• Transactions of the Korean Society of Mechanical Engineers
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• v.8 no.5
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• pp.425-434
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• 1984

The concept of intermittent interlaminar bonding is investigated as a means of improving the fracture toughness of cross-ply Gr/Ep composites without significant loss of tensile strength and modulus. The concept of linear elastic fracture mechanics(LEFM)is used to study the effects of strong bonded area and bonding composites. The experimental results indicate that the fracture toughness and notch strength of intermittent interlaminar bonded composities are improved and the tensile strength only decreased by 3-8% in comparison to those of the fully bonded composites. Damage zones around the crack tip are detected by the modified X-Ray non-destructive testing technique and the fractography. The improvement of toughness is explained based on the damage zones. The mechanisms of damage zone are shown to be caused by subcrack along the fiber on the 0.deg. ply, matrix cracking along the fiber on the 90.deg. ply, interlaminar delamination, and ply pull-out of the 0.deg. ply.

• Journal of Digital Contents Society
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• v.19 no.5
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• pp.899-906
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• 2018

In the entire process of disaster management, it is very significant to construct related information as well as perform quantitative assessment of damage losses with respect to minimizing the effect of disasters. Many countries have paid much attention not only to studying risk assessment methodologies including constructing inventories, hazard mapping, vulnerability assessment and direct/indirect damage loss estimation, but also to developing risk analysis tools investigated in this paper. We conducted comparison studies of representative earthquake damage risk analysis tools, and the result of this study is able to provide useful information to decision makers and researchers who can contribute to development of effective disaster management.

• Journal of Korean Society of Forest Science
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• v.108 no.4
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• pp.618-627
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• 2019

An increase in damage to crops and facilities caused by wildlife such as wild boar causes serious social and economic problems to the rural economy in Korea. This study aims to estimate the economic losses incurred to rural households in mountain villages near protected areas in Korea due to the damage to agricultural and forestry production by wildlife. The case of mountain villages located in Toji-myeon, Gurye-gun near the Jirisan National Park was studied as an example. Data were collected by interviewing 84 households across six mountain villages in April and June 2016. The results indicate that the economic losses due to wildlife damage in 2015 were estimated to be 1.65 million KRW per household, which is a total of 138.63 million KRW for the 84 households. Among local products, the most damaged products were chestnut, fern-brake, wild pear, peach, and potato, whereas the most damaged products per production area were sweet potato, peach, corn, and potato. The potential economic losses caused by wildlife damage to agricultural and forestry production in whole Gurye-gun area was estimated to be around 4.0 billion KRW in 2015. However, the municipal government budget for the compensation of wildlife damage was only 0.9 percent of the potential rural economic losses caused by wildlife damage in 2015. The results of our study suggest that the compensation scheme for wildlife damage is inadequate in the respect of social justice. Considering the low financial capacity of the municipalities in mountain areas, the central government should take a progressive responsibility by allocating more financial resources for compensation of economic losses of rural households due to wildlife damage. The equitable and effective governance of wildlife conservation is required for sustainable development of rural communities near protected areas.

• Journal of the Korea Concrete Institute
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• v.26 no.5
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• pp.627-634
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• 2014

In this study, standoff detonation tests and static beam tests on $160{\times}290{\times}2200mm$ RC beams were conducted to investigate the effect of local damage on the flexural strength and ductility index. And also, blast resistance of RC beams strengthened with steel fiber and FRP sheet were evaluated by these tests. The standoff detonation tests were performed with charge weight of 1kg and standoff distance of 0.1m. After the tests, crater diameters and loss weights of specimens were measured to evaluate the local damage of specimens. Flexural strength and ductility index were measured by conducting the static beam tests on the damaged and undamaged specimens. As a test results, normal concrete specimen(NC) showed relatively large crater and spall diameters that caused weight loss of 23.5kg as a local damage. Whereas, steel fiber reinforced concrete specimen(SFRC) and FRP sheet retrofitted specimens(NC-F, NC-FS) showed higher blast resistance than NC by reducing crater size and weight loss. Flexural strength and ductility index were decreased in case of local damaged specimens by detonation. Especially, large decrease of flexural strength was shown in NC as compared with intact specimen and brittle failure was occurred due to buckling of compressive reinforcement. In case of specimens strengthened with steel fiber and FRP sheet, residual flexural strength and ductility index were increased as compared with NC. In these results, it is concluded that critical local damage can be occurred unless enough standoff distance can be assured even if the charge weight is small. and it is verified that strengthening method using steel fiber and FRP sheet can increase blast resistance.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2006.03a
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• pp.358-365
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• 2006

In this study, fragility curves of continuous buried pipelines subjected to transverse PGD (permanent ground deformation) due to liquefaction are proposed. For the waterworks system, continuos buried pipelines made of ductile iron, poly ethylene, and poly vinyl chloride are analyzed and fragility curves are drawn. Fragility curves are based on the repetitive analyses results and formulated with the dominant factors of behaviour of buried pipeline. With the use of fragility curves, engineers can estimate the status of damage of buried pipeline without overall knowledge of relevant features. Especially, fragility curves proposed in this study will act as a major module of earthquake loss estimation method. Moreover, critical value of magnitude and width of transverse PGD (by which the full damage status of buried pipelines are induced) are estimated. With the use of regression curves of these values, pre evaluation of seismic safety of buried pipelines located within liquefaction hazardous region will be possible.

• Magazine of the Korea Concrete Institute
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• v.7 no.2
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• pp.117-125
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• 1995

In this study, the damage to a concrete br~dge pier due to flre caused by the fall of an oil truck were investigated by the use of FEM and by tensile tests for reinfortements. And thtse results were analyzed and compared with the measured values. In the FEM calculations, the selected variable was the fire temperature $T_a=500-800^{\circ}C$. The fixed values were the heat transition coefficient ${\alpha}=2000W/m^2{\cdot}K$. the initial temperature of concrete $T_0=5{\circ}C$ and the fire duration t=30 minutes. As the results obtained from numerical calculations, the property darrlage zone ap,)eared to be 1.5-4.1cm and the structure damage zone appeared to be 8.7- 10.1cm from the concrete surface. And this results give values very similar to those measured, nanlelv 2-4cm and 8~10cm respectively. The results frorn tensile tests give no serious loss of the tensile strength.

• Journal of The Korean Society of Agricultural Engineers
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• v.55 no.6
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• pp.145-154
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• 2013

Recently, damage occurrence by wind erosion has been increasing in society. In times past, such problems only took place in desert area ; however, in recent years, the wind erosion problem is spreading out to agricultural land. Wind erosion in agricultural land can cause loss of loam soils, the disturbance of the photosynthesis of the crop fields and serious economic losses. To overcome the mentioned problems, installation of windbreak fence can be recommended which function as disturbing strong wind and wind erosion. However, there is still no proper guideline to install the windbreak fence and the installation used to rely on the intuition of the workers due to the lack of related studies. Therefore, this study measured the aerodynamic resistance of screens of the windbreak fence using the apparatus for testing screens. The apparatus for testing screens was designed to measure pressure loss around the screen. Measured pressure loss by wall friction compensated for pressure loss to calculate the aerodynamic resistance of screens. The result of pressure loss by regression analysis derived the aerodynamic coefficient of Darcy-Forchheimer equation and power law equation. The aerodynamic resistance was constant regardless of the overlapped shape when the screen was overlapped into several layers. Increasing the number of layers of the screen, internal resistance increased significantly more, and pressure loss caused by the screen also increased linearly when the wind speed was certain conditions, but permeability had no tendency. In the future, the results of this study will be applied to the computational fluid dynamics simulation. The simulation models will be also validated in advance by wind tunnel experiments. It will provide standard of a design for constructing windbreak fence.

• Korean journal of applied entomology
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• v.31 no.2
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• pp.174-181
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• 1992

Early, mid, and late maturing soybean varieties were artificially infested with larvae of Delia platura at seeding, and then later development and productivity of soybeans were studied. In addition, in hope to utilize as possible tactics in the management of D. platura in soybeans, cultural factors such as contents of organic matter in soil, soil types, and the use of plastic mulching on the degree of damage to soybean plants by D. platura were examined. Primary leaf damage by the larva delayed the forthcoming vegetative growth but not the blooming which is initiated by the change in day length. Degree of delay in growth was more severe where leaf damage was induced by insect infestation than where artificially excised, apparently owing to simultaneous damage in stems and roots besides primary leaves. Productivity of soybeans also dropped significantly in plants with 25 % or more loss in the primary leaf area by the larva. Both transparent and black plastic mulchings shortened the period from seeding to emergence of soybean thus reducing the chance of possible attack by the larva. Soybean seedlings grown in clay loam or clay were attacked less by the larva than those in other types of soil. High organic matter content in the soil enhanced speed of emergence resulting in less larval damage to the seedling.

• Earthquakes and Structures
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• v.18 no.2
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• pp.249-261
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• 2020

Seismic loss estimation studies require fragility curves which are usually derived using ground motion datasets. Ground motion records can be either in the form of recorded or simulated time histories compatible with regional seismicity. The main purpose of this study is to investigate the use of alternative ground motion datasets (simulated and real) on the fragility curves. Simulated dataset is prepared considering regional seismicity parameters corresponding to Erzincan using the stochastic finite-fault technique. In addition, regionally compatible records are chosen from the NGA-West2 ground motion database to form the real dataset. The paper additionally studies the effects of hazard variability and two different fragility curve derivation approaches on the generated fragility curves. As the final step for verification purposes, damage states estimated for the fragility curves derived using alternative approaches are compared with the observed damage levels from the 1992 Erzincan (Turkey) earthquake (Mw=6.6). In order to accomplish all these steps, a set of representative masonry buildings from Erzincan region are analyzed using simplified structural models. The results reveal that regionally simulated ground motions can be used alternatively in fragility analyses and damage estimation studies.

• Journal of the Korean Geotechnical Society
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• v.20 no.2
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• pp.47-58
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• 2004

Steel Pipelines were located in hillside and mountain areas where landslides occurred during the Northridge earthquake. This paper describes the investigations that were performed to identify and locate the different types of steel pipeline construction in the system using GIS (Geographical Information System). The paper explores the damage correlations of steel pipelines with PGV (peak ground velocity) and investigates the areas subjected to the landslide effects during the Northridge earthquake. One noticeable finding is that the repair rates for steel distribution pipelines after the Northridge earthquake are higher than those of CI (cast iron) pipelines. The relatively high susceptibility of steel piping to damage during the Northridge earthquake may be explained in part by utility practices, such as using steel pipe for the highest internal pressures, and increased susceptibility to corrosion also appears to play a role in steel pipeline performance.