• Journal of the Korean Society of Safety
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• v.31 no.4
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• pp.64-74
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• 2016

Recently, the seismic stability evaluation of concrete gravity dams is raised due to the failure of dams occurred by the Izmit, Turkey and JiJi, Taiwan earthquake in 1999. Dams failure may incur loss of life and properties around the dam as well as damage to dam structure itself. Recently, there has been growing much concerns about "earthquake - resistance" or "seismic safety" of existing concrete gravity dams designed before current seismic design provisions were implemented. This research develops three evaluation levels for seismic stability of concrete gravity dams on the basis of the evaluation method of seismic stability of concrete gravity dams in U.S.A., Japan, Canada, and etc. Level 1 is a preliminary evaluation which is for purpose of screening. Level 2 is a pseudo-static evaluation on the basis of the seismic intensity method. And level 3 is a detail evaluation by the dynamic analysis. Evaluation results on existing concrete gravity dams on operation showed good seismic performance under designed artificial earthquake(KHC earthquake).

• Proceedings of the KSR Conference
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• 2009.05b
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• pp.641-646
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• 2009

Concrete tracks are superior to ballast tracks in the aspect of durability, maintenance and safety. However, deteriorated stiffness of railroad bed and settlement of soft ground induced by trapped or seepage water lead to problems in safety of train operation. In this research, characteristic stiffness of concrete tracks, which is determined from FRACTAL (Flexural-Rigidity Assessment of Concrete Tracks by Antisymmetric Lamb Waves) technique, was employed as an index of track displacement. The characteristic stiffness is defined using Poisson's ratio, moment of inertia and stiffness ratio of subgrade to slab. To verify validity and reliability of the proposed characteristic stiffness, experimental and theoretical researches were performed. Feasibility of the characteristic stiffness based on FRACTAL technique was proved at a real concrete track for Korean high-speed trains. Validity of the FRACTAL technique was also verified by comparing the results of impulse-response tests performed at the same measurement array and the results of SASW tests and DC resistivity survey performed at a shoulder nearby the track.

• Proceedings of the KSR Conference
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• 2011.10a
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• pp.853-860
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• 2011

The societal interest on a faster transportation demands an increase of the train speed over the current operation speed of 350 km/h. However, the dynamic response in the roadbed of concrete track system subjected to the train speed ranging between 300 to 500 km/h has been systematically investigated. Herein, a series of the 2-dimensional numerical simulations using various train speeds were performed. A single wheel was modeled by the rigid body. The rail was attached to the sleepers via linear springs in parallel. The results show that the vertical displacement at the rail and track concrete layer exponentially increases when the train speed increases over 400 km/h. This conclusion implies an existence of the critical train velocity at which the displacement of the track system dramatically increases.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.05a
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• pp.93-98
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• 2001

This study is to develop the end anchorage of external steel reinforcement of RC slab bridges. External prestress method using the existing steel is that When the anchorage is installed in slab end, a plenty of anchor bolts were required because the only tangential stress of anchor bolt received a tendon force. Then, for this reason, the wide end anchorage was required and the shape was complicate. But this reinforcement method using method that inserts anchor key at concrete surface cut a groove gets big internal force comparing to the anchorage using existing anchor bolt. Furthermore, the number of anchor bolt for installing apparently will be reduced, and the operation will be convenient because a small anchorage of a simple shape will be received a great tendon force

• Proceedings of the Korea Concrete Institute Conference
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• 2001.11a
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• pp.1009-1014
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• 2001

This study is to develop the end anchorage of external steel reinforcement of RC slab bridges. External prestress method using the existing steel is that When the anchorage is installed in slab end, a plenty of anchor bolts were required because the only tangential stress of anchor bolt received a tendon force. Then, for this reason, the wide end anchorage was required and the shape was complicate. But this reinforcement method using method that inserts anchor key at concrete surface cut a groove gets big internal force comparing to the anchorage using existing anchor bolt. Furthermore, the number of anchor bolt for installing apparently will be reduced, and the operation will be convenient because a small anchorage of a simple shape will be received a great tendon force.

• Journal of Ocean Engineering and Technology
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• v.23 no.6
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• pp.111-116
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• 2009

The cracking due to hydration heat in mass concrete must be resolved to improve the stability and durability of concrete structures. In this study, the economic efficiency was improved by replacing a copper pipe with a steel one for the heat pipe, and the heat pipe was standardized to significantly improve the operation efficiency, such as the processing, transport, assembly, and construction time. As a result of the experiment, the peak temperature of the ICSHP, ISSHP, and ISUHP specimens decreased by about $7.2{\sim}10.9^{\circ}C$ compared to the OPC specimen and the probability of a thermal crack being generated in the ICSHP, ISSHP, and ISUHP specimens decreased by up to 84~88%.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.11a
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• pp.343-346
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• 2005

This study makes the performance evaluation of water-jet chipping through analysis of ruggedness of chipping surface. The ruggedness is mapped by 3D Laser Scanner and the results are also compared with the chipping surface by mechanical chipping. And the details of in-situ works is investigated for increasing interface adhesion between existing concrete and repairing mortar. Water-jet has good operation efficiency which is up $60m^2$ per hour when the chipping depth is 7cm and also has a large ruggedness about 1.65.

• Proceedings of the Korea Concrete Institute Conference
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• 2009.05a
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• pp.167-168
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• 2009

The CFT structure is applied to newly developed CFTA girder because of improvement of ductility deformation, stiffness and internal force of structure owing to the interaction between steel tube and core concrete. CFTA girder is the structure which can reduce tensile stress due to external loads by using its arch shape and prestress force. This paper proposed constructional stage procedure and represented analytical technique considering constructional stage to investigate the safety against bridge collapse on construction and on operation.

• Proceedings of the Korea Concrete Institute Conference
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• 1996.04a
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• pp.363-369
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• 1996

PMS(Pavement Management System) is the effective and efficient decision making system to provide pavements in an acceptable condition at the lowest life-cycle cost. As the highway system become larger, the necessity of the PMS in increasing. As of December 1995, the 3rd stage of PMS project was completed. The accomplishment of the research work can be itemized to the followings : $\bullet$ Calibration of PMS submodules (1) Pavement Condition Evaluation Model (2) Pavement Distress Prediction Model (3) Pavement Performance Prediction Mode (4) Selection of Pavement Rehabilitation Criteria (5) Optimization Technique for PMS Economic Analysis $\bullet$ Development of Computer Program to Implement PMS Logic $\bullet$ A Study to Implement the Automized Pavement Condition Survey Equipment to PMS $\bullet$ PMS Test Run $\bullet$ Development of PMS Operation Guideline $\bullet$ The 2nd Pavement Condition Survey for Long-Term Pavement Performance Monitoring.

• Journal of Advanced Marine Engineering and Technology
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• v.38 no.10
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• pp.1206-1211
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• 2014

This study has been conducted to confirm the effect of sacrificial anode cathodic protection system for 90 days to protect corrosion on pier that is located in Korea. The cathodically protected structure was a slab and a pile cap. Before the construction of cathodic protection system, the macrography was carried out. As a result of the macrography, many corrosion traces were confirmed in this structure. The trace was mainly focused on joint and zones that concrete cover was eliminated. To apply the cathodic protection system, many onsite techniques have been adopted. In addition, to confirm the inner state of steel in concrete properly, a corrosion monitoring sensor (DMS-100, Conclinic Co. Ltd) has been applied. Test factors were corrosion & cathodic protection potential, 4 hour depolarization potential, resistivity and current density. After 90 days from the installation of cathodic protection system, it could confirm that proper corrosion protection effect was obtained by considering the result of tests.