• Journal of Yeungnam Medical Science
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• 제34권2호
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• pp.200-207
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• 2017

Background: We conducted a systematic review of the literature to investigate the correlation between the interval to treatment and management of tendon avulsion ruptures in the musculotendinous junction (MTJ) of the forearm. Methods: A thorough literatures search for studies of tendon avulsion injuries at the forearm was conducted using PubMed, MEDLINE, CINAHL, and Cochrane databases in accordance with the PRISMA guidelines. In total, five case series and 15 case reports accounting for 87 injured tendons involving 60 patients were selected for the analysis. Results: Twenty-six patients had 44 tendon injuries associated with avulsion amputations, 31 patients had 38 tendon ruptures associated with closed avulsion injuries and three patients had five tendon ruptures associated with open avulsion injuries. Eighteen of the 49 (37%) patients were immediately treated for tendon ruptures and one of the 32 (3%) tendon ruptures treated via elective surgery was directly repaired. Additionally, 18 of the 30 (60%) tendons were directly repaired and 12 of the 30 (40%) tendons were transferred or side-to-side repaired in the immediately treated series. In contrast, one of the 28 (4%) tendon ruptures were directly repaired and 27 of the 28 (96%) tendons were transferred or side-to-side repaired in the electively treated series. Conclusion: In managing digital tendon avulsions at the MTJ, an immediate treatment could provide an opportunity to repair the ruptured tendon directly to the muscle.

• Nuclear Engineering and Technology
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• 제42권3호
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• pp.319-328
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• 2010

Bonded tendons have been used in reactor buildings at some operating nuclear power plants in Korea. Assessing prestress force on these bonded tendons has become an important pending problem in efforts to assure continued operation beyond their design life. The System Identification (SI) technique was thus developed to improve upon the existing indirect assessment technique for bonded tendons. As a first step, this study analyzed the sensitivity of the key parameters to prestress force, and then determined the optimal parameters for the SI technique. A total of six scaled post-tensioned concrete beams with bonded tendons were manufactured. In order to investigate the correlation of the natural frequency and the displacement to prestress force, an impact test, a Single Input Multiple Output (SIMO) sine sweep test, and a bending test using an optical fiber sensor and compact displacement transducer were carried out. These tests found that both the natural frequency and the displacement show a good correlation with prestress force and that both parameters are available for the SI technique to predict prestress force. However, displacements by the optical fiber sensor and compact displacement transducer were shown to be more sensitive than the natural frequency to prestress force. Such displacements are more useful than the natural frequency as an input parameter for the SI technique.

• Computers and Concrete
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• 제10권3호
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• pp.241-258
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• 2012

The need for long-span members increases gradually in recent years, which makes issues not only on ultimate strength but also on excessive deflection of horizontal members important. In building structures, the post-tension methods with unbonded tendons are often used for long-span members to solve deflection problems. Previous studies on prestressed flexural members with unbonded tendons, however, were mostly focused on the ultimate strength. For this reason, their approaches are either impossible or very difficult to be implemented for serviceability check such as deflection, tendons stress, etc. Therefore, this study proposed a flexural behavior model for post-tensioned members with unbonded tendons that can predict the initial behavior, before and after cracking, service load behavior and ultimate strength. The applicability and accuracy of the proposed model were also verified by comparing with various types of test results including internally and externally post-tensioned members, a wide range of reinforcement ratios and different loading patterns. The comparison showed that the proposed model very accurately estimated both the flexural behavior and strength for these members. Particularly, the proposed model well reflected the effect of various loading patterns, and also provided good estimation on the flexural behavior of excessively reinforced members that could often occur during reinforcing work.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1998년도 가을 학술발표대회 논문집(III)
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• pp.643-648
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• 1998

Despite many advantages of FRP materials, such as corrosion resistance, their linear elastic behavior up to rupture is likely to result in a lack of ductility. This paper discusses ductility improvement methods for prestressed concrete beams using FRP tendons. The methods were evaluated thorough extensive analytical and experimental investigations. The methods include optimization of sectional ductility through proper reinforcement, concrete confinement, concrete reinforcement with fibers, and prestressing with unbonded tendons.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2006년도 정기 학술대회 논문집
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• pp.445-450
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• 2006

It is proposed that the electromechanical relation of the conductive materials with high electrical resistance may be used to estimate the current stress of prestressing tendons. To choose the best conductive material to this end, we studied the electromechanical relations of carbon fibers and metalic heat wires experimentally. It is found that the relation of carbon fibers can be modelled by a parabolic(or hyperbolic) function in the early stage of deformation. However because the relation is not consistent when it is unloaded and reload, carbon fibers are not suitable for this purpose. Metallic heat wires show a consistent linear relation during loading and unloading in the elastic deformation and are suitable for this purpose. To estimate the electromechanics relation of metallic wires, we developed a simple formula based on the rigid plasticity. We propose a new kind of prestressing tendons whose stress can be monitored.

• International Journal of Concrete Structures and Materials
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• 제11권1호
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• pp.1-16
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• 2017

The compression or tension-controlled failure mode of concrete beams prestressed with unbonded FRP tendons is governed by the relative amount of prestressing tendon to the balanced one. Explicit assessment to determine the balanced reinforcement ratio of a beam with unbonded tendons (${\rho}^U_{pfb}$) is difficult because it requires a priori knowledge of the deformed beam geometry in order to evaluate the unbonded tendon strain. In this study, a theoretical evaluation of ${\rho}^U_{pfb}$ is presented based on a concept of three equivalent rectangular curvature blocks for simply supported concrete beams internally prestressed with unbonded carbon-fiber-reinforced polymer (CFRP) tendons. The equivalent curvature blocks were iteratively refined to closely simulate beam rotations at the supports, mid-span beam deflection, and member-dependent strain of the unbonded tendon at the ultimate state. The model was verified by comparing its predictions with the test results. Parametric studies were performed to examine the effects of various parameters on ${\rho}^U_{pfb}$.

• Structural Engineering and Mechanics
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• 제55권6호
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• pp.1099-1120
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• 2015

External prestressing has been applied to both new construction and retrofitting of existing reinforced and prestressed concrete structures. Continuous beams are preferred to simply supported beams because of economy, fewer movement joints and possible benefits from moment redistribution. However, this paper argues that continuous prestressed concrete beams with external unbonded tendons demonstrate different full-range behaviour compared to reinforced concrete (RC) beams. Applying the same design approach for RC to external prestressing may lead to design with a lower safety margin. To better understand the behaviour of continuous prestressed concrete beams with unbonded tendons, an experimental investigation is performed in which nine such specimens are tested to failure. The full-range behaviour is investigated with reference to moment-curvature relationship and moment redistribution. The amounts of moment redistribution measured in the experiments are compared with those allowed by BS 8110, EC2 and ACI 318. Design equations are also proposed to estimate the curvature ductility index of unbonded prestressed concrete beams.

• 콘크리트학회논문집
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• 제20권5호
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• pp.611-618
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• 2008

CFRP (carbon fiber reinforced polymer) 긴장재는 PS 강연선의 부식문제를 해결하기 위해 대안으로 사용될 수 있다. CFRP 긴장재는 횡방향 압력 및 응력집중에 취약하므로 기존의 PS 강연선에 적용되는 정착시스템의 적용은 조기파괴 등으로 인하여 믿을만한 내하성능을 주지 못한다. 따라서 CFRP 긴장재를 정착하기 위한 알맞은 정착장치의 개발이 필요하다. CFRP 긴장재용 정착구의 주된 형태는 쐐기형, 부착형 및 압착형으로 구분되며 이들 형태는 CFRP 긴장재에서 발생되는 조기파단을 방지하고 국부응력을 적절히 분산시키기 위한 목적으로 개발되고 있다. 본 논문은 CFRP 긴장재를 정착시키기 위해 압착형 정착방식을 적용하여 응력집중을 완화시키기 위해 슬리브 내외경에 변단면을 적용하고, 변단면 길이에 따른 압착형 정착구의 정착성능을 고찰하였다. 실험결과 정착구의 성능은 슬리브 제원과 압착력에 크게 좌우되는 것으로 나타났고, 응력완화구간을 갖는 슬리브는 응력집중을 감소시키는 것으로 나타났다.

• 콘크리트학회논문집
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• 제22권1호
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• pp.113-122
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• 2010

후 긴장된 PS 강재의 부식과 파단은 프리스트레스 콘크리트 교량의 안전에 매우 심각한 문제를 발생시키고 있다. 따라서 교량의 내하력 평가시 PS 강재의 부식 상태를 조사해야 하며, 부식된 PS 강재가 발견되는 경우, 부식에 의한 강재의 단면적 감소량을 극한강도 평가시 고려해야만 한다. 선행 연구에서는 연속음향감지기법을 그라우팅되고 후 긴장된 PS 강연선의 부식과 파단을 감지할 수 있는 신뢰할 만한 비파괴검사방법으로 평가하였다. 이 연구에서는 긴장재에 도입된 응력 수준이 현행 설계기준에 제시된 수준보다 낮게 도입된 PS 강연선에 대해 부식에 의한 강선 파단을 감지하기 위한 실험적 연구를 수행하였다. 이를 위해 프리스트레스의 크기가 각각 인장강도의 66%와 40%로 도입된 PS 강연선이 포함된 길이 10 m의 PSC 보를 제작하였다. 부식 촉진 장비를 이용하여 긴장재를 인위적으로 부식시켰으며, 7개의 음향센서와 연속음향감지장치를 이용하여 실험부재를 모니터링하였다. 부식 촉진 실험 동안 각 PS 강연선으로부터 2번의 강선 파단음파를 성공적으로 감지하였으며, 또한 오차범위 20 mm 이하로 음원 위치를 표정할 수 있었다. 이상의 실험 결과를 토대로 그라우팅되고 후 긴장된 PSC 보에서 발생되는 PS 강선 파단을 감지하는데 연속음향감지기법을 적용할 수 있다고 판단된다.

• Computers and Concrete
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• 제31권4호
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• pp.337-348
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• 2023

Shear wall is commonly used as a lateral force resisting system of concrete mid-rise and high-rise buildings, but it brings challenges in providing relatively large space throughout the building height. For this reason, the structure system where the upper structure with bearing, non-bearing and/or shear walls that sits on top of a transfer plate system supported by widely spaced columns at the lower stories is preferred in some regions, particularly in low to moderate seismic regions in Asia. A thick reinforced concrete (RC) plate has often been used as a transfer system, along with RC transfer girders; however, the RC plate becomes very thick for tall buildings. Applying the post-tensioning (PT) technique to RC plates can effectively reduce the thickness and reinforcement as an economical design method. Currently, a simplified model is used for numerical modeling of PT transfer plate, which does not consider the interaction of the plate and the upper structure. To observe the actual behavior of PT transfer plate under seismic loads, it is necessary to model whole parts of the structure and tendons to precisely include the interaction and the secondary effect of PT tendons in the results. This research evaluated the seismic behavior of shear wall-type residential buildings with PT transfer plates for the condition that PT tendons are included or excluded in the modeling. Three-dimensional finite element models were developed, which includes prestressing tendon elements, and response spectrum analyses were carried out to evaluate seismic forces. Two buildings with flat-shape and L-shape plans were considered, and design forces of shear walls and transfer columns for a system with and without PT tendons were compared. The results showed that, in some cases, excluding PT tendons from the model leads to an unrealistic estimation of the demands for shear walls sit on transfer plate and transfer columns due to excluding the secondary effect of PT tendons. Based on the results, generally, the secondary effect reduces shear force demand and axial-flexural demands of transfer columns but increases the shear force demand of shear walls. The results of this study suggested that, in addition to the effect of PT on the resistance of transfer plate, it is necessary to include PT tendons in the modeling to consider its effect on force demand.