In this paper, anchorage behavior of high-strength headed rebar with minimum edge distance was evaluated. The experimental parameters are the compressive strengths of concrete, the strengths and the anchorage lengths of headed rebar. The maximum pullout strengths and final failure modes were evaluated through the experiment.

The purpose of this paper is to assess the effect of surface characteristic of GFRP rebar on concrete-reinforcement bond behavior. For sample preparation, 10 GFRP rebar with two types of surface conditions were used to fabricate 15×15×15cm sized GFRP reinforced concrete. Then, pull-out test was carried out on each concrete samples until the maximum bond strength was achieved. From the test result, it was found that the maximum bond strength at the lattice type is 1.38 times higher than that for unidirectional surface.

최근 철근 콘크리트 구조물에 다양한 철근 이음이 사용되고 있다. 이에 따라 커플러 이음 철근의 인장 특성에 대한 파악이 중요해졌 다. 본 연구에서는 커플러 이음 철근의 연성도에 대한 평가를 위하여 ASTM A615 기준에 따라 생산된 Grade 60 D22(#7), D29(#9), 그리고 두 종류의 커플러를 상대로 1축 인장시험을 수행하였다. 보다 정확하고 다양한 지점에서 자유로운 계측이 가능한 이미지 프로세싱 방법을 사용하 여 변형률을 계측하였다. 1축 인장시험 결과, 응력-변형률 관계와 응력 단계별 종방향 변형률 분포를 산출할 수 있었고, 이를 통하여 동일한 표 점거리 내에서 커플러 이음 부분이 많이 차지할수록 평균변형률이 낮아지는 것을 알 수 있었다. 또한 커플러 이음철근의 극한거동 및 파단 시 변형률에 대한 평가를 통해 커플러의 길이에 대한 한계상태변형률과 파단변형률과의 상관관계를 정식화하였다.

The purpose of this study is to evaluate the tensile strength of GFRP and BFRP Rebar after exposure to environmental factors of deterioration (alkali, freezing -thawing) in order to present that as basic data for the application of FRP Rebar as concrete reinforcement. As a result, in the exposure of an alkali environment, the deterioration of fiber-resin was accelerated as the temperature increased, and it was found that there was an insignificant effect on freezing-thawing.

In this study, the behavior of column rebar in non-reinforced specimens (BF) was evaluated as part of the development of seismic retrofitting systems for public buildings such as school buildings. This is a very useful work because it can show the deformation state of the main bars according to the hysteretic behavior of lateral loads. When yielding the specimen, the main bar was yielded. and the deformation of stirrup at the inflection point position hardly occurred. These results will be used as a key index to evaluate the yield state of the structure from the deformation comparison of the reinforced specimens.

In this study, collision analysis of overlay concrete median barrier under truck load was conducted depending on location of rebar and shear key. Obtained results indicates that the impact resistances of overlay concrete median barrier was improved as the rebar and shear keys are more closed to the top surface of the CMB.

In this study, Corrosion behavior in mortar was observed by the passage of time by using EIS method. As a result of EIS experiment, equivalent circuit and changes of Impedance parameter could be observed. In addition, it was confirmed that impedance of rebar in concrete and corrosion rate according to the amount of NaCl and LiNO2 were different.

The maximum bond strength of PCS-coated rebar with ultra high-early strength cement and EVA at polymer-cement ratio of 80%, curing ages of 7-day, and coating thickness of 100㎛ is about 1.32 and 1.38 times respectively, the strength of uncoated rebar and epoxy-coated rebar. It is also high bond strength at coating thicknesses of 75㎛ and 100㎛ compared with 150㎛ and 250㎛. It is apparent in this study that the coating thickness is very important factors to improve the bond strength of PCS-coated rebar to cement concrete.

In the sliding slab track of railway bridge, a lateral support block is used to control the lateral displacement. Therefore, it is important to analyze the behavior of dowel rebar and the lateral support block of the sliding slab track. In this study, high strength concrete and steel rebar was selected to analyze the behavior of dowel rebar and shear behavior of high strength dowel rebar and the lateral support block were compared to the equations developed by Soroushian et al. (1986) and CEB-FIP (2010).

In this study, the 1-directional tension tests were conducted to evaluate ductility capacity of splice rebar. As a result, the ductility of the reinforced concrete members embedded in the coupler was significantly lower than that of general RC members.

In this study, the 3 point bending tests were conducted to evaluate ductility capacity of splice rebar. As a result, the difference in ductility between RC members embedded in the coupler and general RC members was not significant. For more accurate analysis, 4 point bending tests are considered to be necessary.

In this experimental study, the characteristic of damages on GFRP rebar exposed to high temperature only and immerged in alkaline solution after the exposure to high temperature was analyzed through microscopic image analysis. The found microcrack and pores in resin matrix were quantitatively compared if there was effect of pre-exposure to high temperature. The damages, such as microcrack and pores in resin matrix, by alkali exposure were mainly found in rebar surface. On the other hand, the pores caused by high temperatures were extensively found in a section and had greater width than those caused by the alkali exposure. In results of the quantitative comparison, the accumulated length and widths of microcrack and pores in resin matrix in pre-exposed GFRP rebar to high temperature were respectively 1.5 and 1.4 times of those in the GFRP rebar only immerged in alkali solution. Therefore, the deterioration of resin matrix by the alkali exposure could be accelerated due to the pre-exposure to high temperature.

The maximum bond strength of PCS-coated rebar with ultra high-early strength cement and EVA at polymer-cement ratio of 80%, curing ages of 7-day, and coating thickness of 100㎛ is about 1.32 and 1.38 times respectively, the strength of uncoated rebar and epoxy-coated rebar. It is also high bond strength at coating thicknesses of 75㎛ and 100㎛ compared with 150㎛ and 250㎛. It is apparent in this study that the coating thickness is very important factors to improve the bond strength of PCS-coated rebar to cement concrete.

In the sliding slab track of railway bridge, a lateral support block is used to control the lateral displacement. Therefore, it is important to analyze the behavior of dowel rebar and the lateral support block of the sliding slab track. In this study, high strength concrete and steel rebar was selected to analyze the behavior of dowel rebar and shear behavior of high strength dowel rebar and the lateral support block were compared to the equations developed by Soroushian et al. (1986) and CEB-FIP (2010).

NaCl과 LiNO2의 첨가량에 따른 콘크리트에 매립된 철근의 부식거동을 전기화학적 임피던스 분광법을 이용하여 고찰하였다. 부식 가속 방법중 하나인 건습반복법을 이용하여 단기간 내에 부식현상을 촉진하였으며, 측정된 임피던스 값을 통해 등가회로를 제안할 수 있었다. NaCl 1.2 kg/m3이 첨가된 콘크리트에 매립된 철근의 부동태 피막이 빠르게 파괴되는 것을 확인할 수 있었으며, 염화물 첨가량 대비 0.6M의 LiNO2를 첨가한 경우 부식진행속도가 크게 저하하는 것을 확인할 수 있었다. 또한 염화물 첨가량 대비 1.2M의 LiNO2를 첨가한 경우 부동태 피 막이 부식가속시간이 지나도 파괴되지 않고 성능이 유지되는 것을 확인할 수 있었다.

Dowel rebar is key parameter to control the lateral displacement in the sliding slab track. The lateral support block of the sliding slab track is supported by the dowel rebar. In this study, selected parameter (rebar diameter) was expected to affect the performance and behavior of the dowel rebar in the sliding slab track. Furthermore, evaluation of the shear behavior of dowel rebar compared to the results of the Soroushian et al. (1986) and CEB-FIP (2010).

The ultimate load of beam reinforced with polymer cement slurry(PCS)-coated rebar is a little lower than that of un-coated rebar, and almost the same as that epoxy-coated rebar. In special, that using EVA 50% with is in range of 97.0% of un-coated rebar. In this study, it is also apparent that PCS-coated rebar can replace epoxy-coated rebar to solve the corrosion problem in marine construction field.

본 연구에서는 철근의 인장시험에서 변형률에 대한 상세 측정을 위하여 이미지 프로세싱을 이용하고, 변형률 분포와 넥킹구간을 평가하였다. 이미지 프로세싱 방법으로는 기존의 회색조영상을 이용한 방법이 아닌 칼라영상의 색상정보를 분석하여, 원하는 타겟과 가장 일 치하는 영역과 그 외의 영역으로 구분하여 이진영상으로 변환하는 방법을 사용하였다. 변환된 이진영상에서 개별 타겟들의 도심점을 산출한 후 각 도심점의 상대변위값을 변형률로 환산하였다. 인장실험은 ASTM A615 기준으로 제작된 grade 60 철근 중 D22와 D29에 대해서 시험을 수행하였다. 이미지 프로세싱을 이용하여 계측된 변형률 결과를 기존 변형률 게이지를 이용하여 계측한 결과와 비교하여, 본 연구에서 사용한 이미지 프로세싱 방법에 대해서 검증하였다. 이미지 프로세싱을 이용하여 초기 탄성구간의 변형률 뿐만 아니라 넥킹구간에서 발생한 0.5 (50%) 이상의 변형률도 계측이 가능한 것을 확인하였다. 본 연구결과 이미지 프로세싱을 통하여 기존 변형률 게이지의 계측한계를 극복가능 하고, 다양한 지점에서 자유롭게 계측할 수 있음을 알 수 있었다.