• Journal of Ocean Engineering and Technology
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• v.15 no.3
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• pp.131-131
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• 2001

• Journal of the Korean Geotechnical Society
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• v.20 no.3
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• pp.85-96
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• 2004

The ultimate bearing capacity of surface foundations on a sand layer overlying clay has been theoretically investigated. First, a review of previous studies on the bearing capacity problems for this type of foundation was performed and a discussion was presented concerning the practical application. Second, the kinematic approach of limit analysis was used to calculate the upper bound of the true ultimate bearing capacity. The kinematic solutions are upper bounds and their accuracy depends primarily on the nature of the assumed failure mechanism. This approach makes it convenient to create design charts, and it is possible to trace the influence of parameters. Third, the commercial finite element program ABAQUS was applied to obtain the ultimate bearing capacity based on the elasto-plastic theory. Results obtained from the kinematic approach were compared with those from the program ABAQUS and the limit equilibrium equations proposed by Yamaguchi, Meyerhof and Okamura et al. Finally, the validities of the results from the kinematic approach, the results from the program ABAQUS and the limit equilibrium equations were examined.

• Journal of the Korean Society for Marine Environment & Energy
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• v.19 no.1
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• pp.7-17
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• 2016

The present study experimentally considers dynamic performance of large floating wave-offshore hybrid power generation platform in extreme conditions. In order to evaluate the motion performance of the large floating hybrid power generation platform, 1/50 scaled model was manufactured. A mooring line was also manufactured, and free-decay and static pull-out tests were carried out to check the mooring model. A mooring line table was introduced to satisfy the water depth, and environmental conditions were checked. Motion responses in regular waves were measured and complicated environmental conditions including wave, wind, and current were applied to see the dynamic performance in extreme/survival conditions. Maximum motion and acceleration were judged following the design criteria, and maximum offset and mooring tension were also checked based on the rule. The characteristics of hybrid power generation platform are discussed based on these data.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• v.1
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• pp.195-201
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• 2006

The wave load and its influence on the response of offshore structure have been well investigated through the statistical approach based on the linear theory. The linear approach has a limitation to apply the extreme condition such as freak wave, which corresponds to extreme value of wave spectrum. The main topic of present study is to develop an efficient numerical method to predict wave load induced by extreme wave. As a numerical method, finite element method based on variational principle is adopted. The frequency-focusing method is applied to generate the extreme wave in the numerical wave tank. The wave load on the bottom mounted vertical cylinder is investigated. The hydroelastic response of the vertical cylinder is also investigated so as to compare the wave loads with the rigid body case in the extreme wave condition.

• Journal of Navigation and Port Research
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• v.31 no.1 s.117
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• pp.21-27
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• 2007

The wave load and its influence on the response of offshore structure have been well investigated through the statistical approach based on the linear theory. The linear approach has a limitation to apply the extreme condition such as extreme wave, which corresponds to extreme value of wave spectrum. The main topic of present study is to develop an efficient numerical method to predict wave load induced by extreme wave. As a numerical method, finite element method based on variational principle is adopted. The frequency-focusing method is applied to generate the extreme wave in the numerical wave tank. The wave load on the bottom mounted vertical cylinder is investigated. The hydroelastic response of the vertical cylinder is also investigated so as to compare the wave loads with the rigid body case in the extreme wave condition.

• Journal of Ocean Engineering and Technology
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• v.1 no.2
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• pp.39-51
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• 1987

석유시추 보호관의 비선형 운동을 시뮬레이트하는 유효한 해법이 non-uniform grid 유한차분법과 implicit time 적분법에 근거하여 제시되었다. 극한 상태에 있는 지지 플랫폼의 상승 가속도에 의해 생기는 보호관의 동적 좌굴형 반응에 관하여 상세히 연구되었고, 이 반응에 미치는 중요 변수가 규명되었다. 운동의 현저한 감소와 이에 따른 응력들이 컴플라이언트 행오프(hang-off)를 적용시킴으로써 얻어졌다.

• Journal of Ocean Engineering and Technology
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• v.15 no.3
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• pp.134-141
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• 2001

An experimental method to investigate the dynamic characteristics of buoys in extreme environmental condition is established. Because the buoy model requires a resonable size for accurate experiment, the test condition in model basin that satisfies the similarity law is hardly compatible with capability of test facilities. It is suggested that the linear wave component that is unable to satisfy similarity is separated with others. The model experiment is carried out with mitigated condition for the linear wave components while others including wave drift, current and wind are keeping the similarities. Then, the result can be extrapolated to give the dynamic behavior of buoys n extreme condition because linear wave component is solely responsibly to oscillatory buoy motion and other environmental components are applied as a initial tension. The similarity for current and wind conditions is viewed as equivalence of restoring forces. The validity of proposed method is examined with different types of standard ocean buoys and it indicates that the linearity of measured characteristics is assured with a limitation of resonable distance between test and estimated wave conditions.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2001.05a
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• pp.208-215
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• 2001

An experimental method to investigate the dynamic charasteristics of buoys in extreme environmental condition is established. Because the buoy model requires a resonable size for accurate experiment, the test condition in model basin that satisfies the similarity law is hardly met with capability of test facilities. It is suggested that the linear wave component that is unable to satisy similarity is separated with others. The model experiment can be carried out with mitigated condition for the linear wave components while others including wave drift, current and wind are keeping the similarities. Then the result is extrapolated to give the dynamic behavior of buoys in extreme condition because linear wave component is soley responsible to oscillatory buoy motion and other environmental components are applied as a initial tension. the similarity for current and wind conditions is viewed as equivalence of restoring forces. the validity of proposed method is examined with different types of standard ocean buoys and it indicates that the linearity of measured characteristics is assured with a limitation of resonable distance between test and estimated wave conditions.

• Journal of the Society of Naval Architects of Korea
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• v.47 no.3
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• pp.328-341
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• 2010

The authors adopt the Unmanned Undersea Vehicle(UUV), which has taken the shape of manta(Sohn et al. 2006). They call here it Manta-type Unmanned Undersea Test Vehicle(MUUTV). MUUTV is designed with the similar concept of UUV called Manta Test Vehicle(MTV), which was originally built by the Naval Undersea Warfare Center, USA(Lisiewicz and French 2000, Sirmalis et al. 2001, U.S. Navy 2004). The present study deals with evaluation of extreme motion of MUUTV at large attack angles. Extreme motion contains, for example, rising and depth change due to operation of hovering thrusters attached to MUUTV, lateral motion due to ocean current applied to MUUTV at low advance velocity, and so on. Numerical simulation technique has been utilized. The previous mathematical model on manoeuvring motion of MUUTV(Bae et al. 2009a) is basically adopted. Based on the results of present model experiment on extreme motion, the mathematical model is revised and supplemented in order to describe extreme motion. The hydrodynamic derivatives related to extreme motion are obtained from present model experiment and the other derivatives are referred to previous work(Bae et al. 2009a).

• Bulletin of the Korean Space Science Society
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• 2004.04a
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• pp.77-77
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• 2004

인공위성은 정상궤도에 들어선 후부터 수명을 다하는 시기까지 각종 복사, 열(온도차), 고진공, 미세중력, 미세운석과 우주파편 등에 의해 영향을 받게 된다. 특히, 위성체에 미치는 열환경은 위성이 궤도를 그리며 운동하는 동안 태양과 지구로부터의 복사량의 크기 및 분포에 따라 결정되는데, 약 5,50$0^{\circ}C$의 흑체온도를 갖고 있는 태양과 -27$0^{\circ}C$의 심우주는 위성체에서 태양이 비추는 부분과 반대편과의 온도를 극한으로 만들게 된다. (중략)