• Advances in concrete construction
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• 제10권4호
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• pp.319-332
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• 2020

The impacts of reinforcing concrete matrix with steel fibers, polypropylene fibers and recycled plastic fibers using different volume fractions of 0.15%, 0.5%, 1.5% and 2.5% on the compressive and tensile characteristics are experimentally investigated in the current research. Also, flexural behavior of plain concrete (PC) beams, shear performance of reinforced concrete (RC) beams and compressive characteristics of both PC and RC columns reinforced with recycled plastic fibers were studied. The experimental results showed that the steel fibers improved the splitting tensile strength of concrete higher than both the polypropylene fibers and recycled plastic fibers. The end-hooked steel fibers had a positive effect on the compressive strength of concrete while, the polypropylene fibers, the recycled plastic fibers and the rounded steel fibers had a negative impact. Compressive strength of end-hooked steel fiber specimen with volume fraction of 2.5% exhibited the highest value among all tested samples of 32.48 MPa, 21.83% higher than the control specimen. The ultimate load, stiffness, ductility and failure patterns of PC and RC beams in addition to PC and RC columns strengthened with recycled plastic fibers enhanced remarkably compared to non-strengthened elements. The maximum ultimate load and stiffness of RC column reinforced with recycled plastic fibers with 1.5% volume fraction improved by 21 and 15%, respectively compared to non-reinforced RC column.

• Structural Engineering and Mechanics
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• 제50권6호
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• pp.817-834
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• 2014

An experimental program was designed in the current work to examine the structural behavior of ferrocement beams reinforced with composite materials under three point loadings up to failure. The experimental program comprised casting and testing of twelve ferrocement beams having the dimensions of 120 mm width, 200 mm depth and 1600 mm length. The twelve beams were different in the type of reinforcements; steel bars, traditional wire meshes (welded and expanded wire meshes) and composite materials (fiberglass wire meshes and polypropylene wire meshes). The flexural performances of the all tested beams in terms of strength, ductility, cracking behavior and energy absorption were investigated. Also all the tested beams were simulated using ANSYS program. The results of the experimental tests concluded that the beam with fiber glass meshes gives the lowest first crack load and ultimate load. The ferrocement beam reinforced with four layers of welded wire meshes has better structural behavior than those beams reinforced with other types of wire meshes. Also the beams reinforced with metal wire meshes give smaller cracks width in comparing with those reinforced with non-metal wire meshes. Also the Finite Element (FE) simulations gave good results comparing with the experimental results.

• 한국재료학회지
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• 제4권2호
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• pp.219-226
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• 1994

반복회수에 대한 하중-변형률 선도로부터 구산 잔류변형률의 비교 결과에서 피로하중하의 GFRP관의 강성은 GFRP관의 유리섬유의 적층수가 클수록 크게 나타났으며, 이러한 현상은 피로파괴 직전까지 나타났다. 아울러 본 피로실험 결과를 회귀분석하여 구한 S-N선도에 의하면 정적극한강도 백분율에 대한 피로강도는 GFRP관의 유리섬유 적층수가 증가할수록 증가하였으며, 유리섬유의 적층수가 15, 25, 35층인 GFRP관의 반복회수 200만회에 대한 피로강도는 정적극한강도는 각각 약 75.2%, 79.5%, 84.2%로 나타났다.

• Steel and Composite Structures
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• 제27권4호
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• pp.453-464
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• 2018

The objective of this study is to devise an alternative strengthening method to the ones available in the literature. So, external steel members were used to enhance both flexural and shear capacities of reinforced concrete (RC) beams having insufficient shear capacity. Two types of RC beams, one without stirrups and one with lacking stirrups, were prepared in the study. These beams were strengthened with external steel clamps devised by the authors and with external longitudinal reinforcements. Although the use of clamps alone didn't have a significant effect on the load carrying capacity of the tested beams, the ductility increased approximately tenfold and the failure behavior changed from brittle to ductile. Although the use of clamps and longitudinal reinforcements together did not significantly increase the ductility of the beams, it approximately doubled their load capacities. The results of the experimental study were compared to the ones obtained from nonlinear finite element analysis (NLFEA) and it was observed that they were compatible. Finally, it can be concluded that the devised method could be applied to structural members as an alternative to methods in application due to lightness, low-cost, easy applicable and reliable.

• 대한건축학회논문집:구조계
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• 제34권1호
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• pp.3-10
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• 2018

This experimental investigation was conducted to observe the shear strengthening behavior of pre-damaged reinforced concrete (RC) beams strengthened with externally post-tensioning steel rods. A total of six simply supported beams - two control beams and four post-tensioned beams using external steel rods - were tested to failure in shear. The external steel rods of 18 mm or 28 mm diameter were respectively employed as post-tensioning material. The four post-tensioned beams have a V-shaped profile with a deviator (or saddle pin) located at mid-span, and the post-tensioning system increased the low load-carrying capacity and overcame a little bit of deflection caused by damage. Concretely, the load-carrying capacity and flexural stiffness were respectively increased by about 25~57% and 263~387% due to the post-tensioning when compared with the unstrengthened control beams.

• Steel and Composite Structures
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• 제41권5호
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• pp.649-661
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• 2021

This paper presents experimental and analytical studies to understand the behavior of crumb rubber concrete (CRC)-filled fiber reinforced polymer (FRP) and steel tube double skin column (DSC) and beam (DSB) members under cyclic loading. The main test variable was the percentage of rubber which ranged from 0 to 40%. For column members, different heights corresponding to different aspect ratios were examined to understand the to understand the effect of DSCs' slenderness on the cyclic response of the columns. the. The behavior of the specimens in terms of failure mode, strain development, energy dissipation, load-displacement response were presented and compared. The ability of the current provisions of the Australian codes to predict the capacity of such double skin members was also evaluated based on the test results. This study concluded that the reduction in the concrete strength was more severe at the material level compared to structural level. Also, as the load changed from axial compression in columns to pure moment in beams the negative effect of rubber percentage on the strength became less significant.

• Steel and Composite Structures
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• 제45권2호
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• pp.193-204
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• 2022

The need for establishing the contribution of pultruded FRP encasements and additional FRP wraps around these encasements to the shear strength and load-deflection behavior of reinforced concrete beams is the main motivation of the present study. This paper primarily focuses on the effect of additional wrapping around the composite beam on the flexural and shear behavior of the pultruded GFRP (Glass Fiber Reinforced Polymer) beams infilled with reinforced concrete, taking into account different types of failure according to av/H ratio (arch action, shear-tension, shear-compression and pure bending). For this purpose, nine hybrid beams with variable shear span-to-depth ratio (av/H) were tested. Hybrid beams with 500 mm, 1000 mm, and 1500 mm lengths and cross-sections of 150x100 mm and 100x100 mm were tested under three-point and four-point loading. Based on the testing load-displacement relationship, ductility ratio, energy dissipation capacity of the beams were evaluated with comprehensive macro damage analysis on pultruded GFRP profile and GFRP wrapping. The GFRP wraps were established to have a major contribution to the composite beam ductility (90-125%) and strength (40-75%) in all ranges of beam behavior (shear-dominated or dominated by the coupling of shear and flexure). The composite beams with wraps were showns to reach ductilities and strength values of their counterparts with much greater beam depth.

• 콘크리트학회논문집
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• 제19권5호
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• pp.569-575
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• 2007

철근콘크리트 구조물의 수명 연장 및 기능 보완을 위하여 콘크리트 면의 보수를 실시할 경우 일반적으로 구조적 내력을 고려하지 않는다. 특히, 표면박락 등의 보수에는 단순하게 모르타르 도포만을 이용하여 보수가 완료되므로 별도의 구조적인 보강 성능을 발휘하지 않는다. 그러나 시공성의 향상 및 균열의 억제를 위하여 철망 등의 재료를 사용할 경우 일정부분 보강의 효과를 얻을 수 있을 것으로 예상되며, 특히, 수로 구조물과 같이 교각 간에 놓여지는 구조요소의 경우 하부면의 보수를 실시할 경우 휨 저항성의 증가를 기대할 수 있다. 따라서 본 연구에서는 크리프 철망에 의한 보수를 실시하고 보수 부위 및 보수 두께에 따른 보강 성능을 확인하고자 하였다. 이를 위하여 두께 150mm, 길이 3,000mm, 너비 600mm 슬래브를 제작하고, 상부 부분 보수, 상부 전면 보수, 하부 부분 보수, 하부 전면 보수, 크림프 철망 보강 유무 등 총 8개 실험 유형을 선택하고 이에 대한 휨 보강 성능 실험을 실시하였다. 분석 결과, 크림프 철망을 보강한 실험체에서 보수 재료의 두께가 증가할수록 항복하중 및 파괴하중은 높아지는 것으로 나타났으며, 동일 조건일 경우 하부면의 보수가 휨 하중에 대한 내력을 증가시킬 수 있는 것으로 나타났다. 또한, 휨 하중을 받는 구조물 중 부분 보수만을 실시할 경우 휨 보강 성능은 기대하기 어려운 것으로 나타났다. 결론적으로 크림프 철망에 의한 보수공법 적용 시 휨 저항성의 증가가 있는 것을 알 수 있었다.

• 콘크리트학회논문집
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• 제15권3호
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• pp.377-385
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• 2003

인장강도와 내방식성이 우수하고 콘크리트 구조물속에서 철근과의 정착성이 양호하여 콘크리트 구조물의 새로운 보강재로 사용되고 있는 탄소격자섬유의 보강효과를 검증하기 위하여 탄소격자섬유보강공법으로 보강한 철근콘크리트 보 시험체를 제작하여 정적 휨 파괴실험을 통해 보강효과 및 휨 파괴특성을 분석하였다. 강판이나 탄소섬유 압착공법에서 나타나는 계면박리(탈락)파괴 보다는 보수 몰탈의 고강도화로 휨균열의 진전에 의해 콘크리트 속에서 철근에 정착된 격자섬유 층에서의 균열이 지점부로 진행되어 파괴되는 내부 계면박리와 지간중앙에서 철근 항복후 격자와 연결된 앵커볼트의 항복으로 인한 탄소격자섬유 파괴, 그리고 격자섬유 항복후 취성적인 콘크리트 압축파괴 양상이 나타났다. 실험결과를 근거로 최소보강재량이 제시되었으며, 강도설계법을 근거로 격자섬유로 보강시 필요한 설계법이 제안되었다.

• 한국건설관리학회논문집
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• 제5권6호
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• pp.212-217
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• 2004

이 연구는 같은 위치에 힘모멘트와 전단력이 최대가 되는 철근콘크리트 보에 대하여 휨모멘트 보강을 실시하는 경우, 탄소 섬유판의 두께와 하중점 부위 및 탄소섬유판의 끝부분을 감싸는 탄소섬유쉬트의 겹수를 변수로 하여 보의 구조적 거동을 실험하였다. 탄소섬유판의 두께의 증가에 따라 내력이 증가하였으나 선형적으로 비례하지 않았으며, 하중점에 감싼 탄소섬유쉬트의 영향은 뚜렷하게 나타나지 않았다 이 는 보강시험의 주된 파괴가 탄소섬유판의 파단이 아닌 하중점 주위에서의 휭-전단균열에서부터 층분리가 시작되었고 하중점을 탄소섬유쉬트로 감싼 경우 휭-전단균열 탄소섬유쉬트의 바깥 부분으로 이동하기 때문이다. 또한 탄소섬유판 단부에 정착용으로 시공한 탄소섬유쉬트는 하중점에서 발생한 취성파괴로 인하여 큰 효과를 나타내지 못하였다. 그러므로 재하상태에 따른 설계방법을 다르게 할 필요가 있으며, 특히 같은 위치에서 휨모멘트와 전단력이 최대가 되는 경우 탄소섬유판의 유효 두께는 최대 0.6mm로 하고 무보강보의 휨모멘트에 대한 보강된 보의 휨모멘트 비는 1.5-2.0으로 제한하는 것이 바람직하며, 0.6mm이상의 탄소섬유판을 사용하기 위하여 탄소섬유쉬트로 하중점을 보강하는 경우 무보강보 휨모멘트의 1.5 배가 되는 위치이상 탄소섬유쉬트를 연장하는 것이 바람직하다.