파괴역학에 근거한 철근콘크리트 보의 휨 파괴거동

어석홍,이형진,최덕진 국립7개대학공동논문집간행위원회 2002 공업기술연구 Vol.2 No.-

An analytical fracture mechanics approach was used to investigate the fracture behavior of reinforced concrete beams. By use of this approach based on fracture mechanics concepts, the crack width and length as well as the strength and cracking stability of reinforced concrete beams were investigated. The results obtained from the analytical studies were also discussed in terms of the minimum reinforcement ratio and crack width specified in design code provisions. The analytical approach based on fracture mechanics concepts are very useful to predict the fracture behavior of reinforced concrete beams.

폐굴껍질을 혼입한 콘크리트의 기초적 성질에 관한 실험적 연구

어석홍,이형진,황규한 國立 昌原大學校 産業技術硏究所 2002 産技硏論文集 Vol.16 No.-

The purpose of this study is to investigate the fundamental properties of concrete mixed with crushed oyster shells(OS) as coarse or fine aggregates. For this purpose, five reference mixes with W/C ratios of 0.4∼0.6 at intervals of 0.05 were considered. The replacement proportion of OS was varied with ratios of 0, 10, 30, 50 and 100% by volume of fine or coarse aggregate in the reference mixes. OS was washed and crushed for using as aggregates. New chemical reaction between crushed OS aggregate and and cement paste was tested through XRD and SEM analysis. The compressive and flexural strength properties were considered. Strength tests were carried out at the ages of 1, 3, 7, 14, and 28 days. The variation of workanility, air content and density, drying shrinkage of the specimens with different proportions of OS were also studied. Finally, the hollow concrete block using OS as a substitute material for fine aggregate was made for testing the application of OS. Experimental results showed that any new chemical reaction did not occur due to mixing crushed OS in ordinary concrete. The workability and strengths decreased with increase in proportion of OS. The same trend was observed in density and unit weight, but air content increased due to the inherent shape and texture of OS, which showed a possibility to produce light weight concrete with low strength by using OS as coarse aggregates for concrete. Tests on hollow concrete block showed that the compressive strength and absorption ratio were satisfied with quality requirements when the fine aggregate was substituted with OS up to 50% in volume.

콘크리트 배합설계용 전문가 시스템의 개발

어석홍,허택녕,이석홍 산업기술연구소 1998 産技硏論文集 Vol.12 No.-

가상균열모델에 의한 고강도 콘크리트의 비선형파괴거동

魚碩泓 國立 昌原大學校 産業技術硏究所 1994 産技硏論文集 Vol.8 No.-

In this study, the mechanism of brittleness and fracture characteristics in high-strength concrete (HSC) have been investigated .For this purpose, a finite element numerical analysis using a bilinear fictitious crack model (FCM) was made for normal-strength concrete (NSC) and high-strength concrete (HSC) three-point bend specimens. The parameters of bilinear softening model were estimated through the mumerical simulation and comparison with the test results by Nomura et al. Fracture energy (G?) did not increase necessarily with increase in compressive strength (f?'). Tensile strength and crack opening displacement estimated showed increase and decrease respectively with increase in f?'. It is concluded that a reduction of bridging effect at mortar matrix-aggregate interface in HSC results in a more brittle fracture behavior than NSC.

재생골재를 사용한 콘크리트의 품질특성

어석홍,김희성,이형진 국립7개대학공동논문집간행위원회 2003 공업기술연구 Vol.3 No.-

The availability of natural aggregates has decreased in recent years due to depleting reserves. From the viewpoint of energy and resources saving, it may be advantageous to use the waste concrete as construction aggregates. Recently, recycled aggregate has been used for low-grade material such as concrete pavement. So in this study, authors examined the practical use of recycled aggregate for high-grade material such as structural aggregate. Several cases were selected for testing whether this is suitable or not. From outcome of these tests, it was found physical and chemical properties of recycled aggregate, compressive strength and mix proportion of concrete using recycled aggregate. The purpose of this study is to analyze physical and chemical properties of recycled aggregate, and to investigate the resistance of concrete to rapid freezing and thawing by using replacement ratios (0, 20, 40, 60, 80, 100%) of recycled aggregate.

고강도 콘크리트 보의 파괴특성과 크기효과

어석홍 산업기술연구소 1994 産技硏論文集 Vol.8 No.-

콘크리트구조물의 크기효과에 관한 JCI 국제워크숍

어석홍 한국콘크리트학회 1994 콘크리트학회지 Vol.6 No.1

고강도 콘크리트보의 파괴특성과 크기효과에 관한 수치해석

김희성,진치섭,어석홍 釜山大學校生産技術硏究所 1996 生産技術硏究所論文集 Vol.51 No.-

선형탄성파괴역학(LEFM) 및 파괴진행영역(FPZ)의 개념으로부터 유도한 크기효과법칙(SEL)에 따르면 콘크리트의 휨강도는 부재의 크기가 증가할수록 연속적으로 감소한다. 그러나, 초기노치가 없는 콘크리트보에 대한 실험결과에 의하면 콘크리트의 휨강도는 시편의 깊이가 증가함에 따라 우선 감소하다가 매우 큰 시편에서는 어느 일정한 값에 수렴하게 된다. 따라서, 본 연구에서는 2직선 가상균열모델(FCM)과 유한요소법(FEM)을 사용한 수치해석을 수행하여 초기균열 유무에 따른 보통강도 콘크리트(NSC)와 고강도 콘크리트(HSC)보의 파괴특성과 크기효과를 연구하였다. 수치해석 결과로부터 크기효과 모델식을 제안하였으며, Bazant의 제안식과 비교·분석하였다. 결론적으로, 고강도 콘크리트에 대한 파괴특성과 크기효과법칙을 구하기 위해서는 파괴에너지 및 연화거동 등을 고려하여야 함을 알 수 있었으며, 고강도 콘크리트에 대하여 보다 정확한 크기효과법칙을 정립하기 위하여 많은 실험 및 해석적 연구가 필요하리라 생각한다. Size effect laws(SEL) based on linear elastic fracture mechanics(LEFM) concepts, and fracture process zone(FPZ) modifications of that concept, predict that the flexural strength of plain concrete specimens decreases continuously as the specimen's depth increases. By contrast it is observed experimentally that while the flexural strength of unnotched specimens at first decreases as the specimen's depth increases, that strength subsequently reaches a limiting value for very large specimens. A finite element numerical analysis, using a bilinear fictitious crack model(FCM), was made to investigate fracture characteristics and size effect predictions for normal strength concrete(NSC) and high strength concrete(HSC) with and without an initial crack. Based on the numerical results, a simple size effect equation was proposed and compared with the predictions of equations proposed by Bazant. It is concluded that fracture energy and softening behavior need to be included in fracture characteristics and size effect laws for high strength concrete. Futhermore, physical tests and researches are needed to determine that size effect relationship for HSC.

객체지향기법을 이용한 콘크리트 배합설계 시스템의 개발

허택녕,어석홍 國立 昌原大學校 産業技術硏究所 1998 産技硏論文集 Vol.12 No.-

The objective in designing concrete mixtures is to determine the most economical and practical combination of readily available materials to produce a concrete that will satisfy the performance requirements under national and local site conditions of use. But it is very difficult to obtain optimal concrete mixtures considered various and local characteristics without an specialist's judgement and experiences. In this paper a concrete mixture proportioning system for normal concrete is developed using a object-oriented technique. Microsoft foundation Class is used for a object-oriented programming and Microsoft Access for database management. And primary classes for concrete mixture proportioning under the standard specifications of Korea concrete Institute, american Concrete Institute and British Standards are designed and windows programming with user graphic interface is accomplished. If the concrete mixture proportioning system is successively developed, it is expected that good mixture proportioning considered various conditions will be obtained without specialist's help or experience, and this system will be expanded to cover mixture proportioning of special concrete.

콘크리트용 골재로서 굴패각의 활용

어석홍(Seok-Hong Eo),황규환(Kyu-Han Hwang),김정규(Jeong-Gyu Kim) 한국콘크리트학회 2002 콘크리트학회논문집 Vol.14 No.4