• Journal of the Earthquake Engineering Society of Korea
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• v.14 no.6
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• pp.11-21
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• 2010

This study presents seismic responses of 5-story reinforced concrete structures retrofitted with the buckling-restrained braces using a time-dependent element. The time-dependent element having birth and death times can freely be activated within the user defined time intervals during the time history analysis. The buckling-restrained brace that showed the largest energy dissipation capacity among the test specimens in previous research was used for retrofitting the RC buildings in this study. It was assumed that the first story of the damaged building under the first earthquake was retrofitted with the buckling-restrained braces considered as the time-dependent element before the second of the successive earthquakes occurs. Under this assumption, this paper compares seismic responses of the RC structures with the time-dependent element subjected to the successive earthquake. Subjected to the second earthquake, it was observed that activation of the BRB systems largely decreases deformation of the moment frame where the damage was concentrated under the first earthquake. However, damages to the shear wall systems were increased after activation of the BRB systems. Since the cumulative damages of the shear wall systems were infinitesimal compared with the retrofit effect of the moment frame, the BRB system was effective under the successive earthquake.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.26 no.5
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• pp.335-342
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• 2013

Since the seriousness of environmental pollution came to the fore recently, various efforts have been made globally for the reduction of the environmental load. In particular, in the field of construction, an industry responsible for a considerable amount of pollution, studies have been actively conducted to reduce $CO_2$ emissions and energy consumption. However, most conventional research about pollution as it relates to construction is focused on the maintenance stages where $CO_2$ emissions are the greatest. Research related to the design stage is in its infancy, as it has only been conducted thus far on steel buildings and RC buildings. In fact, in order to achieve environmentally friendly construction considering the Life Cycle Assessment(LCA), the building design should be derived to reduce the $CO_2$ emissions from the early building design stage, and structural engineers should be able to suggest a design plan considering its environmental friendliness. In this study, optimal structural design method for steel reinforced concrete(SRC) columns considering $CO_2$ emissions is presented. The trends of $CO_2$ emissions in SRC columns according to the variations of steel shapes, concrete strengths and loads are investigated.

• Journal of the Korea Concrete Institute
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• v.19 no.4
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• pp.515-525
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• 2007

In this investigation, results of laboratory tests on four reinforced concrete flat plate interior connections with elongated rectangular column support which has been used widely in tall residential buildings are presented. The purpose of this study is to evaluate an effect of column aspect ratio (${\beta}_c={c_1}/{c_2}$=side length ratio of column section in the direction of lateral loading $(c_1)$ to the direction of perpendicular to $c_1$) on the hysteretic behavior under earthquake type loading. The aspect ratio of column section was taken as $0.5{\sim}3\;(c_1/c_2=1/2,\;1/1,\;2/1,\;3/1)$ and the column perimeter was held constant at 1200mm in order to achieve nominal vertical shear strength $(V_c)$ uniformly. Other design parameters such as flexural reinforcement ratio $(\rho)$ of the slab and concrete strength$(f_{ck})$ was kept constant as ${\rho}=1.0%$ and $f_{ck}=40MPa$, respectively. Gravity shear load $(V_g)$ was applied by 30 percent of nominal vertical shear strength $(0.3V_o)$ of the specimen. Experimental observations on punching failure pattern, peak lateral-load and story drift ratio at punching failure, stiffness degradation and energy dissipation in the hysteresis loop, and steel and concrete strain distributions near the column support were examined and discussed in accordance with different column aspect ratio. Eccentric shear stress model of ACI 318-05 was evaluated with experimental results. A fraction of transferring moment by shear and flexure in the design code was analyzed based on the test results.

• Journal of the Korea institute for structural maintenance and inspection
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• v.19 no.1
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• pp.23-34
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• 2015

Recently a new damper system with Kogome truss structure was developed and its mechanical properties were verified based on the laboratory test. This paper presents a Kagome truss damper external connection method for seismic strengthening of RC frame structural system. The Kagome external connection method, proposed in this study, consisted of building structure, Kagome damper and support system. The method is capable of reducing earthquake energy on the basis of the dynamic interaction between external support and building structures using Kagome damper. The pseudo-dynamic test, designed using a existing RC frame apartment for pilot application of LH corporation, was carried out in order to verify the seismic strengthening effects of the proposed method in terms of the maximum load carrying capacity and response ductility. Test results revealed that the proposed Kagome damper method installed in RC frame enhanced conspicuously the strength and displacement capacities, and the method can resist markedly under the large scaled earthquake intensity level.

• Journal of the Korea institute for structural maintenance and inspection
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• v.22 no.1
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• pp.137-146
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• 2018

On September 12, 2016, the Gyeongju District was strongly shaken with M=5.8, which was the largest one since measured by the actual seismometer in Korea, and some buildings were damaged. The field survey of reinforced concrete school buildings in the affected area was carried out, and their residual seismic capacities(R) were estimated based on the Japanese Standard for post-earthquake damage evaluation. In this study, the M school, which was greatly damaged by the 2016 Gyeongju Earthquake, was selected, and its damage level was evaluated on the basis of the Japanese Standard. The seismic capacity of the M school was also evaluated using the nonlinear dynamic analysis, and relationships between its damage level and seismic capacity was also conducted to investigate causes of earthquake damage. The damage level of M school was classified into light with R=88.2%. The result of the dynamic analysis agreed reasonably well with the damage of M school sustained by the 2016 Gyeongju earthquake. This will provide fundamental data for earthquake preparedness measures, such as the seismic rehabilitation of low-rise reinforced concrete buildings in Korea.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.22 no.4
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• pp.355-362
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• 2009

Many of residential buildings, which have pilotis in lower stories to meet the architectural needs, are recently constructed in Korea. Usually, infill walls located in the upper stories of these buildings may cause a soft first story, which is very weak from the earthquake resistance. In the design of the buildings, the infill walls of upper stories are usually considered as non-structural elements and thus they are not included in the analytical model. However, the infill walls may affect the seismic behavior of the residential buildings. Therefore, the differences in seismic behaviors of RC buildings with and without masonry infill walls are required to be investigated. In this study, seismic fragility analyses were performed for masonry infilled low-rise RC moment-resisting frames. And seismic behaviors of RC moment-resisting frame with/without masonry infill walls were evaluated. Two types of structural system with the same frame and different allocation of infill walls are used to evaluate the influence of masonry infill walls on seismic behavior of RC moment-resisting frames. The infill walls were modeled as bi-equivalent diagonal struts. The fragility analyses show that the seismic performance of RC moment-resisting frames with soft story is below the desirable building seismic performance level recommended by current seismic codes, indicating high vulnerability of RC moment-resisting frames with soft story.

• Fashion & Textile Research Journal
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• v.1 no.2
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• pp.173-181
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• 1999

The purpose of this study was to investigate actual sleeping environments in Ondol rooms depending on the season. The experiment was performed on five healthy women. The bedroom environments using Ondol were measured in five cases (three apartments and two houses). The environments in bedroom, bedding temperature, skin temperature and thermal sensation were measured continuously through the seven days for each season in real life. This data of sleeping environments were analyzed in the view of seasonal variations and housing types. Annual average bedroom temperatures: $26.2{\sim}31.0^{\circ}C$ in apartments, $15.7{\sim}33.6^{\circ}C$ in houses. Annual average bedroom humidity: 48.3~82.1% RH in apartments, 64.9~87.0% RH in houses. During sleeping, temperatures of contact surfaces like sheets and under quilts ranged between $30.5^{\circ}C$ and $34.1^{\circ}C$ regardless of season or housing type. Annual average rectal temperature was $36.8^{\circ}C$ with no significant difference in season or housing type. In the point of thermal sensation, neutral temperature of the bedroom was $25.9^{\circ}C$ in apartments and $20.3^{\circ}C$ in houses. It was concluded that in spite of thermal environmental variations according to the seasons, skin, bedding and bedroom temperatures in apartments were better and more stable than those of houses. It is regarded that while houses are brick structured, apartments are steel-frame structured. Due to better insulation and air tightness, apartments were affected less from outdoor temperature and maintained higher room temperature than houses.