부유구조체 형상에 따른 동요감소 특성분석

이두호(Lee, Du Ho),정연주(Jeong, Youn Ju),유영준(You, Young Jun),박민수(Park, Min Su) 한국해안해양공학회 2013 한국해안해양공학회 논문집 Vol.25 No.6

이전 연구에서는 부유구조체의 동요저감을 위해 폰툰과 반잠수식 부유구조체 형식을 결합하여 하이브리드 부유구조체를 제안한 바 있다. 하이브리드 부유구조체는 입사파랑에 대한 동요감소에는 효과적이었으나 부유구조체에 충분한 부력을 제공할 수 없는 단점이 있었다. 이와 같은 단점을 보완하기 위해 본 연구에서는 새로운 형식의 콤비네이션 부유구조체를 제안하였다. 입사 파랑하중에 대한 부유구조체의 동요감소 효과를 비교하기위해 폰툰, 콤비네이션 그리고 하이브리드 부유구조체에 대한 수치해석을 동수역학 해석프로그램 ANSYS AQWA를 이용하여 수행하였다. 본 연구에서 제안된 콤비네이션 부유구조체가 다른 부유구조체에 비해 동요감소에 효과적인 것을 확인할 수 있었다. 따라서 콤비네이션 부유구조체는 앞으로 개발될 초대형 부유구조체 건설을 위한 신형식 부유구조체로서 매우 유용하게 사용될 것으로 판단된다. In previous study, the hybrid floating structure composed of a pontoon and a semi-submersible was suggested to reduce the motions of floating structure. It was reported that the suggested hybrid floating structure could reduce the motions. However, the hybrid floating structure could not support enough buoyancy. In this study, the combination floating structure is newly suggested to resolve the problem. In order to adopt the shape of floating structures reducing the motions, the hydrodynamic analysis of various floating structures such as the pontoon, the hybrid and the combination of floating structure is carried out through hydrodynamic analysis program ANSYS AQWA. It is found that the combination floating structure is remarkably effective to reduce the motions compared to the other cases. Thus, the suggested combination floating structure may be a useful offshore structure for constructing a very large floating structure.

중국 도시군의 유동인구 구조 분석

최준환 ( Choi Joon Hwan ) 한중사회과학학회 2018 한중사회과학연구 Vol.16 No.2

The floating population has been increasing in China due to rapid economic development and accelerating industrialization speed after the reform and opening of 1978. The floating population is the key agenda of China’s future population development and the main factor of transition in urban, rural, and local structures. Furthermore, the continuous increase in the floating population is creating a large and unprecedented metropolitan regions. The metropolitan regions appearing in China are the subject of new urbanization. They are the main overflowing population areas as well as the strategic growth point of China’s development in their future economic society. After considering the situation above, this study selected 19 metropolitan regions of China, divided them into 3 regions and analyzed the structure of their floating population. The results are as the followings. First, the floating population of China showed to center around the metropolitan regions. When analyzed by regions, the amount of influx of floating population showed to highly increase around Guojia metropolitan regions, which are the center of major cities, followed by Quyu metropolitan regions and Diqu metropolitan regions. Second, in the analysis results by educational background of the floating population, the low educated tended to move onto the non-city groups while the educated showed great amount of flow into the major metropolitan regions. Third, in the analysis results of the floating population by the state of marriage, the single and first marriage showed high flowing rates into the major cities while the divorced and bereavement tended to greatly flow into the non-city groups. Lastly, in the analysis results by different age, in ages between 15 to 49, the floating population to metropolitan regions showed higher rates compared to the floating population to non-city areas. However, in ages over 50, the gap of the floating population rates between Guojia metropolitan regions and areas with no city groups showed to decrease. As a result, although China is institutionally restricting the flow of its population, floating population is taking place in forms of irregular workers and under the name of Migrant workers. In other words, though it is impossible in China for population movement between the urban and rural areas to happen in system, floating population is actually occurring in reality. Therefore, this study can ease off arguments that consider Harris-Todaro model and Lewis model to be inappropriate in the case of China and become the evidence to the fact that these models can somewhat decipher the reality of China.

해저지진의 수직지반운동에 의한 부유식 해양구조물의 지진응답 해석기법 개발

이진호,김재관,진병무 한국지진공학회 2014 한국지진공학회논문집 Vol.18 No.6

Considering a rigorously fluid-structure interaction, a method for an earthquake response analysis of a floating offshore structure subjected to vertical ground motion from a seaquake is developed. Mass, damping, stiffness, and hydrostatic stiffness matrices of the floating offshore structure are obtained from a finite-element model. The sea water is assumed to be a compressible, nonviscous, ideal fluid. Hydrodynamic pressure, which is applied to the structure, from the sea water is assessed using its finite elements and transmitting boundary. Considering the fluid-structure interaction, added mass and force from the hydrodynamic pressure is obtained, which will be combined with the numerical model for the structure. Hydrodynamic pressure in a free field subjected to vertical ground motion and due to harmonic vibration of a floating massless rigid circular plate are calculated and compared with analytical solutions for verification. Using the developed method, the earthquake responses of a floating offshore structure subjected to a vertical ground motion from the seaquake is obtained. It is concluded that the earthquake responses of a floating offshore structure to vertical ground motion is severely influenced by the compressibility of sea water.

해저지진의 수직지반운동에 의한 부유식 해양구조물의 지진응답 해석기법 개발

이진호,김재관,진병무 한국지진공학회 2014 한국지진공학회논문집 Vol.18 No.6

Considering a rigorously fluid-structure interaction, a method for an earthquake response analysis of a floating offshore structure subjected to vertical ground motion from a seaquake is developed. Mass, damping, stiffness, and hydrostatic stiffness matrices of the floating offshore structure are obtained from a finite-element model. The sea water is assumed to be a compressible, nonviscous, ideal fluid. Hydrodynamic pressure, which is applied to the structure, from the sea water is assessed using its finite elements and transmitting boundary. Considering the fluid-structure interaction, added mass and force from the hydrodynamic pressure is obtained, which will be combined with the numerical model for the structure. Hydrodynamic pressure in a free field subjected to vertical ground motion and due to harmonic vibration of a floating massless rigid circular plate are calculated and compared with analytical solutions for verification. Using the developed method, the earthquake responses of a floating offshore structure subjected to a vertical ground motion from the seaquake is obtained. It is concluded that the earthquake responses of a floating offshore structure to vertical ground motion is severely influenced by the compressibility of sea water.

中国西部地区产业结构升级背景下 流动人口就业结构的分析研究 – 以贵阳市为例 –

서상,이상만 중국지역학회 2023 중국지역연구 Vol.10 No.1

In the process of China’s continuous development of reform and development, with the reform of the household registration system and urbanization, population movement has become a key phenomenon of economic development, and population movement between different regions has become more frequent. Guiyang, as a region of economic development in western China, has also been affected to some extent. In the process of rapid economic development, the size of Guiyang’s migrant population continues to grow. Based on this background, this paper introduces the basic characteristics of the spatial pattern of the migrant population in Guiyang and explains the spatial and temporal changes in the spatial pattern of the migrant population in Guiyang, which is a key strategic issue in the process of modernization of the city. Guiyang is a rapidly developing region in western China, and based on the background of the new western development, Guiyang City attracts a large number of migrant populations to visit, live, work, and study in Guiyang through its unique advantages. The large influx of people provides talents for Guiyang’s economic development and plays an important role in the process of economic development. In addition, it also causes social crimes and insufficient social security. Guiyang needs to effectively solve the problem of the migrant population in the process of economic growth transformation and stable economic development, and it is a key issue that needs to be solved to make Guiyang an influential regional growth pole and a central city in western China. With the rapid development of the market economy, there are significant opportunities for the upgrading and adjustment of China’s industrial structure. The coordination between industrial structure and employment structure will still have an important impact on macroeconomic development. Especially since the launch of the strategy of developing the country through science and education and strengthening the country through talents, employment in higher education is also closely related to the development of the industrial structure of the region. We propose specific optimization strategies to promote the synergy of industrial structure and higher education employment structure in the Guiyang region of western China in order to accelerate the region’s economic development. The industrial structure has a decisive influence on the employment structure, and the employment structure can in turn influence the industrial structure and other economic structures. The coordination between industrial structure and employment structure has a significant impact on the adjustment and optimization of industrial structure and the adequate and rational allocation of labor resources. In this paper, the coordination of industrial structure and employment structure in Guiyang is analyzed quantitatively and qualitatively through several indicators. It measures whether the development between the two is relevant and how it needs to be adjusted in the future to achieve sustainable development.

Analytical study on hydrodynamic motions and structural behaviors of hybrid floating structure

Jeong, Youn-Ju,Lee, Du-Ho,Park, Min-Su,You, Young-Jun Techno-Press 2013 Ocean systems engineering Vol.3 No.1

In this study, a hybrid floating structure with cylinder was introduced to reduce the hydrodynamic motions of the pontoon type. The hybrid floating structure is composed of cylinders and semi-opened side sections to penetrate the wave impact energy. In order to exactly investigate the hydrodynamic motions and structural behavior of the hybrid floating structure under the wave loadings, integrated analysis of hydrodynamic and structural behavior were carried out on the hybrid floating structure. Firstly, the hydrodynamic analyses were performed on the hybrid and pontoon models. Then, the wave-induced hydrodynamic pressures resulting from hydrodynamic analysis were directly mapped to the structural analysis model. And, finally, the structural analyses were carried out on the hybrid and pontoon models. As a result of this study, it was learned that the hybrid model of this study was showed to have more favorable hydrodynamic motions than the pontoon model. The surge motion was indicated even smaller motion at all over wave periods from 4.0 to 10.0 sec, and the heave and pitch motions indicated smaller motions beyond its wave period of 6.5 sec. However, the hybrid model was shown more unfavorable structural behavior than the pontoon model. High concentrated stress occurred at the bottom slab of the bow and stern part where the cylinder wall was connected to the bottom slab. Also, the hybrid model behaved with the elastic body motion due to weak stiffness of floating body and caused a large stress variation at the pure slab section between the cylinder walls. Hence, in order to overcome these problems, some alternatives which could be easily obtained from the simple modification of structural details were proposed.

중국 비유통주(國有股) 개혁에 관한 법적 고찰

이정표 한중법학회 2006 中國法硏究 Vol.6 No.-

Most of the listed companies in Chinese stock market have common and State-owned shares, which were limited in floating. The Stated-owned shares defines government possessed assets consisted in a certain evaluated process when stated-owned companies reformed into the qualified company. It characterizes that a total liabilities and net worth is included, but limited proportions. Currently, the floating shares are only 1/3 of total issued stocks from listed companies and 2/3 are of the non-floating shares. The reformation of stated-owned stocks means the non-floating shares convert to the floating shares. Regally, it called Split Share Structure (股權分置) correspondingly. Chinese and their authorities is currently processing this reformation drastically and they rapidly renovate security legislation since April 2005. If this reformation completes, the stated-owned asset management would be transferred to the floating shares and, finally, Chinese monetary circulation system would become a capital market economy system. It plans that non-floating shares of 20 enterprises stocks converts to the floating shares weekly until the end of 2006. The conversion method of stated-owned stocks to the floating shares is to approve 2/3 of stockholders who owned the non-floating shares in ‘A’ security market. The non-floating shares and floating shares stockholders have to deliberate the method of stock effacement simultaneously. The floating shares will shortly be released and directly influenced with the security market after completed this reformation. Chinese government enforces next three method; firstly, the reformation of split share structures, secondly, the non-floating shares prohibition of selling within an year, thirdly, stockholders who owned over 5% of the total value would forbid a selling as well. At the same time, the institutional investor has been recommended the acquiescent intervention as well as the foreign strategical investors induced the investments for solving secondary problems caused by the conversion. Meanwhile, the non-floating shares converted enterprises have given a certain advantages, such as issuing new bonds, bank credits and shares collateralized loan etc,. If those reformation completed successfully, the management system and co-operated governance of the listed companies would become transparented. Also the efficiency of the capital market would be improved by the merged effectiveness from ‘B’ and ‘A’ security markets.

부력 프리플랙션 효과가 콘크리트 부유구조체 구조성능에 미치는 영향에 대한 해석적 연구

이두호(Lee Du-Ho),정연주(Jeong Youn-Ju) 대한토목학회 2012 대한토목학회논문집 A Vol.32 No.2A

본 연구에서는 콘크리트 부유구조체의 구조성능을 향상시키기 위한 부력 프리플랙션 효과에 대한 해석적 연구를 수행하였다. 부력 프리플랙션은 부유구조체를 구성하는 모듈들의 부분적 부력차이에 의해 부유구조체에 프리플랙션 효과가 도입되는 것을 뜻한다. 부력 프리프랙션 효과를 검증하기 위해, 실제 설계에서 도출된 콘크리트 부유구조체 단면을 바탕으로 전체 부유구조체 길이에서 부력 부리플랙션 효과를 발생기키는 변단면 중앙부의 길이 비를 매개변수로 설정한 해석적 연구를 수행하였다. 해석결과는 부력 프리플랙션에 의해 도입되는 콘크리트 부유구초체의 하부 슬래브 응력상태와 부상 변위향에 대해, 이를 부력 프리플랙션과 활하중의 하중단계별로 분석하여 부력 프리플랙션 효과가 큰크리트 부유구조체의 구조성능에 미치는 영향을 분석하였다. 연구결과, 전체 부유구조체 길이에 대한 중앙부 모듈의 길이 비가 작은 경우에도 상대적으로 큰 부력 프리플랙션 효과가 발생되는 것으로 나타났다 부력 프리플랙션 효과는 중앙부 모듈의 길이 비에 따라 포물선의 형태를 나타내며, 중앙부 모듈의 길이 비 40~60%에서 최대의 효과가 도입되는 것으로 나타났다. 인접한 모듈들의 부력차이를 이용하는 부력 프리플랙션은 원리가 간단하여 적용이 간편하고, 부유구조체의 하부 슬래브에 효율적으로 사전 압축응력을 도입시킬 수 있는 것으로 나타났다. 이는 부유구조체의 하중지지능력 향상을 가져와 콘크리트 부유구조체의 구조성능 향상과 단면높이 슬림화에 기여할 수 있을 것으로 판단된다. In this study, an analytical studies were carried out for the buoyancy preflexion method to improve structural performance of concrete floating structures. The buoyancy preflexion means that the preflexion effects were induced to the floating structure due to the difference in buoyancy between the pontoon modules composing the floating structures. In order to verify the buoyancy preflexion effects, an analytical studies were carried out for the floating structures. The size and dimensions of FE model were determined through the structural design process. The parameter of this analytical study was length ratios of central module part, which induces buoyancy preflexion effects, to the total length. The analysis results were pre-compression on the bottom concrete slab and displacement of freeboard due to buoyancy preflexion effects. These results were processed according to the loading step, buoyancy preflexion loads on the bottom and live loads on the topside. Then, the buoyancy preflexion effects on structural performance was analyzed. As the results of this study, it was found that the byoyancy preflexion significantly influence on structural performance of floating structures. According to the length ratio, the buoyancy preflexion effects have a tendency of parabolic form and maximized at the length ratio 40~60% The buoyancy preflexion method is simple in principle and easy in application. Also, it can effectively induce pre-compression on the bottom concrete slab. Therefore, it can be concluded that the buoyancy preflexion method contribute to the improvement of structural performance and decreasing of the cross-sectional depth of floating structures.

추적식 수상 태양광발전 시스템의 설계 및 시공

김선희 ( Sun Hee Kim ),이영근 ( Young Guen Lee ),서수홍 ( Su Hong Seo ),주형중 ( Hyung Joong Joo ),윤순종 ( Soon Jong Yoon ) 한국복합재료학회 2014 Composites research Vol.27 No.2

대부분의 에너지는 전세계적으로 제한되어 있는 석유, 석탄, 천연가스 등 주로 화석연료로부터 얻어지고 있다. 최근, 고유가, 석유자원의 고갈, 기후변화 등이 신재생에너지를 포함한 비화석 연료가 세계적으로 주목을 받고 있는 이유 중의 하나이다. 이 연구에서는 고비강성 및 비강도, 고내부식성 및 내화학성 등을 장점으로 갖고 있는 펄트루젼 FRP(PFRP)를 사용하였다. 따라서 부유식 구조물의 설계와 시공을 위해서는 PFRP 재료가 우선적으로 선택될 수 있다. 추적식 수상 태양광발전 구조물의 설계는 유한요소해석 결과를 사용하여 수행되었으며, 구조물은 조립되어 수상에 설치되었다. 구조물을 설치하기 전에 안전성 문제를 유한요소법을 사용하여 검토하였으며, 그 결과 설계, 제작, 시공된 구조물은 외적으로 작용된 하중을 지지하는데 충분히 안전함을 알 수 있었다. Most of energy are obtained from oil, coal, and natural gas, most likely, fossil fuel which is limited throughout the world. Recently, high crude oil price, climate change, oil depletion, etc. are main reason to get attention to non-fossil energy including renewable energy in the world. In this study, we studied analysis and design of structure system composed of pultruded fiber reinforced polymer composite (PFRP) which has many advantages such as high specific strength and stiffness, high corrosion resistance and chemical resistance. For the design and construction of floating-type structure, PFRP structural members may be the first choice. Design of tracking-type floating PV generation structure was performed by using the results of the finite element analysis. The structure is fabricated and installed on the water surface. Before the installation of the structure, safety related problems associated with installation and operation are investigated using the finite element simulation and it was found that the structure is safe enough to resist externally applied loads.

대형 수중구조물 보수를 위한 부유식 섹터케이슨

이중우(Joong-Woo Lee),이승철(Seung-Chul Lee),이정수(Jung-Su Lee),곽승규(Seung-Kyu Kwak),김기담(Ki-Dam Kim) 한국항해항만학회 2007 한국항해항만학회지 Vol.31 No.05

최근 건설구조물의 하자보수기간은 5년에서 10년으로 연장되었고 건설품질 및 유지관리에 대한 인식의 변화에 따라 교량, 댐, 항만구조물의 수중부 은폐된 부분에 대한 유지관리를 위해 반영구적인 공법의 개발이 요구되고 있다. 본 연구에서는 지금까지 대형 강관 및 교각의 수중시공에서는 잠수부들의 기술능력부족과 수중에서의 작업조건의 까다로움 등으로 임시적인 작업이 되었던 현 실정을 고려하여 수중구조물 유지관리에 실용화 될 수 있는 공법으로 부체식 섹터케이슨을 제안하였다. 특히, 상부구조물이 수면에 가까운 경우 및 구조물간 간격이 좁은 경우 보수구간의 접근성과 교각과 같은 대형 수중구조물 유지.보수 시 드는 고비용의 문제 등으로 전체 구조체를 설치하는 대신 섹터케이슨을 개발하여 도입함으로써 비상시 이동과 장래 신속한 작업수행 및 작업수준 향상에 획기적인 역할이 기대된다. Recently, the defect maintenance period of the new construction structure was extended from 5 years to 10 years. And according to change of realization on the quality of construction and maintenance, a development of semi-permanent method of construction is required for maintenance of blind parts of underwater structure, such as bridge, dam, harbor, etc. In this study, we proposed a floating type sector drγ caisson, which is effective to the maintenance of submerged large structures. These large structures were being maintained incompletely, partly due to unskilled divers and difficult working condition Considering the easiness of access to the maintenance area and the cost for set up the working structure, especially for the case of structure slabs close to the sea surface and harrow pile span structures, we developed and introduced a sector dry caisson instead of the full caisson structure. By doing this, it is easy to move out the caisson rapidly in emergence case. Therefore, we expect that the floating sector caisson will contribute to reduce working time and improve the quality of underwater work in future days