Application areas of floating marine structure systems have been increased with the development of power generation systems using renewable energy. Hence it is necessary to analyze the behavior of these floating systems for efficient design and operation. In this study, a computational analysis was performed to predict the characteristics of mooring lines load variation connected to a floating marine structure with waves. Pressure on the floating body and mooring lines load were analyzed with wave direction and height. The floating body stability severely decreased for 90° of the wave incident direction, and maximum load of the mooring lines increased with the height. These results are expected to be applicable for optimal design of the marine floating system.

The Port of Pyeong Taek is located on the west coast, meaning that the difference between the rise and fall of tide is great (flood tide 1.8 to 2.9 knots, ebb tide 1.6 to 2.9 knots). Due to mainly N~NW’ly strong winds & high waves during winter, navigating as well as loading & discharging vessels must focus on cargo handling. The strong tidal and wind forces in the Port of Pyeong Taek can push an LNG carrier away from its berth, which will end up causing forced disconnection between the vessel’s cargo line and shore-side loading arm. The primary consequence of this disconnection will be LNG leakage, which will lead to tremendous physical damage to the hull and shore-side equipment. In this study, the 125K LNG Moss Type ship docked at No. 1 Pier of the Pyeong Taek is observed, and the tension of the mooring line during cargo handling is calculated using a combination of wind and waves to determine effective mooring line and mooring line priority management. As a result if the wind direction is 90° to the left and right of the bow, it was found that line monitoring should be performed bearing special attention to the Fore Spring Line, Fore Breast Line, and Aft Spring Line.

The difference of mooring tension by type of buoy was investigated in the circulating water channel and the wave tank for deducting the most stable buoy from the current and the wave condition. 5 types of buoy made up of short cylinder laid vertically (CL-V), short cylinder laid horizontally (CL-H), capsule (CS), sphere (SP) and long cylinder (CL-L) were used for experiments. A mooring line and a weight were connected with each buoy. A tensile gauge was installed between a mooring line and a weight. All buoy’s mooring tension was measured at the same time for the wave test with periods of 1.5~3.0 sec and wave heights of 0.1~0.3 m, and the current test with flow speeds of 0.2~1.0 m/sec. As a result, the order of tension value in the wave test was CL-H > CL-V > SP > CS > CL-L. In the current test CL-V and CL-H were recorded in the largest tension value, whereas SP has the smallest tension value. So it seems that SP buoy is the most effective in the location affected by fast current. CS is predicted to be suitable for a location that influence of wave is important more than that of current if practical use in the field is considered. And it was found that the difference of mooring tension among buoys in wave is related to the product of the cross sectional area and the drag coefficient for the buoy’s bottom side in high wave height. The factor for the current condition was not found. But it was supposed to be related to complex factors like a dimension and a shape by buoy’s posture to flow.

침하식 가두리 시설의 안정성 평가를 위한 기초 단계로서 일방향 규칙파 중 2점 계류된 원통형 부체를 대상으로 부설 수심의 변화에 따른 부체의 동적 거동 및 계류삭에 작용하는 장력 산정에 관한 수치 계산을 수행하였다. 수치 계산 결과, 수면 상에 설치된 부체를 수면 아래의 약 1/2되는 수층까지 침하 시킨 경우 그것은 동적 거동과 파력은 초기 상태에 비해 각각 최대 50%와 77%까지 감소되어 시설물을 수중으로 침하 시키면 그것의 안정성 유지에 매우 효과적임을 확인할 수 있었다. 또한 부체의 전 후단 변위 및 계류삭에 작용하는 장력의 최대치는 부체의 고유 주기의 영향으로 인해 그것은 길이 d 에 대한 파장 λ의 비 즉, d/λ가 약 0.66에서 나타났으며, 이와 같은 현상은 기존 수리 모형실험 결과와 비교적 잘 일치하였다. 그러나 본 수치 계산의 신뢰성 확인을 위해서는 수리 모형실험을 통해 부체의 고유 주기와 작용 파고에 대한 전 후단 변위 등에 대한 충분한 검토가 요구된다.