• Title/Summary/Keyword: 동적 전단계수

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Simulation of Dynamic in-situ Soil Properties for the Centrifuge Test (Hualien Site in Taiwan) (원심 모형 시험을 위한 동적 현장 지반 모사 기법 연구(대만 화련 지반))

  • Ha, Jeong-Gon;Lee, Sei-Hyun;Choo, Yun-Wook;Kim, Se-Hee;Kim, Dong-Soo
    • Journal of the Earthquake Engineering Society of Korea
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    • v.16 no.4
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    • pp.27-36
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    • 2012
  • The simulation of the field dynamic soil properties for soil modeling in the centrifuge test is important. In this study, the process of soil modeling based on the shear wave velocity profile is developed. From the resonant column test in each confining pressure, the shear wave velocity profile is expected and the modeling condition is determined by comparing it with that in the field. During the dynamic centrifuge test, the bender element test is performed for measuring the in-flight shear wave velocity profile, and the applicability of the proposed method was verified. This modeling method is applied to the centrifuge test of the Hualien Large-Scale Seismic test.

Dynamic Properties and Settlement Characteristics of Korea Weathered Granite Soils (화강풍화토의 동적 물성치와 침하특성에 대한 연구)

  • Park, Jong-Gwan;Kim, Yeong-Uk;Lee, In-Mo
    • Geotechnical Engineering
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    • v.9 no.2
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    • pp.5-14
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    • 1993
  • Weathered granite soil is the most representative as a surface soil in Korea. In this paper, the dynamic properties and settlement characteristics of Korea granite soil are studied through the dynamic triaxial compression tests. The dynamic characteristics are very important on the analysis of the foundations under dynamic loading such as machine vibration and earthquake. Soil samples having different grain sixtes were prepared at the relative densities between 80oA and 90oA and tested to measure shear moduli and damping ratios at each level of shear strain. The measured shear moduli of weathered granite soils showed large variations according to the grain sizes, confining pressures, relative densities and shear strains. Sandy weathered granite had a little larger dynamic properties than the average values of the sand studied by Seed and Idriss. Pot the well compacted granite soils, little residual settlements occured due to dynamic loading.

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Effects of Hihh Amplitude Prestraining Vibrations on Shear Modulus of Sands (고 변형률 반복 진동이 모래의 전단 탄성계수에 미치는 영향)

  • ;Stokoe, K.H.Il
    • Geotechnical Engineering
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    • v.8 no.1
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    • pp.19-28
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    • 1992
  • Recently, testing equipment which can run resonant column test altogether with the torsional shear test at the very highly controlled condition was developed at the University of Texas at Austin(U.S.A). With this equipment, the effects of high amplitude pre-straining vibrations on the dynamic properties of clean sands were studied. Tests showed the following results. Low amplitude shear modulus was gradually increased with little void ratio change as the number of high amplitude vibration cycles increased. Variation of volumetric strain with confining pressure for the pre -strained specimen under vibration was smaller than that of fresh specimen. Also the slope of the diagram for shear modulus and confining pressure relationship of the prestrained specimen was smaller than that of fresh specimens. These results agreed well with the analytical results.

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Dynamic Deformation Characteristics of Granite Weathered Soils Using RC/TS Tests (공진주/비틂전단시험을 이용한 화강풍화지반의 동적변형특성)

  • Kim, Dong-Soo;Ko, Dong-Hee;Youn, Jun-Ung
    • Journal of the Korean GEO-environmental Society
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    • v.5 no.1
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    • pp.35-46
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    • 2004
  • In Korea, around one - third of the country is occupied by granite, and granite weathered soils are widely distributed. Most of the research on this soil has been performed using reconstituted specimens because of the extreme difficulty of undisturbed sampling due to the sensitive particle structures. Therefore, the comparisons of deformational characteristics, which is expressed in terms of shear and Young's moduli and damping ratio, obtained from the undisturbed and reconstituted specimens are important for the reliable understanding of soil behavior. In this study, the resonant column and torsional shear tests were performed on granite weathered soils in Korea, and the deformation characteristics of undisturbed and reconstituted soil on granite weathered soils were evaluated and compared.

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Theoretical Modeling of the Resonant Column Testing with the Viscosity of a Specimen Considered (점성을 고려한 공진주 실험의 이론적 모델링)

  • 조성호;황선근;권병성;강태호
    • Journal of the Korean Geotechnical Society
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    • v.19 no.4
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    • pp.145-153
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    • 2003
  • The resonant column testing determines the shear modulus and material damping factor dependent on the shear strain magnitude, based on the wave-propagation theory. The determination of the dynamic soil properties requires the theoretical formulation of the dynamic behavior of the resonant column testing system. One of the theoretical formulations is the use of the wave equation for the soil specimen in the resonant column testing device. Wood, Richart and Hall derived the wave equation by assuming the linear elastic soil, and didn't take the material damping into consideration. Hardin incorporated the viscoelastic damping of soil in the wave equation, but he had to assume the material damping factor for the determination of the shear modulus. For the better theoretical formulation of the resonant column testing, this study derived a new wave equation to include the viscosity of soil, and proposed an approach for the solution. Also, in this study, the equation of motion for the testing system, which is another approach of the theoretical formulation of the resonant column testing, was also derived. The equation of motion leads to the better understanding of the resonant column testing, which includes the dynamic magnification factor and the phase angle of the response. For the verification of the proposed equation of motion for the resonant column testing, the finite element analysis was performed for the resonant column testing. The comparison of the dynamic magnification factors and the phase angles far the system response were performed.

A Study of Dynamic Instability for Sigmoid Functionally Graded Material Plates on Elastic Foundation (탄성지반위에 놓인 S형상 점진기능재료(FGM)판의 동적 불안정성에 관한 연구)

  • Lee, Won-Hong;Han, Sung-Cheon;Park, Weon-Tae
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.28 no.1
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    • pp.85-92
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    • 2015
  • This article presents the dynamic instability response of sigmoid functionally graded material plates on elastic foundation using the higher-order shear deformation theory. The higher-order shear deformation theory has ability to capture the quadratic variation of shear strain and consequently shear stress through the plate thickness. The governing equations are then written in the form of Mathieu-Hill equations and then Bolotin's method is employed to determine the instability regions. The boundaries of the instability regions are represented in the dynamic load and excitation frequency plane. The results of dynamic instability analysis of sigmoid functionally graded material plate are presented using the Navier's procedure to illustrate the effect of elastic foundation parameter on dynamic response. The relations between Winkler and Pasternak elastic foundation parameter are discussed by numerical results. Also, the effects of static load factor, power-law index and side-to-thickness ratio on dynamic instability analysis are investigated and discussed. In order to validate the present solutions, the reference solutions are used and discussed. The theoretical development as well as numerical solutions presented herein should serve as reference for the dynamic instability study of S-FGM plates.

Measurement of Dynamic Elastic Constants of RPV Steel Weld due to Localized Microstructural Variation (원자로 용접부의 국부적 미세조직 변화에 따른 동적탄성계수 측정)

  • Cheong, Yong-Moo;Kim, Joo-Hag;Hong, Jun-Hwa;Jung, Hyun-Kyu
    • Journal of the Korean Society for Nondestructive Testing
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    • v.20 no.5
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    • pp.390-396
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    • 2000
  • The dynamic elastic constants of the simulated weld HAZ (heat-affected zone) of SA 508 Class 3 reactor pressure vessel (RPV) steel were investigated by resonant ultrasound spectroscopy (RUS). The resonance frequencies of rectangular parallelepiped samples woe calculated from the initial estimates of elastic stiffness $c_{11},\;c_{12}\;and\;c_{44}$ with an assumption of isotropic property, dimension and density. Through the comparison of calculated resonant frequencies with the measured resonant frequencies by RUS, very accurate elastic constants of SA 508 Class 3 steel were determined by iteration and convergence processes. Clear differences of Youngs modulus and shear modulus were shown from samples with different thermal cycles and microstructures. Youngs modulus and shear modulus of samples with fine-grained bainite were higher than those with coarse-grained tempered martensite. This tendency was confirmed from other results such as micro-hardness test.

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Cyclic Strength and Deformation Characteristics of Marine Cohesive Soil (해성 점성토의 동적 강도 및 변형 특성)

  • Kim, Yong-Seong;Seo, Min-Woo;Oh, Sang-Eun
    • Journal of The Korean Society of Agricultural Engineers
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    • v.54 no.3
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    • pp.159-168
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    • 2012
  • 본 연구에서는 해성 점성토에 대하여 반복 삼축시험을 실시하고 응력-변형률 관계 및 유효응력경로 특성 분석을 통해 동적 변형 및 강도 특성을 조사하였다. 시험에 사용된 시료는 일본 도쿠시마현의 코마츠시마 항 인근에서 채취된 점성토이며, 반복 삼축시험으로 동적 비배수 삼축시험, 동적 비배수 삼축시험 후 동적 삼축변형시험, 다단계 동적 비배수 삼축시험, 동적 삼축 변형시험 등 4종류의 시험을 수행하고, 시험 주파수로서 0.1 및 0.01 Hz을 적용하였다. 본 연구 결과 0.01 Hz로 수행된 동적 삼축시험 결과는 0.1 Hz로 수행된 삼축시험 결과보다 평균유효응력의 감소량이 크며, 반복 하중은 해성 점성토의 구조적 약화를 초래하고 초기 거동시 발생하는 간극수압과 밀접하게 관련이 있는 것으로 나타났다. 또한 미소변형률 영역에서 등가 탄성계수는 시험 횟수가 증가함에 따라 점차 감소하며, 감쇠비는 점차 증가하는 것으로 보아 변형계수는 반복 하중으로 인한 전단변형률의 축척에 따른 변형률 의존 거동에 관련하는 것으로 판단된다.

Dynamic Behavior of Unsaturated Decomposed Mudstone Soil Under Low Strain Amplitude (저변형률하 불포화 이암풍화토의 동적거동)

  • Huh, Kyung-Han;Chung, Choong-Sun;Bae, Joong-Seon
    • Journal of the Korean Society of Hazard Mitigation
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    • v.4 no.2 s.13
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    • pp.19-27
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    • 2004
  • The interest in the dynamic properties of soils has increased strongly because of earthquake, heavy traffic, and foundations undergo high amplitude of vibrations. Most of soils in Korean peninsula are composed of granite soils, especially the decomposed mudstone soils are widely spread in Pohang areas, Kyong-buk province. Therefore, it is very important to investigate the dynamic properties of these types of soils. The most important soil parameters under dynamic loadings are shear modulus and material dampings. Furthermore, few definitive data exist that can evaluate the behavior of unsaturated decomposed mudstone soils under dynamic loading conditions. The investigations described in this paper is designed to identify the shear modulus and damping ratio due to a surface tension for the unsaturated decomposed mudstone soils under low and high strain amplitude. For this purpose, the resonant column test and the cyclic triaxial test were performed. Test results and data have shown that the optimum saturated degree of decomposed mudstone soils under low and strain amplitude is $32{\sim}37%$ which is higher than that of decomposed granite due to the amount of fine particles as well as the type and proportion of chief rock-forming minerals.

Effects of Accelerated Thermal Aging on Dynamic Properties of Laminated Rubber Bearings (적층고무받침의 가속 열 노화 동적특성 영향)

  • Oh, Ju;Jung, Hie-Young
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.30 no.5A
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    • pp.417-424
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    • 2010
  • The dynamic properties of laminated rubber bearings used as isolators in structures could be significantly deteriorated because of the change of microstructure in rubber caused by thermal aging. As a result, a catastrophic failure of bridges and buildings unexpectedly occurs when they are subjected to earthquake attack. Here, the dynamic properties of laminated rubber bearings before and after different of compression-shear loading and repeated cycles loadings, ultimated failure test with thermal aging were first measured and compared to each other. The experimental results, the effects of thermal aging on the shear stiffness, energy absorption, and equivalent damping coefficient of laminated rubber bearings are investigated. It is found that the deterioration of dynamic properties of laminated rubber bearings caused by thermal aging is significant and should be taken into account in designing rubber bearings.