• Journal of Korean Society of Coastal and Ocean Engineers
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• v.33 no.6
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• pp.374-382
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• 2021

The scour risk assessment was conducted for ultimate limit state of newly developed penta pod suction bucket support structures for a 5.5 MW offshore wind turbine. The hazard was found by using an empirical formula for scour depth suitable for considering marine environmental conditions such as significant wave height, significant wave period, and current velocity. The scour fragility curve was calculated by using allowable bearing capacity criteria of suction foundation. The scour risk was assessed by combining the scour hazard and the scour fragility.

• Journal of the Korean GEO-environmental Society
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• v.15 no.6
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• pp.75-83
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• 2014

Suction bucket foundation is installed with the differential pressure created by pumping water out of bucket. Bucket foundation has usually been utilized in mooring anchor for offshore platform or floating oil and gas production facilities in the open sea. After suction bucket foundation successfully was applied as the foundation for offshore wind turbines in Europe, it recently attracts much attention in Korea, too. To estimate the penetration resistance of the suction bucket foundation is one of the important matters that should be considered during its installation. This study carried out a series of model tests to investigate the penetration resistance of suction bucket foundation. And the mobilized soil strength factor was reviewed through comparing the experimental results by two installation ways (e.g., push-in-load and suction) and the results calculated by the conventional equation.

• Journal of the Korean GEO-environmental Society
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• v.20 no.12
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• pp.41-47
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• 2019

This paper deals with the reliability analysis of foundation for an offshore wind turbine system. Reliability analyses were carried out for suction bucket foundation considering the uncertainties in soil and structural parameters. In reliability analysis, the vertical and lateral resistances are defined as base limit states. The case studies were carried out using the preliminarily designed foundations at western-south mainland sea of Korea. From reliability analyses, vertical resistance for free-slip condition has overall lower reliability index, and submerged unit weight and internal friction angle of seabed soil are governing factors in vertical and lateral resistance in this case.

• Journal of Ocean Engineering and Technology
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• v.31 no.4
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• pp.281-287
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• 2017

In the case of fixed offshore wind turbines, scouring phenomena have been reported around sub-structures as a result of currents, which seriously damage the structural stability. A parametric study of the various sub-structures of a fixed offshore wind turbine was performed to investigate their effects on the scouring phenomena. For a suction bucket foundation and monopile, the effects of the stick-up heights and water depth were studied, respectively. The open source libraries, called OpenFOAM, were used to simulate a violent flow around a foundation. The numerical methods were selected based on a two-dimensional analysis of a suction bucket. Based on the results for various stick-up heights, a larger scouring region was observed with an increase in the stick-up height because of the down-wash flow around a foundation. Based on the results for various monopile water depths, the water depth had an insignificant effect on the scouring.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.11
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• pp.870-877
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• 2020

A suction bucket foundation, especially useful at depths of more than 20m, is a method of construction. The method first places an empty upturned bucket at the target site. Then, the bucket is installed by sucking water or air into it to create negative pressure. For stability, it is crucial to secure the verticality of the bucket. However, inclination by the bucket may occur due to sea-bottom conditions. In general, a repeated intrusion-pulling method is used for securing verticality. However, it takes a long time to complete the job. In this paper, we propose a real-time suction bucket verticality monitoring system. Specifically, the system consists of a sensor unit that collects raw verticality data, a controller that processes the data and wirelessly transmits the information, and a display unit that shows verticality information of a circular steel pipe. The system is implemented using an inclination sensor and an embedded controller. Experimental results show that the proposed system can efficiently measure roll/pitch information with a 0.028% margin of error. Furthermore, we show that the system properly operates in a suction bucket-based model experiment.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.4
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• pp.1908-1914
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• 2012

As the turbine capacity and the water depth of wind farms are increasing, the construction cost of substructures and foundations for offshore wind turbines is expected to increase. Since the installation of suction bucket foundation is achieved by both self-weight and applied suction, the construction generally does not require heavy equipment for penetration. This study provides an economic analysis on the tripod which have the bucket foundations and compares that the jacket foundation at 50m water depth on sand layer or soft layer. As the strength of the soil and the number of the foundation is increasing, the construction cost of the tripod with the bucket foundations is more economically feasible than the jacket foundation.

• KEPCO Journal on Electric Power and Energy
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• v.2 no.3
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• pp.469-475
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• 2016

As we are facing the shortage of oil energy, studies on renewable energy, wind energy research has been naturally getting attention. Among wind energies, ocean wind energy is relatively abundant compared to land wind energy and therefore, is getting much attention in terms of its efficiency. However, the problem is the cost. Generally, the cost ratio of the supporting structure is over 25% of the total installation cost of a offshore wind turbine system. Thus, it is very important to reduce the total installation cost of the offshore wind turbine and develop accurate analysis methodology for various offshore wind turbine foundations. In this study, nonlinear structure-soil interaction analyses have been proposed and conducted for the typical suction bucket model of an offshore wind turbine foundation, and the results were compared with experimental test data for numerical validations.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.32 no.6
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• pp.524-530
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• 2020

The risk of offshore wind turbine support structures by scour has been proposed. The proposed utilize probabilities of scour depths and fragilities according to scour depth and a modification of a seismic risk analysis method. The probability distribution of scour depth was calculated using a equation which is suitable to consider marine environmental conditions such as significant wave height, significant period, and current velocity, and dynamic analysis was performed on an offshore wind turbine equipped with an suction bucket to find fragility. Then, the risk of offshore wind turbine support structure considering scour can be found by integrating the scour probability and the fragility.