• Title/Summary/Keyword: strength

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The Relevant Variables of Parent-Leadership that Influence Family Strength (가족건강성에 영향을 미치는 부모 리더십에 대한 연구)

  • Chae, Kyoung-Sun
    • Journal of the Korean Home Economics Association
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    • v.44 no.3 s.217
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    • pp.51-59
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    • 2006
  • The purpose of this study is to determine the relevant variables of parent-leadership that influence family strength based on the transformational leadership and transactional leadership proposed by Bernard M. Bass and to investigate the primary impact of leadership on the subordinate's job satisfaction and job involvement to his/her supervisor. Therefore, this study will provide implications for the family through a diagnosis of the effect by leadership. The results of this research are as follows : 1) How is the relationship of parent-leadership and family strength? A positive correlation was found between transformational leadership scores and family strength. A negative correlation was found between nontransactional leadership scores and family strength. 2) How had transformational leadership and transactional leadership affected on the family strength? Transformational leadership had the strongest effect on family strength. How had the 7 sub- factors of transformational/transactional leadership affected family strength? Idealized influence and contingent reward had strong effect on family strength but management by except had a negative effect on family strength.

Bond Strength of Reinforcing Steel to High Strength, High Flow Belite Concrete (고강도, 고유동 Belite 콘크리트의 부착성능)

  • 김상준;조필규;이세웅;최완철
    • Proceedings of the Korea Concrete Institute Conference
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    • 1998.04b
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    • pp.653-660
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    • 1998
  • Bond strength of reinforcing bar to high-performance concrete using belite cement is explored using beam end test specimen. The key parameters for the bond test are slump of concrete, top bar effect, and strength of concrete in addition to concrete covers. Specimen failed in the typical brittle bond failure splitting the concrete cover as the wedging action. The test results show that the specimens with belire cement concrete show higher bond strength than those with portland cement concrete. Bond strength of the top bar is less than bond strength of bottom bar, but the top bar factor satisfies the modification factor for top reinforcement. The results also show that the bond strength is function of the square root of concrete compressive strength and cover thickness. The recently developed high-strength and high-slump concrete with belite cement performs well in terms of bond strength to reinforcing steel.

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The Mechanical Properties of High Strength Concrete in Massive Structures

  • Park, Ki-Bong
    • Architectural research
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    • v.15 no.1
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    • pp.53-58
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    • 2013
  • High strength concrete is being used increasingly in mass structure projects. The purpose of this study is to investigate the influence of temperature during mixing, placing and curing on the strength development, hydration products and pore structures of high strength concrete in mass structures. The experiments were conducted with two different model walls, viz.: 1.5 m and 0.3 m under typical summer and winter weather conditions. The final part of this study deal with the clarification of the relationship between the long-term strength loss and the microstructure of the high strength concrete at high temperatures. Test results indicated that high elevated temperatures in mass concrete structures significantly accelerate the strength development of concrete at the early ages, while the long-term strength development is decreased. The long-term strength loss is caused by the decomposition of ettringite and increased the total porosity and amount of small pores.

Analysis Strength Improvement on 50 to 80 MPa Level High Performance Concrete (50~80 MPa급 고성능 콘크리트의 강도증진해석)

  • Park, Byung-Kwan;Lee, Ju-Sun;Jang, Ki-Hyun;Choi, Young-Wha;Han, Min-Cheol;Han, Cheon-Goo
    • Proceedings of the Korean Institute of Building Construction Conference
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    • 2008.11a
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    • pp.93-96
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    • 2008
  • This research performed strength improvement analysis after evaluating strength characteristics by estimated temperatures to evaluate the real time strength performance of 50 to 80 MPa high performance concrete equipped with heat resistance, and the results are as follows. The lesser W/B and the lesser target slump flow value difference, compression strength was shown to increase, and the more curing temperature becomes, the strength increased accordingly. According to the correlation review result of strength improvement analysis by estimated temperature change performed using logistic analysis model, the compression strength value predicted with logistic curve expression and the compression strength value measured in experiment were shown to have similar correlation, and the strength improvement analysis value by logistic model was shown to be estimated good when W/B is high.

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Prediction of compressive strength of concrete based on accelerated strength

  • Shelke, N.L.;Gadve, Sangeeta
    • Structural Engineering and Mechanics
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    • v.58 no.6
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    • pp.989-999
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    • 2016
  • Moist curing of concrete is a time consuming procedure. It takes minimum 28 days of curing to obtain the characteristic strength of concrete. However, under certain situations such as shortage of time, weather conditions, on the spot changes in project and speedy construction, waiting for entire curing period becomes unaffordable. This situation demands early strength of concrete which can be met using accelerated curing methods. It becomes necessary to obtain early strength of concrete rather than waiting for entire period of curing which proves to be uneconomical. In India, accelerated curing methods are used to arrive upon the actual strength by resorting to the equations suggested by Bureau of Indian Standards' (BIS). However, it has been observed that the results obtained using above equations are exaggerated. In the present experimental investigations, the results of the accelerated compressive strength of the concrete are used to develop the regression models for predicting the short term and long term compressive strength of concrete. The proposed regression models show better agreement with the actual compressive strength than the existing model suggested by BIS specification.

Shear Strength of High Strength Concrete Beams with Steel Fibrous (강섬유를 혼입한 고강도 콘크리트 보의 전단강도)

  • 곽계환;박종건;정태영
    • Journal of the Korea Concrete Institute
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    • v.12 no.4
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    • pp.23-30
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    • 2000
  • The purpose of this paper is to study on the shear strength of high strength concrete beams with steel fibrous. In general, the shear strength of reinforced concrete beams is affected by the compressive strengths of concrete( c), the shear span-depth ratio(a/d), the longitudinal steel ratio($\rho$ $\omega$), and shear reinforcement. An experimental investigation of the shear strength of high strength concrete beams with steel fibrous was conducted. In each series the shear span-depth ratio(a/d) was held constant at 1.5, 2.8, or 3.6, while concrete strengths were varied from 320 to 520, to 800kgf/$\textrm{cm}^2$. To verify the proposed equations the experimental results were compared with those from other researches such as equation of ACI code 318-95 or equation of Zsutty. To deduce equation for shear strength from experimental data carried out MINITAP program. According to the experimental results, the addition of steel fibrous has increased the deflection and strain at failure load, improving the brittleness of the high strength concrete.

Structural Safety Evaluation for Static Strength of Thin Plate RC Member with High Strength Concrete (고강도 콘크리트를 적용한 얇은 RC 판부재의 정적 강도 안전성 평가)

  • Hwang, Hoon-Hee;Park, Sung-Yong
    • Journal of the Korean Society of Safety
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    • v.32 no.5
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    • pp.69-75
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    • 2017
  • Structural safety evaluation for static strength of thin plate RC member with high strength concrete is conducted in this study. Static strengths were predicted and compared with the experimental values. Predicted values were calculated by the evaluation formula based on the punching shear behavior and the yield line theory which can appear in the plate members. Static load tests were carried out for the specimens with high strength concrete and the test results were compared with the required performance in design. The comparison results show that the specimens with high strength concrete have sufficient structural safety for flexural and punching shear performance required in design. High strength concrete specimens exhibited excellent strength despite their small thickness. The range of concrete strengths applied in this study was about 60 MPa to 100 MPa.

Long-term development of compressive strength and elastic modulus of concrete

  • Yang, Shuzhen;Liu, Baodong;Yang, Mingzhe;Li, Yuzhong
    • Structural Engineering and Mechanics
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    • v.66 no.2
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    • pp.263-271
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    • 2018
  • Compressive strength and elastic modulus of concrete are constantly changing with age. In order to determine long-term development of compressive strength and elastic modulus of concrete, an investigation of C30 concrete cured in air conditions was carried out. Changes of compressive strength and elastic modulus up to 975 days were given. The results indicated that compressive strength and elastic modulus of concrete rapidly increased with age during the initial 150 days and then increased slowly. The gain in elastic modulus was slower than that of compressive strength. Then relationships of time-compressive strength, time-elastic modulus and compressive strength-elastic modulus were proposed by regression analysis and compared with other investigations. The trends of time-compressive strength and time-elastic modulus with age agreed best with ACI 209R-92. Finally, factors contributed to long-term development of compressive strength and elastic modulus of concrete were proposed and briefly analyzed.

An Experimental Study on manufacturing Ultra-High Strength Concrete of 3116kgf/$\textrm{cm}^2$ Compressive Strength (압축강도 3116kgf/$\textrm{cm}^2$ 초강도콘크리트의 개발에 관한 실험적 연구)

  • 최세진;강석표;최희용;김규용;김진만;김무한
    • Proceedings of the Korea Concrete Institute Conference
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    • 1997.04a
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    • pp.323-328
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    • 1997
  • The strength of concrete depends on factors of materials, composition and manufacturing method. Among these factors, preparatory experiments are to consider and analyze the factors on compressive strength of ultra-high strength concrete according to types of aggregate, binder content, water-binder ratio, and curing methods. And the final experiment to develop the ultra-high strength over 3,000kgf/$\textrm{cm}^2$ is based on these preparatory experiments. As the result of this final expriment. We could manufacture the ultra-high strength concrete with a marvelous compressive strength concrete with a marvelous compressive strength of 3,116kgf/$\textrm{cm}^2$. This study is to compare and analyze the manufacturing system of ultra-high strength concrete of 3,116kgf/$\textrm{cm}^2$ compressive strength in the side of material development of construction industry.

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A Study on the Effects of Curing Temperature for Compressive Strength of High Performance Concrete (양생온도 변화가 고성능 콘크리트의 압축강도에 미치는 영향에 관한 연구)

  • Ro, In-Cheul
    • Journal of the Korea Institute of Building Construction
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    • v.2 no.4
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    • pp.163-168
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    • 2002
  • The object of this study is to define the characteristics of high performance concrete with varing compressive strength of concrete and curing temperature. The major test variables are 1) high strength concrete(500kg/$cm^2$) and ordinary strength concrete(240kg/$cm^2$) compressive strength, 2) curing temperature and condition, 3) concrete curing age, 4) three types of cement. From the test results were shown that curing temperature and curing conditions were also very effective for high strength concrete and ordinary strength concrete, and concrete were largely effected by cement type and temperature during the hydration reaction process. This paper describes the effect of curing temperature for strength and characteristics of high performance concrete.