• Title/Summary/Keyword: discrete element modeling

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Winkler spring behavior in FE analyses of dowel action in statically loaded RC cracks

  • Figueira, Diogo;Sousa, Carlos;Neves, Afonso Serra
    • Computers and Concrete
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    • v.21 no.5
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    • pp.593-605
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    • 2018
  • A nonlinear finite element modeling approach is developed to assess the behavior of a dowel bar embedded on a single concrete block substrate, subjected to monotonic loading. In this approach, a discrete representation of the steel reinforcing bar is considered, using beam finite elements with nonlinear material behavior. The bar is connected to the concrete embedment through nonlinear Winkler spring elements. This modeling approach can only be used if a new constitutive model is developed for the spring elements, to simulate the deformability and strength of the concrete substrate. To define this constitutive model, an extensive literature review was conducted, as well as 3 experimental tests, in order to select the experimental data which can be used in the calibration of the model. Based on this data, an empirical model was established to predict the global dowel response, for a wide range of bar diameters and concrete strengths. This empirical model provided the information needed for calibration of the nonlinear Winkler spring model, valid for dowel displacements up to 4 mm. This new constitutive model is composed by 5 stages, in order to reproduce the concrete substrate response.

Interactive analysis of a building fame resting on pile foundation

  • Chore, H.S.
    • Coupled systems mechanics
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    • v.3 no.4
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    • pp.367-384
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    • 2014
  • The study deals with the physical modeling of a typical single storeyed building frame resting on pile foundation and embedded in cohesive soil mass using the finite element based software SAP-IV. Two groups of piles comprising two and three piles, with series and parallel arrangement thereof, are considered. The slab provided at top and bottom of the frame along with the pile cap is idealized as four noded and two dimensional thin shell elements. The beams and columns of the frame, and piles are modeled using two noded one dimensional beam-column element. The soil is modeled using closely spaced discrete linear springs. A parametric study is carried out to investigate the effect of various parameters of the pile foundation, such as spacing in a group and number of piles in a group, on the response of superstructure. The response considered includes the displacement at the top of the frame and bending moment in columns. The soil-structure interaction effect is found to increase the displacement in the range of 38 -133% and to increase the absolute maximum positive and negative moments in the column in the range of 2-12% and 2-11%. The effect of the soil- structure interaction is observed to be significant for the type of foundation and soil considered in this study. The results obtained are compared further with those of Chore et al. (2010), wherein different idealizations were used for modeling the superstructure frame and sub-structure elements (foundation). While fair agreement is observed in the results in either study, the trend of the results obtained in both studies is also same.

Vibration Characteristics of a Motorcycle Body (이륜차 차체의 진동특성)

  • 박보용
    • Journal of the Korean Society for Precision Engineering
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    • v.15 no.1
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    • pp.169-176
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    • 1998
  • This paper presents the vibration characteristics of a motorcycle body frame. In order to study the excitation mechanism. for example, of handle vibration, discrete models and finite element model are developed for the calculation of natural frequencies and mode shapes of the driveline and body. which can lead to the resonances. Experiments are also conducted to compare with the analytical results From the various kinds of vibration reduction methods, the technical realizable one is presented to reduce the handle vibration responses at the start of driving.

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Rheological Modeling of Nanoparticles in a Suspension with Shear Flow (전단 흐름을 갖는 서스펜션 내부 나노 입자의 유변학적 특성 연구)

  • Kim, Gu;Fukai, Jun;Hironaka, Shuji
    • Applied Chemistry for Engineering
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    • v.30 no.4
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    • pp.445-452
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    • 2019
  • Shear thickening is an intriguing phenomenon in the fields of chemical engineering and rheology because it originates from complex situations with experimental and numerical measurements. This paper presents results from the numerical modeling of the particle-fluid dynamics of a two-dimensional mixture of colloidal particles immersed in a fluid. Our results reveal the characteristic particle behavior with an application of a shear force to the upper part of the fluid domain. By combining the lattice Boltzmann and discrete element methods with the calculation of the lubrication forces when particles approach or recede from each other, this study aims to reveal the behavior of the suspension, specifically shear thickening. The results show that the calculated suspension viscosity is in good agreement with the experimental results. Results describing the particle deviation, diffusivity, concentration, and contact numbers are also demonstrated.

Stability analysis of pump using finite element method (유한요소법에 의한 펌프축계의 안정성해석)

  • 양보석
    • Journal of Advanced Marine Engineering and Technology
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    • v.10 no.4
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    • pp.31-40
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    • 1986
  • With the tendency toward high speed and high pressure in centrifugal pumps, the problem of sub-synchronous vibration has arisen, caused by the hydraulic forces of the working fluid, such as wearring, balance piston, impeller, etc.. These forces can drastically alter the rotor critical speeds and stability characteristics, and can be acted significant destabilizing forces. For preventing such self-excited vibration, the desing of the rotor system needs, which would secure the stability of the machine. In this paper, a procedure is presented for dynamic modeling of rotor-bearing-seal-impeller systems which consist of rigid disks, distributed parameter finite rotor elements and discrete bearings, seals and impellers. A finite element model including the effects of rotatory inertia and gyroscopic moments is developed using the consistent matrix approach. The technique of dynamic matrix reduction is applied to the shaft matrices to reduce them to a set of matrices of dynamic of significantly fewer degrees of freedom. The representation of bearing, seal and impeller elements is in term of linearized stiffness and damping matrices by reasonably small perturbations from equilibrium. The stability behavior of a typical double suction centrifugal pump is presented. Results show the influence of clearance and flow conditions on running speeds and stability characteristics.

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Assessment of seismic behavior stone bridge using a finite element method and discrete element method

  • Naderi, Melika;Zekavati, Mehdi
    • Earthquakes and Structures
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    • v.14 no.4
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    • pp.297-303
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    • 2018
  • Seismic behavior of Osmanli and Senyuva stone bridges was addressed in this study. A combination of FEM and DEM was employed for getting closer to the real behavior of the bridge. One of the unique features of this combinational method is simulation close to reality. Modal numerical analysis was also used to verify the modeling. At the end of earthquake, a part of two lateral walls of Osmanli bridge was broken. The growth of arch cracks also increased during the earthquake. A part of right-hand wall of Senyuva Bridge was destructed during the earthquake. The left-hand side of the bridge wall was damaged during the earthquake but was not destructed.

Validation of 3D crack propagation in plain concrete -Part II: Computational modeling and predictions of the PCT3D test

  • Gasser, T.Christian
    • Computers and Concrete
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    • v.4 no.1
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    • pp.67-82
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    • 2007
  • The discrete crack-concept is applied to study the 3D propagation of tensile-dominated failure in plain concrete. To this end the Partition of Unity Finite Element Method (PUFEM) is utilized and the strong discontinuity approach is followed. A consistent linearized implementation of the PUFEM is combined with a predictor-corrector algorithm to track the crack path, which leads to a robust numerical description of concrete cracking. The proposed concept is applied to study concrete failure during the PCT3D test and the predicted numerical results are compared to experimental data. The proposed numerical concept provides a clear interface for constitutive models and allows an investigation of their impact on concrete cracking under 3D conditions, which is of significant scientific interests to interpret results from 3D experiments.

Characterization of Groundwater Flow to Horizontal or Slanted Well Using Numerical Modeling (수치 모사를 활용한 수평 혹은 경사형 특수 정호 지하수 흐름 특성 평가)

  • Kim, Hyoung-Soo
    • Journal of Soil and Groundwater Environment
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    • v.13 no.2
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    • pp.54-61
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    • 2008
  • The drawdown distribution due to pumping by horizontal or slanted wells is analyzed by numerical modelling. In the numerical modelling uses 1-D discrete element feature included in commercial groundwater modeling program FEFLOW (version 5.1) and the results are compared with the semi analytic solution which uses superposition of successive point sources proposed by Zhan and Zlotnik (2002). Results of the numerical modeling agree well with the semi analytic solution except for very near field region of sink sources. The drawdown distribution due to pumping in riverbank filtration(RBF) plan site can be evaluated quantitatively by the numerical modeling in this study.

Non-Prismatic Beam Element for Nonlinear Seismic Analysis of Steel Moment Frames I: Element Formulation (강재 모멘트 골조의 비선형 지진 해석을 위한 부등단면 보 요소 I: 요소개발)

  • Hwang, Byoung-Kuk;Jeon, Seong-Min;Kim, Kee-Dong;Ko, Man-Gi
    • Journal of the Korean Society of Hazard Mitigation
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    • v.7 no.5
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    • pp.27-35
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    • 2007
  • This study presents a non -prismatic beam element for modeling the elastic and inelastic behavior of the steel beam, which has the post-Northridge connections in steel moment frames that are subjected to earthquake ground motions. The elastic stiffness matrix for non-prismatic members with reduced beam section (RES) connection is in the closed-form. The plasticity model is of a discrete type and is composed of a series of nonlinear hinges connected by rigid links. The hardening rules can model the inelastic behavior for monotonic and random cyclic loading, and the effects of local buckling. Verification and calibration of the model are presented in a companion paper.

Numerical Analysis of EPB TBM Driving using Coupled DEM-FDM Part I : Modeling (개별요소법과 유한차분법 연계 해석을 이용한 EPB TBM 굴진해석 Part I : 모델링)

  • Choi, Soon-wook;Lee, Hyobum;Choi, Hangseok;Chang, Soo-Ho;Kang, Tae-Ho;Lee, Chulho
    • Tunnel and Underground Space
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    • v.30 no.5
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    • pp.484-495
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    • 2020
  • To numerically simulate the advance of EPB TBM, various type of numerical analysis methods have been adopted including discrete element method (DEM), finite element method (FEM), and finite difference method (FDM). In this paper, an EPB TBM driving model was proposed by using coupled DEM-FDM. In the numerical model, DEM was applied in the TBM excavation area, and contact properties of particles were calibrated by a series of triaxial tests. Since the ground around the excavation area was coupled with FDM, the horizontal stress considering the coefficient of earth pressure at rest could be applied. Also, the number of required particles was reduced and the efficiency of the analysis was increased. The proposed model can control the advance rate and rotational speed of the cutter head and screw conveyor, and derive the torque, thrust force, chamber pressure, and discharging during TBM tunnelling.