Use of overturning spectra in the performance evaluation of on-off control strategies for rocking objects

Rocking of rigid bodies induced by seismic events triggers a number of complex dynamic phenomena such as impacts, sliding, uplift, which can potentially result in disastrous outcomes. Typical structures that present a significant seismic vulnerability with respect to overturning are water tanks, electrical and hospital equipment, statues and art objects. Several methods have been investigated in the past years to prevent the overturning or damage, such as rigid anchorages or base isolation devices. This paper presents some numerical investigations about a novel on-off adaptive control strategy for rigid blocks subjected to rocking motion. In more detail, control algorithms were specifically conceived to regulate an adjustable stiffness of two restrainers placed at the lower corners of the block. The control’s laws and the anchorage devices exhibited good performance when excited by simple one-sine pulse excitation, as reported by the authors in a previous study. The present work will instead investigate the performance and the robustness of the controlled system with respect to amplitude modulated harmonic excitations.