• Computers and Concrete
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• v.19 no.2
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• pp.211-216
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• 2017

Crack on concrete surface allows more rapid penetration of chlorides. Crack width and depth are dominant parameters for chloride behavior, however their effects on chloride penetration are difficult to quantify. In the present work, the previous anisotropic (1-D) model on chloride diffusion in concrete with single crack is improved considering crack shape and roughness. In the previous model, parallel-piped shape was adopted for crack shape in steady-state condition. The previous model with single crack is improved considering wedge shape of crack profile and roughness. For verifying the proposed model, concrete samples for nuclear power plant are prepared and various crack widths are induced 0.0 to 1.2 mm. The chloride diffusion coefficients in steady-state condition are evaluated and compared with simulation results. The proposed model which can handle crack shape and roughness factor is evaluated to decrease chloride diffusion and can provide more reasonable results due to reduced area of crack profile. The roughness effect on diffusion is evaluated to be 10-20% of reduction in chloride diffusion.

• Geomechanics and Engineering
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• v.27 no.6
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• pp.573-582
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• 2021

From the effect of bound water, this study aims to seek the potential reasons for difference of mechanical experiment results of subgrades soils. To attain the comparatively test condition of bound water, dry forming (DF) and wet forming (WF) were used in the specimen forming process before testing, series of laboratory tests, i.e., CBR tests, direct shear tests and compaction tests. The measured optimal moisture contents, maximum dry densities, CBR, cohesion c, and internal friction angle 𝜑 were given contrastive analysis. Then to detect the adsorptive bound water in the subgrade soils, the thermal gravimetric and differential scanning calorimetry (TG-DSC) test were employed under different heating rates. The free water, loosely bound water and tightly bound water in soils were qualitatively and quantitatively analyzed. It was found that due to the different dehydration mechanics, the lost bound water in DF and WF process show their own characteristics. This may lead to the different mechanical properties of tested soils. The clayey particles have a great influence on the bound water adsorbed ability of subgrade soils. The more the clay content, the greater the difference of mechanical properties tested between the two forming methods. Moreover, in highway construction of southern China, the wet forming method is recommended for its higher authenticity in simulating the subgrade filed humidity.

• Journal of Drive and Control
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• v.20 no.4
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• pp.80-91
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• 2023

The purpose of this study is to suggest the direction for the development of intelligent agricultural machinery technology in the Republic of Korea. For this purpose, intelligent technology of agricultural machinery was divided into autonomous agricultural machinery and tractor-implement intelligent communication technology. Then, a survey and analysis of a previous study of the Republic of Korea and foreign countries were conducted. GNSS-based autonomous driving technology is still widely used worldwide, and recently, as research on camera and LiDAR-based autonomous driving is actively progressing, autonomous driving technology is becoming more advanced. ISOBUS-based technology is being developed worldwide for intelligent control of tractor-attached implements, and major global agricultural machinery manufacturers are actively applying it to their products. However, although some ISOBUS technologies are being researched in the Republic of Korea, there are no cases of application on agricultural machinery yet. Therefore, to be globally competitive in the agricultural machinery manufacturing industry, there is an urgent need to advance autonomous driving technology and commercialize agricultural machinery using ISOBUS technology.

• Journal of Families and Better Life
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• v.33 no.4
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• pp.83-104
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• 2015

The purpose of this study is to provide diverse points of view to understand the low fertility issue of Korean society. For this phenomenological qualitative study, in-depth interviews were conducted with 14 married couples(28 persons) all raising three children. Participants were asked about overall family and work life, child care role performance, thoughts about child rearing, and their sociocultural context. Interview data were explored based on 6 analyzing steps offered by S, J, Talyor and R. Bogdan(1984). Most participants of this study were formed positive perceptions about having three children. Parents' positive perception was closely related with their attitude of not worrying too much about their children's future as well as child caring contexts around them. Parents' perception about having three children was also linked with their child care role construction process. In detail, parents with more positive perceptions tended to increase their level of child care involvement. This was particularly true for fathers. Mother and father's job situation emerged as an important factor to shape their child care involvement. In addition, child care attitude of people around them explained father's child care involvement. Applying these qualitative results, we first expect to provide detailed ideas about lives with three children in Korea. Second, based on our study findings, a more realistic and helpful policy to help the low fertility problem could be developed. Lastly, we also hope to provide helpful phenomenological qualitative research about low fertility issues of Korea.

• Journal of the Korean Recycled Construction Resources Institute
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• v.9 no.1
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• pp.58-65
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• 2021

In this study, as a method to increase the recycling of circulating fluidized bed combustion ash(CFBCA), CFBCA was utilized to produce autoclave aerated concrete product since CFBCA contains quicklime and calcium sulfate components that are required for the manufacture of autoclave aerated concrete. Successful achievement of such objective will bring cost reduction with high value addition, saving of natural resources, and the reduction of environmental load. Various mixing designs were designed to evaluate the properties of autoclave aerated concrete made of CFBCA. Based on series of experimental program, prototypes mix design for factory manufacturing was obtained. According to the experimental results, it was confirmed that gypsum can be replaced with CFBCA through the method of pre-treating the CFBCA as a slurry. It was possible to produce competitive autoclave aerated concrete products using CFBCA.

• Computers and Concrete
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• v.33 no.5
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• pp.595-603
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• 2024

In the construction industry, there has been a surge in the implementation of high-tech equipment in recent years. Various technologies are being considered as potential solutions for future construction projects. Building information modeling (BIM), which utilizes advanced equipment, is a promising solution among these technologies. The need for safety inspection has also increased with the aging structures. Nevertheless, traditional safety inspection technology falls short of meeting this demand as it heavily relies on the subjective opinions of workers. This inadequacy highlights the need for advancements in existing maintenance technology. Research on building safety inspection using 3D laser scanners has notably increased. Laser scanners that use light detection and ranging (LiDAR) can quickly and accurately acquire producing information, which can be realized through reverse engineering by modeling point cloud data. This study introduces an innovative evaluation system for building safety using a 3D laser scanner. The system was used to assess the safety of an existing three-story building by implementing a reverse engineering technique. The 3D digital data are obtained from the scanner to detect defects and deflections in and outside the building and to create an as-built BIM. Subsequently, the as-built structural model of the building was generated using the reverse engineering approach and used for structural analysis. The acquired information, including deformations and dimensions, is compared with the expected values to evaluate the effectiveness of the proposed technique.

• Journal of the Korea Concrete Institute
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• v.20 no.6
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• pp.747-754
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• 2008

In this study, high strength concrete corbels reinforced with steel fibers and polypropylene fibers, and subjected to the vertical and horizontal loads were constructed and tested. The results showed that performance in terms of load carrying capacities, stiffness, ductility, crack width, and number of cracks was improved, as the steel fibers and polypropylene fibers were added. The polypropylene fiber reinforced concrete corbels resulted in higher ductility in presence of horizontal loads, but showed larger crack width than the steel fiber reinforced concrete corbels. And, the heads of the headed bars provided excellent end anchorage of the main tension tie reinforcement. Experimental results presented in this paper are also compared with various prediction models proposed by codes and researchers. The refined strut-and-tie model showed more accurate and conservative predictions in presence of horizontal loads, and the truss model proposed by Fattuhi provides fairly good predictions for fiber reinforced concrete corbels.

• Korean Journal of Construction Engineering and Management
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• v.9 no.2
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• pp.159-169
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• 2008

Recently, domestic construction projects Have become more high-rised, bigger, sophisticated, so necessity of logistics and progress management through application of various management theories has also been increased and development of IT technologies like RFID can help to improve management method, although the existing logistics and progress management studies are applied only to single progress or important material. It is a basic research for integrated framework for logistics and progress management. An analysis on the characteristics of RFID tech was performed for major materials or components of each work item in office building projects. This paper will make foundation of integrated framework for logistics and progress management in construction project, utilizing RFID technology by analysing materials type like materials which can be chased and measured, materials which can be chased and measured by certain methodologies, materials which can be chased and measured by future technologies, materials which are difficult to be chased and measured. So we can effectively control logistics and progress management, appling the optimum RFID technology to each construction project, and we need to study out solution in order to overcome RFID technology limitation through development of specification counterproposal about delicate materials of the RFID technology application.

• Korean Journal of Construction Engineering and Management
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• v.15 no.4
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• pp.86-94
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• 2014

Since the late 1990s, mixed-use apartment, armed with high qualities and large scales with a high ratio of TFA(Total Floor Area) have been continuously provided accommodating exclusive community facilities along with high-tech securities, not to mention excellent skyline view. However, especially in mid-small cities, there have been only a few supplies. As a result, none of the mixed-use housing provided by high-end brands has ever been built in non-metropolitan area. But constructors couldn't plan the projects which aims to build the mixed-use apartment in local city, because they couldn't get the basic data or advanced research for feasibility analysis. Therefore, to suggest the useful price for mixed-use apartment supply project of local city, the PSM(Price Sensitivity Method) widely used for determining the price preferences as a market research tools has been applied. As analysis results, the estimated price of mixed-use apartment is 10.8% higher than general apartment, and mixed-use apartment has lower price sensitivity than general apartment. As price determinants, the age, education level and family size influence on UTP in significant level. It is expected that these research findings can be applied for establishing the solid marketing strategy of mixed-use apartment development project in local city.

• Journal of the Korea Concrete Institute
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• v.19 no.2
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• pp.209-216
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• 2007

This study reports on the structural characteristics of slab-column connections using fiber-reinforced ultra-high-strength concrete (UHSC). Compression tests were performed on two slab-column and four isolated column specimens. In the column load tests, slab loads were also applied on the slab-column specimens so that the actual confinement condition at the slab-column joint was considered. The main parameter investigated was the "puddling" of fiber-reinforced UHSC. This paper also investigates the effects of some parameters, such as confinement of slab concrete, steel fibers, and concrete strength of the joint, related to the ability of the slab-column specimens and isolated column specimens without the surrounding slab to transmit axial loads from the UHSC columns through slab-column connections. Furthermore, the ACI Code (2005) and the CSA Standard (2004) are compared to the experimental results. The beneficial effects of the puddling of fiber-reinforced UHSC on the transmission of column loads through slab-column connections are demonstrated.