• International Journal of Highway Engineering
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• v.20 no.3
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• pp.19-26
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• 2018

PURPOSES : The main purpose of this study is suggest of field bond strength evaluation method for more objective evaluation method through Evaluation of Bond Strength Properties with changing aspect ratio and temperature. METHODS : The evaluation is laboratory bond strength test. Using the core machine, the pull-off test method ; the bond strength test of interface layer the universal testing machine. RESULTS : As a result of the laboratory bond strength evaluation, it was verified that the bond strength by aspect ratio decreases linearly with increasing aspect ratio and the bond strength properties by temperature change existed at high and low temperature condition relative to odinary temperature condition. CONCLUSIONS : According to the results of laboratory bond strength evaluation, the field bond strength evaluation results suggest applying the proposed correction factor (0.8, 1.0, 1.4, 1.9) according to aspect ratio(0.5, 0.1, 1.5, 2.0), For more objective evaluation of the bond strength, it is analyzed that the evaluation value is within $6{\sim}32^{\circ}C$ and the result can be obtained within 5% of the coefficient of variation.

• The Journal of Engineering Geology
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• v.8 no.2
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• pp.153-161
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• 1998

An anisotropic characteristics of stratified sedimentary rocks should be considered in the design of tunnel. The second line of Taegu subway is under construction through the sedimentary rocks which is stratified by alternation of shale and sandstone, and Tongsoe over bridge road is planned to be constructed along the subway line. Thus the subway twin tunnels will be subjected by the bridge load of 76.2 MN per pier that will be placed in between the twin tunnels of the subway line. A numerical analysis is carried out for the stability of the twin tunnel, and the result shows that the maximum principal stress of surrounding ground is increased by 5∼6 MPa and the additional displacement of concrete lining is reached up to 8∼10mm due to the external bridge load. For the safety operation of the subway, reinforcement of the tunnel structure is highly recommended.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.19 no.6
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• pp.63-76
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• 2016

Slope revegetation refers to the use of vegetation and construction to protect a barren slope devastated by road and building construction. Among many revegetation strategies, hydroseeding has been widely utilized to stabilize barren slopes and has become the representative approach. Previous studies on slope stability have been conducted from a civil engineering perspective, mainly evaluating the stability of cut-slopes on solid bedrock and the use of concrete structures to stabilize devastated slopes. This study was conducted to develop a method to evaluate erosion risk of revegetated cut-slopes, based on criteria derived from previous studies. Twenty-five factors were surveyed on both on-the-spot erosion slopes and non-erosion slopes after slope revegetation to compare slope types. The scores of all non-erosion slopes exceed 80 score while erosion slopes are 80 below. Erosion slopes got the range of 68-74 score while non-erosion slopes got the range of 81-100 score in the first result which was not applied for weighted-values. The scores of all non-erosion slopes exceeded 3.10, while erosion slopes were below 3.10. Erosion slopes were in the range of 2.73-3.09, while non-erosion slopes were in the range of 3.15-3.90 in the second result, which was applied with weighted-values according to the AHP result from a previous study.

• Structural Engineering and Mechanics
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• v.50 no.4
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• pp.501-524
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• 2014

This paper presents a type of composite box girder with corrugated webs and concrete filled steel tube slab to overcome cracking on the web and reduce self-weight. Utilizing corrugated steel web improves the efficiency of prestressing introduced into the top and bottom slabs due to the accordion effect. In order to understand the loading capacity of such new composite structure, experimental and numerical analyses were conducted. A full-scale model was loaded monotonically to investigate the deflection, strain distribution, loading capacity and stiffness during the whole process. The experimental results show that test specimen has enough loading capacity and ductility. Based on experimental works, a finite element (FE) model was established. The load-displacement curves and stress distribution predicted by FE model agree well with that obtained from experiments, which demonstrates the accuracy of proposed FE model. Moreover, simplified theoretical analysis was conducted depending on the assumptions which were confirmed by the experimental and numerical results. The simplified analysis results are identical with the tested and numerical results, which indicate that simplified analytical model can be used to predict the loading capacity of such composite girder accurately. All the findings of present study may provide reference for the application of such structure in bridge construction.

• Journal of the Korean Society of Safety
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• v.30 no.5
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• pp.67-73
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• 2015

In this paper, the simple truss model was modified to predict the punching shear strength of long-span prestressed concrete (PSC) deck slabs under wheel load including the effects of transverse prestressing and long span length between girders. The strength of the compressive zone arounding punching cone was evaluated by the stiffness of inclined strut which was modified by considering aging effective modulus. The stiffness of springs which control lateral displacement of the roller supports consists of the steel reinforcement and prestressing which passed through the punching cone. Initial angle of struts was determined by the experimental observation to compensate for uncertainties in the complexities of the punching shear. The validity of computed punching shear strength by modified simple truss model was shown by comparing with experimental results and the experimental results were also compared with existing punching shear equations to determine level of predictability. The modified simple truss model appeared to better predict the punching shear strength of PSC deck slabs than other available equations. The punching shear strength, which was determined by snap-through critical load of modified simple truss model, can be used effectively to examine punching shear strength of long span PSC deck slabs.

• Geotechnical Engineering
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• v.7 no.2
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• pp.27-40
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• 1991

The Sunghak Campus, Dong-A University, which located at the excavated area of mountain, has been constructed year by year for about 10 years since 1978. The buildings, steep slopes, road and so on in the Campus area were damaged by heavy rainfall more than 200mm 1 day on August, 1989. The methods used for the investigation and repair methods of the damage are the preliminary investigation, the present condition survey, 50 by 50m grid survey, compasstraverse for locating outcrops, geopysical exploration, geologic survey, boring and laboratory soil testing. Based on the results of investigations, the causes of the failures have been evaluated, and the repair methods have been set up as horizontal drains, removal of the dangerous rock, retaining wall with subsurface drains, the elimination of colluvium and slope stabilization by use of precast concrete grids and so on.

• Structural Monitoring and Maintenance
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• v.4 no.1
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• pp.1-15
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• 2017

Installation of sensors networks for continuous in-service monitoring of structures and their efficiency conditions is a current research trend of paramount interest. On-line monitoring systems could be strategically useful for road infrastructures, which are expected to perform efficiently and be self-diagnostic, also in emergency scenarios. This work researches damage detection in composite concrete-steel structures that are typical for highway overpasses and bridges. The techniques herein proposed assume that typical damage in the deck occurs in form of delamination and cracking, and that it affects the peak power spectral density of dynamic curvature. The investigation is performed by combining results of measurements collected by long-gauge fiber optic strain sensors installed on monitored structure and a statistic approach. A finite element model has been also prepared and validated for deepening peculiar aspects of the investigation and the availability of the method. The proposed method for real time applications is able to detect a documented unusual behavior (e.g., damage or deterioration) through long-gauge fiber optic strain sensors measurements and a probabilistic study of the dynamic curvature power spectral density.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2007.10a
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• pp.887-890
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• 2007

For a integrated system to control several parking lots within a commercial district, it is required to guide a route to a nearest neighbor parking lot considering diverse realtime constraints such as realtime status of parking lots and changes of an access route. This paper proposes an optimized route-searching technique of integrated parking control system considering realtime contraints. In concrete, it proposes a method of researching a route in the surrounding area considering various status of parking lots that a customer designates (no parking, closed, under construction, no passing of a road) and deals with a route-searching technique optimized for each situation in detail.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 1996.06c
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• pp.1055-1062
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• 1996

A method for automatically driving paddy vehicles, such as rice transplanters, etc., straight ahead in a paddy field was investigated . The direction of such vehicles must be precisely controlled to do the operations as straight. However, the alignment of the from wheels becomes distorted due to the unevenness of the ground, preventing the vehicle form going straight. If the proper alignment of the front wheels is maintained , the vehicle can be driven straight ahead greater precision. To investigate the influence of the ground uneveness, the behavior of a paddy vehicle running over an obstacle was quantified. The left wheel ran over an obstacle on a flat concrete road surfaced. When the steering wheel was free, the front wheels were forced toward the left when vehicle went up the obstacle and toward the right when the vehicle went down it. The torsion of the wheel when the vehicle went down the obstacle was larger than that when it went up ,so it turned right 5 degrees. Sinc hydraulic control steering decreased the steering angle , it turned right 3 degrees. These results suggest that a vehicle can be driven straight ahead with high precision when the steering angle is changed in response to the direction and inclination of the vehicle . Such results were obtained in a paddy field tests.

• International Journal of Highway Engineering
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• v.20 no.1
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• pp.97-105
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• 2018

PURPOSES : Asphalt concrete pavement is damaged by various causes such as traffic and environmental loads. The distressed pavement should be maintained by various methods to provide a comfortable and safe pavement for the driver. This study evaluates the effect of adding a mixing procedure to enhance the mixture quality in the hot in-placement recycled asphalt pavement method, which is an asphalt-pavement maintenance method. METHODS : Various test methods such as Marshall stability and dynamic stability, were employed to estimate the recycled asphalt mixture with and without an additional mixing, using the hot in-placement recycled asphalt pavement method. RESULTS : The mixture samples used in this study were taken before and after the addition of the mixer in the hot in-placement recycled asphalt pavement method (HIR) at field construction sites in GongJu and JinJu in South Korea. The test results of both mixtures satisfied the asphalt-mixture standard specifications. CONCLUSIONS : This study confirmed that adding a mixer in the HIR method results in a well-mixed new asphalt mixture, rejuvenator, and reclaimed asphalt mixture.