긴장을 가한 보강 플레이트로 보강된 RC 보의 휨보강 효과

하상수 한국구조물진단유지관리공학회 2019 한국구조물진단유지관리공학회 논문집 Vol.23 No.1

Fiber-reinforced polymer (FRP) composites have proved to be reliable as strengthening materials. Most of existing studies used single types of FRP composites. Therefore, in this experimental study, carbon FRP sheet, aramid FRP sheet, and hybrid FRP plate including glass fibers were fabricated, and the effect of pre-stressed FRP composites on flexural strengthening of reinforced concrete (RC) beams was investigated. In total, eight RC beam specimens were fabricated, including one control beam (specimen N) without FRP composites and seven FRP-strengthened beams. The main parameters were type of FRP composite, the number of anchors used for pre-stressing, and thickness of FRP plates. As a result, the beam strengthened with pre-stressed FRP plate showed superior performance to the non-strengthened one in terms of initial strength, strength and stiffness at yielding, and ultimate strength. As the number of anchors and thickness of FRP plate (i.e., amount of FRP plates) increased, the strengthening effect increased as well. When hybrid FRP plates were pre-stressed, the strengthening effect was higher in comparison with pre-stressed single type FRP plate. 본 연구는 탄소섬유시트, 아라미드섬유시트, 그리고 유리섬유시트를 혼합한 하이브리드 FRP 플레이트를 제작하였으며, 제작한 보강 플레이트를 보강한 후, 최대한의 휨 보강 효과가 발생되도록 다시 보강 플레이를 긴장시켜 RC보의 휨 보강 효과를 파악하고자 하였다. 또한, 긴장시키는 보강방법을 제시하는 동시에 무보강 실험체에 비해 보강효과가 어느 정도 되는지 실험적으로 규명하기 위해 실험적 연구를 진행하였다. 연구를 위해 총 8개의 RC 보 부재를 동일하게 제작하여 1 개의 실험체(N 실험체)를 제외한 7 개의 실험체는 보강재 종류, 단부 정착 앵커 개수, 보강재 두께 등을 주요 변수로 하여 실험을 실시하였다. 실험결과, 휨 거동을 보이는 실험체에 긴장을 가한 FRP 플레이트로 보강하면, 보강하지 않은 실험체에 비해 우수한 휨거동(초기강도, 항복시 강도 및 강성, 최대강도 등)보여 주었으며, 단부정착 앵커의 개수가 많고, 보강재의 두께(보강량)가 클수록 보강효과가 우수한 것으로 나타났으며, 긴장시킨 보강재는 단일 FRP 플레이트에 비해, 하이브리드 FRP 플레이트를 적용했을 때 보강효과가 더 우수하게 나타났다.

FRP-강판 복합플레이트로 보강된 RC 보의 휨거동에 관한 실험적 연구

안상호 대한건축학회지회연합회 2007 대한건축학회연합논문집 Vol.9 No.3

The flexural behavior of reinforced concrete beams strengthened with FRP-steel composite plate is presented. In this method, FRP-steel composite plate, reinforced with a combination of fibers(carbon or glass) and steel plate, are bonded to the concrete substrate and fastened with anchor bolts. The experimental work included flexural testing of 2.4m-long concrete beams with bonded and anchored composite plate. The strengthened RC beams were designed to fail in a ductile manner. The thin steel plate in FRP-steel composite plate makes usage of the anchoring system possible, which could delay or prevent the premature debonding failure. Two reference beams and 21 strengthened beams with CSP(Carbon fiber-steel composite plate) and 12 strengthened beams with GSP(Glass fiber-steel composite plate) were tested. The structural behaviors of strengthened beams are compared with codes in terms of yield load and ultimate load, flexural stiffness. 33 beams were tested experimentally to evaluate the strength enhancement provided by the composite plate. In the test results presented in this paper, the strengthened beams showed increases in yield and ultimate loads of up to 29~70% and 33~115%, respectively over an unstrengthened beam. All strengthened beams failed, as intended, in a ductile manner with the ultimate failure mode due to fiber tension failure in composite plate at large deflection with the composite plate still firmly attached. According to the results, it is shown that beams strengthened with composite plate are structurally efficient.

전단키 종류에 따른 GFRP Plate와 콘크리트의 합성거동에 관한 실험적 연구

김용재 ( Kim Yongjae ),신정렬 ( Shin Jeongryol ),이안호 ( Lee Anho ),문도영 ( Moon Doyoung ) 한국복합신소재구조학회 2023 복합신소재구조학회논문집 Vol.14 No.6

섬유 보강폴리머(Fiber Reinforced Polymer: FRP)는 강재에 비해 인장강도 및 내식성이 우수하므로 콘크리트와의 합성을 통해 FRP의 재료적 특성에 의한 단점을 보완하고, 그 활용도를 증진시키기 위한 연구가 진행되고 있다. 그러나 FRP와 콘크리트로 구성된 단면이 설계이론과 동일한 합성거동을 하기 위해서는 전단연결을 통해 두 요소 간 충분한 응력전달이 이루어져야 한다. 이 논문에서는 GFRP Plate와 콘크리트의 합성거동 증진을 위한 다양한 전단연결 방법을 제안하고, 변수별 거동 특성을 분석하고자 하였다. 이를 위해 단위부재 형태의 시험제를 제작하여 Push out 실험을 진행하였다. 실험결과, 작은 단면의 FSK도 높은 전단력을 저항하는 것으로 확인되어 볼트 천공에 의한 손상이 우려되는 단면구간에서 FSK 적용이 가능할 것으로 예상된다. 또한 GFRP Plate에 볼트를 전단연결재로 활용할 경우, GFRP Plate의 파단을 방지하고 전단저항력 증진을 위해 FSK를 동시에 적용하는 것이 효과적인 것으로 판단된다. Fiber-reinforced polymer (FRP) exhibits superior tensile strength and corrosion resistance compared to steel but has a lower elasticity. Recently, researchers have addressed this by proposing composite sections of FRP and concrete. To ensure the intended composite behavior, these FRP-concrete sections should exhibit sufficient stress transfer between the two elements through a shear connection. Herein, various shear connection methods were proposed to improve the composite behavior of glass fiber-reinforced polymer (GFRP) plates and concrete. Through push-out tests, the behavior characteristics of the prepared specimens were analyzed. The findings confirm that an FRP shear key (FSK) with a small cross-section resists high shear stresses, making it suitable for sections vulnerable to damage from bolt drilling. Additionally, combining an FSK with bolts as shear connectors on a GFRP plate proves beneficial in preventing the fracture of the plate and improving the shear resistance.

벨크로를 이용한 FRP 플레이트 보강공법의 시공공법 개선

홍건호 한국구조물진단유지관리공학회 2008 한국구조물진단유지관리공학회 논문집 Vol.12 No.6

본 논문에서는 FRP 보강재의 부착방식에 따른 RC보의 휨보강 성능평가에 대하여 연구하였다. 기존의 FRP 휨보강공법은 보강재의 형태에 따라 크게 FRP 쉬트 보강공법과 FRP 플레이트 보강공법으로 분류될 수 있으며, 각 공법은 에폭시의 양생기간동안 쉬트의 들뜸이 발생하지 않도록 주의해야하거나, 앵커설치 등 시공이 복잡하며, 인력이 많이 소요되는 단점이 있다. 이러한 문제점을 개선하기 위하여 본 논문에서는 Velcro형 고정재를 사용하여 FRP 플레이트를 임시 고정하는 보강공법을 제안하였고, 이에 대한 휨보강 성능평가 실험을 실시하였다. 실험은 FRP보강재의 부착방식을 변수로 하여 총 4개 실험체에 대하여 수행하였다. 실험결과 벨크로형 FRP판 보강공법은 타 공법에 비하여 우수한 시공성을 가짐과 동시에 휨내력이나 연성도 면에서도 우수한 보강성능을 확보하고 있는 것으로 나타났다. The object of this paper is to study the flexural strengthening effectiveness on the construction method of bonding of the FRP. The existing FRP flexural strengthening methods were divided into FRP sheet strengthening and FRP plate strengthening according to the FRP condition. For improving the existing construction method, this paper proposed the velcro type anchorage system for temporary bonding material, and flexural strengthening effects were tested. Test variables were bonding methods of the FRP strengthening materials, and total 4 specimens were tested. Following to the test results, it is shown that FRP-plate strengthening method using the velcro can get better workability than existing construction methods, and have excellent strengthening performance including flexural strength, stiffness, ductility and failure aspect.

콘크리트에 표면매입 보강된 FRP판의 전단키 및 연단거리 효과

서수연 한국구조물진단유지관리공학회 2016 한국구조물진단유지관리공학회 논문집 Vol.20 No.1

본 연구에서는 콘크리트에 표면매입된 FRP판의 부착거동에서, 전단키와 연단거리의 효과를 관찰하기 위한 부착시험을 실시하였 다. 실험에서의 주요변수는 전단키의 위치, 형태 그리고 연단길이이다. 규격 3.6 ㎜×16 ㎜의 FRP를 400 ㎜×200(300) ㎜×400 ㎜ 규격의 콘크리 트 블록에 매입하고 에폭시로 고정시켜서 실험변수에 따라 총 10개의 부착실험체를 제작하였다. FRP의 연단에 인장력을 가한 뒤 파괴시까지 실험을 실시하고 하중을 기록하였으며, 미끄러짐과 FRP의 인장변형량을 기록하였다. 실험으로부터, 전단키의 위치는 가력부에서 멀리 떨어 질수록 전단강도가 상승하는 것으로 나타났으며, 전단키의 직경이 커질수록 내력이 저하되는 것으로 나타났다. 특히 전단키가 일정 이상의 규 격이 되면 전단키가 없는 경우에 비하여 내력이 저하되어 오히려 부착강도에 부정적인 영향을 미칠 수 있는 것으로 나타났다. NSM FRP에서 응력장용방향의 연단거리가 길어짐에 따라 동일 부착길이임에도 불구하고 내력이 일부 증가하는 것으로 나타났다. 표면매입 보강된 FRP의 부착실험에서, FRP와 콘크리트사이의 부착-미끄러짐은 전체거동을 지배하는 것으로 나타나므로 이에 따른 과도한 미끄러짐은 설계에 반드시 고려될 필요가 있다. This paper presents a bond test to find the effect of shear key and edge length from the bonded FRP in near surface-mounted(NSM) retrofit using FRP plate. Main parameters in the test are the location and size of shear key and the edge length. For the test, 10 specimens were made by embedding FRP plate of 3.6 ㎜×16 ㎜ into 400 ㎜×200(300) ㎜×400 ㎜ concrete block and fixing it by using epoxy. Tensile load was applied to the FRP of the specimens until failure and was recorded at each load increase. In addition, the bond slip and elongation of FRP were measured during the test. From the test, it was found that the further the shear key located from the loading, the higher strength we could get. The bond strength inversely depended on the size of shear key. Especially, when the size of shear key was to be lagger than certain size, the bond strength decreased to very low value; even less than that of the case without shear key. The bond strength somewhat increased corresponding to the increase of edge length from the bonded end of FRP to loading in spite of same bond length. The bond-slip between FRP and concrete governed overall deformation in the bond test of NSM FRP so that the effect of excessive slip is necessary to be considered in the design.

FRP 보강판 부착 콘크리트에서 유도초음파 모드 거동에 대한 접착층의 영향

이용주(Yongju Lee),신성우(Sung Woo Shin) 한국비파괴검사학회 2012 한국비파괴검사학회지 Vol.32 No.1

본 연구에서는 FRP 보강판 부착 콘크리트에서의 유도초음파 기본 모드의 전파 특성에 부착제인 epoxy의 두께와 물성이 미치는 영향을 알아보고자 하였으며, 이를 위해 FRP-epoxy-concrete로 구성된 다층 유도초음파 시스템을 모델링하고 모드 해석을 수행하였다. Epoxy 층의 두께와 탄성계수를 변수로 하여 해석을 수행한 결과, A0 모드에 비해 S0 모드가 epoxy 층의 두께와 탄성계수 변화에 큰 영향을 받으며, 이로부터 경계층인 Epoxy 층의 상태 평가에는 A0 모드에 비해 S0 모드가 유효하리라는 결론을 얻었다. In this study, effects of bonding agent, e.g. epoxy, on the behavior of fundamental guided wave modes propagated in FRP plate bonded on a concrete, are investigated. Global matrix model of multilayered FRP-epoxy-concrete system was constructed to obtain the velocity and attenuation dispersion curves of the fundamental A0 and S0 modes. Two variables, thickness and elastic modulus of epoxy layer, were considered in the dispersion analysis. It was found that both the thickness and the elastic modulus of epoxy layer greatly affect the phase velocity and attenuation of S0 mode while those are negligible for A0 mode. Based on the results, it was concluded that S0 mode is more effective than A0 mode for bonding condition assessment for FRP plate bonded concrete.

FRP판을 이용한 콘크리트 보강에서 보강방법에 따른 부착성능

서수연(Seo Soo-Yeon),오재길(Oh Jae-Gil),최기봉(Choi Ki-Bong) 대한건축학회 2011 大韓建築學會論文集 : 構造系 Vol.27 No.8

Recently, FRP (Fiber Reinforced Polymer) has been widely applied in retrofit of concrete member owing to its ease construction and high structural capacity compared to other materials. External Bond Retrofit (EBR) using FRP sheet or plate is most popular method for flexural retrofit of concrete member. In strengthened concrete member using this method, however, problems such as dismantling of FRP were founded after retrofit. This causes a strength reduction of the retrofitted member. To resolve this problem, Near-Surface-Mounted Rertofit (NSMR) method was developed and being studied. In this paper, bond capacities of EBR and NSMR using FRP plate were studied experimently and results were compared each other. Main variables in the test were retrofit method, bond length and existence of shear key. From the test results, it was found that the member strengthened by NSMR had almost 1.5 times higher bond strength than that by EBR. The contribution of shear key was not observed when the splitting failure of concrete governed.

내진보강 섬유의 재료별 특성에 따른 기둥의 내진성능 효과 분석

허진호(Jinho Hur),김진호(Jinho Kim),박웅기(Woongi Park),김기홍(Ki-Hong Kim) 한국철도학회 2013 한국철도학회 학술발표대회논문집 Vol.2013 No.5

FRP섬유와 알루미늄 다공판으로 제작된 내진보강시스템은 가벼운 중량과 공장생산을 통하여 균질한 품질과 간편하고 신속한 시공성으로 철근콘크리트구조의 기존 철도시설보강에 적합한 보강시스템이다. 본 연구에서 탄소섬유, 유리섬유, 고성능 유리섬유 및 아라미드와 알루미늄 다공판을 적층하여 제작한 복합판으로 보강된 철근콘크리트 기둥의 보강성능을 반복횡하중 실험을 통하여 평가하였다. 실험결과에 근거하여 보강된 기둥과 비보강된 기둥의 하중-변위이력, 파괴모드, 강성 및 연성 등을 비교하였으며, 유리섬유의 인장강도를 개선한 고성능 유리섬유의 보강성능이 가장 우수한 것으로 나타났다. Composite plate composed of fiber and perforated aluminum plate is lightweight and mass produced in order to consistent quality and rapid construction. It is appropriate for seismic retrofit system of the existing railway concrete structures. In this study, concrete column experiments reinforced by composite plate made of 4 types of FRP(carbon fiber, glass fiber, high performance glass fibers and aramid) with perforated aluminum plate were tested under lateral cyclic loading. Comparing load-displacement relation, failure modes, initial stiffness and ductility, plate composed of high performance glass fiber was found better performance than the others.

Behavior of FRP-reinforced steel plate shear walls with various reinforcement designs

Mehdi Seddighi,Mohammad A. Barkhordari,S.A.A. Hosseinzadeh 국제구조공학회 2019 Steel and Composite Structures, An International J Vol.33 No.5

The nonlinear behavior of single- and multi-story steel plate shear walls (SPSWs) strengthened with three different patterns of fiber reinforced polymer (FRP) laminates (including single-strip, multi-strip and fully FRP-strengthened models) is studied using the finite element analysis. In the research, the effects of orientation, width, thickness and type (glass or carbon) of FRP sheets as well as the system aspect ratio and height are investigated. Results show that, despite an increase in the system strength using FRP sheets, ductility of reinforced SPSWs is decreased due to the delay in the initiation of yielding in the infill wall, while their initial stiffness does not change significantly. The content/type/reinforcement pattern of FRPs does affect the nonlinear behavior characteristics and also the mode and pattern of failure. In the case of multi-strip and fully FRP-strengthened models, the use of FPR sheets almost along the direction of the infill wall tension fields can maximize the effectiveness of reinforcement. In the case of single-strip pattern, the effectiveness of reinforcement is decreased for larger aspect ratios. Moreover, a relatively simplified and approximate theoretical procedure for estimating the strength of SPSWs reinforced with different patterns of FRP laminates is presented and compared with the analytical results.

Shear strengthening of deficient concrete beams with marine grade aluminium alloy plates

Abu-Obeidah, Adi S.,Abdalla, Jamal A.,Hawileh, Rami A. Techno-Press 2019 Advances in concrete construction Vol.7 No.4

In this study, high strength aluminum alloys (AA) plates are proposed as a new construction material for strengthening reinforced concrete (RC) beams. The purpose of this investigation is to evaluate AA plate's suitability as externally bonded reinforcing (EBR) materials for retrofitting shear deficient beams. A total of twenty RC beams designed to fail in shear were strengthened with different spacing and orientations. The specimens were loaded with four-points loading till failure. The considered outcome parameters included load carrying capacity, deflection, strain in plates, and failure modes. The results of all tested beams showed an increase up to 37% in the load carrying capacity and also an increase in deflection compared to the control un-strengthened beams. This demonstrated the potential of adopting AA plates as EBR material. Finally, the shear contribution from the AA plates was predicted using the models available in the ACI440-08, TR55 and FIB14 design code for fiber reinforced polymer (FRP) plates. The predicted results were compared to experimental testing data with the ratio of the experimentally measured ultimate load to predicted load, range on the average, between 93% and 97%.