• Structural Engineering and Mechanics
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• v.32 no.2
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• pp.283-300
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• 2009

The characteristic response of a structure to blast load may be divided into two distinctive phases, namely the direct blast response during which the shock wave effect and localized damage take place, and the post-blast phase whereby progressive collapse may occur. A reliable post-blast analysis depends on a sound understanding of the direct blast effect. Because of the complex loading environment and the stress wave effects, the analysis on the direct effect often necessitates a high fidelity numerical model with coupled fluid (air) and solid subdomains. In such a modelling framework, an appropriate representation of the blast load and the high nonlinearity of the material response is a key to a reliable outcome. This paper presents a series of calibration study on these two important modelling considerations in a coupled Eulerian-Lagrangian framework using a hydrocode. The calibration of the simulated blast load is carried out for both free air and internal explosions. The simulation of the extreme dynamic response of concrete components is achieved using an advanced concrete damage model in conjunction with an element erosion scheme. Validation simulations are conducted for two representative scenarios; one involves a concrete slab under internal blast, and the other with a RC column under air blast, with a particular focus on the simulation sensitivity to the mesh size and the erosion criterion.

• Journal of the Korean GEO-environmental Society
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• v.25 no.7
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• pp.5-19
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• 2024

During the blasting process, a fracture zone is formed in the vicinity of the blast hole. Any damage that extends beyond the excavation boundary line necessitates the implementation of an additional support system to assure safety. Typically, fracture zone radius is estimated from blast hole pressure using theoretical methods due to its simplicity. However, linear charge concentration (kg/m) is used for tunnel blasting. This paper compiles Swedish experimental datasets to estimate the radius of fracture zones based on linear charge concentration. Further numerical analyses are performed in LS-DYNA for coupled single-hole blasting. The Riedel-Hiermaier-Thoma (RHT) model has been selected as the constitutive model for this investigation. The numerical model is validated against small-scale laboratory tests. Parametric studies are conducted to predict fracture zones in granite and sandstone rocks using two kinds of explosives, PETN and AFNO. The analyses evaluate ten types of blast hole sizes, ranging from 17 to 100 mm. The results indicate that granite has a larger fracture zone than sandstone, and the PETN explosive predicts more damage than ANFO. Smaller blast holes exhibit smaller fracture zones in comparison to larger blast holes. Wave propagation is more rapidly attenuated in granite than in sandstone. Subsequently, the predicted fracture zone outcomes are compared with the empirical dataset. Fracture zones of medium blast hole diameter align well with the experimental data set. A predictive equation is derived from the data set, which may be used to evaluate blast design to manage fracture zones beyond the excavation line.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.8
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• pp.1989-1998
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• 1995

Characteristics of the flame propagation for normal and abnormal combustion in hydrogen premixture in a cylindrical constant-volume combustion chamber are studied numerically. A detailed hydrogen oxidation kinetic mechanism, mixture transport properties and a model describing spark ignition process are used. The calculated pressure-time history of the stable deflagration wave propagation agrees well with the experiment. The ignition of the premixture in the unburned gas, initiated by the hot spot, causes a transition from deflagration to detonation under some initial temperature and pressure. Under the initial conditions with high temperature and pressure, excessive ignition energy initiates a strong blast wave and a detonation wave that follows. The chemical reaction in the detonation wave is much more vigorous than that in the deflagration wave and the peak pressure in the detonation wave is much higher than the equilibrium value.

• Journal of Korean Association for Spatial Structures
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• v.16 no.4
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• pp.117-123
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• 2016

The blast load is classified into free-air blast and surface blast following the location of explosion and surface. In this paper, several equations for blast load calculation are explained briefly and a modified equation for free-air blast load is suggested. The modified equation is based on Kingery-Bulmash equation which is used in UFC 3-340-02 and Conwep model. In this modified equation, the process of calculation is simplified against the original equation, and the number of coefficients is reduced under 5. As a result, each parameter of estimated data by modified equation has less than 1% of error range comparing with Kingery-Bulmash equation.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.269-272
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• 2008

Blast load, an impulsive load with extremely short time duration with very high pressure, is effected by ground and air condition, weight of charge, shape and location of structure. In this study, a blast dynamic analysis for the air-structural integrated model considering dynamic properties of materials and simulation of complex blast wave propagation by Arbitrary Lagrangian- Eulerian technique is suggested to perform an accurate blast analysis of concrete structures. For the verification of the proposed blast analysis method, which is the air-structure integrated model using ALE technique, the comparison of analysis and experimental results is performed. The verification confirms that the simulation of realistic behavior of RC wall structures is possible using ALE method. Also, the example cases which have been analyzed using this method show that the estimation to the structural failure criterion for blast load failure can be represented by energy absorbtion procedure.

• Earthquakes and Structures
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• v.7 no.3
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• pp.349-365
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• 2014

The dynamic response of structures under extremely short duration dynamic loads is of great concern nowadays. This paper investigates structures' response as well as the associated structural damage to explosive loads considering and ignoring the supporting soil flexibility effect. In the analysis, buildings are modeled by two alternate approaches namely, (1) building with fixed supports, (2) building with supports accounting for soil-flexibility. A lumped parameter model with spring-dashpot elements is incorporated at the base of the building model to simulate the horizontal and rotational movements of supporting soil. The soil flexibility for various shear wave velocities has been considered in the investigation. In addition, the influence of variation of lateral natural periods of building models on the obtained response and peak response time-histories besides damage indices has also been investigated under blast loads with different peak over static pressures. The Dynamic response is obtained by solving the governing equations of motion of the considered building model using a developed Matlab code based on the finite element toolbox CALFEM. The predicted results expressed in time-domain by the building model incorporating SSI effect are compared with the corresponding model results ignoring soil flexibility effect. The results show that the effect of surrounding soil medium leads to significant changes in the obtained dynamic response of the considered systems and hence cannot be simply ignored in damage assessment and response time-histories of structures where it increases response and amplifies damage of structures subjected to blast loads. Moreover, the numerical results provide an understanding of level of damage of structure through the computed damage indices.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.35 no.4
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• pp.207-214
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• 2022

A prediction model is proposed for a blast load acting on a column component because of an external explosion. The model can predict the pressure-time histories acting on a column using the fitting curves established from a database composed of finite-element (FE) analysis results. To this end, 70 numerical simulations using the commercial software AUTODYN were performed by changing the column width. To confirm the performance of the proposed model, pressure-time histories estimated from an existing empirical formula and the proposed model were compared based on the FE analysis results. It was verified that the proposed model can more precisely predict the pressure-time histories compared with the existing model.

• Korean Chemical Engineering Research
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• v.54 no.3
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• pp.360-366
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• 2016

The Propulsion Test Facilities for the development of Korea Space Launch Vehicle-II are being built, some test facilities are completed and various combustion tests are running. The Propulsion Test Facilities consists test-stand, which carries out tests for engine development model, and various sub-systems and vessels containing LOX and Jet A-1 as propellant. There are always risks of fire and explosion at the test-stand since engine development model is conducted at test-stand with real combustion test with very high pressure, mixed propellant and high energy. In this paper, in order to establish the consequence analysis and risk reduction measures in the Propulsion Test Facilities, followings are considered. 1) a propellant leak accident scenario is assumed in test-stand. 2) TNT equivalent model equation based on blast wave of the explosion was used to analyze blast overpressure and impacts. Also, technical, systematic and managemental measure is described to ensure risk reduction for propulsion test facility.

• Structural Engineering and Mechanics
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• v.60 no.6
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• pp.923-937
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• 2016

The common prospect in diminishing mine-blast vibration is decreasing vibration with increasing distance. This paper indicates that, contrary to the general expectancy, vibration waves change their forms when they are travelling through the low velocity layer like coal and so-called guided waves moving the vibration waves to longer distances without decreasing their amplitudes. The reason for this unexpected vibration increase is the formation of guided waves in the coal bed which has low density and low seismic velocity with respect to the neighboring layers. The amplitudes of these guided waves, that are capable of traveling long distances depending on the seam thickness, are several times higher than that of the usual vibration waves. This phenomenon can many complaints from the residential areas very far away from the blasting sites. Thus, this unexpected behavior of the coal beds in the surface coal mines should also be considered in vibration minimization studies. This study developed a model to predict the effects of guided waves on the propagation ways of blast-induced vibrations. Therefore, vibration mitigation studies considering the nearby buildings can be focused on these target places.

• Journal of the Korea Society for Simulation
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• v.28 no.1
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• pp.109-115
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• 2019

The probability of lethality of personnel targets inside a room is a key issue at assessing effectiveness of a weapon system. In this study, the minimum charge weight to achieve 100% lethality of personnel targets inside a box-type room is proposed at each side length of a base of a room. A fast running blast wave model is used to simulate the pressure-time histories of the blast generated by an internal explosion inside a room, and Axelsson SP method is used to evaluate the lethality of personnel targets under the blast. 176 different internal explosion scenarios are simulated for cases of TNT weights ranging from 20kg to 170kg inside a room whose square base has a side length ranging from 5m to 15m. A linear model and a charge-density model were developed to predict the minimum charge weight to achieve 100% lethality inside a room given a length of a base of a room.