• Title/Summary/Keyword: placing height

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Experiments on Mechanical Characteristics of Anti-Washout Concrete with Mixing and Placing Condition (배합 및 타설조건에 따른 수중불분리성 콘크리트의 역학적특성 변화에 관한 실험)

  • Yang, Eun-Ik;Choi, Hong-Shik;Heo, Gweon;Lee, Si-Woo
    • Proceedings of the Korea Concrete Institute Conference
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    • 1999.04a
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    • pp.141-146
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    • 1999
  • An experimental study is carried out to estimate the effects of mixing and placing condition on the mechanical properties of anti-washout concrete. According to the test results, mixing method and placing temperature do affect the characteristics of rrsh concrete, while they do not affect the strength development of anti-washout concrete. But, concrete strength was greatly affected by the placing condition and placing height. Concrete strength decreases linearly as the placing height increased. Compared to the normal concrete, the increase in strength is not associated much with an increase in the elastic modulus of anti-washout concrete.

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Influence of Mixing and Construction Factor on the Bleeding of Concrete (콘크리트의 블리딩에 미치는 배합 및 시공요인의 영향)

  • 황인성;김경민;전충근;신병철;한천구
    • Proceedings of the Korea Concrete Institute Conference
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    • 2002.10a
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    • pp.265-268
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    • 2002
  • This study is focused on the influence of mixture and construction factor on bleeding amount of concrete According to the results, Amount of bleeding with mixture factor increases with increase of water contents and W/C. Amount of bleeding with construction factors is larger in the case of placing height of 1m than in the case of placing height of 0 and 0.5m. Amount of bleeding is larger at the temperature of 20℃ than at the temperature of 35℃ and 5℃, and increases in order of vibration compacting, standard lamping and non tamping. Therefore, to reduce bleeding, it is thought that it is profitable to reduce water content within the range that fluidity and workability don't go bad, to lower the placing height and not to do compacting too much.

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A Study of the Thermal Analysis for the Crack Control of Underground Pier Footing (지하 교각 기초의 온도균열 제어를 위한 수화열 해석 연구)

  • Park, Weon-Tae
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.10 no.2
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    • pp.91-101
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    • 2006
  • Lately, massive concrete structures are increasingly built. In such massive structures, the heat of hydration of mass concrete causes thermal cracks. To avoid thermal crack, methods widely acceptable for practical use are pre-cooling, pipe cooling and control of placing height. Thermal stress analysis is performed to find the way of controlling the thermal crack of pier footing mat in this paper. The footing mat model for the analysis is $12m{\times}14m$area and 3m height. The analysis results are compared with method of control of lift height and method of pipe cooling. The analysis results show that thermal crack can be removed by method of placing control and pipe cooling at footing mat placed on the ground.

Full Scale Tests of Concrete Filled Steel Tube Column using High Fluidity Concrete (고유동 콘크리트를 이용한 콘크리트 충전강관 기둥의 실물대 시공실험)

  • Kim Ook-Jong;Lee Do-Bum
    • Proceedings of the Korean Institute Of Construction Engineering and Management
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    • autumn
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    • pp.222-227
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    • 2001
  • Full scale construction tests of CFT(concrete filled steel tube) column to solve construction problem and to confirm quality were performed in apartment site. To improve construction efficiency, the tests has been accomplished two stages after the tests for material mixing design had been completed. In the first stage, the experimental variables were the placing methods, existence of guiding pipe, placing velocity and drop height and the height of specimen were $3.6{\cal}m$. In the second stage, Filling steel tube of 9.6m height with concrete was performed by two ways, that is, the pump-up method and the dropping method. The filled condition of the concrete and concrete strength distribution according to the column height were checked and the quality of the CFT column was confirmed.

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A Study on the Influencing Factors on the Estimation of Compressive Strength by Small Size Core (소구경 코어에 의한 콘크리트 압축강도 추정에 미치는 실험인자의 영향에 관한 연구)

  • 한민철;김기정;백병훈;한천구;송성진
    • Proceedings of the Korea Concrete Institute Conference
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    • 2002.10a
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    • pp.361-364
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    • 2002
  • This paper discusses the influencing factors such as coring position, height to diameter ratio of core specimen(h/d) and coring torque on the strength estimation of concrete by small site coring method in order to verify the validities of small size core method. According to results, as for the influence of drilling position, when core specimens are obtained from the place parallel to placing direction, compressive strength of core specimens are higher than those perpendicular to placing direction. This is due to the loss of the area of core specimen perpendicular to plating direction by bleeding. And in case of $\phi$ 24mm core specimen, when vertical drilling against placing direction is taken. compressive strength of core specimen obtained at the bottom of the structure is higher than that at the top of the structure. As for the influence of height to depth ratio, as h/d ratio increases compressive strength shows to be decreased. As for the influences of rotation speed of drilling machine, as its speed goes up, compressive strength decreases, regardless of core diameter.

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The Safety Assessment to Breakwater Systems by Placing Submarine Rectangular Trench (해저 Trench 설치에 의한 방파제 시스템의 안전성 평가)

  • Kim, Sung-Duk
    • Journal of the Korean Society of Safety
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    • v.24 no.1
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    • pp.37-42
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    • 2009
  • The present study is to estimate the effect of wave height affecting at the front face of breakwater systems, when a submarine trench is dredged in the distant offshore from outer breakwater. The wave diffraction field, which is important hydraulic factor in the ocean, is considered to be two dimensional(2D) plane and the configuration of the submarine trench on the sea bed designated by single horizontal long-rectangular system. The numerical simulation is performed by using Green function based on the boundary integral equation and meshed at moving boundary conditions. The results of present numerical simulations are illustrated by applying the normal incidence. It is shown that the ratios of wave height reduction at the front face of breakwater systems are approximately 20% by the effect of placing long trench on the sea bed. This study can effectively be utilized for safety assessment to various breakwater systems in the ocean field.

Thermal Crack Control of Mass Concrete by Concrete Placing Height and Curing Method (매스콘크리트의 타설높이 및 양생조건에 따른 온도균열 저감 방안에 관한 연구)

  • 민병소;신길수;김대권;이현희;신성우;이광수
    • Proceedings of the Korea Concrete Institute Conference
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    • 2001.11a
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    • pp.369-376
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    • 2001
  • As many studies have performed to reduce thermal cracking in mass concrete, it is already prepared against thermal cracking, we can find many plans against thermal cracking in several reference book. But it needs practical guidelines to be available in construction site. In this study to establish control method of thermal cracking in mass concrete, tests which have factors of placing thickness and curing method of concrete are performed.

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Simple Method of Evaluating the Range of Shoulder Motion Using Body Parts

  • Yun, Yeo-Hon;Jeong, Byeong-Jin;Seo, Myeong-Jae;Shin, Sang-Jin
    • Clinics in Shoulder and Elbow
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    • v.18 no.1
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    • pp.13-20
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    • 2015
  • Background: The purpose of this study is to assess the range of shoulder motion using an indirect evaluation method without physical examinations of patients based on questionnaires regarding several specific arm postures referenced by patient's own body parts. Methods: Nine criteria of specific shoulder motion including 4 forward flexion, 2 external rotation, and 3 internal rotation were decided as reference position which can represent a certain shoulder motion. Flexion contains postures such as lifting arm to waist-height, shoulder-height, eye-height, and raising arm above head with arm touching ears. External rotation comprises grasping ears and placing hands on back of the head. Vertebral height in internal rotation is determined by calculating the samples' motions, which are holding on to trouser belts, opposite-elbow, and scapula. These postures are included in questionnaires for patients to evaluate the validity and effectiveness of this indirect method. Results: The range of flexion was $77^{\circ}$ ($60^{\circ}$ to $100^{\circ}$), $96^{\circ}$ ($87^{\circ}$ to $115^{\circ}$), $135^{\circ}$ ($115^{\circ}$ to $150^{\circ}$), and $167^{\circ}$ ($150^{\circ}$ to $175^{\circ}$) when arms go up to waist, shoulder, eye, and high vertically. Range of external rotation was $39.6^{\circ}$ ($30^{\circ}$ to $50^{\circ}$) when grasping ears and $69.2^{\circ}$ ($60^{\circ}$ to $80^{\circ}$) with the hands on the back of the head. Range of internal rotation was L4 when placing trouser belts, T12 for holding opposite elbow, and T9 for reaching scapula. The mismatch rates of flexion, external rotation, and internal rotation were 11.6%, 9.6%, and 7.8%. Conclusions: The range of shoulder motion using this method is expected to be applied to an established shoulder scoring system which included shoulder motion evaluation item.

ALC(Autoclaved Lightweight Concrete) Hardness Prediction Research By Multiple Regression Analysis (다중회귀분석을 이용한 ALC 경도예측에 관한 연구)

  • Kim, Gwang-Su;Baek, Seung-Hun
    • Proceedings of the Safety Management and Science Conference
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    • 2012.04a
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    • pp.117-137
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    • 2012
  • In the ALC(Autoclaved lightweight concrete) manufacturing process, if the pre-cured semi-cake is removed after proper time is passed, it will be hard to retain the moisture and be easily cracked. Therefore, in this research, we took the research by multiple regression analysis to find relationship between variables for the prediction the hardness that is the control standard of the removal time. We study the relationship between Independent variables such as the V/T(Vibration Time), V/T movement, expansion height, curing time, placing temperature, Rising and C/S ratio and the Dependent variables, the hardness by multiple regression analysis. In this study, first, we calculated regression equation by the regression analysis, then we tried phased regression analysis, best subset regression analysis and residual analysis. At last, we could verify curing time, placing temperature, Rising and C/S ratio influence to the hardness by the estimated regression equation.

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Evaluation of Construction RCB Exterior Wall Formwork according to Placing Height on Nuclear Power Plant

  • Song, Hyo-Min;Sohn, Young-Jin;Shin, Yoonseok
    • Journal of the Korea Institute of Building Construction
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    • v.15 no.6
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    • pp.653-660
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    • 2015
  • Technologies for reducing construction duration are key factors in nuclear power plant construction projects, as a reduction in construction duration at the construction phase leads to a reduction in construction cost and an increase in profits through the early operation of the nuclear power plant. To analyze the constructability of the height of single-layer placement of formwork for the Reactor Containment Building (RCB) exterior wall through lateral pressure according to the height of concrete placement, the deformation criteria for formwork, and a new form design, 'MIDAS GEN (hereinafter referred to as MIDAS)' is used in this study. The cost and workload of formwork are derived according to the unit of height of the RCB exterior wall. Based on the result, it was found that the higher the RCB exterior wall, the higher the material cost, and the less the construction duration and the less the total number of formwork layers. Based on this result, it is believed that the material cost and the construction duration can be appropriately determined according to the formwork height.