• Journal of the Korea Concrete Institute
• /
• v.29 no.3
• /
• pp.249-257
• /
• 2017

The purpose of this study was to contribute to the field application cost effectively and reasonably by developing the functional piles that make up for the defects of PHC piles. CFP (Concrete Filled Pretensioned Spun High Strength Concrete Pile with Ring type Composite shear connectors) piles developed in this study increases the compressive stress through enlarged cross section by rearranging composite shear connectors and filling the hollow part of PHC pile with concrete. And it improved shear and bending performance placing the rebar (H13-8ea) within the PHC pile and the hollow part of PHC pile of rebar (H19-8ea). In addition, the composite shear connectors were placed for the composite behavior between PHC pile and filled concrete. Placing Rebars (H13-8ea) of PHC pile into composite shear connector holes are sleeve-type mechanical coupling method that filling the concrete to the gap of the two members. Nonlinear finite element analyzes were performed to verify the performance of shear and bending moments and it deduced the spacing of the composite shear connectors. Through a various interpretation of CFP piles, it's proved that the CFP pile can increase the shear and bending stiffness of the PHC pile effectively. Therefore, this can be utilized usefully on the construction sites.

• The Journal of The Korea Institute of Intelligent Transport Systems
• /
• v.15 no.5
• /
• pp.20-28
• /
• 2016

A Ubiquitous City (U-city, Smart City) is one that ties information communications technologies (ICT) into many facets of city construction, thereby implicitly intending to function as a smart city that aims to be efficiently managed as well as provide an enhanced standard of living for its residents. Laws related to the construction of such ubiquitous cities point to integrated city management centers, intelligent facilities, and U-City infrastructure, among others, as central components of U-Cities, but do not provide a standard for these structures. Consequently, building of U-Cities by local governments are based on arbitrary judgments constrained the myriad of practical limitations that they face. Such ambiguity brings to light the need to find ways to improve the quality of these efforts. The first and second stages of this research examine the status of the components of a U-City -ubiquitous planning, technology, infrastructure, and services - and undertakes a comprehensive review thereof, with evaluation criteria formulated on the characteristics of stability, connectivity, goal-orientation, and development potential. In the research's third stage, a realistic and detailed evaluation index by which U-Cities can be renewed, demonstrated, and applied (???) is introduced in a step-by-step fashion, which will allow for local governments to properly assess the standard of their U-City in relation to the realities of the locality. Through the research result, it is expected that the index will become a part of the continued development and advancement of the "smart" character of an autonomous U-City at the local scale, and contribute to the overall revitalization of the U-City.

• Journal of the Korean Geographical Society
• /
• v.50 no.1
• /
• pp.73-90
• /
• 2015

This article focuses on geo-institutional differentiation and a multi-scalar analysis of emerging capitalist development in Laos. It discusses the impact of the Greater Mekong Subregion on new institutional economic and economic geographical arrangements. It demonstrates the usefulness of the varieties of Asian capitalism approach. The rubber industry was chosen to unravel emerging but various sub-national institutional arrangements linked to higher scale levels. Rubber is a growing agribusiness industry throughout the country, led by the insatiable demand from China. Overall, this study shows that the capitalist development of the rubber industry features much geo-institutional differentiation, due to the different strategies of Chinese, Thai and Vietnamese investors. Since Laos is still in transition from a state-led economy to something else, it is impossible at this to identify the exact number capitalisms. Yet, the evidence on rubber clearly lays bare the presence of multiple institutional arrangements. Without more inclusiveness, however, the implications for regional development are worrying. Exclusive arrangements will most likely lead to more uneven regional development and higher regional inequality. To refine theories on sub-national varieties of capitalism in developing countries it is instructive to consider more explicitly the notion of regional personal capitalisms and the complex interplay between national and regional states and relationships between capital accumulation and livelihood analyses.

• The Journal of the Korea Contents Association
• /
• v.11 no.3
• /
• pp.26-35
• /
• 2011

In these days, internet environment are very quickly development as well on-line service have been using a online for the mission critical business around the world. As the amount of information to be processed by computers has recently been increased there has been cluster computing systems developed by connecting workstations server using high speed networks for high availability. but cluster computing technology are limited for a lot of IT resources. So, grid computing is an expanded technology of distributed computing technology to use low-cost and high-performance computing power in various fields. Although the purpose of Grid computing focuses on large-scale resource sharing, innovative applications, and in some case, high-performance orientation, it has been used as conventional distributed computing environment like clustered computer until now because grid middleware does not have common sharable information system. In order to use grid computing environment efficiently which consists of various grid middleware, it is necessary to have application-independent information system which can share information description and services, and expand them easily. This paper proposed new database architecture and load balancing for high availability through Grid technology.

• Tunnel and Underground Space
• /
• v.14 no.1
• /
• pp.54-68
• /
• 2004

In this study, scaled model tests were performed on blasting demolition of reinforced concrete structures and the experimental results were analyzed in comparison with the results of numerical analysis. The tests were designed to induce a progressive collapse, and physical properties of the scaled model were determined using scale factors obtained ken dimension analysis. The scaled model structure was made of a mixture of plaster, sand and water at the ratio determined to yield the best scaled-down strength. Lead wire was used as a substitute for reinforcing bars. The scaled length was at the ratio of 1/10. Selecting the material and scaled factors was aimed at obtaining appropriately scaled-down strength. PFC2D (Particle Flow Code 2-Dimension) employing DEM (Distinct Element Method) was used for the numerical analysis. Blasting demolition of scaled 3-D plain concrete laymen structure was filmed and compared to results of numerical simulation. Despite the limits of 2-D simulation the resulting demolition behaviors were similar to each other. Based on the above experimental results in combination with bending test results of RC beam, numerical analysis was carried out to determine the blasting sequence and delay times. Scaled model test of RC structure resulted in remarkably similar collapse with the numerical results up to 900㎳ (mili-second).

• School Mathematics
• /
• v.9 no.1
• /
• pp.119-139
• /
• 2007

The purpose of this study is to analyze students' misconception in the teaming of the conic sections with the cognitive and pedagogical point of view. The conics sections is very important concept in the high school geometry. High school students approach the conic sections only with algebraic perspective or analytic geometry perspective. So they have various misconception in the conic sections. To achieve the purpose of this study, the research on the following questions is conducted: First, what types of misconceptions do the students have in the loaming of conic sections? Second, what types of errors appear in the problem-solving process related to the conic sections? With the preliminary research, the testing worksheet and the student interviews, the cause of error and the misconception of conic sections were analyzed: First, students lacked the experience in the constructing and manipulating of the conic sections. Second, students didn't link the process of constructing and the application of conic sections with the equation of tangent line of the conic sections. The conclusion of this study ls: First, students should have the experience to manipulate and construct the conic sections to understand mathematical formula instead of rote memorization. Second, as the process of mathematising about the conic sections, students should use the dynamic geometry and the process of constructing in learning conic sections. And the process of constructing should be linked with the equation of tangent line of the conic sections. Third, the mathematical misconception is not the conception to be corrected but the basic conception to be developed toward the precise one.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.22 no.1
• /
• pp.6-12
• /
• 2018

Recently, The use of the curtain wall method is increasing in construction. The curtain wall construction is widely applied to the exterior wall of the building for shortening construction period and economical efficiency. However, the replacement of deterioration of the weather resistance and structural behavior of the sealing material connecting the curtain wall method and the glass frame is necessary for introduction of the stable curtain wall method and quality improvement in accordance with KS F 4910 standard. In this study, the elastic restoring force test was performed in the external environment. In this study, the deterioration of the sealant was evaluated for structural sealants. In Korea, studies on the variable displacement behavior of structural sealants are lacked. In this study, the reproduced results in laboratory conditions are compared with the deteriorating conditions exposed to the external environment, and they are reflected in the design of sealing materials in the future. According to the results of the study, it was confirmed that the existing structure sealant meets the quality standard of KS F 4910, but in the conditions performed in this study, adhesion failure of the specimen and cracking of the surface occurred. Especially, in the weather resistance test, it is necessary to evaluate the long-term durability performance of the structural sealant used in the curtain wall method by checking the insoluble state of all the test pieces. Therefore, in order to apply a conventional structural sealant to the site, it is necessary to introduce another durability performance evaluation.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.21 no.6
• /
• pp.147-161
• /
• 2017

Generally, significant amount of reinforcements are used in nuclear power plant structures and it may cause several potential problems during the construction. In particular, it is more difficult to pour concrete into structural member joint area than other areas because of the significant congestion of the joint area due to a lot of hooked bars, embedded materials, and other reinforcements. The purpose of this study is to solve these problems due to the reinforcement congestion by using the high-strength(ASTM A615 Gr.80) headed deformed bars of large-sized diameter(43 mm & 57 mm) in nuclear power plant structures as a alternative of standard hooked bars. In order to use headed deformed bars effectively, It is necessary to find the method how to relax limits on their use while maintaining or improving the anchorage capacity. Therefore, this study will analyze the results of tests planned to evaluate the influence of the restricted variables, such as bar size, yield strength, clear cover thickness.

• Journal of the Korean Geosynthetics Society
• /
• v.12 no.3
• /
• pp.15-22
• /
• 2013

By changing from ballasted track to concrete slab track, new type railroad subgrade is strongly required to satisfy strict regulations for displacement limitations of concrete slab track. In this study, sensitivity analysis was performed to assess the design characteristics of new type reinforced railroad subgrade, which could minimize residual settlement after track construction and maintain its function as a permanent railway roadbed under large cyclic load. With developed design program, the safety analysis (circular slip failure, overturning, and sliding) and the evaluation of internal forces developed in structural members (wall and reinforcement) were performed according to vertical installation spacing and stiffness of short and long geotextile reinforcement. Based on this study, we could evaluate the applicabilities of 0.4 H short geogrid length with 0.4 m vertical installation spacing of geotextile as reinforcement and what the ground conditions are for the reinforced railroad subgrade. And also, we could grasp design characteristics of the reinforced railroad subgrade, such as the importance of connecting structure between wall and reinforcement, boundary conditions allowing displacement at wall ends to minimize maximum bending moment of wall.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.13 no.3
• /
• pp.11-19
• /
• 2009

Recently, concerns relating to the maintenance of large structures have been increased. In addition, the number of large structures that need to be evaluated for their structural safety due to natural disasters and structural deterioration has been rapidly increasing. It is common for the structural characteristics of an older large structure to differ from the characteristics in the initial design stage, and changes in dynamic characteristics may result from a reduction in stiffness due to cracks on the materials. The process of deterioration of such structures enables the detection of damaged locations, as well as a quantitative evaluation. One of the typical measuring instruments used for the monitoring of bridges and buildings is the dynamic measurement system. Conventional dynamic measurement systems require considerable cabling to facilitate a direct connection between sensor and DAQ logger. For this reason, a method of measuring structural responses from a remote distance without the mounted sensors is needed. In terms of non-contact methods that are applicable to dynamic response measurement, the methods using the doppler effect of a laser or a GPS are commonly used. However, such methods could not be generally applied to bridge structures because of their costs and inaccuracies. Alternatively, a method using a visual image can be economical as well as feasible for measuring vibration signals of inaccessible bridge structures and extracting their dynamic characteristics. Many studies have been conducted using camera visual signals instead of conventional mounted sensors. However, these studies have been focused on measuring displacement response by an image processing technique after recording a position of the target mounted on the structure, in which the number of measurement targets may be limited. Therefore, in this study, a model experiment was carried out to verify the measurement algorithm for measuring multi-point displacement responses by using a DIC (Digital Image Correlation) technique.