• Title, Summary, Keyword: Elastic Modulus

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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.

Effect of Temperature and Aging on the Relationship between Dynamic and Static Elastic Modulus of Concrete (온도와 재령이 콘크리트의 동탄성계수와 정탄성계수의 상관관계에 미치는 영향)

  • 한상훈;김진근
    • Proceedings of the Korea Concrete Institute Conference
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    • pp.445-450
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    • 2001
  • The paper investigates the relationships between dynamic elastic modulus and static elastic modulus or compressive strength according to curing temperature, aging, and cement type. Based on this investigation, the new model equations are proposed. Impact echo method estimates the resonant frequency of specimens and uniaxial compression test measures the static elastic modulus and compressive strength. Type I and V cement concretes, which have the water-cement ratios of 0.40 and 0.50, are cured under the isothermal curing temperature of 10, 23, and 50 $^{\circ}C$. Cement type and aging have no large influence on the relationship between dynamic and static elastic modulus, but the ratio of dynamic and static elastic modulus comes close to 1 as temperature increases. Initial chord elastic modulus, which is calculated at lower strain level of stress-strain curve, has the similar value to dynamic elastic modulus. The relationship between dynamic elastic modulus and compressive strength has the same tendency as the relationship between dynamic and static elastic modulus. The proposed relationship equations between dynamic elastic modulus and static elastic modulus or compressive strength properly estimates the variation of relationships according to cement type, temperature, and aging.

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Determining Shear Modulus of 3-ply Laminated Veneer Lumber by Uniaxial Tension Test

  • Oh, Sei-Chang
    • Journal of the Korean Wood Science and Technology
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    • v.41 no.5
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    • pp.425-431
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    • 2013
  • Estimation equations of shear modulus in the plane of laminated veneer lumber (LVL) were compared each other through uniaxial tension test results. The equations - basic elastic equation in the dimensional orthotropic case, Hankinson's formula and empirical equation proposed by Salikis and Falk, were applied to determine the elastic constants at various angles to the grain, which were needed for determination of shear modulus. Tensile elastic modulus of LVL predicted from these equations were compared with test data to evaluate the accuracy of the equation. Tensile elastic modulus rapidly decreased at orientations between 0 and 15 degrees and elastic modulus at grain angles of 15, 30, and 45 degrees overestimated in the presented equations. But the proposed equation by Salikis and Falk showed better prediction, especially at 30, and 45 degrees. This proposed formula would be more useful and practical for estimating of shear modulus of wood composites like LVL to minimize the effect of Poisson's ratio term.

Estimation of Pile Shaft Resistances with Elastic Modulus Depending on Strain (변형률에 따른 탄성계수 변화를 고려한 말뚝의 주면지지력 산정)

  • Kim, Seok-Jung;Kim, Sung-Heon;Jung, Sung-Jun;Kwon, Oh-Sung;Kim, Myoung-Mo
    • Proceedings of the Korean Geotechical Society Conference
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    • pp.933-943
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    • 2009
  • Axial loads and shaft resistances can be calculated by load transfer analysis using strain data with load level. In load transfer analysis, the elastic modulus of concrete is a one of the most important parameters to consider. The elastic modulus, $E_{50}$, suggested by ACI (American Concrete Institute), has been commonly used. However, elastic modulus of concrete shows nonlinear stress-strain characteristic, so nonlinearity should be considered in load transfer analysis. In this paper, a load transfer analysis was performed by using data obtained from bi-directional pile load tests for four cases of drilled shafts. For consideration of nonlinearity, elastic modulus was calculated by both the Fellenius method and the nonlinear method, assuming the stress-strain relation of concrete to be a quadratic function, and then, the calculated elastic modulus was applied to the estimation of shaft resistance. The calculated shaft resistances were compared with the result obtained using the constant elastic modulus of ACI code. It was found that the f-w curves are similar to each method, and elastic modulus and shaft resistances decreased as strain increased. Moreover, shaft resistances estimated from elastic modulus considering nonlinearity were 5~15% different than those obtained using the constant elastic modulus.

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Correlation Analysis between Ultrasonic Parameters and Elastic Modulus of Apple

  • Kim, Ghi-Seok;Kim, Ki-Bok;Park, Jeong-Gil;Lee, Sang-Dae;Jung, Hyun-Mo;Kim, Man-Soo
    • Journal of the Korean Society for Nondestructive Testing
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    • v.28 no.3
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    • pp.279-284
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    • 2008
  • The firmness of fruit is one of the most important quality factors and is highly correlated to the elastic modulus. In this study, the ultrasonic transmission method was applied to evaluate the elastic modulus of the apple. In order to transmit and receive the ultrasonic wave through the whole apple, the ultrasonic measurement setup consisted of ultrasonic pulser, two specially fabricated ultrasonic transducers for fruit and digital storage oscilloscope. Ultrasonic parameters such as ultrasonic wave velocity, apparent attenuation, and peak frequencies were analyzed. The elastic modulus of apple was measured by using compression test apparatus. The correlations between ultrasonic parameters and elastic modulus were analyzed. A multiple linear regression model describing the relationship between elastic modulus and ultrasonic parameters was proposed.

Effects of environmental temperature and age on the elastic modulus of concrete

  • Yang, Shuzhen;Liu, Baodong;Li, Yuzhong;Zhang, Minqiang
    • Structural Engineering and Mechanics
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    • v.72 no.6
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    • pp.737-746
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    • 2019
  • Concrete mechanical properties change constantly with age, temperature, humidity and the other environmental factors. This research studies the effects of temperature and age on the development of concrete elastic modulus by a series of prism specimens. Elastic modulus test was conducted at various temperatures and ages in the laboratory to examine the effects of temperature and age on it. The experimental results reveal that the concrete elastic modulus decreases with the rise of temperature but increases with age. Then, a temperature coefficient K is proposed to describe the effects of temperature and validated by existing studies. Finally, on the basis of K, analytical models are proposed to determine the elastic modulus of concrete at a given temperature and age. The proposed models can offer designers an approach to obtain more accurate properties of concrete structures through the elastic modulus modification based on actual age and temperature, rather than using a value merely based on laboratory testing.

An Experimental Study on the Elastic Modulus of Deep Mixing Ground Specimen (심층혼합 시료의 탄성계수에 관한 실험적 연구)

  • Park, Choon-Sik;Park, Hwan-Ki
    • Journal of the Korean Geotechnical Society
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    • v.34 no.10
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    • pp.39-49
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    • 2018
  • In this study, aimed at determining the elastic modulus of deep mixed samples, 320 test specimens were developed by mixing 8%, 10%, 12%, and 14% of stabilizer mixture in the granular conditions of clay, sand and gravel. Uniaxial compression tests were carried out using these specimens, and the uniaxial compression strength and strain were analyzed to determine the secant elastic modulus and tangent elastic modulus. Laboratory test results showed that the uniaxial compression strength of all deep mixed samples increased with increasing curing time and stabilizer mixing ratio, and that the secant elastic modulus and the tangen elastic modulus also increased. The increase of the elastic modulus according to the curing period turned out greater in the tangent elastic modulus than in the secant elastic modulus. In order to measure elastic modulus with changes in stabilizer mixing ratio, the correlation coefficient between the elastic modulus for stabilizer mixing ratio of 8% and that of 10%, 12% and 14% was calculated respectively by the specimen condition. The elastic modulus tended to increase as the grain size in a deep mixed specimen increased. The distribution of grain size that had the greatest effect appeared when the composition ratio of sand was high. On the other hand, the increase in the elastic modulus was larger in the sand specimens than in the clay and gravel specimens. Based on these results, it is suggested that a pertinent soil parameter of the deep mixed ground in the field may be obtained by the particle size distribution and the mixing ratio of stabilizer of the deep mixed soil.

Effect of Weld Elastic Modulus on Simulation of Stress Concentration and Fatigue Life for Boiler Vessel (ADINA & WINLIFE 활용한 압력용기 용접부 피로파괴 해석)

  • Choe, Byung Hak;Lee, Bum Gyu;Shim, Jong Heon;Park, Chan Sung;Kim, Jin Pyo;Park, Nam Gyu
    • Journal of Welding and Joining
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    • v.34 no.5
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    • pp.47-53
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    • 2016
  • The aim of this study is to consider effect of weld elastic modulus on simulations of stress concentration and fatigue life for pressure vessel. The investigations include analysis with ADINA and WINLIFE softwares for whole body model about using condition of the boiler vessel. Values of weld elastic modulus were divided by 5 steps in butt weld area of the boiler vessel body. The stress concentration of the butt weld more was increased in case of higher elastic modulus of weld area because of higher difference of material properties between matrix and weld. It was concluded that the fatigue lives were decreased along increasing stress concentration due to high elastic modulus of weld. The matrix microstructure was estimated as pearlitic structure of ${\alpha}$ ferrite and pearlite. And the microstructures of welds along 5 steps of elastic modulus were estimated as bainitic fine pearlite and martensite as increasing elastic modulus.

A Proposal of an Elastic Modulus Equation for High-Strength and Ultra High-Strength Concrete

  • Jang, II-Young;Park, Hoon-Kyu;Yoon, Young-Soo
    • International Journal of Concrete Structures and Materials
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    • v.18 no.1E
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    • pp.43-48
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    • 2006
  • This paper presents an elastic modulus equation more appropriate for predicting the elastic modulus of structural materials designed for and made of high- and ultra high-strength concrete under current domestic situation in Korea. In order to validate and assess the proposed elastic modulus equation, more than 400 laboratory test data available in the domestic literature on compressive strength of concrete in the range between 400 to 1,000 $kgf/cm^2$ were used and analyzed statistically. Comparison analyses of the proposed elastic modulus equation with previously suggested equations of ACI363R, CEB-FIP, NS3473 and New-RC are also presented to demonstrate its applicability in domestic practice.

A Study on the Prediction of Elastic Modulus in Short Fiber Composite Materials (단섬유 복합재료의 탄성계수 예측에 관한 연구)

  • Kim Hong Gun
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.29 no.2
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    • pp.318-324
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    • 2005
  • Theoretical efforts are performed to extend the formulation of NSLT(New Shear Lag Theory) for the prediction of the elastic modulus in short fiber composite. The formulation is based on the elastic stress transfer considering the stress concentration effects influenced by elastic modulus ratio between fiber and matrix. The composite modulus, thus far, is calculated by changing the fiber aspect ratio and volume fraction. It is found that the comparison with FEA(Finite Element Analysis) results gives a good agreement with the present theory (NSLT). It is also found that the NSLT is more accurate than the SLT(Shear Lag Theory) in short fiber regime when compared by FEA results. However, The modulus predicted by NSLT becomes similar values that of SLT when the fiber aspect ratio increases. Finally, It is shown that the present model has the capability to predict the composite modulus correctly in elastic regime.