In this paper the application of a passive control system with fluid (the Tuned Liquid Damper) to buildings exposed to earthquakes will be studied for two types of tanks: a classic cylindrical tank and a tank in the shape of a frustum of a cone, called conical in the following. This second type represents the new proposal of this study. The advantages of the conical tank are linked to its greater adaptability to a control of semiactive type, since with the variation of the height of the liquid one obtains a variation of the natural frequency of the tank, and therefore one can enforce or avoid the condition of "tuning". On the other hand the natural frequency of a cylindrical tank is not influenced substantially by the height of the liquid.

There have been made tests on shaking tables for structures with one degree of freedom, and the results of the control strategies have been satisfactory for both types of tanks for all the signals used in the experiments: sinusoidal signals, white noise and recorded earthquake accelerations. Experimenting with some earthquake signals it has been noticed that, when the signal has a strong initial impulsive character, the fluid needs some seconds in order to work well, and initially the benefit of the control is modest. The experimental tests are interpreted using simplified linearized models. for the interaction container-liquid. Such models, even if they are used here at the limit of their applicability, have proven however to be very useful for the identification of the first mode of vibration of the tank and have given an satisfactory interpretation of the result of the experiments.

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