• Proceedings of the Korea Concrete Institute Conference
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• 2009.05a
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• pp.145-146
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• 2009

In this paper, feasibility tests of 2200MPa PS strand in terms of wedge and anchor head used currently for 1860MPa PS strand were performed. Static and fatigue tests for PT anchorage systems from 4 companies were conducted in compliance with ETAG013(European Technical Approval Guideline). The test results implied that some of them can be used for 2200MPa PS strand without improvement and some with small improvement.

• Journal of the Korea Concrete Institute
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• v.24 no.6
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• pp.727-735
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• 2012

Recently, a high-strength strand of 2400 MPa was developed using domestic technologies. In 2011, KS D 7002 was revised to cover the newly developed high-strength strands to support their practical usage. Presently, however, discussions and evaluations are not sufficient on the mechanical properties of the strands and their performance in structural members. Also, there were no detailed reviews on the need to revise the current design code for practical use of the high-strength strands. In this study, flexural behavior of a member with the high-strength strands was estimated through sectional analysis and a review and comparison of the domestic and foreign design codes were conducted considering the analysis results. Also, the need for the revision of the design code was discussed. Such discussion especially focused on the estimation of the stress in strand, which related with various issues such as determination methods for yield point of strands, time-dependent loss of prestressing force, estimation of stress in strand at member failure, and net strain limit for ductile failure of member. The discussion revealed that some parts in the design code need a revision and the further studies are required.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.21 no.3
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• pp.287-294
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• 2008

This study proposes a novel method for in service evaluation of tension force of a prestressed 7-wire strand which is frequently employed for retrofitting bridge superstructure. The smart strand is made by replacing the straight king wire of the strand with an instrumented steel tube in which the FBG sensor is embedded. Since the strain of the smart strand can easily be measured using the sensor, it is possible to monitor tension force of the strand during the service. For the sake of demonstrating effectiveness of the proposed strand, we came up with a 7.0m long prototype with 2 FBG sensors, and it is applied as an external tendon to a 6.4m long and 0.6 high RC T-shaped beam. A loading-unloading test has been carried out, and estimated tension forces using the smart strand are compared with measured forces by load cell. The comparison showed that the proposed smart tendon is useful and accurate for monitering tension force of the prestressed tendon.

• Journal of the Korea institute for structural maintenance and inspection
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• v.17 no.4
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• pp.18-29
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• 2013

A new precast concrete (PC) beam and column connection system using non-prestressed wire strands was recently developed. The system is composed of one unit of two-storied PC-column and PC-beams with U-shaped ends. The connection part of the column and beams is reinforced by deformed bars and non-prestressed wire strands in combination for the improvement of workability. Structural performance of this system was verified by several experimental studies. The purpose of this study is developing a design concept of the beam reinforced by deformed bars and non-prestressed wire strands in combination, in terms of the cross-sectional analysis, based on the preceded experiment. A minimum and maximum reinforcement ratio and the calculation formula for the strength of flexural member reinforced by reinforcements having different yield strengths are derived based on KBC2009. Under consideration existing research results for the application of high strength reinforcement bars, the design yield strength of the non-prestressed wire strand is suggested. An example for the cross section design, satisfying the serviceability requirements, demonstrates the applicability of the design concept developed in the study.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.28 no.6
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• pp.707-714
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• 2015

In this paper, an experimental program has been conducted to investigate transfer length in high strength concrete members pretensioned through a seven-wire strand with FBG sensors. To measure transfer length, five members were fabricated, which had a length of 3 m and a cross-section of $150{\times}150mm$. It was measured that the concrete compressive strength was 58MPa at pretensioning. Test results indicated that more precise and reliable measurement on the transfer length was attained with FBG sensors than conventional gauges attached on concrete surface. Through comparing the measured transfer length and predictions, applicability of several transfer length models in literature was investigated. This paper can be useful for relevant research field such as investigation on the bond mechanism of a seven-wire strand in concrete members.

• Journal of the Korean Geotechnical Society
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• v.29 no.6
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• pp.33-51
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• 2013

This paper introduces the improvement of connection method for segment in tunnel lining system using prestressed steel cable and presents the results of real-scale tests. It conducted a study about the applicability and mechanical behaviour analysis of the new method that connects segment tunnel lining using prestressed steel cable by real-scale test. Through the research, it was found that the new method has stronger connection than conventional assembling methods. Also, the new method can be expected to have integrated behavior and stability increase of shield tunnel lining. It is considered that the new method is much more effective than conventional assembling methods.

• Proceedings of the Korean Fiber Society Conference
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• 2002.04a
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• pp.281-284
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• 2002

마 섬유는 흡습성이 좋고 건조가 빠르고, 습윤 시 강도가 증가되며 열전도율이 크고 통기성이 크며, 강도와 내열성이 천연 섬유 중 가장 우수하며 매끄러운 표면을 가지고있어서 광택과 방오성이 좋다. 그러나 세사방적이 어렵고 강연도가 지나치게 커서 의복소재로서 극히 제한적으로 사용되어왔으나, 최근에는 큰 강연도를 장점으로 활용하여 여름용 의복소재로 다시 각광받고 있다. 따라서 면, 레이온, 셀룰로오스계 섬유제품들에 대하여 마 제품과 유사한 효과를 낼 수 있는 다양한 의마가공법이 개발되어왔다[1,2]. (중략)

• Nuclear industry
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• v.37 no.7
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• pp.94-97
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• 2017

서울대 원자력정책센터에서는 7월 13일 서울 금호고에서 진행된 김익중 교수(동국대학교 의과대학 미생물학교실) 강연의 주요 내용을 보도한 <조선일보>의 7월 15일과 7월 17일 기사 내용 중 원자력의 위험성에 관련된 주요 내용에 대하여 기술적인 확인을 하고 그 결과를 홈페이지에 올렸다.

• Journal of Digital Contents Society
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• v.11 no.4
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• pp.513-518
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• 2010

As the number of the deaf who go out into the society has been increasing, in most of the lectures, the demands for the sign language interpretation and the accuracy of the interpretation have become more important. Especially, in order to improve the accuracy of the sign language interpretation, the interpreter must be aware of the appearances of the lecturer and the contents of the lecture, and at the same time, the interpreter must look toward the audience. This research introduces a system which can be effective in a small classrooms or auditorium, by providing the maximum information about the lecturer and the contents of the lecture. Also, in order to verify the effectiveness of the proposed system, this research includes the discussions about the related systems and test methods. In conclusion, delivering the images of the lecturer and the contents of the lecture to the interpreter by employing the proposed system has been proved effective.

• 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.