• 콘크리트학회논문집
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• 제22권2호
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• pp.199-208
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• 2010

FRP bar를 철근 대체제로 활용하기 위해서는 설계 기준의 확립이 시급하나 국내에서는 이 소재에 대한 기초 연구가 부족한 상황이다. 그러므로 2차에 걸쳐 전단보강이 없는 18개의 FRP RC와 4개의 기존 RC 실험체의 거동을 관찰하였다. 1차 실험은 휨 파괴 거동과 사용성 항목의 계측 자료 수집을 목적으로 시작되었다. 휨파괴를 유도하기 위하여 전단배근을 강화하는 대신 그로 인한 거동의 불확실성을 배제하기 위하여 전단지간비만을 조정하여 휨파괴를 유도하고, 전단배근을 사용하지 않기로 하였다. 실험 결과 거의 모든 실험체는 전단파괴 되었으며 실험계획에 적용한 ACI 440.1R과 CSA S806의 전단 강도식이 실제와 큰 편차가 있음을 확인하였다. 1차 실험의 결과를 근거로 2차 실험에서는 전단파괴거동을 집중적으로 관찰하였다. 표준 실험체의 제원은 길이 3,300 mm폭 ${\times}$ 800 mm ${\times}$ 유효깊이 200 mm, 순지간 2,800 mm, 전단지간 1,200 mm로 전단지간비는 6.0이며, 단순지지 조건으로 4점 재하실험을 수행하였다. 검토 변수에는 콘크리트 압축강도, 보강근의 종류 및 탄성계수, 전단지간비, 유효보강비, 다발 배근의 영향, 피복두께의 영향이 포함된다.

• 콘크리트학회논문집
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• 제19권2호
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• pp.241-250
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• 2007

폭발하중을 받는 콘크리트 구조물을 섬유 복합재 등의 보강 재료를 사용하여 보강하는 경우에는 강성 증가와 함께 적절한 연성을 확보할 수 있어야 한다. 그러나, 폭발하중을 받는 구조물의 설계 및 해석에 일반적으로 사용되는 기존의 근사적이며 단순화 모델은 보강 재료에 대한 효과를 정확히 반영할 수 없을 뿐 아니라 해석 결과의 정확성 및 신뢰성에 문제가 제기되어왔다. 또한, 동적 하중에 대한 콘크리트와 철근의 응답은 정적 하중에 대한 응답과 상이하기 때문에 기존의 정적, 준정적하에서 정의된 재료물성값들을 폭발하중에 대한 응답 계산에 사용하는 것은 부적절하다. 따라서, 본 연구에서는 명시적(explicit) 해석 프로그램인 LS-DYNA를 사용하여 매우 빠른 재하속도를 갖는 폭발하중에 대하여 강도 증진 및 변형률 속도 효과가 반영된 재료 모델을 포함하고 있는 정밀 HFPB(high fidelity physics based) 유한요소해석 기법을 제시하였다. 제시된 해석적 기법을 통하여 탄소섬유 복합재와 유리섬유 복합재를 사용하여 보강된 콘크리트 벽체의 폭발하중에 대한 거동을 해석하였으며, 이를 보강하지 않은 벽체의 해석 결과와 비교함으로써 보강 성능 분석을 실시하였다. 해석 결과 보강에 따른 최대 처짐이 약 $26{\sim}28%$ 감소하는 보강 성능을 확인하였으며, 제안된 해석 기법이 보강 재료와 보강 기법의 유효성을 평가하는데 효과적으로 적용할 수 있을 것으로 판단된다.

• International Journal of Concrete Structures and Materials
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• 제18권1E호
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• pp.55-61
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• 2006

RC shear walls are frequently used as lateral force-resisting system in building construction because they have sufficient stiffness and strength against damage and collapse. If RC shear walls are properly designed and proportioned, these walls can also behave as ductile flexural members like cantilevered beams. To achieve this goal, the designer should provide adequate strength and deformation capacity of shear walls corresponding to the anticipated deformation level. In this study, the level of demands for deformation of shear walls was investigated using a displacement-based design approach. Also, deformation capacities of shear walls are evaluated through laboratory tests of shear walls with specific transverse confinement widely used in Korea. Four full-scale wall specimens with different wall boundary details and cross-sections were constructed for the experiment. The displacement-based design approach could be used to determine the deformation demands and capacities depending on the aspect ratio, ratio of wall area to floor plan area, flexural reinforcement ratio, and axial load ratio. Also, the specific boundary detailing for shear wall can be applied to enhance the deformation capacity of the shear wall.

• Smart Structures and Systems
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• 제21권4호
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• pp.521-535
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• 2018

The main purpose of this paper is to predict missing absolute out-of-plane displacements and failure limits of infill walls by artificial neural network (ANN) models. For this purpose, two shake table experiments are performed. These experiments are conducted on a 1:1 scale one-bay one-story reinforced concrete frame (RCF) with an infill wall. One of the experimental models is composed of unreinforced brick model (URB) enclosures with an RCF and other is composed of an infill wall with bed joint reinforcement (BJR) enclosures with an RCF. An artificial earthquake load is applied with four acceleration levels to the URB model and with five acceleration levels to the BJR model. After a certain acceleration level, the accelerometers are detached from the wall to prevent damage to them. The removal of these instruments results in missing data. The missing absolute maximum out-of-plane displacements are predicted with ANN models. Failure of the infill wall in the out-of-plane direction is also predicted at the 0.79 g acceleration level. An accuracy of 99% is obtained for the available data. In addition, a benchmark analysis with multiple regression is performed. This study validates that the ANN-based procedure estimates missing experimental data more accurately than multiple regression models.

• Steel and Composite Structures
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• 제18권4호
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• pp.925-946
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• 2015

This paper presents a new cost-effective hybrid GFRP-Concrete deck system that the GFRP panel serves as both tensile reinforcement and stay-in-place form. In order to understand the fatigue behavior of such hybrid deck, fatigue test on a full-scale specimen under sagging moment was conducted, and a series of static tests were also carried out after certain repeated loading cycles. The fatigue test results indicated that such hybrid deck has a good fatigue performance even after 3.1 million repeated loading cycles. A three-dimensional finite element model of the hybrid deck was established based on experimental work. The results from finite element analyses are in good agreement with those from the tests. In addition, flexural fatigue analysis considering the reduction in flexural stiffness and modulus under cyclic loading was carried out. The predicted flexural strength agreed well with the analytical strength from finite element simulation, and the calculated fatigue failure cycle was consistent with the result based on related S-N curve and finite element analyses. However, the flexural fatigue analytical results tended to be conservative compared to the tested results in safety side. The presented overall investigation may provide reference for the design and construction of such hybrid deck system.

• Smart Structures and Systems
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• 제3권4호
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• pp.475-494
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• 2007

This paper deals with the development of an innovative distributed construction system based on smart prefabricated concrete elements for the real-time condition assessment of civil infrastructure. So far, two reduced-scale prototypes have been produced, each consisting of a $0.2{\times}0.3{\times}5.6$ m RC beam specifically designed for permanent instrumentation with 8 long-gauge Fiber Optic Sensors (FOS) at the lower edge. The sensing system is Fiber Bragg Grating (FBG)-based and can measure finite displacements both static and dynamic with a sample frequency of 625 Hz per channel. The performance of the system underwent validation in the laboratory. The scope of the experiment was to correlate changes in the dynamic response of the beams with different damage scenarios, using a direct modal strain approach. Each specimen was dynamically characterized in the undamaged state and in various damage conditions, simulating different cracking levels and recurrent deterioration scenarios, including cover spalling and corrosion of the reinforcement. The location and the extent of damage are evaluated by calculating damage indices which take account of changes in frequency and in strain-mode-shapes. The outcomes of the experiment demonstrate how the damage distribution detected by the system is fully compatible with the damage extent appraised by inspection.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2017년도 춘계 학술논문 발표대회
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• pp.165-166
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• 2017

Corrosion of reinforcement is the main factors affecting the durability of reinforced concrete in the world which lead to the failure of structures of reinforced concrete buildings. In this research, mixed brucite(Mg(OH)₂) into ordinary portland cement paste in ratio of 5, 10 and 15% as a kind of CO₂ fixation material. Samples were exposed to an accelerated carbonation enslavement of 20% CO₂ concentration, 60% relative humidity, and a temperature of 20℃ until tested at 3d, 7d, 14d and 28d. After 28d CO₂ accelerated curing, in the paste containing MH megnesian calcite was found by XRD and SEM-EDX. Meanwhile, paste containing Mg(OH)₂ exhibit the better pore distribution than ordinary portland cement paste and relatively good compressive strength.

• 한국산학기술학회논문지
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• 제13권5호
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• pp.2396-2402
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• 2012

최근 영구거푸집과 보강재 역할을 동시에 하는 FRP-콘크리트 합성부재에 관한 연구가 많이 진행되고 있으며, 일부에서는 실제 교량바닥판에 적용되고 있다. 본 연구에서는 파괴실험으로 평가한 퍼포본드 FRP 콘크리트 합성보에 대해 비선형 유한요소해석 프로그램을 활용하여 검증해석을 실시하고, 이를 이용하여 FRP 보강재 형상에 따른 매개변수 해석을 수행하였다. 퍼포본드 FRP 보강재의 경우 다우웰 영향으로 내력이 증가하는 양상이 나타났고, 본 해석모델을 중심으로 판단하면 웨브의 높이를 고려하여 25~35mm 범위에서 구멍직경을 결정하는 것이 바람직하다고 판단된다.

• Computers and Concrete
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• 제1권2호
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• pp.211-226
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• 2004

A relatively simple multiple-vertical-line-element macro model has been incorporated into a standard computer code DRAIN-2D. It was used in blind predictions of seismic response of cantilever RC walls subjected to a series of consequent earthquakes on a shaking table. The model was able to predict predominantly flexural response with relative success. It was able to predict the stiffness and the strength of the pre-cracked specimen and time-history response of the highly nonlinear wall as well as to simulate the shift of the neutral axis and corresponding varying axial force in the cantilever wall. However, failing to identify the rupture of some brittle reinforcement in the third test, the model was not able to predict post-critical, near collapse behaviour during the subsequent response to two stronger earthquakes. The analysed macro model seems to be appropriate for global analyses of complex building structures with RC structural walls subjected to moderate/strong earthquakes. However, it cannot, by definition, be used in refined research analyses monitoring local behaviour in the post critical region.

• 한국전산구조공학회논문집
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• 제24권2호
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• pp.201-210
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• 2011

이 연구에서는 깊은보-내부기둥 접합부의 내진성능평가를 위한 비선형 유한요소해석 기법을 제시하였다. 사용된 프로그램은 철근콘크리트 구조물의 해석을 위한 RCAHEST이다. 깊은보-내부기둥 접합부의 강도, 연성도 등 거동특성을 파악하기 위한 반복횡하중 실험을 수행하였다. 실험의 변수로는 축력과 횡방향 철근량을 정하였다. 이 연구에서는 깊은보-내부기둥 접합부의 내진성능평가를 위해 제안한 해석기법을 신뢰성 있는 실험결과와 비교하여 그 타당성을 검증하였다.