• Journal of Korean Society of Steel Construction
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• v.29 no.2
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• pp.147-158
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• 2017

The present study focused on the structural performance of newly developed prefabricated composite columns (PSRC composite column) using bolt-connected steel angles. Concentric axial loading tests were performed for four 2/3 scaled PSRC column specimens and two conventional SRC column specimens. The test parameters were the spacing and sectional configurations of lateral reinforcement, and width-to-thickness ratio of steel angles. The test results showed that the axial load-carrying capacity and deformation capacity of the PSRC column specimens were comparable to those of the conventional SRC column specimens. Closely spaced steel plates and Z-shaped steel plates for lateral reinforcement increased the deformation capacity of the PSRC column specimens. The load-carrying capacity was greater than the prediction by current design codes. Numerical analysis was performed for the specimens. The results agreed well with the test results in terms of initial stiffness, load-carrying capacity, except for strength degradation due to cover concrete spalling.

• Journal of the Korean Society of Radiology
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• v.12 no.4
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• pp.525-532
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• 2018

This study is filmed by applying the axial angle variation of the X-ray tube instead of the patient's position change during the perimetric examination of the ribs. A Reference image with the rib oblique examination using a chest phantom and experimental images applied with a six-phase variation in the axial angle by increasing $5^{\circ}$ tube angle each from $5^{\circ}{\sim}30^{\circ}$ from the vertical incident direction of the chest phantom to the right horizontal axis were obtained. For the quantitative comparative evaluation of the images, SNR and CNR were calculated for regions of interest in the experimental images based on the reference image. Also, the left-right rib ratio in the reference image and the left-right rib ratio in the experimental images are measured and compared. As a result of the study, the experimental images with a tube angle of $25^{\circ}$ were best shown in the measurements of the SNR, CNR and left-right rib ratio compared to the reference image with a standard examination method. The modified rib examinations will consider useful, if it is difficult to maintain the patient's examination position.

• Journal of Korean Society of Steel Construction
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• v.22 no.4
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• pp.325-334
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• 2010

In this study, an unbraced five-story steel-framed structure was designed in accordance with KBC2005 to understand the features of structural behavior for the arrangement of semi-rigid connections. A pushover analysis of the structural models was performed, wherein all the connections were idealized as fully rigid and semi-rigid. Additionally, horizontal and vertical arrangements of the semi-rigid connection were adopted for the models. A fiber model was utilized for the moment-curvature relationship of the steel beam and the column, and a three-parameter power model was adopted for the moment-rotation angle of the semi-rigid connection. The top displacement, base-shear force, required ductility for the connection, sequence of the plastic hinge, and design factors such as the overstrength factor, ductility factor, and response modification coefficient were investigated using the pushover analysis of a 2D structure subjected to the equivalent static lateral force of KBC2005. The partial arrangement of the semi-rigid connection was found to have secured higher strength and lateral stiffness than that of the A-Semi frame, and greater ductility than the A-Rigid frame. The TSD connection was found suitable for use for economy and safety in the sample structure.

• Journal of the Korean Geotechnical Society
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• v.27 no.3
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• pp.85-94
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• 2011

Mixtures of sand and rubber particles ($D_{sand}/D_{rubber}=1$) are investigated to explore their characteristics under different stain level. Mixtures are prepared with different volumetric sand fractions ($sf=V_{sand}/V_{total}$). Experimental data are gathered from a resonant column, an instrumented oedometer, and a direct shear tests. Results show that sand and rubber differently control the behavior of the whole mixture with strain level. Non-linear degradation of small strain stiffness is observed for the mixtures with $sf{\geq}0.4$, while the mixtures with low sand fraction ($sf{\leq}0.2$) show significantly high elastic threshold strain. Vertical stress-deformation increases dramatically when the rubber particle works as a member of force chain. The strength of the mixtures increases as the content of rubber particle decreases, and contractive behavior is observed in the mixtures with $sf{\leq}0.8$. Rubber particle plays different roles with strain level in the mixture: it increases a coordination number and controls a plasticity of the mixture in small strain; it prevents a buckling of force chain in intermediate strain; it leads a contractive behavior in large strain.

• Journal of the Korean GEO-environmental Society
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• v.19 no.9
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• pp.5-12
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• 2018

The foundation of the multi-span greenhouse structures is designed with small shallow concrete foundation considering mainly the vertical load. However, recently, due to an abnormal climate such as strong wind, horizontal load and up-lift load over design strength are applied to the foundation, causing safety problems of the greenhouse foundation. In order to reasonably evaluate the safety of greenhouse foundations, rotational and pullout stiffness expressed by the ground-foundation interaction should be evaluated, which also affects the safety of the upper structural members. In this study, three representative basic foundation types were selected by classifying greenhouse standards in Korea according to the shape, and the horizontal loading tests and theoretical calculation were performed for each foundation type. As a result of the comparison and analysis of the test and calculation, it was found that rotational resistance of the foundation is different according to the ratio of the contact area between the foundation and ground when the conditions of the foundation - ground contact surface and the mechanical properties of the ground are the same.

• Journal of the Society of Disaster Information
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• v.11 no.1
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• pp.45-54
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• 2015

In the case of railway facilities in cities such as a railway station or a bridge, the significance of design for reducing vibration and noise is getting more significant. The vibration control solution is in need especially for an elevated railway station to block vibration of a train and secondary noise effectively. Even though a vertical vibration isolation device is able to be applied effectively to railway facilities such as elevated railway stations which transfer vibration directly from a train to a structure, the development of the vertical device is much slower than a horizontal vibration isolation device. In this paper, a vibration isolation device using wedge type friction material which is currently developing to reduce train-induced vibration effectively is introduced and test results for verification of dynamic performance is also presented. The vibration test on a concrete structure equipped with the developed vibration isolation device is conducted through which the isolation performance and dynamic properties are verified and needs for improving the performance of the device is identified.

• Journal of Biomedical Engineering Research
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• v.37 no.2
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• pp.90-103
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• 2016

This research was aimed to analyze load sharing ratios between cortical shell and trabecular bone of a degraded lumbar vertebra with aging, and also evaluate elastic moduli assigned into an FE model, using finite element method. For the better analysis of trabecular bone, effective elastic moduli, that is, nominal elastic moduli divided by the volumetric porosities was used. The elastic moduli of the cortical shell suitable for the trabecular bone were obtained from the equations on the basis of idealized stress-strain relations, including areal porosities. To minimize numerical errors, p-element was used. Using eight parameters that refer to some published papers, the geometry of L3 with a removed posterior part. After the constant compressive displacement was applied, the load sharing ratios were obtained by using both every elastic strain energy and every vertical force between two bones in each 8-volume. As results, 1) according to an increase in age from 20-year to 80-year, load sharing ratios of trabecular bone decreased from 55% to 49%; 2) the maximal ratios of each bone were occurred in the mid-plane of centrums and the endplate of cortical shells, respectively; 3) effective elastic moduli assigned into a porous centrum/cortex were found to be adequate; 4) for load sharing ratios, the difference of two methods showed that the total ratios were almost same within less than 1% but the partial ratios at every depth were more or less different each other.

• The Journal of Engineering Geology
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• v.8 no.1
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• pp.75-86
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• 1998

Eighteen oriented samples from the Jeongsun limestone of the Joseon Supergroup are collected. The orientations of C-axis of calcite and e twin plane, the average thickness, numbers of twins and the widths of calcite grains in 10 samples are measured. Then, the twin strain, mean width, intensity of twin and relative magnitude and orientations of principal stresses are calculated using Calcite Strain Gauge program. Twin strain, mean width and intensitv rainge between 0.801%~10.927%, $0.43{\mu\textrm{m}}~2.03{\mu\textrm{m}}$, and 33.5~113.4twim/mm, respectively. Metamorphic temperatures calculated from twin show below $70^{\circ}C$, indicating that twins were developed within 2.3km depth. In five samples, two events with different orientations of principal stress produced calcite twins, while only one event produced calcite twins in five samples. The direction of the maximum stress is almost horizontal and the minimum is almost vertical, indicating that the stress regirne is identical with thrust fault. E-W and NW-SE are the most dominant directions of comressive stress and N-S and NE-SW directions are also shown. Comparision between paleostress orientations measured in the study and others indicates that the maximum horizontal stress oriented to E-W may represent the paleostress of period either from the Silurian to the Triassic or from the Silulian to the Permian. Paleostress oriented to NW-SE may be the major direction of stress during the Daeho orogeny.

• Journal of Environmental Science International
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• v.16 no.10
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• pp.1179-1187
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• 2007

This paper represents the statistical characteristics of sources and receptors for road traffic noise in apartment complex. Also we suggested that the site-specific characteristics of vertical and horizontal distributions in the complex apartment have been derived using a different analysis for evaluating levels of Leq1h by the apartment floor at a given distance from a road in terms of the flow rate, the mean speed of the traffic, and the percentage of the type vehicles in the day and night periods. As a result, the contribution orders of traffic quantity by the type of vehicles showed as followed: light vehicle>medium vehicle>heavy vehicle>motorcycle. Especially, the mixing ratio of entering the road on the heavy vehicle in the daytime was two times higher than that of in the night. The speed in all types of vehicle is in the range of 41 and 81 km/hr and noise level was not significantly different in day and night-time. The sources of road traffic noise had different variations and uncertainties using a random variable and probability distribution. The sound distribution to receptors by the apartment floor showed S curve between 1st floor and $15^{th}$ floor With the normality test, the normal distributions using Anderson-Darling Test followed $1^{st},\;3^{th},\;13^{th}$ and $15^{th}$, floor in the daytime and all floors except $7^{th}$ floor in the night (p>0.05). And also, the value of the pearson correlation coefficient (r) obtained in this study have significantly different at the range of floor. In conclusion, the results suggested that the distribution characteristics of levels of $Leq_{1h}$ on the sources and receptors of road traffic noise in apartment complex must be improved and developed on the guideline of regulation of road traffic noise.

• Journal of the Korean Society for Railway
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• v.17 no.4
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• pp.251-259
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• 2014

The transition zone between an earthwork and a bridge effect to the vehicle's running stability because support stiffness of the roadbed is suddenly changed. The design criteria for the transition structure on ballast track were not particular in the past. However with the introduction of concrete track is introduced, it requires there is a higher performance level required because of maintenance and running stability. In this present paper, a transition structure reinforced with geosynthetics is suggested to improve the performance of existing bridge-earthwork transition structures. The suggested transition structure, in which there is reinforcing of the approach block using high-tension geosynthetics, has a structure similar to that of earth reinforced abutments. The utilized backfill materials are cement treated soil and gravel. These materials are used to reduce water intrusion into the approach block and to increase the recycling of surplus earth materials. An experiment was performed under the same conditions in order to allow a comparison of this new structure with the existing transition structure. Evaluation items are elastic displacement, cumulative settlement, and earth pressure. As for the results of the real-scale accelerated testing, the suggested transition structure has excellent performance for the reduction of earth pressure and settlement. Above all, it has high resistance the variation of the water content.