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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Journal of Ocean Engineering and Technology
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Journal DOI :
Korean Society of Ocean Engineers
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Volume & Issues
Volume 20, Issue 6 - Dec 2006
Volume 20, Issue 5 - Oct 2006
Volume 20, Issue 4 - Aug 2006
Volume 20, Issue 3 - Jun 2006
Volume 20, Issue 2 - Apr 2006
Volume 20, Issue 1 - Feb 2006
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Comparison between Field Test and Numerical Analysis for a Jacket Platform in Bohai Bay, China
Yang He-Zhen ; Park Han-Il ; Choi Kyung-Sik ; Li Hua-Jun ;
Journal of Ocean Engineering and Technology, volume 20, issue 2, 2006, Pages 1~7
This paper, presents a comparison between numerical analysis and field test on a real offshore platform in Bohai Bay, China. This platform is a steel jacket offshore platform with vertical piles. The field testing under wave-induced force and wind force etc. was conducted, in order to obtain the dynamic parameters of the structure, including the frequencies of the jacket platform, as well as the corresponding damping ratios and mode shapes. The natural excitation technology (NexT) combined with eigensystem realization algorithm (ERA) and the peak picking (PP) method in frequency domain are carried out for modal parameter indentification under operational conditions. The three-dimeansional finite element model (FEM) is constructed by ANSYS and analytical modal analysis is performed to generate modal parameters. The analytical results were compared with experimental results. A good agreement was achieved between the finite element and analysis and field test results. It is further demonstrated that the numerical and experimental modal analysis provide a comprehensive study on the dynamic properties of the jacket platform. According to the analysis results, the modal parameters identification under ambient excitation can calibrate finite element model of the jacket platform structures, or can be used for the structural health monitoring system.
Guided-Waves-Based Mortar-Filled Steel Pipe Inspection Using EMAT End Wavelet Transform
Na Won-Bae ; Kim Jeong-Tae ; Ryu Yeon-Sun ;
Journal of Ocean Engineering and Technology, volume 20, issue 2, 2006, Pages 8~15
Guided-waves-based mortar-filled steel pipe inspection is carried out through using EMAT (Electro magnetic acoustic transducer) and wavelet transform. Possibly existing anomalies such as separation (or void) and inclusion are made in the fabricated mortar-fled steel pipes: these anomalies are infected. Since guided waves have the long range inspection capability, EMAT has its own advantages over the conventional PZT (Piezoelectric zirconate titanate), and wavelet transform gives the multi-resolution on time-frequency domain results, the suggested technique gives an alternative way for inspecting mortar-filled steel pipes, which are popularly used for supporting marine structures such as piers, wharfs, moles, and dolphins. Through this study, it is show that the suggested technique is promising for detecting the amounts of separations and inclusions.
Influence of Removed Web Members in Shaping Formation for Hypar Space Truss
Kim Jin-Woo ; Kwon Min-Ho ; Lee Yong-Hee ;
Journal of Ocean Engineering and Technology, volume 20, issue 2, 2006, Pages 16~21
This paper discusses the behavior of post-tensioned and shaped hypar space truss, with consideration of the influence of removing some web members. Hypar space truss is post-tensioned at the bottom chords of one diagonal on the ground; the essential behavior characteristic of shape formation is discussed by using a small-scale test model. Results of experiments and nonlinear finite-element analysis indicate that a planar, rectangular- arranged structure can be deformed to a predicted hyper shape, by the proposed shape formation method. Also the feasibility of the proposed method for furnishing of a hypar shaped face truss has been presented, under the condition of both non-removed and partially removed web members. It follows that a nonlinear finite element analysis method can be used in predicting the behavior of the space shape and the post-tensioning force in sharing of hypar space truss. Further, in comparison to the other cases, the results of test and analysis show that the active diagonal shaping in the non-removed web members and passive diagonal shaping of partially removed web members are in relatively good agreement.
A Study on Motion and Wave Drift Force of a BBDB Type OWC Wave Energy Device
Kim Jin-Ha ; Lew Jae-Moon ; Hong Do-Chun ; Hong Seok-Won ;
Journal of Ocean Engineering and Technology, volume 20, issue 2, 2006, Pages 22~28
The motion and wave drift forces of floating BBDB (backward-bent duct buoy) wave energy absorbers in regular waves are calculated, taking account of the oscillating surface-pressure due to the pressure drop in the air chamber above the oscillating water column, within the scope of the linear wave theory. A series of model tests has been conducted in order to order to verify the motion and time mean wave drift force reponses in regular waves at the ocean engineering basin, MOERI/KORDI. The pneumatic damping through an orifice-type duct for the BBDB wave energy device are deducted from experimental research. Numerical simulation for motion and drift force responses of the BBDB wave energy device, considering pneumatic damping coefficients, has been carried out, and the results are compared with those of model tests.
Analysis of Flow Around Multi-Circular Cylinders Using a Numerical Model
Lee Sang-Hwa ; Park Jung-Ho ;
Journal of Ocean Engineering and Technology, volume 20, issue 2, 2006, Pages 29~35
The flow patterns around multi-circular cylinders are studies, in order to obtain a global view on the structure of wave control and circulation of sea flow in coastal region. The flow force depends upon the vortex shedding exerted on the structure, especially how the vortex shedding affects the erosion when the structure sets on the sand bottom. Therefore, it is necessary that the flow pattern be hocked. In order to simulate the flow around multi-circular cylinders, the CFX and FLUENT of the computational fluid dynamics (CFD) program were used and compared with the experimental results of the flow visualization installation. The phenomena of flow around the multi-cylinders will be applied to fundamental data for predicting the flow force acting against the structure, erosion and sedimentation around cylinders in arrangement.
Wave-Induced Motions of a Floating Body in a Harbour
Lee Ho-Young ; Kwak Young-Ki ; Park Jong-Hwan ;
Journal of Ocean Engineering and Technology, volume 20, issue 2, 2006, Pages 36~40
As large waves enter a harbor, during their propagation, the motions a floating body are large and if may even be damaged by waves. This phenomenon may be caused by harbor resonance, resulting from large motion at low wave frequency, which is close to the natural frequency of a vessel. In order to calculate the motion of a floating body in a harbor, it is necessary to use the wave forces containing the body-harbor interference. The simulation program to predict the motions of a floating body by waves in a harbor is developed, and this program is based on the method of velocity potential contiuation method proposed by Ijima and Yoshida The calculated results are shown by the variation of wave frequency, wave angle, and the position of a floating body.
A Study on Characteristics of Repair Welding for Cast Iron Part of Diesel Engine for Ship
Kim Jin-Gyeong ; Kang Myung-Shin ; Kim Young-Sik ;
Journal of Ocean Engineering and Technology, volume 20, issue 2, 2006, Pages 41~45
Arc welding is sometimes used to repair damaged cast iron parts in diesel engine for driving n ship. In this case cold arc welding is good for saving the time and results in good repairing. But if some difference in hardness on welding zones made with AWS E Ni-CI and NiFe-CI happen, repaired parts would be cracked in a short. In order to overcome this default, the study is performed on varying preheating temperature of welding parts, selecting welding rod and welding work way. The result will be used on ship's working shop.
An Experimental Study on the Moonpool Characteristics of a Cleaning Ship for Ocean Environment Purification
Kim Do-Jung ; Park Je-Woong ; Kim Ju-Nam ; Jeong Uh-Chul ;
Journal of Ocean Engineering and Technology, volume 20, issue 2, 2006, Pages 46~51
Moonpool characteristics of a cleaning skip related with the performance of a skip are experimentally investigated. Resistance performances of the ship and flow patterns in the moonpool are observed, in order to determine the effect of different shaped moonpool. The ways to reduce ship pithing motion caused by force in the moonpool are examined. Experimental results, using a scale model of cleaning ship with moonpool, show that the step arranged in tier under water leads to significant improvements in performance, such us resistance and ship pithing motion. Depending upon the shape of step in the moonpool, the results indicate that the increment of resistance performance may be up to 35%, especially in the case of no step or high step.
Durability Test on E-Glass Fiber Reinforced Composites of Strand Type in Specific Environment
Lee Seong-Ryul ; Kim By-An ; Moon Chang-Kwon ;
Journal of Ocean Engineering and Technology, volume 20, issue 2, 2006, Pages 52~58
The effect of various environmental conditions on the durability of E-glass fiber/vinylester resin composites have been investigated using the tensile test specimen of strand type. It was found that the durability test method performed by the stand type specimen was more convenient and reliable than other conventional test method. The weight gains increased with the immersion time in both water and alkaline solution, and the Weight gains at
. were much bigger than those at
in both conditions. The tensile strength decreased with the pass of immersion time in all aqueous solution, and the tensile strength at
in alkaline solution decreased very steeply at beginning of immersion time. The decrement of tensile strength according to the immersion time in various environmental conditions was mainly caused by the degradation of interface and the damage of glass fiber surface.
A Study on the Measurement of Steel Corrosion in Mortar by TEM Method
Lee Sang-Ho ; Han Jeong-Seb ;
Journal of Ocean Engineering and Technology, volume 20, issue 2, 2006, Pages 59~65
Steel, as a reinforcing mechanism in concrete, provides the tensile strength that is lacking in concrete, alone, and the high alkaline environment (pH 12.5) in concrete offers satisfactory protection against most corrosion of the steel. However, the corrosion of reinforcing steel in concrete can occur by chloride attack or carbonation, and it can cause a loss of integrity a section and concrete failure through cracking and spalling. In this study, a transient electro magnetic method (TEM) of a nondestructive technique is adapted to study the measuring method of steel corrosion in mortar. The sensor was made of an enameled wire, with a diameter of 0.25mm and anacril. He sensor configuration used was a coincident loop type. The secondary electro motive force (2nd EMF) was measured with SIROTEMIII, which equipped the accelerator. The accelerator allowsthe transmitter to turn off approximately
times faster than normal. The high-resolution time series, used for very shallow or a high resistivity investigation was selected. After steels were corroded by the salt spray, during 4, 8, 15 and 25 days, they were embedded in mortar. The content results acquired in this study are as follows. The variation of the secondary electro motive force (2nd EMF) was shown by the change of steel surface with different corrosion time steel. It was confirmed that measurement of steel corrosion in mortar by a transient electro-magnetic method (TEM) can be possible.
Hull Form Design of Catamaran Type Dredging Vessel Using Model Test and Numerical Simulation
Lee Young-Gill ; Son Choong-Yul ; Jeong Uh-Cheul ; Kang Dae-Sun ; Jeong Kwang-Leol ; Kim Do-Jung ;
Journal of Ocean Engineering and Technology, volume 20, issue 2, 2006, Pages 66~71
To develope a hull form of catamaran type dredging vessel, resistance characteristics is investigated to find the interaction effect of waves between the two hulls. Re fore body shape is simplified as two dimensional wedge shape for the maintenance and disassembly/assembly. Based on MAC method, numerical simulation is performed in staggered variable mesh system. Re conservation form of Euler equations and continuity equation are applied as governing equations. To verify numerical methods, the wive patterns along the hull surface are compared with the results of model tests. This study is performed as varying wedge shape of the bow and the distance between the two hulls. The wave interaction between two hulls are observed to investigate the relation the resistance performance and the flow characteristics. Suitable hull form and distance between two hulls are discussed.