• Title/Summary/Keyword: modeling of structures

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Dynamic Modeling and Control of Flexible Space Structures

  • Chae, Jang-Soo;Park, Tae-Won
    • Journal of Mechanical Science and Technology
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    • v.17 no.12
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    • pp.1912-1921
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    • 2003
  • This paper presents a global mode modeling of space structures and a control scheme from the practical point of view. Since the size of the satellite has become bigger and the accuracy of attitude control more strictly required, it is necessary to consider the structural flexibility of the spacecraft. Although it is well known that the finite element (FE) model can accurately model the flexibility of the satellite, there are associated problems : FE model has the system matrix with high order and does not provide any physical insights, and is available only after all structural features have been decided. Therefore, it is almost impossible to design attitude and orbit controller using FE model unless the structural features are in place. In order to deal with this problem, the control design scheme with the global mode (GM) model is suggested. This paper describes a flexible structure modeling and three-axis controller design process and demonstrates the adequate performance of the design with respect to the maneuverability by applying it to a large flexible spacecraft model.

A Study on the Core Equivalent Stiffness Modeling Technique for FSI Analysis of High-Rise Buildings Under Wind Load (풍하중을 받는 초고층건물의 FSI 해석을 위한 코어 삽입 등가 강성 모델링 기법에 관한 연구)

  • Oh, Kang-Hwan;Jeon, Doo-jin;Han, Sang-Eul
    • Journal of Korean Association for Spatial Structures
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    • v.17 no.3
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    • pp.65-73
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    • 2017
  • Recently, the trend is emerging a variety of irregular tall buildings. It is important to design the building for lateral load according to this trend. Fluid Structure Interaction(FSI) simulation can be performed to understand the vibrations of the structure against dynamic wind loads. In order to make the physical characteristics of the actual structure and the analytical model the same, we studied core inserting equivalent stiffness modeling method. As a result of this analysis, the stiffness of the structure can be set similar to that of the two axes of the structure, and turbulence can be reproduced through the acceleration tendency.

3D Structure Prediction of Thromboxane A2 Receptor by Homology Modeling

  • Nagarajan, Santhosh Kumar;Madhavan, Thirumurthy
    • Journal of Integrative Natural Science
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    • v.8 no.1
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    • pp.75-79
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    • 2015
  • Thromboxane A2 receptors (TXA2-R) are the G protein coupled receptors localized on cell membranes and intracellular structures and play pathophysiological role in various thrombosis/hemostasis, modulation of the immune response, acute myocardial infarction, inflammatory lung disease, hypertension and nephrotic disease. TXA2 receptor antagonists have been evaluated as potential therapeutic agents for asthma, thrombosis and hypertension. The role of TXA2 in wide spectrum of diseases makes this as an important drug target. Hence in the present study, homology modeling of TXA2 receptor was performed using the crystal structure of squid rhodopsin and night blindness causing G90D rhodopsin. 20 models were generated using single and multiple templates based approaches and the best model was selected based on the validation result. We found that multiple template based approach have given better accuracy. The generated structures can be used in future for further binding site and docking analysis.

Finite Element Modeling and Experimental Verification of the Structures with Bolted Joints (볼트결합부가 있는 구조물의 유한요소 모델링 및 실험적 검증)

  • Kim, Jin-Gon;Park, Seong-Su;Choe, Seok-Hwan
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.20 no.6
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    • pp.1854-1861
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    • 1996
  • A reliable and practical finite element modeling technique to estimate the behavior of complex structures with bolted joints is important for engineeres in the industry. Accordingly, we have examined several simplified modeling techinques which do not require the use of special elements such as a gap eloement. The dynamic and static erxperiments have confirmed that the technique to model the bolted joints with eight-noded three dimensional elemnts which fill the bolt space gdives most satisfactory results.

Electret-based microgenerators under sinusoidal excitations: an analytical modeling

  • Nguyen, Cuong C.;Ranasinghe, Damith C.;Al-Sarawi, Said F.
    • Smart Structures and Systems
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    • v.21 no.3
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    • pp.335-347
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    • 2018
  • The fast-growing number of mobile and wearable applications has driven several innovations in small-scale electret-based energy harvesting due to the compatibility with standard microfabrication processes and the ability to generate electrical energy from ambient vibrations. However, the current modeling methods used to design these small scale transducers or microgenerators are applicable only for constant-speed rotations and small sinusoidal translations, while in practice, large amplitude sinusoidal vibrations can happen. Therefore, in this paper, we formulate an analytical model for electret-based microgenerators under general sinusoidal excitations. The proposed model is validated using finite element modeling combined with numerical simulation approaches presented in the literature. The new model demonstrates a good agreement in estimating both the output voltage and power of the microgenerator. This new model provides useful insights into the microgenerator operating mechanism and design trade-offs, and therefore, can be utilized in the design and performance optimization of these small structures.

Structural analysis of a thick composite rotor hub system by using equivalent properties (등가 물성을 이용한 두꺼운 복합재 로터 허브 시스템의 구조 해석)

  • ;Yanti Rachmadini
    • Composites Research
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    • v.16 no.5
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    • pp.7-14
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    • 2003
  • Modeling of thick composite structures for finite element analysis is relatively complicated. 2-D plane elements may cause inaccurate result since the plane stress condition cannot be applicable in these structures. Therefore a 3-D modeling should be used. However, the difficulty to model all the layers with different material properties and ply orientation arise in this case. In this paper, an equivalent modeling is proposed and numerically tested for analysis of thick composite structures. By grouping layers with same material and ply orientation, number of elements through the thickness is remarkably reduced and still the result is close enough to the one from a detail finite element model. MSC/NASTRAN and PATRAN are used for the analysis. The proposed modeling technique has been applied for analysis of composite rotor hub system designed by Korea Aerospace Research Institute(KARI). Using the proposed equivalent modeling technique, we could conduct stress analysis for the hub system and check the safety factor of each part.

Nonlinear Modeling and Dynamic Analysis of Flexible Structures Undergoing Overall Motions Employing Mode Approximation Method

  • Kim, Jung-Young;Hyun, Sang-Hak;Yoo, Hong-Hee
    • Journal of Mechanical Science and Technology
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    • v.16 no.7
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    • pp.896-901
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    • 2002
  • This paper presents a nonlinear modeling method for dynamic analysis of flexible structures undergoing overall motions that employs the mode approximation method. This method, different from the naive nonlinear method that approximates only Cartesian deformation variables, approximates not only deformation variables but also strain variables. Geometric constraint relations between the strain variables and the deformation variables are introduced and incorporated into the formulation. Two numerical examples are solved and the reliability and the accuracy of the proposed formulation are examined through the numerical study.

Reinforcement detailing of a corbel via an integrated strut-and-tie modeling approach

  • Ozkal, Fatih Mehmet;Uysal, Habib
    • Computers and Concrete
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    • v.19 no.5
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    • pp.589-597
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    • 2017
  • Strut-and-tie modeling method, which evolved on truss-model approach, has generally been preferred for the design of complex reinforced concrete structures and structural elements that have critical shear behavior. Some structural members having disturbed regions require exceptional detailing for all support and loading conditions, such as the beam-column connections, deep beams, short columns or corbels. Considering the general expectation of exhibiting brittle behavior, corbels are somewhat dissimilar to other shear critical structures. In this study, reinforcement layout of a corbel model was determined by the participation of structural optimization and strut-and-tie modeling methods, and an experimental comparison was performed against a conventionally designed model.

Analysis and performance of offshore platforms in hurricanes

  • Kareem, Ahsan;Kijewski, Tracy;Smith, Charles E.
    • Wind and Structures
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    • v.2 no.1
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    • pp.1-23
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    • 1999
  • Wind effects are critical considerations in the design of topside structures, overall structural systems, or both, depending on the water depth and type of offshore platform. The reliable design of these facilities for oil fields in regions of hostile environment can only be assured through better understanding of the environmental load effects and enhanced response prediction capabilities. This paper summarizes the analysis and performance of offshore platforms under extreme wind loads, including the quantification of wind load effects with focus on wind field characteristics, steady and unsteady loads, gust loading factors, application of wind tunnel tests, and the provisions of the American Petroleum Institute Recommended Practice 2A - Working Stress Design (API RP 2A-WSD) for the construction of offshore structures under the action of wind. A survey of the performance of platforms and satellite structures is provided, and failure mechanisms concerning different damage scenarios during Hurricane Andrew are examined. Guidelines and provisions for improving analysis and design of structures are addressed.

Numerical modeling and analysis of RC frames subjected to multiple earthquakes

  • Abdelnaby, Adel E.;Elnashai, Amr S.
    • Earthquakes and Structures
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    • v.9 no.5
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    • pp.957-981
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    • 2015
  • Earthquakes occur as a cluster in many regions around the world where complex fault systems exist. The repeated shaking usually induces accumulative damage to affected structures. Damage accumulation in structural systems increases their level of degradation in stiffness and also reduces their strength. Many existing analytical tools of modeling RC structures lack the salient damage features that account for stiffness and strength degradation resulting from repeated earthquake loading. Therefore, these tools are inadequate to study the response of structures in regions prone to multiple earthquakes hazard. The objective of this paper is twofold: (a) develop a tool that contains appropriate damage features for the numerical analysis of RC structures subjected to more than one earthquake; and (b) conduct a parametric study that investigates the effects of multiple earthquakes on the response of RC moment resisting frame systems. For this purpose, macroscopic constitutive models of concrete and steel materials that contain the aforementioned damage features and are capable of accurately capturing materials degrading behavior, are selected and implemented into fiber-based finite element software. Furthermore, finite element models that utilize the implemented concrete and steel stress-strain hysteresis are developed. The models are then subjected to selected sets of earthquake sequences. The results presented in this study clearly indicate that the response of degrading structural systems is appreciably influenced by strong-motion sequences in a manner that cannot be predicted from simple analysis. It also confirms that the effects of multiple earthquakes on earthquake safety can be very considerable.