• Proceedings of the Korea Concrete Institute Conference
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• 1999.04a
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• pp.825-830
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• 1999

The purpose of this study is to improve overall performance of prefoamed lightweight cellular concrete for On-Dol system floor. This study includes 4 sections as follows. \circled1 Analysis of the structural characteristics of On-Dol System focusing on the lightweight cellular concrete insulation layer. \circled2 Establishment of the mixing design equations. \circled3 Development of some admixtures used with foaming agent. \circled4 Improvement of the equipment for onsite production. This study has proven that, compared with the current existing one, the newly developed lightweight cellular concrete has been reduced the usage of cement by 20% and the cracks caused by cement drying shrinkage up to 80% but has shown the increased compression strength by 20% at 7 days curing period. The volume contraction of freshly prepared cellular concrete by the loss of foam was hardly found in newly developed lightweight cellular concrete.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.24 no.6
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• pp.483-492
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• 2014

Uncomfortable feelings of occupants by indoor floor impact noise in a residential building are not accurately represented by the floor impact noise from a standard impact source. It is due to the characteristics of standard impact sources, which are different from the impact forces produced by occupants. It varies significantly by impact source, and it is not easy to be replicated for testing. As a result, the indoor floor impact noise under different acoustic conditions cannot be directly compared. Using frequency response function(FRF), which represents the input-output relationships of a dynamic system, it is possible to examine the characteristics of the system. Especially, FRF can predict the response of a linear dynamic system subjected to various excitation. To determine the relationship between impact force and the corresponding response of dynamic system in residential building, the acceleration response of a concrete slab and the floor impact noise in the living room, produced by bang-machine and rubber-ball excitation, were measured. The test results are compared to the estimates based on FRF and impact force spectrum.

• Structural Engineering and Mechanics
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• v.65 no.3
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• pp.349-357
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• 2018

An extensive research was undertaken to study the vibration serviceability of a long-span and light-weight floor subjected to human loading experimentally and numerically. Specifically, heel-drop test was first conducted to capture the floor's natural frequencies and damping ratios, followed by jumping and running tests to obtain the acceleration responses. In addition, numerical simulations considering walking excitation were performed to further evaluate the vibration performance of a multi-panel floor under different loading cases and walking rates. The floor is found to have a high frequency (11.67 Hz) and a low damping ratio (2.32%). The comparison of the test results with the published data from the 1997 AISC Design Guide 11 indicates that the floor exhibits satisfactory vibration perceptibility overall. The study results show that the peak acceleration is affected by the walking path, walking rate, and adjacent structure. A simpler loading case may be considered in design in place of a more complex one.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2012.05a
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• pp.279-282
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• 2012

This study attempted to the effect on the physical performance of silane coupling agent on solventless epoxy-based concrete surface finishing material for parking floor. Tests were carried out in accordance with KS F 4041 and KS F 4937. The results of compressive strength, flexural compressive are 95.6N/㎟, 25.4N/㎟ and after wheel moving load testing, average abrasive depth is 0.96mm, these results satisfied the quality standard of KS F 4041, KS F 4937. As conclusion, this study confirmed that the silane coupling agent greatly effected on the physical performance of solventless epoxy resin.

• Journal of the Korean Society for Precision Engineering
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• v.16 no.8
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• pp.38-45
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• 1999

The 2-trowel type concrete floor finishing robot can move in any direction by adjusting the posture or trowels without any wheels. Since the quality of the smoothed and polished concrete floor is determined by plastering speed, we need to control the velocity of the robot. However, we cannot use the typical motion control method because it is very difficult to measure the velocity of the robot, in contrast to the mobile robots with wheels. To overcome this difficulty, the following are studied in this paper: we found that the robot dynamics has the disturbance depending on its translational speed, and showed that there exists the saturated velocity of the robot which is set by the posture of the trowels, and obtained the relationship between the saturated velocity and the posture in the translation. The result enables us to control the motion of the robot only by adjusting the posture of trowels without measuring the velocity of the robot. Currently, we built the troweling robot and are experimenting its performance with the proposed motion control method.

• Proceedings of the Korea Concrete Institute Conference
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• 1997.04a
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• pp.676-681
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• 1997

The purpose of this study is to evaluate the thermal Conductivity and Foolr Impact Sound of Polyurethane Concretes. The Polyurethane Concretes are prepared with various resin content, Fine and Coarse aggregates content, and its thickness, and tested for the Thermal Conductivity and Impact Sound. From the test results. the sound insulation grade of polyurethane concretes by the floor impact sound test on high frequency band is L-60, and its effect is considerable Polyurethane concretes have high degree of solidity compared with other heat shield materials, and its thermal conductivity is 0.05kcal/$mh^{\cire}C$. And it is suitable for sound proof floor materials.

• Korean Journal of Veterinary Research
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• v.35 no.3
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• pp.625-630
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• 1995

During the period from june 1994 to february 1995 influence of free stall with concrete floor on profile of blood chemistry and clinico-morphopathogenesis of foot disease on 266 cows were studied. The results obtained as follow. 1. No differences between value of blood chemistry in normal and lame cows with foot disease were observed. 2. 20.7% of the cows were clinically lame. 3. Prevalence of clinical digital disorders were investigated: hyperplasia interdigitalis(45.8%), pododermatitis circumscripta(22.4%), dermatitis interdigitalis(9.4%), erosio ungulae(5.9%), phlegmona interdigitalis(3.5%), pododermatitis septica traumatica(3.5%), dermatitis digitalis(2.4%), white line disease(2.4%), pododermatitis aseptica diffusa(2.4%), dermatitis verrucosa(1.2%), fissura ungulae(1.2%) 4. Most claw lesions were located on lateral hindclaws and interdigital space of hindclaws.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.05a
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• pp.383-386
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• 2005

Low frequency heavy-weight impact noise is the most irritating noise in Korean high-rise reinforced concrete apartment buildings. This low frequency noise is generated by foot traffic due to the fact that Koreans do not wear shoes at home. The transmission of the noise is facilitated by a load bearing wall structural system without beams and columns which is used in these buildings. In order to control low frequency heavy-weight impact noise, floating floors using isolation materials such as glass-wool mat and poly-urethane mat are used. However, it was difficult to control low frequency heavy-weight impact sound using isolation material. In this study, reinforcement of concrete slab using beams and plate was conducted. Using the FEM analysis, the effect of concrete slab reinforcement using FRP(fiber-glass reinforced plastic) on the bang machine impact vibration acceleration level and sound were conducted at the standard floor impact sound test building. The $3{\sim}4dB$ floor impact vibration acceleration level and impact sound pressure level were reduced and the natural frequency of slabs were changed.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.05a
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• pp.457-462
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• 2003

It studies the non-structural crack factors that are produced in Steel Box Girder Bridge concrete floor plate using analytical method. It mainly studies humidity and design standard of concrete strength. It used MIDAS CIVIL Ver 5.4.0, a general structure analysis program that applies drying shrinkage rate of domestic road bridge design standard and standard value of creep coefficient, CEF-FIP standard equation and ACI standard equation from the aspect of creep, drying shrinkage and hydration heat to see the effect of the two factors on concrete crack and found the following result. The analytical results of this study showed that the initial stress, which was obtained by ACI standard, exceeds the allowable tensile stress between 5 to 18 days. This result means that even if a bridge is designed and constructed according to design standard, the bridge can have cracks due to various variables such as drying shrinkage, hydration heat and creep that produce stress in slab.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.05a
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• pp.387-390
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• 2005

Finite element method was applied to the vibration analysis of concrete slab system in apartment building. To save the time and cost the 2 dimensional finite element model was proposed. At first, experimental results show that sound peak components to influence the overall level and the rating of floor impact sound insulation were coincident with natural frequencies of the reinforced concrete slab. Second, there is linear relationship between the impact sound pressure level and vibration acceleration level. Third, 2 dimensional finite element model was enough to analyze the vibration analysis of floor structure system.