• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1999년도 봄 학술발표회 논문집(I)
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• pp.393-398
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• 1999

The main objective of this project is to define the ultimate bond performance of domestic prestressing strands in the precast prestensioned concrete beams. Eight specimens from four different companies were fabricated and tested in this study. Four-point loading tests were performed on the beams of domestic strands with an arbitrary anchorage length. The research has shown, that all seven specimens except one failed in bond are capable of developing their full flexural capacity and the strands within them are fully anchored even with the sudden transfer of frame cutting. Following results are summarized from the tests conducted. 1) All of the specimens are tested at an embedment lengths much shorter than those required by the ACI code, failed in flexure except one failed in bond. 2) It seems that the beam depth can not be an effective variable to estimate the bond length within these sections and length of specimens on this tests. 3) The development length with the stirrup space which are considered for correction factors in the equations of Russel and Paulsgrove, is fully accurate to determine the required length for the beam tested in this research.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2009년도 춘계 학술대회 제21권1호
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• pp.87-88
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• 2009

본 연구에서는 ACI-01에 제시되지 않은 앵커볼트 직경($d_0$) 50mm($2^''$) 이상, 유효매입깊이($h_{ef}$) 635mm($25^''$) 이상의 대형콘크리트앵커의 전단성능 및 거동특성에 대한 24가지 실험을 수행하였다. 실험을 통하여 전단강도와 거동특성에 영향을 주는 요인을 분석하였다.

• Computers and Concrete
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• 제1권4호
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• pp.401-416
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• 2004

This paper presents investigation of a three-dimensional (3-D) nonlinear finite element model analysis to examine the behavior of reinforced concrete beams strengthened with Carbon Fiber Reinforced Polymer (CFRP) composites to enhance the flexural capacity and ductility of the beams. Three-dimensional nonlinear finite element models were developed between the internal reinforcement and concrete using a smeared relationship. In addition, bond models between the concrete surface and CFRP composite were developed using a smeared bond for general analyses and a contact bond for sensitivity analyses. The results of the FEA were compared with the experimental data on full-scale members. The results of two finite-element bonding models showed good agreement with those of the experimental tests.

• International Journal of Concrete Structures and Materials
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• 제5권1호
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• pp.43-48
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• 2011

This paper presents the performance of anchor systems for reinforced concrete beams retrofitted with carbon fiber reinforced polymer (CFRP) strips. Nine simply-supported beams are tested with various anchor systems such as steel hooks, steel plates with anchor bolts, CFRP anchor plates, and near-surface mounted (NSM) CFRP strip. The effects of these anchors on the behavior of the retrofitted beams are discussed, including load-carrying capacity, failure modes, and ductility characteristics. Test results indicate that end-anchorage is an important parameter when a CFRP-retrofit design is conducted. Mechanical bolts and NSM CRFP anchors are recommended.

• 비파괴검사학회지
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• 제31권6호
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• pp.616-625
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• 2011

Ensuring the designed prestress force is very important for the safety of prestressed concrete bridge. The loss of prestress force in tendon could significantly reduce load carrying capacity of the structure. In this study, an automated prestress-loss monitoring system for prestressed concrete girder using PZT-interface and wireless impedance sensor node is presented. The following approaches are carried out to achieve the objective. Firstly, wireless impedance sensor nodes are designed for automated impedance-based monitoring technique. The sensor node is mounted on the high-performance Imote2 sensor platform to fulfill high operating speed, low power requirement and large storage memory. Secondly, a smart PZT-interface designed for monitoring prestress force is described. A linear regression model is established to predict prestress-loss. Finally, a system of the PZT-interface interacted with the wireless sensor node is evaluated from a lab-scale tendon-anchorage connection of a prestressed concrete girder.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2018년도 춘계 학술논문 발표대회
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• pp.99-100
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• 2018

Because of the congestion problems, the high-strength reinforcements are expected to be used in nuclear power plant structures in the near future. According to ACI 349-13, it is permitted to use the high-strength(550MPa) hooked bars in design of development length, but there is no special equation for high-strength bars. In order to reflect the anchorage capacity and behavior properties of high-strength bars with large-diameter(43 & 57mm), it is necessary to develope the new development length equation for large-size and high-strength bars.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1998년도 가을 학술발표대회 논문집(III)
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• pp.815-820
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• 1998

Many composite girder bridges have been constructed for about thirty five years. Nowadays they are aged or deteriorated because of th increase in traffic and vehicle loads. In this study, the effect of strengthening with glass fiber sheet is investigated to estimate the possibility for appling for damaged prestressed concrete bridges. One normal and eight cracked specimens which had been preloaded were tested. The cracked specimens were strengthened with either external prestressing or bonding glass fiber sheet, or using both methods. The results showed that the maximum loads are almost same for both methods. So it seems that the strengthening with glass fiber sheet can be used for strengthening damaged prestressed concrete girders. It is important that proper devices should be selected to prevent glass fiber sheet from premature bonding failure below its maximum load, which is similar to end anchorage problem in external prestressing method. It is proved that the devices proposed in this paper have sufficient anchoring capability to increase load carrying capacity.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2018년도 추계 학술논문 발표대회
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• pp.110-111
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• 2018

Because of the congestion problems, the high-strength reinforcements are expected to be used in nuclear power plant structures in the near future. According to ACI 349-13, it is permitted to use the high-strength(550MPa) straight bars in design of development length, but there is no special equation for high-strength bars. In order to reflect the anchorage capacity and behavior properties of high-strength straight bars with large-diameter(43 & 57mm), it is necessary to find the modified factor or develop the new development length equation for large-size and high-strength bars.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2004년도 추계 학술발표회 제16권2호
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• pp.17-20
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• 2004

FRP strengthening system that bonds FRP sheet or laminate underneath structure has been used popularly thesedays. The failure of this bonding system occurs mainly at the interface of bonded surface abruptly. So it is difficult to expect the failure and FRP can't show its full material capacity that makes it uneconomically. By that reason, KICT proposed a system to install FRP aminate to structure for strengthening not by bondging but by unbonding. It is to install both ends of FRP laminate by anchoring underneath structure without bonding. Then, the failure is not an interfacial problem any more, it is governed by mechanical anchoring. This paper includes an experimental study about anchoring system for prestressing CFRP laminate.

• 한국구조물진단유지관리공학회 논문집
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• 제7권3호
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• pp.125-131
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• 2003

본 연구에서는 최근 구조물 보강을 위해 사용이 증가하고 있는 CFRP로 보강된 철근콘크리트 보의 휨거동 특성을 분석하였다. 실험변수로 보강길이와 폭, 철근비, 단부정착 여부 그리고 무보강 기준실험체의 예상 극한하중의 75%에 상응하는 사전하중 여부를 고려하였으며, 각각의 실험변수에 따른 영향을 분석하였다. 이를 위해, 총 20개의 철근콘크리트 보를 제작하고 실험을 수행하였으며, 실험변수에 따른 극한하중, 처짐, CFRP의 변형률 그리고 파괴모드의 변화 특성에 대해 연구하였다.