• Title/Summary/Keyword: 휨 부재

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Design of Economical Steel Ratio in RC Flexural Members (RC 휨부재의 경제적 철근비 설계)

  • Jeong, Je Pyong;Lee, Chang Kee;Ryu, Heui Joong
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.35 no.1
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    • pp.93-99
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    • 2015
  • This paper is on a practical method for determination of the economical steel ratio in RC flexural members with an equal safety factor. The cost functions of each material and labor are considered to construct the cost function. Then, an equation for determination of the economical flexure steel ratio with the lowest construction cost were proposed. It was found that a relevant steel ratio is recommended to be 0.65~1.0% for designing singly reinforced rectangular beam.

Size Effect in the Fracture Behavior of Reinforced Concrete Members (철근콘크리트 부재의 파괴거동에 대한 크기 효과)

  • Kim, Dong-Baik;Kim, Woon-Hak;Paik, Shin-Won
    • Journal of the Korean Society of Safety
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    • v.13 no.4
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    • pp.292-299
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    • 1998
  • In this study, the size effect in flexural and shear behaviors of reinforced concrete beams with stirrup has been studied. The specimens of different size with same longitudinal reinforcement ratio are tested. The major variables of test include the size(relative depth) of the members as well as the longitudinal reinforcement ratios. The nominal resistances in flexure and shear are obtained for various sizes and steel ratios. It is found from the present study that the size effect is also very pronounced for the flexural resistance in reinforced concrete structures. The prediction formulas for the size effect of reinforced concrete beams in flexure and shear are proposed. The proposed equations agree relatively well with experimental data. The present study will provide useful bases for more accurate analysis and design of reinforced concrete structures.

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Effect of Tension, Compression and Lateral Reinforcement In Ductility Ratio in RC Flexural Members (철근콘크리트 휨 부재에서 인장, 압축 및 횡보강근이 연성률에 미치는 효과)

  • 연규원;박찬수
    • Journal of the Korea Concrete Institute
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    • v.13 no.6
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    • pp.553-560
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    • 2001
  • The ductility capacity should be estimated for inelastic analysis and design of reinforced concrete flexural members. Therefore, to estimate the ductility capacity, the model of moment-curvature relationship of reinforced concrete flexural member is assumed in this study. The curvature, rotation, and displacement(deflection) of reinforced concrete cantilever beams are analyzed and tested. The analytical results are compared with the test results. According to the analytical and test results, the assumed model of moment-curvature relationship in this study is adequate in flexural analysis of reinforced concrete members because the analytical results are well agreed with the test results, and it is resonable to express the ductility capacity in the rotation or displacement ductility, Because the curvature ductility is the limited index in a certain section. It is investigated that the ductility capacity is proportional to lateral reinforcement and compression reinforcement and inversely proportional to tension reinforcement.

A Study on the Evaluation Method to Flexural-bonding Behavior of FRP-Rebar Concrete Member (FRP를 보강근으로 사용한 콘크리트 부재의 휨-부착 거동 평가방법에 관한 연구)

  • Choi, So-Yoeng;Choi, Myoung-Sung;Kim, Il-Sun;Yang, Eun-Ik
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.25 no.5
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    • pp.149-156
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    • 2021
  • FRP has been proposed to replace the steel as a reinforcement in the concrete structures for addressing the corrosion issue. However, FRP-Rebar does not behave in the same manner as steel because the properties of FRP are different. For example, FRP-Rebar has a high tensile strength, low stiffness, and linear elastic behavior which results in a difference bonding mechanism to transfer the load between the reinforcement and the surrounding concrete. Therefore, bonding behavior between FRP-Rebar and concrete has to be investigated using the bonding test. So, Pull-out test has been used to estimate bond behavior because it is simple. However, the results of pull-out test have a difference with flexural-boding behavior of FRP-Rebar concrete member. So, it is needed to evaluate the real fleuxral-bonding behavior. In this study, the evaluation method to flexural-bonding behavior of FRP-Rebar concrete member was reviewed and compared. It was found that the most accurate evaluation method for the fleuxral-bonding behavior of FRP-Rebar concrete member was splice beam test, however, the size and length of specimen have to increase than other test method and the design and analysis of splice beam is complex. Meanwhile, characteristics of concrete could be reflected by using arched beam test, unlike hinged beam test which is based on the ignored change of moment arm length in equilibrium equation. However, the possibility of shear failure exists before the flexural-bonding failure occur.

Experimental Evaluation for Ultimate Flexural Behaviors of PSC beams with A Corroded Tendon (PS강연선이 부식된 PSC보의 극한휨거동 평가실험)

  • Youn, Seok-Goo
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.33 no.3
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    • pp.843-854
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    • 2013
  • This paper presents experimental research work for the evaluation of ultimate flexural behaviors of prestressed concrete beams with a corroded tendon. In order to evaluate the effects of loss of prestress or loss of tendon area on the ultimate flexural strength of prestressed concrete beams, static load tests are conducted using five prestressed concrete beams. After exposing prestressing tendons in two test beams using 25mm drill bit, the exposed tendons were corroded using an accelerating corrosion equipment to simulate loss of tendon area. During the tests, steel strains, concrete strains and displacements at the center of test beams were measured, and acoustic emission measurements were conducted to detect wire fractures. Based on the test results, evaluation method for predicting flexural strength of prestressed concrete beams with corroded tendons is investigated. In addition, evaluation methods for predicting the existence of corroded tendons in post-tensioned prestressed concrete beams at service loads are discussed.

Experimental Study on the Material Characteristics and Flexural Behavior of Ultra High-Strength Concrete (초고강도 콘크리트의 재료특성 및 휨 거동에 관한 실험적 연구)

  • 장영일;이호범;변근주
    • Magazine of the Korea Concrete Institute
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    • v.4 no.2
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    • pp.111-118
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    • 1992
  • 본 연구는 실리카흄을 혼화재료로 사용하여 1200kg/$ extrm{cm}^2$정도의 초고강도 콘크리트를 제조하였으며 이에 대한 재료특성을 실험 및 보부재의 휨거동을 실험을 실시 비교 분석하였다. 재료특성 실험으로는 기본적인 강도 시험, 파괴음 측정에 의한 AE실험 그리고 수은압입법에 의한 세공실험을 실시하였다. 초고강도 콘크리트의 재료특성치는 ACI 363의 고강도 콘크리트 재료특성 결가보다 크게 나타났으며 압축강도와 미세공극량은 선형적으로 비례하였다. 보부재의 휨특성을 파악하기 위해 인장철근비 변화, 전단보강근의 유무 및 철근 표면형상의 변화 등을 실험인자로 하였으며 각각의 현상을 비교분석함으로써 균열성상에 따른 하중-변위 관계, 중립축 이동에 따른 부재거동 및 응력블록의 변화에 관하여 비교 고찰하였다. 초고강도 콘크리트 사용한 보부재의 경우 중립축 상승으로 단면의 압축영역은 매우 작아져 급격히 압축파괴되는 경향을 보였으며 응력블록 형태는 삼각형의 분포를 보였다.

Flexural Performance Evaluation of HPFRCC Using Hybrid PVA Fibers (하이브리드 PVA 섬유를 이용한 HPFRCC의 휨 성능 평가)

  • Kim, Young-Woo;Min, Kyung-Hwan;Yang, Jun-Mo;Yoon, Young-Soo
    • Proceedings of the Korea Concrete Institute Conference
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    • 2008.11a
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    • pp.753-756
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    • 2008
  • HPFRCC (High-Performance Fiber Reinforced Cementitious Composites), which is relatively more ductile and has the characteristic of high toughness with high fiber volume fractions, can be used in structures subjected to extreme loads and exposed to durability problems. In the case of using PVA(polyvinyl alcohol) fibers, it is noted by former studies that around 2% fiber volume fractions contributes to the most effective performance at HPFRCC. In this study, therefore, compressive and flexural tests were implemented to evaluate the compressive and flexural capacities of HPFRCC while the total fiber volume fractions was fixed at 2% and two different PVA fibers were used with variable fiber volume fractions to control the micro-crack and macro-crack with short and long fibers, respectively. Moreover, specimens reinforced with steel and PVA fiber simultaneously were also tested to estimate their behavior and finally find out the optimized mixture. In the result of these experiments, the specimen consists of 1.6% short fibers (REC 15) and 0.4% long fiber (RF4000) outperformed other specimens. When a little steel fibers added to the mixture with 2% PVA fibers, the flexural capacity was increased, however, when high steel fiber volume fractions applied, the flexural capacity was decreased.

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Characteristics of Flexural Behaviors for Marine Concrete Members Using High-Durable Materials (고내구성 재료를 사용한 해양 콘크리트 부재의 휨 거동 특성)

  • Yang, Eun-Ik;Kim, Myung-Yu;Park, Hae-Geun;Lee, Dong-Gun
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.12 no.6
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    • pp.249-256
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    • 2008
  • The durability of marine concrete structure is severely degraded by corrosion due to penetration and diffusion of chloride. So, many researches have been performed to improve the durability in marine concrete structure. In this study, the concrete members mixed with the mineral admixtures(SF and BFS), the epoxy-coated steel, and corrosion inhibitors are prepared, and four-point bending test of specimens are performed to investigate the flexural behaviors and the applicability for marine concrete structure. From the test results, the mineral admixtures and inhibitors are useful for safety against the initial cracking and the bending resistance in specimens. When the durable material is used in specimen, the tensile stress of reinforcing rod was less variable in same bending span length, and the durable member showed a stable behavior. And it is evaluated that the crack spacing is not larger in specimen used the durable material.

Calculation for of Strength Reduction Factor for Concrete Beam reinforced with GFRP rebars (GFRP rebar로 보강된 콘크리트보의 휨 강도감소계수 보정식 제안)

  • Sim, Jong-Sung;Park, Cheol-Woo;Park, Sung-Jae;Kang, Tae-Sung;Kwon, Dong-Wook;Lee, Yong-Taek
    • 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.

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Nonlinear Analysis of Reinforced Concrete Flexural Members under Cyclic Loading (반복하중을 받는 철근콘크리트 휨부재의 비선형해석)

  • 변근주;김영진
    • Magazine of the Korea Concrete Institute
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    • v.3 no.3
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    • pp.149-157
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    • 1991
  • This paper concentrates on the nonlinear analysis of the reinforced concrete flexural members under cyclic loading. To develop a nonlinear material model, concrete is treated as an orthotropic nonlinear material and steel is modeled as an elasto-plastic material. The models for hysteresis behavior with stiffness degradation in compression and for crack opening and closing in tension are included. The finite element computer program for the nonlinear analysis of RC flexural members under cyclic loading is developed. The accuracy and reliabihty of the numerical procedure IS demonstrated by the FEM analysis and test results of underreinforced concrete beams.