• Proceedings of the Computational Structural Engineering Institute Conference
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• 2011.04a
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• pp.178-181
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• 2011

본 연구에서는 광섬유센서를 내장한 스마트강연선을 이용하여 초고성능콘트리트로 제작된 하이브리드 사장교 세그먼트의 횡방향 도입 긴장력을 계측하고 세그먼트 내부의 프리스트레스를 계측하여 즉시손실에 해당하는 정착장치 활동에 의한 손실과 마찰손실을 도로교설계기준(2005)의 설계 마찰손실과 비교하였다. 제작된 2개의 UHPC 사장교 세그먼트는 횡방향 길이 16.7m, 종방향 길이 1.75m, 높이 1.5m이며 각 시험체의 1/4, 1/2, 3/4지점에 긴장력을 계측하기 위해 3개의 FBG센서를 배치하였다. 긴장력은 유압잭을 이용하여 5개의 강연선에 동시에 순차적으로 도입되었으며, 단부에서 최대 도입 긴장력은 세그먼트 1은 734kN, 세그먼트 2는 639kN이었다. 도로교설계기준에 제시된 마찰계수의 중간값(파상마찰계수=0.00405, 곡률마찰계수=0.20)을 사용하여 FBG센서 위치에서 계산된 긴장력은 계측치와 5% 이내의 차이를 보였으며, 정착장치 활동에 의한 순간손실은 긴장단에서 최대 12.8%로 계측되었다. 이로부터 이 연구에서 제시하는 긴장력계측방법의 적용성을 입증할 수 있었으며, 향후 이 방법은 프리스트레스트 콘크리트 교량의 설계기준 마찰계수 개정을 위한 연구에 좋은 도구로 활용될 수 있을 것으로 기대된다.

• Journal of Korean Tunnelling and Underground Space Association
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• v.24 no.6
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• pp.699-714
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• 2022

The objective of this study is to suggest a safe and economical pillar reinforcement method when very near-twin tunnels with a minimum interval of 1 m passes through a soft zone such as weathered soil or weathered rock. A standard cross-sectional view of a two-lane road tunnel was applied to suggest a pillar reinforcement method for the very near-twin tunnels. The thickness of the pillar was 1 m. The ground condition around the tunnel was weathered soil or weathered rock. There were four reinforcement methods for pillar stability evaluation. These were rock bolt reinforcement, pre-stressed steel strand reinforcement, horizontal steel pipe grouting reinforcement, horizontal steel pipe grouting + prestressed steel strand reinforcement. When the ground condition was weathered soil, only the pillar reinforced the horizontal steel pipe grouting + prestressed steel strand did not failed. When the ground condition was weathered rock, there were no failure of the pillar reinforced the horizontal steel pipe grouting or the horizontal steel pipe grouting + prestressed steel strand. It is considered that the horizontal steel pipe grouting reinforcement played a role in increasing the stability of the upper part of the pillar by supporting the upper load applied to the upper part of the pillar.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.31 no.1
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• pp.39-46
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• 2018

In this paper, an unbonded post-tensioning anchorage for a single-stranded wire that allows more efficient stress distribution in the post-tensioned anchorage zone was developed by using a finite element analysis using a commercial program. The stress analysis was carried out using a 3D model in the anchorage zone of the concrete member using the developed anchorage. The result of analysis ensured that the developed anchorage reduced the maximum bursting stress in anchorage zone compared to the case of existing anchorage and the location where maximum bursting stress also occurred closer to the anchorage. Bursting force was calculated using AASHTO, modified $M{\ddot{o}}rsch$ and Stone. As a result, it was concluded that an effective reinforcement design of the anchorage zone can be designed by modified $M{\ddot{o}}rsch$.

• Journal of Korean Association for Spatial Structures
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• v.20 no.1
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• pp.41-48
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• 2020

In this study, the design of anchorage zone for unbonded post-tensioned concrete beam with single tendons of ultimate strength 2400MPa was evaluated to verify that the KDS 14 20 60(2016) and KHBDC 2010 codes are applicable. The experimental results showed that the bursting force equation of current design codes underestimated bursting stress measured by test, because the KDS 14 20 60(2016) and KHBDC 2010 propose the location of the maximum bursting force 0.5h which is the half of the height of member regardless of stress contribution. Although the allowable bearing force calculated by current design codes was not satisfied the prestressing force, the cracks and failure in anchorage zone was not observed due to the strengthening effect of anchorage zone reinforcement.

• Journal of Korean Tunnelling and Underground Space Association
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• v.20 no.5
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• pp.823-837
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• 2018

Congestion of the city with the rapid industrial development was accelerated to build complex social infrastructure. And numerous structures have been designed and constructed in accordance with these requirements. Recently, to solve complex urban traffic, many researches of large-diameter tunnel under construction downtown are in progress. The large-diameter tunnel has been developed with a versatile double-deck of deep depth tunnel. For the safe tunnel construction, ground reinforcement methods have been developed in the weakened pillar section like as junction of tunnel. This paper focuses on evaluation of the effects of new developed ground reinforcement methods in double-deck junction. The values of reinforcement determined from the existing and developed methods were compared to each other by numerical simulation.

• Journal of Biosystems Engineering
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• v.31 no.5 s.118
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• pp.423-429
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• 2006

The heat pump water heater developed in this research consisted of one evaporator, one compressor, 1st condenser, 2nd condenser, one expansion valve, one water tank, one recirculation circuit and etc. The performance of heat pump water heater was tested and analyzed. The quantities of output water changed linearly from 2380 to $660{\ell}/h$, and the output water temperature changed curvedly from 29.9 to $44.5^{\circ}C$ when the opening rate of recirculation valve changed from 0 to 100%. The COP of heat pump water heater increased from 3.0 to 3.8 when the quantities of output water changed from 660 to $2380{\ell}/h$. When the temperature distributions of water tank were measured during 50 minutes after turning on the heat pump, the temperature stratification by the level appeared apparently. When the inlet water temperature changed from 30 to$50^{\circ}C$, the output energy of heat pump hardly changed. The surface area of double pipe heat exchanger changed from 0.429 to $6.254m^2$ when the compressor capacity increased from 1.0 to 50.0 PS.