• Journal of the Korea institute for structural maintenance and inspection
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• v.18 no.2
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• pp.21-29
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• 2014

This paper evaluates the shear strength, behavior and failure mode of reinforced concrete beams with deformed GFRP reinforcing bar. Four concrete beam specimens were constructed and tested. It was carried out to observe failure behavior and load-deflection of simply supported concrete beams subjected to four-point monotonic loading. In order to eliminate of the uncertainty by the shear reinforcements, any stirrups were not used. Variables of the specimens were shear span-depth ratio, effective reinforcement ratio. The dimensions of specimen is 3,300 or $1,950mm{\times}200mm{\times}240mm$. Clear span and shear span were 2,900mm, 1,000mm respectively. Shear span-depth ratios were 6.5 and 2.5. Effective ratios of Longitudinal GFRP reinforcing bar were $1.126{\rho}_{fb}$, $2.250{\rho}_{fb}$, $3.375{\rho}_{fb}$ and $0.634{\rho}_{fb}$. All beam specimens were broken by diagonal-tension shear and the ACI 440.1R, CSA S806 and ISIS, which was used to design test beams, showed considerable deviation between prediction and test results of shear strengths.

• Journal of the Korean Geosynthetics Society
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• v.13 no.2
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• pp.31-39
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• 2014

The helical pile is a manufactured steel pile consisting of one or more helix-shaped bearing plates affixed to a central shaft. This pile is installed by rotating the shaft into the ground to support structural loads. The advantages of helical piles are no need for boring or grout process, and ability to install with relatively light devices. The bearing capacity of the helical pile is exerted by integrating the bearing capacity of each helix plate attached to the steel shaft. In this paper, to estimate the bearing capacity of moderate-size helical piles, 6 types of helical piles were constructed with different shaft diameter, plate configuration and the penetration depth. A series of field loading tests was performed to evaluate the effect of helical pile configuration on the bearing capacity of helical pile, constructed in two different shaft diameters (i.e. 73 mm and 114 mm). In the same way, the diameter of bearing plate was also changed from 400mm to 250mm with one or three plates. As well, the penetration depth was varied from 3m to 6m to analyze the relation between the penetration depth and the bearing capacity. As a result, not only the increase of the shaft diameter, but also the number or diameter of helix bearing plates enhances the bearing capacity. Especially the configuration of the helix plate is more critical than the shaft diameter.

• Proceedings of the KSME Conference
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• 2008.11b
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• pp.2256-2261
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• 2008

The electric snow melting and deicing system by electric heating cable which is adopted in this study is a part of road facilities to keep surface temperature of the road higher than freezing point of water for melting the snow or ice accumulated on it. The electric heating cables are buried under paved road at a certain depth and a certain pitch and operated automatically and manually. Design theory, amount of heating, and installation standard vary according to economic situation, weather condition, and installation place. A main purpose of this study is figuring out the appropriate range of required heat capacity and installation depth and pitches for solving snowdrifts and freezing problems with minimum electric power consumption. This study was performed under the ambient air temperature($-2^{\circ}C$, $-5^{\circ}C$), the pitches of the electric heating cables (200 mm, 300 mm), heating value ($250\;W/m^2$, $300\;W/m^2$, $350\;W/m^2$).

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.05a
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• pp.856-860
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• 2002

The main objective of this study is to consider the effect of fatigue crack behavior on the variable depth of micro hole defects in SM20C at the symmetric position. The fatigue crack propagation test is performed by rotary bending fatigue test machine. The relationship between crack length(2a), cycles(N) and crack growth rate(da/dN) are investigated in this study. The result from the rotary bending fatigue test under the applied stress at 250MPa turned out that the fatigue life illustrated almost constant when the depth of symmetric micro hole deflects is both part A and B at the hope depth(h) = 0.5mm.

• Journal of the korean academy of Pediatric Dentistry
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• v.31 no.2
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• pp.280-289
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• 2004

Adequate polymerization is a crucial factor in obtaining optimal physical properties and clinical performance of resin composite restorative materials. The purpose of this study was to determine the effectiveness of shade and depth on dental composite resin polymerized with plasma arc curing unit employing FTIR and microhardness. From this experiment, the following results were obtained : 1. The light transmission and microhardness by mode 6 in plasma arc curing were similar to by 20 secs in halogen light curing. 2. The experimental groups of A1, A2, A3, A3.5 were not signifcant difference to light transmission and microhardness on surface and 2mm depth, but were significant difference on 3mm and 4mm depth. Especially light transmission and microhardness were small in darker shade and deeper thickness. 3. Compared with depth cure, uncured monomer amount increased at more than 2mm depth. 4. The light transmission by FTIR and polymerization by microhardness were significant corelation.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.2
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• pp.465-473
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• 2013

In this Study, the performance of precast PSC slabs with fire resistance panel for fire resistance of the tunnel system was evaluated by experimentally. The fire test was performed in fire resistance (electric) furnace according to RABT(Richtlinien fur die Ausstatung und den Betrieb von stra${\beta}$entunneln) time heating temperature curve. The test results showed that the measured temperatures at the t=0 mm depth of PSC slab with precast fire resistance panel during a fire was maximum temperature $367^{\circ}C$, lower than $380^{\circ}C$ (ITA 2004), when damage occurs. Also, at the t=25 mm, the maximum temperature was $239^{\circ}C$, which was lower than the damage temperature of rebar, $250^{\circ}C$. From the results, the use of precast fire resistance panel (t=25 mm) improves fire resistance of PSC structures.

• Journal of the Korean GEO-environmental Society
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• v.23 no.8
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• pp.17-22
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• 2022

To reduce the bump of bridge/earthwork transition area caused by the settlement of the soft ground during public use, the road agencies have been continuously overlay or repavement at those areas. In this study, the vehicle-mounted ground penetrating radar with 1GHz air-coupled antenna was used to estimate the settlement amount of those areas for nine bridges built in the soft ground. Results shows that it is possible to effectively measure the thickness of pavement up to a depth of 1 m on an asphalt road with ground penetrating radar technology that can inspect under the road surface. Distinctively deformation of the road surface, the variation in the thickness of the pavement measured at bridge/earth transition areas is equivalent to a minimum of 50 mm and a maximum of 600 mm, and there is a risk of cavity in the ground. The difference in the increased pavement thickness is 50~250 mm for each bridge connection, which may cause the differential settlement. In this study, by using the result of the ground penetration radar, a plan for improving drivability and maintenance of the settlement is suggested and applied to the field.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2018.06a
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• pp.240-243
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• 2018

최근 VR(Virtual Reality)와 AR(Augmented Reality)의 발전에 따라 영상 또는 이미지에서 카메라와 물체 사이의 거리를 추정하는 기술에 대한 연구가 활발히 진행되고 있다. 본 논문에서는 카메라와 물체 사이의 거리 추정 방법 중에서 단일 카메라를 이용하여 촬영한 이미지의 흐림 정도를 분석하여 3D 거리를 추정하는 알고리즘을 연구한다. 특히 고가의 렌즈가 장착된 DSLR 카메라가 아닌 스마트폰 카메라 이미지에서 DFD를 이용한 거리 추정 방법 중 1개의 이미지를 이용한 3D 거리 추정 방법과 초점이 서로 다른 2개의 이미지를 결합하여 3D 거리를 추정하는 방법을 연구하고 최적회된 피사체 범위에 대해 연구하였다. 한 개의 이미지를 이용한 거리 추정에서는 카메라의 초점 거리를 200 mm로 설정할 때, 두 개의 이미지를 이용한 거리 추정에서는 두 이미지의 초점 거리를 각각 150 mm, 250 mm로 설정했을 때 가장 넓은 거리 추정 범위를 갖는다. 또한, 두 거리 추정 방법 모두 초점 거리가 가까울수록 가까운 물체의 거리 추정에 효율적인 것으로 나타났다.

• Journal of Bio-Environment Control
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• v.14 no.3
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• pp.166-173
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• 2005

This study was carried out to evaluate the structural stability in a non-heating greenhouse with a single cover for Citrus cultivation which was built up in Jeju on the basis of the drawing designed by Jejudo Agricultural Research & Extension Services and also to make use of the data for developing a standardized non-heating greenhouse in Jeju. The analysis of a structural stability was conducted by using CFX-5.7 and ANSYS under the design condition of a maximum accumulated snow-depth of 19.1 cm as well as an instantaneous maximum wind velocity of $36.6\;m{\cdot}s^{-1}$ which was set up on the basis of meteorological statistics in Jeju. As a result, the maximum von-Mises stress applied on pipes under the wind velocity of $36.6\;m{\cdot}s^{-1}$ showed a value of $250\;N{\cdot}mm^{-2}$ which was greater than the allowable stress of the pipe with a value of $235.4\;N{\cdot}mm^{-2}$ (=$2,400\;kg{\cdot}cm^{-2}$) and also $53.8\;N{\cdot}mm^{-2}$ under the snow-depth of 19.1 cm, respectively. This result suggested that the greenhouse be unstable under the design condition of an instantaneous wind velocity of $36.6\;m{\cdot}s^{-1}$ so that it was necessary for the greenhouse to be reinforced to secure the structural stability.

• Journal of the Korea institute for structural maintenance and inspection
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• v.16 no.6
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• pp.18-25
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• 2012

This paper estimates the ductility of reinforced concrete columns according to configurations of transverse reinforcement. A total of 8 reinforced concrete columns were cast and tested in flexure. The test variables in this study were the configurations, yield strength, and amount of transverse reinforcement. The specimens had a cross-section of $250{\times}250mm$ and had a shear span-to-depth ratio of 4.1 to induce flexural failure. In the test, cyclic lateral load was applied to the specimens with a constant axial load. The experimental result indicated that the specimens with proposed configurations of transverse reinforcement showed higher ductility and energy dissipation capacity than the specimens with rectangular tie.