• KSCE Journal of Civil and Environmental Engineering Research
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• v.35 no.3
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• pp.715-723
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• 2015

Earthwork in a large construction project such as a land development generally costs 20-30% of the total cost. The earthmoving process, comprising of four repetitive tasks: loading, hauling, unloading, returning, is quite simple and it does not need delicate or advanced techniques. Therefore, earthmoving earthwork planning can heavily affect the cost and time., and Even a slight deviation from the plan can increase or decrease the cost and time. This study presents a planning model that minimizes average haul distance in a large complex construction project. Based on earthwork planning, practitioners' heuristics, a districting algorithm and Simulated Annealing algorithm were employed to build the model. Districting algorithm plays a role that divides in dividing an earthmoving area into several sections. Simulated annealing provides a function that decides whether a new generated solution is confident. Finally, the proposed model was applied to a real earthmoving project of a large land development. It was found that the model showed approximately 14% improvement in average hauling distance compared to the actual design plan.

• Journal of the Korea Convergence Society
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• v.6 no.5
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• pp.85-90
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• 2015

In this study, the life evaluation due to the structural configuration of bumper attached at the front side of ATV vehicle is studied on the basis of fatigue analysis. As the purpose of this study, the characteristic of bumper exposed on the repetitive loading condition like the vibration is understood. The position of crack happened at the fatigue situation is grasped in advance and complemented in advance. It is considered that the multipurpose vehicle is designed to not be driven on the paved general road but the rough road like the unpaved load. And the weak part of bumper is understood through the study of life evaluation on this driving environment. The durability can be improved by doing the safe design of automotive bumper on the basis of the analysis result. And it is possible to be grafted onto the convergence technique at design and show the esthetic sense.

• Journal of the Korean Society for Railway
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• v.17 no.2
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• pp.123-132
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• 2014

In this study, permanent deformation of asphalt trackbed was investigated by performing repetitive load test on specimen made with dense graded asphalt mixture that was specially prepared for asphalt trackbed foundation. The obtained test results were compared with those computed from the prediction model proposed by AASHTO 2002, called MEPDG. No prediction model adaptable only for permanent deformation of the asphalt trackbed foundation has yet been developed, so the prediction model by AASHTO was adapted in this study to simulate permanent deformation of trackbed foundations in asphalt slab track and in ballasted asphalt track. In order to simulate permanent deformation, a finite element analysis was performed to obtain stresses generated in trackbed due to wheel load. It was found that the predicted permanent deformation was much smaller than the anticipated deformation and that the asphalt track could be stable during the service life of the structure.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.333-336
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• 2008

CFRP tendons have been attempted in concrete structures as a substitute for steel tendons considering their many advantages such as the corrosion-resistance, light weight etc. However, the elastic behavior up to failure is likely to result in ductility problems. To overcome such problems, prestress concrete beams with partially bonded tendons have been developed and suggested. In this new system, the un-bonded part near the mid-span contributes to the improvement of ductility. And the bonded parts at both ends play a role as a safe anchorage. According to the previous research on the static behavior, the suggested method has demonstrated enough ductility and strength. However it is essential to verify the long-term safety for repetitive fatigue loads under service states. For this purpose, flexural fatigue loading tests were carried out in this research. This paper includes an experimental investigation on the static load-carrying capacities of the beams with or without fatigue tests. The results showed that the beams prestressed with partially bonded CFRP tendons possessed good fatigue capacity under the constant cyclic loads.

• Journal of the Society of Disaster Information
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• v.8 no.4
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• pp.391-400
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• 2012

Recently, the construction industry commonly uses FRP as a reinforcement material because of its material advantages. FRP attached reinforcement has various advantages such as high strength, stiffness, excellent durability and construction practicability comparing to its weight. However, external attachment of FRP is water-tighted with low water permeable material, not draining water, probably causing damages on a permanent structure. The study manufactured it through pultrusion and examined GP(glass fiber panel) of which material-mechanical properties are almost same as the existing FRP but durability and attachment performance are better by stationary experiments, testing load-deflection curve, destruction types and load-deflection relation under repetitive loading test. As a result of 2,000,000 fatigue tests, it did not result in the destruction and showed excellent permanent attachment and durability as it displays significantly low compressive strain of concrete.

• Journal of the Korean Society of Safety
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• v.34 no.2
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• pp.40-47
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• 2019

The Half-depth precast deck is a structural system that utilizes pre-cast panels pre-built at the factory as formwork at the construction stage and as a major structural member at the same time after completion. These systems have joints between segments, and the detail and performance of the joints are factors that have a very large impact on the quality, such as the constructability and durability of the bridge decks. In this study, strength performance evaluation was performed for improved joints using connecting rebar by experimental method. Static loading tests were conducted on the test specimen with improved joint, those with existing joint and those without joint. The test results of the specimens were compared to each other, and the flexural strength required by the design was compared. The flexural strength required in the design was presented by finite element analysis. It has been shown that the flexural strength of the specimens with joints were more than twice that required by the design. But the flexural strength of the specimen with existing joint was about 84% of that without joint. The flexural strength of the specimen with improved joints was a nearly similar degree of that compared to the specimen without joint. And a comparison of the moment-deflection relationship curves of the two specimens also shows a very similar flexural behavior. It is confirmed that improved joint has sufficient flexural strength. In addition to strength, the bridge decks require serviceability, such as deflection and cracking, and in particular, fatigue resistance due to repetitive live loads is an important performance factor. Therefore, further verification studies are required.

• Journal of the Korean Geotechnical Society
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• v.22 no.7
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• pp.13-21
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• 2006

When enforced earth is used for the retain wall and four walls, the most important thing would be how to maximize the land utilization. Accordingly, in case of enforced earth, we pile up the minimal height of earth ($20{\sim}50\;cm$) and harden the earth using a static dynamic hardening machine. In this paper, we tried to analyze and compare the stress transformation characteristics of reinforced weathered granite soil with geosynthetics when repetitive load is added to the enforced earth structure and when static load is added. The result is that the cohesion component of the strength increased greatly and the friction component decreased slightly.

• Journal of the Korean Society for Railway
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• v.20 no.2
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• pp.241-247
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• 2017

Railway bridges with continuously welded rail have a limitation of span length due to track-bridge interaction. In order to overcome this, a sliding slab track system has been developed that comprises with a low-frictional sliding layer between the bridge deck and the track slab to isolate the longitudinal behavior between the bridge and the track. In this study, a real scale track system is prepared to experimentally evaluate the longitudinal frictional behavior. Applied loading rates were 0.2, 1.0, 5.0 and 10mm/min; vertical mass on the track are track slab only, 5,000 and 10,000kg added mass, respectively. Test results showed that the resulting frictional coefficients varied from 0.22 to 0.33. In addition, 10,000 cycle loadings were applied to simulate repetitive sliding to represent 30 years of service life. The frictional coefficient increase was measured and found to be 7% of that of the initial loading stage, which means that the sliding layer is adequate to provide low-frictional behavior for the sliding slab track system. Effects of changes of the frictional coefficient of the sliding layer were analyzed by rail-structure interaction analysis.

• Microbiology and Biotechnology Letters
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• v.31 no.4
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• pp.368-376
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• 2003

Cyclodextrin glucanotransferase (CGTase) from Paenibacillus sp. JB-13 was immobilized on various carriers by several immobilization methods such as ionic binding, covalent linkage and ultrafiltration to improve the process performance. The ultrafiltration and covalent linkage with CNBr-activated sepharose 4B were found as the best method for immobilization of CGTase. The ability of CGTase immobilization onto CNBr-activated sepharose 4B was as high as 18,000 units/g resin when the conditions was as follows: contact time 9 hrs at $37^{\circ}C$, pH 6.0, 100 nm and enzyme loading 24,000 units/g resin. The optimum conditions for production of 2-O-$\alpha$-D-Glucopyranosyl L-Ascorbic acid by immobilized CGTase turned out to be: pH 5.0, temperature $37^{\circ}C$, 20% substrate solution containing 8% (w/v) of soluble starch and 12% (w/v) of L-ascorbic acid sodium salt, 100 rpm, far 25 hrs and with 800 units of immobilized CGTase/ml substrate solution. Moreover the CGTase activity could be stably maintained for 8 times of repetitive reactions after removing products by ultrafiltration through YM 10 membrane.

• International Journal of Highway Engineering
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• v.13 no.3
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• pp.21-30
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• 2011

As well known, dowel bars are used to transfer traffic load acting on one edge to another edge of concrete slab in concrete pavement system. The dowel bars widely used in South Korea are round shape steel bar and they shows satisfactory performance under bending stress which is developed by repetitive traffic loading and environment loading. However, they are not invulnerable to erosion that may be caused by moisture from masonry joint or bottom of the pavement system. Especially, the erosion could rapidly progress with saline to prevent frost of snow in winter time. The problem under this circumstance is that the erosion not only drops strength of the steel dower bar but also comes with volume expansion of the steel dowel bar which can reduce load transferring efficiency of the steel dowel bar. To avoid this erosion problem in reasonable expenses, dowers bars with various materials are being developed. Fiber reinforced plastic(FRP) dower that is presented in this paper is suggested as an alternative of the steel dowel bar and it shows competitive resistance against erosion and tensile stress. The FRP dowel bar is developed in tube shape and is filled with high strength no shrinkage. Several slab thickness designs with the FRP dowel bars are performed by evaluating bearing stress between the dowel bar and concrete slab. To calculated the bearing stresses, theoretical formulation and finite element method(FEM) are utilized with material properties measured from laboratory tests. The results show that both FRP tube dowel bars with diameters of 32mm and 40mm satisfy bearing stress requirement for dowel bars. Also, with consideration that lean concrete is typical material to support concrete slab in South Korea, which means low load transfer efficiency and, therefore, low bearing stress, the FRP tube dowel bar can be used as a replacement of round shape steel bar.