• International Journal of Highway Engineering
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• v.19 no.1
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• pp.11-19
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• 2017

PURPOSES : The purpose of this study is to verify the property of self-healing, and to propose an appropriate duration for wet curing of bridge deck concrete overlays. METHODS : In this study, reinforced bars were inserted into concrete molds in order to prevent brittle fracture and induced cracks in the concrete resulting from indirect tension mode. The induced time of concrete cracking was 3 to 7 days, following which the concrete specimens were cured in water. The resulting concrete crack width was measured using image analysis equipment. Additionally, the self-healing tests were performed using the following three mixtures: OPC, SFC, and LMC. RESULTS : Concrete mixtures with crack widths of $150{\mu}m$ or lower were completely healed by Day 28. Hydrates of crack fills were found to be the calcium carbonate. CONCLUSIONS : The cement-based mixtures exhibit properties of self-healing. Considering these properties, it is necessary to increase the curing duration of concrete overlays for bridge decks.

• Journal of the Korea Concrete Institute
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• v.12 no.6
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• pp.13-22
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• 2000

In order to resolve the problem of increasing traffic entailed by the economic development, road system is reorganization and new highways are built, and long span bridges over 40m are being constructed in environmental and aesthetic considerations. Most long span bridges that are currently being constructed are in general steel box girder and preflex girder bridges; however these types of breiges are less efficiency than PSC I-type girder bridges in terms of construction cost and maintenance. Therefore, in these study, structural efficiency of PSC I-type girders based on section parameters, concrete compressive strength and other design parameter is observed to develope new PSC I-type girder for long span bridges. As a results of analysis, most important design parameters that control the stress of the girder are found to be the top flange width and the height of girder. In this light, the relationship between the two variables is determined and cross-section details of the girder that most appropriates for the long span bridges are proposed. The use of high strength concrete appears to increase the general design span however the increase rate of the span from increasing concrete ultimate strength appears to be reduced depending on the span. Also, the optimal girder spacing is determined through the parameter studies of design span using the proposed girder.

• Journal of Biosystems Engineering
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• v.42 no.1
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• pp.12-22
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• 2017

Purpose: This aim of this study was to develop a pick-up type pulse crop harvester for harvesting cut and dried pulse crop. Methods: The pick-up type pulse crop harvester was designed and constructed. Its specifications and operating performance were investigated. Results: Compared with conventional bean harvesters, the pick-up type pulse crop harvester adopted seven rows of chains with tines to pick-up the cut and dried pulse crop on a flat or ridged field, two transverse threshing drums with steel wire teeth to reduce the threshing speed, and a tilt plate and plastic bucket elevator for conveying clean grain to reduce damage. The threshing speed and the oscillating frequency of the separating and cleaning parts according to crop type and condition could be varied easily to efficiently use engine power and to improve harvesting performance. The harvester showed forward speed ranges of 0 ~ 1.5 m/s during harvesting operation, and 0 ~ 2.5 m/s during road travelling. The pick-up width of the harvester was about 1 m. Conclusions: The pick-up type self-propelled 51.5 kW harvester was designed and constructed to harvest cut and dried pulse crop. The effective field capacity of the harvester was predicted as above 40 a/h.

• Journal of Korean Society of Water and Wastewater
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• v.25 no.2
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• pp.141-152
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• 2011

In this study, we extracted effective factors of pipe burst from the status data of water asset, operating data of pressure, volume and etc. and 7 years' pipe burst and repair records. The extracted factors were sorted by each attribution and then a statistical analysis was performed to generate a pipe burst probability function using the logistic regression model. As the result, material, diameter, length, laying year, pressure and road width affected to pipe burst significantly. Especially, in case of small diameter, laying year was most effective factor and in case of steel pipe, external loading was main cause of burst, and in case of cast iron, PE, PC, HP pipes, the deterioration of joint was main cause. The other side, as a result of Hosmer-Lemeshow goodness of fit test the models are turned out significant statistically. Also the classification criteria were determined to minimize the total cost from classification errors, when the predicted probability was more than 18% this pipe could have a chance of burst.

• International Journal of Highway Engineering
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• v.15 no.2
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• pp.121-129
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• 2013

PURPOSES : This study deals with the traffic accidents of rotary in Korea. The objective of this study is to develop the accident models by age group based on the various data of rotaries. METHODS : In pursuing the above, this study gives particular attentions to classifying the accident data of 17 rotaries by age, collecting the data of geometric structure, traffic volume and others, and developing the models using SPSS 17.0 and EXCEL. RESULTS : First, 3 multiple linear regression models which were all statistically significant were developed. The value of model of under 30-49 age group were, however, evaluated to be 0.688 and be less than those of other models. Second, the most powerful variables were analyzed to be traffic volume in the model of under 30 age group, circulatory roadway width in the model of 30-49 age group, and the number of approach lane in the model of above 50 age group. Finally, the test results of accident models using RMSE were all evaluated to be fitted to the given data. CONCLUSIONS : This study propose install streetlights, speed humps and widen Circulatory as effective improvements for reduction of accident in rotary.

• Journal of The Korean Digital Architecture Interior Association
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• v.10 no.1
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• pp.65-74
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• 2010

This study has been given careful consideration to an induction of the mixed-use districts for the efficiency of Land Use, the rational plot planning and the mixture/complex among the functions in order to complement the zoning plan with the primary purpose to purify the usage of landscape. Furthermore, it is aimed to indicate the implementations through the medium of the in-depth analysis about the cardinal factors such as the standards on the regional location, building size and building uses in the case of designating the Mixed-use districts.Abstract This study has been examined by the aspect of scope for securing the adequacy of Site Division Restriction, Floor Area Ratio, Building Coverage Ratio and Outdoor Area Ratio in the "Mixed-Use Districts" and especially, by the medium of the in-depth analysis about the actual condition of building and outdoor space scales. It has been deduced the scale standards by using the simulation and correlation analysis among the factors of those buildings and outdoor spaces. Moreover, it has been applied the analysis method of using the building scale, especially, the latter has analyzed the total 1,656 different types classified by 3 patterns of Plottage and Building Coverage Ratio, 9 patterns of the factor change on Outdoor Area Ratio and 8 different patterns of road width.

• Journal of the Korean housing association
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• v.19 no.6
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• pp.85-93
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• 2008

This study analyzes areas, traffic lines and characteristics of block of traditional villages in order to suggest how to build urban village in the way that can solve problems occurring in residential areas these days. The study showed the following results: 1) Traditional villages have definite boundary and entrance, and the community area for the villages is close to the entrance to encourage community activities of villagers. 2) With an access in the form of a blind alley branched from the main road, traditional villages form a small-sized clustering and encourage community activities in a natural way. 3) Formed of block with a pattern of net, blind alley or standing in a line on both sides, traditional villages help residents to form close relations between. These findings suggest that for building desirable urban villages, 1) they should have definite boundary, 2) size and location of community area should be determined in the way to activate community activities of residents, 3) roads inside the village should have branched form rather than standardized check pattern so that small-sized clustering could be formed along the branched inner roads, and 4) clustering in villages should be arranged in a line on both sides or in the form of a blind alley giving consideration to the length and width of roads. The roads should be also of a closed type so that residents could create strong bonds with their neighbors.

• Wind and Structures
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• v.14 no.1
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• pp.55-70
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• 2011

This study investigates the design criteria required for wind barriers to protect vehicles running on an expressway under a high side wind. At the first stage of this study, the lateral deviations of vehicles in crosswinds were computed from the commercial software, CarSim and TruckSim, and the critical wind speeds for a car accident were then evaluated from a predefined car accident index. The critical wind speeds for driving stability were found to be 35 m/s for a small passenger car, yet 30 m/s for a truck and a bus. From the wind tunnel tests, the minimum height of a wind barrier required to reduce the wind speed by 50% was found to be 12.5% of the road width. In the case of parallel bridges, the placement of two edge wind barriers plus one wind barrier at center was recommended for a separation distance larger than 20 m (four lanes) and 10 m (six lanes) respectively, otherwise two wind barriers were recommended.

• Proceedings of the KSME Conference
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• 2001.06b
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• pp.676-681
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• 2001

ABS is a safety device, which adds hydraulic system to the existing brake system to prevent wheel from locking, so we can obtain maximum braking force on driving. The hydraulic system to control braking pressure consists of sol-flow type using solenoid valve, flow control valve or consists of sol-sol type using two solenoid valve. In this paper, the hydraulic system in ABS is composed of sol type using a 3port-2position solenoid valve, and vehicle system is composed of 1/4 vehicle model. And slip ratio is controlled using PWM (Pulse-Width-Modulation) control algorithm. Braking friction coefficient and tracking friction coefficient which are described by slip ratio's function have maximum value when slip ratio has its value from 0.1 to 0.3. And slip ratio is controlled constantly in this boundary value even in the variation of road's condition in some boundary.

• Journal of the Korean Institute of Rural Architecture
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• v.12 no.1
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• pp.1-8
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• 2010

The purpose of this study was to explore the factors affecting satisfaction of street-scape. According to this purpose, in chapter 2, by inspecting conservation of street environment and streetscape, deduce the frame for analyzing streetscape in commercial district. In chapter 3, analyzing present condition and problems of selected streets in Pohang City, derive the primary factors to induce desirable streetscape through problems and their reason between the analyzed elements of building form. Analyzed elements are composed pavement of road, street furniture, height of buildings, color and material of building and outdoor advertisements, etc. In chapter 4, by conducting a questionnaire survey of pedestrians about street images and the preference, propose the direction of improvement about streetscape in commercial district. As the study method, level of satisfaction was analyzed using the components of street-scape. The collected data was analyzed through Reliability Analysis, ANOVA, Factor Analysis, Regression Analysis. A regression analysis for deriving main factors affecting the satisfaction level of street-scape showed that signboard, sign color, width of street, paving materials, street furniture, open space were found to be the most important.