• Journal of the Korea Society for Simulation
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• v.29 no.2
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• pp.119-127
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• 2020

This study numerically investigated a structural behavior subjected to consecutive explosions. To this end, a small scale one-way reinforced slab (RC) with fixed-fixed boundary condition was considered as the target structure, and a commercial software, LS-DYNA, was utilized for finite element (FE) analysis. Prior to performing FE analysis, preliminary tests were carried out to verification of a computational model for the one-way RC slab. In the numerical simulation, identical blast loads were consecutively applied to the structure, and cumulative damage assessment were carried out based on its maximum dynamic displacements. As a result of the numerical simulation, it was found that maximum displacements considering permanent deformation due to a prior explosion were almost linearly increased in every explosion until the hazardous damage threshold.

• Journal of the Korea Concrete Institute
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• v.26 no.3
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• pp.335-342
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• 2014

In this paper, reference erosion criteria value suitable for progressive collapse analysis of RC structure due to blast load is proposed. Erosion is fundamentally a numerical technique to overcome the problems such as large numerical errors or abrupt termination of analysis and previous study has been suggested value for blast analysis. But concrete has different stress-strain curve according to strain rate. Consequently, the erosion criteria for the realistic progressive collapse simulation were suggested by comparing experiment results and numerical analysis results. Finally, the real progressive collapse of Oklahoma Federal Building was analyzed by using the median value of two values. And as a result, the analysis result is the actual collapse of the well described.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2011.04a
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• pp.148-151
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• 2011

현재 방폭설계 관련 설계지침은 기둥제거시나리오를 이용한 대체하중경로법을 주로 적용하고 있지만, 실제로 폭발이 발생하였을 때 기둥의 완전한 파괴가 일어나지 않을 경우 이 방식을 적용하는 것은 적합하지 않다. 따라서 본 논문에서는 비선형 동적 해석 프로그램인 AUTODYN을 이용해 편심하중을 받는 철근 콘크리트 기둥의 잔존 폭발 저항 성능을 평가하는 방식을 제안하였다. 해석결과를 비교해보면 TNT양과 축하중이 클수록 철근콘크리트 기둥의 잔존 폭발 저항 성능이 감소되었다. 이것은 폭발이 발생하기전의 기둥의 편심하중에 의한 응력상태에 따라 폭발 저항 성능이 달라짐을 알 수 있다.

• Journal of Korean Society of Steel Construction
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• v.28 no.4
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• pp.271-280
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• 2016

The need to accurate quantification of blast pressure loading in the near field is important because the focus of security design of critical infrastructure, buildings and bridges is for near-field detonations. Incident and reflected pressures for near-field detonations are very difficult to be measured by commercially available pressure transducers due to the high pressure and temperature, which requires a verified and validated computational fluid dynamics code to reasonably predict the near-field pressures and impulses. This paper presents numerical studies to verify and validate a CFD code for calculations of incident and reflected overpressures and impulses. The near field is emphasized and recommendations for mesh sizes to optimally simulate the near-field detonation are provided.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.37 no.1
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• pp.1-7
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• 2017

In general, the large loads which are applied from explosion, impact, earthquake and wind at a short time caused the materials of structures to large deformations, rotations and strains locally. If such phenomena will be analyzed, hydrocodes which can be considered fluid-structure interaction under computational continuum mechanics are inevitably needed. Also, the explosion mechanism is so complicated, it is reasonable that the behaviors of structure are predicted through explosion analyses and experiment at the same time. But, unfortunately, it is true that explosion experiments are limited to huge cost, large experiment facilities and safety problems. Therefore, in this study, it is shown that the results of explosion analyses using the AUTODYN are agreed with those of existing explosion experiments for reinforced concrete slabs within reasonable error limits. And the explosion damage of the same reinforced concrete slab are assessed for quite different reinforcement arrangement spacings, concrete cover depths, and vertical reinforcements. From the explosion analyses, it is known that the more the ratio of slab thickness to reinforcement arrangement spacing is increased, and small-diameter reinforcements are used than large-diameter reinforcements on the same reinforcement ratio, and vertical reinforcements are used, the more the anti-knock capacities are improved.

• Computational Structural Engineering
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• v.10 no.3
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• pp.22-29
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• 1997

본 논문에서는 균열이 존재하는 구조부재에 충격이나 폭발하중이 가해진 경우 동적응력확대계수를 구하는 방법들은 논의하고 특히 코오스틱 실험법 및 수치적으로 코오스틱 곡선을 구하여 동적응력확대계수를 구하는 과정을 자세히 설명하였다. 폭발 및 충격에 의한 구조물의 파괴해석은 이와 같은 하중을 받는 압력용기, 빌딩, 초고속선, 해군 함정 등의 파괴강도설계 및 안전성 평가에 핵심기술로 대두되고 있으며 또한 우주항공산업, 고속전철, 암반역학 등의 여러 분야에서 중요한 의미를 갖는다. 따라서 앞으로도 균열진전 및 정지조건, 탄소성 동적파괴해석 및 재료의 충격거동 등에 대한 연구들이 계속되어져야 할 것으로 사료된다.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.25 no.3
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• pp.219-226
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• 2012

Columns are the key elements supporting load in structure. Column failure causes the structure to collapse. It is important to evaluate residual strength for damaged columns under blast load for preventing progressive collapse. In this paper, columns were investigated to compare the blast resistance on the change of the number of steel bars within the range of reinforcement ratio. And this study was carried out 4 different analytical models to evaluate effects of aspect ratio. The results indicate that the vertical strain was unaffected by the number of steel bars and aspect ratio. As the number of steel bars facing blast load increase, the blast resisting capacity of the columns was improved in the lateral strain. Also, the analysis results showed that a large moment of inertia of area, as compared to a small one would be superior in residual strength as well as force of restitution.

• Journal of the Korean Society for Marine Environment & Energy
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• v.10 no.4
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• pp.218-226
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• 2007

In modern naval ships, the design of submarines has continually evolved to improve survivability and it is also important to design ship against shock response. Exiting underwater ship design has been peformed due to results of static analysis considering shock acceleration by simple method. However, it can not be anticipated good assesment. The present study applied the Arbitrary Lagrangian-Eulerian (ALE) technique, a fluid-structure interaction approach, to simulate an underwater explosion and investigate the survival capability of a damaged submarine liquefied oxygen tank. The Lagrangian-Eulerian coupling algorithm and the equations of state for explosives and seawater were also reviewed. It is shown that underwater explosion analysis using the ALE technique can accurately evaluate structural damage after attack. This procedure could be applied quantitatively to real structural design.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.35 no.6
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• pp.333-342
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• 2022

The blast analysis method entails the use of an empirical equation and application of the pressure-time history curve as an explosive load. Although this method is efficient owing to its simple model and short run time, previous studies indicate that it may not be appropriate for near-field explosions. In this study, we investigated why different results were observed for the analysis method by considering an RC beam under near-field explosion conditions with the scaled distance of 0.4-1.0 as an example. On this basis, we examined the application range of the empirical analysis method by using the finite element analysis program LS-DYNA. The results indicate that the empirical analysis method based on data from far-field explosion tests underestimates the impulse. Thus, the calculated deflection of the RC beam would be smaller than the measured deflection and arbitrary Lagrangian-Eulerian (ALE) analysis result. The ALE analysis method is more suitable for near-field explosion conditions wherein the structural responses are large.

• Journal of the Earthquake Engineering Society of Korea
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• v.14 no.1
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• pp.11-23
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• 2010

A sacrificial member with aluminum foam of excellent energy absorption capacity was proposed for the protection of significant structures. Parametric studies of explicit finite element analyses were performed to investigate the pressure mitigation of close-range air-blasts. The scaled distance of the blast had a range of Z=0.48~0.95 and an empirical blast load function was utilized. The analytical parameters of the aluminum foam were density, thickness and the existence of a cover sheet. Analytical results showed that the transmitted pressure can be controlled to have a similar level of yield values of the foam by using a foam with low density and higher thickness. As the blast load increased, the sacrificial member needed to have higher density and thickness. A cover sheet of the foam clearly showed its effect on the wider distribution of blast pressure. It is necessary to determine the design parameters of sacrificial foams considering different energy dissipation capacities according to the scaled distance.