• Journal of the Korea Concrete Institute
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• v.19 no.6
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• pp.701-706
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• 2007

This study evaluated the durability of high-performance shotcrete mixed in the proper proportions using alkali-free and cement mineral accelerators as a permanent support that maintains its strength for the long term. Durability tests were performed the chloride permeability, repeated freezing and thawing, accelerated carbonation, and the effects of salt environments. Test results showed that all the shotcrete mixes included silica fume had low permeability. In addition, after 300 freeze/thaw cycles, the shotcrete mix had excellent freeze/thaw resistance more than the 85% relative dynamic modulus of elasticity. The accelerated carbonation test results were no effect of accelerator type but, the depth of carbonation was greater in the shotcrete mix containing silica fume. No damage was seen in a salt environments. Therefore, the high performance shotcrete mix proportions used in this study showed excellent durability.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.1D
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• pp.35-43
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• 2008

This paper mainly deals with the performance evaluation of 33 asphalt sections of Korea Expressway Corporation Test Road (KECTR) during the past four years. Since the construction of the KECTR in December 2002, key performance indicators of asphalt pavements have been collected five times with an Automatic Road Analyzer (ARAN), and have been analyzed for permanent deformation, surface distress, and road roughness. Linear viscoelastic characteristics of four dense graded HMAs used in KECTR were investigated with a series of complex modulus test. The effect of air void in HMAs on dynamic modulus was investigate at two air void contents for a surface course HMA (19 mm Nominal Maximum Size of Aggregate). Layer densification due to traffic was estimated from air void contents of field cored samples, and was correlated with pavement distresses and performances. One of findings of this study was that both permanent deformation and cracking were suspectible to pavement temperatures, rather than traffic. However, it was found that road roughness was mostly affected by traffic loading.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.1D
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• pp.73-79
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• 2006

A major purpose of this study is to develop high modulus asphalt mixtures for perpetual asphalt pavements which can save maintenance cost by increasing the design and performance periods of the pavements. Various physical and mechanical laboratory tests are performed for the high modulus asphalt binder developed in this study. The test results show that the properties of the high modulus binder are similar to those of the French high modulus binders. In addition to the binder tests, various performance tests are conducted for the high modulus and conventional mixtures. The dynamic modulus test results indicate that the dynamic modulus values of the high modulus mixtures are higher than those of the conventional mixtures by 10~15% at $5^{\circ}C$, 20~25% at $15^{\circ}C$ and 100% at $30^{\circ}C$. It is observed from the performance tests that the high modulus mixtures yield better fatigue, rutting and moisture damage performance than the conventional mixtures.

• Korean Journal of Agricultural Science
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• v.25 no.2
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• pp.271-277
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• 1998

This study was performed to evaluate the stress-strain properties of surlightweight polymer concrete using synthetic lightweight aggregates. The following conclusions were drawn; 1. The dynamic modulus of elasticity was in the range of $1.514{\times}10^5{\sim}1.916{\times}10^5kgf/cm^2$, which was approximately 48~96% of that of the normal cement concrete. It was showed larger with the decrease of synthetic lightweight fine aggregate. 2. The static modulus of elasticity was in the range of $2.552{\times}10^4{\sim}4.386{\times}10^4kgf/cm^2$, which was showed lower compared to that of the normal cement concrete. The poisson's number of surlightweight polymer concrete was less than that of the normal cement concrete. 3. The stress-strain curves of surlightweight polymer concrete were showed smaller with the increase of expanded clay.

• The Journal of the Acoustical Society of Korea
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• v.42 no.6
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• pp.594-602
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• 2023

To date, research on heavy floor impact noise has mainly been conducted. The reason is that in the case of lightweight floor impact noise, sufficient performance could be secured with only the floating floor structure and floor finishing materials. In the case of heavy floor impact noise in a floating floor structure, the reduction performance can be predicted to some extent by measuring the dynamic elasticity of the floor cushioning material. However, with the recent introduction of the post-measurement system, various floor structures are being developed. In particular, many non-floating floor structures that do not use cushioning materials are being developed. In floor structures where cushioning materials are not used, the finishing material will have a significant impact on lightweight floor impact noise. However, research on floor finishing materials is currently lacking. In this study, as a basic research on the development of various floor finishing materials for effective reduction of lightweight floor impact noise, various materials used as floor finishing materials for apartment complexes were selected, the sound insulation performance of lightweight floor impact noise was measured in an actual laboratory, and vibration characteristics were identified through simple experiments. The purpose was to confirm the predictability of light floor impact noise.

• Journal of the Korean Recycled Construction Resources Institute
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• v.4 no.1
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• pp.96-100
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• 2009

The properties of recycled fine aggregates which had different source concrete were examined by mortar test. With higher strength of source concrete, specific gravity of recycled fine aggregate was higher and absorption of recycled fine aggregate was lower due to reduction of the volume of adhered cement paste. The compressive strength and flexible strength of mortar with recycled fine aggregate were affected by the interface boundary of new mortar and the strength of adhered mortar. Strength development of mortar with recycled fine aggregate reduced because recycled fine aggregate become a porous material with the smaller strength of source concrete. The drying shrinkage of mortar was about$800{\sim}2000{\mu}m/m$. It was about 1.5 times than that of mortar with natural fine aggregate. Relative dynamic modulus of elasticity was a similar level with that of mortar with natural fine aggregate.

• Journal of the Korean Society for Railway
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• v.14 no.4
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• pp.383-389
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• 2011

Until now, in planning and constructing KTX and the Express Way, the connectivity and transfer between these facilities have not been considered. In this study the effect of mode choice behavior by connecting KTX and the Express Way is analyzed through estimating Multinomial Logit Model and Binary Logit Model. The SP and RP surveys to develop these models were carried out and the data were selected from the passengers using the KTX station, Express Bus Terminals and Rest Areas in the Express Way. To test the effect of connectivity and transfer in the field, the case study for Dongtan KTX station was carried out. According to the results, connecting the KTX station and the Express Way has the effect of increasing the demand by 30%. And this is caused by saving about 120 minutes of traveling time from Seoul to Pusan. This study shows that the connectivity and transfer can increase the efficiency of transportation system and the improvement in the mobility and accessibility will maximize the usages of these two facilities.

• Journal of the Korean Recycled Construction Resources Institute
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• v.6 no.4
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• pp.319-323
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• 2018

Ferronickel slag is a by-product from the ferronickel smelting process and it is divided into air-cooled ferronickel slag and water granulated ferronickel slag according to cooling system. The purpose of this experimental resesrch is to investigate the mechanical properties and resistance to freezing and thawing of concrete using air-cooled ferronickel slag(ACFNS) fine aggregate. For this purpose, the concrete specimens with water-cement ratio of 50% were made with ACFNS's replacement ratios of 0%, 20%, 30%, 40%, 50%, 70%, and 100% by volume of fine aggregate. It was observed from the test results that the compressive strength and static modulus of elasticity of ACFNS fine aggregate concrete were increased with increasing replacement ratio of ACFNS and the resistance to freezing and thawing of this was similar to reference concrete which had the relative dynamic modulus of elasticity of more than 90% during the freezing and thawing of 300 cycles.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.11a
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• pp.445-450
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• 2001

The paper investigates the relationships between dynamic elastic modulus and static elastic modulus or compressive strength according to curing temperature, aging, and cement type. Based on this investigation, the new model equations are proposed. Impact echo method estimates the resonant frequency of specimens and uniaxial compression test measures the static elastic modulus and compressive strength. Type I and V cement concretes, which have the water-cement ratios of 0.40 and 0.50, are cured under the isothermal curing temperature of 10, 23, and 50 $^{\circ}C$. Cement type and aging have no large influence on the relationship between dynamic and static elastic modulus, but the ratio of dynamic and static elastic modulus comes close to 1 as temperature increases. Initial chord elastic modulus, which is calculated at lower strain level of stress-strain curve, has the similar value to dynamic elastic modulus. The relationship between dynamic elastic modulus and compressive strength has the same tendency as the relationship between dynamic and static elastic modulus. The proposed relationship equations between dynamic elastic modulus and static elastic modulus or compressive strength properly estimates the variation of relationships according to cement type, temperature, and aging.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.12
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• pp.3109-3117
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• 1994

To operate a flexible mechanism in high speed its weight must be reduced as far as the structural strength does not decrease too much, but a light-weighted mechanism causes undesirable elastodynamic responses deteriorating the system performance. Besides, clearance within the connections of mechanisms causes rapid wear, increased noise and vibration. Even if the problems described above must be considered in the initial design stage, there has been no effective design process which takes account of the correlation between dynamic characteristics of flexible mechanism and the clearance effect at the joint. In this study, the generalized elastodynamic governing equations which include dynamic characteristics and boundary conditions of flexible mechanism are derived by variational calculus and solved by using FFM theory. To take the clearance effect at joint into account a new dynamic model is presented and also the method of modified stiffness/damping matrix is proposed to activate the dynamic clearance model, which cooperates with the developed governing equation very easily. As the results of this study, the proposed method(modified stiffness/damping matrix) to calculate clearance effect was proved to be superior to the existing one(force reaction method) in solution convergency and calculation performance. Besides this method can be easily adopted to the complex shape joint without calculation of reaction force direction.