• 대한조선학회 특별논문집
• /
• 대한조선학회 2008년도 특별논문집
• /
• pp.118-125
• /
• 2008

The deck plates of ship block is made of thin plates in their construction. A main reason of using thin plates is that deck plates don't need to support large structural loads. Therefore, out-of-plane deformations between stiffeners are frequent in deck blocks. Because these are got right by correction heating, they continuously causes quality problems in the final dock-building process. According to preceding research, the lifting process by cranes would offset the effect of correction heating. This study finds out the remained efficiency of correction heating when tensional loads are added by a lifting to corrected parts. We used inherent strains in calculating the efficiency, and established the methodology where the positions for callings are. For getting more accurate positions, besides the structural lifting analysis, welding deformation analysis with upper block and measured data from a serial ship are also referenced.

• Journal of Advanced Research in Ocean Engineering
• /
• 제1권3호
• /
• pp.148-156
• /
• 2015

Deck plates of ships or offshore structures would make out-of-plane distortion for their thin thickness. These distortions are usually straightened by thermal straightening such as flame heating method. After thermal straightening, the blocks are lifted and moved by cranes to assemble it at dry-dock stage. After this lifting process, out-of-plane deformation again happens frequently. And then, they continuously cause quality and accuracy problems in the final dry-dock process. So, it takes more time for repair and correction working. According to preceding research, the lifting process by cranes would offset the effect on thermal straightening. The target of this study is to develop a methodology analyzing the remaining efficiency of thermal straightening after block lifting. The development was based on the assumption of yield state at straightening region. Therefore the remaining efficiency was obtained by different stiffness slope while lifting & relieving. The efficiency formula was designed using inherent strain, and we made a table of zero-efficiency by cooling speed and class rule's steels. As a result, if the stress orthogonal to straightened line is calculated during lifting analysis by FEA, the efficiency can be obtained linearly to the values in the table. Finally, even optimized carling position can be designed by considering the regional data from series project and welding region on deck.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2001년도 춘계학술대회논문집C
• /
• pp.164-169
• /
• 2001

A comprehensive extension of functions and efficiency of the software system, DS/Block, developed earlier for the purpose of simulation of the motion of a ship block during lifting and turnover operation. A viewpoint change used in 3D-CAD is utilized and saves the time for displays of a series of configurations for the motion. The Euler parameters are adopted to convert 3 rotational degrees of freedom about global coordinate system to those about local coordinate system defined in Pro/ENGINEER. DS/Block provides FEM input data for stress and strain analyses. Several functions are incorporated for user-friendliness. DS/Block is to be tested and installed in a shipyard.

• 한국소음진동공학회논문집
• /
• 제20권8호
• /
• pp.753-760
• /
• 2010

In this paper, the lifting analysis of a floating crane with a shipbuilding block is performed. Since floating cranes are operated in ocean waves, six degree-of-freedom motions are considered in the dynamic equations of motions of the floating crane and the block. The boom of the floating crane is considered as an elastic body in the analysis, and is modeled as three dimensional beam based on the finite element formulation. The hydrostatic and hydrodynamic forces by a regular wave are considered as external forces. By solving the equations of motions numerically, the dynamic responses of the floating crane and the block are simulated. The simulation results with different wave directions are compared and the conditions which cause maximum responses are discussed.

• 한국공간구조학회논문집
• /
• 제8권3호
• /
• pp.45-51
• /
• 2008

단층 래티스 돔은 경량이면서도 높은 강성을 가지므로 대공간 구조물로서 유리하며, 이 구조물은 기둥 없이 널은 공간을 확보해야하는 구조적 특성으로 인하여 시공시 불안정 현상이 발생할 수 있다. 현재 국내에서 대공간 지붕구조물의 설치 방법으로 가장 많이 도입되고 있는 Erection공법은 Block공법이며, 이 공법은 지상에서 조립한 대공간 지붕 골조를 크레인 등으로 소정의 위치까지 들어 올려 지붕구조를 완성해 가는 설치 공법이다. Block 공법에 있어서 인양할 포인트를 선정하는 작업은 대단히 중요하다. 즉, 인양 시 골조의 변형과 좌굴 등에 대해서 가장 안전하고 경제적인 절점을 인양 포인트로 선정할 필요가 있다. 따라서 본 연구에서는 가장 안전하고 경제적인 Erection을 위한 기초자료를 얻기 위하여 삼각형 네트워크를 갖는 단층 래티스 돔의 Erection 시 인양 포인트에 따른 구조물의 거동 및 좌굴 특성을 연구하는데 그 목적이 있다. 얻어진 결론은 1) 돔의 높이 H가 작을수록 인양위치에 따른 좌굴내력의 영향이 큰 것을 알 수 있었으며, 반대로 돔의 높이 H가 클수록 인양위치에 따른 좌굴내력의 영향은 미미한 것을 알 수 있었다. 2) 인양 위치에 관계없이 인양로프 길이에 따른 좌굴내력의 영향은 크지 않은 것을 알 수 있었다.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2000년도 춘계학술대회논문집A
• /
• pp.714-719
• /
• 2000

In this paper, an application program is made to simulate the behavior of a ship block under various crane works and to generate data of lu9 reactions and wire tensions. The program is based on a CAD program, Pro/ENGINEER. A ship is composed of more than 100 ship blocks. In order to lift, move, turn, or put a ship block at a convenient location fur assembling, workers in a shipyard use cranes, wires, and lugs temporarily attached to the block. In the procedure of lifting and turning a ship block with a crane, it is important to find suitable lug points and wires to do the handling efficiently and prevent accidents. Evaluation of forces in lugs and wires is necessary, but the problem is rather complex due to nonlinearity and nonuniqueness. In the present development, the nonlinear system of equations for quasi-static equilibriums is derived and a Newton type solution method is adopted to solve the system. The importance of initial estimates to the solution is illustrated and two approaches are utilized and compared. With the program developed, users can assign lug points on the CAD model by mouse and choose various linking devices at each crane point. Users can try to simulate the motion for any prescribed conditions, compare the motion of the block and the reactions and choose appropriate lug points and the type of wires and lugs.

• International Journal of Naval Architecture and Ocean Engineering
• /
• 제11권2호
• /
• pp.858-864
• /
• 2019

The increasing demands of lifting lugs can be attributed to the rapid advancement of shipbuilding and offshore-structure production technologies and an exponential increase in the size of the block units of ship structures. Therefore, to ensure safety during the transportation and turnover of large blocks, it is important to determine the structural integrity and position of lifting lugs. However, because the manufacturing cost and availability of lugs are important considerations, low cost and easily obtainable steel compositions of grades different from those of the blocks are often used as alternatives. The purpose of this study is to investigate the effect of a lifting-lug metal on the physical properties of a base metal in a dissimilar welding between the base metal and lifting lug. The effect was evaluated by observing the metal microstructures and determining the hardness and dilution values on the cross-sectional surface of the lifting lug. According to the results of the metal microstructures, impact, hardness, and emission spectrochemical analysis at the surface from where the lug was removed confirmed that the chemical composition of the lifting-lug metal did not influence the physical properties of the base metal.

• Management Science and Financial Engineering
• /
• 제14권1호
• /
• pp.91-96
• /
• 2008

Robust knapsack problem appears when dealing with data uncertainty on the knapsack constraint. This note presents a generalization of the cover inequality for the problem with its lifting procedure. Specifically, we show that the lifting can be done in a polynomial time as in the usual knapsack problem. The results can serve as a building block in devising an efficient branch-and-cut algorithm for the general robust (0, 1) IP problem.

• 한국해양공학회지
• /
• 제29권4호
• /
• pp.309-316
• /
• 2015

Lifting lugs are frequently used in shipyards to transport and turn over the blocks of ships and offshore structures. With the development of shipbuilding technology, blocks have increased in size, and block management technology has assumed a more important role in shipbuilding to enhance the productivity. For the sake of economics, as well as the safe design of a lug structure, a more rational design procedure based on a rigorous structural analysis is needed. This study investigated the strength characteristics of T-type lugs, considering the influence of blocks on which lugs are attached, by varying the in-plane and out-of-plane load direction. In this paper, the ultimate strength is also addressed for cases that include or do not include blocks in the strength analysis. In the present results, when there was a load acting in the normal direction to the block surface, the strength characteristics became poor, and the ultimate strength decreased. This paper ends by describing the need for further study to develop a more rational design for a lug structure.

• 한국해양공학회:학술대회논문집
• /
• 한국해양공학회 2000년도 춘계학술대회 논문집
• /
• pp.189-194
• /
• 2000

Due to the rapid growth of ship building industry and increment of ship construction in Korea, several hundred thousand of lifting lugs per year, have been installed at the lifting positions of ship block and removed after finishing their function, therefore, appropriate design system for strength check or optimal design of each lug structure has been required in order to increase the capability of efficient design. In this study, design system of D-type lifting lug structure which is most popular and useful in shipyards, was developed for the purpose of initial design of lug structure. Developed system layout and graphic user interface for this design system based on the C++ language were explained step by step. Using this design system, more efficient performance of lug structural design will be expected on the windows of personal computer.