• Journal of Korean Society of Coastal and Ocean Engineers
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• v.31 no.6
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• pp.478-484
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• 2019

The submarine cable for Yongsu wave power plant was cut in 2014 winter. This study investigated the probability of high-wave occurrence exceeding the 50-year return period and the underestimation of armor unit weight used to protect the cable. The observation data from KMA buoy and the hindcast wave data were reviewed to determine the return period of wave height during the winter. In order to investigate the armor unit weight of cable-protection, we calculated the required weight of armor unit using not only Design Standard for Harbor and Fishery Port, but also the previous researches for the wave with large incident angle. As a result, it appeared that the high wave exceeding the 50-year return period did not occur during the winter of 2014 and the armor unit weight of the cable protection was not sufficient to sustain the obliquely incident wave, which induced the cable protection failure.

• International Journal of Naval Architecture and Ocean Engineering
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• v.7 no.6
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• pp.1007-1019
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• 2015

The determination of the required seawall height is usually based on the combination of wind speed (or wave height) and still water level according to a specified return period, e.g., 50-year return period wind speed and 50-year return period still water level. In reality, the two variables are be partially correlated. This may be lead to over-design (costs) of seawall structures. The above-mentioned return period for the design of a seawall depends on economy, society and natural environment in the region. This means a specified risk level of overtopping or damage of a seawall structure is usually allowed. The aim of this paper is to present a conditional risk probability-based seawall height design method which incorporates the correlation of the two variables. For purposes of demonstration, the wind speeds and water levels collected from Jiangsu of China are analyzed. The results show this method can improve seawall height design accuracy.

• Journal of Navigation and Port Research
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• v.30 no.2
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• pp.131-136
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• 2006

Researches on a superstructure built on a floating structure in the shape of pontoon type have begun in recent years. A superstructure responds by wave load and it is important to evaluate its habitability. The purpose of this study is evaluation and investigation of habitability of a superstructure due to wave for 10 year return period. In this study, response analyses of the superstructure built on middle-sized floating structure due to the waves of three cases were carried out by 3-D integration analysis, which means analyzing the calculation model integrated a superstructure with a floating structure, and its habitability was evaluated by the evaluation diagrams. As the result, the habitability differed by each wave condition The use of a superstructure is restricted according to the disposition of a floating structure for incident wave angle.

• Special Issue of the Society of Naval Architects of Korea
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• 2015.09a
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• pp.34-40
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• 2015

The design, procurement and fabrication of FPSO project ordered by Inpex Browse, Ltd. have been currently carried out by DSME(Daewoo Shipbuilding Marine and Engineering Co.). The unit will be installed and operated in the Ichthys field offshore of North-Western Australia and there are the particular design requirements to do with performance on the environment loads corresponding to max. 10,000 years return period wave. Also, the operational life of FPSO has to be over 40 years. With this background, this paper introduces the structural design procedure of crane pedestal foundation operated in north-western Australia offshore. The design of crane pedestal foundation structure is basically based on international design code (i.e. API Spec. 2C), Classification society's rule and project specifications. The design load cases are mainly divided into the crane normal operating conditions and crane stowed conditions according to environment conditions of the offshore with 1-year, 5-year, 10-year, 200-year and 10,000-year return period wave. This design experience for crane pedestal foundation operated in north-western Australia offshore will be useful to do engineering of other offshore crane structures.

• Ocean Systems Engineering
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• v.13 no.3
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• pp.225-245
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• 2023

In the present paper, a numerical and experimental analysis for a wave energy converter under extreme environmental conditions is carried out. After the definition of design waves, including a 100-year return period stochastic sea state and a deterministic rogue wave condition, a numerical analysis using potential theory and a RANS equations solver are compared with experiments carried out at the Seakeeping Basin at the Technical University of Berlin. Results are discussed with special emphasis on the limits of potential theory methods for the evaluation of extreme wave conditions and the use of the presented methodology for early design stages.

• Journal of Korean Society of Disaster and Security
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• v.16 no.4
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• pp.19-31
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• 2023

According to the climate change scenarios, the intensity of typhoons, a major factor in Korea's natural disaster, is expected to increase. The increase in typhoon intensity leads to a rise in wave heights, which is likely to cause large-scale disasters in coastal regions with high populations and building density for dwelling, industry, and tourism. This study, therefore, analyzed observation data of the Donghae ocean data buoy and conducted a numerical model simulation for wave estimations for the typhoon MAYSAK (202009) period, which showed the maximum significant wave height. The boundary conditions for wave simulations were a JMA-MSM wind field and a wind field applying the typhoon central pressure reduction rate in the SSP5-8.5 climate change scenario. As a result of the wave simulations, the wave height in front of the breakwater at Sokcho port was increased by 15.27% from 4.06 m to 4.68 m in the SSP5-8.5 scenario. Furthermore, the return period at the location of 147-2 grid point of deep-sea design wave was calculated to increase at least twice, it is necessary to improve the deep-sea design wave of return period of 50-year, which is prescriptively applied when designing coastal structures.

• Journal of Navigation and Port Research
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• v.45 no.3
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• pp.87-94
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• 2021

The IMO has adopted emission standards that strictly restrict the use of bunker C oil for vessels. Accordingly, research and bunkering pilot projects for LNG fueled ships are being actively carried out, which is expected to substantially reduce environmental pollution. In this study, we have adopted the turret moored Floating LNG Bunkering Terminal (FLBT) designed to receive the LNG from LNGCs and to transfer LNG to LNG bunkering shuttles in ship to ship moored condition. Numerical simulations have been performed with a 1-year return period of wind, wave, and current. Damping values of numerical model were adjusted from the results of model tests to obtain accurate simulation results. The results confirm safe berthing operation during the 1-year return period of environmental condition. Safety depends on the direction of environment, with increasingly stable operation facilitated by the application of heading-control function of FLBT to avoid beam-sea conditions.

• Journal of the Korean Society for Marine Environment & Energy
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• v.15 no.3
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• pp.163-169
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• 2012

In this paper, model test on the Tapdong's revetment at Jeju-si has been conducted to figure out the causes of frequent occurrence of wave overtopping and to suggest the action plan. In the model test, the reflection coefficients were measured according to the change of wave periods for with and without armor stones. Also, the wave overtopping rate and the wave pressures inside revetment structure for 4 types of upper block were estimated for various wave heights and wave periods, which are chosen based on the NE design wave with 50 year return period. It is found that the increase of the upper structure's height and the modification of the curved protruding shape are effective in reducing the overtopping rate.

• International Journal of Naval Architecture and Ocean Engineering
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• v.5 no.2
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• pp.179-187
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• 2013

Floating production storage and offloading (FPSO) facilities are used at most of the offshore oil fields worldwide. FPSO usage is expected to grow as oil fields move to deeper water, thus requiring the reliability and stability of mooring wires and risers in extreme environmental conditions. Except for the case of predictable attack angles of external loadings, FPSO facilities with turret single point mooring (SPM) systems are in general use. There are two types of turret systems: permanent systems and disconnectable turret mooring systems. Extreme environment criteria for permanent moorings are usually based on a 100-year return period event. It is common to use two or three environments including the 100-year wave with associated wind and current, and the 100-year wind with associated waves and current. When fitted with a disconnectable turret mooring system, FPSOs can be used in areas where it is desirable to remove the production unit from the field temporarily to prevent exposure to extreme events such as cyclones or large icebergs. Static and dynamic mooring analyses were performed to evaluate the stability of a spider buoy after disconnection from a turret during cyclone environmental conditions.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.28 no.6
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• pp.375-382
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• 2016

In the present study, the wave hindcasting has been performed, and then the characteristics of storm waves at Gangnueng port was investigated, in which the high waves are observed. Comparing the numerical results with the wave measurements at Gangneung port, Niigata, and Hamada, there were good agreements between them. In particular, the Pearson correlation coefficients of significant wave heights and peak periods at Gangneung port were 0.92 and 0.72, respectively. Then the extreme wave analysis on the significant wave heights was carried out for the estimation of the frequency of storm waves. In this analysis, the storm waves over the threshold were fitted to GPD(Generalized Pareto Distribution). According to this analysis, the return period of the storm wave on February, 24, 2008, one of the large storm waves at Gangneung port, was 8.2 months. Among the computed significant wave heights larger than one-year wave, 58.3% of them were resulted from the storm, while the others were from the typhoon. Additionally, the regression analysis on the waves larger than one-month wave has been conducted, and then the relationship between the computed significant wave heights and the significant wave period, $T_{1/3}=7H_s^{0.25}$ was obtained.