• Transactions of the Korean Society of Mechanical Engineers A
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• v.40 no.4
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• pp.337-342
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• 2016

A spudcan is mounted on the lower leg of the jack-up rig, a device for preventing a rollover of a structure and to support the structure in a stable sea floor. At the time of inserting the surface of the spud can to penetrate when the sand layer is stable and smoothly pulled to the clay layer, and at that time of recovery when uploading the spud can is equipped with a water injection device. In this study, it is significant to optimize the shape of pipelines holes for water injection device and it was set in two kinds of shape, the oval and round. Interpretation of the subject into the site of Gulf of Mexico offshore Wind Turbine Installation Vessels (WTIV) was chosen as a target platform. Using the ANSYS Workbench commercial programs, optimal design was conducted. The results of this study can be applied to the hole-shaped design of various marine structures.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.12
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• pp.106-111
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• 2017

In this study, the stiffness of an LMU (Leg Mating Unit), which is a device required for installing the top side part of an offshore structure, was examined through structural analysis. This unit is mounted on the supporting point of the structure and is used to absorb the shock at installation. It is a cylindrical structure with an empty center. To support the vertical load, elastomeric bearings (EBs) and iron plates are laminated in layers. The stiffness of the EBs is basically influenced by the size of the bearings, but it varies with the number of laminated sheets inside the same sized structure. The relationship between the stiffener and the compressive stiffness is investigated, and its design is suggested. The stiffness of the EBs is analyzed by calculating the reaction force, while controlling the displacement. First, the relationship between the size of the reinforcing plate and the compressive stiffness is considered. Next, the relationship between the number of stacked reinforcing plates and the compression stiffness is considered. Different loads are required for each installed point. The goal is to design the compression stiffness in such a way that the same deformation occurs at each point in the analysis. In this study, ANSYS is used to perform the FE analysis.

• Journal of Navigation and Port Research
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• v.29 no.5 s.101
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• pp.383-388
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• 2005

To install a radar reflector on small ships, such as a small fishing vessel, a fishery buoy, and a barge ship for fishery, it is very important to develop the optimal system which may determine a proper installation location. For this, the response characteristics how waves have an effect on the small ships should be accurately analyzed. In this paper, we analyze the dynamic behaviors of small ships, which may be caused by irregular waves. To do this, we investigate how a barge ship responses to wavelength, water depth, and directions of incoming waves. The analyzed results shall be utilized to evaluate an effect on a radar cross section when we install an radar reflector on a barge ship for fishery and a small ship.

• Journal of the Korean Geosynthetics Society
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• v.17 no.3
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• pp.1-8
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• 2018

Sand compaction pile (SCP) is a ground improvement method which is used to secure the stability of the soft ground by using a type of replacement pile filled with coarse grained material. The behavior characteristics of the SCP, which is frequently used for improving both the onshore and offshore ground, is governed by the ground condition, the installation method, and replacement ratio. Therefore, the stability of the SCP in terms of the bearing capacity and displacement needs to be evaluated considering both the design values and in-situ conditions of construction site. In this study, numerical analysis is carried out based on the conditions of 00 revetment construction site in South Korea where unexpected displacement occurred during construction of SCP. Based on the analysis results, the displacement of the revetment structure according to the replacement ratio of the SCP was compared to the result calculated from design formulas. The results showed that the lateral displacement can be exceeded the reference value from proposed criteria regardless of increased replacement ratio of SPC. It is also confirmed that the behavior of the structure according to the replacement ratio of SPC in not reflected in the existing calculation methods. Therefore, the stability of the SCP composite ground should be examined through the site inspection after the SCP construction.

• Journal of Intelligence and Information Systems
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• v.26 no.4
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• pp.87-109
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• 2020

Currently, thanks to the major stride made in developing wired and wireless communication technology, a variety of IT services are available on land. This trend is leading to an increasing demand for IT services to vessels on the water as well. And it is expected that the request for various IT services such as two-way digital data transmission, Web, APP, etc. is on the rise to the extent that they are available on land. However, while a high-speed information communication network is easily accessible on land because it is based upon a fixed infrastructure like an AP and a base station, it is not the case on the water. As a result, a radio communication network-based voice communication service is usually used at sea. To solve this problem, an additional frequency for digital data exchange was allocated, and a ship ad-hoc network (SANET) was proposed that can be utilized by using this frequency. Instead of satellite communication that costs a lot in installation and usage, SANET was developed to provide various IT services to ships based on IP in the sea. Connectivity between land base stations and ships is important in the SANET. To have this connection, a ship must be a member of the network with its IP address assigned. This paper proposes a SANET-CC protocol that allows ships to be assigned their own IP address. SANET-CC propagates several non-overlapping IP addresses through the entire network from land base stations to ships in the form of the tree. Ships allocate their own IP addresses through the exchange of simple requests and response messages with land base stations or M-ships that can allocate IP addresses. Therefore, SANET-CC can eliminate the IP collision prevention (Duplicate Address Detection) process and the process of network separation or integration caused by the movement of the ship. Various simulations were performed to verify the applicability of this protocol to SANET. The outcome of such simulations shows us the following. First, using SANET-CC, about 91% of the ships in the network were able to receive IP addresses under any circumstances. It is 6% higher than the existing studies. And it suggests that if variables are adjusted to each port's environment, it may show further improved results. Second, this work shows us that it takes all vessels an average of 10 seconds to receive IP addresses regardless of conditions. It represents a 50% decrease in time compared to the average of 20 seconds in the previous study. Also Besides, taking it into account that when existing studies were on 50 to 200 vessels, this study on 100 to 400 vessels, the efficiency can be much higher. Third, existing studies have not been able to derive optimal values according to variables. This is because it does not have a consistent pattern depending on the variable. This means that optimal variables values cannot be set for each port under diverse environments. This paper, however, shows us that the result values from the variables exhibit a consistent pattern. This is significant in that it can be applied to each port by adjusting the variable values. It was also confirmed that regardless of the number of ships, the IP allocation ratio was the most efficient at about 96 percent if the waiting time after the IP request was 75ms, and that the tree structure could maintain a stable network configuration when the number of IPs was over 30000. Fourth, this study can be used to design a network for supporting intelligent maritime control systems and services offshore, instead of satellite communication. And if LTE-M is set up, it is possible to use it for various intelligent services.