• 제목/요약/키워드: experimental substructure

검색결과 101건 처리시간 0.028초

다중전달 함수합성법을 이용한 구조물의 동특성 해석 (Structural Dynamic Analysis using Multi-FRF Synthesis Method)

  • 정재훈;지태한;박영필
    • 소음진동
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    • 제8권1호
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    • pp.139-145
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    • 1998
  • A great deal of effort has been invested in upgrading the performance and the efficiency of dynamic analysis of mechanical structures. Using experimental modal analysis(EMA) or finite element analysis(FEA) data of mechanical structures, the performance and efficiency can be effectively evaluated. In order to analyze complex structures such as automobiles and aircrafts, for the sake of computing efficiency, the dynamic substructuring techniques that allow to predict the dynamic behavior of a structure are widely used. Through linking a modal model obtained from EMA and an analytical model obtained from FEA, the best conditioned strucutres can be proposed. In this study, a new algorithm of substructre synthesis method, Multi-FRF synthesis method, is proposed to analyze a structure composed of many substructures.

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Real-time hybrid substructuring of a base isolated building considering robust stability and performance analysis

  • Avci, Muammer;Botelho, Rui M.;Christenson, Richard
    • Smart Structures and Systems
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    • 제25권2호
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    • pp.155-167
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    • 2020
  • This paper demonstrates a real-time hybrid substructuring (RTHS) shake table test to evaluate the seismic performance of a base isolated building. Since RTHS involves a feedback loop in the test implementation, the frequency dependent magnitude and inherent time delay of the actuator dynamics can introduce inaccuracy and instability. The paper presents a robust stability and performance analysis method for the RTHS test. The robust stability method involves casting the actuator dynamics as a multiplicative uncertainty and applying the small gain theorem to derive the sufficient conditions for robust stability and performance. The attractive feature of this robust stability and performance analysis method is that it accommodates linearized modeled or measured frequency response functions for both the physical substructure and actuator dynamics. Significant experimental research has been conducted on base isolators and dampers toward developing high fidelity numerical models. Shake table testing, where the building superstructure is tested while the isolation layer is numerically modeled, can allow for a range of isolation strategies to be examined for a single shake table experiment. Further, recent concerns in base isolation for long period, long duration earthquakes necessitate adding damping at the isolation layer, which can allow higher frequency energy to be transmitted into the superstructure and can result in damage to structural and nonstructural components that can be difficult to numerically model and accurately predict. As such, physical testing of the superstructure while numerically modeling the isolation layer may be desired. The RTHS approach has been previously proposed for base isolated buildings, however, to date it has not been conducted on a base isolated structure isolated at the ground level and where the isolation layer itself is numerically simulated. This configuration provides multiple challenges in the RTHS stability associated with higher physical substructure frequencies and a low numerical to physical mass ratio. This paper demonstrates a base isolated RTHS test and the robust stability and performance analysis necessary to ensure the stability and accuracy. The tests consist of a scaled idealized 4-story superstructure building model placed directly onto a shake table and the isolation layer simulated in MATLAB/Simulink using a dSpace real-time controller.

해상풍력 삼각지주형 하부구조물의 충격손상방지용 고무펜더의 두께결정 방법 (Method for Determining Thickness of Rubber Fenders of a Tripod Type Offshore Wind Turbine Substructure)

  • 이강수
    • Journal of Advanced Marine Engineering and Technology
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    • 제36권4호
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    • pp.490-496
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    • 2012
  • 본 연구의 목적은 바지선에 의해 발생하는 해상풍력발전기의 충격손상을 최소화 시키기 위한 것이다. 충격해석은 상용유한요소해석 프로그램인 ANSYS LS-Dyna를 통하여 분석하였다. 바지선속을 변화시켜 다양한 상태의 하중케이스를 고려하였고 충격방지고무의 비선형성을 고려한 시간이력해석을 수행하였으며 변형률 에너지, 전체 변형량, 플라스틱 변형률, 내부충격에너지, 영구손상된 변형량 등을 검토하였다. 충격속도에 변화에 따른 영구변형을 확인한 후 자연고무, 복합고무, 네오프렌 등의 고무시험 물성치로부터 구한 Mooney-Rivlin 상수를 적용하여 적절한 충격방지고무의 두께를 제안하였다. 본 연구를 통하여 구조물의 두께와 충격방지고무의 두께비에 대한 경향을 파악할 수 있으며 구조물의 설계에 적용할 수 있다.

지오셀 특성 변화에 따른 하중지지력 연구 (Experimental Study of the Changing Characteristics of Geocell with Load Carrying capacity)

  • 홍승록;최진욱;유충식;이대영;이수형;유인균
    • 한국지반신소재학회논문집
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    • 제12권3호
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    • pp.1-13
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    • 2013
  • 본 논문에서는 투수성 포장 하부구조의 지반에 지오셀 보강에 따른 거동특성을 다루었다. 지오셀을 이용한 포장구조체의 하중지지력 증가효과를 고찰하기 위하여 지오셀 결합부의 유형, 벽 두께, 직경을 변화시켜가며 총 9가지의 실험 케이스의 실내 축소모형실험을 진행하여 무보강 투수성 포장에 비해 지오셀로 보강된 포장 하부구조에서 더 큰 지지력이 발현 되는 것으로 나타났고 지오셀의 단면 형태의 관계 없이 거의 일정한 하중 지지력을 보이는 것으로 나타났다. 또한 지오셀 속채움 시 지오셀의 형상은 직경 30cm, 두께 1.8mm에서 가장 지지 효과가 크게 나타나는 것을 알 수 있었다.

하이브리드 해상풍력발전 지지구조물의 콘크리트 베이스-슬리브 연결부에 대한 실험 연구 (Experimental Study for Concrete Base to Sleeve connection of Hybrid Substructure for Offshore Wind Turbine)

  • 이정화;변남주;김성환;박재현;강영종
    • 한국산학기술학회논문지
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    • 제17권1호
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    • pp.79-87
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    • 2016
  • 본 논문에서는 하이브리드 해상풍력발전 지지구조물의 콘크리트베이스와 파일기초를 연결하는 베이스-슬리브 연결부를 제시하고 이를 실험적으로 검증하였다. 베이스-슬리브 연결부의 펀칭 전단 강도와 구조거동을 분석을 위하여, 철근비와 하중조건을 변수로 하는 3개의 연결부 실험체에 대하여 펀칭전단실험이 실시하였다. 실험 결과, 베이스-슬리브 연결부의 펀칭전단강도와 강성은 베이스의 철근비에 주로 영향을 받는 것으로 나타났다. 축력과 모멘트가 동시에 작용되는 하중 조건은 연결부의 강성에는 영향을 미치지 않으나 축력-모멘트 상호작용에 의하여 강도에 영향을 미치는 것으로 나타났다. 또한, 각 실험체의 파괴거동과 펀칭전단의 위험단면에 대해 검토되었다.

Influence of heat treatment on the microstructure and the physical and mechanical properties of dental highly translucent zirconia

  • Dimitriadis, Konstantinos;Sfikas, Athanasios Konstantinou;Kamnis, Spyros;Tsolka, Pepie;Agathopoulos, Simeon
    • The Journal of Advanced Prosthodontics
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    • 제14권2호
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    • pp.96-107
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    • 2022
  • PURPOSE. Microstructural and physico-mechanical characterization of highly translucent zirconia, prepared by milling technology (CAD-CAM) and repeated firing cycles, was the main aim of this in vitro study. MATERIALS AND METHODS. Two groups of samples of two commercial highly-translucent yttria-stabilized dental zirconia, VITA YZ-HTWhite (Group A) and Zolid HT + White (Group B), with dimensions according to the ISO 6872 "Dentistry - Ceramic materials", were prepared. The specimens of each group were divided into two subgroups. The specimens of the first subgroups (Group A1 and Group B1) were merely the sintered specimens. The specimens of the second subgroups (Group A2 and Group B2) were subjected to 4 heat treatment cycles. The microstructural features (microstructure, density, grain size, crystalline phases, and crystallite size) and four mechanical properties (flexural strength, modulus of elasticity, Vickers hardness, and fracture toughness) of the subgroups (i.e. before and after heat treatment) were compared. The statistical significance between the subgroups (A1/A2, and B1/B2) was evaluated by the t-test. In all tests, P values smaller than 5% were considered statistically significant. RESULTS. A homogenous microstructure, with no residual porosity and grains sized between 500 and 450 nm for group A and B, respectively, was observed. Crystalline yttria-stabilized tetragonal zirconia was exclusively registered in the X-ray diffractograms. The mechanical properties decreased after the heat treatment procedure, but the differences were not statistically significant. CONCLUSION. The produced zirconia ceramic materials can be safely (i.e., according to the ISO 6872) used in extensive fixed prosthetic restorations, such as substructure ceramics for three-unit prostheses involving the molar restoration and substructure ceramics for prostheses involving four or more units. Consequently, milling technology is an effective manufacturing technology for producing zirconia substructures for dental fixed all-ceramic prosthetic restorations.

Experiments and theory for progressive collapse resistance of ECC-concrete composite beam-column substructures

  • Weihong Qin;Wang Song;Peng Feng;Zhuo Xi;Tongqing Zhang
    • Structural Engineering and Mechanics
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    • 제85권1호
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    • pp.65-80
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    • 2023
  • To explore the effect of Engineered Cementitious Composite (ECC) on improving the progressive collapse resistance of reinforced concrete frames under a middle column removal scenario, six beam-column substructures were tested by quasistatic vertical loading. Among the six specimens, four were ECC-concrete composite specimens consisting of different depth of ECC at the bottom or top of the beam and concrete in the rest of the beam, while the other two are ordinary reinforced concrete specimens with different concrete strength grades for comparison. The experimental results demonstrated that ECC-concrete composite specimens can improve the bearing capacity of a beam-column substructure at the stages of compressive arch action (CAA) and catenary action in comparison with ordinary concrete specimen. Under the same depth of ECC, the progressive collapse resistance of a specimen with ECC at the beam bottom was superior to that at the beam top. With the increase of the proportion of ECC arranged at the beam bottom, the bearing capacity of a composite substructure was increased, but the increase rate slows down with the proportion. Meanwhile, the nonlinear numerical analysis software MSC Marc was used to simulate the whole loading process of the six specimens. Theoretical formulas to calculate the capacities of ECC-concrete composite specimens at the stages of flexural action, CAA and catenary action are proposed. Based on the research results, this study suggests that ECC should be laid out at the beam bottom and the layout depth should be within 25% of the total beam depth.

하이브리드 실험법을 이용한 TLD가 설치된 건물의 지진응답 제어 (Earthquake Response Control of a Building with a Tuned Liquid Damper Using Hybrid Experiment Method)

  • 이성경;이상현;민경원;박은천;우성식;정란;윤경조
    • 한국지진공학회:학술대회논문집
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    • 한국지진공학회 2006년도 학술발표회 논문집
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    • pp.527-534
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    • 2006
  • A real-time hybrid method, in which the experimental implementation and the numerical computation of a structure are simultaneously carried out in real-time and combined on-line, has been used as a dynamic testing technique of structure to investigate its dynamic behaviors. In this paper, an experimental hybrid method, which implements the earthquake response control of a building structure with a TLD by using only a TLD as an experimental part, is proposed and is experimentally verified through a shaking table test. In the proposed methodology, the whole building structure with a TLD is divided into the upper TLD and the lower structural parts as experimental and numerical substructures, respectively. At the moment, the control force acting between their interface is measured from the experimental TLD with shear-type load-cell which is mounted on shaking table. Shaking table vibrates the upper experimental TLD with the response calculated from the numerical substructure, which is subjected to the excitations of the measured interface control force at its top story and an earthquake input at its base. The experimental results show that the conventional method, in which both a TLD and a building model are physically manufactured and are tested, can be replaced by the proposed methodology with a simple experimental installation and a good accuracy for evaluating the control performance of a TLD.

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건물-지반 시스템에 관한 진동대실험 (1) : 반무한지반위의 구조물 (Shaking table test on soil-structure interaction system (1) : Superstructure with foundation on half-space soil)

  • Lee Sung-Kyung;Masato Motosaka;Min Kyung-Won
    • 한국전산구조공학회:학술대회논문집
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    • 한국전산구조공학회 2005년도 춘계 학술발표회 논문집
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    • pp.538-547
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    • 2005
  • This paper presents the shaking table testing method, only using building specimen as an experimental part taking into account the dynamic soil-structure interaction based on the substructure method. The Parmelee's soil stiffness is used as an assumed soil model in here. The proposed methodologies are summarized as: (1) Acceleration feedback method is the one that the shaking table is driven by the motion, corresponding to the acceleration at foundation of the total SSI system. This is found by observing the fed-back accelerations of superstructure and using the interaction force based on the acceleration formulation. (2) Velocity feedback method is the one that the shaking table is driven by the motion, corresponding to the velocity at foundation of the total SSI system. This is found by observing the fed-back accelerations of superstructure and using the interaction force based on the velocity formulation. The applicability of the proposed methodologies to the shaking table test is investigated and experimentally verified in this paper.

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Experimental Characterization of Cyclic Deformation in Copper Using Ultrasonic Nonlinearity

  • Kim, C.S.;Park, Ik-Keun;Jhang, Kyung-Young;Kim, Noh-Yu
    • 비파괴검사학회지
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    • 제28권3호
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    • pp.285-291
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    • 2008
  • We have experimentally investigated the cyclic deformation in copper using ultrasonic nonlinearity. The observation and characterization of dislocation substructure have been conducted using transmission electron microscope and electron backscattered diffraction technique. The ultrasonic nonlinearity (${\beta}/{\beta}_0$) was measured by the harmonic generation technique after various fatigue cycles. The microstructural effect on the nonlinearity was discussed regarding the extent of dislocation substructures evolved from low cycle fatigue. The ultrasonic nonlinearity of copper monotonically increased with the fatigue cycles due to the evolution of dislocation cell substructures.