• Explosives and Blasting
• /
• v.37 no.4
• /
• pp.10-16
• /
• 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 Society of Safety
• /
• v.36 no.4
• /
• pp.71-79
• /
• 2021

In this study, a real-scale fuel-cell room of volume 1.36 m³ is constructed to confirm the explosion characteristics of hydrogen-air mixture gas in a hydrogen-powered house. A volume concentration of 40% is applied in the fuel-cell room as the worst-case scenario to examine the most severe accident possible, and two types of doors (made of plastic sheet and wood) are fabricated to observe their effects on the overpressure and impulse. The peak overpressure and impulse based on distance from the ignition source are experimentally observed and assessed. The maximum and minimum overpressures with a plastic-sheet door are about 20 and 6.7 kPa and those with a wooden door are about 46 and 13 kPa at distances of 1 and 5 m from the ignition source, respectively. The ranges of impulses for distances of 1-5 m from the ignition source are about 82-28 Pa·s with a plastic-sheet door and 101-28 Pa·s with a wooden door. The amount of damage to people, buildings, and property due to the peak overpressure and impulse is presented to determine the safe distance; accordingly, the safe distance to prevent harm to humans is about 5 m based on the 'injuries' class, but the structural damage was not serious.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.24 no.6
• /
• pp.77-84
• /
• 2020

In this paper, we developed a damage evaluation technique that can determine the damage location of a long-sized structure such as a cable-stayed bridge, and verified the performance of the developed technique through experiments. The damage assessment method aims to extract data that can evaluate the damage of the structure without the undamage data and can determine the damage location only by analyzing the response data of the structure. To complete this goal, we developed a damage assessment technique that considers variability based on the IMD theory, which is a statistical pattern recognition technique, to identify the damage location. To complete this goal, we developed a damage assessment technique that considers variability based on the IMD theory, which is a statistical pattern recognition technique, to identify the damage location. To evaluate the performance of the developed technique experimentally, cable damage experiments were conducted on model cable-stayed bridges. As a result, the damage assessment method considering variability automatically outputs the damageless data according to external force, and it is confirmed that the performance of extracting information that can determine the damage location of the cable through the analysis of the outputted damageless data and the measured damage data is shown.

• Journal of the Korean Society of Safety
• /
• v.22 no.4
• /
• pp.110-116
• /
• 2007

There have been 3E problems of energy, economy and environment since the earth has its history. Especially, as the industrial society is highly developing, human need in daily life has also changed drastically. With the introduction of 40 hour working week system, more households enjoy picnics on weekends. More gas accidents take place on Saturdays and on Sundays than any other days of week. Consequently, this study tries to find out the influence of flame caused by the explosion of butane canister on the adjacent combustibles and people by simulating relevant quantity of TNT. In addition, the damage estimation was conducted by using API regulations. If the scale of the radiation heat is known by calculating the distance of flame influence from the explosion site, the damage from the site can be easily estimated. And the accident damage was estimated by applying the influence on the adjacent structures and people into the PROBIT model. According to the pro bit analyze, the spot which is 50cm away from the flame has 97% of the damage probability by the first-degree burn, 8% of the damage probability by the second-degree burn and 4% of the death probability by the fire.

• Proceedings of the KSRS Conference
• /
• 1999.11a
• /
• pp.443-449
• /
• 1999

The investigation of the amount of the ecosystem damage on the shoreline due to the NAHODKA oil-spill accident, which occurred in the Sea of Japan, was attempted by using geoinformatics. At first, it was assumed that symbolical vegetation's distribution could be specified in the coast in Ishikawa Pref. where the heavy oil was washed, and surveyed the regional distribution. Then, the presumption result of those environmental capacities was arranged by GIS. In addition, the amount of the ecosystem damage was presumed as cost necessary though a symbolical living thing for the retreat because of the base line by the heavy oil drifting ashore was recovered. By comparing the vegetation line and the surveying data which shows environmental capacity, the retreat areas of the vegetation were 1100-1200 $m^2$. When the amount of damage on the ecosystem of the NAHODKA oil-spill accident was presumed based on the retreat area of this vegetation and the restoration cost, the amount of damage within Shioya beach which 150m in the surveying range became 2 to 2.5 million Yen. Because the extension distance from the Shioya beach to the Katano beach was about 3,500m, the amount of damage became about 46 to 65 million Yen. As a result of calculation for the amount of damage on the ecosystem of the NAHODKA oil-spill accident, it was estimated approximately 1,400 to 2,000 million Yen in the shoreline of Ishikawa Pref., because the total extension of beaches in Ishikawa Pref. is about 110km.

• Journal of the Korean Society of Safety
• /
• v.25 no.3
• /
• pp.53-60
• /
• 2010

LPG(Liquefied Petroleum Gas) vehicles in metropolitan area are being applied to improve air quality and have been proven effective for the reduction of air pollutant. In addition, LPG demand is growing rapidly as an environmentally friendly energy source and its gas station is also increasing every year. Consequently, this study tries to find out the influence of flame caused by the VCE(Vapor Cloud Explosion) in filling station on the adjacent combustibles and people by simulating relevant quantity of TNT. In addition, the damage estimation was conducted by using API regulations. If the scale of the radiation heat is known by calculating the distance of flame influence from the explosion site, the damage from the site can be easily estimated. And the accident damage was estimated by applying the influence on the adjacent structures and people into the PROBIT model. According to the probit analyze, the spot which is 30m away from the flame has 100% of the damage probability by the first-degree burn, 99.2% of the damage probability by the second-degree burn and 93.4% of the death probability by the fire.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.25 no.10
• /
• pp.1551-1558
• /
• 2001

Recently, a number of underground pipelines have been drastically increased. The integrity of these buried pipelines, especially gas transmitting pipelines, is of importance due to an explosive characteristic of natural gas. The third party damage is known as one of the most critical factor which causes fatal accidents. For this reason, a number of systems detecting third party damage are under development. The major concern in the development of third party damage detection system is to transmit vibration signals out of accelerometer to signal conditioner and data acquisition system without any interference caused by noise. The objective of this paper is to develope a fiber optic accelerometer applicable to third party damage detection system. A fiber optic accelerometer was developed by use of combining principles of one degree of freedom vibration model and an extrinsic Fabry-Perot interferometer. The developed fiber optic accelerometer was designed to perform with a sensitivity of 0.06mVg, a frequency range of less than 6kHz and an amplitude range of -200g to 200g. The developed, accelerometer was compared with a piezoelectric accelerometer and calibrated. In order to verify the developed accelerometer, the field experiment was performed. From the field experiment, vibration signals and the location of impact were successfully detected. The developed accelerometer is expected to be used for the third party damage detection system which requires long distance transmission of signals.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.7 no.4
• /
• pp.721-726
• /
• 2006

This paper is on intelligent decision system by safety distance of gas storage tank(IDSG). The safety distance fixed up by law is used to prevent from the injury by explosion of storage tank on the spot. However, it is not easy for a layman to decide a proper safety distance considering the size, shape and place of the storage tank. Therefore, this thesis shows the user-friendly intelligent decision system which a layman can decide the Bas related law, the size, shape and place of the storage tank by the intelligent decision, and it is to make assurance doubly sure for safety supervision on the spot. Also, the paper can make the data for the damage influence distance of overpressure by the explosion of the storage tank calculated by the scaling law of Hopkinson with the fixed distance by law, and safety range can be grasped with the graphic which is printed by the PHAST(Process Hazard Analysis Software Tool) model using this data.

• Earthquakes and Structures
• /
• v.12 no.1
• /
• pp.1-12
• /
• 2017

Historical earthquakes have shown that successive seismic events may occur in regions of high seismicity. Such a sequence of earthquakes has the potential to increase the damage level of the structures, since any rehabilitation between the successive ground motions is practically impossible due to lack of time. Few studies about this issue can be found in literature, most of which focused their attention on the seismic response of SDOF systems or planar frame structures. The aim of the present study is to examine the impact of seismic sequences on the damage level of 3D multistorey R/C buildings with various structural systems. For the purposes of the above investigation a comprehensive assessment is conducted using three double-symmetric and three asymmetric in plan medium-rise R/C buildings, which are designed on the basis of the current seismic codes. The buildings are analyzed by nonlinear time response analysis using 80 bidirectional seismic sequences. In order to account for the variable orientation of the seismic motion, the two horizontal accelerograms of each earthquake record are applied along horizontal orthogonal axes forming 12 different angles with the structural axes. The assessment of the results revealed that successive ground motions can lead to significant increase of the structural damage compared to the damage caused by the corresponding single seismic events. Furthermore, the incident angle can radically alter the successive earthquake phenomenon depending on the special characteristics of the structure, the number of the sequential earthquakes, as well as the distance of the record from the fault.

• Smart Structures and Systems
• /
• v.17 no.6
• /
• pp.957-980
• /
• 2016

Structural damage detection (SDD) is a challenging task in the field of structural health monitoring (SHM). As an exploring attempt to the SDD problem, a hybrid self-adaptive Firefly-Nelder-Mead (SA-FNM) algorithm is proposed for the SDD problem in this study. First of all, the basic principle of firefly algorithm (FA) is introduced. The Nelder-Mead (NM) algorithm is incorporated into FA for improving the local searching ability. A new strategy for exchanging the information in the firefly group is introduced into the SA-FNM for reducing the computation cost. A random walk strategy for the best firefly and a self-adaptive control strategy of three key parameters, such as light absorption, randomization parameter and critical distance, are proposed for preferably balancing the exploitation and exploration ability of the SA-FNM. The computing performance of the SA-FNM is evaluated and compared with the basic FA by three benchmark functions. Secondly, the SDD problem is mathematically converted into a constrained optimization problem, which is then hopefully solved by the SA-FNM algorithm. A multi-step method is proposed for finding the minimum fitness with a big probability. In order to assess the accuracy and the feasibility of the proposed method, a two-storey rigid frame structure without considering the finite element model (FEM) error and a steel beam with considering the model error are taken examples for numerical simulations. Finally, a series of experimental studies on damage detection of a steel beam with four damage patterns are performed in laboratory. The illustrated results show that the proposed method can accurately identify the structural damage. Some valuable conclusions are made and related issues are discussed as well.