Twelve Lectures on Structural Dynamics pp 247-274
- First Online:
This chapter analyzes various ways of reducing vibration passively. Two main categories are examined: the first category consists of reducing the amplification of the resonance peak by dissipating the vibration energy; the second, known as isolation, consists of preventing the propagation of the disturbances to the sensitive part of the structure. The first part of this chapter is devoted to the Dynamic Vibration Absorber which may be used either for narrow band disturbances or for wide band disturbances (with a different tuning); its efficacy is illustrated on a n-storey building excited seismically. The second part of this chapter is devoted to isolation; first, the weaknesses of the single axis linear isolator are examined and the benefit of the relaxation isolator are pointed out. Next, the equations governing a six-axis isolator are formulated. The chapter ends with a few interesting specific problems: the isolation by kinematic coupling (used in helicopters), the centrifugal pendulum vibration isolator (used in car transmissions) and a quarter-car model of a car suspension. A set of problems is proposed at the end of the chapter.