• Proceedings of the Korea Concrete Institute Conference
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• 1993.04a
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• pp.59-64
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• 1993

The flexural and horizontal shear behavior of overlaid concrete slabs is investigated in the present study. An experimental program was set up and several series of overlaid concrete slabs have been tested to study the effect of different surface preparation ; and dowels between old slab and overlay under service load. The present study indicates that the overlaid concrete slabs behave integrally with existing bottom slabs up to yield range for rough and doweled joints.

• Proceedings of the Korea Concrete Institute Conference
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• 1998.04a
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• pp.385-390
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• 1998

Non-destructive field tests of the concrete has achieved increasing acceptance for the evaluation of existing concrete structures. As two major testing methods, this paper recommends the proper empirical relationship between the rebound number together with the ultrasonic pulse velocity and the core strength to fit the old concrete bridges in Korea.

• 재활복지
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• v.21 no.3
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• pp.187-207
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• 2017

The purpose of this study was to explore the characteristics of defining concrete and abstract nouns for the elderly. A total of 382 elderly participated in this study and they were classified into four age groups (i.e., over 55 to under 64, over 65 to under 74, over 75 to under 84, and over 85 year-old group). They performed the word definition task, composed of five concrete and five abstract nouns. The total scores and numbers and ratio of core/supplementary meanings were compared among four elderly groups. The frequency and ratio of error types were also examined. The results showed that all four groups had statistically significant differences in total scores, numbers and ratio of core and supplementary meaning of concrete noun definition task. In addition, abstract noun definition performances revealed group differences except the two groups (over 75 to under 84 and over 85-year-old group). The oldest group showed a sharp increase in error production. The highest ratio of error types were personal experience in over 55 to under 64-year-old group, and over 65 to under 74 year-old groups; and for the target word repetition in over 75 to under 84 year-old group; and no response in over 85 year-old group. In conclusion, both concrete and abstract word defining abilities had age-related deterioration. This decline results from impairment in spreading semantic knowledge within semantic network, which is vulnerable to aging. Characteristics of word definition for elderly can provide basic information to understand various neurolinguistic disorders associated with age.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.05a
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• pp.859-864
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• 2003

In these days, the deterioration of bridges make it necessary for decks to be replaced and it is inevitable to apply the precast decks to minimize the traffic control induced from the deck placement. This precast deck construction makes the physically discontinuous interface between old and new concrete. Usually, the adhesive force at this interface are ignored. However, for crack behavior and reliable long term behavior, it is required to evaluate the exact value of the cohesive force at the interface. This research investigates the cohesive characteristics at the interface. Four different interface surface conditions are tested and three different methods are used to measure the cohesive strength at the interface. In addition, cohesive characteristic at the surface between precast panels are investigated with different interface surface conditions.

• Proceedings of the KSR Conference
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• 2007.05a
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• pp.1050-1055
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• 2007

In the case of a rail road bridge extension work, especially single track to double track, the foundation of new substructure which supports the extended part of superstructure could be interfered by the exist foundation of an old bridge. When these two foundations are jointed to prevent such fatal effects of the structure as unequal subsidence of soil foundations, it is important to prove the structural behaviour of the joining surfaces between new foundation and old foundation. 3-Dimensional Finite Element Analysis Method have been studied for the solutions of the structural behaviour of the foundations. In this analysis, 'Contact Element' which allows the sliding of each adjoining member is used for the joint of the boundary surface of the old and new pier foundations. Furthermore, Material Nonlinear Behaviour Analysis also supports the accuracy of the result in this study because the foundations consist of concrete main bodies and reinforced steel bars. These detailed analyses secure the verification of the structural safety of the foundations in the extension work more firmly.

• Korean Journal of Child Studies
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• v.38 no.1
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• pp.117-126
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• 2017

Objective: The purpose of this study was to investigate young children's nonsymbolic magnitude comparison ability according to ratio limit and task condition. Methods: The participants included 40 3-year-old children, 42 4-year-old children, and 41 5-year-old children recruited from 4 childcare centers located in Seoul, Korea. All magnitude comparison tasks were composed of image material tasks and concrete material tasks. In addition, each magnitude comparison task varied with the ratio of the two quantities; 0.5 ratio, 0.67 ratio, 0.75 ratio. Results and Conclusion: The results revealed that 3-, 4-, and 5-year-old children could perform nonsymbolic magnitude comparison tasks without learning experiences. Also, 3-, 4-, and 5-year-old children could perform concrete material tasks better than image material tasks in nonsymbolic magnitude comparison tasks. Furthermore, children's performance on nonsymbolic magnitude comparison tasks indicated the ratio signature of the approximate number system. Children have a degree of numerical capacity prior to formal mathematics instruction. Also, children were influenced by task conditions or sense stimulus when they processed numerical information. Furthermore, the approximate number system can be used in understanding the ordinality of number.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2014.05a
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• pp.122-123
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• 2014

Measurement of the strength of concrete is an important indicator of the safety of the fresh as well as old concrete structures. It is possible to evaluate the strength of the concrete by means of an ultrasonic velocity method which is a kind of non-destructive inspection method for safety diagnostic evaluation of the building structures with aging. Steel embedded in the concrete and age of the concrete may affect ultrasonic pulse velocity. In order to accurately assess the strength of the concrete, it is necessary to understand rebar embedded in the concrete, steel shapes in various forms which effect ultrasonic pulse velocity. In this study, by measuring the velocity of ultrasonic waves generated when the waves pass through the ultrasonic pulse in a direction perpendicular to the reinforcing bars embedded in concrete, the effect of reinforcing bars on ultrasonic velocity accurately was verified and used to estimate the strength of the concrete.

• Proceedings of the Korean Geotechical Society Conference
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• 2000.03b
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• pp.449-456
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• 2000

Remediation grouting has been widely used for the rehabilitation of various civil works like hydraulic and traffic structures. Recently there were some cases of remediation grouting for repairing old dams in korea. So this study will describe the case of remediation grouting of the concrete dam base located east-northern part of Seoul. We use Lugeon Test and Borehole Image Processing System(BIPS) for estimating the effectiveness of remediation grouting of this project. As the results of this study, we could find the lots of joints between the old concrete body and the weathered rock base. So the about 30% quantity of total cement grouts was injected at the boundary surface between concrete and rock base. And Lugeon Test and BIPS could be compared relatively because BIPS results could be presented quantitatively as well as qualitative analysis. Finally, we could find microfine cement was very effectively injected to the fine fissured concrete body compared with ordinary portland cement, but there was little injectability differences beteween microfine cement and ordinary portland cement at the large cracks or cavities were developed rock base.

• Proceedings of the Korea Concrete Institute Conference
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• 1993.04a
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• pp.188-193
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• 1993

In widening of existing bridges, construction joints between old new parts of concrete slabs are subjected to repeated traffic loads during placing and curing of concrete. Therefore, the main focus of this paper is given to examine several construction methods of bridge widening. As a result, the occurrence of cracks in vibrating specimen is faster than non-vibrating one, but the difference between flexural strength and ultimate moment was negligible. Also, it shows the same result in other construction method, say direct and non-shrinkage joint specimen.

• Proceedings of the Korea Concrete Institute Conference
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• 1999.10a
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• pp.655-658
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• 1999

An experimental investigation on the ruined RC bridge with 30 years old has been conducted to estimate the durabilities. The ruined RC bridge estimated in this study was located at Kyung-Bu Express Way. First, concrete strength and durability characteristics such as concrete resistivity, chloride content were estimated. Second, it was to test reinforcing corrosion embedded in slab of bridge. And, third, tensile strength and yield strength of reinforcing bar corroded and not corroded were estimated. This bridge inspection provides the most common cause of defects and deterioration and the results of this inspections give more specific information than those of laboratory inspections do.