried out. First, flow velocity necessary to sustain and exhaust solid particles in the vertical pipelines is calculated. Second, the flowrate necessary to make the calculated velocities in each vertical pipelines is calculated. Third, all the pipelines are analyzed with the Piping Systems Fluid Flow software to calculated the pressure loss in the pipelines. Finally, the operating point of the applied pump is calculated with the help of the same software.

• Earthquakes and Structures
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• v.5 no.4
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• pp.417-438
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• 2013

This study was concerned on the application of a hybrid approach for analyzing the buried pipelines deformations subjected to earthquakes. Nonlinear time-history analysis of Finite Element (FE) model of buried pipelines, which was modeled using laboratory data, has been performed via selected earthquakes. In order to verify the FE model with experiments, a statistical test was done which demonstrated a good conformity. Then, the FE model was developed and the optimum intersection angle of pipeline and fault was obtained via genetic algorithm. Transient seismic strain of buried pipeline in the optimum intersection angle of pipeline and fault was investigated considering the pipes diameter, the distance of pipes from fault, the soil friction angles and seismic response duration of buried pipelines. Also, a two-layer perceptron Artificial Neural Network (ANN) was trained using results of FE model, and a nonlinear relationship was obtained to predict the bending strain of buried pipelines based on the pipes diameter, intersection angles of the pipelines and fault, the soil friction angles, distance of pipes from the fault, and seismic response duration; whereas it contains a wide range of initial input data without any requirement to laboratory measurements.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.3
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• pp.865-873
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• 2013

This paper proposes a theoretical solution of elastic critical buckling load of infinitely long pipelines with non-uniform thickness under external pressure. The non-uniform cross section of pipelines can be considered as corroded or stiffened pipelines so that this paper can be a fundamental research of pipelines that are essential technology for offshore industries. The theoretical solution of pipelines with non-uniform thickness is derived with an assumption that a cylindrical shell under external pressure can be considered as a simple ring. The eigenfunctions are derived to obtain the critical buckling load. The reduced thickness and the reduced range are considered as variables in parametric analysis. The finite element analysis is performed to verify the theoretical solutions and the results of the analytic method and the finite element method are in good agreement.