• Title, Summary, Keyword: modulus

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Analysis on Relationship between FWD Back-calculated Modulus and Dynamic Modulus of Asphalt Layers for Existing Asphalt Pavements (공용중인 아스팔트 포장의 아스팔트층 동탄성계수와 FWD 역산 탄성계수의 상관관계 분석)

  • Park, Hee Mun;Park, Hong Joon
    • International Journal of Highway Engineering
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    • v.17 no.5
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    • pp.25-31
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    • 2015
  • PURPOSES: The objective of this study is to analyze the relationship between the FWD back-calculated modulus and dynamic modulus of asphalt layers for existing asphalt pavements. METHODS: To evaluate the dynamic modulus of the asphalt mixture in the existing and new asphalt layers, the uniaxial direct tension test was conducted on small asphalt specimens obtained from the existing asphalt-covered pavements. A dynamic modulus master curve was estimated by using the uniaxial direct tension test for each asphalt layer. The falling weight deflectometer (FWD) testing was conducted on the test sections, and the modulus values of pavement layers were back-calculated using the genetic algorithm and the finite element method based back-calculation program. The relationship between measured and back-calculated asphalt layer moduli was examined in this study. The normalized dynamic modulus was adopted to predict the stiffness characteristics of asphalt layers more accurately. RESULTS: From this study, we can conclude that there is no close relationship between dynamic modulus of first layer and back-calculated asphalt modulus. The dynamic moduli of second and third asphalt layers have some relation with asphalt stiffness. Test results also showed that the normalized dynamic modulus of the asphalt mixture is closely related to the FWD back-calculated modulus with 0.73 of R square value. CONCLUSIONS: The back-calculated modulus of asphalt layer can be used as an indicator of the stiffness characteristics of asphalt layers in the asphalt-covered pavements.

Multi-Modulus Blind Equalization Algorithm (다중 Modulus 블라인드 등화 알고리즘)

  • Choi, Ik-Hyun;Kim, Chul-Min;Oh, Kil-Nam;Choi, Soo-Chul
    • Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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    • v.9 no.2
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    • pp.465-468
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    • 2005
  • MMA(Multi-Modulus Algorithm) is inferior at a initial equalization in high ISI(intersymbol interference), because it is the inaccurate decision. To improve this probel SMMA(Sliced Multi-Modulus Algorithm) is based on using the MCMA(Modified Constant Modulus Algorithm). SMMA is a improved capability than MMA in high SNR but is inaccurate decision in low SNR. In this paper, We propose some multi-modulus blind equalization algorithm scheme. It is a method of operation in some multi-modulus algorithm which does no obstruct a convergence property at the initial equalization in the low SNR. Proposed algorithm improves the steady-state performance. And it uses residual ISI of the equalizer output in order to decide the optimum switching time between the single modulus and the multi-modulus algorithm.

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A Suggestion of an Empirical Equation for Shear Modulus Reduction Curve Estimation of Sandy Soils (사질토 전단탄성계수 감소곡선 산정을 위한 경험식 제안)

  • Park, Dug-Keun
    • Journal of the Korean Geotechnical Society
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    • v.18 no.3
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    • pp.127-138
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    • 2002
  • In dynamic analyses such as seismic ground response and soil-structure interaction problems, it is very crucial to obtain accurate dynamic shear modulus of soil deposit. In this study, an extensive data base of available experimental data is compiled and reanalyzed to establish a simple empirical formula for the dynamic shear modulus reduction curve to cover wide range of strain for sandy soils. The proposed empirical equation is to represent the dynamic shear modulus degradation with strain in terms of low-amplitude dynamic shear modulus and effective mean confining Pressure, since those factors have the most significant effect on the Position and shape of the shear modulus reduction curve for nonelastic soils. If low-amplitude shear modulus is measured, degraded modulus at any shear strain amplitude can be calculated using the proposed equation.

A study on dynamic modulus of self-consolidating rubberized concrete

  • Emiroglu, Mehmet;Yildiz, Servet;Kelestemur, M. Halidun
    • Computers and Concrete
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    • v.15 no.5
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    • pp.795-805
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    • 2015
  • In this study, dynamic modulus of elasticity of self-consolidating rubberized concrete is evaluated by using results of ultrasonic pulse velocity and resonance frequency tests. Additionally, correlation between dynamic modulus of elasticity and compressive strength results is compared. For evaluating the dynamic modulus of elasticity of self-consolidating rubberized concrete, prismatic specimens having $100{\times}100{\times}500$ mm dimensions are prepared. Dynamic modulus of elasticity values obtained by non-destructive measurements techniques are well agreed with those given in the literature.

Empirical Correlation for the Estimation of Resilient Modulus of Cohesive Soils (점성토의 회복탄성계수 추정을 위한 경험식)

  • 이우진
    • Proceedings of the Korean Geotechical Society Conference
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    • pp.259-264
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    • 1994
  • The 1986 AASHTO Guide for the Design of Pavement Structures introduced the resilient modulus as a definitive material property to characterize roadbed soil. Although the incorporation of resilient modulus represents a significant acvance in pavement design practice, the test procedure for resilient modulus is complicated and time-consuming. Therefore, it is necessary to develop data base of resilient modulus for the soils frequently encountered; and to develop the reliable correlations between resilient properties and parameters from simple routine tests, In this study, resilient modulus tests were performed on five cohesive soils sampled from in-service subgrades. The stress at 1 percent axial strain in unconfined compression test(su1.0%) was found as a good indicator of the resilient modulus, and unique relationship between Mg and Su1.0% was obtained. A simple chart to estimate the resilient modulus at different levels of confining stress and deviator stress was also developed.

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Sliced Multi-modulus Blind Equalization Algorithm

  • Abrar, Shafayat;Axford, Roy A. Jr.
    • ETRI Journal
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    • v.27 no.3
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    • pp.257-266
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    • 2005
  • Many multi-modulus blind equalization algorithms (MMA) have been presented in the past to overcome the undesirable high misadjustment exhibited by the well-known constant modulus algorithm. Some of these MMA schemes, specifically tailored for quadrature amplitude modulation (QAM) constellations, have also been proved to fix the phase offset error without needing any rotator at the end of the equalizer stage. In this paper, a new multi-modulus algorithm is presented for QAM signals. The contribution lies in the technique to incorporate the sliced symbols (outcomes of decision device) in the multi-modulus-based weight adaptation process. The convergence characteristics of the proposed sliced multi-modulus algorithm (S-MMA) is demonstrated by way of simulations, and it is shown that it gives better steady-state performance in terms of residual inter-symbol interference and symbol-error rate. It has also been shown that the proposed algorithm exhibits lesser steady-state misadjustment compared to the best reported MMA.

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Estimation of Deformation Modulus of Cemented Sand using CPT and DMT (CPT와 DMT를 이용한 고결모래의 변형계수 추정)

  • Lee, Moon-Joo;Choi, Sung-Kun;Hong, Sung-Jin;Lee, Woo-Jin
    • Proceedings of the Korean Geotechical Society Conference
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    • pp.484-491
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    • 2008
  • The purpose of this study is to compare the cementation effect on cone resistance and DMT indices and to evaluate the deformation characteristic of cemented sand using cone resistance and dilatometer modulus. Specimens of various relative densities with three different cementation levels are prepared in a large calibration chamber under different vertical stress levels. Test result shows that the cone resistance and dilatometer modulus underestimate the deformation modulus of cemented sand, since in situ penetration tests such as CPT and DMT damage the cementation bonds during penetration. By regression analysis, the constrained modulus of cemented sand is related with the cone resistance and the dilatometer modulus.

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Variability of subgrade reaction modulus on flexible mat foundation

  • Jeong, Sangseom;Park, Jongjeon;Hong, Moonhyun;Lee, Jaehwan
    • Geomechanics and Engineering
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    • v.13 no.5
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    • pp.757-774
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    • 2017
  • The subgrade reaction modulus of a large mat foundation was investigated by using a numerical analysis and a field case study. The emphasis was on quantifying the appropriate method for determining the subgrade reaction modulus for the design of a flexible mat foundation. A series of 3D non-linear FE analyses are conducted with special attention given to the subgrade reaction modulus under various conditions, such as the mat width, mat shape, mat thickness, and soil condition. It is shown that the distribution of the subgrade reaction modulus is non-uniform and that the modulus of subgrade reaction at both the corners and edges should be stiffer than that at the center. Based on the results obtained, a simple modification factor for the subgrade reaction modulus is proposed depending on the relative positions within the foundation in weathered soil and rocks.

Measuring Young's Modulus of Materials by Using Accelerometer (가속도계를 이용한 재료의 영계수 측정방법)

  • Sohn, Chang-Ho;Park, Jin-Ho;Yoon, Doo-Byung;Chong, Ui-Pil;Choi, Young-Chul
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.16 no.11
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    • pp.1158-1164
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    • 2006
  • For the description of the elastic properties of linear objects a convenient parameter is the ratio of the stress to the strain, a parameter called the Young's modulus of the material. Young's modulus can be used to predict the elongation or compression of an object as long as the stress is less than the yield strength of the material. Conventional method for estimating Young's modulus measured the ratio of stress to corresponding strain below the proportional limit of a material using a tensile testing machine. But the method needs precision specimens and expensive equipment. In this paper, we proposed method for estimating Young's modulus using accelerometer. The basic idea comes from that the wave velocity is different as the Young's modulus. To obtain Young's modulus, a group velocity is obtained. It is difficult to measure group velocity. This is because plate medium has a dispersive characteristics which has different wave speed as frequency. In this paper, we used Wigner-Ville distribution to measure group velocity. To verify the proposed method, steel and acryl plate experiments have been performed. Experimental results show that the proposed method is powerful for estimating Young's modulus.

The Variation Rate of Shear Modulus for Anisotropic Magneto-rheological Elastomer due to Volume Fraction of CIP (CIP 부피비에 따른 이방성 MRE의 전단계수 변화율)

  • Jeong, Un-Chang;Yoon, Ji-Hyun;Yang, In-Hyung;Lee, You-Yub;Oh, Jae-Eung
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.21 no.12
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    • pp.1132-1137
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    • 2011
  • MRE(magneto-rheological elastomers) is a material which shows reversible and various modulus in magnetic field. Comparing to conventional rubber vibration isolator, MREs are able to absorb vibration of broader frequency range. These characteristic phenomena result from the orientation of magnetic particles named carbonyl iron powder(CIP) in rubber matrix. In this paper, simulation on variation rate of shear modulus for anisotropic MRE due to volume fraction of CIP and an effective permeability model was applied to predict the field-induced shear modulus of MREs. Also, the variation rate of shear modulus for anisotropic MRE was derived using magneto-mechanical theory. Based on Maxwell-Garnett mixing rule, the increment of shear modulus was calculated to evaluate the shear modulus of MREs with column structure of CIP due to induced current. The simulation results on variation rate of shear modulus can be applied to the variable mechanical system of MRE such as tunable vibration absorber, stiffness variable bush and mount.