• Steel and Composite Structures
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• 제24권4호
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• pp.383-390
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• 2017

This paper highlights the experimental and numerical investigations performed on a tubular T-joint fabricated from circular hollow sections under axial compressive loads applied at the brace. Tests were performed on a reference joint and the joint wrapped with Carbon Fiber Reinforced Polymer (CFRP). The Nitowrap EP carbon fiber with Nitowrap 410 resin serve as a composite material is used for wrapping the T-joint. Schematic diagram of the fabricated tubular joint for the experimental test setup, along with the experimental and numerical results are presented. After performing these experiments, it has been demonstrated that the joint wrapped with CFRP has a better strength and lesser deflection than a reference joint. Finite element analysis carried out in Ansys reveals that the results were in good correlation with the experimental values.

• 국제학술발표논문집
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• The 3th International Conference on Construction Engineering and Project Management
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• pp.1272-1277
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• 2009

Since improved capacity for RC bridges has been required due to deterioration or increase in traffic, the deflection of cracked reinforced concrete slabs need to be reconsidered. Strengthening is known as the better way to improve capacity of bridges than reconstructing. In this paper, Fiber Reinforced Plastic (FRP) was introduced as one of the best strengthening methods for civil structures. The structures strengthened with FRPs can improve the strengthening capacity and serviceability. Therefore, CFRP sheet and Glass Fiber-Steel Composite Plate (GSP) in this research were used for strengthening slabs of RC bridges. Experimental data from the strengthening will be helpful to better understand the effect of the strengthening and effective flexural rigidity.

• 한국구조물진단유지관리공학회 논문집
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• 제25권6호
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• pp.169-176
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• 2021

본 연구에서는 고온가열 이후의 탄소 보강근의 잔류 부착 강도 평가를 위하여 상온, 150℃에 따른 부착실험을 수행하였으며, 탄소 보강근과의 비교를 위한 D10 및 D13 철근도 고온 가열한 이후 잔류 부착 강도를 평가하였다. 실험 결과, 150℃ 가열 이후 탄소 보강근의 부착 강도는 상온 대비 약 9.94% 감소하였다. 반면 가열 이후 D10 철근 및 D13 철근 모두 탄소 보강근 대비 부착 강도 감소율이 적게 나타났다. 또한 온도 가열 이후 최대부착 강도에서 발생한 슬립도 탄소 보강근과 철근 모두 줄어드는 경향을 보였다. 이를 통해 고온가열에 따른 부착 강도와 슬립 감소의 상관관계를 확인하였으며, 부착-슬립 곡선을 나타내었다. 최종적으로는 실험 결괏값을 상대부착 강도로 나타냄으로써 가열 이후 탄소 보강근 및 철근의 잔류 부착성능을 확인하고자 하였다.

• Composites Research
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• 제30권3호
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• pp.215-222
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• 2017

에폭시 수지의 열적 특성과 접합 특성에 대해 다중벽 탄소 나노 튜브 (MWCNT)의 효과가 이중 중첩 전단시험에 의해 연구되었다. Epoxy/MWCNT 복합 수지는 에폭시 수지(araldite 2011)에 다양한 질량 분율로 MWCNT를 분산하여 제조되었다. MWCNT의 효과를 확인하기 위해 접합강도 시험이 열특성 변형 만능재료시험기에 의해 진행되었고 충격강도 시험이 ASTM D256에 따라 진행되었다. 금속 판재와 탄소섬유강화복합재료가 실험 재료로써 사용되었으며, 열적 안정성 분석은 열 중량 분석기와 시차 주사 열량기에 의해 진행되었다. 또한 접합강도 시험 후 시편의 형태학적 특성은 주사전자현미경에 의해 관찰되었고 파괴거동을 알아보기 위하여 광학현미경을 사용하였다. 에폭시 수지와 비교하였을 때 epoxy/MWCNT 복합 수지가 물리적 특성이 향상되는 것을 나타내었다.

• 한국구조물진단유지관리공학회 논문집
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• 제8권1호
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• pp.147-156
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• 2004

최근에 구조적인 손상을 입은 철근콘크리트 구조물은 내구성과 내력 향상을 위해 보수 보강이 필요하게 되었다. 본 연구에서는 철근콘크리트 보가 휨에 의해서 손상되었을 경우 손상이전의 상태로 내력복원을 할 수 있는지를 규명하고자 한다. 실험결과 기준실험체와 강판 탄소섬유시트 격자탄소섬유판으로 보강한 실험체를 비교할 때, 휨내력은 상승하였고, 연성도와 에너지흡수능력도 기준실험체에 비해 큰 차이를 보이지 않아 보강재인 강판 탄소섬유시트 격자탄소섬유판(복합재)은 R.C보의 휨보강재로 매우 우수한 성능을 보유하고 있다고 판단된다.

• Earthquakes and Structures
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• 제17권2호
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• pp.205-219
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• 2019

In Peru, construction of dwellings using confined masonry walls (CM) has a high percentage of acceptance within many sectors of the population. It is estimated that only in Lima, 80% of the constructions use CM and at least 70% of these are informal constructions. This mean that they are built without proper technical advice and generally have a high seismic vulnerability. One way to reduce this vulnerability is by reinforcing the walls. However, despite the existence of some reinforcement methods in the market, not all of them can be applied massively because there are other parameters to take into account, as economical, criteria for seismic improvement, reinforcement ratio, etc. Therefore, in this paper the feasibility of using five reinforcement techniques has been studied and compared. These reinforcements are: welded mesh (WM), glass fiber reinforced polymer (GFRP), carbon fiber reinforced polymer (CFRP), steel bar wire mesh (CSM), steel reinforced grout (SRG). The Multi-Criteria Decision Making (MCDM) method can be useful to evaluate the most optimal strengthening technique for a fast, effective and massive use plan in Peru. The results of using MCDM with 10 criteria indicate that the Carbon Fiber Reinforced Polymer (CFRP) and Steel Reinforced Grout (SRG) methods are the most suitable for a massive reinforcement application in Lima.

• Steel and Composite Structures
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• 제48권5호
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• pp.599-610
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• 2023

To avoid debonding failure, a novel type of hybrid anchorage (HA) is proposed in this study that uses a slotted plate to lock the ends of the fiber-reinforced polymer (FRP) sheet in addition to the usual bonding over the substrate of the strengthened member. An experimental investigation was performed on three groups of RC beams, which differed from one another in either concrete strength or steel reinforcement ratio. The test results indicate that the end self-locking of the CFRP sheet can improve the failure ductility, ultimate capacity of the beams and its utilization ratio. Although intermediate debonding occurred in all the strengthened beams, it was not a fatal mode of failure for the three specimens with end anchorage. Among them, FRP rupture occurred in the beam with higher concrete strength and lower steel reinforcement ratio, whereas the other two failed by concrete crushing. The beam strengthened by HA obtained a relatively high percentage of increase in ultimate capacity when the rebar ratio or concrete strength decreased. The expressions in the literature were inspected to calculate the critical loads at intermediate debonding, FRP rupturing and concrete crushing after debonding for the strengthened beam. Then, the necessity of further research is addressed.

• Steel and Composite Structures
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• 제47권6호
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• pp.781-794
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• 2023

In order to directly apply seawater and sea sand in construction without desalination, a type of square concrete-filled steel tube (CFST) encased with prefabricated seawater sea-sand concrete filled Polyvinyl Chloride (PVC)/Glass Fiber Reinforced Polymer (GFRP) tube column was proposed. Twenty short columns were tested under uniaxial loads, and the test parameters included inner tube types, seawater sea-sand concrete replacement ratios, concrete strength, the wrapping area of Carbon Fiber Reinforced Polymer (CFRP) strips and the thickness of GFRP tube. The effects of the parameters on failure modes, loading capacity, ductility and strain responses were discussed. All the tested specimens failed with serious buckling of the steel tubes and fracture of the inner tubes. The specimens had good residual bearing capacity corresponding to 64% to 88.9% of the peak capacity. The inner GFRP tubes and PVC tubes wrapped by CFRP strips provided stronger confinement to the core concrete, and were good choices for the proposed columns. Moreover, an analytical model for the composite column with different inner tube types was proposed.

• 한국구조물진단유지관리공학회 논문집
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• 제22권1호
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• pp.199-207
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• 2018

이형철근과 FRP 보강근의 복합 이중근을 갖는 FRC 보의 휨성능을 평가하기 위하여 실험이 수행되었다. 인장근의 종류(CFRP 보강근, GFRP 보강근, 철근)과 PVA 섬유 혼입률(0.5%, 0%)을 주요변수로 한 7개의 실험체를 제작하였다. 유한요소해석을 통하여 FRC 보의 균열 및 휨거동을 예측하기 위한 해석적 방법이 제안되고 분석되었다. 복합 이중근을 가지는 실험체들에서 철근으로 이중근을 가지는 실험체가 철근과 FRP 보강근을 이단으로 배치한 실험체들에 비하여 26~34% 균열하중이 큰 것으로 나타났다. 최대 휨강도에서는 복합 이중근을 가지는 실험체들 중 CFRP 보강근을 최외측으로 한 실험체가 가장 큰 내력을 나타내었다. 해석과 실험을 통한 휨강도를 비교한 결과, 강도비는 평균 1.2, 표준편차 0.085, 최대 오차율은 22% 등으로 나타났다. 이러한 결과에서 본 연구의 유한요소해석방법이 복합 이중근을 가지는 보의 실제 거동을 효과적으로 표현할 수 있음을 알 수 있다.

• Steel and Composite Structures
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• 제14권1호
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• pp.41-55
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• 2013

Fiber reinforced polymers (FRP) materials are increasingly being used for strengthening and repair of steel structures. An issue that concerns engineers in steel members which are retrofitted with FRP is stress experienced due to temperature changes. The changing temperature affects the interface bond between the FRP and Steel. This research focused on the effects of cyclical thermal loadings on the interface properties of FRP bounded to steel members. Over fifty tests were conducted to investigate the thermal effects on bonding between FRP and steel, which were cycled from temperature of $-11^{\circ}C$ ($12^{\circ}F$) to $60^{\circ}C$ ($140^{\circ}F$) for 21-36 days. This investigation consisted of two test protocols, 1) the tensile test of epoxy resin, tack coat, FRP and FRP-steel plate, 2) tensile test of each FRP compound and FRP with steel after going through thermal cyclic loading. This investigation reveals an extensive reduction in the composite's strength.