• Proceedings of the Korean Geotechical Society Conference
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• 2006.10a
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• pp.56-65
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• 2006

As portions(28m) of the designed tunnel was crossing the abandoned tunnel, methods for safe construction were demanded. The level of the abandoned tunnel and the designed tunnel was almost same and each tunnel was crossing at an angle of about 40 degrees. Therefore the abandoned tunnel would adversely affect the stability of the designed tunnel. Some sections of the abandoned tunnel passes through the designed tunnel wall were fully filled with tunneling spoil and cement milk grouting to increase tunnelling stability. By checking physical properties of grouting cores drilled at the cross section of the designed tunnel and the abandoned tunnel, the quality of material filled in the abandoned tunnel was confirmed. Also the stability of the designed tunnel was checked by the monitoring during excavation of the tunnel.

• Journal of Korean Society of Steel Construction
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• v.30 no.2
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• pp.77-85
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• 2018

A through diaphragm is often used to ensure their stiffness for moment-resisting connections using rectangular steel-tube column and H-shaped beam. The through-diaphragm connections, however, have some difficulties for their applicabilities to the field due to the complexity of the fabrication and construction processes. This study thus proposes a new modular system of steel structures assembled only using bolts without welding, by bringing a connection module composed of rectangular steel-tube column, H-shaped beam and oneway bolt onto the site. An experimental study to evaluate the seismic performance of the proposed connection details based on the new modular system is then conducted. The length and type of the inner reinforcement plate are considered as the primary design parameters, and the strength, stiffness, ductility and energy dissipation capability of the new connections are experimentally analyzed by comparison to those of conventional through diaphragm connections.

• Journal of the Korea Concrete Institute
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• v.28 no.2
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• pp.129-139
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• 2016

Cast-in-place concrete-filled hollow PC (HPC) columns are used to reduce lifting load of heavy-weight PC columns and to improve the structural integrity of joints. In the present study, a new type of HPC column was proposed to improve the productivity and structural integrity of the concrete. To form the hollow PC columns, a permanent inner form was prefabricated using structural deck plates and penetrated lateral bars. Half-scale specimens of four HPC columns were tested under combined axial compression and lateral cyclic loading to evaluate the seismic resistance. In the design of test specimens, various parameters such as the spacing of lateral re-bars, the use of steel fiber, and the thickness of PC cover were considered. The test results showed that the proposed HPC columns generally exhibited satisfactory load-carrying capacity and deformation capacity without brittle failure of PC. If closely spaced hoops or fiber reinforcements are used for PC, the deformation capacity can be improved further by restraining PC spalling.

• Journal of the Earthquake Engineering Society of Korea
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• v.12 no.4
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• pp.11-17
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• 2008

This study evaluates the seismic performance of post-tensioned flat plate structures with or without slab bottom reinforcement. For this purpose, 3 and 9 story frames were designed only considering gravity loads. This study conducts a nonlinear static pushover analysis. This study was an analytical model that is able to represent punching shear failure and fracture mechanism. The analytical results showed that the seismic performance of a post-tension flat plate is strongly influenced by the existence of slab bottom reinforcement through column. By placing slab bottom reinforcement in a PT flat plate frame, lateral strength and max drift capacity are significantly increased.

• 한국초전도학회:학술대회논문집
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• v.10
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• pp.241-247
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• 2000

77 K와 self-field에서 22 A 의 Ic 를 갖는 길이 120 m, 19-심 Bi-2223상 선재를 제조하여, 두 개의 double pancake 코일로 구성된 proto-type 고온초전도 자석을 설계, 제작하여 이 자석에서의 4.2 K와 77 K에서의 I-V 특성과 운전 특성을 평가한 결과, 이 자석은 77 K 등온조건에서는 9.5 A 의 Ic를, 77 K 헬륨가스 속에서는 8.3 A 의 Ic를 나타내었고, 4.2 K 등온조건에서는 93.7 A 의 Ic와 102 A 의 Iq를, 4.2K헬륨가스 속에서는 88.4A의 Ic 와 92.0 A 의 Iq를 나타내어, 이 자석은 4.2 K 와 77 K 의 등온조건에서 각각 0.58 T 와 0.06 T 의 자장을 발생하였는데, 이는 해석적 방법으로 계산한 결과와 잘 일치하였다. 그리고 이 자석이 전도냉각되어 4.2 K 에서 운전될 때의 안정성 특성평가로서, Ic 보다 약간 큰 전류인 89 A 를 인가한 결과, 전류인가 후 82.6초 후에 quench가 발생하였는데, 이 quench는 네 번째 pancake의 전류도입선부 연결부에서와 약간 늦지만 첫 번째 pancake의 전류도입선부 연결부에서 거의 동시에 개시되어 전체로 파급된 것으로 사료되었는데, Ic 가 낮은 첫번째 pancake에서 더 높은 전압 강하가 나타났다. 또한 장착된 heater를 통하여 77 K 에서 8.9 A 의 전류로 운전되고 있는 코일에 146 joule 의 열을 가했을 때 quench 가 일어났는데, 이때 quench 는 방위각 방향의 Bi-2223/Ag 선재를 따라서 보다 Kapton 절연층을 관통하는 선재의 반경방향으로 훨씬 빨리 전파하였다.

• Journal of the Society of Naval Architects of Korea
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• v.34 no.4
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• pp.42-52
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• 1997

The basic principle of underwater ram-jet as a unique marine propulsion concept showing vary high cruise speed range(e. g. 80-100 knots) is the thrust production by the transfer of the potential energy of compressed gas to the operating liquid through kinetic mixing process. This paper is aimed to investigate the propulsive efficiency of the nozzle flow in underwater ram-jet at the speed of 80 knots for the buried type vessel. The basic assumption of the theoretical analysis is that mixture of water and air can be treated as incompressible gas. For an optimized nozzle configuration obtained from the performance analysis, preliminary data for performance evaluation are obtained and effects of nozzle inner wall friction, ambient temperature, ambient pressure, water density, gas velocity, bubble radius, flow velocity, diffuser area ratio, mass flow ratio and water velocity gradient are investigated.

• Journal of the Korean Society for Nondestructive Testing
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• v.30 no.1
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• pp.1-5
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• 2010

Acoustic emission(AE) has emerged as a powerful nondestructive tool to detect or monitor preexisting defects and leaks in the vessel structures. A Bragg grating based acoustic emission sensor system is developed. Various type of fiber Bragg grating sensor including the variable length of sensing part was fabricated and prototype sensor system was tested by using PZT pulser and pencil lead break sources. Two types of sensor attachment were used. First, the fiber Bragg grating sensor was attached fully to the surface using bonding agent. Second one is that one part of fiber was attached to the surface partly by bonding and the other part of fiber will be act as a cantilever. That is, the resonant frequency of the fiber Bragg grating sensor will depend on the length of sensing part. The final goal of the sensor system is to provide on-line monitoring of cracks or leaks in reactor vessel head penetration of nuclear power plants.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.1A
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• pp.91-97
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• 2006

This paper presents the results of push-out test conducted for the perfobond rib shear connectors welded onto steel-concrete composite deck. Push-out test specimen consists of profiled steel sheeting, perfobond rib, reinforcement, and concrete. To provide longitudinal shear resistance between the profiled sheeting and the concrete, perfobond rib with a number of holes was used. The parameters considered in the design of perfobond rib were the spacing and location of holes, and effect of reinforcing bars placed in the holes. To validate the effectiveness of the proposed system, twelve specimens were fabricated and tested. Although the scope of test was limited in nature, the results of test have shown that the perfobond ribs can be effectively used for shear connection in the steel-concrete composite decks.

• Korean Journal of Environment and Ecology
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• v.31 no.1
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• pp.104-111
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• 2017

The construction of road tunnels and bridges have delivered driving efficiency and stability based on developed engineering technology. Tunnels have the advantage of reducing the deforested area compared with other road construction methods. Since a tunnel is an underground passageway dug through the surrounding soil/earth/rock and enclosed except for the entrance and exit, commonly at each end, it does not cause a large amount of deforestation. This study surveyed the deforested areas at each end of the tunnel by the design of the tunnel entrance and exit and forest topography to minimize the amount of deforestation caused by road construction. A survey was done on a total of 150 tunnels (300 entrances and exits) on several main roads in Korea. The deforested area of each tunnel was collected by a breakdown of the entrance area and the upper area of the tunnel. According to the results of Kruskal-Wallis analysis, it was found that there was statistically a significant relation between the location of tunnels and the amount of deforestation by the topographical access type of the tunnels. The tunnel with 'facing orthogonal to incline' type access caused the smallest deforestation while the the tunnel with 'facing to valley' and 'parallel with incline' type accesses caused large deforestation during tunnel construction. Tunnel positioning in the light of topography can reduce the deforested area by up to 1.5ha at each tunnel.

• Journal of the Korean Society for Nondestructive Testing
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• v.29 no.2
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• pp.153-161
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• 2009

After several PWSCCs were found in Bugey(France), Ringhals(Sweden), Tihange(Belgium), Oconee, Arkansas, Crystal Fever, Davis-Basse, VC Summer(U.S.A.), Thuruga(Japan), USNRC and PNNL started the research on PWSCC, that is, PINC project. The aim of this project is to fabricate and obtain representative NDE mock-ups with flaws to simulate tight PWSCC cracks, to identify and quantitatively assess NDE methods for accurately detecting, sizing and characterizing tight cracks such as PWSCC, to document the range of locations and crack morphologies associated with PWSCC and observed responses and to incorporate findings from other ongoing PWSCC research programs, as appropriate. By participating in PINC project, Korean morphology technique about PWSCC and NDE technique have improved and become similar lever with other advanced country. Therefore, the evaluation technique of integrity for nickel alloy component has been improved by cooperation with university, research institute and industries.