• 제목/요약/키워드: restrained concrete

검색결과 203건 처리시간 0.025초

초속경 라텍스개질 콘크리트의 초기수축 및 구속건조수축 (Early-Age and Restrained Shrinkage of Very-Early Strength Latex Modified Concrete)

  • 최판길;김용곤;심도식;이봉학
    • 산업기술연구
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    • 제25권A호
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    • pp.49-56
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    • 2005
  • Recently, very-early strength latex-modified concrete(below ; VES-LMC) has been developed for repairing and overlaying the old concrete bridge deck. VES-LMC provides the advantage of very-early-strength, as well as high flexural strength, bond strength, durability, resistance to corrosion, reduced water permeability and resistance to damage from freeze-thaw cycles. The compressive and flexural strength of VES-LMC are 21 MPa and 4.5 MPa at 3 hours after concrete placing, respectively. However, VES-LMC would have a relatively large shrinkage at early-age because of reduced water-cement ratio, big water self-dissipation, and rapid hydration reaction. Therefore, the purpose of this study was to evaluate the early-age and restrained shrinkage of VES-LMC, having an experimental variables such as latex contents and cement types. The latex contents included 0%, 5%, 10%, 15% and 20%, and the cement types included ordinary portland cement and very-early strength cement.

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Experimental Study on Tensile Creep of Coarse Recycled Aggregate Concrete

  • Seo, Tae-Seok;Lee, Moon-Sung
    • International Journal of Concrete Structures and Materials
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    • 제9권3호
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    • pp.337-343
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    • 2015
  • Previous studies have shown that the drying shrinkage of recycled aggregate concrete (RAC) is greater than that of natural aggregate concrete (NAC). Drying shrinkage is the fundamental reason for the cracking of concrete, and tensile creep caused by the restraint of drying shrinkage plays a significant role in the cracking because it can relieve the tensile stress and results in the delay of cracking occurrence. However, up till now, all research has been focusing on the compressive creep of RAC. Therefore, in this study, a uniaxial restrained shrinkage cracking test was executed to investigate the tensile creep properties caused by the restraint of drying shrinkage of RAC. The mechanical properties, such as compressive strength, tensile splitting strength, and Young's modulus of RAC were also investigated in this study. The results confirmed that the tensile creep of RAC caused by the restraint of shrinkage was about 20-30 % larger than that of NAC.

가열조건에 따른 초고강도 콘크리트의 내부수증기압력 평가 (Evaluation on Vapor Pressure of Ultra-high-strength Concrete by Heating Condition)

  • 황의철;김규용;윤민호;이보경;서원우;백재욱
    • 한국건축시공학회:학술대회논문집
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    • 한국건축시공학회 2017년도 춘계 학술논문 발표대회
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    • pp.224-225
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    • 2017
  • Ultra-high-strength concrete exposed to high temperature is likely to cause spalling. Spalling is caused by the vapor pressure of the concrete, and the vapor pressure may be different depending on the heating conditions of the concrete. Therefore, in this study, a ring-type restrained specimen was fabricated using ultra-high-strength concrete and the vapor pressure generated in the concrete by heating condition(rapid and slow heating) was evaluated.

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가열조건에 따른 링형 구속 콘크리트의 폭렬특성 (Spalling Properties of Ring-Type Restrained Concrete by Heating Conditions)

  • 황의철;김규용;이상규;손민재;백재욱;남정수
    • 한국건축시공학회:학술대회논문집
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    • 한국건축시공학회 2018년도 추계 학술논문 발표대회
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    • pp.155-156
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    • 2018
  • In this study, surface spalling and explosive spalling of ring-type ultra-high strength concrete under rapid heating and slow heating were investigated. In rapid heating, the internal temperature difference of the concrete is large, so that continuous surface spalling occurs. However, in slow heating, the difference in the internal temperature of the concrete is small, resulting in explosive spalling at a time. Since the heating condition has a great influence on the internal temperature of the concrete, it is necessary to consider the spalling of the concrete under various heating conditions.

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고온에 노출된 링형 강관 구속 콘크리트의 폭렬 및 초음파투과시간 (Spalling and Ultrasonic Pulse Transmission Time of Ring-Type Restrained Concrete exposed to High Temperature)

  • 황의철;김규용;이상규;손민재;편수정;남정수
    • 한국건축시공학회:학술대회논문집
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    • 한국건축시공학회 2019년도 춘계 학술논문 발표대회
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    • pp.174-175
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    • 2019
  • In this study, the spalling and ultrasonic pulse transmission time of concrete were investigated according to compressive strength during heating. As a result, the higher the compressive strength of the concrete, the more the explosion occurs, which affects the cross-sectional loss and the spalling fragment size. Also, ultrasonic pulse transmission time was found to be strongly influenced by the section loss of concrete.

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Simplified Algorithm of the Novel Steel-concrete Mixed Structure under Lateral Load

  • Li, Liang;Li, Guo-qiang;Liu, Yu-shu
    • 국제초고층학회논문집
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    • 제1권4호
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    • pp.247-254
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    • 2012
  • In order to improve the seismic behaviors of traditional steel-concrete mixed structure, a novel steel concrete mixed structure consisting of steel frames braced with buckling restrained braces (BRBs) and a concrete tube is proposed. Based on several assumptions, the simplified mechanical model of the novel mixed structure is established, and the shear and bending stiffness formulas of the steel frames, BRBs and concrete tube are respectively introduced. The equilibrium differential equation of the novel mixed structure under horizontal load is developed based on the structural elastic theory. The simplified algorithms to determine the lateral displacement and internal forces of the novel mixed structure under the inverted-triangle distributed load, uniformly load and top-concentrated load are then obtained considering several boundary conditions and compatible deformation conditions. The effectiveness of the simplified algorithms is verified by FEM comparison.

A GMDH-based estimation model for axial load capacity of GFRP-RC circular columns

  • Mohammed Berradia;El Hadj Meziane;Ali Raza;Mohamed Hechmi El Ouni;Faisal Shabbir
    • Steel and Composite Structures
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    • 제49권2호
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    • pp.161-180
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    • 2023
  • In the previous research, the axial compressive capacity models for the glass fiber-reinforced polymer (GFRP)-reinforced circular concrete compression elements restrained with GFRP helix were put forward based on small and noisy datasets by considering a limited number of parameters portraying less accuracy. Consequently, it is important to recommend an accurate model based on a refined and large testing dataset that considers various parameters of such components. The core objective and novelty of the current research is to suggest a deep learning model for the axial compressive capacity of GFRP-reinforced circular concrete columns restrained with a GFRP helix utilizing various parameters of a large experimental dataset to give the maximum precision of the estimates. To achieve this aim, a test dataset of 61 GFRP-reinforced circular concrete columns restrained with a GFRP helix has been created from prior studies. An assessment of 15 diverse theoretical models is carried out utilizing different statistical coefficients over the created dataset. A novel model utilizing the group method of data handling (GMDH) has been put forward. The recommended model depicted good effectiveness over the created dataset by assuming the axial involvement of GFRP main bars and the confining effectiveness of transverse GFRP helix and depicted the maximum precision with MAE = 195.67, RMSE = 255.41, and R2 = 0.94 as associated with the previously recommended equations. The GMDH model also depicted good effectiveness for the normal distribution of estimates with only a 2.5% discrepancy from unity. The recommended model can accurately calculate the axial compressive capacity of FRP-reinforced concrete compression elements that can be considered for further analysis and design of such components in the field of structural engineering.

A numerical analysis on the performance of buckling restrained braces at fire-study of the gap filler effect

  • Talebi, Elnaz;Tahir, Mahmood Md.;Zahmatkesh, Farshad;Kueh, Ahmad B.H.
    • Steel and Composite Structures
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    • 제19권3호
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    • pp.661-678
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    • 2015
  • Buckling Restrained Braces (BRB) have been widely used in the construction industry as they utilize the most desirable properties of both constituent materials, i.e., steel and concrete. They present excellent structural qualities such as high load bearing capacity, ductility, energy-absorption capability and good structural fire behaviour. The effects of size and type of filler material in the existed gap at the steel core-concrete interface as well as the element's cross sectional shape, on BRB's fire resistance capacity was investigated in this paper. A nonlinear sequentially-coupled thermal-stress three-dimensional model was presented and validated by experimental results. Variation of the samples was described by three groups containing, the steel cores with the same cross section areas and equal yield strength but different materials (metal and concrete) and sizes for the gap. Responses in terms of temperature distribution, critical temperature, heating elapsed time and contraction level of BRB element were examined. The study showed that the superior fire performance of BRB was obtained by altering the filler material in the gap from metal to concrete as well as by increasing the size of the gap. Also, cylindrical BRB performed better under fire conditions compared to the rectangular cross section.

합성반강접 CFT기둥-보 접합부 구조의 경제성 평가 (The Structural Economical Efficiency Evaluation of Partially Restrained Composite CFT Column-to-Beam Connection)

  • 김선희;방중석;박영욱;최성모
    • 한국강구조학회 논문집
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    • 제24권1호
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    • pp.109-117
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    • 2012
  • 연구대상은 콘크리트 충전강관 (Concrete Filled steel tube)기둥과 보의 접합부를 합성반강접으로 적용한 구조물의 설계 적용에 관한 것이다. 합성반강접으로 기둥접합부의 강성을 조절함으로서 구조적 안전성을 확보하고 경제적인 부재를 적용하고자 하였다. 저층건물을 모멘트골조로 구조물의 안정성을 검토한 결과 합성작용으로 인하여 합성반강접을 이용하면 횡강성이 증대하여 저층건물의 경우 특별한 횡 보강재 없이 저항할 수 있음을 확인 하였다. 고층건물의 경우 모멘트골조가 횡저항 분담이 10%정도 되었으며 반강접 비율은 60%정도가 적절하였다. 경제적인 면에서 보 부재는 등분포하중이 작용하는 경우는 반강접 효과가 크나 집중하중이 작용하는 보는 반강접 효과가 크지 않았으며 등분포의 경우 60% 반강접이 단부 모멘트 저감에 따른 경제성이 가장 좋은 것으로 분석되었다. 단부 모멘트는 약 25% 감소되는 것을 확인 할 수 있었다.