• Korean Journal of Environment and Ecology
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• v.9 no.1
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• pp.62-69
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• 1995

No. of visitor at Chirisan National Park increased by three times, respectively after seven years comparing to the visitors before construction of the Songsamjae access road in 1988. Fifty percent of visitors at southern and northern rigion of Chirisan National Park visited Nogodan in spring and autumn season. And thirty percent of visitors at Sesokpyongjon accessed from Nogodan, respectively. Visitors at Nogodan and Sesokpyongion were estimated each 410.000 persons and 150.000 persons in 1994. Maximum daily users of shelter and camp ground were each 570 persons in Nogodan and 1, 100 persons in Sesokpyongjon in 1994. The Songsamjae access road in Chirisan National Park increased users' impacts on mountain ridge environment including Nogodan, Sesokpyongjon. etc. Therefore user management including prohibiting camping shall be necessary in order to minimize environmental damage of mountain ridge.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.11a
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• pp.916-919
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• 2004

The monopole theory has long been used to model air-pumped effect from the elastic cavities in car tire. This approach models the change of an air as a piston moving backward and forward on a spring and equates local air movements exactly with the volume changes of the system. Thus, the monopole theory has a restricted domain of applicability due to the usual assumption of a small amplitude acoustic wave equation and acoustic monopole theory. This paper describes an approach to predict the air-pumping noise of a car ave with CFD/Kirchhoff integral method. The type groove is simply modeled as piston-cavity-sliding door geometry and with the aid of CFD technique flow properties in the groove of rolling car tyre are acquired. And these unsteady flow data are used as a air-pumping source in the next Cm calculation of full tyre-road geometry. Acoustic far field is predicted from Kirchhoff integral method by using unsteady flow data in space and time, which is provided by the CFD calculation of full tyre-road domain. This approach can cover the non-linearity of acoustic monopole theory with the aid of using Non-linear governing equation in CFD calculation. The method proposed in this paper is applied to the prediction of air-pumping noise of modeled car tyre and the predicted results are qualitatively compared with the experimental data.

• Asian Journal of Turfgrass Science
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• v.9 no.3
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• pp.173-185
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• 1995

Hydroseeding technique is a very popular method of revegetating slope areas through the control of soil erosion and stability by seeding grasses. This study was conducted to select turfgrass species and cultivars for hydroseeding. Experiment plots were established on various soil types and environmental conditions at Singar-Ansan high-way construction site. The investigation was designed in three cutting, one back-filling and other three spare sites with various seed mixtures. Results indicated that combinations of seed mixtures influenced seed germination and rates of surface cover. In a view of long term, vegetation shifts should be influenced by characters of slopes and micro-climate conditions. Hydroseeding did not show good results on rocky slope areas. Revegetation was only going on where there had soil. The combination of seed mixture with a higher rate of perennial ryegrass had relatively good revegetation with faster germination and seedling growth. Improved turf-type tall fescue Arid ⓡ and Falcon ⓡ seemed to have good environ-mental adaptation and drought tolerance. Wild or old type cultivars showed relatively slow green-up in spring and growth rates at the next year of seeding. For the harmonious landscaping with surrounding area, the combination of native grass mixture with cool-season grasses had good results. Slow and low revegetation rate at hack-filling site seemed to be caused by the poor development of capillary tubes in sub-soil. It was shown that a high correlation between seed germination and revegetation rate, and between three-month later coverage rate and final rate. The evaluation of coverage rate after three month seems to he acceptable to decide the accomplishment of hydroseeding results on rode side slopes.

• International Journal of Highway Engineering
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• v.10 no.2
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• pp.145-157
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• 2008

Load transfer efficiency (LTE) reflects the structural performance of doweled and undoweled joints of Jointed Concrete Pavement (JCP). A 3-dimensional (3-D) model of JCP was built using ABAQUS software in this study. Three concrete slabs were placed on bonded sublayers composed of a base and subgrade. Spring elements were used to connect the adjacent slabs at joints. Different spring constants were input to the model to simulate different joint stiffness of the concrete pavement. The LTE of the joint increased with an increase of the spring constant. The effects of material properties and geometric shape on the behavior of JCP were analyzed using different elastic modulus and thickness of the slab and base in the modeling. The results showed the elastic modulus of the subgrade affected the behavior of the slab and LTE more than that of the base and the thickness of the slab and base. The effects of a negative temperature gradient on the behavior of the slab and LTE were more than that of positive and zero temperature gradients. Joints with low stiffness were more sensitive to the temperature gradient of the slab.

• International Journal of Highway Engineering
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• v.10 no.2
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• pp.81-89
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• 2008

Shear test procedure for concrete-dowel interaction was proposed along with determination of dowel support reaction factor or shear spring stiffness constant using the spreadsheet example. For this task, three AASHTO-type standard specimens were prepared to simulate behavior of the jointed concrete pavement. A side support system was adopted to minimize twisting of the test specimen which had been observed in a preliminary test. A typical elastic behavior of the dowel-concrete interaction was observed from several test loops of loading, unloading and reloading procedures. However load versus slab displacement represents to be nonlinear. Test results show that the dowel support reaction factor ranges from 550-880 GN/m3, which is 1.4-2.2 times greater than 407GN/m3 proposed by Yoder and Witczak. This is because less torsional distraction was occurred with the help of a side support system adopted in this experiment. The dowel support reaction factor or shear spring stiffness constant obtained from the procedures proposed in this paper may be used as a reference data for the structural analysis of jointed concrete pavement.

• International Journal of Highway Engineering
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• v.17 no.3
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• pp.77-83
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• 2015

PURPOSES : In this study, a fracture-based finite element (FE) model is proposed to evaluate the fracture behavior of fiber-reinforced asphalt (FRA) concrete under various interface conditions. METHODS : A fracture-based FE model was developed to simulate a double-edge notched tension (DENT) test. A cohesive zone model (CZM) and linear viscoelastic model were implemented to model the fracture behavior and viscous behavior of the FRA concrete, respectively. Three models were developed to characterize the behavior of interfacial bonding between the fiber reinforcement and surrounding materials. In the first model, the fracture property of the asphalt concrete was modified to study the effect of fiber reinforcement. In the second model, spring elements were used to simulated the fiber reinforcement. In the third method, bar and spring elements, based on a nonlinear bond-slip model, were used to simulate the fiber reinforcement and interfacial bonding conditions. The performance of the FRA in resisting crack development under various interfacial conditions was evaluated. RESULTS : The elastic modulus of the fibers was not sensitive to the behavior of the FRA in the DENT test before crack initiation. After crack development, the fracture resistance of the FRA was found to have enhanced considerably as the elastic modulus of the fibers increased from 450 MPa to 900 MPa. When the adhesion between the fibers and asphalt concrete was sufficiently high, the fiber reinforcement was effective. It means that the interfacial bonding conditions affect the fracture resistance of the FRA significantly. CONCLUSIONS : The bar/spring element models were more effective in representing the local behavior of the fibers and interfacial bonding than the fracture energy approach. The reinforcement effect is more significant after crack initiation, as the fibers can be pulled out sufficiently. Both the elastic modulus of the fiber reinforcement and the interfacial bonding were significant in controlling crack development in the FRA.

• Atmosphere
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• v.33 no.4
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• pp.343-354
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• 2023

Turbulence produced on roadways is one of the major factors determining the dilution rates at the initial stage of traffic emissions of air pollutants and, thus, the distribution of air pollutants near the roadways. Field experiments were conducted on Gyeongbu Highway, one of the busiest highways in Korea, for 4~7 days in winter, spring, and summer. Two three-dimensional ultrasonic anemometers were installed on both sides of the highway to estimate turbulence intensities (vertical wind fluctuation and kinetic turbulence energy) induced by the roadway. Roadway-induced turbulence consists of three components: structural road-induced turbulence (S-RIT), thermal road-induced turbulence (T-RIT), and vehicle-induced turbulence (VIT). The contribution of T-RIT to the total RIT was insignificant (less than 10%), and the majority of RIT was S-RIT (by the highway embankment) and VIT. In this study, we propose the empirical relationships of VIT as a function of traffic density and wind speed under free-flow traffic conditions. Although this empirical relationship appears to underestimate the VIT, it can be applied to the air quality models easily because the relationship is simple and only needs readily obtainable input variables (wind speed and traffic information).

• Journal of the Korean Institute of Landscape Architecture
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• v.50 no.1
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• pp.68-77
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• 2022

The human thermal environment in an apartment complex located in Seoul was quantitatively analyzed to devise methods to modify human heat-related stresses in landscape and urban planning. Microclimatic data (air temperature, relative humidity, wind speed, and short- and long-wave radiation) were collected at 6 locations [Apt-center, roof (cement), roof (grass), ground, playground, and a tree-lined road] in the late spring and summer, and the data were used to estimate the human thermal sensation, physiological equivalent temperature (PET) and universal thermal climate index (UTCI). As a result, the playground location had the highest thermal environment, and the roof (grass) location had the lowest. The mean difference between the two locations was 0.8-1.1℃ in air temperature, 1.8-4.0% in relative humidity, and 7.5-8.0℃ in mean radiant temperature. In open space locations, the wind speed was 0.4-0.5 ms-1 higher than others. Also, a wind tunnel effect happened at the Apt-center location during the afternoon. For the human thermal sensation, PET and UTCI, the mean differences between the playground and roof (grass) locations were: 5.2℃ (Max. 11.7℃) in late spring and 5.4℃ (Max. 18.1℃) in summer in PET; and 3.0℃ (Max. 6.1℃) in late spring and 2.6℃ (Max. 9.8℃) in summer in UTCI. The mean differences indicated a level change in PET and 1/2 level in UTCI, and the maximum differences showed greater changes, 2-3 levels in PET, and 1-1.5 levels in UTCI. Moreover, the roof (grass) location gave 4.6℃ PET reduction and a 2.5℃ UTCI reduction in late spring, and a 4.4℃ PET reduction and a 2.0℃ UTCI reduction in the summer when compared with the roof (cement) location, which results in a 2/3 level change in PET and a 1/3 level in UTCI. Green infrastructure locations [roof (grass), ground, and a tree-lined road] were not statistically significant in the reduction of PET and UTCI in thermal environment modifying effects. The implementation of green infrastructure, such as rooftop gardens, grass pavement, and street tree planting, should be adopted in landscape planning and be employed for human thermal environment modification.

• Journal of the Korea Institute of Military Science and Technology
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• v.6 no.4
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• pp.9-21
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• 2003

This paper describes the practical implementation of a semiactive hydropneumatic suspension system to provide the high off-road performance of military tracked vehicles. Real gas behavior of a spring system, frictional forces of joints, and the dynamics of a continuously variable damper are considered. The control system is consisted of two control loops, an outer loop calculates a target spool position which can deliver the required damping force and an inner loop tracks the required spool position. Dynamic tests of the one axis model show that the semiactive suspension system considerably reduces the acceleration as well as velocity and displacement of the sprung mass than the passive one.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.15 no.6 s.99
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• pp.764-771
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• 2005

This study investigates the 3-axis transmissibility of the vehicle compact disk player's mainbase which is supported by dampers and springs. These dampers and springs as the important element ' determining the vibration performance of vehicle compact disk Player are used to minimize the vibration which is induced by driving the vehicle. In order to determine the analysis frequency band, we investigated the excitation frequency of road from the vehicle test. As the characteristics of damper and spring were changed, we carried out the vibration test and investigated the change of transmissibility, Also, we carried out the sensitivity analysis for transmissibility and we found out that the properties of damper were the dominant element in the vibration performance of vehicle compact disk player.