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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
> Journal Vol & Issue
Ocean Systems Engineering
Journal Basic Information
Journal DOI :
Editor in Chief :
Young S. Shin
Volume & Issues
Volume 4, Issue 4 - Dec 2014
Volume 4, Issue 3 - Sep 2014
Volume 4, Issue 2 - Jun 2014
Volume 4, Issue 1 - Mar 2014
Selecting the target year
Effect of plate slope and water jetting on the penetration depth of a jack-up spud-can for surficial sands
Han, Dong-Seop ; Kim, Seung-Jun ; Kim, Moo-Hyun ;
Ocean Systems Engineering, volume 4, issue 4, 2014, Pages 263~278
DOI : 10.12989/ose.2014.4.4.263
The spudcan requires the suitable design considering the soil, platform, and environmental conditions. Its shape needs to be designed to secure sufficient reaction of soil so that it can prevent overturning accidents. Its shape also has to minimize the installation and extraction time. Even in the same soil condition, the reaction of soil may be different depending on the shape of spud can, mainly the slope of top and bottom plates. Therefore, in this study, the relation between the slope of plates and the reaction of soil with and without water jetting is analyzed to better understand their interactions and correlations. For the investigation, a wind turbine installation jack-up rig (WTIJ) is selected as the target platform and the Gulf of Mexico is considered as the target site. A multi layered (sand overlying two clays) soil profile is applied as the assumed soil condition and the soil-structure interaction (SSI) analysis is performed by using ANSYS to analyze the effect of the slope change of the bottom plate and water jetting on the reaction of soil. This kind of investigation and simulation is needed to develop optimal and smart spudcan with water-jetting control in the future.
Three dimensional finite element analysis of 4 inch smart flange on offshore pipeline
Moghaddam, Ali Shaghaghi ; Mohammadnia, Saeid ;
Ocean Systems Engineering, volume 4, issue 4, 2014, Pages 279~291
DOI : 10.12989/ose.2014.4.4.279
Smart flanges are used for pipeline and riser repair in subsea. In a typical case in the gas export pipeline project, the end cap bolts of a 4inch smart flange were broken during operation, and in turn leakage occurred. This work presents the detail of three dimensional finite element analysis of the smart flange to support the observed end cap bolts failure. From finite element analysis it turns out that in the presence of external bending moment, an uneven contact distribution is present between seal and end cap, which in turn changes the uniform load distribution on bolts and threaten the integrity of bolts. On the other hand, 3D finite element analysis of interaction between pipeline and seabed is presented by means of Abaqus to explore the distribution of bending moment along the pipeline route. It is found that lateral buckling occurs in the pipeline which introduces large bending moment.
Non-Gaussian analysis methods for planing craft motion
Somayajula, Abhilash ; Falzarano, Jeffrey M. ;
Ocean Systems Engineering, volume 4, issue 4, 2014, Pages 293~308
DOI : 10.12989/ose.2014.4.4.293
Unlike the traditional displacement type vessels, the high speed planing crafts are supported by the lift forces which are highly non-linear. This non-linear phenomenon causes their motions in an irregular seaway to be non-Gaussian. In general, it may not be possible to express the probability distribution of such processes by an analytical formula. Also the process might not be stationary or ergodic in which case the statistical behavior of the motion to be constantly changing with time. Therefore the extreme values of such a process can no longer be calculated using the analytical formulae applicable to Gaussian processes. Since closed form analytical solutions do not exist, recourse is taken to fitting a distribution to the data and estimating the statistical properties of the process from this fitted probability distribution. The peaks over threshold analysis and fitting of the Generalized Pareto Distribution are explored in this paper as an alternative to Weibull, Generalized Gamma and Rayleigh distributions in predicting the short term extreme value of a random process.
Stress and strain behavior investigation on a scale model geotextile tube for Saemangeum dike project
Kim, Hyeong-Joo ; Lee, Kwang-Hyung ; Jo, Sung-Kyeong ; Jamin, Jay C. ;
Ocean Systems Engineering, volume 4, issue 4, 2014, Pages 309~325
DOI : 10.12989/ose.2014.4.4.309
Geotextile tubes are basically a huge sack filled with sand or dredged soil. Geotextile tubes are made of permeable woven or non-woven synthetic fibers (i.e., polyester or PET and polypropylene or PP). The geotextile tubes` performances in strength, dewatering, retaining solid particles and stacked stability have been studied extensively in the past. However, only little research has been done in the observation of the deformation behavior of geotextile tubes. In this paper, a large-scale apparatus for geotextile tube experiment is introduced. The apparatus is equipped with a slurry mixing station, pumping and delivery station, an observation station and a data station. For this study the large-scale apparatus was utilized in the studies regarding the stresses on the geotextile and the deformation behavior of the geotextile tube. Model tests were conducted using a custom-made woven geotextile tubes. Load cells placed at the inner belly of the geotextile tube to monitor the total soil pressure. Strain gauges were also placed on the outer skin of the tube to measure the geotextile strain. The pressure and strain sensors are attached to a data logger that sends the collected data to a desktop computer. The experiment results showed that the maximum geotextile strain occurs at the sides of the tube and the soil pressure distribution varies at each geotextile tube section.
Tethers tension force effect in the response of a squared tension leg platform subjected to ocean waves
El-gamal, Amr R. ; Essa, Ashraf ; Ismail, Ayman ;
Ocean Systems Engineering, volume 4, issue 4, 2014, Pages 327~342
DOI : 10.12989/ose.2014.4.4.327
The tension leg platform (TLP) is one of the compliant structures which are generally used for deep water oil exploration. With respect to the horizontal degrees of freedom, it behaves like a floating structure moored by vertical tethers which are pretension due to the excess buoyancy of the platform, whereas with respect to the vertical degrees of freedom, it is stiff and resembles a fixed structure and is not allowed to float freely. In the current study, a numerical study for square TLP using modified Morison equation was carried out in the time domain with water particle kinematics using Airy`s linear wave theory to investigate the effect of changing the tether tension force on the stiffness matrix of TLP`s, the dynamic behavior of TLP`s; and on the fatigue stresses in the cables. The effect was investigated for different parameters of the hydrodynamic forces such as wave periods, and wave heights. The numerical study takes into consideration the effect of coupling between various degrees of freedom. The stiffness of the TLP was derived from a combination of hydrostatic restoring forces and restoring forces due to cables. Nonlinear equation was solved using Newmark`s beta integration method. Only uni-directional waves in the surge direction was considered in the analysis. It was found that for short wave periods (i.e., 10 sec.), the surge response consisted of small amplitude oscillations about a displaced position that is significantly dependent on tether tension force, wave height; whereas for longer wave periods, the surge response showed high amplitude oscillations that is significantly dependent on wave height, and that special attention should be given to tethers fatigue because of their high tensile static and dynamic stress.