• Journal of the Korea Concrete Institute
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• v.28 no.6
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• pp.673-683
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• 2016

In recent years, frequent terror or military attack by explosion, impact, fire accidents have occurred. Particularly, World Trade Center collapse and US Department of Defense Pentagon attack on Sept. 11 of 2001. Also, nuclear power plant incident on Mar. 11 of 2011. These attacks and incidents were raised public concerns and anxiety of potential terrorist attacks on major infrastructures and structures. Therefore, the extreme loading researches were performed of prestressed concrete (PSC) member, which widely used for nuclear containment vessel and gas tank. In this paper, to evaluate the blast resistance capacity and its protective performance of bi-directional unbonded prestressed concrete member, blast tests were carried out on $1,400{\times}1,000{\times}300mm$ for reinforced concrete (RC), prestressed concrete without rebar (PSC), prestressed concrete with rebar (PSRC) specimens. The applied blast load was generated by the detonation of 55 lbs ANFO explosive charge at 1.0 m standoff distance. The data acquisitions not only included blast waves of incident pressure, reflected pressure, and impulse, but also included displacement, acceleration, and strains at steel, concrete, PS tendon. The results can be used as basic research references for related research areas, which include protective design and blast simulation under blast loading.

• Journal of the Korean Data and Information Science Society
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• v.26 no.4
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• pp.791-799
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• 2015

In random walk hypothesis, we assume that current change of financial time series is independent of past values. It is interpreted as an existency of a unit root in ARMA models and many researches have been focused on whether ${\rho}$ < 1 or not. If some financial data are generated from an explosive autoregressive model, the chance of a bubble economy increases. We have to find the symptoms of it in advance. Since some well-known parameter estimators contain the parameter itself and other statistic is constructed under a specific parameter structure assumption, those are difficut to be adopted. In this paper we investigate a test for explosive autoregressive models using slope signs. We found the properties of the slope sign test statistic under both independent error and correlated error conditions, mainly by simulations.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.7
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• pp.677-683
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• 2011

Until now, several empirical models for assessing the damage due to TNT explosions have been proposed. A set of analytical solutions for the time-dependent radius of an expanding fire-ball after detonation of TNT was obtained by solving the continuity, Euler (momentum), and energy equations with a "polytrope" assumption at the fire-ball center. The shock waves developed from the rapid expansion of a fire-ball under water were obtained by using the KirkwoodBBethe hypothesis. The calculated period of bubble oscillation and the maximum radius of the bubble resulting from the fire-ball due to a violent underwater TNT explosion were in good agreement with the experimental data.

• Journal of the Korean Institute of Gas
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• v.22 no.4
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• pp.13-26
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• 2018

Currently, local regulations, such as KS Code, do not clearly specify how to calculate the range of hazardous area, so the dispersion modeling program should be used to select dispersion. The purpose of this study is to present a methodology of determining the range of hazardous area which is simpler and more reasonable than modelling by using representative materials and process conditions. Based on domestic and overseas regulations that are currently in effect, variables affecting distance to LFL(Lower Flammable Limit) were selected. A total of 16 flammable substances were modelled for substance variables, process conditions variables, and weather conditions variables, and the statistical analysis selected the variables that affect them. Using the selected variables, a three-step classification method was prepared to select the range of locations subject to explosion hazard.

• Journal of the Korean Society of Marine Environment & Safety
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• v.24 no.6
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• pp.825-833
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• 2018

In this study, one calculated the range of damage to the combustion characteristics according to the composition of LNG and the size of leaking holes, and analyzed the damage effect in case of leakage accidents caused by pipe damage in the re-gasification process for the LNG supply system. In order to confirm the combustion characteristics according to LNG composition, there was no significant difference in the result of risk analysis by LNG-producing areas. However, the higher the methane content of the components, the lower the risk of flash fire, hazardous areas of overpressure due to explosion, and thermal radiation damage caused by jet fire. In addition, one investigated the effect of leakage, holes, and ruptures on the risk range and explosions according to the size of the pipe-leakage hole. Also, the influence of overpressure and the range of damage from radiant heat could be predicted. One confirmed the effect of LNG composition and pipe-leakage size on fire and explosion.

• Explosives and Blasting
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• v.35 no.3
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• pp.1-8
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• 2017

In this paper, parametric studies are conducted to evaluate the contribute effect of multi layered room and pillar mine structures by underground accidental explosions. Influence of PPV(Peak Particle Velocity) obtained from large explosion at a multi layered room and pillar mine was numerically simulated by using AUTODYN. Parameters for contribution rate Analysis was analyzed by the robust design method. Orthogonal array is $L_9(3^4)$, which was adopted in this study, the parameters were pillar height, pillar width, mine span and sill pillar of 3 levels. Results of analysis showed that bottom mine of vertical direction from explosion point are most affected by pillar height, followed by sill pillar thickness, mine span and pillar width. Parameters affecting adjacent mine of horizontal direction from explosion are in the order of pillar width, mine span, pillar height and sill pillar thickness.

• Explosives and Blasting
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• v.37 no.4
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• pp.10-16
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• 2019

Information on overpressure, positive phase duration, and impulse are required to assess the effects of shock waves or pressure waves on the structure. In this study, the overpressure and positive phase duration were determined by applying the Multi-Energy Method, which is found to be effective in analyzing the explosion of vapor clouds. Based on the total heat of combustion estimated in the cyclohexane vapor cloud explosion in the Nypro Ltd(UK), overpressure and positive phase duration at the distance of 40, 80, 120, 160, 200, 240, 280, 320, 360(m) from the source of explosion were evaluated. Overpressure was shown to decrease exponentially and positive phase duration increased almost linearly with distance. A probit function was used to assess the probability of damages for the structures at each distance using the overpressure and impact obtained at the above mentioned distances. The Analyses of probability of damages have shown that there is a high probability of collapse at distances within 120m, major damage to structures within 240m, and minor damage and breakage of window panes of structures occur over the entire distances.

• Journal of the Korean Institute of Gas
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• v.12 no.3
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• pp.68-74
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• 2008

Measurements were performed to investigate the effects on flame and pressure development by varying locations of multiple obstacles in a top-venting explosion chamber. The chamber dimension was 1000 mm in height with a $700\;{\times}\;700\;mm^2$ cross-section and a rectangular vent area of $700\;{\times}\;700\;mm^2$. Three different multiple obstacles with blockage ratio of 30% were used by changing from 200 mm, 500 mm to 800 mm in heights within the chamber. Temporally resolved flame front images were recorded by a high speed camera to investigate the interaction between the propagating flame and the obstacles. The results showed that the triangular bar caused the fastest flame developments at given times whereas the lowest was obtained with the cylindrical bar. It was also found that local flame displacement speeds of different obstacles were sensitive to the locations of obstacles. The local speed becomes larger in going from 200 mm, to 500 mm and to 800 mm in heights. The obstacles in height of 800 mm yielded the highest overpressure whereas the lowest was in height of 200 mm.

• Explosives and Blasting
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• v.24 no.2
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• pp.41-50
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• 2006

Excavation by explosives blasting necessarily involves noise and vibration, which is highly prone to face claims on the environmental and structural aspects from the neighbors. When the blasting carried out in the vicinity of a structure, the effect of blasting vibration on the stability of the structure should be carefully evaluated. In the conventional method of evaluation, an equation for blast vibration is obtained from test blasting which is later used to determine the amount of charge. This method, however, has limitations in use since it does not consider topography and change in ground conditions. In order to overcome the limitations, dynamic numerical analysis is recently used in continuum or discontinuous models, where the topography and the ground conditions can be exactly implemented. In the numerical analysis for tunnels and rock slopes, it is very uncommon to simulate multi-hole blasting. A single-hole blasting pressure is estimated and the equivalent overall pressure at the excavation face is used. This approach based on an ideal case usually does not consider the ground conditions. And this consequently results in errors in calculation. In this presentation of a case study, a new approach of using blast waves obtained in the test blast is proposed. The approach was carried out in order to improve the accuracy in calculating blasting pressure. The stability of a structure in the vicinity of a slope blasting was examined using the newly proposed method.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2009.04a
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• pp.259-262
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• 2009

지진이나 충돌 등과 같은 동적 하중은 하중 속도에 따라 재료의 파괴 거동이 변하기 때문에 하중 속도는 하중의 위치나 크기와 더불어 재료의 파괴 거동을 결정짓는 중요한 요소 중 하나이다. 특히 콘크리트와 같은 취성재료의 경우 재료의 속도 의존적 거동에 의해 가해진 하중으로부터 발생된 균열의 형상이나 진행 형태가 변하므로 전체 구조물의 거동에도 큰 영향을 끼친다. 따라서 취성재료를 이용한 속도 의존적 파괴 거동에 관한 연구는 그 중요성에 의해 다양한 방법으로 진행되어져 왔으나, 해석을 통한 빠른 하중에서의 파괴 거동 해석은 대부분 무시되어왔다. 하지만 최근 폭발과 같은 매우 빠른 하중에서의 재료의 파괴 거동 대한 관심이 증대되고 있고, 그에 관한 연구의 필요성도 점차 커지고 있다. 따라서 본 연구에서는 irregular lattice model의 하나인 rigid-body-spring networks(RBSN)를 이용하여 취성 재료의 파괴 거동해석에 적합한 수치 해석 모델을 개발하였다. 동적 해석을 위해 각 요소에 질량을 부여하고, 각 요소의 거동은 시간 적분에 의하여 계산된다. 이를 이용하여 빠른 하중에서의 취성 재료의 파괴 거동 특성을 분석하고 기존 실험과의 비교를 통해 수치 해석 모델의 타당성을 입증하였다.