• 한국가스학회지
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• 제18권3호
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• pp.67-74
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• 2014

인구가 밀집되어 있는 도심지역에 매설된 천연가스 공급배관은 외부 또는 내부 결함으로 인한 가스의 누출, 확산, 화재, 폭발로 발생되는 재산과 인명피해의 큰 잠재위험을 지니고 있다. 사고를 미연에 방지하기 위해 정량적 평가에 기초한 위험관리를 실시하고 있으며, 매설배관의 정량적 위험성을 평가하기 위해서는 우선적으로 사고피해영향 분석을 통한 화학물질의 누출량 계산, 확산 분석, 화재 및 폭발로 인한 복사열과 압력파 계산이 필요하다. 본 논문에서는 CCPS, TNO에서 제안하는 model 들을 통하여 실제 San Bruno 매설배관 폭발 사고 시나리오를 기반으로 천연가스의 누출량, Fireball의 복사열 계산을 수행하고 결과 값을 실제 피해결과와 비교분석 하였다.

• Geomechanics and Engineering
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• 제20권4호
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• pp.359-370
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• 2020

Prestressed ground anchors are important structural elements in geotechnical engineering. Despite their widespread usage, the design process is often significantly simplified. One of the major drawbacks of commonly used design methods is the assumption that skin friction is mobilized uniformly along an anchor's fixed length, one consequence of which is that a progressive failure phenomenon is neglected. The following paper introduces an alternative design approach - a computer algorithm employing the load-transfer method. The method is modified for the analysis of anchors and combined with a procedure for the derivation of load-transfer functions based on commonly available laboratory tests. The load-transfer function is divided into a pre-failure (hardening) and a post-failure (softening) segment. In this way, an aspect of non-linear stress-strain soil behavior is incorporated into the algorithm. The influence of post-grouting in terms of radial stress update, diameter enlargement, and grout consolidation is included. The axial stiffness of the anchor body is not held constant. Instead, it gradually decreases as a direct consequence of tensile cracks spreading in the grout material. An analysis of the program's operation is performed via a series of parametric studies in which the influence of governing parameters is investigated. Finally, two case studies concerning three investigation anchor load tests are presented.

• Nuclear Engineering and Technology
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• 제41권2호
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• pp.199-214
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• 2009

High burn-up transformation process in low temperature nuclear fuel oxides material was observed in the early sixties in LWR $UO_2$ fuels, but not studied in depth. Increasing progressively the fuel discharge burn-up in PWR power plants, this material transformation was again observed in 1985 and identified as an important process to be accounted for in the fuel simulations due to its expected consequence on fuel heat transfer and therefore on the fission gas release. Fission gas release was one of the major concerns in PWR fuels, mainly during transient or accidents events. The behaviour of such a material in case of rod failure was also an important aspect to analyse. Therefore several national and international programs were launched during the last 25 years to understand the mechanisms leading to the high burn-up structure formation and to evaluate the physical properties of the final material. A large observations database has been acquired, using the more sophisticated techniques available in hot cells. This large database is discussed in this paper, providing basis to build an engineering-model, which is based on phenomenological description data and information accumulated. In addition this paper has the ambition to construct the best logical model to understand restructuring.

• Structural Engineering and Mechanics
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• 제30권2호
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• pp.177-190
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• 2008

Material failure behavior is generally dependent on loading rate. Especially in brittle and quasi-brittle materials, rate dependent material behavior can be significant. Empirical formulations are often used to predict the rate dependency, but such methods depend on extensive experimental works and are limited by practical constraints of physical testing. Numerical simulation can be an effective means for extracting knowledge about rate dependent behavior and for complementing the results obtained by testing. In this paper, the failure behavior of a brittle material under different loading rates is simulated by molecular dynamics analysis. A notched specimen is modeled by sub-million particles with a normalization scheme. Lennard-Jones potential is used to describe the interparticle force. Numerical simulations are performed with six different loading rates in a direct tensile test, where the loading velocity is normalized to the ratio of the pseudo-sonic speed. As a consequence, dynamic features are achieved from the numerical experiments. Remarkable failure characteristics, such as crack surface interaction/crack arrest, branching, and void nucleation, vary in case of the six loading cases. These characteristics are interpreted by the energy concept approach. This study provides insight into the change in dynamic failure mechanism under different loading rates.

• Computers and Concrete
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• 제9권1호
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• pp.21-33
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• 2012

This paper presents the numerical simulation of the rigid 12.6 mm diameter kinetic energy ogive-nosed projectile impact on plain and fiber reinforced concrete (FRC) targets with compressive strengths from 45 to 235 MPa, using a three-dimensional finite element code LS-DYNA. A combined dynamic constitutive model, describing the compressive and tensile damage of concrete, is implemented. A modified Johnson_Holmquist_Cook (MJHC) constitutive relationship and damage model are incorporated to simulate the concrete behavior under compression. A tensile damage model is added to the MJHC model to analyze the dynamic fracture behavior of concrete in tension, due to blast loading. As a consequence, the impact damage in targets made of plain and fiber reinforced concrete with same matrix material under same impact velocities (650 m/s) are obtained. Moreover, the damage distribution of concrete after penetration is procured to compare with the experimental results. Numerical simulations provide a reasonable prediction on concrete damage in both compression and tension.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2001년도 하계학술대회 논문집
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• pp.1026-1029
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• 2001

Zinc films have been deposited onto various buffer layers, Al, Al-Cu, Ag and Ag-Al, by vacuum evaporation method in order to investigate the film microstructure and its consequence on the film growth. Zn films were grown onto Al buffer layers with faster rates than on Ag buffer layers, because of the presence of preferred growth orientation. Especially, in the Zn film formation on the Ag layers, intermetallic compounds AgZn was formed to cause the different growth orientation from Zn film obtained on the Al layers.

• 한국환경과학회지
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• 제18권11호
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• pp.1291-1297
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• 2009

The purpose of this study was to establish structural bone noise analysing method for apartments building floor with Structural-Acoustic coupling analysis. Nowadays, noise through floor is recognized as important problem with the consequence that noise isolation technique is studied in the various fields of industry. From among noise factors, resonance sound is main reason for floor's solid noise. therefore, In this study, evaluation method for composite material slab is established and that a case study is suggested with it.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2005년도 춘계 학술대회논문집
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• pp.159-168
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• 2005

Noise generated by the blunt trailing edge of lifting surfaces is investigated in this study using fluid structure interaction theory. First, through the eddy modeling, noise generation doe to the flow instability on the rigid trailing edge is surveyed. Then the behavior of elastic cantileverd beam is investigated. Parametric study based on various material properties is employed to analyze the motion of the beam. Moreover, each eigenmode approach of cantilevered beam is used to find when flow induced vibration is resonant. To analyze elastic behavior of cantilever beam efficiently, moving grid generation technique based on non-conservative form of Navier-Stokes equation is used. Equation of the motion associated with the cantilever beam is discretized by the Galerkin procedure with forced vibration. As a consequence, behavior of the elastic cantilevered beam is stable when the first mode natural frequency of the material is relatively higher than that of flow induced pressure fluctuation.

• 콘크리트학회지
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• 제20권2호
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• pp.25-36
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• 2008

Seismic design of reinforced concrete flat plate structures is often complicated as it deals with three dimensionality and continuous spans, and mostly material complexity and reinforcement variation. A great degree of uncertainty in such structural and material properties is thus inherent in the RC flat plate systems, and hinders simplification of the design process in terms of slab flexure, unbalanced moment transfer at a slab-column connection, and punching shear. For these reasons, there have been substantial changes and updates in building codes relating to flat plates and slab-column connections over a handful of decades. Also, for the same reason, some of codes never have been revised. As a consequence of nonsimultaneous development of each provision, it tends to confuse structural engineers when using a mixture of all different US code provisions. In this paper, in the step-by-step logical order, seismic design of the RC flat plate systems is re-organized and clarified to make it easier to apply. Furthermore, recent changes or proposed changes are introduced, and are explained as to how it will apply in practice.

• 한국가스학회지
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• 제18권4호
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• pp.76-85
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• 2014

본 연구는 독성가스 사고의 주요 원인의 하나인 부식에 대해 고압 독성가스시설을 대상으로 필요한 안전기술을 정립하기 위하여 미국석유학회에서 개발한 API-581 절차를 채택하여 사고결과 분석방법에 대한 적용성을 검토하고, 이를 바탕으로 사고결과 분석방법을 제시하였다. 고압 독성가스시설에서 API-581의 8단계 사고결과 분석절차에 따라 단계별 적용성을 검토한 결과, 고압 독성가스시설에 적용할 사고결과 분석방법은 총 6단계로 단순화 할 수 있었다. 즉, Step 1(대표물질 결정), Step 5(누출유형 결정), Step 6(유체상 결정)과 Step 8(사고 피해영역 산출)은 적용하지 않고, Step 3(누출량 산출)은 inventory group 개념만 적용하며, Step 4(누출속도 산출)는 기체 누출속도만을 적용하고, Step 2(누출공 크기 선정)와 Step 7(완화시스템 등급 결정)은 전부 적용한다. 이때, Step 5와 Step 8은 일반적으로 적용이 가능한 CCPS 방법을 대안적인 방법으로 채택한다.