• Geomechanics and Engineering
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• v.10 no.6
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• pp.737-755
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• 2016

The load transfer depth of a ground anchor is the minimum length required to transfer the initial prestressing to the grout column through the bonded part. A thorough understanding of the mechanism of load transfer as well as accurate prediction of the load transfer depth are essential for designing an anchorage that has an adequate factor of safety and satisfies implicit economic criteria. In the current research, experimental and numerical studies were conducted to investigate the load transfer mechanism of ground anchors based on a series of laboratory and field load tests. Optical FBG sensors embedded in the central king cable of a seven-wire strand were successfully employed to monitor the changes in tensile force and its distribution along the tendons. Moreover, results from laboratory and in-situ pullout tests were compared with those from equivalent case studies simulated using the finite difference method in the FLAC 3D program. All the results obtained from the two proposed methods were remarkably consistent with respect to the load increments. They were similar not only in trend but also in magnitude and showed more consistency at higher pullout loading stages, especially the final loading stage. Furthermore, the estimated load transfer depth demonstrated a pronounced dependency on the surrounding ground condition, being shorter in hard ground conditions and longer in weaker ones. Finally, considering the safety factor and cost-effective design, the required bonded length of a ground anchor was formulated in terms of the load transfer depth.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07b
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• pp.1274-1277
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• 2004

최근 에너지 소비구조의 선진화에 따라 전력수요는 매년 10%이상 증가하고 있지만 철탑부지확보 및 환경 문제 둥에 의해 신규 송전선의 건설은 점차 어려워지고 있다. 이에 대한 대책으로 철탑의 교체 없이 송전선의 전류용량간 증가시키는 방안이 우선적으로 고려되어 적용되고 있다. 이미 국내에서도 기존 송전선인 ACSR 전선을 중용량 저이도의 특성을 가진 STACIR/AW(Super Thermal-resistant Aluminum alloy Conductors, aluminum-clad Invar-Reinforced)송전선으로 교체하여 전력 수송량을 증가시키고 있다. STACIR/AW전선은 도체의 내열성을 향상시켜 연속허용온도$(210^{\circ}C)$를 높임으로 전류용량을 증가시키고, ACSR에 사용되는 강심재료인 고탄소강선을 선팽창계수가 낮은 인바강선(INVAR)으로 대체함으로 고온환경에 따른 이도증가를 방지하고 있다. 그러나 STACIR/AW 송전선은 ACSR 송전선에 비하여 연속허용온도가 높고 경간의 거리가 멀기 때문에 열화에 의한 피로특성의 변화 가능성이 높다. 따라서 본 연구에서는 증용량저이도전선의 강심소재인 INVAR/AW강선을 소정의 온도에서 경년 열화하고, 열화시간에 따른 강도와 피로특성의 변화를 조사하여, STACIR/AW전선의 안정적 운전을 위한 재료물성적 관리인자를 도출하고자 하였다.

• Smart Structures and Systems
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• v.7 no.4
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• pp.303-317
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• 2011

A specially designed tendon, which is proposed by embedding an FBG sensor into the center king cable of a 7-wire strand tendon, was applied to monitor the prestress force and load transfer of ground anchor. A series of tensile tests and a model pullout test were performed to verify the feasibility of the proposed smart tendon as a measuring sensor of tension force and load transfer along the tendon. The smart tendon has proven to be very effective for monitoring prestress force and load transfer by measuring the strain change of the tendon at the free part and the fixed part of ground anchor, respectively. Two 11.5 m long proto-type ground anchors were made simply by replacing a tendon with the proposed smart tendon and prestress forces of each anchor were monitored during the loading-unloading step using both FBG sensor embedded in the smart tendon and the conventional load cell. By comparing the prestress forces measured by the smart tendon and load cell, it was found that the prestress force monitored from the FBG sensor located at the free part is comparable to that measured from the conventional load cell. Furthermore, the load transfer of prestressing force at the tendon-grout interface was clearly measured from the FBGs distributed along the fixed part. From these pullout tests, the proposed smart tendon is not only expected to be an alternative monitoring tool for measuring prestress force from the introducing stage to the long-term period for health monitoring of the ground anchor but also can be used to improve design practice through determining the economic fixed length by practically measuring the load transfer depth.

• The Journal of Engineering Geology
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• v.30 no.4
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• pp.673-682
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• 2020

The ground shear force at the expected failure surface and resistance force due to reinforced anchor can act as important factors according to a failure type from the stability viewpoint at a slope. Furthermore, the anchor's axial force may vary at an anchor-reinforced slope due to ground weathering, settlement, and corrosion in the incompletely anti-corrosion treated steel wire strand at a ground where the bearing plate is installed. However, in case that the resistance force of the anchor is locally lost due to the variation of the anchor's axial force, the resistance force may not play the role so that the external force tends to be transferred to the surrounding anchors, causing an increase in the tensile force in the surrounding anchors. Accordingly, a stability problem at the entire slope may occur, which requires much attention. Thus, this study proposed a method to monitor a variation trend of the tensile force of anchors installed at a slope and infer the external stability at the entire slope considering the monitoring result.

• Journal of the Earthquake Engineering Society of Korea
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• v.28 no.3
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• pp.129-139
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• 2024

In this study, the SBC system, a new mechanical joint method, was developed to improve the constructability of precast concrete (PC) beam-column connections. The reliability of the finite element analysis model was verified through the comparison of experimental results and FEM analysis results. Recently, the intermediate moment frame, a seismic force resistance system, has served as a ramen structure that resists seismic force through beams and columns and has few load-bearing walls, so it is increasingly being applied to PC warehouses and PC factories with high loads and long spans. However, looking at the existing PC beam-column anchorage details, the wire, strand, and lower main bar are overlapped with the anchorage rebar at the end, so they do not satisfy the joint and anchorage requirements for reinforcing bars (KDS 41 17 00 9.3). Therefore, a mechanical joint method (SBC) was developed to meet the relevant standards and improve constructability. Tensile and bending experiments were conducted to examine structural performance, and a finite element analysis model was created. The load-displacement curve and failure pattern confirmed that both the experimental and analysis results were similar, and it was verified that a reliable finite element analysis model was built. In addition, bending tests showed that the larger the thickness of the bolt joint surface of the SBC, the better its structural performance. It was also determined that the system could improve energy dissipation ability and ductility through buckling and yielding occurring in the SBC.

• Journal of the Korean Geotechnical Society
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• v.28 no.5
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• pp.13-25
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• 2012

Ground anchor method is one of the most popular reinforcing technology for slope in Korea. For the health monitoring of slope which is reinforced by permanent anchor for a long period, monitoring of the tension force of ground anchor is very important. However, since electromechanical sensors such as strain gauge and V/W type load cell are also subject to long-term risk as well as suffering from noise during long distance transmission and immunity to electromagnetic interference (EMI), optical FBG sensors embedded tendon was developed to measure strain of 7-wire strand by embedding FBG sensor into the center king cable of 7-wire strand. This FBG sensors embedded tendon has been successfully applied to measuring the short-term anchor force. But to adopt this tendon to long-term monitoring, temperature compensation of the FBG sensors embedded tendon should be done. In this paper, we described how to compensate the effect in compliance with the change of underground temperature during long-term tension force monitoring of ground anchors by using optical fiber sensors (FBG: Fiber Bragg Grating). The model test was carried out to determine the temperature sensitivity coefficient (${\beta}^{\prime}$) of FBG sensors embedded tendon. The determined temperature sensitivity coefficient ${\beta}^{\prime}=2.0{\times}10^{-5}/^{\circ}C$ was verified by comparing the ground temperatures predicted from the proposed sensor using ${\beta}^{\prime}$ with ground temperatures measured from ground thermometer. Finally, temperature compensations were carried out based on ${\beta}^{\prime}$ value and ground temperature measurement from KMA for the tension force monitoring results of tension type and compression type anchors, which had been installed more than 1 year before at the test site. Temperature compensated tension forces are compared with those measured from conventional load cell during the same measuring time. Test results show that determined temperature sensitivity coefficient (${\beta}^{\prime}$) of FBG sensors embedded tendon is valid and proposed temperature compensation method is also appropriate from the fact that the temperature compensated tension forces are not dependent on the change of ground temperature and are consistent with the tension forces measured from the conventional load cell.

• Journal of the Korea institute for structural maintenance and inspection
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• v.28 no.4
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• pp.21-27
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• 2024

In this study, the corrosion density of tendon was evaluated with changing chloride and hydroxide ions. To simulate an accelerated corrosive environment, wet sand was used instead of concrete, and the tests were conducted considering three levels of chloride concentration (0.0, 0.125, and 0.250mol/l ) and three [Cl^-]/[OH^-] ratios (0.3, 0.6, and 0.9). The corrosion density was measured to 5.13 µA/cm² at 0.0mol/l and increased with the chloride concentration. Additionally, no significant differences were observed over 0.125mol/l of chloride concentration. When [OH^-] increased with a given chloride concentration (0.125mol/l), the corrosion density decreased linearly, showing effective control of corrosion density even at high chloride concentrations. Notably, the measured corrosion amounts were lower than those under of 0.0mol/l condition. Furthermore corrosion density and influencing parameters were normalized with the maximum and minimum results, and the relation between them was analyzed.

• Journal of Preventive Medicine and Public Health
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• v.31 no.1 s.60
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• pp.15-26
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• 1998

p53 is the most frequently mutated gene in female breast cancer tissues and the prognosis of breast cancer could be changed by mutation of the gene. This study was performed to examine risk factors for breast cancer subtypes classified by p53 mutation and to investigate the roles of p53 gene mutation in carcinogenesis of breast cancer. The study subjects were 81 breast cancer patients and 121 controls who were matched to cases 1:1 or 1:2 age, residence, education level and menopausal status. All the subjects were interviewed by a well-trained nurse with standardized questionnaire on reproductive factors, and wire asked to fill the self-administrative food frequency questionnaire. p53 gene mutation in the cancer tissue was screened using polymerase chain reaction (PCR)-single strand conformational polymorphism (SSCP) method. Mutation type was identified by direct sequencing of the exon of which mobility shift was observed in SSCP analysis. Mutations were detected in p53 gene of 25 breast cancer tissues. By direct sequencing, base substitutions were found in 20 cancer tissues (10 transition and 10 transversion), and frame shift mutations in 5 (4 insertions and 1 deletion). For the whole cases and controls, risk of breast cancer incidence decreased when the parity increased, and increased when intake amount of total calory, fat, or protein increased. Eat and protein were statistically significant risk factors for breast cancer with p53 mutation. For breast cancer without p53 mutation, protein intake was the only significant dietary factor. These results suggest that causes of p53 positive breast lancer would be different from those of p53 negative cancer, and that dietary factors or related hormonal factors induce mutation of p53, which may be the first step of breast cancer development or a promoter following some unidentified genetic mutations.

• Korean Journal of Heritage: History & Science
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• v.46 no.2
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• pp.4-25
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• 2013

Goli-su is the innovative special kind of the embroidery technique, which combines twining and interlacing skill with metal technology and makes the loops woven to each other with a strand. The loops floating on the space of the ground look like floating veins of sculpture and give people the feeling of the openwork. This kind of characteristic has some similarities with the lacework craft of Western Europe in texture and technique style, but it has its own features different from that of Western Europe. It mainly represents the splendid gloss with metallic materials in the Embroidered cloth, such as gold foil or wire. In the 10th century, early days of Goryo, we can see the basic Goli-su structure form of its initial period in the boy motif embroidery purse unearthed from the first level of Octagonal Nine-storied Pagoda of Woljeong-sa. In the Middle period of Joseon, there are several pieces of Goli-su embroidered relic called "Battle Flag of Goryo", which was taken by the Japanese in 1592 and is now in the Japanese temple. This piece is now converted into altar-table covers. In 18~19th century, two pairs of embroidered pillows in Joseon palace were kept intact, whose time and source are very accurate. The frame of the pillows was embroidered with Goli-su veins, and some gold foil papers were inserted into the inside. The triangle motif with silk was embroidered on the pillow. The stitch in the Needle-Looped embroidery is divided into three kinds according to comprehensive classification: 1. Goli-su ; 2. Goli-Kamgi-su ; 3. Goli-Saegim-su. From the 10th century newly establishing stage to the 13th century, Goli-su has appeared variational stitches and employed 2~3 dimensional color schemes gradually. According to the research of this thesis, we can still see this stitch in the embroidery pillow, which proves that Goli-suwas still kept in Korea in the 19th century. And in terms of the research achievement of this thesis, Archetype technology of Goli-su was restored. Han Sang-soo, Important Intangible Cultural Heritage No. 80 and Master of Embroidery already recreated the Korean relics of Goli-su in Joseon Dynasty. The Needle-Looped embriodery is the overall technological result of ancestral outstanding Metal craft, Twining and Interlacing craft, and Embroidery art. We should inherit, create, and seek the new direction in modern multi-dimensional and international industry societyon the basis of these research results. We can inherit the long history of embroidering, weaving, fiber processing, and expand the applications of other craft industries, and develop new advanced additional values of new dress material, fashion technology, ornament craft and artistic design. Thus, other crafts assist each other and broaden the expressive field to pursue more diversified formative beauty and beautify our life abundantly together.