• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2004년도 춘계 학술발표회 제16권1호
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• pp.438-441
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• 2004

This paper presents the results of the experimental study on the performances of reinforced concrete beams rehabilitated by external unbonded high tension steel-bar. Design variables for the experiment in this study includes the position of anchorage zone of the high tension steel bar, the anchorage length of the reinforcing steel bar and the types of the shear strengthening measures. 5 specimens were tested with one point monotonically increased loads and structural performances such as strength capacities, ductility capacities and failure modes were analysed. It is found that the structural performance of the rehabilitated beams are strongly depended on the location of anchorage zone of the high tension steel-bars. In the case that anchorage zone is located near the critical shear zone, it is observed that the rehabilitated beam is failed in brittle failure mode and the additional shear strengthening is necessitated. But if anchorage zone is properly located or additional shear strengthening device is provided properly, it is also observed that the strength capacity of the rehabilitated beams could be increased more than $200\%$ by the proposed method.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2008년도 추계 학술발표회 제20권2호
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• pp.185-188
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• 2008

플랫 플레이트 시스템은 펀칭전단과 같은 구조적 취약점이 있다. 펀칭전단의 저항력은 기둥단면의 증가, 슬래브 유효춤의 증가, 콘크리트 강도의 증가, 휨철근의 증가로 증가시킬 수 있다. 그러나 전단보강체를 설치하는 방법이 경제적, 시공적, 안정적으로 가장 좋은 방법이다. 하지만 슬래브 두께가 250mm보다 작은 슬래브에서는 전단보강체의 충분한 정착길이를 확보할수 없기 때문에 충분한 정착효과를 발휘하기 힘들다. 이전 연구에서 제안된 전단보강체의 경우 상부철근과 하부철근의 사이에 설치되었기 때문에 전단철근의 항복강도에 도달하기 전에 미끄러짐 파괴가 발생하였다. 정착강도의 영향을 주는 요인으로는 유효정착길이, 콘크리트강도, 전단철근의 직경, 정착상세이다. 본 연구에서는 슬래브 두께와 콘크리트 강도를 고려하여 제안된 보강체의 강도산정시 K factor를 제안하였다. 정착길이와 콘크리트강도를 고려함으로써 두께가 얇은 플랫플레이트 슬래브내에서 전단철근에 의한 전단강도를 정확히 산정할수 있을 것으포 판단된다..

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 추계 학술발표회 논문집
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• pp.269-272
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• 2006

The anchorage zone of prestressed concrete members is a critical region where a large concentrated force due to prestressing by tendons is introduced. In this study, the ACI, AASHTO LRFD, CEB-FIP design criteria and the nonlinear strut-tie model approach are applied to the ultimate strength analysis of simple anchorage zones of 18 post-tensioned concrete members tested to failure. From the result of ultimate strength analysis, the advantages and disadvantages of each method are compared and discussed.

• 한국구조물진단유지관리공학회 논문집
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• 제24권1호
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• pp.148-156
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• 2020

본 논문은 강섬유 보강 콘크리트 부재에 수직으로 기계적 정착된 고강도 확대머리철근의 정착성능을 평가하기 위하여 실시한 기초 인발실험결과를 정리한 것이다. 주요 실험변수는 강섬유의 혼입률, 콘크리트 강도, 정착길이, 확대머리철근 항복강도, 전단보강유무 등이다. 실험체의 좌우 순피복두께는 확대머리철근 직경의 두 배로 계획하였다. 확대머리철근을 중심으로 1.5𝑙_dt, 0.7𝑙_dt가 되는 위치에 힌지 지점을 두고, 확대머리 철근을 직접 인발하였다. 인발실험결과, 실험변수에 따라 콘크리트 파괴 및 철근 인장파단이 나타났다. 강섬유를 보강한 실험체가 동일한 변수의 강섬유를 보강하지 않은 실험체에 비히여 콘크리트 압축강도는 2.7~5.4% 크게 나타난 반면 인발강도는 20.9~63.1% 크게 나타나 정착성능 향상에 큰 기여를 하는 것으로 평가되었다. 강섬유 보강 콘크리트에 대해 확대머리철근과 평행한 전단보강근의 배근은 1.7~7.7% 인발강도를 증가시켰으나, 콘크리트 강도 증가를 고려할 때 정착성능 향상에 미치는 영향이 크지 않았다. 본 실험체 상세와 같이 강섬유보강 콘크리트 부재에 수직정착된 SD600의 확대머리철근 정착설계는 KCI2017, KCI2012의 정착길이 설계식을 그대로 사용할 수 있을 것으로 사료된다.

• KCI Concrete Journal
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• 제14권2호
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• pp.86-91
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• 2002

This paper presents an experimental study to investigate the behavior of mechanical anchorage of reinforcing bars in concrete members. Three kinds of mechanical anchorage which are a kind of headed reinforcements are considered in this study. Total seven specimens were prepared to consider the effects of anchoring methods (Type A, Type B and Type C) and anchorage lengths of the reinforcing bars (14 $d_{b}$, 12 $d_{b}$, 9 $d_{b}$). Pullout tests conforming to ASTM were carried out to assess the effects of several variables on anchoring strength of bars. Based on the test results, it was concluded that the behavior of the specimen anchored by the mechanical anchorage with the anchor-age length of 12 $d_{b}$, is as good as, or better than that of the specimen anchored by 90-degree standard hook.rd hook.

• International Journal of Concrete Structures and Materials
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• 제10권2호
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• pp.149-161
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• 2016

This paper presents an experimental work to study the flexural strength of reinforced concrete (RC) beams strengthened by partially de-bonded near surface-mounted (NSM) fiber reinforced polymer (FRP) strip with various de-bonded length. Especially, considering high anchorage capacity at end of a FRP strip, the effect of de-bonded region at a central part was investigated. In order to check the improvement of strength or deformation capacity when the bonded surface area only increased without changing the FRP area, single and triple lines of FRP were planned. In addition, the flexural strength of the RC member strengthened by a partially de-bonded NSM FRP strip was evaluated by using the existing researchers' strength equation to predict the flexural strength after retrofit. From the study, it was found that where de-bonded region exists in the central part of a flexural member, the deformation capacity of the member is expected to be improved, because FRP strain is not to be concentrated on the center but to be extended uniformly in the de-bonded region. Where NSM FRP strips are distributed in triple lines, a relatively high strength can be exerted due to the increase of bond strength in the anchorage.

• 한국구조물진단유지관리공학회 논문집
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• 제2권2호
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• pp.202-208
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• 1998

To investigae the effect of anchorage type of carbon fiber sheet (CFS) on flexural behavior of RC beams, the loading test of RC beams reinforced with CFS was conducted in variable of anchorage Type such as bolting anchorage and U type anchorage using CFS. This study can be summarized as follows ; It is confirmed experimentally that the bolting anchorage and U type anchorage with CFS is very effective to delay the bond failure and prevent the peeling of CFS. Also, the anchorage type applied with this study is very effective to improve the ductility compared with the improving of maximum flexural strength of RC beams. It is believed that the anchorage type used this study must secure the ductile capacity of above 3 for the flexural strengthening of RC beams. In the future, it is required to obtain the data about anchorage type of CFS for utilization of field work as well as investigate the ductile capacity of conventional study of anchorage type

• Geomechanics and Engineering
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• 제11권6호
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• pp.787-803
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• 2016

DDARF (Discontinuous Deformation Analysis for Rock Failure) is a numerical algorithm for simulating jointed rock masses' discontinuous deformation. While its reinforcement simulation is only limited to end-anchorage bolt, which is assumed to be a linear spring simply. Here, several new reinforcement modes in DDARF are proposed, including lining reinforcement, full-length anchorage bolt and equivalent reinforcement. In the numerical simulation, lining part is assigned higher mechanical strength than surrounding rock masses, it may include multiple virtual joints or not, depending on projects. There must be no embedding or stretching between lining blocks and surrounding blocks. To realize simulation of the full-length anchorage bolt, at every discontinuity passed through the bolt, a set of normal and tangential spring needs to be added along the bolt's axial and tangential direction. Thus, bolt's axial force, shearing force and full-length anchorage effect are all realized synchronously. And, failure criterions of anchorage effect are established for different failure modes. In the meantime, from the perspective of improving surrounding rock masses' overall strength, a new equivalent and tentative simulation method is proposed, it can save calculation storage and improve efficiency. Along the text, simulation algorithms and applications of these new reinforcement modes in DDARF are given.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2001년도 가을 학술발표회 논문집
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• pp.179-184
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• 2001

The objective of this study is to clarify the seismic capacity and the characteristics in the hysteretic behavior of RC structures with nonseismic detailing. To do this, an exterior beam-column subassemblage was selected from a 10-story RC building and 6 1/3-scale specimens were manufactured with 3 variables; ⑴ with and without slab, ⑵ upward and downward direction of anchorage for the bottom bar in beams, and ⑶ with and without hoop bars in the joint region. The test results have shown that ⑴ the existence of slab increased the strength in positive and negative moment, 25% and 62%, respectively; ⑵ the Korean practice of anchorage (downward and 25 $d_{b}$ anchorage length) caused the 8% reduction of strength and the early strength degradation when compared with the case of seismic details; and ⑶ the existence of hoop bars in the joint region does not show significant difference because the size of column is much larger than that of beam.m.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2005년도 봄학술 발표회 논문집(I)
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• pp.327-330
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• 2005

Bond failure of reinforcing bar generally take place by splitting of the concrete cover as bond force between concrete and reinforcing bars exceeds the confinement of the concrete cover and reinforcement. However, the confinement force in practice has a limitation. Thus, the only variable is the bearing area corresponding to the change of bond force. In this study, to the evaluate anchorage strength of high relative rib area bars, hook bond test specimens are tested and the results are discussed. Higher rib height bars when bars are confined showed higher anchorage strength than lower rib higher bars.