• 동력기계공학회지
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• 제15권1호
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• pp.64-71
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• 2011

The Tension Leg Platform(TLP) is restrained from oscillating vertically by tethers(or tendons), which are vertical anchor lines tensioned by the platform buoyancy larger than the platform weight. Thus a TLP is a compliant structure which allows lateral movements of surge, sway, and yaw but restrains heave, pitch, roll. In this paper, the motions of a TLP in current and waves were investigated. Hydrodynamic forces and wave exciting forces acting on the TLP were evaluated using the three dimensional source distribution method. The motion responses and tension variations of the TLP were analyzed in the case of including current or not including one in regular waves and effects of current on the TLP were investigated.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2002년도 추계학술대회 논문집
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• pp.256-260
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• 2002

This report summarizes the results of global performance analysis of TLP(Tension Leg Platform) at in-place operation condition. The frequency and time domain analysis were performed to calculate the wave induced dynamic responses of TLP using the commercial 3-D diffraction program, MOSES. As results of the analysis, air-gap, excursion and tension on the tendons&risers were provided. For verifying, the existed numerical and experimental result were compared with the results of the present study.

• 한국해양공학회지
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• 제5권1호
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• pp.16-24
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• 1991

This paper presents a method of the reliability analysis for a tension leg platform(TLP)in severe storm waves by using the first passage concept of the random tensile stress in the tendons. In the present method, two failure conditions are considered ;i.e., the exceedance of the ultimate tensile capacity and the occurrence of the negative tension. In order to consider the correlation effects between the failure events for each corner resulted from the rupture of all tencons at one corner, a new system limit state for a rectangular shaped TLP is developed, which is defined in terms of the TLP motions in the vertical plane ;i.e., heave, roll, and pitch. To illustrate the validity of the present method, the numerical analysis is carried out for two TLP's with different structural dimensions. Then, the results are compared with those by other methods.

• 대한토목학회논문집
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• 제7권4호
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• pp.73-81
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• 1987

본 논문에서는 파랑하중에 대한 Tension Leg Platform(TLP)의 tether와 platform의 동적거동해석에 대해서 연구하였다. tether의 동특성 효과를 적절하고도 간단히 고려할 수 있는 platform 해석모델을 제안하여 platform 운동해석을 수행하였으며, tether에 작용하여 인장력에 기인된 기하학적 강성을 고려한 유한요소법을 사용하여 tether의 거동을 해석하였다. 해석 예제용구조물로는 설치수심이 1000ft 및 3000ft인 두 가상적인 TLP를 선택하였으며, 비교를 목적으로 tether의 동특성 효과를 고려하지 않은 기존모델 및 platform과 tether를 조합한 모델 등에 의한 해석도 수행하여, 그 결과를 본 연구에서 제안한 모델에 의한 platform 운동과 tether의 거동 해석결과와 비교분석하였다. 아울러, tether의 통상적인 휨강성 및 tether에 작용하는 파랑하중이 tether의 거동에 미치는 영향정도도 고찰하였다.

• Structural Engineering and Mechanics
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• 제59권3호
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• pp.559-577
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• 2016

There are many theoretical analyses and experimental studies of the hydrodynamics for the tension leg platform (TLP) of a floating wind turbine. However, there has been little research on the arrangement of the TLP's internal structure. In this study, a TLP model and a 5-MW wind turbine model as proposed by the Minstitute of Technology and the National Renewable Energy Laboratory have been adopted, respectively, to comprehensively analyze wind effects and wave and current combinations. The external additional coupling loads on the TLP and the effects of the loads on variables of the internal structure have been calculated. The study investigates preliminary layout parameters-namely, the thickness of the tension leg body, the contact mode of the top tower on the tension leg, the internal stiffening arrangement, and the formation of the spoke structure-and conducts sensitivity analyses of the TLP internal structure. Stress is found to be at a maximum at the top of the tension leg structure and the maximum stress has low sensitivity to the load application point. Different methods of reducing maximum stress have been researched and analyzed, and the effectiveness of these methods is analyzed. Filling of the spoke structure with concrete is discussed. Since the TLP structure for offshore wind power is still under early exploration, arrangements and the configuration of the internal structure, exploration and improvements are ongoing. With regard to its research and analysis process, this paper aims to guide future applications of tension leg structures for floating wind turbine.

• International Journal of Ocean System Engineering
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• 제4권1호
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• pp.19-28
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• 2014

The tension leg platform (TLP) is a vertically moored structure with excess buoyancy. The TLP is regarded as moored structure in horizontal plan, while inherit stiffness of fixed platform in vertical plane. In this paper, a numerical study using modified Morison equation was carried out in the time domain to investigate the influence of nonlinearities due to hydrodynamic forces and the coupling effect between surge, sway, heave, roll, pitch and yaw degrees of freedom on the dynamic behavior of TLP's. The stiffness of the TLP was derived from a combination of hydrostatic restoring forces and restoring forces due to cables and the nonlinear equations of motion were solved utilizing Newmark's beta integration scheme. The effect of tethers length and wave characteristics such as wave period and wave height on the response of TLP's was evaluated. Only uni-directional waves in the surge direction was considered in the analysis. It was found that for short wave periods (i.e. 10 sec.), the surge response consisted of small amplitude oscillations about a displaced position that is significantly dependent on tether length, wave height; whereas for longer wave periods, the surge response showed high amplitude oscillations about that is significantly dependent on tether length.

• 대한토목학회논문집
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• 제7권3호
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• pp.223-228
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• 1987

본 논문에서는 Tension Leg Platform(TLP)에 작용하는 파랑하중을 간단한 Morison 방정식을 이용하여 효율적으로 산정할 수 있는 방법에 대해서 연구하였다. 본 방법에서는 MacCamy-Fuchs 산란파이론에 기초를 둔 파동력 감소계수를 도입하여 파의 산란효과를 근사적으로 고려하였으며, Morison 방정식 상에서는 무시되는 연직기둥의 바닥에 작용하는 수직력을 이 면에서의 동압력과 수직방향의 부가질량에 관련된 관성력으로 산정하여 고려하였다. 수치해석은 1000 ft 수심에 위치한 가상적인 구조물에 $0^{\circ}$ 및 $45^{\circ}$로 입사하는 파에 대하여 전술한 방법 및 이론적으로 보다 정확한 산란파이론에 의한 방법을 사용하여 수행하였으며, TLP 운동 및 tether의 상단 인장력의 전달함수(RAO)를 구하여 비교 검토하였다.

• Journal of Advanced Research in Ocean Engineering
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• 제2권4호
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• pp.179-191
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• 2016

As the demand for renewable energy has increased following the worldwide agreement to act against global climate change and disaster, large-scale floating offshore wind systems have become a more viable solution. However, the cost of the whole system is still too high for practical realization. To make the cost of a floating wind system be more economical, a new concept of tension leg platform (TLP) type ocean floating wind system has been developed. To verify the performance of a 5-MW TLP type ocean floating wind power system designed by the Korea Advanced Institute of Science and Technology, the FAST simulation developed by the National Renewable Energy Laboratory is used. Further, 1/50 scale model tests have been carried out in the ocean engineering tank of the Research Institute of Medium and Small Shipbuilding, Korea. This paper compares the simulation and ocean engineering tank test results on motion prediction and tension assessment of the TLP anchor.

• Ocean Systems Engineering
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• 제4권4호
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• pp.327-342
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• 2014

The tension leg platform (TLP) is one of the compliant structures which are generally used for deep water oil exploration. With respect to the horizontal degrees of freedom, it behaves like a floating structure moored by vertical tethers which are pretension due to the excess buoyancy of the platform, whereas with respect to the vertical degrees of freedom, it is stiff and resembles a fixed structure and is not allowed to float freely. In the current study, a numerical study for square TLP using modified Morison equation was carried out in the time domain with water particle kinematics using Airy's linear wave theory to investigate the effect of changing the tether tension force on the stiffness matrix of TLP's, the dynamic behavior of TLP's; and on the fatigue stresses in the cables. The effect was investigated for different parameters of the hydrodynamic forces such as wave periods, and wave heights. The numerical study takes into consideration the effect of coupling between various degrees of freedom. The stiffness of the TLP was derived from a combination of hydrostatic restoring forces and restoring forces due to cables. Nonlinear equation was solved using Newmark's beta integration method. Only uni-directional waves in the surge direction was considered in the analysis. It was found that for short wave periods (i.e., 10 sec.), the surge response consisted of small amplitude oscillations about a displaced position that is significantly dependent on tether tension force, wave height; whereas for longer wave periods, the surge response showed high amplitude oscillations that is significantly dependent on wave height, and that special attention should be given to tethers fatigue because of their high tensile static and dynamic stress.

• Smart Structures and Systems
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• 제9권1호
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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.