Theory, Design, and Application of Dynamic Absorbing Beam

• Main Authors: Yen-Hui Huang, 黃燕輝
• Other Authors: Yung-Hsiang Chen
• Format: Others
• Language: zh-TW
• Published: 2000
• Online Access: http://ndltd.ncl.edu.tw/handle/13134226608078490128

博士 === 國立臺灣大學 === 土木工程學研究所 === 88 === The dynamic absorbing beam is composed of a metal beam (called tuned beam) and a layer of the viscoelastic material (such as the high-damping rubber), which can effectively disperse the energy of vibration and reduce the vibration of the main structure. The Timoshenko beam theory is applied to the beam structure. The study of the dynamic absorbing beam includes: (1) Timoshenko beam (functions as a dynamic absorbing beam) on viscoelastic foundation, (2) The viscoelastic layered dynamic absorbing beam, which composed of a main beam and a tuned beam with a viscoelastic layer in between. (3) The viscoelastic layered dynamic absorbing beam on viscoelastic foundation. One or more concentrated masses can be attached to the tuned beam in order to increase the performance of the damper. The spring, link, or support can be set between the tuned beam and the structure, if necessary in application. The study of the dynamic absorbing beam adopts distributed- parameter and continuous coordinate system to describe the dynamic behavior of the beam structure, which is different from the discrete coordinate of the finite element method. Therefore, the dynamic characteristics of the beam structure can be completely described. The dynamic shape functions, dynamic stiffness matrix, and frequency equation are established, and the natural frequencies, mode shapes, and dynamic magnification factor are calculated. The optimal design of the viscoelastic layered dynamic absorbing beam can be performed by the simplified model of two-degree-of-freedom system. With the same shape functions of the main beam and tuned beam, the formula of the optimal parameters, such as optimal tuned frequency, optimal layer spring coefficient, optimal mass ratio, and optimal damping ratio, are derived. For the arbitrary boundary conditions of beams, the optimal parameters can be determined numerically by the theory of the layered beam. By performing the structural analysis and optimal design properly, this so-called dynamic absorbing beam can reduce the vibration of the main beam very efficiently. The modal test shows excellent in agreement to the analytical results. It proves the potential of the dynamic-absorbing beam in engineering applications.