Keywords: rocking motion, unilateral rigid model, structural dynamics, control of vibrations, tuned liquid dampers, numerical investigation, laboratory experiments.

The rocking response and the possibility of overturning of rigid bodies in earthquakes are central considerations in seismic safety problems [1,2,3], since a broadly similar response can be observed, during earthquakes, in the behaviour of sculptures and remnants of ancient Greek and Roman stone temples, electrical equipment, retaining walls, liquid storage tanks, tall rigid buildings, and so on, and the need for understanding and predicting these failures in association with an attempt to estimate the related intensity levels of ground motion appears of basic importance.

As regards the many structural control applications, although a consistent effort in terms of scientific and factory research has been devoted to active and semi-active control approaches (which are potentially much more effective than passive analogous approaches, because of their skill of real time self-adaptation on the basis of the incoming dynamic excitation), the high sophistication and energy requirements of the components has resulted in passive devices being the most widely employed in real full-scale applications.

If suitably tuned on the basis of the expected characteristics of the seismic event and of the mechanical parameters of the structure, passive control systems represent economic, low invasive and rather effective techniques for mitigating the effects induced in civil engineering structures by dynamic events.

With this perspective, in the first part of the paper, the rocking response of rigid blocks is analyzed and experimental data are compared with numerical results developed by the implementation of the block dynamics in an ad hoc compiled calculus code, showing good agreement although the rocking motion is perturbed by a number of factors occurring during the execution of the experiments.

Thereafter the paper finally presents the evaluation of the benefits, in terms of mitigation of the structural seismic response, resulting from the adoption of special auxiliary masses, the tuned liquid dampers (TLDs), which have recently been the subject of increased interest by the international scientific community [4].

With this purpose in mind, some features of the experimental investigation developed on TDLs attached to rigid blocks under pure rocking are discussed, emphasizing the potential benefits produced by liquid dampers in terms of the mitigation of the structural response, if a proper design is provided.

1

G.W. Housner, "The behavior of inverted pendulum structures during earthquakes", Bull. Seism. Soc. Am., 53(2), 404-417, 1963.

2

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)

3

I. Corbi, R. Orefice, "Study of Rocking Response of Rigid Blocks using Shaking Table Experiments", in B.H.V. Topping, C.A. Mota Soares, (Editors), "Proceedings of the Seventh International Conference on Computational Structures Technology", Civil-Comp Press, Stirlingshire, UK, Paper 270, 2004. doi:10.4203/ccp.79.270

4

Y. Fujino, L. Sun, B.M. Pacheco, P. Chaiseri, "Tuned Liquid Damper (TLD) for suppressing Motion of Structures", J. Engrg. Mech., 118, 2017-2030, 1992. doi:10.1061/(ASCE)0733-9399(1992)118:10(2017)

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