• 한국전산구조공학회논문집
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• 제19권4호
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• pp.337-345
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• 2006

본 연구에서는 개발된 중공단면 복합소재 교량 바닥판에 대해 피로거동을 평가하기 위하여 거더 지지부에서의 압축피로 시험과 2.8m 길이의 휨시험체 모델에 대한 휨피로시험을 수행하였다. 피로하중은 도로교설계기준의 제시된 DB24 트럭 후륜 축하중에 대해 200만회까지 반복 재하하였으며, 압축피로시험의 경우에는 복합소재 바닥판 부재와 바닥판 튜브간의 연결부에 대한 피로성능을, 휨피로시험의 경우에는 복합소재 바닥판 및 주형연결부에 대한 피로성능을 분석하였다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2008년도 추계 학술발표회 제20권2호
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• pp.993-996
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• 2008

콘크리트 구조물 설계에 사용되는 콘크리트 압축 응력블럭은 실제 응력분포를 등가의 삼각형, 직사각형, 사다리꼴 또는 포물선-직선 등 여러 형태로 나타낸 것이다. 이러한 콘크리트의 압축 응력블럭은 주요 선진국의 설계기준마다 그 형태가 조금씩 다르며, 각 나라 콘크리트의 재료적 특성을 반영하여 적용하고 있다. 현재, 우리나라 콘크리트 설계기준에 적용하고 있는 직사각형 압축 응력블럭은 ACI 설계기준과 동일한 형태이고, 이는 고강도 콘크리트의 재료적 특성을 반영하지 못하여 비합리적 이라는 여러 연구결과가 발표되어왔다. 본 연구는 주요 선진국의 설계기준에 적용되는 콘크리트 압축 응력블럭에 대해 검토하였으며, 우리나라 콘크리트의 재료적 특성을 알기 위해 콘크리트 압축 응력블럭 실험을 실시하였다. 실험을 통해 하중 및 변형률을 얻었으며, 실험 결과에 의한 응력블럭계수를 도출하였다. 실험에 의한 응력블럭계수와 주요 선진국의 설계기준에 적용하는 응력블럭계수 값들을 비교.분석하였다. 또한, 주요 설계기준의 응력블럭에 따른 공칭 축력-모멘트 상관도를 비교 분석하였다.

• Steel and Composite Structures
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• 제13권5호
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• pp.473-487
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• 2012

An experimental study was performed to investigate the seismic performance of steel reinforced concrete (SRC) special-shaped columns. For this purpose, 17 steel reinforced concrete special-shaped column specimens under low-cyclic reversed load were tested, load process and failure patterns of the specimens with different steel reinforcement were observed. The test results showed that the failure patterns of these columns include shear-diagonal compression failure, shear-bond failure, shear-flexure failure and flexural failure. The failure mechanisms and characteristics of SRC special-shaped columns were also analyzed. For different SRC special-shaped columns, based on the failure characteristics and mechanism observed from the test, formulas for calculating ultimate shear capacity in shear-diagonal compression failure and shear-bond failure under horizontal axis and oblique load were derived. The calculated results were compared with the test results. Both the theoretical analysis and the experimental results showed that, the shear capacity of T, L shaped columns under oblique load are larger than that under horizontal axis load, whereas the shear capacity of +-shaped columns under oblique load are less than that under horizontal axis load.

• 한국농공학회지
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• 제31권3호
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• pp.81-91
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• 1989

The aims of this study were to determine mechanical properties of steel-fiber reinforced concrete under splitting tensile, flexural and compressive loading, and thus to improve the possible applications of concrete. The major factors experimentally investigated in this study were the fiber content and the length and the diameter of fibers. The major results obtained are summarized as follows : 1.The strength, strain, elastic modulus and energy obsorption capability of steel-fiber reinforced concrete under splitting tensile loading were significantly improved by increasing the fiber content or the aspect ratio. 2.The flexural strength, central deflection, and flexural toughness of steel4iber reinforced beams were significantly improved by increasing the fiber content or the aspect ratio. And flexural behavior characteristic was good at the aspect ratio of about 60 to 75. 3.The strength, strain, and energy absorption capability in compression were increased with the increase of the fiber content. These effects were not so sensitive to the aspect ratio. The energy absorption capability was improved only slightly with the increase of the fiber length. 4.The elastic modulus, transverse strains, and poisson's ratios in compression were not influenced by the fiber content. 5.The steel-fibers were considered to be appropriated as the materials covering the weakness of concrete because the mechanical properties of concrete in tension and flexure were significantly improved by steel-fiber reinforcement.

• Earthquakes and Structures
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• 제18권4호
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• pp.451-466
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• 2020

In this paper, the effect of Engineered Cementitious Composites (ECC) on the lateral strength of a bearing unreinforced Masonry (URM) wall, was experimentally and numerically investigated. Two half scale solid walls were constructed and were tested under quasi-static lateral loading. The first specimen was an un-retrofitted masonry wall (reference wall) while the second one was retrofitted by ECC mortar connected to the wall foundation via steel rebar dowels. The effect of pre-compression level, ECC layer thickness and one or double-side retrofitting on the URM wall lateral strength was numerically investigated. The validation of the numerical model was carried out from the experimental results. The results indicated that the application of ECC layer increases the wall lateral strength and the level of increment depends on the above mentioned parameters. Increasing pre-compression levels and the lack of connection between the ECC layer and the wall foundation reduces the influence of the ECC mortar on the wall lateral strength. In addition, the wall failure mode changes from flexure to the toe-crashing behavior. Furthermore, in the case of ECC layer connected to the wall foundation, the ECC layer thickness and double-side retrofitting showed a significant effect on the wall lateral strength. Finally, a simple method for estimating the lateral strength of retrofitted masonry walls is presented. The results of this method is in good agreement with the numerical results.

• 한국생산제조학회지
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• 제21권3호
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• pp.421-424
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• 2012

Carbon Fiber reinforced composite material can be designed for the optimized performances of structural member that have achieve appropriate mechanical properties with cross-sectional shape, fiber direction, stacking sequence and thickness. So there are needed extensive databases each optimal design of CFRP structural member by impact through the preparation of different shape, interface number, thickness and stacking angle. When pressure is applied to structural member, compression, bending and torsion is shown on the corresponding member. For the effective utilization of fiber reinforced composite material as main structural member, optimized design technology should be established to maximize mechanical properties for compression, bending and torsion. In this paper, CFRP prepreg sheet with different stacking angle is manufactured in CFRP and hybrid(Al+CFRP) with circular cross-section. Strength and stiffness is gotten respectively by flexure test. CFRP structure and hybrid structure can be compared with each other. The best design guideline can be analyzed by use of this study result.

• Advances in Computational Design
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• 제8권2호
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• pp.113-131
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• 2023

The use of fibers has been commonly considered in engineered cementitious composites, but their behavior with coarse aggregate in concrete has not been studied significantly, which is needed to meet structural performance objectives for design, such as ductility. This research analyzes the behavior of fiber-reinforced concrete with coarse aggregate with 0.62%, 1.23%, and 2% PVA (Polyvinyl-alcohol) content, varying the maximum aggregate size. Tensile (direct and indirect) and compressive concrete tests were performed. The PVA fiber addition in coarse aggregate concrete increased the ductility in compression, especially for the fiber with a larger aspect ratio, with a minor impact on strength. In addition, the tensile tests showed that the PVA fiber increased the tensile strength of concrete with coarse aggregate and, more significantly, improved the ductility. A selected mixture was used to build short and slender reinforced concrete beams to assess the behavior of structural members. PVA fiber addition in short beams changed the failure mode from shear to flexure, increasing the deflection capacity. On the other hand, the slender beam tests revealed negligible impact with the use of PVA.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2008년도 춘계 학술발표회 제20권1호
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• pp.197-200
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• 2008

이전 연구에서 제안된 변형률 기반 전단강도모델을 휨-압축 부재에 적용하여, 프리스트레스트 콘크리트 보의 전단강도를 예측하기 위한 해석모델을 제안하였다. 전단보강 되지 않은 콘크리트 휨-압축 부재에서는 균열발생 이후, 일반적으로 인장대보다 콘크리트 압축대가 주로 전단력에 저항한다. 압축대 콘크리트의 전단성능은 콘크리트의 재료 파괴기준을 통해 정의된다. 그리고 압축대의 전단성능은 단면에 작용하는 수직응력과의 상관관계를 고려하여, 주응력방향에 의해 결정되는 파괴면을 따라서 산정된다. 압축대의 수직응력 분포는 부재의 휨변형에 따라 변화하므로, 압축대 단면의 전단성능은 휨변형에 대한 함수이다. 부재의 전단강도는 전단 성능 곡선과 수요 곡선의 교점에서 결정된다. 제안된 해석모델을 기존 연구자들의 실험 연구 결과와 비교한 결과, 실험체의 전단강도를 정확하게 예측하였다.

• Computers and Concrete
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• 제11권6호
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• pp.531-539
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• 2013

An experimental investigation of mechanical properties of jute fiber-reinforced concrete (JFRC) has been reported for making a suitable construction material in terms of fiber reinforcement. Two jute fiber reinforced concretes, called jute fiber reinforced normal strength concrete (JFRNSC) and jute fiber-reinforced high-fluidity concrete (JFRHFC), were tested in compression, flexure and splitting tension. Compressive, flexural and splitting tensile strengths of specimens were investigated to four levels of jute fiber contents by volume fraction. From the test results, Jute fiber can be successfully used for normal strength concrete (NSC) and high-fluidity concrete (HFC). Particularly, HFC with jute fibers shows relatively higher improvement of strength property than that of normal strength concrete.

• Structural Engineering and Mechanics
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• 제24권2호
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• pp.195-212
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• 2006

In seismic areas, ductility is an important factor in design of high strength concrete (HSC) members under flexure. A number of twelve HSC beams with different percentage of ${\rho}$ & ${\rho}^{\prime}$ were cast and incrementally loaded under bending. The effect of ${\rho}^{\prime}$ on ductility of members were investigated both qualitatively and quantitatively. During the test, the strain on the concrete middle faces, on the tension and compression bars, and also the deflection at different points of the span length were measured up to failure. Based on the obtained results, the serviceability and ultimate behavior, and especially the ductility of the HSC members are more deeply reviewed. Also a comparison between theoretical and experimental results are reported here.