• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2001년도 춘계학술대회 논문집
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• pp.254-259
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• 2001

There are advantages in the installation of dual subsea pipelines over two separate single lines. In many case it can reduce the cost for trench, back-filling and installation. However the installation of dual pipelines often requires technical challenges. Dual Pipelines should be placed to be stable to external loading not only during the installation but also in the design life. Dual pipelines in trench can reduce the influence of external forces. To investigate applied forces as slope changes, number of experiments are conducted with PIV (Particle Image Velocimetry) in a circulating water channel. Numerical approaches 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 pattern of flow around dual pipelines. it is proved that the trench slope affects the pipeline stability significantly. The results can be applied in the stability design of dual pipelines in trench section. The complex flow patterns can be referenced effectively linked in the understanding of fluid around circular bodies in trench.

• 한국해양환경ㆍ에너지학회지
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• 제19권4호
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• pp.286-296
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• 2016

해양 CCS는 화력발전소에서 배출되는 $CO_2$를 포집하여 해양 지중의 대수층이나, 고갈 유가스전까지 수송하여 저장하는 기술이다. 시간 경과에 따라 지중 저장소로 주입 및 저장되는 $CO_2$의 누적 양이 증가하며, 이는 저류층 압력의 상승을 동반한다. 저류층 압력의 상승은 수송 및 주입 시스템의 운전조건 변화를 유발한다. 따라서 초기 설계단계에서 이러한 사업시간의 경과에 따른 운전조건 변화를 반영한 분석이 요구된다. 본 연구에서는 국내 동해 대륙붕에 위치한 가스전을 $CO_2$ 저장소로 활용할 경우 시간 경과에 따른 해양 수송 및 주입 시스템 내 $CO_2$ 거동을 수치해석적 방법을 이용하여 분석하였다. 전체 시스템을 해저 파이프라인, 라이저, 탑사이드, 주입정으로 구성하고, 이를 OLGA 2014.1을 이용하여 모델링 및 해석하였다. 약 10년의 주입 운전기간동안 해저 파이프라인, 라이저, 탑사이드, 주입정에서의 $CO_2$ 압력과 온도, 상거동의 변화를 분석하였다. 이를 통해 해저 파이프라인 입구 압축기, 탑사이드 열교환기 및 주입정 정두 제어 등의 설계 방안을 제시하였다.

• 한국해안해양공학회지
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• 제8권1호
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• pp.81-86
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• 1996

해저 파이프라인은 해저 석유 및 천연가스 생산의 전반에 걸쳐 중요한 역할을 하나, 열악한 해양환경하에 있어 여러 가지 외부 요인에 의해 손상될 가능성이 높으며 그로 인한 피해는 막대하다. 본 논문에서는 해저 파이프라인의 안정성을 위협하는 주된 요인 중의 하나인 동적 자유경간을 해석하였으며, 해저 파이프라인 설계에 있어서 중요한 자유경간의 허용길이를 산출하였다. 자유경간의 허용길이는 와동방출의 진동수와 자유경간의 고유진동수와의 상관관계를 이용하여 산출하였고 경계조건에 따른 허용길이의 변화를 규명하였다. 자유경간 양단의 해저지반은 탄성기초로 간주하였으며, 이를 선형 및 회선 스프링으로 치환하여 경계조건을 일반화하였다. 본 연구를 통하여 여러 가시 지반조건에 대한 동석 자유경간의 정확한 허용길이를 간단하게 얻을 수 있는 무차원화 된 곡선을 구하였으며, 그 결과를 우리나라 동남해역 천연가스전에 설치예정인 해저 파이프라인에 적용하였다.

• 해양환경안전학회지
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• 제2권1호
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• pp.77-82
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• 1996

Subsea pipelines are exposed to several potential risks of damage due to wave, soil instability and other hazards. Structural failure of the steel pipelines will result in serious consequences such as release of transported hydrocarbons, pollution to the ocean environment and heavy costs due to repair. This paper examines the safety of subsea pipelines with free span which is one of high potential damages. The variation of an allowable length of static free span is examined for different boundary conditions and is given in a curve which is useful for the dsign of the subsea pipeline with a free span.

• 한국압력기기공학회 논문집
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• 제17권2호
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• pp.119-125
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• 2021

Subsea pipelines are widely used to transport hydrocarbons from ultra-deep seawater to facilities on the coast. A sandwich pipe is a pipe-in-pipe system in which the annulus between the two concentric steel pipes is filled with polymer cores and fillers for insulation and structural reinforcement. Sandwich pipeline is always exposed to complex loading such as bending moment, bulking, internal and external pressures caused by installation, operation and environmental factors. This research provides insights into the structural integrity of sandwich pipeline exposed to complex loading conditions using a linear matching method (LMM). The finite element model of the sandwich pipeline has been generated from previous research, and the model validation is performed by comparing the results of the linear analysis between the two models. The temperature dependent material properties are used to simulate the behavior of real pipeline, and the elastic-perfectly plastic (EPP) model has been taken into account for the material non-linearity. Numerical results provide comprehensive insights into the structural response of the sandwich pipeline under monotonic and cyclic loading and provide notable points about the evaluation of the plastic collapse limit and the elastic shakedown limit of the sandwich pipeline.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2000년도 춘계학술대회 논문집
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• pp.13-17
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• 2000

해저관로가 노출되어 있을 경우 파도와 조류 등에 의한 외적 하중으로부터 안정적이어야 한다. 트랜치 구간 내의 해저관로에 작용하는 유체 입자의 속도와 가속도는 해저면과 비교하여 볼 때 현저히 감소하므로 감쇄 계수를 사용하여 트랜치 구간 내에 설치되는 해저관로의 안정성을 해석한다. 그러나, 다양한 트랜치 구간의 깊이와 기울기에 대한 감쇄 계수에 대해 많은 자료가 부족하여 실제 설계에는 한정된 계수들이 이용된다. 본 논문에서는 다양한 깊이와 기울기를 가진 트랜치 구간의 실험 모형을 제작하여 회류 수조에서 P.I.V(입자 영상 속도계) 기법을 이용하여 여러 속도에 대하여 실험을 수행하였다. 다양한 트랜치 구간 내의 실린더 주변의 유동 특성과 유체 입자의 수평 속도를 측정하여 항력 감쇄 계수를 산출해 냈으며 실제 해양 공사에서 적용 가능한 안정성 해석 기준을 제시하였다.

• 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.

• Journal of Advanced Research in Ocean Engineering
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• 제3권2호
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• pp.53-58
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• 2017

This study introduces the case of pipelines installed in subsea conditions and buried offshore. Such installations generate pore water pressure under the seabed because of cyclic wave excitation, which is an environmental load, and consistent cyclic wave loading that reduce the soil shear strength of the seabed, possibly leading to liquefaction. Therefore, in view of the liquefaction of the seabed, stability of the subsea pipelines should be examined via calculations using a simple method for buried subsea pipelines and floating structures. Particularly, for studying the possible liquefaction of the seabed in regard to subsea pipelines, high waves of a 10- and 100-year period and the number of occurrences that are affected by the environment within a division cycle of 90 s should be applied. However, when applying significant wave heights (HS), the number of occurrences within a division cycle of 3 h are required to be considered. Furthermore, to research whether dynamic vertical load affect the seabed, mostly a linear wave is used; this is particularly necessary to apply for considering the liquefaction of the seabed in the case of pile structure or subsea pipeline installation.

• Ocean Systems Engineering
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• 제1권1호
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• pp.59-72
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• 2011

The objective of this work is to investigate the possibility of using the longitudinal strain on the surface of a pipe to determine the inception of dangerous free spanning. The long term objective is to develop an online monitoring technique to detect the development of dangerous free spanning in subsea pipelines. This work involves experimental study as well as finite element modeling. In the experiments, the strains at four points on a cross section of a pipeline inside the free span zone are measured. Pipes with different boundary conditions and different diameter to length ratios were tested. The pipe is treated as a simple beam with fixed-fixed or simply supported boundary conditions. The variation of the strains as a function of the diameter to length ratio gives a pointer to the inception of dangerous free spanning. The finite element results agree qualitatively with the experiments. The quantitative discrepancy is a result of the difficulty to replicate the exact boundary conditions that is used by the finite element program.

• 한국해양공학회지
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• 제29권3호
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• pp.207-216
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• 2015

Amanifold is one of the essential subsea oil and gas production components to simplify the subsea production layout. It collects the production fluid from a couple of wellheads, transfers it to onshore or offshore storage platforms, and even accommodates water and gas injection flowlines. This paper presents the basic design procedure for a manifold frame structure with novel structural verification using in-house unity check codes. Loads and load cases for the design of an SIL 3 class-manifold are established from a survey of relevant industrial codes. The basic design of the manifold frame is developed based on simple load considerations such as the self weights of the manifold frame and pipeline system. In-house software with Eurocode 3 embedded, called INHA-SOLVER, makes it possible to carry out code checks on the yield and buckling unities. This paper finally proves that the new design of the manifold frame structure is effective to resist a permanent and environment load, and the in-house code is also adaptively combined with the commercial finite element code Nastran.