• International Journal of Ocean Engineering and Technology Speciallssue:Selected Papers
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• v.3 no.1
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• pp.23-28
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• 2000

A numerical investigation was made to examine characteristics of rectangular pontoon type floating breakwaters in oblique waves. Sway and heave wave exciting forces, roll moment acting on the floating breakwater and three motion reponses decrease as the incident wave angle increases for the most of the wave ranges. There exists a minimum wave transmission coefficient which is a function of wave frequency. In short wave range wave transmission coefficient increases as the incident wave angle increases. In long wave range, however, wave transmission coefficient decreases as the wave incident angle increases.

• Journal of the Korean Society of Industry Convergence
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• v.26 no.6_3
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• pp.1279-1288
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• 2023

Recently, domestic leisure boats have been actively researching eco-friendly product development to enter the global market. Since the hulls of existing leisure boats are mainly made of fiber reinforced plastic (FRP) or aluminum, design techniques for securing structural safety by applying related materials have been mainly studied. In this study, an initial structural design safety assessment of a trimaran pontoon leisure boat with a modular hull structure and eco-friendly high-density polyethylene (HDPE) material was conducted, and sensitivity evaluation and optimization analysis for lightweight design were performed. The initial structural design safety assessment was carried out by creating a finite element analysis model and applying the loading conditions specified in the ship classification regulation to check whether the specified allowable stresses are satisfied. For the sensitivity evaluation, the influence of stress and weight of each hull structural member was evaluated using the orthogonal array design of experiments method, and an approximate model based on the response surface method was generated using the results of the design of experiments. The optimization analysis set the thickness of the hull structural members as the design variable and considered the optimal design formulation to minimize the weight while satisfying the allowable stress. The algorithm of the optimization analysis applied the Gradient-population Based Optimizer (GBO) to improve the accuracy of the optimal solution convergence while reducing the numerical cost. Through this study, the optimal design of a newly developed eco-friendly trimaran pontoon leisure boat with a weight reduction of 10% was presented.

• Journal of the Society of Naval Architects of Korea
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• v.35 no.2
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• pp.38-50
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• 1998

In order to understand the characteristics of floating breakwaters we planned series of experimental and numerical investigations and completed the first stage which is the experiment with fred pontoons near the free surface. As controlling parameters the draft and breadth of pontoon were varied and the wave frequency and steepness were also varied. Wave transmission and forces exiled on the breakwater were experimentally investigated and compared with the results computed based on linear potential theory. Discussions made are on the effect of draft and wave length on the wave transmission and force in fixed pontoon case. The predicted and measured results show quantitatively good agreement both in forces and transmission coefficient. The effect of separation distance between two pontoons on the wave transmission and force in array case is also examined.

• Smart Structures and Systems
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• v.9 no.1
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• pp.71-104
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• 2012

In this research, a typical tension-leg type of floating platform incorporated with an innovative concept of underwater tuned liquid column damper system (UWTLCD) is studied. The purpose of this study is to improve the structural safety by means of mitigating the wave induced vibrations and stresses on the offshore floating Tension Leg Platform (TLP) system. Based on some encouraging results from a previous study, where a Tuned Liquid Column Damper (TLCD) system was employed in a floating platform system to reduce the vibration of the main structure, in this study, the traditional TLCD system was modified and tested. Firstly, the orifice-tube was replaced with a smaller horizontal tube and secondly, the TLCD system was combined into the pontoon system under the platform. The modification creates a multipurpose pontoon system associated with vibration mitigation function. On the other hand, the UWTLCD that is installed underwater instead would not occupy any additional space on the platform and yet provide buoyancy to the system. Experimental tests were performed for the mitigation effect and parameters besides the wave conditions, such as pontoon draught and liquid-length in the TLCD were taken into account in the test. It is found that the accurately tuned UWTLCD system could effectively reduce the dynamic response of the offshore platform system in terms of both the vibration amplitude and tensile forces measured in the mooring tethers.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.38 no.5
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• pp.316-322
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• 2005

In order to develop a floating breakwater, which can efficiently control long period waves, vertical plates are attached in pontoon. Wave control and dynamic behaviors of the newly developed vertical plates type are verified from numerical analysis and hydraulic experiment. As a result, for the wave control and energy dissipation, the newly developed vertical plates type is more efficient than the conventional pontoon type. For the floating body motion, the wave transmission, depending on incident wave period, is decreased at the natural frequency. Dimensionless drift distance has similar trend of the reflection rate of wave transformation near natural frequency except maximum and minimum values. Dimensionless maximum tension is 17 percent of the weight of floating breakwater in case of the conventional pontoon type and 18 percent or 14 percent in case of the newly developed vertical plates type. Thus, it is shown that the wave control is improved by the vertical plates type. In addition, by adjusting the interval of the front and back vertical plate, we would control proper wave control.

• Proceedings of the Korean Society of Coastal and Ocean Engineers Conference
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• 2004.08a
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• pp.150-159
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• 2004

In the present paper, the hydrodynamics properties of a Rahmen type flexible porous breakwater with dual fixed-pontoon system interacting with obliquely or normally incident small amplitude waves are numerically investigated. This system is composed of dual vertical porous membranes hinged a the side edges of dual fixed pontoons, and a submerged horizontal membrane that both ends are hinged at the steel frames mounted pontoons. The dual vertical membranes are extended downward and hinged at bottom steal frame fixed into seabed. The wave blocking and dissipation mechanism and its effects of permeability, Rahmen type membrane and pontoon geometry, pre-tensions on membranes, relative dimensionless wave number, and incident wave headings are thoroughly examined.

• Journal of Ocean Engineering and Technology
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• v.19 no.2 s.63
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• pp.1-11
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• 2005

In the present paper, the hydrodynamic properties of a Rahmen type flexible porous breakwater with dual fixed pontoon system interacting with obliquely or normally incident small amplitude waves are numerically investigated. This system is composed of dual vertical porous membranes hinged at the side edges of dual fixed pontoons, and a submerged horizontal membrane that both ends are hinged at the steel frames mounted pontoons. The dual vertical membranes are extended downward and hinged at bottom steal frame fixed into seabed. The wave blocking and dissipation mechanism and its effects of permeability, Rahmen type membrane and pontoon geometry, pretensions on membranes, relative dimensionless wave number, and incident wave headings are thoroughly examined.

• International Journal of Naval Architecture and Ocean Engineering
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• v.7 no.6
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• pp.951-963
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• 2015

The water wave characteristics of Bragg reflections from a train of fixed floating pontoon breakwaters was studied numerically. A numerical model of boundary discretization type was developed to calculate the wave field. The model was verified by comparing to analytical data in literature and good agreements were achieved. Series of parametric studies were conducted systematically to investigate the dependence of the reflected coefficients by the Bragg scattering on the design variables, including the spacing between the breakwaters, the total number of installed breakwaters, the draft and width do the breakwater, and wave length. Certain wave characteristics of the Bragg reflections were observed and discussed in details which might be of help for practical engineering applications in shoreline protection from incident waves.

• Ocean Systems Engineering
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• v.14 no.2
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• pp.115-139
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• 2024

In this study, numerical study of a long, straight, side-anchored floating bridge with discrete pontoons subjected to combined earthquakes and waves is conducted. Ground motions with magnitude corresponding to 200 YRP (years return period) earthquake in South Korea are generated based on the spectral matching method from a past earthquake record in California. Several sensitivity studies are carried out for bridge end condition, for different site classes (hard rock S1 and soft and deep soil S5), and for three different excitations (earthquake only, wave only, and earthquake-wave combined). Bridge and pontoon motions, bending moments along the bridge, and mooring tensions are systematically examined through coupled time-domain simulations by commercial program OrcaFlex. The numerical results show that the impact of earthquakes on floating bridges is still of importance especially for soft soil although ground motions are less directly applied to the structure than fixed bridges.

• Proceedings of the Korea Water Resources Association Conference
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• 2005.09b
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• pp.900-901
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• 2005