플라이애쉬를 사용한 수중불분리성 콘크리트의 수화열에 관한 연구

권중현(JUNG-HYUN KWON) 한국해양공학회 2000 韓國海洋工學會誌 Vol.14 No.4

The concretes cast in the sea water would be likely to be rich mix and mass concrete. Therefore it is important to check out the hydration heat of concrete and to reduce it to prevent the concrete from processing the temperature crack. Recently the antiwashout agent is used on underwater concretes for preventing from the segregation of concrete in the water. The experimental studies were done for the combined cement replaced by fly ash 30% unit weight of binder to study on the characteristics of hydration heat of antiwashout underwater concrete, and its characteristic was discussed by comparing one cast in sea water with another one in air. The present paper showed that the hydration heat of concrete replaced by 30% of fly ash was more significantly reduced than the normal concrete. The hydration heat of antiwashout underwater concrete was higher than that of normal concrete, but it was reduced lower than the normal concrete by adding fly ash.

플라이애쉬 수중불분리성 콘크리트의 내해수성에 관한 염화물 촉진 시험

권중현(JUNG-HYUN KWON),김봉익(BONG-IK KIM) 한국해양공학회 2005 韓國海洋工學會誌 Vol.19 No.6

This paper describes the effect of fly ash replacement on seawater resistance of anti-washout underwater concrete, which was replaced cement by fly ash from 0% to 50%. The experimental work was performed to find out the variations of length and weight of specimens, using a chloride acceleration test in 40℃ The results show that the admixture using fly ash on an anti-washout underwater concrete in the sea environment makes it more durable for the attacks of chloride by seawater. Also, the length of specimens of anti-washout underwater concrete, at age 180 days, increased substantially, compared with normal concrete; however, the mixture in which cement was replaced 50% of fly ash shows 93% reduction of the expansion, compared with the normal anti-washout underwater concrete specimen.

플라이애시 수중불분리성 콘크리트의 수밀성에 관한 실험적 연구

권중현(JUNG-HYUN KWON),김봉익(BONG-IK KIM) 한국해양공학회 2008 韓國海洋工學會誌 Vol.22 No.4

This paper describes the effects of fly ash replacement on the water tightness of antiwashout underwater concrete, which replaced the cement with fly ash from 0% to 30%. The experimental work was performed to find out the depth of permeation of concrete specimens cast in air and cured in 23℃ tap water using an open center pressure type of water permeation tester. The results showed that the permeation depth values of antiwashout underwater concrete were deeper than normal concrete, but that an admixture using fly ash during antiwashout underwater concrete casting in air made it more watertight than normal concrete according to the water permeation testing. SEM observations of the specimensof fly ash antiwashout underwater concrete showed that it wasmore packed with structures because of the pozzolan reaction of the fly ash and cement.

플라이애쉬를 사용한 수중불분리성 콘크리트의 응결에 관한 실험적 연구

권중현(JUNG-HYUN KWON),김봉익(BONG-IK KIM) 한국해양공학회 2001 韓國海洋工學會誌 Vol.15 No.4

This paper describes the effect of fly ash replacement on the setting time of antiwashout underwater concrete, where cement was replaced by 0% to 50%. Experimental work was performed on the condition of sea water and in air to find out the characteristics of setting time between the concretes that were cast in air and cast in 15℃ of sea water. The experimental results show that the setting time of underwater concrete with 50% replacement was delayed about 10 hours than normal concrete. And it can be concluded that, at the case of underseawater concrete addicted with fly ash the delayed final setting times are shown as the function Tf=0.069F+7.69, where Tf is the delayed final setting time and F is quantity of fly ash respectively. These results confirm that the setting time of underseawater concrete could be prolonged.

유전자 알고리즘을 이용한 뼈대구조물의 이산최적화

김봉익(BONG-IK KIM),권중현(JUNG-HYUN KWON) 한국해양공학회 2002 韓國海洋工學會誌 Vol.16 No.4

This paper is to find optimum design of plane framed structures with discrete variables. Global search algorithms for this problem are Genetic Algorithms(GAs), Simulated Annealing(SA) and Shuffled Complex Evolution(SCE), and hybrid methods (GAs-SA, GAs-SCE). GAs and SA are heuristic search algorithms and effective tools which is finding global solution for discrete optimization. In particular, GAs is known as the search method to find global optimum or near global optimum. In this paper, reinforced concrete plane frames with rectangular section and steel plane frames with W-sections are used for the design of discrete optimization. These structures are designed for stress constraints. The robust and effectiveness of Genetic Algorithms are demonstrated through several examples.

하모니 서치 알고리즘과 고유진동수 제약조건에 의한 트러스의 단면과 형상 최적설계

김봉익(Bong-Ik Kim),권중현(Jung-Hyun Kwon) 한국해양공학회 2013 韓國海洋工學會誌 Vol.27 No.5

We present the optimum design for the cross-sectional(sizing) and shape optimization of truss structures natural frequency constraints. The optimum design method used in this paper employs continuous design variables and the Harmony Search Algorithm(HSA). HSA is a meta-heuristic search method for global optimization problems. In this paper, HSA uses the method of random number selection in an update process, along with penalty parameters, to construct the initial harmony memory in order to improve the fitness in the initial and update processes. In examples, 10-bar and 72-bar trusses are optimized for sizing and 37-bar bridge type truss and 52-bar(like dome) for sizing and shape. Four typical truss optimization examples are employed to demonstrate the availability of HSA for finding the minimum weight optimum truss with multiple natural frequency constraints.

유전자 알고리즘을 이용한 철근콘크리트 보의 단면 최적설계

김봉익(Bong-Ik Kim),권중현(Jung-Hyun Kwon) 한국해양공학회 2009 韓國海洋工學會誌 Vol.23 No.6

We present an optimum design method jar a rectangular reinforced concrete beam using Genetic Algorithms. The optimum design procedure in this paper employs 2 design cases: ⅰ) all of the design variables (b, d, As) of the rectangular reinforced concrete section are used pseudo-continuously, ⅱ) one is pseudo-continuous for the concrete cross section (b, d) and the other is discrete, using an index jar the steel area (As). The optimum design in this paper uses Chakrabarty's model. In this paper, the Genetic Algorithms use the method of Elitism and penalty parameters to improve the fitness in the reproduction process, which leads to very practical designs. The optimum design of the steel area in the examples uses ASTM standard reinforcing bars (#3#~11, #14, #18).

유전자 알고리즘을 이용한 트러스의 최적설계

김봉익(BONG-IK KIM),권중현(JUNG-HYUN KWON) 한국해양공학회 2003 韓國海洋工學會誌 Vol.17 No.6

Optimum design of most structural systems requires that design variables are regarded as discrete quantities. This paper presents the use of Genetic Algorithms for determining the optimum design for truss with discrete variables. Genetic Algorithms are known as heuristic search algorithms, and are effective global search methods for discrete optimization. In this paper, Elitism and the method of conferring penalty parameters in the design variables, in order to achieve improved fitness in the reproduction process, is used in the Genetic Algorithm. A 10-Bar plane truss and a 25-Bar space truss are used for discrete optimization. These structures are designed for stress and displacement constraints, but buckling is not considered. In particular, we obtain continuous solution using Genetic Algorithms for a 10-bar truss, compared with other results. The effectiveness of Genetic Algorithms for global optimization is demonstrated through two truss examples.