• International Journal of Highway Engineering
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• v.13 no.4
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• pp.187-198
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• 2011

Researches on children's traffic behavior have only focused on traffic accidents and the number of accidents, and therefore it's been impossible to deal with more broad field of study. In this research we can review the possibility of traffic accidents of children and provide them with traffic education. The goal of this research is to develop a device for measuring possibility of children in terms of traffic behavior. Around 600 elementary students of two schools involved in the pretest with 259 questions and about 3,500 students(junior level 53 questions & senior level 72 questions) involved in practical test. At the result of the research, junior level extracted 4 factors(Lack of behavioral control, Aggressive, Self-regulation, Impulsive Instinct) and 44 questions, and senior level extracted 4 factors(Lack of behavioral control, Depression, Sense-oriented, Aggressive) and 69 questions. We take the gender consideration in separate the groups whether the group has traffic behavioral problem or not. In these series of research, we got the standard score such as junior male student, 63 & female student, 50 and senior male student, 110 & female student, 99.

• International Journal of Highway Engineering
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• v.13 no.4
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• pp.103-115
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• 2011

Concrete slab curls and warps due to the uneven distribution of temperature and moisture and as the result, internal stress develops within the slab. Therefore, environmental loads must be considered in addition to the traffic loads to predict the lifespan of the concrete pavement more accurately. The strength of the concrete slab is gradually decreases to a certain level at which fatigue cracking is generated by the repetitive traffic and environmental loadings. In this study, a new fatigue regression model was developed based on the results from previously performed studies. To verify the model, another laboratory flexural fatigue test program which was not used in the model development, was conducted and compared with the predictions of other existing models. Each fatigue model was applied to analysis logic of cumulative fatigue damage of concrete pavement developed in the study. The sensitivity of cumulative fatigue damage calculated by each model was analyzed for the design factors such as slab thickness, joint spacing, complex modulus of subgrade reaction and the load transfer at joints. As the result, the model developed in this study could reflect environmental loading more reasonably by improving other existing models which consider R, minimum/maximum stress ratio.

• International Journal of Highway Engineering
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• v.9 no.2 s.32
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• pp.13-25
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• 2007

Viscosity, adhesion and cohesion of asphalt binder are very important characteristics in asphalt pavement. However, these characteristics can cause some problems such as inaccurate amount of asphalt mixture, reduction of asphalt content and loss of workability during asphalt pavement construction. Asphalt release agent has been used to solve these problems. Diesel oil and vegetable oil are generally used as an asphalt release agent in Korea. However, these agents have been criticized from environmental and binder integrity reasons. Therefore, this study evaluated the characteristics of asphalt release agents including diesel oil, vegetable oil and two emulsion type oils. From the study, it was found that the diesel oil resolved the binder within ten minutes and vegetable oil stripped the binder from mixture within one hour after contacting with asphalt mixture. And also, from the test for estimating the application cycle of asphalt release agent, it appears that diesel oil and vegetable oil should be applied to construction equipments every time in their uses. However, diesel oil and vegetable oil showed a good performance as a lubricant for detaching the asphalt mixtures from the truck bed.

• Journal of the Korean Geotechnical Society
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• v.32 no.12
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• pp.23-32
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• 2016

A single particle crushing test was carried out for recycled aggregates from waste concrete while demolishing various structures. When the recycled aggregates were used for backfill or road subbase materials, load-displacement and crushing characteristics were analyzed. The recycled aggregates with hydrates and aggregates were sorted into 40 mm size (75-40 mm) and 20 mm size (40-20 mm). At initial loading, their irregular surface was closed to and then crushed by loading plate. Such first crushing stage was called 'Surface crushing'. Further loading, some hydrate was crushed and detached from aggregate, and such process repeated several times. This state is called 'hydrate crushing'. The final state is called 'aggregate crushing' in which aggregate crushed and following load suddenly dropped down. As the load increased, such crushing cycle is repeated several times. The shapes of aggregates are round or square, and triangle or long shaped. Depending on their shapes and surface conditions, they crushed in different ways. The 63% of aggregates showed more than 50% load reduction due to aggregate crushing. The 90% load reduction occurred at 15% of aggregates. The 40 mm aggregate crushed at maximum load between 3.05-4.38 kN and 70% of crushed aggregates were less than 20 mm.

• International Journal of Highway Engineering
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• v.3 no.4 s.10
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• pp.127-136
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• 2001

To increase the structural integrity of concrete box culvert good compaction by the dynamic compaction roller with bi9 capacity is as effective as good backfill materials. It is needed for effective compaction that a compaction roller closes to concrete structure with high frequency. However structural distress of the culvert could be occur due to the excessive earth pressure by great dynamic compaction load. To investigate the characteristics of Induced stress by compaction, a box culvert was constructed with changing cushion materials and compaction methods. Two types of cushion material such as tire rubber chip and EPS(Expanded Polystyrene) were used as cushion panels and they are set on the culverts before backfill construction. Laboratory test result of cushion material says that the value of dynamic elastic modulus of rubber is lesser than that of EPS. On the other hand, material damping of rubber material is greater than that of EPS. In most case, dynamic compaction rollers with 10.5 ton weights were used and vibration frequency was applied 30Hz for the great compaction energy. This paper presents the main results on the characteristics of dynamic earth pressures during compaction. The amounts of induced dynamic pressures$(\Delta\sigma\;h)$ by compaction are affected with construction condition such as compaction frequency, depth of pressure cell, distance between roller and the wall of culvert and roller direction. Based on the measured values dynamic lateral pressure on the culverts, it could be said that orthogonal direction of roller to the length of culvert is more effective to compaction efficiency than parallel direction.

• International Journal of Highway Engineering
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• v.3 no.4 s.10
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• pp.93-103
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• 2001

This study focused on the field applicability evaluation of SB latex-modified concrete (LMC) for concrete bridge deck overlay using mobile mixer. The main experimental factors were water-cement ratio(31, 33, 35 37%), latex contents(0, 5, 10, 15, 20%), and fine aggregate ratio(55, 56, 57, 58%) in order to evaluate the workability, mechanical properties, and durability property of LMC. The slump loss, air content, compressive and flexible strength tests were used to evaluate LMC workability and strength properties. Also, the rapid chloride permeability test was used to evaluate the relative permeability of LMC. As a results, the LMC with enough workability and good quality was produced when it was mixed in field using mobile mixer, satisfying the target compressive strength and flexural strength. The required water-cement ratio of LMC for same workability when mixing with mobile mixer was less than that when mixing in laboratory. Increasing the amount of latex produced concrete with increased flexural strength by mobile mixer. The required cement-water ratios for same initial $19{\pm}3cm$ slump were 37% and 33% at laboratory and mobile mixer, respectively. The mobile mixer was accurately calibrated satisfying the required specification.

• Journal of Korean Society of Transportation
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• v.33 no.1
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• pp.70-80
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• 2015

In recent years, tram has been the focus of a new mode of public transportation that can solve traffic jams and decrease public transit usage and environmental problem. This research is in the works to develop a tram signal controller and signal control strategies, and aim to resolve the problem of what could happen if a tram system was installed in general road. We developed the hierarchical signal control strategies to obtain a minimum tram bandwidth and to minimize vehicle delay, in order to perform a priority control to include passive and active signal priority control strategies. The strategies was produced for S/W and H/W, it is based in standard traffic signal controller. We conducted a micro simulation test to evaluate the hierarchical signal control strategies, which showed that the developed optimization model is effective to prevent a tram's stop in intersection, to reduce a tram's travel time and vehicle's delay.

• Journal of agricultural medicine and community health
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• v.37 no.2
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• pp.76-83
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• 2012

Objectives: The purpose of this study was to define the underserved emergency medical services (EMS) areas in Daejeon metropolitan city, as well as to identify their distinctive characteristics in public health perspectives. Methods: An underserved EMS area was operationally defined as an area in which it is difficult to arrive at an emergency medical center within 30 minutes. Using a cost-weighted distance algorithm with a geographic information system (GIS), the underserved EMS area was calculated. The characteristics of the underserved areas were analyzed by the Chi-square test. The SPSS statistical software package was used to perform the statistical analysis. All statistical tests were two-sided, and a p-value<0.05 was considered statistically significant. Results: Twelve administrative sectors ('Dong' in Korean) were included in the underserved areas, accounting for a population of approximately 8,100 citizens. The relationships between underserved EMS area and populations of agriculture, fishery, and forestry; citizens who are recipients of national basic livelihood security program; disabled; or aged 65 or older were statistically significant. Conclusion: It was found that 12 administrative sectors were included in the underserved EMS areas. Revealing underserved EMS areas using GIS analysis based on a cost-weighted distance algorithm of road data was an effective analytic method. However, as this study was confined to Daejeon City, South Korea, a nation-wide study should be performed to provide a more accurate conclusion.

• Journal of the Korea Concrete Institute
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• v.24 no.5
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• pp.543-551
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• 2012

Road pavements in Korea generally show shorter service life than the predicted one. There are many reasons for this phenomenon including increased traffic load and other attacks from exposure conditions. In order to extend a service life and upgrade the pavement, a new multi-functional composite pavement system is being developed in Korea. This study is to investigate the performances of fiber-reinforced lean concrete for pavement base. This study considered mineral admixtures of fly ash and reject ash. The reject ash is defined as ash that does not meet the specifications for fly ash so that it cannot be used as a supplemental material for cement replacement. Due to the inherent property of lean concrete, compaction during the fabrication of specimens is a key factor. Therefore, this study suggests an appropriate compaction method. From the test results, the compressive strengths of the concrete satisfied the required limit of 5 MPa at 7 days. When a compaction roller was used to mimic actual field conditions, the strength development seemed to be influenced by the compaction energy rather than hydration of cement itself.

• Journal of Korean Tunnelling and Underground Space Association
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• v.22 no.5
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• pp.563-574
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• 2020

Currently, road tunnels and railroad tunnels are building smoke control systems to emit toxic gases and smoke from fires. Among the various smoke control systems, the transverse smoke control system has the disadvantage that air supply or exhaust is performed on only half of the cross-section, rather than air supply or exhaust on the entire cross-section of the tunnel as air is supplied or exhausted by partitioning the wind path. Therefore, this study analyzed the effect of exhaustion through numerical analysis and scaled model tests on the zoning smoke control system, which improved the limitations of the transverse smoke control system. As a result of the scaled model test, the transverse ventilation system exhibited a 25.6% smoke control rate based on the state where no smoke was controled, and zoning smoke control system showed a smoke control rate of 40.8%. In addition, as a result of numerical analysis, it was found that transverse ventilation system did not control fire smoke spreading from the tunnel and continued to spread. On the other hand, zoning smoke control system was found to be smoke controled within a certain section due to the air curtain effect and the flue gas effect.