• Title, Summary, Keyword: Number of Excitations

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Dynamic Analysis of Viscoelastic Composite Thin-Walled Blade Structures (점탄성-복합재 박판 블레이드 구조물의 진동 해석)

  • Shin, Jae-Hyun;Na, Sung-Soo;Park, Chul-Hue
    • Proceedings of the KSME Conference
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    • pp.1684-1689
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    • 2003
  • This paper concerns the analytical modeling and dynamic analysis of advanced cantilevered blade structure implemented by a dual approach based on structural tailoring and viscoelastic materials technology. Whereas structural tailoring uses the directionality properties of advanced composite materials, the passive materials technology exploits the damping capabilities of viscoelastic material(VEM) embedded into the host structure. The structure is modeled as a composite thin-walled beam incorporating a number of nonclassical features such as transverse shear, secondary warping, anisotropy of constituent materials, and rotary inertias. The case of VEM spreaded over the entire span of the structure is considered. The displayed numerical results provide a comprehensive picture of the synergisitic implications of the application of both techniques, namely, the tailoring and damping technology on vibration response of thin-walled beam structure exposed to external time-dependent excitations.

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A simplified normalized cumulative hysteretic energy spectrum

  • Sun, Guohua;Gu, Qiang;Fang, Youzhen
    • Earthquakes and Structures
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    • v.12 no.2
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    • pp.177-189
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    • 2017
  • For energy-based seismic design, a simplified normalized cumulative hysteretic energy spectrum proposed for obtaining hysteretic energy as energy demand is the main objective in this paper. The dimensionless parameter, ${\beta}_{Eh}$, is presented to express hysteretic energy indirectly. The ${\beta}_{Eh}$ spectrum is constructed directly through subtracting the hysteretic energy of single degree-of-freedom (SDOF) system energy equation. The simplified ${\beta}_{Eh}$ spectral formulation as well as pseudo-acceleration spectrum of modern seismic provisions is developed based on the regression analysis of the large number of seismic responses of SDOF system subjected to earthquake excitations, which considers the influence of earthquake event, soil type, damping ratio, and ductility factor. The relationship between PGV and PGA is established according to the statistical analysis relied on a total of 422 ground motion records. The combination of ${\beta}_{Eh}$ spectrum and PGV/PGA equation allows determining the cumulative hysteretic energy as a main aseismic design indicator.

Detection of Intensity Changes by a Diffusion Neural Network (확산뉴런망을 이용한 밝기 변화 추출)

  • Kwon, Yool;Nam, Ki-Gon;Yoon, Tae-Hoon;Kim, Jae-Chang
    • Journal of the Korean Institute of Telematics and Electronics B
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    • v.29B no.11
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    • pp.85-92
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    • 1992
  • In this paper we propose a diffusion neural network model. In this model, each excitatory and inhibitory neuron has the capability of diffusing external excitations. We show that this model can be used for the detection of intensity changes of an input image. The relations between the diffusion coefficient, the iteration number of diffusion, and the detected spatial frequency are analyzed. The calculation time is reduced than that of a LOG(a Laplacian of a Gaussian) method.

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Dynamic Response Analysis of Composite H-Type Cross-Section Beams to Random Loads (랜덤하중이 가해진 복합재료 H-형 보의 동적 응답 해석)

  • Kim, Sung-Kyun;Song, Pong-Gun;Song, Oh-Seop
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.130-135
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    • 2011
  • A study of the bending-extension-transverse shear coupled random response of the composite beams with thin-walled open sections subjected to various types of concentrated and distributed random excitations is dealt with in this paper. First of all, equations of motion of thin-walled composite H-type cross-section beams incorporating a number of nonclassical effects of transverse shear and primary and secondary warping, and anisotropy of constituent materials are derived. On the basis of derived equations of motion, analytical expressions for the displacement response of the composite beams are derived by using normal mode method combined with frequency response function method.

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Seismic analysis of 3-D two adjacent buildings connected by viscous dampers with effect of underneath different soil kinds

  • Farghaly, Ahmed Abdelraheem
    • Smart Structures and Systems
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    • v.15 no.5
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    • pp.1293-1309
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    • 2015
  • 3D two adjacent buildings with different heights founded in different kinds of soil connected with viscous dampers groups, with especial arrangement in plane, were investigated. Soil structure interaction for three different kinds of soil (stiff, medium and soft) were modeled as 3D Winkler model to give the realistic behavior of adjacent buildings connected with viscous dampers under various earthquake excitations taking in the account the effect of different kinds of soil beneath the buildings, using SAP2000n to model the whole system. A range of soil properties and soil damping characteristics are chosen which gives broad picture of connected structures system behavior resulted from the influence soil-structure interaction. Its conclusion that the response of connected structures system founded on soft soil are more critical than those founded on stiff soil. The behavior of connected structures is different from those with fixed base bigger by nearly 20%, and the efficiency of viscous dampers connecting the two adjacent buildings is reduced by nearly 25% less than those founded on stiff soil.

Convergence studies on static and dynamic analysis of beams by using the U-transformation method and finite difference method

  • Yang, Y.;Cai, M.;Liu, J.K.
    • Structural Engineering and Mechanics
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    • v.31 no.4
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    • pp.383-392
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    • 2009
  • The static and dynamic analyses of simply supported beams are studied by using the U-transformation method and the finite difference method. When the beam is divided into the mesh of equal elements, the mesh may be treated as a periodic structure. After an equivalent cyclic periodic system is established, the difference governing equation for such an equivalent system can be uncoupled by applying the U-transformation. Therefore, a set of single-degree-of-freedom equations is formed. These equations can be used to obtain exact analytical solutions of the deflections, bending moments, buckling loads, natural frequencies and dynamic responses of the beam subjected to particular loads or excitations. When the number of elements approaches to infinity, the exact error expression and the exact convergence rates of the difference solutions are obtained. These exact results cannot be easily derived if other methods are used instead.

Identification of Diametrical Node Number of Travelling Wave Modes is Rotating Disk-Use of Directional Frequency Response Function (회전원판의 진행파 모드 절직경 수 규명-방향성 주파수응답함수의 이용)

  • Kim, Myeong-Eop;Lee, Chong-Won
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.20 no.3
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    • pp.960-967
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    • 1996
  • Directional frequency response functions(dFRFs) are introduced for isotropic rotating disks, treating pairs of excitations and measurements as the complex input and output, respectively. It is shown that the dFRFs can be effectively used for separation of the forward and backward travelling wave modes and identification of the diametrical node numbers associated with modes of interst. Numerical simuations and experimental works are performed to demonstrate the analytical development and its validity.

Damage Assessment and A seismic Capacity Evaluation of Existing Structures (기설구조물의 손상도추정 및 내진능력평가 방법에 관한 연구)

  • 윤정방;송종걸;김유진
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • pp.414-421
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    • 1998
  • The content of this paper consists of two related subjects. One is the assessment of damages in the existing structure and the other is the evaluation of seismic capacity of the structure with damage. A method is presented for damage assessment of existing structures using the modal data measured at limited points by the inverse medal perturbation technique. For efficient damage assessment, the number of the unknown probable damaged members is reduced for each damage identification by grouping the members in the large structure. The aseismic capacity is evaluated for the structure using the results of damage assessment. An example analysis is carried out for a building structure subjected to different earthquake excitations.

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Damage Detection Method for Bridge Structures Using Hilbert-Huang Transform Technique (Hilbert-Huang Transform을 이용한 교량구조물의 손상추정기법)

  • 윤정방;장신애;심성한;이종재
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • pp.453-458
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    • 2002
  • A recently developed Hilbert-Huang transform (HHT) technique is applied to the detection of the damage locations of bridge structures. The HHT may be used to identify the locations of damages which exhibit nonlinear and non-stationary behavior, since the instantaneous frequency characteristics of the measured signal can be analyzed by the HHT. Numerical simulations were conducted on two bridge systems with damages using controlled excitations with sweeping frequency. Nonlinear plastic model using a gap element is employed to model the behavior of the cracked elements in the numerical simulations. The results indicate that the HHT method can reasonably identify the damage locations based on a limited number of acceleration sensors. Experimental study has been 실so carried out on a steel frame to confirm the applicability of the HHT to detect a structural connection with loosened bolts.

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Dynamic Response Analysis of Composite H-type Cross-section Beams (복합재료 H-형 단면 보의 동적응답 해석)

  • Kim, Sung-Kyun;Song, Oh-Seop
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.20 no.6
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    • pp.583-592
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    • 2010
  • Equations of motion of thin-walled composite H-type cross-section beams exposed to concentrated harmonic and non-harmonic time-dependent external excitations, incorporating a number of nonclassical effects of transverse shear, primary and secondary warping, and anisotropy of constituent materials are derived. The forced vibration response characteristics of a composite H-type cross-section beam exhibiting the circumferentially asymmetric stiffness(CAS) configuration are exploited in connection with the structural bending-torsion coupling resulting from directional properties of fiber reinforced composite materials.