• Journal of Ocean Engineering and Technology
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• v.20 no.3 s.70
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• pp.24-36
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• 2006

This paper investigates wave loads of ships that suffer sinkage due to flood in a compartment caused by damage on the side of the hull. By analyzing ships with various sizesof damage opening, the influence of opening size on ship response is investigated. The motion of the damaged ship is analyzed by using the boundary element method, based on three-dimensional potential theory, considering hydrodynamic pressure in the flooded compartments. The shear forces, bending moments and torsional moments are calculated by the direct integration of the three dimensional hydrodynamic pressure on the outer and inner hulls. A RORO passenger ship with length of 174.8 m is considered in the numerical example, and results for wave loads are discussed.

• Journal of Advanced Research in Ocean Engineering
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• v.4 no.4
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• pp.195-203
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• 2018

The wave impact on ships could cause local damage to the ship's hull, which has been a concerning issue during the ship design process. In recent years, local structural damages of ships caused by slamming loads have been reported by accident; therefore, it is necessary to study the local slamming pressure loads and structural response assessment. In the present study, slamming loads around the ship's bow region in the presence of regular wave have been simulated by RANS equations discretized with a cell-centered finite volume method (FVM) in conjunction with the $k-{\Box}$ turbulence model. The dynamic structural response has been calculated using an explicit FE method. By adding the slamming pressure load of each time step to the finite element model, establishing the reasonable boundary conditions, and considering the material strain-rate effects, the dynamic response prediction of the bow flare structure has been achieved. The results and insights of this study will be helpful to design a container ship that is resistant enough to withstand bow flare slamming loads.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• v.1
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• pp.195-201
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• 2006

The wave load and its influence on the response of offshore structure have been well investigated through the statistical approach based on the linear theory. The linear approach has a limitation to apply the extreme condition such as freak wave, which corresponds to extreme value of wave spectrum. The main topic of present study is to develop an efficient numerical method to predict wave load induced by extreme wave. As a numerical method, finite element method based on variational principle is adopted. The frequency-focusing method is applied to generate the extreme wave in the numerical wave tank. The wave load on the bottom mounted vertical cylinder is investigated. The hydroelastic response of the vertical cylinder is also investigated so as to compare the wave loads with the rigid body case in the extreme wave condition.

• Journal of Navigation and Port Research
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• v.31 no.1 s.117
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• pp.21-27
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• 2007

The wave load and its influence on the response of offshore structure have been well investigated through the statistical approach based on the linear theory. The linear approach has a limitation to apply the extreme condition such as extreme wave, which corresponds to extreme value of wave spectrum. The main topic of present study is to develop an efficient numerical method to predict wave load induced by extreme wave. As a numerical method, finite element method based on variational principle is adopted. The frequency-focusing method is applied to generate the extreme wave in the numerical wave tank. The wave load on the bottom mounted vertical cylinder is investigated. The hydroelastic response of the vertical cylinder is also investigated so as to compare the wave loads with the rigid body case in the extreme wave condition.

• Journal of the Society of Naval Architects of Korea
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• v.49 no.2
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• pp.109-115
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• 2012

Slamming phenomenon may occur when a ship navigates a high sea region, where the response of ship can be expected as elastic behaviour and the resultant wave loads may increase. In this paper, numerical analysis of ship motions and wave loads including momentum slamming was performed using the strip theory with regular waves. In order to analyze the effect of slamming force on the global ship motions, time histories of each mode of displacement and forces were simulated by using Newmark-beta time integration scheme. The added mass and damping coefficients calculated by Lewis form method were compared with the results of given references. For verification of numerical results, the motion RAOs of a S175 containership were calculated as an example of application and time histories of respective displacement and vertical bending moment were compared with the results of ITTC workshop benchmark test.

• Journal of Ocean Engineering and Technology
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• v.29 no.5
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• pp.359-365
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• 2015

A reliability analysis of the gravity-based foundation of anoffshore wind turbine was performed by considering the uncertainties of the design variables, including environmental loads. The limit state functions of the gravity-based foundation were defined using the response limits of the support structures suggested in the DNV standard. The wind load couldbe obtained using the GH_bladed software, and the wave load was calculated using the Morison equation. Then, the extreme distributions of the wind and wave loads were estimated by applying the peak over threshold (POT) method to the wind and wave load data. The probability distribution characteristics of the soil properties were defined with reference to a southwest coast geotechnical survey report. The reliability index was evaluated for each failure mode using a first-order reliability method.

• Ocean Systems Engineering
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• v.8 no.3
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• pp.329-343
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• 2018

The inclination of seabed profile (sloped seabed) is one of the known topographic features which can be observed at different seabed level in the large offshore basin. A mooring system connected between the platform and global seabed is an integral part of the floating structure which tries to keep the floating platform settled in its own position against hostile sea environment. This paper deals with an investigation of the motion responses of an FPSO platform moored on the sloped seabed under the combined action of wave, wind and current loads. A three-dimensional panel discretization method has been used to model the floating body. To introduce the connection of multi-segmented non-linear elastic catenary mooring cables with the sloped seabed, a quasi-static composite catenary model is employed. The model and analysis have been completed by using hydrodynamic diffraction code AQWA. Validation of the numerical model has been successfully carried out with an experimental work published in the latest literature. The analysis procedure in this study has been followed time domain analysis. The study involves an objective oriented investigation on platform motions, in order to identify the effects of the slopped seabed, the action of the wave, wind and current loads and the presence of riser system. In the end, an effective analysis has been performed to identify a stable mooring model in demand of reducing structural responses of the FPSO.

• Journal of the Society of Naval Architects of Korea
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• v.59 no.2
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• pp.89-95
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• 2022

The stability of the existing ships has been evaluated through numerical calculations in the steady-state, but recently the IMO proposed a new stability assessment criteria that the stability is evaluated in the state in which environmental loads from such as waves and wind act like the loads under actual ship operating conditions. In this study, IMO 2nd generation stability assessment method and procedure were summarized for the dead ship condition, and Direct Stability Assessment (DSA) was performed on 13K chemical tanker through basin model test. The model test is performed in the ocean engineering basin to implement wave and wind loads, and environmental conditions for waves were set height and period of the incident wave, considering the regular wave and wind generation range reproducible in the ocean engineering basin. In addition, to consider the effect of wind speed, the Beaufort Scale for wind speed was applied in the model test.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2004.11a
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• pp.96-101
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• 2004

When the wind blows hard, most waves are breaking in sea. Breaking waves occur, exceeding limitation of wave steepness(wave height/wave length=l/7). Because a wave of single angular frequency couldn't generate the breaking phenomena at two dimensional ocean engineering basin, the breaking wave can be generated by the superposition of waves with various angular frequencies. We research how are the particle kinematics in the breaking wave and the magnitude of the breaking wave exciting force. We compare the force in a regular wave which has same specifications(wave height, period and length) as the breaking wave. Also the experimental results of wave exciting force and particle velocity are investigated by comparison on the analytic results using the potential theory.

• International Journal of Highway Engineering
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• v.15 no.3
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• pp.53-63
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• 2013

PURPOSES : This study is to evaluate moisture susceptibility of asphalt mixtures by using non-destructive impact wave and to determine durability so as to decrease the gap between before and after freezing in the future. METHODS : Using non-destructive impact wave, this study is to determine the dynamic modulus of asphalt specimen. Furthermore, the results obtained from two experiment accelerometers are used for the dynamic modulus determination. The dynamic moduli of specimens are compared with those of the freezing-thawing specimens. RESULTS : Test results showed that the dynamic modulus before freezing and thawing environment loads at each temperature dropped about 3.7% after the environmental loads. Furthermore, correlation analysis indicates that transition of dynamic modulus at each point is about 89.59%. CONCLUSIONS: Evaluation of asphalt mixtures using non-destructive impact wave has excellent repeatability and simple equipment for the test. Consequently, the method in the study will be useful for evaluating the characteristics of a various asphalt mixtures.