• Journal of the Society of Naval Architects of Korea
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• v.55 no.4
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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 Ocean Engineering and Technology
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• v.20 no.5 s.72
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• pp.9-14
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• 2006

This paper presents an analytical method, application of expansion, mechanical design, and integrated expansion design of subsea insulated pipe-in-pipe (PIP) systems. PIP system consists of a flowline and a casing pipe for the transport of high temperature and high pressure product from the subsea wells. To prevent heat lass from the fiowline, insulation material is applied between the pipes. The fiawline pipe and the casing pipe have mechanical connections through steel ring plate (water stops) and bulkheads. Pipeline expansion is defined by temperature, internal pressure, soil resistance, and interaction force between the flowline and the casing pipe. The results of the expansion analysis, the mechanical design of connection system of the two pipes and tie-in spool design are integrated for the whole PIP system.

• Journal of the Korean Society of Marine Environment & Safety
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• v.22 no.7
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• pp.892-899
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• 2016

Gravity current flow past a subsea pipe above a scour based on computational fluid dynamics. For comparison, gravity current flow over pipe above a smooth bed also calculated, this configuration conventionally employed to consider the scour effect from an ideal approach. Interestingly, there different flow features and hydrodynamic forces between the scour and smooth bed cases. These results indicate that realistic conditionvery important investigatthe scour effect on gravity current flow around subsea pipe.

• Ocean Systems Engineering
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• v.1 no.1
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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.

• International Journal of Naval Architecture and Ocean Engineering
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• v.7 no.4
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• pp.720-738
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• 2015

This study examined the dynamic response of a subsea pipeline under an impact load to determine the effect of the seabed soil. A laboratory-scale soil-based pipeline impact test was carried out to investigate the pipeline deformation/strain as well as the interaction with the soil-pipeline. In addition, an impact test was simulated using the finite element technique, and the calculated strain was compared with the experimental results. During the simulation, the pipeline was described based on an elasto-plastic analysis, and the soil was modeled using the Mohr-Coulomb failure criterion. The results obtained were compared with ASME D31.8, and the differences between the analysis results and the rules were specifically investigated. Modified ASME formulae were proposed to calculate the precise structural behavior of a subsea pipeline under an impact load when considering sand- and clay-based seabed soils.

• International Journal of Naval Architecture and Ocean Engineering
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• v.9 no.5
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• pp.509-524
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• 2017

Experiments and a numerical simulation were conducted to investigate the deformation and impact behavior of a corroded pipe, as corrosion, fatigue, and collision phenomena frequently occur in subsea pipelines. This study focuses on the deformation of the corrosion region and the variation of the geometry of the pipe under impact loading. The experiments for the impact behavior of the corroded pipe were performed using an impact test apparatus to validate the results of the simulation. In addition, during the simulation, material tests were performed, and the results were applied to the simulation. The ABAQUS explicit finite element analysis program was used to perform numerical simulations for the parametric study, as well as experiment scenarios, to investigate the effects of defects under impact loading. In addition, the modified ASME B31.8 code formula was proposed to define the damage range for the dented pipe.

• International Journal of Naval Architecture and Ocean Engineering
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• v.6 no.4
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• pp.775-787
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• 2014

Availabilities of subsea Blowout Preventers (BOP) in the Gulf of Mexico Outer Continental Shelf (GoM OCS) is investigated using a Markov method. An updated ${\beta}$ factor model by SINTEF is used for common-cause failures in multiple redundant systems. Coefficient values of failure rates for the Markov model are derived using the ${\beta}$ factor model of the PDS (reliability of computer-based safety systems, Norwegian acronym) method. The blind shear ram preventer system of the subsea BOP components considers a demand rate to reflect reality more. Markov models considering the demand rate for one or two components are introduced. Two data sets are compared at the GoM OCS. The results show that three or four pipe ram preventers give similar availabilities, but redundant blind shear ram preventers or annular preventers enhance the availability of the subsea BOP. Also control systems (PODs) and connectors are contributable components to improve the availability of the subsea BOPs based on sensitivity analysis.

• Journal of Ocean Engineering and Technology
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• v.16 no.5
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• pp.56-60
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• 2002

본 논문은 고온 고압의 유류 수송용 이중배관의 팽창에 대한 해석적 방법에 대한결과고찰과 해석, 그리고 설계시 응용이 가능한 현상에 대해 논하였다. 고온의 유류수송시 온도를 유지할 목적으로 내부의 수송 배관과 외부의 케이싱 배관사이에 절연체가 쓰여진다.이런 이중배관의 팽창을 조사할 수 있는 간단한 해석적 방법이 개발되었다. 본 논문에서는온도의 분포, 입력, 토질의 저항, 수송배관과 케이싱 배관과의 상호작용 등이 고려되어졌으며, 이 해석적 방법은 심해의 이중배관 해석에 적합하게 개발되었다. 계산의 결과 분석에서고온의 영향이 고압보다 현저한 것이 밝혀졌다.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.10
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• pp.1131-1137
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• 2012

Subsea pipelines have been operated with buried depths of 1.2-4m underneath the seabed to prevent buoyancy and external impacts. Therefore, they have to show resistance to both the soil load and the hydrostatic pressure. In this study, the structural integrity of a subsea pipeline subjected to soil load and hydrostatic pressure was evaluated by using FE analyses. A parametric study showed that the internal pressure increased the plastic collapse depth by increasing the resistance to plastic collapse. The hoop stress increased with an increase in the buried depth for the same water depth; however, the hoop stress decreased with an increase in the water depth for the same buried depth.

• Smart Structures and Systems
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• v.15 no.2
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• pp.245-258
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• 2015

A methodology based on distributed fiber optic sensors is proposed to detect the lateral buckling for subsea pipelines in this study. Uncontrolled buckling may lead to serious consequences for the structural integrity of a pipeline. A simple solution to this problem is to control the formation of lateral buckles among the pipeline. This firms the importance of monitoring the occurrence and evolution of pipeline buckling during the installation stage and long-term service cycle. This study reports the experimental investigations on a method for distributed detection of lateral buckling in subsea pipelines with Brillouin fiber optic sensor. The sensing scheme possesses the capability for monitoring the pipeline over the entire structure. The longitudinal strains are monitored by mounting the Brillouin optical time domain analysis (BOTDA) distributed sensors on the outer surface of the pipeline. Then the bending-induced strain is extracted to detect the occurrence and evolution of lateral buckling. Feasibility of the method was validated by using an experimental program on a small scale model pipe. The results demonstrate that the proposed approach is able to detect, in a distributed manner, the onset and progress of lateral buckling in pipelines. The methodology developed in this study provides a promising tool for assessing the structural integrity of subsea pipelines.