• Journal of the Korea Concrete Institute
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• v.26 no.6
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• pp.715-722
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• 2014

In this paper, internal blast effect of reinforced concrete core structure were investigated using Ansys Autodyn, which is a specialized hydrocode for the analysis of explosion and impact. It is expected that internal blast case can give additional damage to the structure because it causes rebound of blast loads. Therefore, in this paper, the hazard of internal blast effect is demonstrated using UFC 3-340-02 criteria. In addition, analysis result of Autodyn, experimental result regarding rebound of blast load, and example of UFC 340-02 are compared to verify that Autodyn can analyze internal blast effect properly. Furthermore, progressive collapse mechanism of core structure which is one of the most important parts in high rise buildings is also analyzed using Autodyn. When internal blasts are loaded to core structure, the core structure is mostly damaged on its corner and front part of core wall from explosives. Therefore, if the damaged parts of core wall are demolished, progressive collapse of the core structure can be initiated.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.39 no.3
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• pp.369-380
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• 2019

When a extreme loading such as blast is applied to prestressed concrete (PSC) structures and infrastructures for an instantaneous time, serious property damages and human casualties occur. However, a existing design procedure for PSC structures such as prestressed containment vessel (PCCV) and gas storage tank do not consider a protective design for extreme internal blast scenario. Particularly, an internal blast is much more dangerous than that of external blast. Therefore, verification of the internal blast loading is required. In this paper, the internal blast resistance capacity of PSC member is evaluated by performing internal blast tests on RC and bi-directional PSC scaled down specimens. The applied internal blast loads were 22.68, 27.22, and 31.75 kg (50, 60, and 70 lbs) ANFO explosive charge at 1,000 mm standoff distance. The data acquisitions include blast pressure, deflection, strain, crack patterns, and prestressing force. The test results showed that it is possible to predict the damage area to the structure when internal blast loading occurs in PCCV structures.

• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 1998.05a
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• pp.87-94
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• 1998

폭발현상(explosion phenomena)이 항상 연소(combustion)를 수반하는 것도 아니고, 연소현상이 항상 폭발적으로 일어나는 것이 아님에도 불구하고 많은 사람들은 폭발과 연소 사이에 밀접한 관계가 있는 것으로 생각하고 있다. 일반적으로 폭발이라고 하면 우선 큰 소리와 건물이나 실내의 파괴를 연상한다. 폭발 시에 발생하는 큰소리, 이른바 폭발음은 공기 중을 전파하는 압력파(blast wave)에 의한 것이고 건물이나 실내 파괴는 그들의 내부압력 상승에 의한 것이다. 그러므로 폭발현상은 압력상승과 불가분하다고 생각해도 된다. (중략)

• Explosives and Blasting
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• v.38 no.4
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• pp.26-36
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• 2020

With the increase of expansion and use of the underground space, the possibility of an underground explosion by terrorists is increasing. In this study, after modeling a circular tunnel excavated at a depth of 50m, an explosion load was applied to the inside of the tunnel. As for the explosion load, the explosion load of the maximum explosive amount for six types of vehicle booms proposed by ATF (Bureau of Alcohol, Tobacco, and Firearms) was calculated. For the rock mass around the circular tunnel, three types of rock grades were selected according to the support pattern suggested in the domestic tunnel design. Nonlinear dynamic analysis was performed to evaluate the influence of the ground structure by examining the surface displacement using the explosion load and rock mass characteristics as parameters. As a result of the analysis, for grade 1 rock, the influence on the uplift of the surface should be considered, and for grade 2 and 3 rocks, the influence on a differential settlement should be considered. In particular, for grade 3 rocks, detailed analysis is required for ground-structure interaction within 40m. Also, it is considered that the influence of Young's modulus is the main factor for the surface displacement.

• Journal of the Korean Institute of Gas
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• v.20 no.5
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• pp.89-95
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• 2016

Keeping the gas pipelines in the common utility tunnel is useful because it has a lower risk of corrosion than conventional burial, and can prevent from excavating construction. But, explosions in common utility tunnels can cause greater damage from the blast overpressure compared to outdoor explosions, due to nature of the confined environment. Despite this fact, however, research on common utility tunnels has been limited to fire hazard and little has been studied on the dangers of explosions. This study developed scenarios of methane gas explosion caused by gas leak from gas piping within the common utility tunnel followed by unknown ignition; the study then calculated the extent of the impact of the explosion on the facilities above, and suggested the needs for designing additional safety measures. Two scenarios were selected per operating condition of safety devices and the consequence analysis was carried out with FLACS, one of the CFD tools for explosion simulation. The overpressures for all scenarios are substantial enough to completely destroy most of the buildings. In addition, we have provided additional measures to secure safety especially reducing incident frequency.

• Journal of the Korea Society for Simulation
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• v.27 no.1
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• pp.101-109
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• 2018

Field experiments as well as numerical analyses with finite element analysis codes are two valuable and complemental ways to understand the structural response under explosive blast load. However, there seems to be only limited information available about finite element analysis and experimental validation on the response of structural components under internal explosions. For complementary use of the two ways, the numerical analyses should be validated with field experiments by comparing their results. In this paper, a small-scaled reinforced concrete building with a room is employed for experimental investigations. An amount of TNT is detonated at the center of the room. Pressure at three different sites in the room, displacement of centers of two walls, and damage patterns of four walls are measured and compared to results from numerical analyses. The experimental results are much similar to the numerical analyses results. The finite element analysis code ANSYS AUTODYN is employed to numerically analyze both pressure distribution inside the room and response of walls subjected to blast pressure. The feasibility and validity of the numerical analysis on the reponses of structural components under internal explosions are discussed in terms of structural damage assessment, and evaluated as the same damage in the analysis and the experiments.

• Journal of Advanced Marine Engineering and Technology
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• v.35 no.6
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• pp.849-855
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• 2011

Emergency batteries on board are used for stairs, pathway lights, and emergency communications during alternator black-out. In addition, there are engine start-up batteries in lifeboats. Typically, these batteries are installed under the Classification Rules. However, Since batteries inside life boats are installed in a confined narrow space, it is difficult to perform regular maintenances. Also, even though there are air vents in the life boat, the temperature inside the life boat often reaches above $65^{\circ}C$, which is much higher than the regulation temperature, $45^{\circ}C$. In this paper, we will summarize the accident of battery explosion occurred in MMU training ship, and possible causes. We will propose preventive measures of battery explosions as well as the revision of the regulation.

• Proceedings of the Materials Research Society of Korea Conference
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• 2009.05a
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• pp.58.2-58.2
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• 2009

금속 와이어를 전기폭발법에 의해 증기 상태로 만든 후 응축시킬 때 제조되는 금속나노분말의 크기특성을 파악하기 위하여 제조장치에 샘플링 포트를 삽입하여 실시간 입자 측정기(Scanning Mobility Particle Sizer; SMPS) 로 14~615 nm 범위의 크기분포를 측정하였다. SMPS는 입자의 크기에 따라 전기적 이동도가 달라지는 원리를 이용하여 공기 중에 부유된 나노입자의 크기분포를 수 분내에 측정하는 실시간 입자 측정기이다. 금속나노분말 제조장치 내부는 약 0.5 bar 수준으로 불활성가스로 채워져 있어서 대기압보다 높은 고압조건이므로 SMPS 전단에 작은 노즐이 삽입된 pressure reducer를 부착하여 적정한 압력 수준으로 낮춘 후 SMPS로 나노분말의 크기분포를 실시간으로 측정하였다. 제조공정이 진행되면서 전기폭발이 주기적으로 발생하는 동안에 SMPS로 측정한 14~615 nm 범위 입자의 총 수농도는 약 $10^7$ 개/$cm^3$ 수준으로 매우 높았고, 약 100 nm와 200 nm에서 고농도 피크를 나타내는 bimodal 분포를 나타냈다. 반면 전기폭발이 잠시 중단되는 경우 입자의 총 수 농도는 약 $10^4$ 개/$cm^3$ 수준으로 낮아지고, 약 20 nm 이하의 입자가 대부분을 차지하면서 입자의 크기가 커질수록 농도가 낮아지는 형태의 크기분포로 바뀌었다. 본 연구를 통해 얻어진 제조장치 내부의 나노분말 크기분포 자료는 고품질 제품을 생산하기 위해 나노분말의 크기분포를 제어하는 분급장치 개발에 활용될 수 있을 것으로 기대된다.

• Journal of the Korean Institute of Gas
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• v.20 no.1
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• pp.29-39
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• 2016

Electrical apparatuses for use in the presence of explosive gas atmospheres have to be special designed to prevent them from igniting the explosive gas. Flameproof design implies that electrical components producing electrical sparks are contained in enclosures and withstand the maximum pressure of internal gas or vapours. In addition, any gaps in the enclosure wall have to designed in such a way that they will not transmit a gas explosion inside the enclosure to an explosive gas or vapours atmosphere outside it. In this study, we explained some of the most important physical mechanism of Maximum Experimental Safe Gap(MESG) that the jet of combustion products ejected through the flame gap to the external surroundings do not have an energy and temperature large enough to initiate an ignition of external gas or vapours. We measured the MESG and maximum explosion pressure of propane and acetylene by the test method and procedure of IEC 60079-20-1:2010.When the minimum MESG is measured, the concentration of propane, acetylene in the air is higher than the stoichiometric point and their explosion pressure is the highest value.

• Fire Science and Engineering
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• v.34 no.2
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• pp.86-93
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• 2020

This study aims to maintain the safety of an outdoor storage tank through the fundamental case analysis of explosion and fire accidents in the storage tank. We consider an accident caused by the explosion of fire inside the tank, as a result of the gradual spreading of the residual fire generated by wind lamps flying off a workplace in the storage tank yard. To determine the cause of the accident, atmospheric diffusion conditions were derived through CCTV image analysis, and the wind direction was analyzed using computational fluid dynamics. Additionally, the amount of oil vapor inside the tank when the floating roof was at the lowest position, and the behavior of the vapor inside the tank when the floating roof was at the highest position were investigated. If the cause of the explosion in the storage tank is identified and the level of the storage tank is maintained below the internal floating roof, dangerous liquid fills the storage tank, and the vapor in the space may stagnate on the internal floating roof. We intend to improve the operation procedure such that the level of the storage tank is not under the Pontoon support, as well as provide measures to prevent flames from entering the storage tank by installing a flame arrester in the open vent of the tank.