• Title, Summary, Keyword: 고유 진동

Search Result 2,003, Processing Time 0.04 seconds

Natural Frequency Characteristics of a Cylindrical Tank Filled with Bounded Compressible Fluid (압축성 유체로 충진된 원통형 탱크의 고유진동수의 특성)

  • 정경훈;김강수;박근배
    • Computational Structural Engineering
    • /
    • v.10 no.4
    • /
    • pp.291-302
    • /
    • 1997
  • This paper presents an analytical method for evaluating the free vibration of a circular cylindrical tank filled with bounded compressible fluid. The analytical method was developed by means of the finite Fourier series expansion method. The compressible fluid motion was determined by means of the linear velocity potential theory. To clarify the validity of the analytical method, the natural frequencies of a circular cylindrical tank with the clamped-clamped boundary condition, and filled with water, were obtained by the analytical method and the finite element method using a comercial ANSYS 5.2 software. Excellent agreement on the natural frequencies of the liquid-filled tank structure was found. The compressiblity and the fluid density effects on the normalized coupled natural frequencies were investigated. The density of fluid affects on all coupled natural frequencies of the tank, whereas the compressibility of fluid affects mainly on the natural frequencies of lower circumferential modes.

  • PDF

The Influence of the Loading Sizes on Natural Frequency of the Advanced Composite Material Structures (복합신소재구조물의 고유진동수에 대한 하중크기의 영향)

  • Han, Bong Koo
    • Journal of the Korea institute for structural maintenance and inspection
    • /
    • v.17 no.3
    • /
    • pp.20-27
    • /
    • 2013
  • Simple Iteration Method for calculating the natural frequency is presented in this paper. This method is simple but exact method of calculating natural frequencies corresponding to the modes of vibration of beams and tower structures with irregular cross sections and arbitrary boundary conditions. This method consists of determining the deflected mode shape of the member due to the inertia force under resonance condition. Finite difference method is used for this purpose. The influence of the $D_{22}$ stiffness on the natural frequency is rigorously investigated. In this paper, the influence of the loading sizes, different cross section on the natural frequency of vibration of some structural elements is presented. This method extends to two dimensional problems including advanced composite material structures.

Topology Optimization of a Vibrating System of Rigid and Flexible Bodies for Maximizing Repeated Eigenfrequencies (중복 고유 진동수를 갖는 진동하는 강체-유연체 계의 위상최적설계)

  • Ahn, Byungseong;Kim, Suh In;Kim, Yoon Young
    • Transactions of the Korean Society of Mechanical Engineers A
    • /
    • v.40 no.4
    • /
    • pp.363-372
    • /
    • 2016
  • When a system consisting of rigid and flexible bodies is optimized to improve its dynamic characteristics, its eigenfrequencies are typically maximized. While topology optimization formulations dealing with simultaneous design of a system of rigid and flexible bodies are available, studies on eigenvalue maximization of the system are rare. In particular, no work has solved for the case when the target frequency becomes one of the repeated eigenfrequencies. The problem involving repeated eigenfrequencies is solved in this study, and a topology optimization formulation and sensitivity analysis are presented. Further, several numerical case studies are considered to demonstrate the validity of the proposed formulation.

Free Vibrations of Elastica Shaped Arches with Linear Taper (선형 변단면 정확탄성곡선형 아치의 자유진동)

  • Lee, Byoung Koo;Lee, Tae Eun;Kim, Gwon Sik
    • Journal of The Korean Society of Civil Engineers
    • /
    • v.29 no.6A
    • /
    • pp.617-624
    • /
    • 2009
  • This study deals with the free vibrations of the elastica shaped arch with linear taper. The shape of elastica is obtained from the Bernoulli-Euler beam theory. Differential equations governing free vibrations of such arch are derived and numerically solved to determine natural frequencies, in which three kinds of taper type and two kinds of end constraint, respectively, are considered. For validating the theories presented herein, the frequency parameters obtained in this study are compared to those of SAP 2000. As results of the numerical analyses, effects of end constraint, taper type, slenderness ratio and section ratio on the lowest four non-dimensional frequency parameters are extensively investigated.

  • PDF

Modal Parameter Extraction of Seohae Cable-stayed Bridge : II. Natural Frequency and Damping Ratio (서해대교 사장교의 동특성 추출 : II. 고유진동수와 감쇠비)

  • Kim, Byeong Hwa;Park, Jong-Chil
    • Journal of The Korean Society of Civil Engineers
    • /
    • v.28 no.5A
    • /
    • pp.641-647
    • /
    • 2008
  • This paper introduces a new technique that can extract natural frequencies and damping ratios from output-only vibration data. Firstly, the free vibration data is obtained from the cross correlations of the output-only response data using a singular value decomposition process. Secondly, the well-known system identification algorithm is applied to extract the natural frequencies and damping ratios from the extracted free vibration data. Comparing to ERADC technique, the accuracy of the proposed modal parameter identification algorithm has been numerically examined. Furthermore, the practicability of the proposed algorithm has been examined through the output-only acceleration data collected from the Seohae cable-stayed bridge. Using the proposed technique, total 24 modes have been identified for the deck plate motions of the bridge.

  • PDF

Flexural Stiffness and Characteristics of Vibration in CFT Truss Girder (CFT 트러스 거더의 휨강성 및 진동특성)

  • Chung, Chul-Hun;Song, Na-Young;Kim, In-Gyu;Jin, Byeong-Moo
    • Journal of The Korean Society of Civil Engineers
    • /
    • v.29 no.1A
    • /
    • pp.19-30
    • /
    • 2009
  • The primary objective of the present study was to attempt to quantify the effect of the existing codes for CFT composite section on initial section flexural stiffness, based on the measured vibration frequency of CFT truss girders. The formulae for the initial flexural stiffness of the composite sections in the different codes are compared with the free vibration test results. The results of the free vibration test on the CFT truss girders are in good agreement with the analysis results when used in ACI formulae. The free vibration analysis of CFT truss girders for different f/L ratios was conducted to determine how the natural frequency of the CFT truss girder is affected by different f/L ratios. The presence of the f/L ratios in CFT truss girders alters its frequencies of vibration because of the global stiffness of the CFT girders. The frequency in horizontal modes decreases as the f/L ratio increases. However, the frequency in vertical modes increases as the f/L ratio increases.

  • PDF

Vibration Characteristics of a Three-Story Reinforced Concrete Building Before and After Damage (3층 철근콘크리트조 건물의 손상전후의 진동특성)

  • Yoon, Sung-Won;Park, Yong;Ji, Jung-Hwan;Lim, Jae-Hwi;Jang, Dong-Wo
    • Journal of the Korean Association for Spatial Structures
    • /
    • v.9 no.3
    • /
    • pp.59-66
    • /
    • 2009
  • Dynamic characteristics such as frequency and damping ratio in the ambient state of building has been progressed in domestic and foreign. However, there has not been any deep research of dynamic characteristics of full-scale structure using vibration measurement of the building damaged up to failure. Dynamic characteristics of three-story reinforced concrete building was evaluated before and after it was damaged by using a actuator. Dynamic characteristics is reviewed and compared with previous study. Ambient vibration and human excitation test were applied. After 120mm horizontal displacement by actuator, frequency of long and short direction is reduced to 34.3%, 33.7% and damping ratio is reduced to 36.5%, 19.5% respectively.

  • PDF

Vibrational Chacacteristics of Initially Stressed Laminated Plates (초기응력을 받는 적층판의 진동특성에 관한 연구)

  • Park, Sung-Jin;Baek, Joo-Eun
    • Proceedings of the Korean Society of Disaster Information Conference
    • /
    • /
    • pp.188-189
    • /
    • 2016
  • 본 논문은 초기하중을 하중을 받는 역대칭 angle-ply 와 cross-ply 적층판의 좌굴 및 진동특성을 무재하시의 고유진동수를 이용하여 산정하는 간편법을 제시하였다. 마주보는 두변이 단순 지지된 역대칭 적층판의 운동방정식은 전단변형과 회전강성효과를 고려한 YSN 이론으로 유도하였으며 이를 선점법을 이용하여 해석하였다. 초기응력을 받는 적층판의 무차원화 고유진동수, 임계좌굴계수 및 동적 주 불안정영역 문제들을 무재하시의 무차원화 고유진동수로서 각각의 특성을 정립시켰다. 본 연구에서 제안한 진동특성에 관한 간편산정식의 정당성과 사용성을 입증하기 위하여 수치예들로서 검토하였다.

  • PDF

Computational Modelling Method by Using the Natural Frequencies of Five-Story Stone Pagoda in Chongnimsa Site (고유진동수를 이용한 정림사지 5층 석탑의 구조모델)

  • Lee, Sung-Min;Lee, Ki-Hak;Park, Sun-Woo;Suh, Man-Chul;Lee, Chan-Hee
    • Journal of the Korean Association for Spatial Structures
    • /
    • v.8 no.5
    • /
    • pp.67-74
    • /
    • 2008
  • Multi-layered stone masonry monuments, such as stone pagoda can be modeled as a multi-degrees of freedom system. The dynamic behavior of these structures are mainly influenced by contour condition of contacting surface of stones. In this case the mass of the system can be easily estimated, mean while the estimation of stiffness at junction is not simple. In this paper a method for estimating the spring constant at the contacting surface of stone in proposed. This paper describes a method of computational modelling technique for structural analysis of stone pagodas using measurement of natural frequency and eigenvalue analysis. For this purpose Five story stone pagoda in Cchongnimsa site was selected as a model.

  • PDF

Vibration Characteristics of the Point-symmetric Mode in a Spherical Piezoelectric Transducer (구형 압전 변환기의 점대칭 방사모드 진동 특성)

  • 전한용;김진오
    • The Journal of the Acoustical Society of Korea
    • /
    • v.21 no.8
    • /
    • pp.757-765
    • /
    • 2002
  • The object of this paper is to examine the vibration characteristics of the point-symmetric radial mode in a spherical piezoelectric transducer. The differential equations of piezoelectric radial motion are derived in terms of the radial displacement and electric potential, which are functions of the radial coordinate and time. Applying mechanical and electrical boundary conditions yields the characteristic equation of radial vibration. Numerical results of the natural frequencies are compared with the experimental measurements. The paper discusses the difference between piezoelectric and elastic resonances and the dependence of the natural frequencies on the radius and thickness of the piezoelectric spheres. As a result it is concluded for the first radial mode that the natural frequency is reduced due to the piezoelectric phenomenon and that the frequency exponentially decreases as the sphere radius increases.