Vibration Reduction of a Floating Roof by Dynamic Vibration Absorbers

This paper investigates the use of dynamic vibration absorbers as a means to reduce the vibration of a floating roof due to sloshing caused by long-period earthquakes. It is shown that the damping ratio of the primary system caused by the dynamic vibration absorbers increases with rising filling level, hence increasing the probability of liquid overspilling, although the ratio of the vibration absorbers’ mass to the liquid mass decreases as the filling level rises. We also study dynamic vibration absorbers that can be more easily tuned to the filling-level dependent sloshing frequency. A feature of these vibration absorbers is that they use time-integral feedback of the primary structure’s displacement near the tuning frequency unlike ordinary vibration absorbers. Computer simulation is carried out using a sinusoidal wave function and an actual earthquake ground motion record as the excitation applied to the tank.