• 한국철도학회:학술대회논문집
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• 한국철도학회 2005년도 추계학술대회 논문집
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• pp.878-883
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• 2005

Sleeper, the ballast, and ballast mat in the high-speed railroad line are modelled using a two-dimensional discrete element method to generate circle and line elements. Stress transfer mechanism from the sleeper to the subgrade via the ballast is analyzed. The behavior of ballast bed of the high-speed railroad line is also accessed with the model.

• 한국자원리싸이클링학회:학술대회논문집
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• 한국자원리싸이클링학회 2006년도 춘계임시총회 및 제27회 학술발표대회
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• pp.168-172
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• 2006

• 한국지반신소재학회논문집
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• 제10권2호
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• pp.55-66
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• 2011

본 논문에서는 Back-to-Back(BTB) 보강토 옹벽의 파괴메커니즘에 관한 연구내용을 다루었다. 이를 위해 모형실험과 불연속체 해석(Discrete Element Method, DEM)을 도입한 수치해석을 수행하였다. 먼저 축소모형실험에서는 일반적으로 시공되는 Back-to-Back 보강토 옹벽을 1/10로 축소하여 1-g 모델을 구축한 후 자중만으로 파괴에 도달하도록 하였으며 보강재의 길이변화에 따른 파괴 메커니즘을 고찰하였다. 아울러 모형실험 결과를 토대로 검증된 DEM 해석모델을 이용하여 다양한 시공조건에 대한 해석을 수행하여 BTB 옹벽의 폭 및 보강재 길이에 따른 파괴 메커니즘을 고찰하고 그 결과를 현재 적용되는 FHWA 설계기준과 비교하였다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1999년도 봄 학술발표회 논문집(I)
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• pp.233-238
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• 1999

Localized failure analysis of concrete structures can be carried out effectively by modeling fracture process zone of concrete during crack initiation and propagation. But, the analysis techniques are still insufficient for crack modeling because of difficulties in numerical analysis procedure which describe progressive crack. In this paper, a finite element with embedded displacement discontinuity is introduced to remove the difficulties of remeshing for crack propagation in discrete crack model during progressive failure analysis of concrete structures. The performance of this so-called embedded crack approach for concrete failure analysis is verified by several analysis examples. The analysis results show that the embedded crack approach retains mesh size objectivity and can simulate localized failure under mixed mode loading. It can be concluded that the embedded crack approach cab be an effective alternate to the smeared and discrete crack approaches.

• Earthquakes and Structures
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• 제21권5호
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• pp.531-549
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• 2021

Analytical models were developed and seismic behaviors were analyzed for a three-story stone pagoda at the Cheollyongsa temple site, which was damaged by the Gyeongju earthquake of 2016. Both finite and discrete element modeling were used and the analysis results were compared to the actual earthquake damage. Vulnerable parts of stone pagoda structure were identified and their seismic behaviors via sliding, rocking, and risk analyses were verified. In finite and discrete element analyses, the 3F main body stone was displaced uniaxially by 60 and 80 mm, respectively, similar to the actual displacement of 90 mm resulting from the earthquake. Considering various input conditions such as uniaxial excitation and soil-structure interaction, as well as seismic components and the distance from the epicenter, both models yielded reasonable and applicable results. The Gyeongju earthquake exhibited extreme short-period characteristics; thus, short-period structures such as stone pagodas were seriously damaged. In addition, we found that sliding occurred in the upper parts because the vertical load was low, but rocking predominated in the lower parts because most structural members were slender. The third-floor main body and roof stones were particularly vulnerable because some damage occurred when the sliding and rocking limits were exceeded. Risk analysis revealed that the probability of collapse was minimal at 0.1 g, but exceeded 80% at above 0.3 g. The collapse risks at an earthquake peak ground acceleration of 0.154 g at the immediate occupancy, life safety, and collapse prevention levels were 90%, 52%, and 6% respectively. When the actual damage was compared with the risk analysis, the stone pagoda retained earthquake-resistant performance at the life safety level.

• Computers and Concrete
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• 제5권4호
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• pp.329-342
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• 2008

A local behavior law, which includes elasticity, plasticity and damage, is developed in a three dimensional numerical model for concrete. The model is based on the Discrete Element Method (DEM)and the computational implementation has been carried out in the numerical Code YADE. This model was used to study the response of a concrete slab impacted by a rigid missile, and focuses on the extension of the compacted zone. To do so, the model was first used to simulate compression and hydrostatic tests. Once the local constitutive law parameters of the discrete element model were calibrated, the numerical model simulated the impact of a rigid missile used as a reference case to be compared to an experimental data set. From this reference case, simulations were carried out to show the importance of compaction during an impact and how it expands depending on the different impact conditions. Moreover, the numerical results were compared to empirical predictive formulae for penetration and perforation cases, demonstrating the importance of taking into account the local compaction process in the local interaction law between discrete elements.

• 소음진동
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• 제10권3호
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• pp.523-530
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• 2000

In this paper we present an efficient method for finite element vibration analysis of a structure with cyclic symmetry and applied it to calculating the natural vibration characteristics for a blower impeller. Blower impeller having a cyclically symmetric structure is composed of circumferentially repeated substructures., The whole-structure is partitioned into substructures and then finite element vibration analysis is performed for a substructure using transformed equations for each number of nodal diameter which are derived from discrete Fourier transform in consideration of the cyclic symmetry. natural vibration characteristics for three kinds of models which are blower impeller without support ring with small support ring and with large support ring are numerically analyzed and compared. Accuracy and efficiency of the present method are verified by comparison of results of the analysis with substructure and with whole-structure. Also the results of the analysis by cyclic symmetry module(SOL 115) of MSC/NASTRAN are presented and compared.

• 소성∙가공
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• 제9권3호
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• pp.274-283
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• 2000

A dynamic explicit finite element code for simulating sheet forming processes has been developed. The code utilizes the discrete Kirchhoff shell element and contact force is treated by a conventional penalty method. In order to reduce the computational cost, a new and robust contact searching algorithm has been developed and implemented into the code. In the method, a hierarchical structure of tool segments is built for each tool at the initial stage of the analysis. hierarchical structure is built in a way to divide a box to 8 sub-boxes, 2 in each direction, until the lowest level of the hierarchical structure contains exactly one segment of the tool or empty. Then at each time step, contact is checked from the box to sub-boxes hierarchically for each node. Comparisons of computational results of various examples with the existing ones show the validity of the method.

• 한국지반공학회논문집
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• 제21권4호
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• pp.115-122
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• 2005

본 연구에서는 토사사면의 안전율을 산정하고 최소임계단면을 탐색하기 위하여 개별요소법과 유전자 알고리즘으로 조합된 새로운 해석방법이 제안되었다. 안전율 산정시, 한계평형법에 근거한 통상적인 사면안정 해석법들은 전체적인 힘평형을 만족하지 못하기 때문에 절편간에 작용하는 힘의 경사와 위치에 대한 가정이 불가피하다. 개별요소법에 근거하여 개발된 사면안정해석법은 힘과 변위간의 적합조건을 만족할 수 있다. 또한 제안된 해석기법에서는 최소임계 단면을 탐색하기 위하여 실수형 유전자 알고리즘이 적용되었다. 이 방법은 지역해에 쉽게 수렴하는 간편한 최적화기 법보다 안정적으로 전역해를 탐색할 수 있다 제안된 해석기법의 적용성을 검토하기 위하여 예제해석이 수행되었다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1998년도 가을 학술발표논문집(II)
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• pp.450-455
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• 1998

In this paper, finite element with embedded discontinuous line is introduced in order to avoid the difficulties of adding new nodal points along with crack growth in discrete crack model. With the discontinuous element using discontinuous shape function, stiffness matrix of finite element is derived and dual mapping technique for numerical integration is employed. Using the finite element program made with employed algorithms, algorithm is verified and fracture analysis of simple concrete beam is performed.