• The Journal of the Acoustical Society of Korea
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• v.35 no.4
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• pp.261-271
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• 2016

In the prediction of response of a pile in soil, numerical approaches such as a finite element method are generally applied due to complicate nonlinear behaviors of soils. However, the numerical methods based on the finite elements require heavy efforts in pile and soil modelling and also take long computing time. So their usage is limited especially in the early design stage in which principal dimensions and properties are not specified and tend to vary. On the contrary, theoretical approaches adopting linear approximations for soils are relatively simple and easy to model and take short computing time. Therefore, if they are validated to be reliable, they would be applicable in predicting responses of a pile in soil, particularly in early design stage. In case of wind turbines regarded in this study, it is required to assess their natural frequencies in early stages, and in this simulation the supporting pile inserted in soil could be replaced with a simplified elastic boundary condition at the bottom end of the wind turbine tower. To do this, analysis for a pile in soil is performed in this study to extract the spring constants at the top end of the pile. The pile in soil can be modelled as a beam on elastic spring by assuming that the soils deform within an elastic range. In this study, it is attempted to predict pile deformations and influence factors for lateral loads by means of the beam-on-spring model. As two example supporting structures for wind turbines, mono pile and suction pile models with different diameters are examined by evaluating their influence factors and validated by comparing them with those reported in literature. In addition, the deflection profiles along the depth and spring constants at the top end of the piles are compared to assess their supporting features.

• Journal of the Korean Geotechnical Society
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• v.26 no.11
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• pp.63-73
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• 2010

Monopiles, used as one foundation option for offshore wind turbines, are usually subjected to great cyclic lateral loads due to wind and wave. In this study, model pile load tests were performed using calibration chamber and three model piles with different pile lengths in order to investigate the behavior of laterally cyclic loaded piles driven into sand. Model test results show that the first loading cycle generates a bigger displacement than the following ones, and the permanent displacement of piles by one loading cycle decreases with increasing the number of cycles. 1-way cyclic loading causes the permanent displacement in the same direction as cyclic loading, whereas 2-way cyclic loading causes the permanent displacement in the reverse direction of initial loading. It is also observed that the permanent displacement of piles due to cyclic lateral loads increases with decreasing relative density of soil and with increasing the magnitude of cyclic loads. However, it is insensitive to the earth pressure ratio of soil and embedded pile length. In addition, based on the model pile load test results, equations for estimation of the permanent lateral displacement and rotation angle of piles due to 1-way cyclic lateral loads are proposed.

• Journal of Navigation and Port Research
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• v.43 no.6
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• pp.420-428
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• 2019

Although marine structures are a risk factor interfering with the passage of ships, there are no obvious guidelines on the required safety distance between ships and marine structures under regulations and laws. In this study, the width of the shipping route width was set based on the AIS data to analyze the separation distance between marine structures and ships, and the ships were classified by the length of each ship. By analyzing the distribution at marine structures, this study confirmed that the ships' traffic volume was in the form of normal distribution. To statistically analyze the separation distance between the traffic distribution results and the normal distribution of ships in this study, the traffic pattern analysis around the marine structures was performed. As a result, the traffic pattern was different by length and the recommended safety distance for each length is presented accordingly. Referring to the IMO (International Maritime Organization) the standard turning circle and reference of safety separation distance between ships and offshore wind turbines of the CESMA (Confederation of European Shipmasters' Associations) and P IANC (World Association for Waterborne Transport Infrastructures), the analysis was conducted on ships that did not follow the set distance among the AIS data by setting the distance within the recommended ship safety distance to 5-7 overall length. As a result, the 5.5 length over all of the safety recommendations were selected as appropriate, and based on the above results, the two cases recommending ship safety distance were proposed.