• Structural Engineering and Mechanics
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• v.87 no.4
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• pp.297-304
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• 2023

Targeted introduction of explosion-resisting and energy-absorbing materials and optimization of explosion-resisting composite structural styles in underground engineering are the most important measures for modern engineering protection. They could also improve the survivability of underground engineering in wartime. In order to test explosion-resisting and energy-absorbing effects of high-performance equal-sized-aggregate (HPESA) concrete, the explosive loading tests were conducted on HPESA concrete composite plates by field simple explosion craters. Time-history curves of the explosion pressure at the interfaces were obtained under six conditions with different explosion ranges and different thicknesses of the HPESA concrete plate. Test results show that under the same explosion range, composite plate structures with different thicknesses of the HPESA concrete plate differ significantly in terms of the wave-absorbing ability. Under the three thicknesses in the tests, the wave-absorbing ability is enhanced with the growing thickness and the maximum pressure attenuation index reaches 83.4%. The energy attenuation coefficient of the HPESA concrete plate under different conditions was regressively fitted. The natural logarithm relations between the interlayer plate thickness and the energy attenuation coefficient under the two explosion ranges were attained.

• International Journal of Naval Architecture and Ocean Engineering
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• v.13 no.1
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• pp.877-888
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• 2021

The water entry behaviors of projectiles with different cone-headed angles were studied numerically, experimentally and theoretically, mainly focusing on the hydrodynamic impact in the initial stage. Based on MMALE algorithm, it was proposed a formula of impact deceleration, which relied on the initial entry velocity and cone-headed angle. Meanwhile, in order to verify the validity of the simulation model, experiments using accelerometer and high-speed camera were carried out, and their results were in a good agreement with simulation results. Also, theoretical calculation results of cavity diameter were compared with experiments and simulation results. It was observed that the simulation method had a good reliability, which would make forecast on impact deceleration in an engineering project.

• Earthquakes and Structures
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• v.10 no.3
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• pp.669-680
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• 2016

In this paper, the underground box structure is discretized as a system with limited freedoms, and the explosion seismic wave is regarded as series of dynamic force acting on the lumped masses. Based on the local deformation theory, the elastic resistances of the soil are simplified as the effects of numbers of elastic chain-poles. Matrix force method is adopted to analyze the deformation of the structure in elastic half space. The structural dynamic equations are established and by solving these equations, the axial force, the moment and the displacement of the structure are all obtained. The influences of size ratio, the incident angle and the rock type on the dynamic response of the underground box structure are all investigated through a case study by using the proposed method.

• Special Issue of the Society of Naval Architects of Korea
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• 2015.09a
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• pp.69-73
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• 2015

An evaluation of the accidental limit state (ALS) for design of a semi-submersible drilling rig is one of the essential design requirements as well as ultimate limit state (ULS) and fatigue limit state (FLS). This paper describes the ALS evaluation on the explosion accident at shale shaker room of semi-submersible drilling rig. There are three steps for the ALS evaluation such as structural analysis at concept design, risk based safety design and structural analysis at detailed design. For the ALS evaluation at concept design, conceptual explosion overpressure from the Rule guided by the classification society was used in the structural analysis that was carried out using LS-DYNA. To set up the design accidental load (DAL), explosion analysis was carried out using FLACS taking safety barriers into consideration. Then, the structural analysis was carried out applying DAL for the ALS evaluation at detailed design. Through the ALS evaluation on the explosion at shale shaker room, the importance of the risk based safety design was described.

• Structural Engineering and Mechanics
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• v.44 no.6
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• pp.801-814
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• 2012

The strain rate effects on the interaction between a Mode I matrix crack and an inclined elliptic matrix-inclusion interface under dynamic tensile loadings were investigated numerically, and the results are in agreement with previous experimental data. It is found, for a given material system, that there are the first and the second critical strain rates, by which three kinds of the subsequent crack growth patterns can be classified in turn with the increasing strain rate, namely, the crack deflection, the double crack mode and the perpendicular crack penetration. Moreover, such a crack deflection/penetration behavior is found to be dependent on the relative interfacial strength, the inclined angle and the inclusion size. In addition, it is shown that the so-called strain rate effect on the dynamic strength of granule composites can be induced directly from the structural dynamic response of materials, not be entirely an intrinsic material property.

• Nuclear Engineering and Technology
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• v.54 no.10
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• pp.3909-3918
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• 2022

In the event of a severe accident, the reactor core may melt due to insufficient cooling. the high-temperature core melt will have a strong interaction (FCI) with the coolant, which may lead to steam explosion. Steam explosion would pose a serious threat to the safety of the reactors. Therefore, the study of steam explosion is of great significance to the assessment of severe accidents in nuclear reactors. This research focuses on the development of a two-dimensional steam explosion integrated analysis code called SEINA. Based on the semi-implicit Euler scheme, the three-phase field was considered in this code. Besides, the influence of evaporation drag of melt and the influence of solidified shell during the process of melt droplet fragmentation were also considered. The code was simulated and validated by FARO L-14 and KROTOS KS-2 experiments. The calculation results of SEINA code are in good agreement with the experimental results, and the results show that if the effects of evaporation drag and melt solidification shell are considered, the FCI process can be described more accurately. Therefore, it is proved that SEINA has the potential to be a powerful and effective tool for the analysis of steam explosions in nuclear reactors.

• Steel and Composite Structures
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• v.23 no.2
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• pp.187-194
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• 2017

To reuse a broken plain concrete (PC) arch, a retrofitting method was proposed to ensure excellent structural performances, in which carbon fiber reinforced polymers (CFRPs) were applied to repair and strengthen the damaged PC arch through bonding and wrapping techniques. Experiments were carried out to reveal the deformation and the load carrying capacity of the retrofitted composite arch. Based on the experiments, repairing and strengthening effects of the CFRP retrofitted broken arch were revealed. Simplified analysing model was suggested to predict the peak load of the CFRP retrofitted broken arch. According to the research, it is confirmed that absolutely broken PC arch can be completely repaired and reinforced, and even behaves more excellent than the intact PC arch when bonded together and strengthened with CFRP sheets. Using CFRP bonding/wrapping technique a novel efficient composite PC arch structure can be constructed, the comparison between rebar reinforced concrete (RC) arch and composite PC arch reveals that CFRP reinforcements can replace the function of steel bars in concrete arch.

• Geomechanics and Engineering
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• v.13 no.3
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• pp.489-504
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• 2017

The localized shear and the slip lines are easily observed in elastic-brittle-plastic rock. After yielding, the strength of the brittle rock suddenly drops from the peak value to the residual value, and there are slip lines which divide the macro rock into numbers of elements. There are slippages of elements along the slip lines and the displacement field in the plastic region is discontinuous. With some restraints, the discontinuities can be described by the combination of two smooth functions, one is for the meaning of averaging the original function, and the other is for characterizing the breaks of the original function. The slip lines around the circular opening in the plastic region of an isotropic H-B rock which subjected to a hydrostatic in situ stress can be described by the logarithmic spirals. After failure, the deformation mechanism of the plastic region is mainly attributed to the slippage, and a slippage parameter is introduced. A new analytical solution is presented for the plane strain analysis of displacements around circular openings. The displacements obtained by using the new solution are found to be well coincide with the exact solutions from the published sources.

• Journal of KIISE:Software and Applications
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• v.31 no.11
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• pp.1560-1567
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• 2004

In temporal logic model checking, the number of states is exponentially increased by the size of a model. This is called the state explosion problem. Abstraction, partial order, symmetric, etc. are widely used to avoid the problem. They reduce a number of states by exploiting structural information in a model. Instead, this paper proposes the relay model checking that decomposes a temporal formula to be verified into several sub-formulas and then model checking them one by one. As a result, we solve complex games that can't handle with previous techniques.

• Journal of the Society of Disaster Information
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• v.16 no.1
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• pp.44-59
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• 2020

This study analyzed a gas explosion accident. A gas smell from a underground coffee shop in the two-story building was reported to 119. A fire brigade was turned out, turned off the main valve of LPG gas cylinder on the roof, and checked the turning off of middle valve in the coffee shop. The fire brigade required a gas supplier and gas installer who arrived at the spot to take safety actions. Gas explosion occurred seven minutes after the fire brigade was withdrawn and two people died and 21 people were injured. A court decided that because the causes for gas explosion were not found, compensation responsibility could not be charged with the gas supplier, the gas installer, or Korea Gas Safety Corporation. In this reason, the court judged that only the fire brigade who was withdrawn without taking safety actions shall compensate victims or bereaved families. Therefore, fire brigades who turn out after a 119 report of a gas leak should take safety actions such as escaping people or preventing people's access and ventilating and be withdrawn when there is no possibility of fire or explosion.