• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2004년도 추계 학술발표회 제16권2호
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• pp.17-20
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• 2004

FRP strengthening system that bonds FRP sheet or laminate underneath structure has been used popularly thesedays. The failure of this bonding system occurs mainly at the interface of bonded surface abruptly. So it is difficult to expect the failure and FRP can't show its full material capacity that makes it uneconomically. By that reason, KICT proposed a system to install FRP aminate to structure for strengthening not by bondging but by unbonding. It is to install both ends of FRP laminate by anchoring underneath structure without bonding. Then, the failure is not an interfacial problem any more, it is governed by mechanical anchoring. This paper includes an experimental study about anchoring system for prestressing CFRP laminate.

• 한국안전학회지
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• 제26권6호
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• pp.54-63
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• 2011

Steel plate or FRP materials have been typically used for the seismic retrofit of civil infrastructures. In order to overcome the limitation of each retrofitting material, a composite material, which takes advantages from both metal and fiber polymer materials, has been developed. In the study herein, the composite retrofitting material consists of metal part(steel or aluminum) and FRP sheet part(glass or carbon fiber). The metal part can enhance the ductility and the FRP part the ultimate strength. As a preliminary study to investigate the fundamental mechanical characteristics of the metal-FRP laminated composite material this study performed the tensile test with various experimental variables including the number, the angle and the combination of FRP laminates. From the test results, both aluminum and steel-FRP laminate composite material showed increased fracture toughness. However, the angle and the kind of fibers should be carefully considered in conjunction with the expected loading conditions. In general, steel-FRP laminate composite showed better tensile performance in regards to the seismic retrofit purposes.

• 한국안전학회지
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• 제27권1호
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• pp.55-62
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• 2012

Steel plate or FRP materials have been typically used for the seismic retrofit of civil infrastructures. In order to overcome the limitation of each retrofitting material, a composite material, which takes advantages from both metal and fiber polymer materials, has been developed. In the study herein, the composite retrofitting material consists of metal part(steel or aluminum) and FRP sheet part(glass or carbon fiber). The metal part can enhance the ductility and the FRP part the ultimate strength. As a preliminary study to investigate the fundamental mechanical characteristics of the metal-FRP laminated composite material this study performed the flexural fracture test with various experimental variables including the number, the angle and the combination of FRP laminates. From the aluminum-FRP composite tests no great increase in flexural strength and flexural toughness were observed. However, flexural toughness of steel-FRP laminate composite was increased so that its behavior can be considered in the retrofit design. In addition, the angle and the kind of fibers should be carefully considered in conjunction with the expected loading conditions.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2010년도 춘계 학술대회 제22권1호
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• pp.73-74
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• 2010

콘크리트 보의 휨 보강을 위한 FRP 플레이트가 콘크리트 하면에 직접 부착될 경우 콘크리트-FRP 부착경계면에서 대부분 콘크리트 박리파괴에 의한 최종파괴가 주로 발생된다. 본 연구에서는 이들 콘크리트 박리에 의한 취성파괴를 지연시켜 부착 보강재의 수명을 보다 더 연장시키기 위하여 콘크리트와 보강재 접착경계면 사이에 얇은 두께의 중간 삽입재(알루미늄, 티타늄)를 앵커와 에폭시로 부착, 기존의 FRP 플레이트 보강방법 보다 개선된 휨 성능 보강방법에 관한 연구이다. 이를 위하여 본 연구에서는 상대적으로 가격이 저렴한 알루미늄과 재료적 성능이 우수한 티타늄을 중간삽입제로 이용, 콘크리트와 보강재 사이의 부착하였으며 이들의 활용에 따른 휨 연성 개선과 콘크리트 박리파괴 지연에 대한 효과를 측정하였다.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2002년도 가을 학술발표회 논문집
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• pp.17-24
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• 2002

인발성형 적층 FRP 복합소재의 재료상수는 일반적으로 시편실험을 통해 구해지고 있으나, 본 논문에서는, 실험에서 구한 탄성계수가 부재일 경우를 위해, Micromechanics와 Classical Laminate Theory (CLT)를 이용한 적층 FRP 복합재료의 탄성계수(E/sub L/과 E/sup b//sub L/) 예측모델을 제시하였다 또한 예측모델로부터 구한 값과 실험으로부터 얻은 실측값을 비교하여 그 적정성을 검증하였고, 예측모델의 민감도 및 확률적인 특성을 구성소재 (Constituents)의 재료특성에 근거해 평가하였다.

• 한국공간정보시스템학회:학술대회논문집
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• 한국공간정보시스템학회 2004년도 춘계 학술발표회 논문집 제1권1호(통권1호)
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• pp.206-211
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• 2004

This paper deals with the flexural strengthening of reinforced concrete beams by means of thin fiber reinforced plastic(FRP) laminas. This study focuses on modeling of structural of concrete bonded FRP laminate in flexural bending members. Used computational equation is derived by relation of stress and strain. The section analysis is based on experimental observations of a linear strain distribution in the cross section until failure, and a multi-linear moment-deflection curve that is divided into four regions, each terminated by a similarly numbered point. The load-deflection relationship in each region is assumed to be linear. The present model is validated to compare wit the experiment of 4-point bending tests of R/C rectangular beams strengthened with CFRP laminates, and has well predicted the moment-displacement relationships of members.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 추계 학술발표회 논문집
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• pp.317-320
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• 2006

In order to determine a minimum thickness of the pultruded GFRP panel as a structural member, some experimental studies were performed. GFRP tubes with 2mm, 4mm, 6mm thickness were manufactured by pultrusion process. First, coupon tests for finding mechanical properties were carried out. Comparisons between test results and analysis results based on classical laminate theory showed large differences in case of 2mm, 4mm specimens. The reason is that it is difficult to apply appropriate pultruding force and keep layered stitched fabric flat for the pultrusion process of complex shaped FRP member with small thickness. On the consequence, we decide 6mm as a minimum thickness of FRP member. Second, 4-point bending tests were performed and the results with compared with numerical analysis. The behavior of FRP tube can be exactly predicted by numerical analysis if buckling analysis is included.

• 한국해양공학회지
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• 제33권6호
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• pp.495-503
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• 2019

Approximately 90,000 ships are registered in South Korea, and about 80,000 of these ships are used in domestic shipping. Among these, 84% are small ships, such as a fishing vessels that weigh less than 20 tons and are made mostly of an FRP (Fiber Reinforced Plastics). When this fact is taken into account, the greenhouse gas emissions that are released per ton of a composite vessel are sizeable. In this study, the laminated structures of an FRP fishing vessel, many of which currently are being built in Korea, were analyzed by ISO (International Organization for Standardization) and international design rules, and the structures of the hulls are lightweight with optimum glass fiber mass content as determined by the laminate weight minimization algorithm. As a result, it was confirmed that the laminations of the vessels in accordance with the Korean rule could have 6.4% to approximately 11% more design margin compared to the requirements of ISO and other international rules. And the case study of the application of the laminate weight minimization algorithm showed the possibility of reducing the weight of the hull bottom plating by as much as about 19.32% and by as much as about 18.06% in the overall structure.

• Steel and Composite Structures
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• 제50권2호
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• pp.183-199
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• 2024

In this paper, a closed-form rigorous solution for interfacial stress in continuous steel beam with variable section strengthened with bonded prestressed FRP plates and subjected to a uniformly distributed load is developed using linear elastic theory and including the variation of fiber volume fractions with a longitudinal orientation of the fibers of the FRP plates. The results show that there exists a high concentration of both shear and normal stress at the ends of the laminate, which might result in premature failure of the strengthening scheme at these locations. The theoretical predictions are compared with other existing solutions. Overall, the predictions of the different solutions agree closely with each other. A parametric study has been conducted to investigate the sensitivity of interface behavior to parameters such as laminate and adhesive stiffness, the thickness of the laminate and the fiber volume fractions where all were found to have a marked effect on the magnitude of maximum shear and normal stress in the composite member. This research gives a numerical precision in relating to the others studies which neglect the effect of prestressed plate and the shear lag impact. The physical and geometric properties of materials are taken into account, and that may play an important role in reducing the interfacial stresses magnitude.

• 대한기계학회논문집
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• 제19권4호
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• pp.1013-1022
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• 1995

A hybrid composite (APAL;Aramid Patched ALuminum alloy, CPAL;Carbon Patched ALluminum alloy), consisting of a Al 2024-T3 aluminum alloy plate sandwiched between two aramid/epoxy and carbon/epoxy laminate, was developed. Fatigue crack growth behavior was examined at stress ratios of R=0.2, 0.5. The APAL and CPAL showed superior fatigue crack growth resistance, which may be attributed to the crack bridging effect imposed by the intact fibers in the crack wake.