• Structural Engineering and Mechanics
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• 제62권1호
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• pp.65-77
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• 2017

The free vibration analysis of fluid conveying Timoshenko pipeline with different boundary conditions using Differential Transform Method (DTM) and Adomian Decomposition Method (ADM) has not been investigated by any of the studies in open literature so far. Natural frequencies, modes and critical fluid velocity of the pipelines on different supports are analyzed based on Timoshenko model by using DTM and ADM in this study. At first, the governing differential equations of motion of fluid conveying Timoshenko pipeline in free vibration are derived. Parameter for the nondimensionalized multiplication factor for the fluid velocity is incorporated into the equations of motion in order to investigate its effects on the natural frequencies. For solution, the terms are found directly from the analytical solution of the differential equation that describes the deformations of the cross-section according to Timoshenko beam theory. After the analytical solution, the efficient and easy mathematical techniques called DTM and ADM are used to solve the governing differential equations of the motion, respectively. The calculated natural frequencies of fluid conveying Timoshenko pipelines with various combinations of boundary conditions using DTM and ADM are tabulated in several tables and figures and are compared with the results of Analytical Method (ANM) where a very good agreement is observed. Finally, the critical fluid velocities are calculated for different boundary conditions and the first five mode shapes are presented in graphs.

• 한국해양공학회지
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• 제29권1호
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• pp.100-110
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• 2015

To meet the increasing demand for energy around the world, offshore and subsea energy development is constantly being conducted. This trend is accompanied by an increasing demand for pipeline installation, which brings numerous problems, including those related to accessibility, high pressure, and corrosion. Among these, corrosion is a primary factor in pipeline fractures, and can cause severe environmental and industrial damage. Hence, accurate corrosion assessment for corroded pipelines is very important. For this reason, the present study investigated the mechanical behavior of an idealized corroded subsea pipeline with an internal/external pressure load using the commercial FEA code ABAQUS. Then, the analysis result was compared with corrosion assessment codes such as ASME B31G, DNV RP F101, ABS. Finally, a fitness-for-service assessment was conducted.

• 대한조선학회논문집
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• 제55권4호
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• pp.289-296
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• 2018

The offshore subsea platforms are connected to subsea pipelines to transport gas/oil from wells. The pipe is a multilayered structure of polymer and steel for compensating both flexibility and strength. The pipe also requires reinforcement structures to endure the extreme environmental conditions. A vertebrae structure of bend restrictors is one of the reinforcement structures installed to protect the subsea pipe from excessive bending deformations. In this study, structural behaviors of the subsea pipeline with bend restrictors are investigated by the multi-body contact analysis in Abaqus 6.14-2. Contact forces of each bend restrictor extracted from the multi-body contact analysis can be boundary conditions for topology design optimization in Altair Hyperworks 13.0 Hypermesh-Optistruct. Multiple design constraints are considered to obtain a manufacturable design with efficient material usage. Through the multi-body contact analysis with optimized bend restrictors, it is confirmed that the bending performance of the optimized design is enhanced.

• 한국해양공학회지
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• 제32권2호
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• pp.84-94
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• 2018

Subsea pipelines are designed to transport mixtures of oil, gas, and their associated impurities from a wellhead that can be in excess of approximately $100^{\circ}C$, while the external temperature may be approximately $5^{\circ}C$. Heat can be lost from a subsea pipeline containing a high-temperature fluid to the surrounding environment. It is important that the pipeline be designed to ensure that the heat loss is small enough to maintain sufficient flow from the unwanted deposition of hydrate and wax, which occurs at a critical temperature of about $40^{\circ}C$. Therefore, it is essential to estimate the heat loss of a subsea pipeline in various circumstances. In previous studies, overall heat transfer coefficient(OHTC) formulas were considered only for a single soil type. Thus, it is difficult to characterize the OHTC of the actual seabed with multiple soil layers. In this paper, an OHTC formula that considers multi-layered soils is proposed for more precise OHTC estimation.

• 한국음향학회:학술대회논문집
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• 한국음향학회 2004년도 춘계학술발표대회 논문집 제23권 1호
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• pp.225-230
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• 2004

Leak noise is a good source to identify the exact location of a leak point of underground water pipelines. Water leak generates broadband noise from a leak location and can be propagated to both directions of water pipes. However, the necessity of long-range detect ion of this leak location makes to identify low-frequency acoustic waves rather than high frequency ones. Acoustic wave propagation coupled with surrounding boundaries including cast iron pipes is theoretical analyzed and the wave velocity was confirmed with experiment The leak locations were identified both by the acoustic emission (AE) method and the cross-correlation method. In a short-range distance, both the AE method and cross-correlation method are effective to detect leak position. However, the detect ion for a long-range distance required a lower frequency range accelerometers only because higher frequency waves were attenuated very quickly with the increase of propagation paths. Two algorithms for the cross-correlation function were suggested and a long-range detection has been achieved at real underground water pipelines longer than 300m.

• KEPCO Journal on Electric Power and Energy
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• 제3권1호
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• pp.49-56
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• 2017

In order to examine the feasibility of Carbon Capture & Sequestration, a major technological strategy for the national goal of greenhouse gas reduction, this paper studies the various methods and corresponding costs for the transportation of $CO_2$ captured at the domestic thermal power plants, as well as performing comparative analysis with overseas CCS demonstration projects. It is predicted that the investment cost would be about 98 million USD when the using land-based pipelines to transport captured $CO_2$ from the thermal power plant located in the south coast. And using marine-based offshore pipelines, it will cost about twice the amount. When the captured $CO_2$ is transported from the power plant in the west coast instead, the cost is expected to increase substantially due to the transportation distance to the storage site being more than double to that of the south coast power plant case.

• 한국콘텐츠학회논문지
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• 제13권8호
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• pp.44-51
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• 2013

래스터 연산은 트루 컬러 이미지(픽스맵)나, 단색 이미지(비트맵)을 표현하기 위해서 광범위하게 사용된다. 이 기능은 이미지 프로세싱 기능이나, 폰트 출력 시에 강하게 요구된다. 반면에, OpenGL ES 하드웨어 등을 포함하는, 현재의 모바일 그래픽스 플랫폼들에서는 이 기능을 직접 제공하지는 않는다. 모바일 그래픽스 플랫폼들에서 이러한 래스터 연산을 완벽히 제공하기 위해서, 본 논문에서는 그래픽스 이미지들을 3차원 점들의 집합으로 해석하고, 풀-소프트웨어 구현 방식으로, 이들 3차원 점들을 전형적인 3차원 기하 파이프라인으로 처리하게 했다. 구현 결과는 충분한 실행 속도를 보였고, 정확도를 증명하기 위한 공식 검증 테스트(conformance test)들을 모두 통과하였다.

• 복합신소재구조학회 논문집
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• 제6권4호
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• pp.16-23
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• 2015

The industrialization and urbanization forced to increase the density of pipelines such as water supply, sewers, and gas pipelines. The materials used for the existing pipe lines are mostly composed of concretes and steels, but it is true that the development for more durable and efficient materials has been continued performed to produce long lasting pipe lines. Recently, underground pipes serve in diverse applications such as sewer lines, drain lines, water mains, gas lines, telephone and electrical conduits, culverts, oil lines, etc. In this paper, we present the result of investigation pertaining to the structural behavior of unplasticized polyvinyl chloride (PVC-U) flexible pipes buried underground. In the investigation of structural behavior such as a ring deflection, pipe stiffness, 4-point bending test, experimental and analytical studies are conducted. In addition, pipe stiffness is determined by the parallel plate loading tests and the finite element analysis. The difference between test and analysis is about 8% although there are significant variations in the mechanical properties of the pipe material. In addition, it was found by the 4-point bending test there is no problem in the connection between the pipes by coupler.

• 한국산학기술학회논문지
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• 제13권6호
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• pp.2757-2762
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• 2012

하수관거는 중요한 사회간접시설중의 하나이다. 이러한 하수관거의 파손은 주로 하수관거의 시공에 이용되는 뒤채움재의 부적절한 품질관리 및 다짐관리로 인하여 발생한다. 특히, 원형관로의 경우 현장에서 다짐작업이 어려워 다짐기준을 만족시키기 어렵다. 이러한 문제를 해결하기 위하여 본 연구는 플라스틱 현장조립식 경량기초를 개발하였다. 개발된 경량기초의 하중재하시험 및 변형특성을 평가하였다. 제한된 실험결과로부터 현장조립식 플라스틱 경량기초의 사용은 뒤채움재의 다짐관리시 발생하는 어려움을 줄여줄 수 있는 대안으로 사용 가능함을 확인하였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 하계학술대회 논문집 A
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• pp.470-473
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• 2000

Because of the continuous growth of energy consumption, and also the tendency to site power lines and pipelines along the same routes, the close proximity of high voltage structures and metallic pipelines has become more and more frequent. Moreover, normal steady state and fault currents become higher as electric networks increase in size and power. Therefore, there has been and still is a growing concern (safety of people marking contact with pipeline, risk of damage to the pipeline coating, the metal and equipment connected to pipeline. especially cathodic protection system) about possible hazards resulting from the influence of high voltage power system on metallic structures(gas pipeline, oil pipeline and water pipeline etc.). Therefore, we analyze the interference problems when the gas pipeline is buried with power cable in the same submarine tunnel. This paper present the results of the study about interference mechanism, AC corrosion, limitation of safety voltage and analysis of indiction voltage.