• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2004.11a
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• pp.159-166
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• 2004

The beach, a margin between the sea and the land, is an extremely dynamic zone, for it is here that the motion of the sea interacts with the sediment, rock of the land or the artificial barriers. In order to prohibit or retard erosions due to the extreme Typhoon or storm induced waves, man has constructed these of temporary or more permanent nature, but they caused problems of other erosions from the secondary effect of them and a bad influence on the seascape. In considering the energy available to accelerate sediment transport and erosion in the surf zone, where the waves are broken, and offshore beyond the breaker line, the wave height and the wave period should be taken account. Hence, we tried to present an applicability of the submerged artificial Bio-reefs analyzing waves by a numerical model such that they could reduce the wave power without the secondary effect and restoration of marine ecologies. A new technique of beach preservation is by artificial reefs with artificial and/or natural kelps or sea plants. By engineering the geometry of the nearshore reef, the wave attenuation ability of the feature can be optimized Higher, wider and longer reefs provide the greatest barrier against wave energy but material volumes, navigation hazards, placement methods and other factors require engineering considerations for the overall design of the nearshore reefs.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.26 no.1
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• pp.25-32
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• 2014

Offshore wind power structures are subject to coastal hydrodynamic loading such as wind and wave loads. A considerable number of turbines have been installed in Europe, but so far none in Korea. Interest in offshore wind energy is growing in Korea, and it is expected that projects will reach the design stage in the near future. This paper discusses the level of structural reliability implied by the design rules of ABS(2010, 2013) and IEC(2009). Metocean conditions in 4 Korean seas(Gunsan, HeMOSU 1, Mokpo, Jeju) were used in the calibrations to calculate the aerodynamic and hydrodynamic loads as well as the structural responses of the typical designs of offshore wind turbines. Due to the higher variability of the wind and wave climate in hurricane-prone areas, applying IEC strength design criteria in combination with Korea west sea conditions could result in a design with much lower reliability index than what is anticipated from a design in European waters. To achieve the same level of safety as those in European waters, application of ABS 100 year design standards are recommended. Level-1 reliability-based design suitable for the Korean sea state conditions should be introduced because the IEC standards does not consider the typhoon effects in depth and the ABS standards is a WSD design method. In addition, the design equation should be established based on the statistical characteristics of the wind and wave loads of the Korean sea areas.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.25 no.5
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• pp.267-275
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• 2013

This study projected the future ocean wave climate changes based on global climate change scenario using the coupled climate model HadGEM2-AO according to the emission scenarios and using regional wave model. Annual mean significant wave height (SWH) is linked closely to annual mean wind speed during the forthcoming 21st Century. Because annual mean speed decreased in the western North Pacific, annual mean SWH is projected to decrease in the future. The annual mean SWH decreases for the last 30 years of the 21st century relative to the period 1971-2000 are 2~7% for RCP4.5 and 4~11% for RCP8.5, respectively. Also, extreme SWH and wind speed are projected to decrease in the future. In terms of seasonal mean, winter extreme SWH shows similar trend with annual extreme SWH; however, that of summer shows large increasing tendency compared with current climate in the western North Pacific. Therefore, typhoon intensity in the future might be more severe in the future climate.

• Journal of the Korean Society of Marine Environment & Safety
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• v.22 no.7
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• pp.869-875
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• 2016

The purpose of this study is to analyze the long-term wave characteristics and tendencies of coastal waters near Korea based on wave hind-casting modelling. Wave hind-casting modelling was performed with a wind data set from ECMWF (2001~2014), which provides data from 1979 to the present. The results of numerical modelling were verified with observed data collected using wave buoys installed by the Korea Meteorological Administration (KMA) and Korea Hydrographic and Oceanographic Agency (KHOA) in offshore waters. The results agreed well with observations from buoy stations, especially during event periods such as typhoons. The quantitative RMSE value was 0.5 m, which was significant. Consequently, the results of a wave tendency analysis for 14 years (2001~2014) showed an increased appearance ratio for waves of more than 2 m in height at all regional domains. The mean appearance ratio was 0.082 % per year, which implies that coastal waves have been increasing continuously. This coastal wave tendency analysis data can be used to evaluate coastal vulnerability due to recent climate change and the design of coastal erosion prevention structures.

• Journal of the Korean Society of Marine Environment & Safety
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• v.23 no.2
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• pp.139-145
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• 2017

Recently, gusts, typhoon and tsunamis have been occurring more frequently around the world. In such an emergency situation, a moored vessel can be used to predict and analyze other vessel behavior, but if the mooring system is destroyed, marine casualties can occur. Therefore, it is necessary to determine quantitatively whether a vessel should be kept in the harbour or evacuate. In this study, moored ship safety in an exclusive wharf according to swell effects on motion and mooring load have been investigated using numerical simulations. The maximum tension exerted on mooring lines exceeded the Safety Working Load for intervals 12 and 15 seconds. The maximum bollard force also exceeded 35 tons (allowable force) in all evaluation cases. The surge motion criteria result for safe working conditions exceeded 3 meters more than the wave period 12 seconds with a wind speed of 25 knots. As a result, a risk rating matrix (risk category- very high risk, high risk and moderate risk) was developed with reference to major external forces such as wind force, wave height and wave periods to provide criteria for determining the control of capabilities of mooring systems to prevent accidents.

• Journal of the Korean Society for Marine Environment & Energy
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• v.17 no.2
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• pp.63-69
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• 2014

Analysis frequency spectrum through observed wave data in northeastern shore, jeju island, during winter and fall, and review wave characteristics. In order to compute maximum wave height, we calculate the ratio of significant wave height to maximum wave height using the linear regression equation. In addition, for calculating JONSWAP spectrum, we assumed ${\gamma}$ value using significant wave height and peak frequency in the observation area. Consequently, the highest frequency is below 1 m in the case of significant wave height and during the first observation, the mean of height was estimated at 0.523 m and during the scend observation, it was 0.423 m. Furthermore, in peak frequency, the highest frequency was 0.12 Hz~0.15 Hz (period is nearly 6.67s~8.33s), the results of ${\gamma}$ from using significant wave height and peak frequency is 2.72 and the significant wave height calculated by straight linear regression equation was $1.635H_s$.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• v.1
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• pp.57-62
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• 2006

Busan New Port, under construction aiming for the hub of Northeast Asia and Partly in operation, had damaged up to 48 billion Won due to Typhoon 'maemi' in 2003. The present criteria of domestic harbor design only describes about the critical wave height with respect to the size of vessel for harbor tranquility. The berth operation ratio which represents the annual available berthing days is depending on the efficiency of cargo handling work and this depends on the motion of the moored vessel due to the wave action and the characteristics of cargo gears. The motion of moored vessel might be related not only to the wave height but also to wave period. Furthermore, the berth operation ratio relies on external forces such as currents and winds, including the characteristics of mooring system and the specification of the moored vessel. In this study we only deal with berth operation ratio in normal sea state, considering wave and current by measured data and numerical calculation. Especially we tried to evaluate the berth operation ratio for each berth adopting the variation of dredging and reclamation plan and the change of wave environment during the process of the new port construction. For better understanding and analysis of wave transformation process, we applied the steady state spectral wave model and extended mild-slope wave model to the related site. This study summarizes comparisons of harbor responses predicted by two numerical predictions obtained at Busan New port site. Field and numerical model analysis was conducted for the original port plan and the final corrected plan.

• Journal of the Korean Society for Environmental Technology
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• v.18 no.2
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• pp.165-172
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• 2017

In current stage, it is hard to predict the scale of damage caused by natural disaster and it is hard to deal with it. However, in case of disaster planning level, if it is possible to predict the scale of disaster then quick reaction can be done which will reduce the damage. In the present study, therefore, function of wind wave damage estimation among various disaster is developed. Damage of wind wave and typhoon in eastern and Jeju coastal zone was collected from disaster report (1991~2014) published by Ministry of Public Safety and Security and to reflect inflation rate, 2014 damage cost was converted. Also, wave height, wind speed, wave direction, wave period, etc was collected from Meteorological Administration and Korea Hydrographic and Oceanographic Administration web site. To reflect the characteristic of coastal zone when wave damage occurs, CODI(Coastal Disaster Index), COSI(Coastal Sensitivity Index), CPII(Coastal Potential Impact Index) published by Korea Hydrographic and Oceanographic Agency in 2015 were used. When damage occurs, function predicting wind wave damage was developed through weather condition, regional characteristic index and correlation of damage cost.