최근 Carbon Fiber Sheets(CFS)를 이용하여 철근콘크리트(RC) 기둥을 보강하는 방법이 널리 사용 되고 있다. 기존 연구들은 대부분 원형 단면을 가진 RC 기둥에 초점을 맞추고 있는 반면, 사각 단면 을 가진 RC 기둥에 대한 연구는 비교적 제한적이다. 특히 실험 결과를 예측하기 위한 해석적 연구는 실험적 연구에 비해 제한적으로 수행되었다. 따라서 본 연구에서는 CFS로 횡구속된 RC 기둥의 횡구 속 효과를 예측하기 위한 해석적 연구결과를 제시한다. CFS로 횡구속된 RC 기둥의 횡구속 효과를 예 측하기 위해 상용 구조해석 프로그램인 ABAQUS를 이용하여 유한요소해석이 수행되었다. 유한요소해 석 시 콘크리트는 Solid 요소로 모델링 되었으며, 철근과 CFS는 각각 Beam 요소 및 Shell 요소로 모 델링 되었다. 또한 콘크리트와 철근은 일체 거동하는 것으로 가정되었으며, CFS와 콘크리트는 완전부 착하는 것으로 가정되었다. 실험결과와 해석결과의 파괴양상을 분석하였을 때, 본 연구에서 제안된 유 한요소해석 모델은 실험체의 부착파괴를 적절히 모사할 수 있는 것으로 나타났다. 또한 해석을 통해 예측된 극한응력에 대한 실험결과의 오차는 평균 2.97%로 나타났으며, 극한응력 시의 축방향 변형률 및 횡방향 변형률은 실험결과와 비교하여 각각 평균 17.32% 및 9.52%의 오차를 나타내었다. 따라서 제안된 해석모델은 CFS로 횡구속된 RC 기둥의 횡구속 효과를 비교적 잘 예측할 수 있는 것으로 판 단된다.

이 연구는 탄소섬유시트의 보강겹수와 보강위치에 따른 I형 PFRP 휨부재의 휨보강 효과에 대해 조사하였다. 또한, 탄소섬유시트로 보강한 PFRP 휨부재의 실험적, 이론적으로 확인하기 위해 유한요소해석을 실시하였으며, 휨실험 결과와 이론적 해석결과를 비교분석하였다. 휨실험 결과와 유한요소해석 결과는 이론적인 결과와 비교한 결과 일치하는 경향을 보였고, 휨보강 효과가 큰 탄소섬유시트 2겹을 보강한 시편에서 결과에서 오차가 가장 크게 발생하였다.

이 연구는 탄소섬유시트의 보강겹수에 따른 I형 PFRP 휨부재의 휨보강 효과를 조사하기 위해 길이 600mm의 PFRP 휨부재와 상하부 플랜지에 1mm 두께의 탄소섬유시트로 보강하여 휨실험을 수행하였다. 또한, 탄소섬유시트의 보강겹수와 보강 위치에 따른 I형 PFRP 휨부재의 휨보강 효과와 단면 감소량에 대해 조사하였다. 그 결과 2겹으로 보강하였을 때 휨강도와 휨강성이 증가함을 확인하였다.

Existing reinforced concrete frame buildings designed for only gravity loads have been seismically vulnerable due to their inadequate column detailing. The seismic vulnerabilities can be mitigated by the application of a column retrofit technique, which combines high-strength near surface mounted bars with a fiber reinforced polymer wrapping system. This study presents the full-scale shaker testing of a non-ductile frame structure retrofitted using the combined retrofit system. The full-scale dynamic testing was performed to measure realistic dynamic responses and to investigate the effectiveness of the retrofit system through the comparison of the measured responses between as-built and retrofitted test frames. Experimental results demonstrated that the retrofit system reduced the dynamic responses without any significant damage on the columns because it improved flexural, shear and lap-splice resisting capacities. In addition, the retrofit system contributed to changing a damage mechanism from a soft-story mechanism (column-sidesway mechanism) to a mixed-damage mechanism, which was commonly found in reinforced concrete buildings with strong-column weak-beam system.

탄소섬유는 인장강도와 내구성이 우수하므로 구조물의 표면에 탄소섬유시트를 부착하는 보강공법은 콘크리트 구조물의 보수 및 보강에 사용되는 대표적인 방법이다. 그러나 탄소섬유시트 부착공법은 시공 후 보강성능의 확인이 어려운 단점이 있다. 탄소섬유시트에 광섬유를 매입하여 계측이 가능한 보강재로 사용하는 경우 미부착이나 탈락된 부위를 찾아내어 구조물의 보강수준을 평가할 수 있을 것으로 기대된다. 본 연구는 제작된 센싱보강재의 기본적인 가능성을 확인하기 위해 센싱보강재의 크기와 매립된 광섬유의 간격을 변인으로 두고 센싱보강재 실험체를 제작하였다. BOTDR (Brillouin Optical Time Domain Reflectometer)을 사용하여 시편의 변형에 따른 광섬유의 산란광으로부터 변형률을 계측하고 응답을 분석하였다. 분석 결과로부터 보강수준 정량화를 위한 센싱보강재의 적용성 및 BOTDR의 최소요구성능을 확인하였다.

The purpose of this study was to develop a carbon fiber sheet with embedded fiber optic sensor for maintenance and performance improvement of aged concrete bridges. The carbon fiber sheet reinforcement method can separate the concrete and the carbon fiber sheet, so it is necessary to investigate the bond performance level. However, separation of concrete and carbon fiber sheet and investigation of concrete scaling phenomenon are carried out by human, so it is difficult to secure objectivity and accurate investigation. Therefore, in this study, a method to confirm the bond level of carbon fiber sheet by reinforcing with a carbon fiber sheet with a fiber optic sensor was examined. In this study, we investigated the strain of fiber optic sensor embedded in carbon fiber sheet to identify the separate point of carbon fiber sheet. The strain measured by fiber optic sensor was measured by numerical analysis. The strain rate of the carbon fiber sheet was compared with that of the carbon fiber sheet. As a result, it was confirmed that the strain was changed at the point where the carbon fiber sheet was separated, and the strain occurred in the carbon fiber sheet was examined to predict the separate point.

The purpose of this study is to develop a carbon fiber sheet with embedded fiber optic sensor for maintenance and performance improvement of aged concrete bridges. The carbon fiber sheet bonded method has many advantages in terms of member repair and reinforcement, but it is disadvantageous in that it is necessary to directly identify the separate point generated during the bonded of the carbon fiber sheets by an artificial method. In this study, we examined the method of confirming the separate point of the carbon fiber sheets by examining the strain of the fiber optic sensor embedded in the carbon fiber sheets. The strain rate measured by the fiber optic sensor was replaced by the strain of the carbon fiber sheets derived from the FEM analysis.

This paper deals with the strengthening effect of reinforced concrete beams strengthened with carbon fiber sheets (CFSs). Fifteen strengthened reinforced concrete (RC) beams were experimentally evaluated to determine improvements in structural performance. Test parameters in this experimental study are strengthening ratios and strengthening methods of CFSs (I-S, I-W, U-S, U-W type). RC beams strengthened with CFSs were tested under sustaining load. Considering strengthening ratios and strengthening methods of carbon fiber sheets, structural performance and failure mode of test specimens were evaluated. The results show that maximum capacity of beams strengthened with CFSs is about 28.8% in I-S type, 20.5% in I-W type, 26.0% in U-S type, 28.7% in U-W type higher than that of control beam.

In recent years, fiber reinforced polymer plastic composites are readily available in the construction industry. Fiber reinforced polymer composite has many advantages such as high specific strength and high specific stiffness, high corrosion resistance, light-weight, magnetic transparency, etc. In this paper, we present the result of investigation pertaining to the flexural behavior of flange strengthened I-shape pultruded fiber reinforced polymer plastic (PFRP) member using carbon fiber sheet (CFRP sheet). Test variable is consisted of the number of layers of strengthening CFRP sheet from 0 to 3. From the experimental results, flexural strengthening effect of flange strengthened I-shape PFRP member using CFRP sheet is evaluated and it was found that 2 layers of strengthening CFRP sheet are appropriate considering efficiency and workability.

In recent years, fiber reinforced polymer plastic composites are readily available in the construction industry. Fiber reinforced polymer composite has many advantages such as high specific strength and stiffness, high corrosion resistance, light-weight, magnetic transparency, etc. In this paper, we present the result of investigation pertaining to the flexural behavior of flange strengthened I-shape pultruded fiber reinforced polymer plastic (PFRP) member using carbon fiber sheet (CFRP sheet). The number of layers of strengthening CFRP sheet, with a value of 0 to 3 was the test variables. From the experimental results, flextural strengthening effect of flange strengthened I-shape PFRP member using CFRP sheet is evaluated and it was found that 2 layers of strengthening CFRP sheet is appropriated considering efficiency and workability.

This paper presents experimental studies aiming at evaluation of structural behaviors of RC (Reinforced Concrete) beams externally strengthened with taper ended CFRPs(Carbon Fiber Reinforced Polymers). Experiments are performed with RC beams having different numbers of CFRP layers and length of each layer. The beams are subjected to four point-bending with simply supported condition. Test results of taper ended CFRPs and non-tapered CFRPs are compared and the better strengthening effect is observed from tapered ended CFRPs.

Recently, strengthening and repairing concrete structures are increasing due to the deterioration of concrete infrastructures. Carbon Fiber Reinforced Polymer Plastic (CFRP) system for strengthening concrete structures have emerged as an alternative to traditional strengthening techniques, such as steel plate bonding, section enlargement, and external post-tensioning. CFRP systems offer advantages over traditional strengthening techniques such as lightweight, noncorrosive, and relatively easy to install. In this paper, we present the structural design algorithm for the RC beams strengthened with CFRP sheet based on ACI 440. In addition, structural behavior of strengthened RC beams is investigated by varying the amount of CFRP sheets.

본 연구는 반복 횡하중 하에서 CFRP(Carbon Fiber Reinforced Polymer) Sheet로 보강된 철근콘크리트 프레임면내 조적벽체의 전단내력을 평가하여 국내 조적벽체 학교 건축물에 적합한 CFRP Sheet 보강 방안을 제안하는 것에 그 목적이 있다. 조적 허리벽이 있는 1층, 1경간, 1/2 스케일의 시험체를 4개 제작하여 CFRP Sheet의 보강량을 변수로 실험을 수행하였으며 이를 통하여 보강량에 따른 강도와 강성의 변화를 분석하였다. 실험 결과 CFRP Sheet는 시험체의 내력과 강성을 향상시켰으며 특히 기둥과 조적벽을 모두 보강하는 방법을 통한 보강방법에 있어 그 적용성을 확인할 수 있었다.

본 연구의 목적은 일정 축하중과 반복횡하중 하에서 탄소섬유시트와 비좌굴 가새로 보강된 보-기둥 시험체의 횡방향 거동 평가를 통하여 사용된 보강 방법의 구조적 성능을 검증하는 것이다. 세 개의 시험체를 비보강, 탄소섬유보강, 탄소섬유와 비좌굴 가새 보강 방법을 각각 적용하여 제작하였다. 변위에 따른 최대, 최소하중은 하중-변위 관계를 분석함으로써 평가되어지며, 하중과 강성의 관계는 비교구간의 유효강성 분석에 의해 평가된다. 실험의 수행 결과, 보강을 하지 않은 시험체에 비하여 보강을 적용한 시험체는 최대허용하중과 유효강성, 철근 항복 시 재하 횡하중, 변위연성비 등에서 상대적으로 우수한 성능을 보였다.

The present study was conducted to appraise tow theoretical models for reinforced concrete members strengthened with carbon fiber reinforced polymer(CFRP) sheets. Predicted values using two models by ACI 440.2R-08 were compared with ones obtained from experiment. For this, two flexural specimens were tested: one unstrengthened specimen and the other strengthened with CFRP sheets. Based on the test results, the wow models are reliable by showing good agreement with the test results.

In this study, experimental research was carried out to improve and evaluate the seismic performance of reinforced concrete beam-column joint using Embedded Carbon Fiber Rod and Carbon Fiber Sheet in existing reinforced concrete building. Test result shows that retrofitting specimen(LBCJ-SP45, CS2, CRUS) designed by the improvement of seismic performance of reinforced concrete beam-column joints load-carrying capacities were increased 1.34 ~ 1.54 times in comparison with the standard specimen.