• Title/Summary/Keyword: Discrete element analysis

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Differential cubature method for buckling analysis of arbitrary quadrilateral thick plates

  • Wu, Lanhe;Feng, Wenjie
    • Structural Engineering and Mechanics
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    • v.16 no.3
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    • pp.259-274
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    • 2003
  • In this paper, a novel numerical solution technique, the differential cubature method is employed to study the buckling problems of thick plates with arbitrary quadrilateral planforms and non-uniform boundary constraints based on the first order shear deformation theory. By using this method, the governing differential equations at each discrete point are transformed into sets of linear homogeneous algebraic equations. Boundary conditions are implemented through discrete grid points by constraining displacements, bending moments and rotations of the plate. Detailed formulation and implementation of this method are presented. The buckling parameters are calculated through solving a standard eigenvalue problem by subspace iterative method. Convergence and comparison studies are carried out to verify the reliability and accuracy of the numerical solutions. The applicability, efficiency, and simplicity of the present method are demonstrated through solving several sample plate buckling problems with various mixed boundary constraints. It is shown that the differential cubature method yields comparable numerical solutions with 2.77-times less degrees of freedom than the differential quadrature element method and 2-times less degrees of freedom than the energy method. Due to the lack of published solutions for buckling of thick rectangular plates with mixed edge conditions, the present solutions may serve as benchmark values for further studies in the future.

Vibration Analysis of Trapezoidal Corrugated Plates with Stiffeners and Lumped Masses (집중질량을 고려한 보강된 사다리꼴 주름판의 진동해석)

  • Jung, Kang;Kim, Young-Wann
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.24 no.5
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    • pp.414-420
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    • 2014
  • In this paper, the vibration characteristics of the trapezoidal corrugated plate with axial stiffeners and lumped masses are investigated by the analytical method. The corrugated plate can be treated as an equivalent orthotropic plate as this plate has different flexure properties in two perpendicular directions; flexible in the corrugation direction and stiff in the transverse direction. The effective extensional and flexural stiffness of the equivalent plate are considered to obtain the precise solution in the analysis. The plate is stiffened by concentric stiffeners horizontally to the corrugation direction. The discrete stiffener theory is adopted to consider the position of stiffener. To demonstrate the validity of the proposed approach, the comparison is made with the results of 3D ANSYS finite element solutions. Some numerical results are presented to check the effect of the geometric properties.

Assessment of steel components and reinforced concrete structures under steam explosion conditions

  • Kim, Seung Hyun;Chang, Yoon-Suk;Cho, Yong-Jin
    • Structural Engineering and Mechanics
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    • v.60 no.2
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    • pp.337-350
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    • 2016
  • Even though extensive researches have been performed for steam explosion due to their complex mechanisms and inherent uncertainties, establishment of severe accident management guidelines and strategies is one of state-of-the arts in nuclear industry. The goal of this research is primarily to examine effects of vessel failure modes and locations on nuclear facilities under typical steam explosion conditions. Both discrete and integrated models were employed from the viewpoint of structural integrity assessment of steel components and evaluation of the cracking and crushing in reinforced concrete structures. Thereafter, comparison of systematic analysis results was performed; despite the vessel failure modes were dominant, resulting maximum stresses at the all steel components were sufficiently lower than the corresponding yield strengths. Two failure criteria for the reinforced concrete structures such as the limiting failure ratio of concrete and the limiting strains for rebar and liner plate were satisfied under steam explosion conditions. Moreover, stresses of steel components and reinforced concrete structures were reduced with maximum difference of 12% when the integrated model was adopted comparing to those of discrete models.

The Rearch of Stress Route for Concrete Structure using Advanced Progressive Optimization (개선된 점진적 구조 최적화 기법을 이용한 콘크리트 구조물의 응력경로 탐색)

  • Kim, Shi-Hwan;Yoon, Seong-Soo;Park, Jin-Seon;Jeon, Jeong-Bae
    • Journal of The Korean Society of Agricultural Engineers
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    • v.53 no.6
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    • pp.153-163
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    • 2011
  • This research describe improved algorithm that is able to decide terminal criterion of Evolutionary Structural Optimization (ESO), reducing load of calculation to search load path of concrete beam, and apply to agricultural facilities. The ESO method is that make to discrete structure, structural analyze each element stress through FEM. And repeat generation with next material condition to become for most suitable composing. Individual element introduces concept of zero stiffness, but zero stiffness decisions are gone to direction of exclusion. In this stduy, improve algorithm to be convergence by 'Rule of Alive or Die' in arrival because is most suitable. Also, existing terminal criterion lack consistency because that used depend on experience of researcher. This research procedure is fellowed. First, all modulus of elasticity assume a half of elasticity modulus of material, Second, structural analysis by FEM, Third, apply to the remove ratio and restoration ratio for the 'rule of alive or die'. Forth, reconstruct the element and material conditions. And repeat the first to forth process. The terminal time of evolutional procedure is the all elastic modulus of element changed to blank value or elasticity modulus value of original. Therefore, in this study, consist the algorithm for programming, and apply to the agricultural facilities with concrete.

Numerical Analysis on Morphologic Characteristics of Rock Slope for Reducing Rockfall Risk (낙석의 위험성 경감을 위한 사면의 외적조건 특성에 관한 수치해석적 연구)

  • Ji, Hyun-Woo;Choi, Sung-O.
    • Tunnel and Underground Space
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    • v.20 no.1
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    • pp.15-27
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    • 2010
  • Geo-hazard shows a rapid increasing tendency with establishment of frequent great slopes in various construction sites, especially in the unfavorable topographic condition in which about 70% of the surface is covered by the mountainous area. An repeatedly taking place on the heavy rain season is accompanied by a large scale of rockfall, and causes great damage to an individual as well as a property. Even though lots of field studies and fundamental studies have been performed to reduce this hazard, however, an essential study on the mechanism of the rockfall should be limited to the conventional studies on the slope reinforcement and/or the rockfall risk analysis. In this study, the mechanism of rockfall depending on the morphologic characteristics of slope has been simulated numerically with the PFC2D, one of the discrete element programs. For analyzing its mechanism, the input parameters relating to the slope such as surface condition, gradient, number of benches, bench gradient, and the ratio of bench width to rockfall size were taken into consideration.

The effect of formation of spherical underground cavity on ground surface settlement : Numerical analysis using 3D DEM (구형지하공동 형성이 지표침하에 미치는 영향에 대한 3차원 개별요소해석)

  • Lee, Sang-Hyun;Lee, Hang-Lo;Song, Ki-Il
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.18 no.2
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    • pp.129-142
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    • 2016
  • The underground cavity known as one of the reasons of ground surface settlement is a discontinuous character. Therefore, it is limited to analyze with continuum analysis. In this research, The spherical underground cavity affecting the ground surface settlement is studied with Discrete Element Method. Ground properties, depth and diameter of the spherical underground cavity are chosen as factors of the spherical underground cavity and the effect of the each factor variations on the ground surface settlement is analyzed. Relative depth to the diameter of the spherical underground cavity is also studied. The result of the research suggests the basis of underground cavity collapse prediction and standard of support.

Particle Morphology Change and Different Experimental Condition Analysis during Composites Fabrication Process by Conventional Ball Mill with Discrete Element Method(DEM) Simulation (전동볼밀을 이용한 금속기반 복합재 제조공정에서 분쇄매체차이에 대한 입자형상변화와 DEM 시뮬레이션 해석)

  • Ichinkhorloo, Batchuluun;Bor, Amgalan;Uyanga, Batjargal;Lee, Jehyun;Choi, Heekyu
    • Korean Journal of Materials Research
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    • v.26 no.11
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    • pp.611-622
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    • 2016
  • Particle morphology change and different experimental condition analysis during composite fabrication process by traditional ball milling with discrete element method (DEM) simulation were investigated. A simulation of the three dimensional motion of balls in a traditional ball mill for research on the grinding mechanism was carried out by DEM simulation. We studied the motion of the balls, the ball behavior energy and velocity; the forces acting on the balls were calculated using traditional ball milling as simulated by DEM. The effect of the operational variables such as the rotational speed, ball material and size on the flow velocity, collision force and total impact energy were analyzed. The results showed that increased rotation speed with interaction impact energy between balls and balls, balls and pots and walls and balls. The rotation speed increases with an increase of the impact energy. Experiments were conducted to quantify the grinding performance under the same conditions. Furthermore, the results showed that ball motion affects the particle morphology, which changed from irregular type to plate type with increasing rotation speed. The evolution was also found to depend on the impact energy increase of the grinding media. These findings are useful to understand and optimize the particle motion and grinding behavior of traditional ball mills.

Seismic Response Analysis of a Floating Bridge with Discrete Pontoons (이산폰툰형 부유식교량의 지진응답해석)

  • Kwon, Jang-Sup
    • Journal of the Earthquake Engineering Society of Korea
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    • v.9 no.2 s.42
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    • pp.47-58
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    • 2005
  • Dynamic response analysis in time dimain is conducted for floating bridges with discrete pontoons subject to spatial variation of ground motions. The Spatial variation of ground motions is considered with the coherency function model which represents wave passage, incoherence and local site effects. The superstructure of the bridge is represented by space frame and elastic catenary cable elements, the abutment us modelde with the spring element of FHWA guideline for considering soil structure interaction and the concept of retardation function is utilized to consider the frequency dependency of the hydrodynamic coefficients which are obtainde by boundary element method. multiple support excitations considering the spatial variation. The noticeable amplification of the response can be shown when the spatial variation of ground motions is incorporated in the anallysis of floating bridges.

Numerical Study on Medium-Diameter EPB Shield TBM by Discrete Element Method (개별요소법을 이용한 중단면 토압식 쉴드TBM의 수치해석 연구)

  • Choi, Soon-Wook;Park, Byungkwan;Kang, Tae-Ho;Chang, Soo-Ho;Lee, Chulho
    • Journal of the Korean Geosynthetics Society
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    • v.17 no.4
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    • pp.129-139
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    • 2018
  • The Discrete Element Method (DEM) has been widely used in granular material researches. Especially, if material has a large deformation, such as ground, it can be a useful method to analyze. In this study, to simulate ground formations, DEM was used. The main purpose of DEM analysis was to investigate the numerical model which can predict the TBM performance by simulating excavating procedure. The selected EPB TBM has a 7.73 m of diameter and six spokes. And two pre-defined excavation conditions with the different rotation speeds per minute (RPM) of the cutterhead was applied. In the modeled cutterhead, the open ratio of cutterhead was 21.31% and number of cutters (including disc cutter and cutter bit) was 219. From the results, reaction forces and resistant torques at the cutterhead face and cutting tools, were measured and compared. Additionally the muck discharge rate and accumulated muck discharge by the screw auger were evaluated.

Reinforcement layout design for deep beam based on BESO of multi-level reinforcement diameter under discrete model

  • Zhang, Hu-zhi;Luo, Peng;Yuan, Jian;Huang, Yao-sen;Liu, Jia-dong
    • Structural Engineering and Mechanics
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    • v.84 no.4
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    • pp.547-560
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    • 2022
  • By presetting various reinforcement diameters in topology optimization with the discrete model finite element analysis, an algorithm of bidirectional evolutionary structural optimization of multi-level reinforcement diameter is presented to obtain the optimal reinforcement topologies which describe the degree of stress of different parts. The results of a comparative study on different reinforcement feasible domain demonstrate that the more angle types of reinforcement are arranged in the initial domain, the higher utilization rate of reinforcement of the optimal topology becomes. According to the nonlinear finite element analysis of some deep beam examples, the ones designed with the optimization results have a certain advantage in ultimate bearing capacity, although their failure modes are greatly affected by the reinforcement feasible domain. Furthermore, the bearing capacity can be improved when constructional reinforcements are added in the subsequent design. However the adding would change the relative magnitude of the bearing capacity between the normal and inclined section, or the relative magnitude between the flexural and shear capacity within the inclined section, which affects the failure modes of components. Meanwhile, the adding would reduce the deformation capacity of the components as well. It is suggested that the inclined reinforcement and the constructional reinforcement should be added properly to ensure a desired ductile failure mode for components.