Showing papers on "Dynamic Vibration Absorber published in 1979"

The inelastic vibration absorber subjected to earthquake ground motions

Abstract: Two storey bilinear hysteretic structures have been studied with a view to exploring the possibility of using the dynamic vibration absorber concept in earthquake-resistant design. The response of the lower storey has been optimized for the Taft 1952, S69°E accelerogram with reference to parameters such as frequency ratio, yield strength ratio and mass ratio. The influence of viscous damping has also been examined.

Tuned spring-mass vibration absorber

Abstract: A tuned spring-mass vibration absorber in which a dynamic mass is suspended from a vibrating support member, such as a helicopter fuselage, by a plurality of cantilevered leaf springs integrally connected to the dynamic mass at selected stations so that the mass CG and the spring center of force are coincident, so that the springs are shaped to constitute a substantial part of the vibration absorber effective mass, and so that the springs are pivotally connected to the support member so as to impart no moments thereto.

Vibration absorbers and bridges

Abstract: Many modern bridges exhibit very low vibration damping values, and footbridges, in particular, can often be excited into first mode vibration by pedestrians. This paper looks at the tuned vibration absorber as one solution to the increasing problem of lively bridges. Laboratory and full-scale tests in first mode vibration have been made with a single-span beam and tuned absorber attached at the mid-span position. The results are given, and the correlation between the theory presented for stationary and travelling harmonic loading is examined. /Author/TRRL/

Handbook of Vibration and Noise Control.

Abstract: : The static and dynamic properties of rubberlike materials are reviewed initially, followed by discussion of the simple and compound mounting systems. Reference is also made to the dynamic vibration absorber and to the measurement of mount transmissibility. Three sections then describe the natural frequencies, the mechanical impedances, and the transmissibility of structural members. Finally, four-pole parameter analyses are reviewed and the relative transmissibility of various mounting systems supported by a variety of non-rigid foundations is discussed. (Author)

Vibration absorber and use thereof in a helicopter

Abstract: A fixed frequency vibration absorber (10) adapted to be fixedly mounted in a fixed vibration prone system. The vibration absorber is of the pendular-type with two dynamic masses (11, 12) suspended in pendular fashion from a base member (20), and with at least one coil spring (18) acting upon the masses to establish and linearize the vibration absorber natural frequency.

Vibration absorber for use in shipbuilding - has flexible vibration absorbing body with inserted masses altering vibration frequency

Abstract: The vibration damper is used for heavy objects, in ship-building or for damping vibrations of concrete structures. On the surface of the object (1) is placed a body (10) which carries masses (12). The body is a composite vibration absorbing material. The body can be a cast resin, thermoplastics or thermosetting plastics of suitable stiffness and of suitable loss factor. The vibration absorbing masses can have plate or rod form. The latter can be made from steel or concrete or from stone and of mortar with heavy additives.

Thin film el display panel

Abstract: PURPOSE:To enhance the reliability of the products with no disconnection nor breakdown at the lead part as well as to recduce the noise occurrence by providing the vibration absorber between the back of the thin film EL display panel and the support substrate CONSTITUTION:Vibration absorber 14 composed of foaming Si rubber is provided in the gap between support substrate 12 and the back of matrix electrode structure thin film EL panel 11 incorporating the thin film EL element Thus, the vibration of panel 11 can be reduced to substrate 12 Electronic parts 15 forming the driving circuit is mounted on the back of substrate 12, and the driving pulse is applied to the thin film EL element via capton film lead 13 As foraming Si rubber features elasticity, the weight of panel 11 is born to substrate 12 And then the external vibration and impact can be absorbed by rubber 14, thus eliminating the disconnection and breakdown at the lead part as well as enhancing the reliability of the products Furthermore, the resonance of panel 11 can be prevented at the display driving time, thus reducing the noise occurrence

Reduction of offshore platform response with a liquid vibration absorber and seismic response of elevated liquid storage tanks

Abstract: The thesis is divided into two parts - I and II. -- I Reduction of Offshore Platform Response with a liquid Vibration Absorber – The LVA consists of a liquid-filled cylindrical container mounted near the deck level of the platform. During wave excitation, the liquid in the container swirls into an oscillating motion which interacts with the platform motion to produce a reduction in the platform response. The reduction in the platform response is largely due to energy dissipation through damping of the liquid, and to a smaller extent the inertia of the liquid. In this investigation, the effectiveness of the LVA in reducing the dynamic response of the offshore platform model is studied. The finite element programme for dynamic analysis of two-dimensional fixed offshore platforms, developed by Duvall (1), has been extended by Glacel (2) to include damping effects and a tuned mass damper. This study describes further modifications of the work with an additional option of replacing the actual spring mass model by an LVA. The relatively rigid container wall is discretized by finite beam elements. The work of Housner (3) is employed account for the liquid sloshing loads on the container wall, while the liquid damping is based on a semi-empirical formulation by Stephens et al (4). The structural response of the model is determined for a digitized wave height spectrum, with and without the LVA in operation. The platform is analysed to determine the LVA effectiveness, and the variation of the system response with the LVA parameters. The various parameters considered are, cylinder radius, liquid height, liquid mass, frequency, and damping. Methods of frequency tuning, and damping device mechanisms are discussed. – II Seismic Response of Elevated Liquid Storage Tanks – The structure under consideration consists of a liquid storage tank mounted on an axisymmetric pedestal. The tank is a thin elastic cylinder with an axisymmetric dome-top and a conical base which is relatively rigid. A finite element model is presented for the seismic analysis of the structure. The shell mass and stiffness matrices are generated by using the computer code SAMMSOR-II (56). The procedure of Shaaban and Nash (45) is used to generate the added liquid mass matrix which accounts for the hydrodynamic effect on the tank wall. A digitized acceleration of an earthquake is provided as the ground excitation input, and the displacement response of the whole system determined by mode superposition.