Therefore, even in its apparent simplicity, this may be considered an open problem, to be carefully deepened both under the experimental and numerical points of view.

On the other side, the possibility of preventing collapses of structures by means of additional masses suitably tuned to the basic characteristics of the structure itself is a widely studied problem, and devices based on sloshing liquids have now recognized desirable damping properties [9,10,11,12,13].

In this paper the two features are coupled and the possibility of controlling the dynamic rocking response of standard models of rigid blocks by simple TLDs devices is investigated from an experimental point of view.

For developing experimental tests, one refers to a unidirectional shaking table facility available at the Laboratory of "Scienza delle Costruzioni" of the University of Naples "Federico II".

In order to evaluate the dissipation of energy due to the sloshing action of liquid in containers, some tanks filled with water at different levels are mounted on the upper surface of some rigid blocks, placed on the shaking table, with the purpose of dissipating the incoming energy.

Generally speaking, one can observe that comparison between the different liquid depth levels reveal the efficiency and advantage of the liquid damper system in damping the vibrations of the structural model.

In all the cases that have been tested the benefit has been found to be potentially very significant (attenuation ratio larger and also much larger than five in some cases) but some cases have been encountered where the device increases the risk (attenuation ratio smaller than one).

The conclusion is that a theoretical settlement cannot be ignored and the damping device has to be carefully designed with regard to shape and entity of the sloshing liquid mass, taking into account both the excitation's character and the object's inertial properties.

1

M. Aslam, W.G. Godden, D.T. Scalise, "Earthquake rocking response of rigid bodies", J. Engrg. Mech. Div. ASCE 106(2), pp. 377-392, 1980.

2

I. Corbi, R. Orefice, "Study of rocking rigid blocks using shaking table experiments", Proc. 4th Int. Conf. Engineering Computational Technology, in press, Portogallo, 2004. doi:10.4203/ccp.79.270

3

S.J. Hogan, "The many steady state responses of a rigid block under harmonic forcing", Int. J. Earthquake Eng. & Struct. Dyn. 19, pp. 1057-1071, 1990. doi:10.1002/eqe.4290190709

4

J. Milne, "Experiments in observational seismology", Trans. Seism. Soc. Japan 8, 12-64, 1881.

5

J. Perry, "Note on the rocking of a column", Trans. Seism. Soc. Japan 3, pp. 103-106, 1881.

6

W.K. Tso, C.M. Wong, "Steady state rocking response of rigid blocks. Part 2: Experiment", Int. J. Earthquake Eng. & Struct. Dyn. 18, pp. 107-120, 1989. doi:10.1002/eqe.4290180110

7

C.S. Yim, A.K. Chopra, J. Penzien, "Rocking response of rigid blocks to earthquakes", Earthquake Engrg. Struct. Dyn., 8(6), pp. 565-587, 1980. doi:10.1002/eqe.4290080606

8

J. Zhang, N. Makris, "Rocking Response of Free-Standing Blocks Under Cycloidal Pulses", Journal of Engineering Mechanics 127(5)L 47383, ASCE, 2001. doi:10.1061/(ASCE)0733-9399(2001)127:5(473)

9

H. Kosaka, T. Noji, H. Yoshida, E. Tatsumi, H. Yamanaka, A.K. Agrawal, "Damping Effects of a Vibration Control Damper Using Sloshing of Water", Proc. Tenth World Conf. on Earthquake Engineering; Madrid, 19-24 July 1992. Rotterdam: A.A. Balkema, 1992, vol. 4, pp. 2435-2440.

10

Y. Fujino, "Tuned Liquid Damper (TLD) for Suppressing Horizontal Motion of Structures", Journal of Engineering Mechanics, vol. 118, n. 10, pp. 2017-2030, 1992. doi:10.1061/(ASCE)0733-9399(1992)118:10(2017)

11

P. Chaiseri, Y. Fujino, B. M. Pacheco, L.M. Sun, "Interaction of Tuned Liquid Damper (TLD) and Structure: Theory, Experimental Verification and Application", Structural Engineering/Earthquake Engineering, vol. 6, n. 2, pp. 273-282, 1989.

12

L.M. Sun, Y. Fujino, K. Koga, "Model of Tuned Liquid Damper for Suppressing Pitching Motions of Structures", Earthquake Engineering and Structural Dynamics, vol. 24, n. 5, pp. 625-636, 1995. doi:10.1002/eqe.4290240502

13

A. Kareem, "Next Generation of Tuned Liquid Dampers", Proc. First World Conf. on Structural Control: International Association for Structural Control; Los Angeles, 3-5 August 1994. G.W. Housner et al, eds. Los Angeles: Int.Assoc. for Structural Control, vol. 3, pp. 19-28, 1994.

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