• 한국정밀공학회지
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• 제18권10호
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• pp.148-153
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• 2001

Active control of flexural vibrations of smart laminated composite beams has been carried out using piezoceramic sensor/actuator and viscoelastic material. The beams with passive constrained layer damping hale been analyzed by formulating the equations of motion through the use of extended Hamilton's principle. The dynamic characteristics such as damping ratio and modal damping of the beam are calculated for various fiber orientations by means of iterative complex eigensolution method. This paper addresses a design strategy of laminated composite under flexural vibrations to design structure with maximum possible damping capacity.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2022년도 봄 학술논문 발표대회
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• pp.146-147
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• 2022

Exposed composite beams composed of H-beams and concrete slabs are generally used in building structures because of their excellent economics and flexural strength. However, deep beams used under large load often make difficulties in construction. In this study, an exposed composite beam with high strength steel (SM460) used in the bottom flange of built-up H-shaped beam, so-called S-Beam, was proposed in order to reduce beam depth. And its positive and negative flexural strengths were experimentally evaluated. The test results showed that S-Beam has excellent flexural strength and ductility.

• 한국강구조학회 논문집
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• 제28권2호
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• pp.109-120
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• 2016

본 연구에서는 콘크리트 채움 U형 하이브리드 합성보의 실물대 휨 실험을 수행하고 평가하였다. U형 강판의 웨브에는 공칭인장강도 400MPa 일반강종의 강재(SS400) 하부플랜지에는 공칭인장강도 570MPa 고강도 강재(SM570)의 강판을 각각 적용하였다. 연구의 주요 목적은 최대의 휨성능을 발현할 수 있는 하이브리드 단면구성과 설계지침의 개발이었다. 4점 단조가력실험의 수행을 통해 제안된 모든 하이브리드 합성보 실험체들은 의도한대로 소성모멘트 이상의 강도발현과 충분한 연성거동을 나타내었다. 그리고 하이브리드 합성단면의 소성중립축의 위치가 상부 콘크리트 기준으로 합성단면 전체깊이의 15%이내에 존재할 경우 휨강도 산정 시 소성응력분포법의 적용이 가능할 것으로 판단되었다. 또한 실험결과를 기반으로 하이브리드 합성보에 적합한 강성산정과정을 제안하였다.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2002년도 추계학술발표대회 논문집
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• pp.208-211
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• 2002

In RC beams strengthened with Epoxy-Bonded Fiber, debonding failure happens frequently. Moreover, through the life cycle, it is difficult to recognize clacks and deflections on the surface of concrete members strengthened with Epoxy- Bonded Fiber. For these reasons, we must always monitor the state of RC beams. The Optical FBG sensor is broadly accepted as a structural health monitoring device. The main objective of this paper is that it's possible to monitoring the debonding failure of R.C. beams strengthened with Epoxy-Bonded Fiber. For that, we fixed two Optical FBG sensors at the center of the beam and another two sensors in the end of Epoxy-Bonded Fiber, According to the comparison micro-strain between embeded sensor in concrete and that on the fiber surface, we can find the point which debonding failure occurs

• Composites Research
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• 제20권3호
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• pp.8-16
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• 2007

자동차 충돌이나 전복사고에 있어서 부재들의 변형은 축방향 압축붕괴와 함께 굽힘붕괴가 혼합된 변형양상을 보여주고 있으며, 자동차에 사용되는 대부분의 박벽관 부재는 굽힘붕괴가 주된 붕괴형태로 나타나고 있다. 하지만 혼성 사각관의 굽힘붕괴에 대한 연구는 축방향 붕괴의 연구에 비해 많이 부족한 현실이다. 본 논문에서는 알루미늄-복합재료 혼성 사각관의 굽힘 붕괴 거동 및 에너지 흡수 특성을 실험적 방법으로 연구하여 경량화 구조부재로서의 적용가능성을 조사하였다. 접착필름 살입형 경화법으로 제작된 알루미늄-복합재료 혼성 사각관 보에 대해 복합 재료 층의 적층두께와 적층 각에 따른 굽힘 성능을 평가하였다. 본 혼성 사각관 보는 복합재료만으로 구성된 사각관 보에서 발생할 수 있는 불안정한 붕괴모드를 안정적인 붕괴로 전환시키면서, 단순 알루미늄 사각관에 비해 에너지 흡수 능력이 향상되었고, 특히 $[0^{\circ}/90^{\circ}]s$를 적층한 혼성 사각관의 경우 벽두께 1mm인 알루미늄 사각관 시험편과 비교하여 흡수에너지가 1.78배 증가하였고 단위무게당 흡수에너지는 1.29배로 증가함을 보였다.

• Coupled systems mechanics
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• 제10권2호
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• pp.161-184
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• 2021

Strengthening of reinforced concrete beams with externally bonded fiber reinforced polymer plates/sheets technique has become widespread in the last two decades. Although a great deal of research has been conducted on simply supported RC beams, a few studies have been carried out on continuous beams strengthened with FRP composites. This paper presents a simple uniaxial nonlinear analytical model that is able to accurately estimate the load carrying capacity and the behaviour of damaged RC continuous beams flexural strengthened with externally bonded prestressed composite plates on both of the upper and lower fibers, taking into account the thermal load. The model is based on equilibrium and deformations compatibility requirements in and all parts of the strengthened beam, i.e., the damaged concrete beam, the FRP plate and the adhesive layer. The flexural analysis results and analytical predictions for the prestressed composite strengthened damaged RC continuous beams were compared and showed very good agreement in terms of the debonding load, yield load, and ultimate load. The use of composite materials increased the ultimate load capacity compared with the non strengthened beams. The major objective of the current model is to help engineers' model FRP strengthened RC continuous beams in a simple manner. Finally, this research is helpful for the understanding on mechanical behaviour of the interface and design of the FRP-damaged RC hybrid structures.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2001년도 가을 학술발표회 논문집
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• pp.515-520
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• 2001

This study discusses the flexural performance of rehabilitated composite sections, consisting originally of R/C beams and subsequently strengthened by, Hybrid Fiber Reinforced Polymers(FRPs) and adhesives. Experimentations were peformed with 8 specimens to compare the rehabilitated effect of the length of FRPs, 2plies of FRPs, and 3plies of FRPs. The results show that the increase of the FRP strengthening length is effective on the flexural capacity and strength. Also, R.C beams retrofitted with hybrid FRPs are more effective on the increase of flexural capacity, strength, stiffness, and ductility than with a single kind of FRPs.

• Structural Engineering and Mechanics
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• 제70권6호
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• pp.751-763
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• 2019

Steel-concrete composition is widely used in the construction due to efficient utilization of materials. The service load behavior of composite structures is significantly affected by cracking, creep and shrinkage effects in concrete. In order to control these effects in concrete slab, an efficient and novel strategy has been proposed by use of fiber reinforced concrete near interior supports of a continuous beam. Numerical study is carried out for the control of cracking, creep and shrinkage effects in composite beams subjected to service load. A five span continuous composite beam has been analyzed for different lengths of fiber reinforced concrete near the interior supports. For this purpose, the hybrid analytical-numerical procedure, developed by the authors, for service load analysis of composite structures has been further improved and generalized to make it applicable for composite beams having spans with different material properties along the length. It is shown that by providing fiber reinforced concrete even in small length near the supports; there can be a significant reduction in cracking as well as in deflections. It is also observed that the benefits achieved by providing fiber reinforced concrete over entire span are not significantly more as compared to the use of fiber reinforced concrete in certain length of beam near the interior supports in continuous composite beams.

• Advances in concrete construction
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• 제8권1호
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• pp.9-19
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• 2019

This paper describes an experimental investigation on hybrid fiber reinforced concrete (HYFRC) beams. And the main aim of this present paper is to examine the dynamic characteristics and damage evaluation of undamaged and damaged HYFRC beams under free-free constraints. In this experimental work, totally four RC beams were cast and analyzed in order to evaluate the dynamic behavior as well as static load behavior of HYFRCs. Hybrid fiber reinforced concrete beams have been cast by incorporating two different fibers such as steel and polypropylene (PP). Damage of HYFRC beams was obtained by cracking of concrete for one of the beams in each set under four-point bending tests with different percentage variation of damage levels as 50%, 70% and 90% of maximum ultimate load. And the main dynamic characteristics such as damping, fundamental natural frequencies, mode shapes and frequency response function at each and every damage level has been assessed by means of non-destructive technique (NDT) with hammer excitation. The fundamental natural frequency and damping values obtained through dynamic tests for HYFRC beams were compared with control (reference) RC beam at each level of damage which has been acquired through static tests. The static experimental test results emphasize that the HYFRC beam has attained higher ultimate load as compared with control reinforced concrete beam.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1999년도 학회창립 10주년 기념 1999년도 가을 학술발표회 논문집
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• pp.549-552
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• 1999

Recently, a variety of uses for combined reinforced concrete and steel have been applied in actual construction, which are called hybrid structures. The purpose of the hybrid construction is the high-efficiency of structural behaviors. But the design method of SRC is relatively complicated design method. So, it hasn't detailed design method yet and we are depending upon foreign specifications. In this study, To develop the design method of SRC at the condition of composite behaviors, makes process about major factors that affects the composite behaviors. And we suggested fundamental data of the composite behaviors by experiments.