• Earthquakes and Structures
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• 제14권4호
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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.

• 한국도로학회논문집
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• 제15권5호
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• pp.21-29
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• 2013

PURPOSES: Simulation of aggregate slump test using equivalent sphere particle in DEM and its validity evaluation against lab aggregate slump test METHODS : In this research, aggregate slump tests are performed and compared with DEM simulation. To utilize spheric particles in YADE, equivalent sphere diameter concept is applied. As verification measures, the volume in slump cone filled with aggregate is used and it is compared with volume in slump cone filled with equivalent sphere particle. Slump height and diameter are also used to evaluate the suggested numerical method with equivalent concept RESULTS : Simulation test results show good agrement with lab test results in terms of loose packing volume, height and diameter of slumped particle clump. CONCLUSIONS : It is concluded that numerical simulation using DEM is applicable to evaluate the effect of aggregate morphological property in loose packing and optimum gradation determination based on the aggregate slump test simulation result.

• Geomechanics and Engineering
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• 제35권5호
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• pp.475-486
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• 2023

Ballast particles have an irregular shape and are discrete in nature. Due to the discrete nature of ballast, it exhibits complex mechanical behaviour under loading conditions. The discrete element method (DEM) can model the behaviour of discrete particles under a multitude of loading conditions. DEM is used in this paper to simulate a series of three-dimensional direct shear tests in order to investigate the shear behaviour of railway ballast and its interaction at the microscopic level. Particle flow code in three dimension (PFC3D) models the irregular shape of ballast particles as clump particles. To investigate the influence of particle size distribution (PSD), real PSD of Indian railway ballast specification IRS:GE:1:2004, China high-speed rail (HSR) and French rail specifications are generated. PFC3D built-in linear contact model is used to simulate the interaction of ballast particles under various normal stresses, shearing rate and shear box sizes. The results indicate how shear resistance and volumetric changes in ballast assembly are affected by normal stress, shearing rate, PSD and shear box size. In addition to macroscopic behaviour, DEM represents the microscopic behaviour of ballast particles in the form of particle displacement at different stages of the shearing process.

• Computers and Concrete
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• 제21권2호
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• pp.189-197
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• 2018

A discrete element approach is used to investigate the effects of confining stress on the shear behaviour of joint's bridge area. A punch-through shear test is used to model the concrete cracks under different shear and confining stresses. Assuming a plane strain condition, special rectangular models are prepared with dimension of $75mm{\times}100mm$. Within the specimen model and near its four corners, four equally spaced vertical notches of the same depths are provided so that the central portion of the model remains intact. The lengths of notches are 35 mm. and these models are sequentially subjected to different confining pressures ranging from 2.5 to 15 MPa. The axial load is applied to the punch through the central portion of the model. This testing and models show that the failure process is mostly governed by the confining pressure. The shear strengths of the specimens are related to the fracture pattern and failure mechanism of the discontinuities. The shear behaviour of discontinuities is related to the number of induced shear bands which are increased by increasing the confining pressure while the cracks propagation lengths are decreased. The failure stress and the crack initiation stress both are increased due to confining pressure increase. As a whole, the mechanisms of brittle shear failure changes to that of the progressive failure by increasing the confining pressure.

• 한국지반신소재학회논문집
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• 제16권2호
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• pp.11-21
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• 2017

지반함몰의 발생은 하수관 파손으로 인한 토사유실이 주원인으로써 그 대책을 수립하기 위해서는 공동과 이완영역의 발생, 주변 지반의 거동을 이해하여야 할 필요성이 있다. 본 논문에서는 지중 하수관의 파손으로 인한 지반함몰 메커니즘 분석을 위해 실내모형실험과 개별요소 수치해석을 실시하였다. 실내모형실험에서는 알루미늄 봉과 트랩도어를 이용하여 모형지반의 거동을 모사하였고, 개별요소 수치해석은 모형실험과 동일한 경계조건으로 수행하여 그 결과를 모형실험 결과와 비교분석하였다. 모형실험 및 개별요소 결과로부터 토사유실로 인한 공동과 이완영역의 형상 및 규모를 파악하였으며, 공동 주변 지반의 간극비 분포 특성 및 이완정도를 파악할 수 있었다.

• 드라이브 ㆍ 컨트롤
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• 제21권2호
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• pp.44-52
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• 2024

In this study, we predicted PTO power requirements based on torque predicted by the discrete element method and the multi-body dynamics coupling method. Six different scenarios were simulated to predict PTO power requirements in different soil conditions. The first scenario was a tillage operation on cohesionless soil, and the field was modeled using the Hertz-Mindlin contact model. In the second through sixth scenarios, tillage operations were performed on viscous soils, and the field was represented by the Hertz-Mindlin + JKR model for cohesion. To check the influence of surface energy, a parameter to reproduce cohesion, on the power requirement, a simple regression analysis was performed. The significance and appropriateness of the regression model were checked and found to be acceptable. The study findings are expected to be used in design optimization studies of agricultural machinery by predicting power requirements using the discrete element method and the multi-body dynamics coupling method and analyzing the effect of soil cohesion on the power requirement.

• 대한토목학회논문집
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• 제30권4A호
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• pp.353-359
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• 2010

시멘트계 기질을 사용하는 복합재료는 재료 양생 과정에서 발생하는 건조수축 균열에 취약하다. 본 연구에서는 파이버 보강 콘크리트의 건조수축에 의한 파괴 거동을 시뮬레이션 하고, 파이버의 조건이 균열 특성에 미치는 영향에 대해 분석한다. 수치 해석 모델은 무작위 격자 형태의 기하학적 구조를 공유하는 관로 요소와 rigid-body-spring 요소로 구성되는데, 각 요소가 담당하는 비역학적-역학적 거동의 커플링에 의해 건조수축이 표현된다. 파이버 보강을 모델링하기 위해 rigid-bodyspring network 내부의 semi-discrete 파이버 요소를 적용하였다. KS F 2424 자유 건조수축 실험을 해석하고 시간에 따른 건조수축 변형률 변화를 비교함으로써 재료의 건조수축 관련 계수들을 산정한다. 다음으로 여러 파이버 혼입률에 대해 KS F 2595 구속 건조수축 실험을 시뮬레이션 하고 균열 발생 일자를 선행 실험 결과와 비교하여 해석 모델의 타당성을 검증한다. 또한, 파이버의 길이와 표면 형태를 변화시켜 건조수축 균열 해석을 수행하고 최대 균열 폭을 측정하여 시뮬레이션에서 나타나는 균열 제어 효과를 판단한다.

• Structural Engineering and Mechanics
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• 제66권3호
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• pp.343-351
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• 2018

Brazilian disc test is one of the most widely used experiments in the literature of geo-mechanics. In this work, the pre-holed concrete Brazilian disc specimens are numerically modelled by a two-dimensional discrete element approach. The cracks initiations, propagations and coalescences in the numerically simulated Brazilian discs (each containing a single cylindrical hole and or multiple holes) are studied. The pre-holed Brazilian discs are numerically tested under Brazilian test conditions. The single-holed Brazilian discs with different ratios of the diameter of the holes to that of the disc radius are modelled first. The breakage load in the ring type disc specimens containing an internal hole with varying diameters is measured and the crack propagation mechanism around the wall of the ring is investigated. The crack propagation and coalescence mechanisms are also studied for the case of multi-holes' concrete Brazilian discs. The numerical and experimental results show that the breaking mechanism of the pre-holed disc specimens is mainly due to the initiation of the radially induced tensile cracks which are growth from the surface of the central hole. Radially cracks propagated toward the direction of diametrical loading. It has been observed that for the case of disc specimens with multiple holes under diametrical compressive loading, the breaking process of the modelled specimens may occur due to the simultaneous cracks propagation and cracks coalescence phenomena. These results also show that as the hole diameter and the number of the holes increases both the failure stress and the crack initiation stress decreases. The experimental results already exist in the literature are quit agree with the proposed numerical simulation results which validates this simulation procedure.

• 드라이브 ㆍ 컨트롤
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• 제20권4호
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• pp.115-122
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• 2023

This study utilized a discrete element method (DEM) simulation, as one of the virtual field trials, to predict the impact of tillage depth on the rotary blade shaft during rotavator tilling. The virtual field for the simulation was generated according to soil properties observed in an actual field. Following the generation of particles for the virtual field, a sequence of calibration steps followed to align the mechanical properties more closely with those of real soil. Calibration was conducted with a focus on bulk density and shear torque, resulting in calibration errors of just 0.02% for bulk density and 0.52% for shear torque. The prediction of the load on a rotary tiller's blade shaft involved a three-pronged approach, considering shaft torque, draft force, and vertical force. In terms of shaft torque, the values exhibited significant increases of 42.34% and 36.91% for every 5-centimeter increment in tillage depth. Similarly, the vertical force saw substantial growth by 40.41% and 36.08% for every 5-centimeter increment. In contrast, the variation in draft force based on tillage depth was comparatively lower at 18.49% and 0.96%, indicating that the effect of tillage depth on draft force was less pronounced than its impact on shaft torque and vertical force. From a perspective of agricultural machinery research, this study provides valuable insights into the DEM soil modeling process, accounting for changes in soil properties with varying tillage depths. These findings are expected to be instrumental in future agricultural machinery design studies.

• 한국분말재료학회지
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• 제7권4호
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• pp.189-196
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• 2000

Effect of ball filling ratio on the behavior of balls motion and their collision characteristic in a tumbler-ball milling of metal powder are investigated by a computer simulation. The discrete element method and the extended Kelvin model composed of nonlinear spring and nonlinear dashpot were employed in the simulation. It can be possible that analysis of the individual balls motion in a three-dimensional actual mill by the two-dimensional model simulation, since the simulated trajectories of ball paths are in relatively good agreement with the actual ones. It knows that the balls motion in the tumbler-ball mill is strongly influenced by the surface conditions of the balls and mill container wall. The energy consumption of the individual balls during impact and the impact frequency of the individual balls increased with an increase in the ball filling ratio and showed maximum values at about 50-60% ball filling ratio, and then decreased.