• 한국CDE학회논문집
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• 제15권1호
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• pp.1-10
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• 2010

Recently, a shipyard is making every effort to efficiently manage equipments of resources such as a gantry crane, transporter, and so on. So far block lifting scheduling of a gantry crane has been manually performed by a manager of the shipyard, and thus it took much time to get scheduling results and moreover the quality of them was not optimal. To improve this, a block lifting scheduling system of the gantry crane using optimization techniques was developed in this study. First, a block lifting scheduling problem was mathematically formulated as a multi-objective optimization problem, considering the minimization of travel distance at an idle state and wire replacement during block lifting. Then, to solve the problem, a meta-heuristic optimization algorithm based on the genetic algorithm was proposed. To evaluate the efficiency and applicability of the developed system, it was applied to an actual block lifting scheduling problem of the shipyard. The result shows that blocks can be efficiently lifted by the gantry crane using the developed system, compared to manual scheduling by a manager.

• 대한조선학회논문집
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• 제41권2호
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• pp.98-105
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• 2004

This study focuses on an analytical approach to calculate four crane lifting forces for heavy ship hull blocks considering elongations of lilting slings. Four-crane-lifting is a redundant problem. During lifting procedures, in addition to the force and moment equilibrium equations, a compatibility condition is introduced to determine 4 unknown lifting forces. For verification of the method, a ship hull block with field measurements data is analyzed and the result shows that the information obtained by current method could be useful to engineers to conduct lifting work at shipyards.

• 대한조선학회 특별논문집
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• 대한조선학회 2005년도 특별논문집
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• pp.107-112
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• 2005

During assembling the ship block, the lifting and turnover events are not only inevitable but also very important for safety aspects and block accuracy. However, they have been executed in empirical ways rather than numerical ways in consideration of the building schedule. In this paper, a structural analysis has been carried out for the container ship side block that collapsed in the course turnover stage. As a result, the causes of collapse and countermeasure plans are presented.

• 대한조선학회논문집
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• 제55권4호
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• pp.297-305
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• 2018

In a shipyard, block lifting is an important process in the production of ships and offshore structures. Block lifting is a sensitive process because lifting blocks have to be erected with exact positions and orientations. If we use a numerical method for the process, it is important to find tensions of wires and positions of equalizers to maintain the initial equilibrium position of the block. At this time, equations of motion of the block should be solved to calculate the initial equilibrium position of the block. Because the solving technique changes according to the number of equalizers, a suitable equation for the corresponding problem is required. In this study, three types of equations are proposed to find the initial equilibrium position of the block according to the number of equalizers. The Newton-Raphson's method is used to solve nonlinear simultaneous equations and the optimization method is used to determine the appropriate solution to the undetermined problem. To evaluate the applicability of the proposed methods, the dynamic simulations are performed using the tensions calculated from the proposed methods, and the results are discussed. The results show that the proposed methods can be effectively used to determine initial equilibrium position of the block for the block lifting.

• 한국해양공학회지
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• 제20권1호
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• pp.16-19
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• 2006

With the fast growth of the shipbuilding industry, the number of lifting lugs used every year has reached onehundred. This paper is aimed at examining the cause of cracking in the hopper top plate, due to block lifting. First of all, we have investigated the fracture surface in the occurrence position of the crack of the hopper top plate, using the scanning electron microscope. In this study, we have evaluated the structural strength for COT super block under present lifting conditions. For this purpose, the equivalent stresses have been calculated by linear elastic analysis, using the finite element program ABAQUS.

• 대한조선학회논문집
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• 제53권2호
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• pp.135-143
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• 2016

In this study, an embedded system composed of equipment setting, block importing, scenario setting and output reporting is developed in multi-body dynamics program, ADAMS, for conducting dynamic structural analysis of block lifting process. First, equipment used for block lifting process is set in the simulation environment and the shapes and functions of two lifting beams, and six block loaders are provided as the equipment. Second, the modal analysis result of the lifting block is imported from the static structural analysis system, NASTRAN. Third, the lifting scenarios, such as hoisting, waiting, trolley moving, and wire connecting, are set in the system. Finally, output results in the forms of plots, texts and tables, are reported after the dynamic structural analysis. The test examples conducted in a shipyard are applied into the developed system in various condition and scenarios. The loads at the lug points, the stress contours, and the hot spot tables of the developed system are compared with the result of the static analysis system.

• 대한조선학회논문집
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• 제58권2호
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• pp.84-89
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• 2021

Recently, shipyards are making many efforts to reduce the number of the mounted blocks by increasing the block size. This is to improve productivity and reduce related costs by minimizing block movement and shortening the building period. However, as the blocks become larger, the weight increases considerably. If the target block has a damage due to an unexpected accident during block lifting, it may seriously cause a problem of the reusability of the block. In this study, a large-sized block of the offshore structure weighing 480 tons was lifting with a total of seven sling belts, and one sling belt was broken while it was moving, resulting in a situation in which a part of the edge of the block collided with the ground. The aim of this paper is to verify the structural integrity of the block that directly collides with the ground in the form of free fall due to the sling breakage. Considering that the hook loads acting on several sling belts holding the block are redistributed when a sling belt is broken, the hook loads were recalculated at the angle just before the sling breakage. These loads were used to check the safety of the sling belts. In addition, FE analysis was performed by calculating the amount of impact from the free fall condition, obtaining the impact area by using Hertz's contact theory, and then applying the impact load to the area.

• 복합신소재구조학회 논문집
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• 제6권2호
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• pp.77-84
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• 2015

The purpose of this study was the analytical safety evaluation on the super-structure of precast modular bridge using standardized modular members and robotic construction during the transportation routing and lifting conditions. In order to evaluate the safety performance of the bridge system, 3-D full scale Finite Element (FE) of 40 m standardized modular block was developed in ABAQUS, followed by the analytical study to classify the structural system according to steel girder structures: 1) modular bridge block lifting method including the steel girder system; 2) modular bridge block lifting method without the steel girder system. The results from the analytical study revealed that the maximum stress of each modular member was within the maximum allowable stresses during lifting condition. However, the stress concentration at the connected area was more critical in comparison to the behavior of 40 m combined modular blocks during lifting time

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집C
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• pp.219-223
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• 2001

This paper introduces DS/Block-Structure - a structural analysis module of DS/Block, which is a Design System to simulate the behavior of a ship block in various crane operations and to evaluate its structural deformation using the finite element method. It runs based on a CAD program, Pro/ENGINEER, and structural analyses are performed by a developed FE code. Boundary conditions for the FE analysis of a ship block under lifting and turnover operation are also considered.

• 대한조선학회 특별논문집
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• 대한조선학회 2011년도 특별논문집
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• pp.82-89
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• 2011

In general, a number of lifting lugs have been used in shipbuilding industry and the D-type lugs are mainly used. The aim of this paper is to increase the cycle of the use and to reduce the size of lifting lugs to introduce lightweight shackle. In this study, nonlinear elasto-plastic analysis has been performed to confirm the ultimate strength of lifting lugs. In order to evaluate the proper design-load distribution around lug eye, the contact force between lifting lug and shackle pin has been realized by gab element model. Gap element modeling and nonlinear analysis are carried out using the finite element program MSC/PATRAN & ABQUS. Additionally the ultimate strength tests were performed to verify the structural adequacy of newly designed lifting lug and to insure safety of it. The D-10, 15, 20 & 40 ton models which are mainly used in the block erection are selected in the strength test. According to the results of the analysis and strength test, the ultimate strength of the newly designed lifting lugs has been estimated to exceed 3 times of design working load.