• Title/Summary/Keyword: compressive strength equation

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Compressive Strength Development Model for Concrete Cured by Microwave Heating Form (마이크로웨이브 발열거푸집으로 양생된 콘크리트의 압축강도발현 모델)

  • Koh, Tae-Hoon;Moon, Do-Young;Bae, Jung-Myung;Yoo, Jung-Hoon
    • Journal of the Korea Concrete Institute
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    • v.27 no.6
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    • pp.669-676
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    • 2015
  • Time dependent model for prediction of compressive strength development of concrete cured by microwave heating form was presented in this study. The presented model is similar to the equation which is given in ACI 209R-92 but the constants which is dependent on cement type and curing method in the presented model are modified by the regression analysis of the experimental data. Laboratory scale concrete specimens were cast and cured by the microwave heating form and drilled cores extracted from the specimens were fractured in compression. The measured core strengths are converted to standard core and in-situ strengths. These in-situ strengths are used for the regression.

Compressive Behavior of Concrete with Loading and Heating (가열 및 재하에 의한 콘크리트의 압축거동)

  • Kim, Gyu-Yong;Jung, Sang-Hwa;Lee, Tae-Gyu;Kim, Young-Sun;Nam, Jeong-Soo
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.14 no.4
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    • pp.119-125
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    • 2010
  • The performance deformation of concrete can be caused by many factors such as load, thermal strain and creep at high temperature. Japan, Europe and America have been doing various experimental studies to solve these problems about thermal properties of concrete at high temperature, each study has generated different results due to a heating methods, heating hours, size of specimens and performance of a the loading, heating method, size of specimen and heating machine. There has been no unified experimental method so far. Therefore, this study reviewed experimental studies on the strength performance of concrete subject to heating and loading method. As a result, compressive strength of specimen prestressed increase in the temperature range of between $100^{\circ}C$ and about $400^{\circ}C$. Also, results can be analyzed as compare equation of compressive strength at elevated temperature with CEN and CEB code.

The Fundamental Study on Quality Properties of Binary Blended Concrete according to Water Reducing Performance of Chemical Admixture and Estimation Equation of Compressive Strength (화학 혼화제의 감수 성능에 따른 2성분계 콘크리트의 품질특성 및 압축강도 추정식에 관한 기초적 연구)

  • Kim, Kyung-Hwan;Oh, Sung-Rok;Choi, Byung-Keol;Choi, Yun-Wang
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.20 no.1
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    • pp.9-17
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    • 2016
  • In this study, binary blended concrete mix with fly ash and ground granulated blast furnace slag was prepared according to 3 level of water reduction performance of chemical admixture (0%, 8% and 16%) and 3 level of water-cement ratio (40%, 45% and 50%) for evaluation of quality properties of binary blended concrete according to performance of chemical admixture. concrete mix was carried out repetition test of three times in order to secure the reliability. As a result, compressive strength according to performance of chemical admixture was found that difference of strength was about 20% occurred, chemical admixture was showed that a great influence on qualities of concrete. In addition, reflected the effect of performance of chemiacal admixture, prediction model equations for concrete compressive strength was proposed, it was found that more than 85% of the high correlation.

Shear Strength and Failure Mode of Architectural Masonry Walls (내진보강된 치장조적벽의 파괴특성과 전단강도)

  • Jin, Hee-Yong;Han, Sang-Whan;Park, Young-Mi
    • Proceedings of the Korea Concrete Institute Conference
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    • 2008.04a
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    • pp.89-92
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    • 2008
  • This study investigates the shear behavior of architectural masonry veneer wall reinforced with specific reinforcement details proposed by this study. For this purpose, experimental tests were conducted using one un-reinforced masonry(URM) wall specimen and three reinforced masonry(RM) wall specimens under quasi static cyclic loads. Un-reinforced(plain) masonry wall is expressed that behavior and failure mode are different for aspect ratio(L/H) and axial compressive force. The test variables are wall aspect ratio and presence of reinforcement. These specimens are masonry structure for architectural clading that is not to exist the axial compressive force. thus the axial compressive force is excepted from test variable. Test result, Behavior of specimens are dominated over rocking mode, but final failure modes are combined with different behaviors. And FEMA273 has proposed the equation of shear strength of masonry pier subjected to in-plane loading. Shear strength equations are classified four types of failure mode that is Rocking, and Toe-Crushing, Bed-Joint-Sliding and Diagonal-Tension. FEMA273 equations predict the behavior modes well, but shear strength is shown in different result.

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Fatigue Strength Analysis of Complex Planetary Gear Train of the Pitch Drive System for Wind Turbines (풍력발전용 피치 드라이브 시스템의 복합 유성기어류에 대한 피로 강도해석)

  • Kim, KwangMin;Bae, MyungHo;Cho, YonSang
    • Tribology and Lubricants
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    • v.37 no.2
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    • pp.48-53
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    • 2021
  • Wind energy is considered as the most competitive energy source in terms of power generation cost and efficiency. The power train of the pitch drive for a wind turbine uses a 3-stage complex planetary gear system in being developed locally. A gear train of the pitch drive consists of an electric or hydraulic motor and a planetary decelerator, which optimizes the pitch angle of the blade for wind generators in response to the change in wind speed. However, it is prone to many problems, such as excessive repair costs in case of failure. Complex planetary gears are very important parts of a pitch drive system because of strength problem. When gears are designed for the power train of a pitch drive, it is necessary to analyze the fatigue strength of gears. While calculating the specifications of the complex planetary gears along with the bending and compressive stresses of the gears, it is necessary to analyze the fatigue strength of gears to obtain an optimal design of the complex planetary gears in terms of cost and reliability. In this study, the specifications of planetary gears are calculated using a self-developed gear design program. The actual gear bending and compressive stresses of the planetary gear system were analyzed using the Lewes and Hertz equation. Additionally, the calculated specifications of the complex planetary gears were verified by evaluating the results from the Stress - No. of cycles curves of gears.

Creep behaviour of mudstone in the tertiary Duho Formation at Pohang basin (포항분지 제3기 두호층 이암의 크리프 거동)

  • 김광식;김교원
    • The Journal of Engineering Geology
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    • v.13 no.2
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    • pp.227-238
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    • 2003
  • Understanding of a creep behavior in rocks under a constant load, due to visco-elastic properties of rock, is an essential element to predict a long term ground deformation. In order to clarify the creep characteristics of the mudstone in Duho formation at Pohang basin, deposited during Tertiary, a series of laboratory tests including physical properties, unconfined compressive strength and uniaxial creep tests, was performed. The mudstone showed a higher creep potential due to 26% of clay minerals such as illite and chlorite. The unconfined compressive strength of the rock was $462{\;}kg/\textrm{cm}^2$ in average, and four creep tests were performed under constant stress of 40 to 70 % of the strength. The creep constants in the empirical and theoretical equations were deduced from the time-strain curves obtained from the tests. Among the several equations, the empirical equation proposed by Griggs and theoretical equation of Burger’s model are appreciated as the best one to express the creep behavior of the mudstone. Instantaneous elastic strain was linearly increased with stress level but strain velocity during the first creep is decreased with a similar pattern by time lapse regardless the stress level.

An Experimental Study on the Flexural Stiffness and Plastic Hinge Ratation Capacity of Reinforced High Performance Concrete Beams (고성능 철근콘크리트 보의 휨강성 및 소성힌지의 회전능력에 관한 실험적 연구)

  • 고만영;김상우;김용부
    • Magazine of the Korea Concrete Institute
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    • v.10 no.4
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    • pp.93-100
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    • 1998
  • This paper presents a study on the flexural stiffness, plastic hinge length and plastic hinge rotation capacity of reinforced high performance concrete beams. 15 beams with different strength of concrete, reinforcement ratio and the pattern of loadings were tested. From the test results of reinforced normal strength concrete beams and reinforced high performance concrete beams with the concrete which has cylinder compressive strength of 700kg/${cm}^2$, slump value of 20~25cm and slump-flow value of 60~70cm. It is found that an extreme fiber concrete compressive strain of ${\varepsilon}_{cu}=0.0047$ may be used in ultimate curvature computations of reinforced high performance concrete beams. An empirical equation is proposed to estimate the effective moment of inertia. length and rotation capacity of plastic hinge of simply supported reinforced high performance concrete beams. The estimated deflections using this equation agree well with the experimental values.

Strength Prediction Equations for High Strength Concrete by Schmidt Hammer Test (슈미트 해머 시험에 의한 고강도 콘크리트의 강도 추정식)

  • Kwon, Young-Wung;Park, Song-Chul;Kim, Min-Su
    • Journal of the Korea Concrete Institute
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    • v.18 no.3 s.93
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    • pp.389-395
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    • 2006
  • For the assessment of exsiting concrete structures, it is important to get the real strength of concrete. The load test or core test has many problems due to cost time, easiness, structural damage, and reliability and so on. Thus, various non-destructive test and statistical analysis techniques for strength assessment have been developed. As a result the real strength of concrete can be obtained by both direct and indirect test. In this study, a series of experimental tests of core strength and Schmidt hammer tests on 3, 7, 14, 28, 90, 180, 365, and 730 days' were done for predicting the compressive strength of high strength concrete with 65.0MPa of 28-days' strength. Each experimental results was analyzed by simple regression analysis. Then, reliability level and error rate between the proposed equations and the existing ones was examined. However, the application of the exsisting equations was inadequate to high strength concrete, because they were conducted under normal strength concrete. Therefore, the following compressive strength equations were proposed for predicting the compressive strength of high strength concrete by Schmidt hammer test. The proposed equations by Schmidt hammer test are as follows.

Push-out tests and bond strength of rectangular CFST columns

  • Qu, Xiushu;Chen, Zhihua;Nethercot, David A.;Gardner, Leroy;Theofanous, Marios
    • Steel and Composite Structures
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    • v.19 no.1
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    • pp.21-41
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    • 2015
  • Push-out tests have been conducted on 18 rectangular concrete-filled steel tubular (CFST) columns with the aim of studying the bond behaviour between the steel tube and the concrete infill. The obtained load-slip response and the distribution of the interface bond stress along the member length and around the cross-section for various load levels, as derived from measured axial strain gradients in the steel tube, are reported. Concrete compressive strength, interface length, cross-sectional dimensions and different interface conditions were varied to assess their effect on the ultimate bond stress. The test results indicate that lubricating the steel-concrete interface always had a significant adverse effect on the interface bond strength. Among the other variables considered, concrete compressive strength and cross-section size were found to have a pronounced effect on the bond strength of non-lubricated specimens for the range of cross-section geometries considered, which is not reflected in the European structural design code for composite structures, EN 1994-1-1 (2004). Finally, based on nonlinear regression of the test data generated in the present study, supplemented by additional data obtained from the literature, an empirical equation has been proposed for predicting the average ultimate bond strength for SHS and RHS filled with normal strength concrete.

The Strength Characteristics of Solidified Sandy Soils with Mixing Conditions (배합조건에 따른 고결사질토의 강도특성)

  • Yu, Chan;Chang, Pyung-Wuck;Lee, Chang-No;Roh, Gwang-Ha
    • Proceedings of the Korean Geotechical Society Conference
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    • 1999.02a
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    • pp.84-95
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    • 1999
  • Laboratory experiments were performed to evaluate the strength characteristics of solidified sandy soils by portland cement with mixing conditions. Factors considered in the experiments were the fine content(<#200, %), cement content(%) and water-cement ratio and unconfined compressive strength tests were performed on samples at 7 and 28 cured day. Results of tests showed that for a low cement content(7%∼10%) the fine content was very important while for a high cement content the water-cement ratio was very important. For 7%∼10% cement content, the optimum fine content which gained maximum strength was about 30%. But for 13% cement content, low fine content and water-cement ratio were more useful than others. In the multi regression analysis, significant equation was gained.

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