• Architectural research
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• 제2권1호
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• pp.55-60
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• 2000

Recently, there is a great demand for precast reinforced concrete (RC) construction methods on the purpose of simplicity in construction. Nishimatsu Construction Company has developed a construction method with precast reinforced concrete members in medium-rise building. In this construction method, how to joint precast members, especially the anchorage of the main bar of beam, is important problem. In this study, the structural performance of exterior joints with precast members was investigated. The parameters of the test specimens are anchorage type of the main bar of beam (U-shape anchorage or anchorage plate) and the ratio of the column axial force to the column strength. Specimens J-3 and J-4 used U-shape anchorage and the ratio of the column axial force of specimen J-4 was higher. On the other hand, specimens J-5 and J-6 used anchorage plate, and the anchorage lengths are 15d and 18d, respectively. Experimental results are summarized as follows; 1) For the joints with beam flexural failure mode, it was found that the maximum strength of specimen with anchorage plate is equal to or larger than that of specimen with conventional U-shaped anchorage if the anchorage length of more than 15d would be ensured, 2) Each specimen shows stable hysteretic curves and there were no notable effects on the hysteretic characteristics and the maximum strength caused by the anchorage method of beam main bar and the difference of column axial stress level.

• Structural Engineering and Mechanics
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• 제59권5호
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• pp.867-883
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• 2016

In this paper, the effects of steel-fiber and rebar reinforcements on the ultimate bearing strength of the local anchorage zone were investigated based on experiments and comparisons between test results and design-equation predictions (AASHTO 2012, NCHRP 1994). Eighteen specimens were fabricated using the same anchorage device, which is one of the conventional anchorage devices, and two transverse ribs were used to secure an additional bearing area for a compact anchorage-zone design. Eight of the specimens were reinforced with only steel fiber and are of two concrete strengths, while six were reinforced with only rebars for two concrete strengths. The other four specimens were reinforced with both rebars and steel fiber for one concrete strength. The test and the comparisons between the design-equation predictions and the test results showed that the ultimate bearing strength and the section efficiency are highly affected by the reinforcement details and the concrete strength; moreover, the NCHRP equation can be conservatively applied to various local anchorage zones for the prediction of the ultimate bearing strength, whereby conditions such as the consideration of the rib area and the calibration factor are changed.

• 도시과학
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• 제7권2호
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• pp.21-27
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• 2018

With the increase of the skyscraper center, the development of large-diameter and high-strength reinforcing bars is being carried out to solve the dense reinforcement. In case of the steel reinforced concrete with a small cross section such as beam-column joints, the development length becomes short when straight bars are used. Therefore, it is possible to solve the problem that the development length becomes short by using the bearing strength of the hooked bar and headed bar. In this study, the exterior beam-column joint test of SD700 hooked bar and headed bar with anchorage length of 20db was conducted to extend the development length limitation of hooked bar and headed bar. As a result of the evaluation of the anchorage strength using the design equation by KCI, the average of the [measured value]/[predicted value] ratio was 1.31 for the hooked reinforcing bars. In the case of headed bars, the average of the [measured value]/[predicted value] ratio was 1.12. In addition, in order to compare the anchorage performance of the hooked bar and the headed bar, the measured values were divided by the square root of the compressive strength of the concrete to compare the anchorage strength. Under the same conditions, the anchorage strength of headed bars was 8.5% higher than the hooked bars.

• 한국공간구조학회논문집
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• 제18권3호
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• pp.117-124
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• 2018

In the post-tensioned concrete member, additional reinforcement is required to prevent failure in the anchorage zone. In this study, the details of reinforcement suitable for the anchorage zone of the post-tensioned concrete member using circular anchorage was proposed based on the experimental results. The tests were conducted with the compressive strength of concrete and reinforcement types as variables. The experimental results indicated that the additional reinforcement for the anchorage zone is required when the compressive strength of concrete is less than 17.5 MPa. U-shaped reinforcement shows most effective performance in terms of maximum strength and cracks patterns.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2000년도 봄 학술발표회 논문집
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• pp.657-662
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• 2000

This paper presents the results from experimental study that investigated to explore the load transfer characteristics of post-tensioning anchorage zones. The experimental program investigated the primary variables which affect the ultimate load, lateral strains and crack width: concrete compressive strength, details of reinforcement and shape of anchorage. Through this research, it was found that the governing factor of the ultimate load was not compressive cylinder strength but tensile splitting strength. Ultimate load was increased and lateral strain was decreased as the ratio of spiral increased because the lateral expansion of th concrete inside the spiral was restrained by the spiral. Furthermore, the shape of anchorage which can diminish the wedge effect of anchorage and disperse the anchorage force in various depths was more effective.

• Structural Engineering and Mechanics
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• 제41권3호
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• pp.407-420
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• 2012

This study investigated possible ways to replace conventional stirrups used on high-strength concrete members with improved reinforcing materials. Headed bar and high-strength steel were chosen to substitute for conventional stirrups, and an experimental comparison between the shear behavior of high-strength concrete large beams reinforced with conventional stirrups and the chosen stirrup substitutes was made. Test results indicated that the headed bar and the high-strength steel led to a significant reserve of shear strength and a good redistribution of shear between stirrups after shear cracking. This is due to the headed bar providing excellent end anchorage and the high-strength steel successfully resisting higher and sudden shear transmission from the concrete to the shear reinforcement. Experimental results presented in this paper were also compared with various prediction models for shear strength of concrete members.

• 한국산업융합학회 논문집
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• 제25권6_3호
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• pp.1165-1171
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• 2022

In this paper, the results of an experimental study were presented by measuring and comparing the flexural strength and deformation on the carbon fiber sheet strength reinforced concrete beam considering end anchorage effect. For this purpose, total six specimens of 100×100×600mm size were prepared and tested according to the KDS 14 20 20. The specimens were categorized in three cases as reference beams without strengthening, beams carbon fiber strengthened but not anchored and beams carbon fiber strengthened also anchored. Experimental results showed that the end anchorage contributed to increase the flexural strength about 42% greater than that of carbon fiber sheets alone, and the number and width of cracks were relatively increased. The results support a considerable effects of end anchorage for carbon fiber strengthened reinforced concrete beams in enhancing the flexural performance. Further studies are needed in durability and long term behavior of carbon fiber sheet strengthened reinforced concrete beams.

• 한국전산구조공학회논문집
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• 제28권3호
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• pp.317-324
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• 2015

프리스트레스 콘크리트 정착부의 설계를 위해 AASHTO 및 PTI에서 관련 설계식을 제안하고 있다. 그러나 이러한 설계식은 구조물의 긴장력이 단순 지압판을 통해 구조 전반으로 전달된다는 가정으로 유도된 것으로 실제 구조물에 적용되는 상용 정착구의 형태와는 차이가 있다. 이 논문에서는 하중전달 시험에 의한 실험적 방법과 3차원 고체요소를 사용한 비선형 유한요소해석 프로그램을 이용한 해석적 방법을 통해 정착구의 형상 변수에 따른 정착부의 거동특성 변화에 대한 연구를 수행하였다. 하중전달시험 결과에서 얻어진 하중변위 곡선 및 극한하중 값을 해석을 통해 얻은 결과와 비교하여 유한요소모델의 적합성을 확인하였다. 또한 정착구의 리브의 설치위치, 리브의 개수, 리브의 설치길이를 주요 변수로 설정하여 형상변수에 따른 매개변수 연구를 수행하였다.

• 콘크리트학회논문집
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• 제28권3호
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• pp.365-373
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• 2016

강섬유 보강 초고성능콘크리트(SUPER Concrete)는 일반 콘크리트에 비해 높은 압축강도와 인장강도를 지닌다. 이러한 특성으로 SUPER Concrete로 제작된 부재는 단면을 크게 줄일 수 있고, 확대머리철근의 정착강도가 향상될 것으로 기대된다. 이 연구에서는 120 MPa, 180 MPa SUPER Concrete로 제작된 외부 보-기둥 접합부에 $4d_b$, $6d_b$의 정착길이를 갖는 확대머리철근의 정착 성능을 평가하였다. 모든 실험체에서 600 MPa 이상의 실제 항복강도가 발현된 후 일부 실험체에서 측면파열파괴가 발생되었다. 확대머리철근의 정착강도가 매우 높아 철근이 파단되는 경우도 있었다. 설계기준강도 120 MPa 이상 SUPER Concrete에 정착된 확대머리철근은 $4d_b$의 짧은 정착길이로 콘크리트구조기준에서 허용하는 철근의 최대 설계기준강도 600 MPa를 발현할 수 있는 것으로 평가되었다. 기존에 개발된 일반 콘크리트에 정착된 확대머리철근의 측면파열파괴강도 평가식과 현행 콘크리트구조 기준의 확대머리철근 정착길이 설계식은 실험값을 과소평가하였다. 일반콘크리트에서 개발된 평가식은 SUPER Concrete의 높은 인장강도 특성을 반영하지 못하기 때문으로 분석된다. 확대머리철근 정착강도를 $(f_{ck})^{\alpha}$에 비례한다고 가정하고 실험결과를 회귀분석하여, SUPER Concrete 압축강도의 0.14승에 비례하는 정착강도 평가식이 개발되었다. 40개 실험 자료에 대한 [실험값]/[예측 값]의 평균은 1.01, 변동계수는 5%였다.

• 한국공간구조학회논문집
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• 제17권1호
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• pp.59-67
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• 2017

In this study, load transfer tests based on KCI-PS101 were conducted to verify the performance of spiral anchorage zone reinforcement for banded post-tensioning (PT) monostrands. With results, the compressive strength of spiral reinforcement was increased by about 20% than that of specimens with two horizontal steel bars and 8% than that of U-shaped bars. Advanced spiral reinforcement for corner increases compressive strength and can resist the spalling forces or fall-out effect at the corner by shear. The ratio of maximum load to amount of steel of the spiral reinforcement is about twice than that of U-shaped reinforcement. With increase of compressive strength capacity and improvement of constructability, the spiral reinforcement is considered to have advantages of promoting the performance of PT anchorage zone compared to conventional methods.