• 한국방재학회:학술대회논문집
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• 2010.02a
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• pp.83.1-83.1
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• 2010

본 연구는 고강도 강재를 적용한 연속교 형식의 강교량에 대하여 연구를 수행하였다. 교량에 사용되는 주구조의 고강도화에 따로 연속교의 교각 부근 부모멘트부에는 정모멘트부에 비하여 큰 모멘트가 작용하게 된다. 또한 정모멘트 구간과 달리 상부플랜지에 인장력이 작용하게 되어 완공 후에도 극한 하중 상태에서 콘크리트 데크가 응력을 부담할 수 없게 된다. 이에 따라 하부 플랜지에 불안정 파괴가 발생할 가능성이 있으며 비합성 단면과 같은 방법으로 설계하게 된다. 또한 모멘트 재분배를 고려한 설계를 하기 위해서는 부모멘트부에 충분한 휨 연성이 필요하다. 고강도 강재를 적용한 교량은 일반강재를 적용한 교량에 비하여 휨연성이 감소하게 되므로 휨연성 확보를 위한 보강방안이 필요하다. 본 연구는 부모멘트부의 휨연성 향상을 휘하여 가로보의 부등 배치를 제안하였으며, 유한요소해석 결과 휨연성이 향상되었다.

• Journal of Korea Foresty Energy
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• v.22 no.1
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• pp.44-48
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• 2003

Flexural properties were investigated on clear specimens made from small diameter thinned trees of pitch pine (Pinus rigida Mill.), Japanese red pine (Pinus densiflora Sieb. et Zucc), Japanese larch (Larix kaempferi Carr.), and sawtooth oak (Quercus acutissima Carr.). MOR and MOE values of small clear specimen were depended on the species. The highest density of sawtooth oak shows the highest values of MOR and MOE. However, the lowest density of Japanese larch shows the lowest values of MOR. It was also shown that flexural properties could be predicted by stress wave MOE, since the correlations between stress wave MOE and flexural properties were relatively good.

• Magazine of the Korea Concrete Institute
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• v.9 no.6
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• pp.207-216
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• 1997

본연구는 축방향 변형 구속이 고강도 콘크리트 휨부재의 휨 전단거동에 미치는 영향을 조사하기 위한 것으로, 수화열과 건조수축에 기인하는 축방향 변형과 재하에 의한 축방향 변형을 구속한 부재 및 무구속 부재에 대하여 휨파괴와 전단파괴 실험을 실시하였다. 타설 직후부터 축변형을 구속한 실험체의 재하시 강성은 재하전의 구속으로 발생한 관통균열의 영향을 받아 무구속 실험체의 강성보다 낮지만, 재하시의 축변형 구속에 따른 압축구속력의 상승으로 인하여 강성의 크기는 역전되었다 축변형이 완전히 구속된 휨부재의 휨강도는 무구속 부재보다 20%이상 상승하지만 변형능력은 감소하는 것으로 나타났으며, 재하전의 축변형 구속에 의한 관통균열(균열폭 0.1mm 미만)은 부재의 전단내력 및 전단균열 진전 형상에 영향을 미치지 않았다.

• Computational Structural Engineering
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• v.7 no.2
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• pp.11-15
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• 1994

본 고에서는 축대칭회전 Shell을 해석모델로 선정하여 주로 Shell의 휨 강성이 구조체의 거동에 미치는 영향에 대하여 검토하였다. 어떠한 구조형식이든 외력의 작용하에서 발생되는 응력이 축방향력 뿐이라는 것은 상당히 합리적이고 역학적으로도 명쾌한 동시에, 실제 설계상 이상적인 판단기준을 부여하지만, 실제로는 필히 휨상태를 수반하게 된다. 이러한 휨상태는 구성요소의 휨강성에 크게 의존하고 있고, 구조체에 어느정도의 휨강성을 부여하므로써 작용하중에 대한 저항능력의 증가, 변형 및 응력의 저감에 효과적이라는 것을 알 수 있다. 본 고에서는 등방성 Shell에 대한 선형 해석결과만을 게재하였으나, 이러한 성상은 여러가지 영향인자(지지조건, 하중상태 등)에 따라 아주 상이하게 나타나기 때문에 세심한 고찰이 필요하다고 할 수 있다.

• Journal of the Korean Recycled Construction Resources Institute
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• v.6 no.2
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• pp.138-145
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• 2018

This paper studies the bending behavior of ultra-high-performance fiber-reinforced concrete (UHPFRC) beams focused on the effect of variation in major material design parameters such as tensile strength, elastic modulus of UHPFRC, and rebar ratio. Analytical results show that the variation in the range of ${\pm}20%$ in the tensile strength of UHPFRC causes the significant difference in ${\pm}8{\sim}9%$ of bending strength compared to the reference condition. The variation of elastic modulus in UHPFRC rarely causes the effect on the bending strength of the UHPFRC section, whereas causes the difference in the slopes of moment-curvature curves, indicating different bending stiffness of UHPFRC sections. For the rebar with yield strength of 400MPa, the bending strength of SC120f is increased by 30, 67, and 99% when the rebar ratio is 1.0, 1.5, and 20%, respectively, compared to the rebar ratio of 0.5%. Therefore, it is observed that the variation of rebar ratio significantly affects the difference in bending strength of UHPFRC beams. However, as the compressive strength of UHPFRC becomes greater, the effect of rebar ratio on the increase of bending strength is decreased.

• Land and Housing Review
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• v.12 no.4
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• pp.119-125
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• 2021

The study presents the ductility reinforcement effect of the RC bending member using the CFRP Grid as an experimental result. Experimental variables include a non-reinforced RC bending member (ORI), a bottom reinforced RC bending member (REB), and an RC bending member reinforced at the bottom and side (REBS). The experiment was carried out with four points bending test. As a result of the experiment, it was confirmed that the maximum bending strength increased by 17-20% through reinforcement. In addition, the ductility index calculation results confirmed that the ductility index of REB and REBS increased by 2 and 3 times, respectively, compared to the ORI.

• Journal of the Korea Concrete Institute
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• v.26 no.4
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• pp.483-489
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• 2014

In this study, the flexural test of amorphous steel fiber-reinforced concrete was performed according to ASTM C 1609 to investigate its flexural performances. The amorphous steel fibers have different configurations from conventional steel fibers : thinner sections and coarser surfaces. Primary test parameters are fiber type (amorphous and conventional steel fibers), concrete compressive strength (27 and 50 MPa), and fiber volume fraction (0.25, 0.50, and 0.75%). Based on the test results, flexural strength and flexural toughness of the amorphous and conventional steel fiber-reinforced concrete were investigated. The results showed that the addition of the amorphous steel fibers into concrete could enhance both flexural strength and toughness while the addition of the conventional steel fibers into concrete was mainly effective to increase the flexural toughness.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.137-140
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• 2008

If the flexural member of concrete is designed using the FRP rebar, suddenly brittleness destruction resulted from the fracture of FRP rebar is generated in the extreme situation because of brittleness characteristics of FRP rebar and concrete when designed to be less than balanced reinforcement ratio, so it is recommended to design the flexural member of concrete to be more than balanced reinforcement ratio. In ACI 440.1R-06 proposes the different bending strength decrease coefficient according to destructive form of concrete flexural member using the FRP rebar. However, ACI 440.1R-06 applies the same strength decrease coeffient to all FRP rebars made of diverse materials. If the same strength decrease coefficient is applied to all FRP rebars, effect of increasing the reinforcement ratio and selection of FRP rebar will be considerably limited. In this regard, we are to propose the formula to calculate the bending strength decrease coefficient in consideration of change in characteristics of FRP rebar and L/D through the reliability analysis in this paper.

• Journal of the Korea Concrete Institute
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• v.20 no.4
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• pp.531-539
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• 2008

The purpose of this study is to investigate the mechanical properties of high strength concretes reinforced with hooked steel fiber. For this purpose, total 36 specimens whose variables are concrete compressive strength, steel fiber aspect ratio, and steel fiber volume contents, are made and tested. From the test results including previous research work, flexural performance of steel fiber reinforced high strength concrete is evaluated in terms of flexural strength and toughness index. Flexural behavior of steel fiber reinforced high strength concrete is enhanced with respect to the fiber volume content, the aspect ratio, and concrete compressive strength. More efforts are devoted to evaluate quantitatively between the flexural strength and the structural parameters such as the fiber volume content, the aspect ratio, and concrete compressive strength.

• Journal of the Korea institute for structural maintenance and inspection
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• v.17 no.4
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• pp.38-47
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• 2013

For the joint connection of the precast steel grid composite decks, the prefabricated joint which is composed of concrete shear key and high-tension bolts was already proposed. In this study, for the purpose of increasing the bending stiffness and bending strength of the proposed prefabricated joint section details of the proposed joint are modified, and through experimental tests the bending performance, such as stiffness and strength of a modified joint, is compared with those of the proposed joint. Test and analysis results show that the shear cracks in the concrete shear key are clearly reduced by the strengthening of the shear key using shear studs and additional rebars. According to analysis results of the moment-curvature relationship, bending stiffness of the modified joint is about 47% greater than the stiffness of the proposed joint. Furthermore, the modified joint has about 32% greater bending strength than the proposed joint. Compared to specimens without the joint the modified joint has same or slightly higher bending strength, but about 37% lower bending stiffness.