• 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.

• Journal of Ocean Engineering and Technology
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• v.23 no.1
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• pp.96-103
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• 2009

In 2006, Jeju Island in South Korea experienced a crisis, no electricity for three hours anywhere in the entire island. This incident was caused by a domino effect that occurred after one of the submarine power cables connecting the island to Haenam, a coastal city on the mainland, was damaged by an external load, probably from a ship anchor or a steel pile being used in marine farming. This study presents a collision analysis of a new submarine power cable protector called arch type reinforced concrete. For the analysis, a dynamic finite element program, ANSYS AUTODYN, was used to examine the displacement and stress of the submarine power cable protector using different material models (RHT concrete model, Mohr.Coulomb concrete model). In addition, two reinforcing bar spacings, 75 mm and 150 mm, were considered. From the analyses, the effects of the parameters (concrete model and spacing) on the results (displacement and stress) were analyzed, and the relations between the damage and parameters were found.

• Journal of Ocean Engineering and Technology
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• v.30 no.2
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• pp.109-116
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• 2016

A flexible concrete mattress (FCM) is a structural system for protecting submarine power or communication cables under various load types. To evaluate its of protection performance, a numerical analysis of an FCM under an anchor collision was performed. The explicit dynamics of the finite element analysis program ANSYS were used for the collision analysis. The influences of the steel reinforcement modeling and collision angle of the anchor on the collision behavior of the FCM were estimated. The FCM damage was evaluated based on the results of the numerical analysis considering the numerical modeling and collision environment.

• Journal of Ocean Engineering and Technology
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• v.29 no.1
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• pp.70-77
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• 2015

The purpose of this study was to provide fundamental data for an anchor collision simulation of an FCM (flexible concrete mattress). Numerical material models (elastic-perfectly plastic model, Drucker-Prager model, and RHT concrete model) were compared. ANSYS Explicit Dynamics was used for collision analyses. An FE model was used for the anchor, FCM, andreinforcement bars. The results showed that the behavior of the FCM was verydifferent that those ofthe material models. In particular, the effect of the pressure dependent strength was most noticeable among the properties of concrete.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.24 no.6
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• pp.609-616
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• 2011

In the study, we analyzed the collision characteristics of a so-called arch-type submarine cable protector by considering the changes in drop heights of a stock anchor and material models for concrete and steel reinforcing bars. We considered plastic kinematics model and Johnson-Holmquist Concrete model for the concrete and linear elastic model and plastic kinematics model for the reinforcing bars. The drop heights of 2-ton stock anchor were selected as 3, 5, and 8.83m, respectively. ANSYS, a finite element analysis program, was used for the collision analysis. To save computational time, we converted those drop heights into initial velocities by the principle of energy conservation. From the sensitivity of the material models on the drop height changes, it is shown that the collision response of the reinforcing bars is sensitive firstly on the steel models and secondly on the concrete models, while the collision response of the concrete is sensitive only on the concrete models.

• Journal of Ocean Engineering and Technology
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• v.32 no.5
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• pp.324-332
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• 2018

It is known that damages to the subsea cables used for electric power transmission between islands and countries, including renewable energy from offshore wind power, current, tides, etc., cost much to restore, which causes social and economic losses. Various types of fishing rigs and anchors have been reported to be the greatest hazards to subsea cables. It is possible to design and construct a suitable protection facility for a subsea cable by precisely estimating the underwater behavior of such hazardous apparatuses. In this study, numerical simulations of the underwater behaviors of various hazardous apparatuses were carried out using fluid-structure interaction (FSI) analysis as a basic study to simulate the actual behavior phenomena of hazardous apparatuses in relation to a subsea cable. In addition, the underwater drop characteristics according to the types of hazardous apparatuses were compared. In order to verify the accuracy of the FSI analysis method used in this study, we compared the test results for underwater drops of a steel ball bearing. Stock anchors, stockless anchors, and rocket piles, which were actually reported to be the cases of damage to subsea cables along the southwest coast of Korea, were considered as the hazardous apparatuses for the numerical simulations. Each hazardous apparatus was generated by a Lagrangian model and coupled with the fluid domain idealized by the Eulerian equation to construct the three-dimensional FSI analysis model. The accuracy of the numerical simulation results was verified by comparing them with the analytical solutions, and the underwater drop characteristics according to the types of hazard apparatuses were compared.