• Title/Summary/Keyword: 콘크리트 구속효과

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Bond Strength of Grout-Filled Splice Sleeve Considering Effects of Confinement (구속효과를 고려한 모르타르 충전식 철근이음의 부착강도)

  • Kim, Hyong-Kee;Ahn, Byung-Ik
    • Journal of the Korea Concrete Institute
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    • v.15 no.4
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    • pp.615-622
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    • 2003
  • The purpose of this study is to propose the more reasonable equation of bond strength of grout-filled splice sleeve. To accomplish this objective, total 60 full-sized specimens were tested under monotonic loading. The experimental variables are compressive strength of mortar, embedment length and size of reinforcing bars. Following conclusions are obtained; 1) If the adequacy of existing equations which estimate the bond strength of grout-filled splice sleeve are investigated, they underestimate the bond strength of grout-filled splice sleeve by 8-18%. Also the existing equations have a tendency to underestimate with decrease in the embedment length of reinforcing bars. 2) From the test result of bond failure, the equation which estimates the confining pressure of grout-filled splice sleeve was proposed by making multiple regression analyses of which independent variables are embedment length of reinforcing bars and compressive strength of mortar. This equation predicted the measured bond capacity of this test more accurately than existing equations and eliminated the deviation according to the embedment length of reinforcing bars.

Modified Modulus of Elasticity of Concrete Column with Steel Bars (철근을 고려한 콘크리트 기둥의 수정탄성계수)

  • Yoon, Dong-Yong;Song, Hyung-Soo;Jang, Won-Seok;Min, Chang-Shik
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.9 no.1
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    • pp.101-111
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    • 2005
  • In this study, it is investigated the modified modulus of elasticity of the reinforced concrete columns including the longitudinal reinforcing steels as well as the confinement effect of the core concrete due to the transverse reinforced steel through the literature reviews. Equations are derived in order to evaluate the modified modulus of elasticity for the reinforced compressive concrete including the confinement effect. The finite element analysis for the 20 story reinforced concrete building is undertaken as a case study depending on the steel ratio and modulus of elasticity, and the analysis results are discussed.

A Study on the Strength Evaluation of Rectangular Steel Tubular Columns Infilled with High Strength Concrete (고강도콘크리트 충전 각형강관기둥의 내력평가에 관한 연구)

  • Shim, Jong Seok;Han, Duck Jeon
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.15 no.1
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    • pp.95-102
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    • 2011
  • The CFT columns used in thin-walled steel tubes can be more economical, because it was expected the increase of strength by restriction for the local buckling of steel tubes. The purpose of this paper is to review feasibility of existing design formula and verify the applicability limit of width-to-thickness ratio for increasing the strength of rectangular CFT columns. As the main parameters of experiments, width-to-thickness ratios of steel tube, height of rectangular concrete columns, and concrete filled or not. The strength of concrete are selected to 90MPa. From the test results, the confinement effect of steel tube on the compressive strength of infilled concrete is remarkably appeared in the thin-walled rectangular steel tube columns infilled wih high strength concrete. By the non-linear analysis, the axial strength from experiment result was given higher than analysis result for all CFT stub columns.

Axial Behavior of Concrete Cylinders Confined with FRP Wires (FRP 와이어 보강 콘크리트 공시체의 압축거동)

  • Cho, Baiksoon;Lee, Jong-Han;Choi, Eunsoo
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.33 no.5
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    • pp.1765-1775
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    • 2013
  • The application of FRP wire as a mean of improving strength and ductility capacity of concrete cylinders under axial compressive load through confinement is investigated experimentally in this study. An experimental investigation involves axial compressive test of three confining amounts of FRP wire and three concrete compressive strengths. The effectiveness of FRP wire confinement on the concrete microstructure were examined by evaluating the internal concrete damage using axial, circumferential, and volumetric strains. The axial stress-strain relations of FRP wire confined concrete showed bilinear behavior with transition region. It showed strain-hardening behavior in the post-cracking region. The load carrying capacity was linearly increased with increasing of the amount of FRP wire. The ultimate strength of the 35 MPa specimen confined with 3 layer of FRP wire was increased by 286% compared to control one. When the concrete were effectively confined with FRP wire, horizontal cracks were formed by shearing. It was developed from sudden expansion of the concrete due to confinement ruptures at one side while the FRP wire was still working in hindering expansion of concrete at the other side of the crack. The FRP wire failure strains obtained from FRP wire confined concrete tests were 55~90%, average 69.5%, of the FRP wire ultimate uniaxial tensile strain. It was as high as any other FRP confined method. The magnitude of FRP wire failure strain was related to the FRP wire effectiveness.

Strength and Deformation Capacities of Short Concrete Columns with Circular Section Confined by GFRP (GFRP로 구속된 원형단면 콘크리트 단주의 강도 및 변형 능력)

  • Cho, Soon-Ho
    • Journal of the Korea Concrete Institute
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    • v.19 no.1
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    • pp.121-130
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    • 2007
  • To investigate the enhancement in strength and deformation capacities of concrete confined by FRP composites, tests under axial loads were carried out on three groups of thirty six short columns in circular section with diverse GFRP confining reinforcement. The major test variables considered include fiber content or orientation, wrap or tube type by varying the end loading condition, and continuous or discontinuous confinement depending on the presence of vortical spices between its two halves. The circumferential FRP strains at failure for different types of confinements were also investigated with emphasis. Various analytical models capable of predicting the ultimate strength and strain of the confined concrete were examined by comparing to observed results. Tests results showed that FRP wraps or tubes provide the substantial increase in strength and deformation, while partial wraps comprising the vertical discontinuities fail in an explosive manner with less increase in strength, particularly in deformation. A bilinear stress-strain response was observed throughout all tests with some variations of strain hardening. The failure hoop strains measured on the FRP surface were less than those obtained from the tensile coupons in all tests with a high degree of variation. In overall, existing predictive equations overestimated ultimate strengths and strains observed in present tests, with a much larger scatter related to the latter. For more accuracy, two simple design- oriented equations correlated with present tests are proposed. The strength equation was derived using the Mohr-Coulomb failure criterion, whereas the strain equation was based on entirely fitting of test data including the unconfined concrete strength as one of governing factors.

Uniaxial Compression Behavior of Circular RC Columns Confined by Carbon Fiber Sheet Wraps (탄소섬유시트로 구속된 원형 RC기둥의 일축압축 거동)

  • Han, Sang Hoon;Hong, Ki Nam
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.11 no.2
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    • pp.125-133
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    • 2007
  • External confinement by CFS (Carbon Fiber Sheet) is a very effective retrofit method for the reinforced concrete columns subject to either static or seismic loads. For the reliable and cost-effective design of CFS, an accurate stress-strain curve is required for CFS-confined concrete. In this paper, uniaxial compression test on short RC column with circular section was performed. To evaluate the effect of confinement on the stress-strain relationship of CFS-confined concrete, CFS area ratio, spiral area ratio, and concrete compressive strength are considered as the test variables. Experiment results indicate that CFS jacketing significantly enhances strength and ductility of concrete. In addition, the CFS-jacketed specimens with the spiral steel show the lower load increasement ratio than those without the spiral steel.

Experimental Study on Mechanical Properties and Deformation Behavior of Concrete with Recycled Aggregates and Steel Fiber (순환골재 및 강섬유를 혼입한 콘크리트의 역학적 특성 및 변형 거동에 관한 실험적 연구)

  • Lee, Hyun-Ho;Lee, Tae-Wang
    • Journal of the Korea Concrete Institute
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    • v.28 no.3
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    • pp.357-363
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    • 2016
  • To solve the exhaustion problem of natural aggregate which were create the high value in construction and environmental industry, recycled aggregates have considerable benefits than other materials. However, even though many researches have been conducted with recycled aggregates, building structures with recycled aggregated are rarely constructed because it has lower quality than natural aggregates have. In this study, mechanical and strain properties of recycled aggregates concrete containing steel fibers have been reviewed in order to complement performance of recycled aggregates concrete. As results, recycled aggregates concrete showed lower compressive strength and elastic modulus than plain concrete. But, recycled aggregates concrete containing steel fibers showed equivalent performance with plain concrete. In review of drying shrinkage and creep coefficient, recycled aggregates concrete containing steel fibers showed similar behavior with plain concrete in the range of 0.5 Vol.% fiber content rate by internal restraint effect, moisture transport restraint effect and strength enhancement effect of steel fiber. Therefore, it is considered that mixing steel fibers with concrete is the effective method as a active application plan for recycled aggregates.

A Study on the Ductility of Concrete-Filled Composite Columns under Cyclic Loading (반복하중을 받는 콘크리트충전 강합성 기둥의 연성에 관한 연구)

  • 송준엽;권영봉;김성곤
    • Journal of the Earthquake Engineering Society of Korea
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    • v.5 no.6
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    • pp.11-19
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    • 2001
  • A series of test on concrete-filled composite columns was preformed to evaluate structural performance under axial compression and cyclic lateral loading. It was presented that concrete-filled composite columns had high strength, high stiffness and large energy-absorption capacity on account of mutual confinement between the steel plate and filled-in concrete. A cross section analysis procedure developed to predict the moment-curvature relation of composite columns was proven to be on accurate and effective method. The ductility factor and the response modification factor were evaluated for the seismic design of concrete-filled composite columns. It was shown that concrete-filled composite columns could be used as a very efficient earthquake-resistant structural member.

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Non-linear Behavior of New Type Girder Filled by High-Strength Concrete (신형식 거더의 고강도 콘크리트 적용 시 비선형 거동 분석)

  • Choi, Sung-Woo;Lee, Hak;Kong, Jung-Sik
    • Proceedings of the Korea Concrete Institute Conference
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    • 2008.04a
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    • pp.217-220
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    • 2008
  • Recently, many studies about a high-strength concrete and composite structures are being progressed to get the more economic and stable result in the construction of structure all over the world. One of those studies is about CFTA(Concrete Filled and Tied Steel Tubular Arch) girder that applies an arch structure and a pre-stressed structure to CFT(Concrete Filled Steel Tubular) Structure which is filled with a concrete and improve the stiffness and strength of the structure by the confinement effect of fillers to maximize the efficiency of structure and economic. In this study, non-linear behavior of CFTA girders filled with a general concrete and the high-strength concrete respectively were analyzed by using ABAQUS 6.5-1 and results were compared.

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Strength Characteristics of Square Concrete Column Confined by Carbon Composite Tube (탄소섬유튜브로 횡구속된 각형 콘크리트 기둥의 압축강도 성능에 관한 연구)

  • 홍원기;김희철;윤석한;박순섭
    • Journal of the Earthquake Engineering Society of Korea
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    • v.7 no.1
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    • pp.1-7
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    • 2003
  • The carbon composite tube can play an important role in replacing or complementing longitudinal and transverse reinforcing steels by providing ductility and strength for conventional columns. In this study, both the experimental and analytical investigations of axial behavior of large-scale square concrete columns confined by carbon composite tube are presented. The specimens are filament-wound carbon composite with 90$^{\circ}$+30$^{\circ}$, 90$^{\circ}$+45$^{\circ}$ winding angle respect to longitudinal axis of tube. The instrumented large-scale concrete-filled composite tubes(CFCT) are subjected to monotonic axial loads exerted by 10,000kN UTM. The influence of winding angle, thickness of tube on stress-strain relationships of the confined columns is identified and discussed. Proposed equations to predict both the strength and ductility of confined columns by carbon composite tube demonstrate good correlation with test data obtained from large-scale specimens.