• 한국구조물진단유지관리공학회 논문집
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• 제11권5호
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• pp.153-159
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• 2007

이 논문은 FRP시스템 외부부착공법의 조기 탈착문제를 개선하기 위해 개발된 유리섬유-강 복합판(GFSP)으로 보강된 RC보의 성능 및 파괴특성에 관한 실험적 연구다. 사용 중인 보의 손상과 재하상황을 실제적으로 모의하기 위하여, 사전균열과 반복하중이 실험변수로 채택되었다. 실험에서 GFSP 보강은 보의 강도증가, 처짐감소, 균열의 억제 등에 매우 효과적인 보강공법임이 확인되었다. 그러나 GFSP로 보강되는 보의 설계는 휨 성능에서 유리섬유의 취성거동을 고려하여야 하는 것을 보여주었다.

• Earthquakes and Structures
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• 제27권2호
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• pp.97-111
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• 2024

In this paper, buckling conditions and retrofitting of cylindrical steel water storage tanks with different roof types and wall thicknesses were investigated by using finite element method. Four roof types of cylindrical steel tanks which are open-top, flat-closed, conical-closed and torispherical-closed and three wall thicknesses of 4, 6 and 8 mm were considered in FE modeling of cylindrical steel tanks. The roof shapes significantly affect load distribution on the tank shell under the seismic action. Composite FRP materials are widely used for winding thin-walled cylindrical steel structures. The retrofitting efficiency of cylindrical steel water tank is tested under the seismic loading with the externally bonded CFRP laminates. In retrofitting of cylindrical steel tank, the CFRP composite material coating method was used to improve of seismic performance of cylindrical steel tanks. ANSYS software was used to analyze the cylindrical steel tanks and maximum equivalent (von-Mises) and directional deformation were obtained. Equivalent (von-Mises) stresses significantly decreased due to the coating of the tank shell with FRP composite material. In thin-walled steel structures, excessive stress causes buckling and deformations. Therefore, retrofitting led to decrease in stress, reductions in directional and buckling deformation of the open-top, flat-closed, conical-closed and torispherical-closed tanks.

• 콘크리트학회논문집
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• 제17권6호
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• pp.903-910
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• 2005

최근 철근콘크리트 구조물의 보강 방법으로 고인장강도를 갖는 섬유복합체를 부재의 외부에 부착시켜 휨 내력을 증진시키는 부착식 보강공법이 널리 사용되고 있으나, 부착되는 섬유복합체의 박리에 의한 파괴강도를 예측하여 설계식에 반영하기 위한 연구는 미흡한 것이 사실이다. 보강재의 박리에 의한 파괴는 부재 전체의 취성적인 파괴를 유도하게 되므로, 부재의 보강설계를 위해서는 이에 대한 검토가 필수적으로 요구되어 진다. 본 연구에서는 보강재의 부착강도에 큰 영향을 미치는 유효부착길이의 개념을 도입하여, 기존 연구 결과로부터 부재의 부착강도를 좌우하게 되는 유효부착길이를 산정 하였으며, 이와 같은 유효부착길이에 의한 보강재의 박리하중을 산정할 수 있는 설계식을 제안하였다. 제안된 설계식은 기존 연구자들의 실험 연구결과와 비교하여 그 신뢰성을 검증하도록 하였으며, 기존 연구자들의 제안식과의 비교를 통하여 본 제안식의 타당성을 증명하였다.

• Structural Engineering and Mechanics
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• 제61권3호
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• pp.397-406
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• 2017

The use of fiber reinforced polymer (FRP) for torsional strengthening of reinforced concrete (RC) single cell box beams has been analyzed considerably by researchers worldwide. However, little attention has been paid to torsional strengthening of multicell box girders in terms of both experimental and numerical research. This paper reports the experimental work in an overall investigation for torsional strengthening of multicell box section RC girders with externally-bonded Carbon Fiber Reinforced Polymer CFRP strips. Numerical work was carried out using non-linear finite element modeling (FEM). Good agreement in terms of torque-twist behavior, steel and CFRP reinforcement responses, and crack patterns was achieved. The unique failure modes of all the specimens were modeled correctly as well.

• Structural Monitoring and Maintenance
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• 제7권3호
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• pp.233-259
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• 2020

Using bonded fiber-reinforced polymer laminates for strengthening wooden structural members has been shown to be an effective and economical method. In this research, properties of suitable composite materials (sika wrap), adhesives and two ways of strengthening beams exposed to bending moment are presented. Passive or slack reinforcement is one way of strengthening. The most effective way of such a strengthening was to place reinforcement laminates in the stretched part of the wooden beam (lower part in our case), in order to investigate the effectiveness of externally bonding FRP to their soffits. The model is based on equilibrium and deformations compatibility requirements in and all parts of the strengthened beam, i.e., the wooden beam, the sika wrap composite plate and the adhesive layer. The theoretical predictions are compared with other existing solutions. This research is helpful for the understanding on mechanical behaviour of the interface and design of the composite-wooden hybrid structures. The results showed that the use of the new strengthening system enhances the performance of the wooden beam when compared with the traditional strengthening system.

• Structural Engineering and Mechanics
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• 제26권4호
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• pp.427-439
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• 2007

The exploitation of fibre reinforced polymer composites, as external reinforcement is an evergreen and well-known technique for improving the structural performance of reinforced concrete structures. The demand to use FRP composites in the civil engineering industry is mainly due to its high strength, light weight, and stiffness. This paper exemplifies the shear strength of partially precracked reinforced concrete rectangular beams repaired with externally bonded Bi-Directional Carbon Fibre Reinforced Polymer (CFRP) Fabrics strips. All specimens were cast in the laboratory environment without any internal shear reinforcement. The test parameters were longitudinal tensile reinforcement, shear span to effective depth ratio, spacing of CFRP strips, and orientation of CFRP reinforcement. It mainly focuses on the shear capacity and modes of failure of the CFRP strengthened shear beams. Results have shown that the CFRP repaired beams attained a shear enhancement of 32% and 107.64% greater than the control beams. This study underscores that the CFRP strip technique significantly enhanced the shear capacity of precracked reinforced concrete rectangular beams without any internal shear reinforcement.

• Computers and Concrete
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• 제27권2호
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• pp.131-141
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• 2021

This paper aims at investigating the capability of different FRP/concrete interface models to predict the effect of carbon nanotubes on the flexural behavior of RC beams strengthened with CFRP. Three different interfacial bond models are proposed to simulate the adhesion between CFRP composites and concrete, namely: full bond, nonlinear spring element, and cohesive zone model. 3D Nonlinear finite element model is developed then validated using experimental work conducted by the authors in a previous investigation. Cohesive zone model (CZM) has the best agreement with the experimental results in terms of load-deflection response. CZM is the only bond model that accurately predicted the cracks patterns and failure mode of the strengthened RC beams. The FE model is then expanded to predict the effect of bond strength on the flexural capacity of RC beams strengthened with externally bonded CNTs modified CFRP composites using CZM bond model. The results reveal that the flexural capacity of the strengthened beams increases with increasing the bond strength value. However, only 23% and 22% of the CFRP stress and strain capacity; in the case of full bond; can be utilized before failure.