• Structural Engineering and Mechanics
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• 제73권4호
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• pp.397-405
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• 2020

In this study size optimization of large-scale dome structures with dynamic constraints is presented. In the optimal design of these structure, the Jaya algorithm is used to find minimal size of design variables. The design variables are the cross-sectional areas of the steel truss bar elements. To take into account the constraints which are the first five natural frequencies of the structures, the finite element analysis is coded in Matlab programs using eigen values of the stiffness matrix of the dome structures. The Jaya algorithm and the finite elements codes are combined by the help of the Matlab - GUI (Graphical User Interface) programming to carry out the optimization process for the dome structures. To show the efficiency and the advances of the Jaya algorithm, 1180 bar dome structure and the 1410 bar dome structure were tested by taking into the frequency constraints. The optimal results obtained by the proposed algorithm are compared with those given in the literature to demonstrate the performance of the Jaya algorithm. At the end of the study, it is concluded that the proposed algorithm can be effectively used in the optimal design of large-scale dome structures.

• Corrosion Science and Technology
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• 제3권6호
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• pp.262-264
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• 2004

Ground Penetrating Radar (GPR) has been used to image inside concrete specimens embedded with steel bars and delamination. An imaging algorithm has been developed to improve measurement output generated from a commercial radar system. For the experiments, laboratory size concrete specimens are made with the dimensions of $1,000mm(W){\times}1,000mm(L){\times}250mm(D)$. The results have shown improved output of the radar measurements compared to commercially available processing methods.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1991년도 봄 학술발표회 논문집
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• pp.65-68
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• 1991

Finite element analysis is used to study the role of interfacial properties on the bond strength of reinforcing steel to concrete. Specifically, the role played by epoxy coatings on the failure of standard beam-end specimens is explored. Experimental results show that epoxy coatings reduce bond strength, but that the effect is dependent on the bar size and the deformation pattern. The finite element model for the beam-end specimen includes representations for the deformed steel bar, the concrete, and the interfacial material. The interface elements can be varied to match the stiffness and friction properties of the interfacial material. Cracking within the concrete is represented using Hillerborg's ficticious crack model. The model is used to study important aspects or behavior observed in the tests and to provide an explanation for the effect of the various test parameters.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2003년도 봄 학술발표회 논문집
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• pp.367-372
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• 2003

Fiber Reinforced Cementitious Composite, DFRCC has strain hardening property with multiple crack in failed of compressive, tensile, bending force, concrete is not so that. But DFRCC could not use to the building element for which has not structural stiffness only has ductile property. DFRCC is used for repair only in recently. In that reason, we considered the concrete of light weight concrete, porous concrete, mortar complex with DFRCC. and DFRCC reinforced by fiber net, steel bar. In this study, results of experiment on complex method of concrete and DFRC were shown as follows; The complex methods of concrete lay on DFRCC, sandwich layer composition were effective for bending force depending on section size each layer, and reinforce DFRCC by fiber net, steel bar was effective method also.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1996년도 가을 학술발표회 논문집
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• pp.127-132
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• 1996

Recently in the country a corrosion of steel is accelerated due to using of sea sand including salts, and critical problem on the durability of concrete structure is occured. Thus a control of steel corrosion is very important in the stability of structure. Coated steel is in use with a method of steps of steel corrosion in U.S,A. Japan etc, and as well in domestic case the manufactured coating steel of three types is on the market. Those are Epoxy coated steel, Zinc-strength, concrete specimen size, bar diameter, which can affect bond characteristics between steel and concrete in order to know their relative bond characteristics.

• 한국산학기술학회논문지
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• 제18권12호
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• pp.118-125
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• 2017

본 논문은 FRP Hybrid Bar의 최적 부착 성능 도출을 위한 실험 결과를 나타낸다. FRP Hybrid Bar는 이형 철근의 부식문제를 해결하기 위하여 이형 철근 외측에 유리섬유를 감싸 만들어졌다. 콘크리트와의 부착 성능 향상을 위해 매끈한 FRP Hybrid Bar 표면에 수지와 규사를 이용하여 코팅하였고 수지의 종류 및 점도, 그리고 규사의 크기를 실험 변수로 하여 FRP Hybrid Bar의 부착 성능을 실험적으로 평가하였다. FRP Hybrid Bar의 부착 성능 평가를 위해 한 변의 길이가 200 mm인 정육면체 콘크리트 블록에 FRP Hybrid Bar를 매립하였고, 인발 실험을 통하여 FRP Hybrid Bar와 콘크리트의 계면에서의 최대 하중과 슬립을 측정하였다. 실험 결과로부터, 각 실험 변수에 따른 최대 하중 및 부착 강도를 산정하였고 FRP Hybrid Bar의 부착 성능이 가장 우수한 수지 종류 및 점도, 그리고 규사 크기를 도출하였다. 에폭시 수지와 5호 규사를 사용한 실험체의 최대부착강도는 이형철근의 최대부착강도 대비 약 35% 정도 증가되었다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1991년도 봄 학술발표회 논문집
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• pp.105-110
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• 1991

The conventional high-frequency testing method is difficult to detect flaw in concrete because the high frequency stress wave is strongly attenuated due to the large grain size and heterogeneous structure. For restoration of this problem, we develop the stu요 of flaw detection in large concrete block containing various artificial flaws by low frequency spectrum anlysis of impact-echo waveforms. This impact-echo testing method is possible to determine the flaw size, shape and location in large concrete block even if required some attention in case of containing reinforcing steel bar.

• Computers and Concrete
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• 제18권3호
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• pp.337-354
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• 2016

To study the influence on fracture properties of reinforced concrete wedge splitting test specimens by the addition of reinforcement, and the restriction of steel bars on crack propagation, 7 groups reinforced concrete specimens of different reinforcement position and 1 group plain concrete specimens with the same size factors were designed and constructed for the tests. Based on the double-K fracture criterion and tests, fracture toughness calculation model which was suitable for reinforced concrete wedge splitting tensile specimens has been obtained. The results show that: the value of initial craking load Pini and unstable fracture load Pun decreases gradually with the distance of reinforcement away from specimens's top. Compared with plain concrete specimens, addition of steel bar can reduce the value of initial fracture toughness KIini, but significantly increase the value of the critical effective crack length ac and unstable fracture toughness KIun. For tensional concrete member, the effect of anti-cracking by reinforcement was mainly acted after cracking, the best function of preventing fracture initiation was when the steel bar was placed in the middle of the crack, and when the reinforcement was across the crack and located away from crack tip, it plays the best role in inhibiting the extension of crack.

• 대한토목학회논문집
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• 제37권3호
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• pp.521-529
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• 2017

본 연구에서는 합성형교와는 다른 전단연결 상세를 가지는 콘크리트 비충전 강합성 바닥판의 유효폭을 수치적으로 분석하였다. 유효폭 산정 방법 및 위치, 작용하중 크기, 메인 베아링 바 간격-지간장비에 따른 콘크리트 비충전 강합성 바닥판의 유효폭을 평가하였다. 분석 결과 응력 형태를 사다리꼴로 이상화하여 유효폭을 산출하여도 실제 유효폭과 거의 동일한 것으로 분석되었다. 또한, 전단 강도 증가를 위해 적용된 전단홀 관통 철근이 유효폭을 증가 시키는 역할을 하는 것으로 나타났다. 메인 베아링 바 간격-지간장비에 따른 유효폭 분석 결과로부터 콘크리트 비충전강합성 바닥판의 유효폭비를 산출 할 수 있는 보정 계수를 제안하였다.

• 화약ㆍ발파
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• 제25권1호
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• pp.53-65
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• 2007

축소모형을 이용한 철근콘크리트 구조물 발파해체 시 구조물의 붕괴거동을 분석하기 위해서는 축소모형 부재에 대한 적절한 축소율 산정과 축소모형 부재를 구성하는 재료의 역학적 특성이 원형 철근콘크리트 부재와 상사되어야 한다. 본 연구에서 축소모형의 상사법칙은 밀도를 기준으로 산정하였고, 콘크리트 표준시방서와 콘크리트 구조설계기준에 의해 축소모형 철근콘크리트의 배합 및 배근을 기술하였다. 또한 축소모형 콘크리트의 축소율은 굵은골재 최대치수를 고려하여 부재 단면 길이를 1/5로 축소하였고, 축소모형 철근의 축소율은 공칭지름을 1/5로 축소하였다. 축소모형에 대한 역학적 실험결과로부터 제안된 상사법칙을 적용함으로써 축소모형 콘크리트의 평균압축강도 및 축소모형 철근의 평균항복강도가 상사관계를 가지는 것으로 나타났다.