• Title, Summary, Keyword: 탄성계수

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Adaptation of Modal Parameter and Elastic Modulus Estimation Method for PSC Bridge Based on Ambient Vibration (상시 진동 계측을 기반으로 한 PSC 교량의 모드계수 및 탄성계수 추정기법 적용)

  • Lee, Sung-Jin;Kim, Saang-Bum;Choi, Kyu-Yong;Lee, Tae-Young
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.574-577
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    • 2007
  • 본 논문에서는 실 시공 중인 PSC 교량에 대하여 풍하중에 의한 상시 진동 계측 자료을 기반으로, 교량의 동특성(고유진동수, 모드형상)을 추정하였으며, 이를 바탕으로 대상 교량의 탄성계수를 추정하여 정적 계측을 통한 탄성계수 결과와 비교하였다. 본 논문에서 사용한 동특성 추정 기법은, 대표적인 주파수 영역 해석 방법인 Frequency Domain Decomposition(FDD) 방법과 시간영역 해석 방법인 Stochastic Subspace Identification(SSI) 방법을 이용하였다. 탄성계수 추정은 유한요소모델과 계측 결과를 이용하여 두 개의 결과 차이가 수렴하도록 하는 반복 계산을 통해 탄성계수를 추정하였다. 우선, 탄성계수 추정 기법의 검증을 위해, 수치 해석을 통하여 그 기법을 검증하였으며, 해석 결과 정확한 탄성계수값을 추정하였으며, 이를 통해 본 논문에서 적용한 탄성계수 추정법에 대한 신뢰도를 확인하였다. 이를 바탕으로 사용된 추정 기법을 실 교량에 적용하기 위해 실제 상시 진동 계측 값을 바탕으로 실교량의 동특성 및 탄성계수를 추정하였다. FDD 및 SSI 기법을 통한 모드 해석 결과, 두 기법 모두 유사한 결과를 나타내어 FDD 및 SSI 두 방법에 대한 결과의 신뢰도를 확인 할 수 있었다. 추정 탄성계수 값은 거더 단면내 설치한 응력계 및 변형률계를 통한 계측 결과값의 범위 내에 있음을 확인하였다. 따라서 본 논문에서 적용한 교량의 상시 진동 데이터를 바탕으로 한동특성 및 탄성계수 추정법이 구조물의 대략적인 탄성계수 및 이에 따른 구조물의 전체적인 건전도를 파악하는데 도움이 되리라 생각된다.

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A Study on Overhead Distribution Conductors for Modulus of Elasticity and Coefficient of Linear Expansion (가공배전선 탄성계수 및 선팽창계수 성능측정 연구)

  • Wong, Yoon-Chan;Cho, Si-Hyung;Park, Jung-Shin;Kim, Byung-Geol;Kim, Sang-Soo
    • Proceedings of the KIEE Conference
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    • pp.7-8
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    • 2006
  • 가공배전선로의 이도는 탄성계수와 선팽계수에 따라 온도 및 장력의 변화에 대하여 다른 변화를 나타낸다. 따라서 본 연구에서는 정확한 이도설계와 선로의 장기신뢰성 확보를 위해 배전선 주요 규격에 대하여 탄성계수와 선팽창계수를 실측하여 계산값과 측정값에 어떠한 차이가 있는지를 비교하였다. 시험결과 전선의 탄성계수와 선팽창계수는 제작공정상의 여러 요인들에 의하여 영향을 받는 것으로 나타났으며, 이도설계시 탄성계수와 선팽창계수는 배전선의 측정값을 적용하는 것이 바람직 한 것으로 나타났다.

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Inversion of SAW Dispersion Data to Determine the Elastic Constants of a Thin film (표면파속도와 역산법에 의한 박막탄성계수 산출)

  • 김진오
    • Journal of the KSME
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    • v.34 no.7
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    • pp.510-516
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    • 1994
  • 탄성파의 속도는 파동 전파 매질의 밀도와 탄선계수에 달려 있으므로, 박막이 입혀진 기판에서 전파하는 표면파에 대해서 기판과 박막의 밀도와 탄성계수 및 박막의 두께 등을 알면 전파 속 도를 계산할 수 있다. 박막의 탄성계수를 모르는 경우에는 표면파 속도를 측정하여 역으로 탄 성계수를 산출할 수 있다. 이러한 역산과정에는 일반적인 비선형 방정식의 curve-fitting에 이용될 수 있는 simplex법이 효율적으로 활용된다. 이 글에서는 표면파 속도를 측정하고 그 데이터로 부터 역산하여 박막의 탄성계수를 구하는 원리와 과정을 설명한다.

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Analysis of Confinement Effectiveness for FRP Confined Concrete Columns (FRP로 구속된 콘크리트 압축부재의 구속효과 분석)

  • Choi, Eunsoo;Choi, Seung-Hwan
    • Journal of The Korean Society of Civil Engineers
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    • v.31 no.1A
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    • pp.19-24
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    • 2011
  • Concrete columns strengthening effect due to FRP (Fiber Reinforced Polymer) confinement depends on the elastic modulus of the FRP. This study analyzes the retrofitting effect of FRP confinements according to elastic modulus of FRPs using the existing data and suggests a practical model to assess the strengthening effect. This study subdivides the FRP elastic modulus into three parts based on normal concrete and steel elastic modulus. The slope and the y-axis intersection seem to increase with increasing FRP elastic modulus. In addition, the strengthening effect does not develop up to some amount of FRP confinement having relatively smaller elastic modulus than the compressive elastic modulus of concrete. In this case, a linear model to assess the strengthening effect is hard to be used. Thus, this study suggests that the FRP jackets having 2 times larger elastic modulus than that of concrete are recommended to be used for retrofit of concrete and that a linear model can be applied for the case. The suggested model shows nearly the same result regardless to the restraint of the y-axis intersection. This has been observed at the model of steel confinement and, thus, is a reliable result.

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.

Estimation of Modulus of Elasticity in High Strength Concrete (고강도 콘크리트의 탄성계수 추정)

  • Oh, Min-Ho;Kim, Tae-Wan;Choi, Jin-Woong;Cui, Jie;Kim, Hyung-Jun;Park, Sun-Kyu
    • Proceedings of the Korea Concrete Institute Conference
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    • pp.413-414
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    • 2010
  • Many researchs shows that modulus of elasticity in manual overestimates real modulus of elasticity of concrete as strength gets higher. In 2007 KCI Manual, formula in modulus of elasticity has revised that it should be demonstrated. In this study, modulus of elasticity in high strength was estimated by experiment and experimental value was compared with manual value.

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Prediction of Equivalent Shear Modulus of Sandwich Panel Core (샌드위치 판넬 코어의 등가 전단 탄성계수 예측)

  • Lee, Sang-Youn;Yun, Su-Jin;Park, Dong-Chang;Yoon, Hyun-Gull
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • pp.123-126
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    • 2011
  • The Finite element modelling is carried to predict the equivalent shear modulus of the Egg-Box core. Homogeneous material H130-foam core is employed to verify the prediction method of equivalent shear modulus. It shows a good agreement between the results of FE calculation and the values available in the reference. As a result of the present work, the equivalent shear modulus of Egg-Box core at various temperatures can be obtained.

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Comparison of Elastic Moduli of Subgrade Soils Using Plate Loading Test, Soil Stiffness Gauge and Dynamic Cone Penetrometer (평판재하시험, 흙강성측정기 및 동적콘관입시험기를 이용한 노상토의 탄성계수 비교)

  • Kim, Kyu-Sun
    • Journal of the Korean Geotechnical Society
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    • v.31 no.3
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    • pp.63-72
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    • 2015
  • This paper describes the correlation and relationship between elastic moduli measured by three stiffness measurement methods with different mechanical characteristics to evaluate the compaction characteristics of subgrade soils. The Soil Stiffness Gauge (SSG) with very small strain (${\approx}0.001%$) ranges, static Plate Loading Test (PLT) with mid-level strain (${\approx}0.01{\sim}0.1%$) ranges, and Dynamic Cone Penetrometer (DCP) using penetration resistance were implemented to measure the elastic modulus. To use the elastic modulus measured by different measurement methods with a wide range of strain in practice, it is required to identify the correlation and relationship of measured values in advance. The comparison results of the measured elastic moduli ($E_{SSG}$, $E_{PLT}$, $E_{DCP}$) using the three measurement methods for domestic and overseas subgrade soils under various conditions indicate that the evaluated elastic modulus relies on the types of soils and the level of stress condition. The correlation analysis of the measured elastic moduli except the data of cement treated soils indicates that the static elastic modulus ($E_{PLT}$) is evaluated as about 60 to 80% of the dynamic elastic modulus ($E_{SSG}$). Unusual soils such as cement treated soils are required to be corrected by the stress correction during the correlation analysis with typical soils, because these types of soils are sensitive to the stress condition when measuring the static elastic modulus ($E_{PLT}$) of soils. In addition, when considering the use of DCP data for the evaluation of the elastic modulus ($E_{DCP}$), the measured data of the elastic modulus less than 200 MPa show more reliable correlation.

Development and Assessment for Resilient Modulus Prediction Model of Railroad Trackbeds Based on Modulus Reduction Curve (탄성계수 감소곡선에 근거한 철도노반의 회복탄성계수 모델 개발 및 평가)

  • Park, Chul Soo;Hwang, Seon Keun;Choi, Chan Yong;Mok, Young Jin
    • Journal of The Korean Society of Civil Engineers
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    • v.29 no.2C
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    • pp.71-79
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    • 2009
  • This study is to develope the resilient modulus prediction model, which is the function of mean effective principal stress and axial strain, for three types of railroad trackbed materials such as crushed stone, weathered granite soil, and crushed-rock soil mixture. The model consists of the maximum Young's modulus and nonlinear values for higher strain, analogous to dynamic shear modulus. The maximum value is modeled by model parameters, $A_E$ and the power of mean effective principal stress, $n_E$. The nonlinear portion is represented by modified hyperbolic model, with the model parameters of reference strain, ${\varepsilon}_r$ and curvature coefficient, a. To assess the performance of the prediction models proposed herein, the elastic response of a test trackbed near PyeongTaek, Korea, was evaluated using a 3-D elastic multilayer computer program (GEOTRACK). The results were compared with measured elastic vertical displacement during the passages of freight and passenger trains at two locations, whose sub-ballasts were crushed stone and weathered granite soil, respectively. The calculated vertical displacements of the sub-ballasts are within the order of 0.6mm, and agree well with measured values. The prediction models are thus concluded to work properly in the preliminary investigation.

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Evaluation of Freeze-Thaw Effect on the Modulus of Subgrade Soils from Impact Resonance Test (충격공진시험을 이용한 동결.융해에 따른 노상토의 탄성계수 평가)

  • Lee, Jae-Hoan;Kweon, Gi-Chul
    • International Journal of Highway Engineering
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    • v.12 no.3
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    • pp.71-77
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    • 2010
  • Anti-freezing layer does not used in case of non frost heaving in subgrade soils. In this case, the modulus of subgrade soils were varied with freezing and thaw cycles under non frost heaving. That effect should be properly considered in pavement design. Impact resonance test that is nondestructive testing method was used for continuously determining the modulus of subgrade soils during freezing and thaw cycle. The modulus of subgrade soils was identical with freezing and thaw cycles under closed freezing and thaw system which is no water supplement into specimen during testing. There was also no difference in the modulus of subgrade soil between before and after freezing-thaw cycles for all specimens with different water content and density. That is thaw-weakening of subgrade soils do not occur under closed freezing and thaw system. The moduli at freezing conditions are varied with water content and density, but it can be ignored in practical design sense.