• Title/Summary/Keyword: Hybrid Structures

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Hybrid Effects of Carbon-Glass FRP Sheets in Combination with or without Concrete Beams

  • Kang, Thomas H.K.;Kim, Woosuk;Ha, Sang-Su;Choi, Dong-Uk
    • International Journal of Concrete Structures and Materials
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    • v.8 no.1
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    • pp.27-41
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    • 2014
  • The use of carbon fibers (CF) and glass fibers (GF) were combined to strengthen concrete flexural members. In this study, data of tensile tests of 94 hybrid carbon-glass FRP sheets and 47 carbon and GF rovings or sheets were thoroughly investigated in terms of tensile behavior. Based on comparisons between the rule of mixtures and test data, positive hybrid effects were identified for various (GF/CF) ratios. Unlike the rule of mixtures, the hybrid sheets with relatively low (GF/CF) ratios also produced pseudo-ductility. From the calibrated results obtained from experiments, a new analytical model for the stress-strain relationship of hybrid FRP sheets was proposed. Finally, the hybrid effects were verified by structural tests of concrete members strengthened with hybrid FRP sheets and either carbon or glass FRP sheets.

Experimental Study on Wave-Induced Hydraulic Pressure subjected to Bottom of Floating Structures (부유구조체 하면에 작용하는 파압에 대한 실험적 연구)

  • Jeong, Youn-Ju;You, Young-Jun;Lee, Du-Ho
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.31 no.6A
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    • pp.425-433
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    • 2011
  • In this study, in order to investigate the wave-induced buoyancy effects, experimental studies were conducted on pontoon-type floating structures. A series of small-scale tests with various wave cases were performed on the pontoon models. A total of four small-scale pontoon models with different lateral shapes and bottom details were fabricated and tested under the five different wave cases. Six hydraulic pressure gauges were attached to the bottom surfaces of the pontoon models and the wave-induced hydraulic pressure was measured during the tests. Finally, hydraulic pressures subjected to the bottoms of the pontoon models were compared with each other. As the results of this study, it was found that whereas the waffled bottom shape hardly influenced the wave-induced hydraulic pressure, the hybrid lateral shape significantly influenced the wave-induced hydraulic pressure subjected on the bottoms of floating structures. The air gap effects of the hybrid shape contribute to decreasing the wave-induced hydraulic pressure due to absorption of wave impact energy. Compared with box type, the hydraulic pressures of the hybrid type were about 83% at the bow, 74% at the middle, and 53% at the stern.

Case Studies of the Participation Structures in Secondary Science Classrooms: Exploring the Possibility to Develop the 'Space for Hybrid Meaning Making' (중등 과학 수업의 참여구조 사례 연구: '혼성적 의미 창출 공간'의 형성 가능성 탐색)

  • Yu, Eun-Jeong;Lee, Sun-Kyung;Oh, Phil-Seok;Shin, Myeong-Kyeong;Kim, Chan-Jong
    • Journal of The Korean Association For Science Education
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    • v.28 no.6
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    • pp.603-617
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    • 2008
  • Inspired by the socio-cultural perspective on teaching and learning science, we have explored how the teacher and students interact with one another and develop meanings in science classrooms. Data came from four 10th grade science classrooms, and video recordings and verbatim transcripts of the lessons were analyzed. Focus of the analysis was on the participation structures as well as the possibility of developing the space for hybrid meaning making. The participation structures identified were mainly teacher-led, and students rarely took an active stance to initiate an opportunity for generating new meanings. However, some participation structures had the potential to develop a new discursive space in which hybrid meaning can be constructed through negotiation between participants. Implications for future research and more desirable educational practices were discussed based on the result.

An effective online delay estimation method based on a simplified physical system model for real-time hybrid simulation

  • Wang, Zhen;Wu, Bin;Bursi, Oreste S.;Xu, Guoshan;Ding, Yong
    • Smart Structures and Systems
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    • v.14 no.6
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    • pp.1247-1267
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    • 2014
  • Real-Time Hybrid Simulation (RTHS) is a novel approach conceived to evaluate dynamic responses of structures with parts of a structure physically tested and the remainder parts numerically modelled. In RTHS, delay estimation is often a precondition of compensation; nonetheless, system delay may vary during testing. Consequently, it is sometimes necessary to measure delay online. Along these lines, this paper proposes an online delay estimation method using least-squares algorithm based on a simplified physical system model, i.e., a pure delay multiplied by a gain reflecting amplitude errors of physical system control. Advantages and disadvantages of different delay estimation methods based on this simplified model are firstly discussed. Subsequently, it introduces the least-squares algorithm in order to render the estimator based on Taylor series more practical yet effective. As a result, relevant parameter choice results to be quite easy. Finally in order to verify performance of the proposed method, numerical simulations and RTHS with a buckling-restrained brace specimen are carried out. Relevant results show that the proposed technique is endowed with good convergence speed and accuracy, even when measurement noises and amplitude errors of actuator control are present.

A Study on the Lightweight Design of Hybrid Modular Carbody Structures Made of Sandwich Composites and Aluminum Extrusions Using Optimum Analysis Method (최적화 해석기법을 이용한 샌드위치 복합재와 알루미늄 압출재 하이브리드 모듈화 차체구조물의 경량 설계 연구)

  • Jang, Hyung-Jin;Shin, Kwang-Bok;Han, Sung-Ho
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.36 no.11
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    • pp.1335-1343
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    • 2012
  • In this study, the lightweight modular design of hybrid railway carbody structures made of sandwich composites and aluminum extrusions was investigated by using topology and size optimization techniques. The topology optimum design was used to select the best material for parts of the carbody structure at the initial design stage, and then, the size optimum design was used to find the optimal design parameters of hybrid carbody structures using first-order and sub-problem methods. Through the topology optimization analysis, it was found that aluminum extrusions were suitable for primary members such as the underframe and lower side panel module to improve the stiffness and manufacturability of the carbody structures, and sandwich composites were appropriate for secondary members such as the roof and middle side panel module to minimize its weight. Furthermore, the results obtained by size optimization analysis showed that the weight of hybrid carbody structures composed of aluminum extrusions and sandwich composites could be reduced by a maximum of approximately 17.7% in comparison with carbody structures made of only sandwich composites.

Vibration Control Performance Evaluation of Hybrid Mid-Story Isolation System for a Tall Building (하이브리드 중간층 지진격리시스템의 고층 건물 진동 제어 성능 평가)

  • Kim, Hyun-Su;Kang, Joo-Won
    • Journal of Korean Association for Spatial Structures
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    • v.18 no.3
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    • pp.37-44
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    • 2018
  • A base isolation system is widely used to reduce seismic responses of low-rise buildings. This system cannot be effectively applied to high-rise buildings because the initial stiffness of the high-rise building with the base isolation system maintains almost the same as the building without the base isolation system to set the yield shear force of the base isolation system larger than the design wind load. To solve this problem, the mid-story isolation system was proposed and applied to many buildings. The mid-story isolation system has two major objectives; first to reduce peak story drift and second to reduce peak drift of the isolation story. Usually, these two objectives are in conflict. In this study, a hybrid mid-story isolation system for a tall building is proposed. A MR (magnetorheological) damper was used to develop the hybrid mid-story isolation system. An existing building with mid-story isolation system, that is "Shiodome Sumitomo Building" a high rise building having a large atrium in the lower levels, was used for control performance evaluation of the hybrid mid-story isolation system. Fuzzy logic controller and genetic algorithm were used to develop the control algorithm for the hybrid mid-story isolation system. It can be seen from analytical results that the hybrid mid-story isolation system can provide better control performance than the ordinary mid-story isolation system and the design process developed in this study is useful for preliminary design of the hybrid mid-story isolation system for a tall building.

Optimal Design of Hybrid Control System through Inter-Building Connection (빌딩간 연결을 통한 복합제어시스템의 최적설계)

  • Park, Kwan-Soon;Ok, Seung-Yong
    • Journal of the Korean Society of Safety
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    • v.32 no.6
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    • pp.81-88
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    • 2017
  • This study deals with the optimal design of a hybrid control system composed of a combination of active control system and passive control system for effective seismic performance improvement of two adjacent structures. The proposed hybrid control system adopts a configuration of installing an active control device in one building and connecting two adjacent structures with a passive control device so that the one-side active control force can be bi-directionally applied to both buildings through the passive connecting devices. In order to derive the optimal performance of the proposed system, the design parameters of the passive and active control systems were searched using the genetic algorithm. Numerical simulations of 10-story and 8-story buildings have been performed to verify the effectiveness of the proposed technique. For the purpose of comparison, the conventional independent control system with two identical active control systems being installed separately for each structure was also optimally designed and its seismic response has been evaluated as well. From the comparative results of the two control systems, it is demonstrated that the proposed hybrid control system requires larger control force for its one-side active control device than the conventional independent control system does for each of both-side active devices, but quite less than the total control force required for both-side devices of the independent control system, while maintaining similar seismic performance. Therefore, the proposed system is more economical and reliable than the conventional independent control system with two identical active devices.

Numerical study on Floor Response Spectrum of a Novel High-rise Timber-concrete Structure

  • Xiong, Haibei;Zheng, Yingda;Chen, Jiawei
    • International Journal of High-Rise Buildings
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    • v.9 no.3
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    • pp.273-282
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    • 2020
  • An innovative high-rise timber-concrete hybrid structure was proposed in previous research, which is composed of the concrete frame-tube structure and the prefabricated timber modules as main structure and substructures, respectively. Considering that the timber substructures are built on the concrete floors at a different height, the floor response spectrum is more effective in estimating the seismic response of substructures. In this paper, the floor response spectra of the hybrid structure with different structural parameters were calculated using dynamic time-history analysis. Firstly, one simplified model that can well predict the seismic response of the hybrid structure was proposed and validated. Then the construction site, the mass ratio and the frequency ratio of the main-sub structure, and the damping ratio of the substructures were discussed. The results demonstrate that the peaks of the floor response spectra usually occur near the vibration periods of the whole structure, among which the first two peaks stand out; In most cases, the acceleration amplification effect on substructures tends to be more evident when the construction site is farther from the fault rupture; On the other hand, the acceleration response of substructures can be effectively reduced with an appropriate increase in the mass ratio of the main-sub structure and the damping ratio of the substructures; However, the frequency ratio of the main-sub structure has no discernible effect on the floor response spectra. This study investigates the characteristics of the floor response spectrum of the novel timber-concrete structure, which supports the future applications of such hybrid structure in high-rise buildings.

A Study on Failure Evaluation of Korean Low Floor Bus Structures Made of Hybrid Sandwich Composite (하이브리드 샌드위치 복합재 초저상버스 구조물의 파손 평가 연구)

  • Lee, Jae-Youl;Shin, Kwang-Bok;Lee, Sang-Jin
    • Transactions of the Korean Society of Automotive Engineers
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    • v.15 no.6
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    • pp.50-61
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    • 2007
  • The structural stiffness, strength and stability on the bodyshell and floor structures of the Korean Low Floor Bus composed of laminate, sandwich panels and metal reinforced frame were evaluated. The laminate composite panel and facesheet of sandwich panel were made of WR580/NF4000 glass fabric/epoxy laminate, while aluminum honeycomb or balsa was applied to the core materials of the sandwich panel. A finite element analysis was used to verify the basic design requirements of the bodyshell and the floor structure. The use of aluminum reinforced frame and honeycomb core was beneficial for weight saving and structural performance. The symmetry of the outer and inner facesheet thickness of sandwich panels did not affect the structural integrity. The structural strength of the panels was evaluated using Von-Mises criterion for metal structures and total laminate approach criterion for composite structures. All stress component of the bodyshell and floor structures were safely located below the failure stresses. The total laminate approach is recommended to predict the failure of hybrid sandwich composite structures at the stage of the basic design.