• Journal of the Korea Concrete Institute
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• v.26 no.3
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• pp.335-342
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• 2014

In this paper, reference erosion criteria value suitable for progressive collapse analysis of RC structure due to blast load is proposed. Erosion is fundamentally a numerical technique to overcome the problems such as large numerical errors or abrupt termination of analysis and previous study has been suggested value for blast analysis. But concrete has different stress-strain curve according to strain rate. Consequently, the erosion criteria for the realistic progressive collapse simulation were suggested by comparing experiment results and numerical analysis results. Finally, the real progressive collapse of Oklahoma Federal Building was analyzed by using the median value of two values. And as a result, the analysis result is the actual collapse of the well described.

• The Bulletin of The Korean Astronomical Society
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• v.35 no.2
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• pp.74.2-74.2
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• 2010

We investigate driven magnetohydrodynamic (MHD) turbulence by including the effects of expansion and collapse of background medium. The main goal is to quantify the evolution and saturation of strength and characteristic lengths of magnetic fields in expanding and collapsing media. Our findings are as follows. First, with expansion and collapse of background medium, the magnetic energy density per comoving volume does not saturate; either it keeps decreasing or increasing with time. The magnetic energy density relative to the kinetic energy density strongly depends on the expanding or collapsing rate. Second, at scales close to the energy injection (or driving) scale, the slope of magnetic field power spectrum shallows with expansion but steepens with collapse. Third, various characteristic lengths, relative to the energy injection scale, decrease with expansion but increase with collapse. We discuss the astrophysical implications of our findings.

• Journal of the Korean Wood Science and Technology
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• v.22 no.1
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• pp.66-71
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• 1994

To increase drying rate and reduce drying degradation, pretreatments such as prefreezing and presteaming have been widely used in wood industries. Presteaming lumbers prior to kiln drying is known positively to improve its permeability, to increase diffusion coefficient and to reduce discoloration, but negatively to increase collapse. Prefreezing lumbers prior to kiln drying is also known to reduce significantly its drying defects and its shrinkages. Thus it is no doubt that the pretreated lumbers shrink diversely from the untreated. In this study the shrinkage behaviors of the pretreated specimens are investigated by drying two tropical hardwoods (Apitong and Taun) in three different dying conditions: high temperature and slow drying rate (drying in a closed cylinder), high temperature and rapid drying rate (drying in an oven) and low temperature and slow drying rate(drying at room temperature). The prefrozen specimens show the least volumetric shrinkages in most drying conditions. The specimens dried in cylinders shrink most among all drying conditions. In general the pretreated specimens reached the 30 % moisture content faster than the untreated by about 30 %.

• Journal of the Korean Society of Safety
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• v.13 no.2
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• pp.30-38
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• 1998

In this study, in order to measure energy-absorbing characteristics in impact test of CFRP thin-walled laminates and interpret the cause of decreasing age when collapse test is carried out under the environments of high temperatures and hygrothermals, the moisture absorbing behavior according to the variety of orientation angle is observed and impact collapse characteristics of no moisture absorbing status is compared with that under the environments of high temperatures and hygrothermals. Especially, we try to obtain quantitative design data to develop CFRP thin-walled laminates with energy characteristics of optimum impact absorbing. The value of the maximum loading, mean loading, rate of energy absorption energy per unit volume and mass in CFRP thin-walled laminates on the high temperatures and hygrothermals is measured much lower than under no moisture absorbing. The maximum collapse loading in dynamic impact test is taken measurements lower than in static collapse test CFRP circular laminates in high temperatures and hygrothermals. But the absorbed energy per unit mass and volume is almost same each other and the biggest amount of energy is shown in CFRP circular laminates with orientation angle of $15^{\circ}$. Therefore, in the case of using CFRP circular laminates with axisymmetric mode, CFRP thin-walled structural members with orientation angle of $10^{\circ}$, $15^{\circ}$ has generally best condition.

• Journal of the Society of Naval Architects of Korea
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• v.36 no.2
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• pp.77-93
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• 1999

The twin aims of the paper are to investigate the collapse strength characteristics of ship plating subject to impact pressure loads and to develop a simple structural design formula considering impact load effects. The general purpose nonlinear finite element program STARDYNE together with existing experimental results is used to investigate the collapse behavior of plating under impact pressure loads. The rigid plastic theory taking into account large deflection effects is applied to the development of the design formulation. In the theoretical method, the collapse strength formulation for plating subject to hydrostatic pressure is first derived using the rigid plastic theory. By including the strain rate erects in the formulation it can be applied to impact pressure problems. As illustrative examples, the collapse behavior of steel unstiffened plates and aluminum alloy stiffened panels subject to impact pressure loads is analyzed.

• Journal of KIISE:Computing Practices and Letters
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• v.16 no.12
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• pp.1229-1233
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• 2010

In event-driven wireless sensor networks, network congestion occurs when event data, which have higher transmission rates than periodic sensing data, arc forwarded to bottleneck links. As the congestion continues, congestion collapse is triggered, so most of packets from source nodes are failed to transmit to a sink node. Rate control schemes can be a solution for preventing the congestion collapse problem. In this paper, a rate control scheme that each node controls child node's data rate based on congestion patterns is proposed. Experiments show that the proposed scheme effectively controls network congestion and successfully transmits more event data packets to a sink node than existing rate control schemes.

• Structural Engineering and Mechanics
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• v.11 no.3
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• pp.315-324
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• 2001

This paper presents the experimetal result on the viscoplastic response and collapse of the titanium alloy tubes subjected to cyclic bending. Based on the capacity of the bending machine, three different curvature-rates were used to highlight the viscoplastic behavior of the titanium alloy tubes. The Curvature-controlled experiments were conducted by the curvature-ovalization measurement apparatus which was designed by Pan et al. (1998). It can be observed from experimental data that the higher the applied curvature-rate, the greater is the degree of hardening of titanium alloy tube. However, the higher the applied curvature-rate, the greater is the degree of ovalization of tube cross-section. Furthermore, due to the greater degree of the ovalization of tube cross-section for higher curvature-rates under cyclic bending, the number of cycles to produce buckling is correspondingly reduced. Finally, the theoretical formulation, proposed by Pan and Her (1998), was modified so that it can be used for simulating the relationship between the controlled curvature and the number of cycles to produce buckling for titanium alloy tubes under cyclic bending with different curvature-rates. The theoretical simulation was compared with the experimental test data. Good agreement between the experimental and theoretical results has been achieved.

• Journal of the Korean Society of Safety
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• v.30 no.2
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• pp.48-55
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• 2015

The number of collapse accidents relevant to form support since 2003 is 30 on the basis of statistical data from Ministry of Employment and Labor,. Total number of casualty was 138 (47 for deaths and 91 for injuries). The accident severity rate was high because the 4.6 casualties per one accident were occurred averagely although the incident rate was relatively low. Especially, one of form support members, the pipe supports have not been equipped adequately so that the accidents could have happened. In this regard, this study performed buckling test related to the effect of horizontal connection and slope in the single pipe which is one of typical pipe supports. The buckling load, which was estimated from the single pipe with the horizontal connectors theoretically and experimentally, was increased as more than 2 times compared to the buckling load obtained from the pipe supports without the connector. The buckling load was reduced as more than 26%, 34% slope of the single pipe comparing with 5% and 10% slope, respectively. Thus, the purpose of this study is to provide the guideline for installation and the maintenance of the pipe supports legally and institutionally to prevent the collapse accidents of the pipe supports.

• Structural Engineering and Mechanics
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• v.6 no.7
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• pp.773-784
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• 1998

To assess the collapse risk of transmission line structures subject to natural hazards, it is important to identify what hazard may cause the structural collapse. In Australia and many other countries, a large proportion of failures of transmission line structures are caused by severe thunderstorms. Because the wind loads generated by thunderstorms are not only random but time-variant as well, a time-dependent structural reliability approach for the risk assessment of transmission line structures is essential. However, a lack of appropriate stochastic models for thunderstorm winds usually makes this kind of analysis impossible. The intention of the paper is to propose a stochastic model that could realistically and accurately simulate wind loading due to severe thunderstorms. With the proposed thunderstorm model, the collapse risk of transmission line structures under severe thunderstorms is assessed numerically based on the computed failure probability of the structure.

• Transactions of the Korean Society of Automotive Engineers
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• v.1 no.3
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• pp.118-126
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• 1993

Static and dynamic crushing behaviors of composite box tube show the difference with those of metal tube. This paper investigates the characteristics of static and dynamic crushing test which were conducted to characterize the energy absorption and collapse mode of composite box tubes. Sixteen kinds of tube specimens were fabricated from[0/90] woven Glass/Epoxy fabric and autoclave cured. Axial crushing tests were performed using Instron and Dynatup Impact Tester. It is shown that collapse mode and energy absorption capacity can vary according to the aspect ratio, length, loading rate, lay-up direction of fabric, and trigger geometry of the composite box tube.