• Journal of the Korean Society of Marine Environment & Safety
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• v.20 no.6
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• pp.738-745
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• 2014

In this paper, It is performing to the elastic and elasto-plastic large deformation series analysis using a numerical method for the initial deflection effect of the aluminum alloy rectangular plate in the elasto-plastic loading area patch loading size. It is assumed a boundary condition to be a simply supported condition and consider the initial deflection amplitude, aspect ratio. It examined the critical elastic buckling load and post-buckling behaviour of aluminium alloy A6082-T6 rectangular plate. It used a commercial program for the elastic and elasto-plastic deformation series analysis. If the initial deflection amplitude is smaller, the in-plane rigidity with increasing to load is reduced from the start and occurs significantly more increasing the amplitude. More higher the aspect ratio, the initial yield strength is gradually decreased, and the plate thickness thicker and occurs larger than the thin walled plate a reduction ratio of the initial yield strength of the patch loading size as 0.5.

• International Journal of Naval Architecture and Ocean Engineering
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• v.12 no.1
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• pp.199-212
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• 2020

A large percentage of maritime accidents in coastal seas are related to small fishing vessels. In order to investigate causes of maritime accidents, it is often necessary to carry out dynamic simulations for the estimation of trajectories and motions of vessels. Initial conditions of vessels such as main dimensions, loading conditions and hydrostatic properties are required for the accurate simulations. Small fishing vessels usually have few records of hydrostatic properties during their fishing operations. Therefore, in this study, estimation procedures for hydrostatic properties of small fishing vessels are proposed. At first, hull form characteristics of Korean small fishing vessels are investigated. Most of vessels have hard-chines and centerline skegs, they have similar hull forms. Bonjean curves of several small fishing vessels whose gross tonnages are below 10 tons are normalized with vessel breadths and depths. Representative bonjean curves are derived from normalized bonjean curves, and a representative hull plan is obtained as well. If the vessel loading conditions such as total weights and centers of gravity are given, fore and aft drafts can be calculated by using the representative bonjean curves with the constraint that weights and buoyancies are in equilibrium. Metacentric heights are also estimated by using the representative hull plan. Drafts and metacentric heights estimated by proposed iterative estimation procedures are compared with actual vessel data, estimated values are in good agreements with actual values. In addition, normalized fore and aft drafts, metacentric heights of vessels can be formulated as the linear functions of normalized total weights and centers of gravity. Empirical formulas of drafts and metacentric heights are proposed, and it is confirmed that the empirical formulas also provide reasonable results, which are similar to the results by iterative estimation procedures with representative bonjean curves and hull plan.

• Aerospace Engineering and Technology
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• v.9 no.2
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• pp.51-56
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• 2010

There are two main software in COMS ground station at the normal mode operation - stationkeeping and wheel off-loading. In this paper, ground software validation test for wheel off-loading is summarized and described. The wheel off-loading was performed the design change from E3000 heritage and analyzed. The wheel off-loading of ground software has two part; one is wheel off-loading management for parameters change at the thruster set switching time and the other is wheel off-loading set-point being sent to satellite for the reference momentum.

• Proceedings of the KSRS Conference
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• v.2
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• pp.756-759
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• 2006

The ocean tide loading (OTL) is an important factor for the GPS positioning, especially in the height direction. The shorter of the distance to the ocean, the larger of the error by the OTL. The influence will be changed when we measure in different place and the order of magnitude is from few centimeters to ten centimeters. In this study, more than ten kinds of the OTL models were collected and applied on the GPS static relative positioning in Taiwan. The GPS observations including five stations were obtained from Nov. 9, 2004 to Feb. 23, 2005 and we used the Bernese GPS software to execute the data processing. In this period, the average amplitudes of the 3-D coordinates are as follows: N is 0.4 cm, E is 0.7 cm, h is 1.8 cm at Kinmen station; N is 0.7 cm, E is 1.3 cm, h is 2.3 cm at Lanyu station; N is 0.5 cm, E is 0.7 cm, h is 2.0 cm at Matsu station; N is 0.6 cm, E is 0.6 cm, h is 2.0 cm at Penghu station and N is 0.5 cm, E is 1.2 cm, h is 1.7 cm at Hsinchu station. Moreover, we will analyze the advantage and disadvantage of every kind of the OTL models in different environments to offer some information to the GPS users and enhance the precision of the GPS positioning.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.9 no.4
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• pp.165-175
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• 1997

This study qualitatively reviewed effect of the height of loading and the ratio of penetration on. the characteristics of deformation of cellular bulkhead by performing a model test of embedded steel plate cellular bulkhead which had different loading height and penetration ratio. And we also examined the effect of the loading height upon the shear behavior by performing two-dimensional model test making use of aluminum rods for a filler. Besides, test results and theoretical values based on Hansen's earth pressure theory were compared and reviewed. In consequence, it was ascertained that the yield moment of cells depended on the height of loading and the ratio of penetration, and the slip surface was located on the lower area of a cell interior according as the height of loading becomes lower. The theoretical consideration which was based on the theory of earth pressure proposed by Hansen revealed that the test results accorded with the theoretical values to some degree, and the same results were derived about the location change of the slip surface.

• Journal of Advanced Research in Ocean Engineering
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• v.1 no.4
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• pp.239-251
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• 2015

In this study, a spectral fatigue analysis was performed for the topside structure of an offshore floating vessel. The topside structure was idealized using beam elements in the SACS program. The fatigue analysis was carried out considering the wave and wind loads separately. For the wave-induced fatigue damage calculation, motion RAOs calculated from a direct wave load analysis and regular waves with different periods and unit wave heights were utilized. Then, the member end force transfer functions were generated covering all the loading conditions. Stress response transfer functions at each joint were produced using the specified SCFs and member end force transfer functions. fatigue damages were calculated using the obtained stress ranges, S-N curve, wave spectrum, heading probability of each loading condition, and their corresponding occurrences in the wave scatter diagrams. For the wind induced fatigue damage calculation, a dynamic wind spectral fatigue analysis was performed. First, a dynamic natural frequency analysis was performed to generate the structural dynamic characteristics, including the eigenvalues (natural frequencies), eigenvectors (mode shapes), and mass matrix. To adequately represent the dynamic characteristic of the structure, the number of modes was appropriately determined in the lateral direction. Second, a wind spectral fatigue analysis was performed using the mode shapes and mass data obtained from the previous results. In this analysis, the Weibull distribution of the wind speed occurrence, occurrence probability in each direction, damping coefficient, S-N curves, and SCF of each joint were defined and used. In particular, the wind fatigue damages were calculated under the assumption that the stress ranges followed a Rayleigh distribution. The total fatigue damages were calculated from the combination with wind and wave fatigue damages according to the DNV rule.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.36 no.5
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• pp.343-353
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• 2018

Ocean tides in Antarctica are not well constrained mostly due to the lack of tidal observations. Especially, tides underneath and around ice shelves are uncertain. InSAR (Interferometric Synthetic Aperture Radar) data has been used to observe ice shelf movements primarily caused by ocean tides. Here, we demonstrate that it is possible to estimate tidal constituents underneath the Sulzberger ice shelf, West Antarctica, solely using ERS-1/2 tandem mission DInSAR (differential InSAR) observations. In addition, the tidal constituents can be estimated in a high-resolution (~200 m) grid which is beyond any tidal model resolution. We assume that InSAR observed ocean tidal heights can be derived after correcting the InSAR data for the effect of atmospheric loading using the inverse barometric effect, solid earth tides, and ocean tide loading. The ERS (European Remote Sensing) tandem orbit configuration of a 1-day separation between SAR data takes diminishes the sensitivity to major tidal constituents including $K_1$ and $S_2$. Here, the dominant tidal constituent $O_1$ is estimated using 8 differential interferograms underneath the Sulzberger ice shelf. The resulting tidal constituent is compared with a contemporary regional tide model (CATS2008a) and a global tide model (TPXO7.1). The InSAR estimated tidal amplitude agrees well with both models with RMS (root-mean-square) differences of < 2.2 cm and the phase estimate corroborating both tide models to within $8^{\circ}$. We conclude that fine spatial scale (~200 m) Antarctic ice shelf ocean tide determination is feasible for dominant constituents using C-band ERS-1/2 tandem mission InSAR.

• Journal of Astronomy and Space Sciences
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• v.24 no.3
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• pp.249-260
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• 2007

The crustal deformation due to Ocean Tide Loading (OTL) in the Korean peninsula reaches up to ${\sim}3cm$ in the vertical direction. Considering that the achievable positioning accuracy of current state-of-the-art space geodesy technologies is at the several millimeter level, the centimeter-level OTL effect should be precisely modelled and corrected for. This study begins with comparison of ocean tide models and validation of OTL-prediction softwares. Different ocean tide models caused about ${\sim}6mm$ RMS differences in the vertical deformation in the Kyung-gi Bay area. When we analyzed the OTL displacements in the Seoul, Ulsan, and Seogwipo areas where three VLBI observatories are planned to be installed, the maximum displacement of ${\sim}3.5cm$ was predicted in the Seogwipo area and ${\sim}2cm$ in the Seoul and Ulsan areas. When the OTL corrections were not applied in the GPS data processing, the OTL effect propagates into the Zenith Wet Delay (ZWD) estimates, and the scale factor between ZWD differences and OTL displacements was 3.72.

• Journal of Ocean Engineering and Technology
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• v.19 no.1 s.62
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• pp.95-99
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• 2005

This paper presents the optimum design of cylindrical shell under external pressure loading. Two kinds of material, Al7075-T6, Ti-6Al-4V, are considered. For each material, the design variable is a thickness of the unstiffened parallel middle body shell, and the state variable, constraint, is hoop stress and the object .function is total weight of the cylindrical shell. Optimization is performed by conventional FE Program, ANSYS. In addition, buckling analysis is performed for the middle body of the cylindrical shell. Finally, we calculates the payload of the cylindrical shell to keep neutral buoyancy with optimized thickness in deep-sea applications.

• Structural Engineering and Mechanics
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• v.77 no.6
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• pp.809-817
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• 2021

In this study, the dynamic behavior of a three-span hybrid continuous arch bridge under vehicle loading is investigated. The natural vibration characteristics of the bridge were analyzed through pulsation test. In the dynamic loading test, the vibrations of the bridge under different truck speeds and different pavement conditions were tested, and time histories of deflection and acceleration of the bridge were measured. Based on the dynamic loading test, the impact coefficient was analyzed. The results indicate that the pavement smoothness had more impacts on the vibration of the bridge than the truck's speed. The vertical damping of the bridge under the excitation of the trucks is larger than the transverse damping. Resonance occurs at the side span of the bridge under a truck at 10 km/h.