Improvement of the Dynamic and Seismic Behaviour of Rigid Block-like Structures by a Hysteretic Mass Damper Coupled with an Inerter

Abstract

The protection of rigid block-like structures against seismic hazards is a widely studied topic and has been achieved to different degrees with active and passive protection methods. For the protection of rigid block-like structures, this paper proposes the coupling of a rigid block-like structure, modelled as a single rigid block, with an external, auxiliary system through a hysteretic elasto-plastic device. The auxiliary system is constituted by an oscillating mass, whose inertial effects are amplified by the use of an inerter device. The auxiliary system works as a hysteretic mass damper. The elasto-plastic behaviour of the coupling device is described by the Bouc–Wen model. The mechanical model of the coupled system has two degrees of freedom, and its equations of motion can be written by following a direct approach. A preliminary analysis is performed by exciting different coupled systems and the corresponding stand-alone rigid blocks with harmonic base accelerations. Such an investigation is aimed at understanding the sensitivity of the dynamics of the coupled systems to the characteristics of the rigid blocks and auxiliary systems and is performed by comparing the frequency–response curves of the coupled systems with those of the corresponding stand-alone rigid blocks. A further analysis is performed to verify the effectiveness of the proposed protection methodology under seismic excitation. Both the harmonic and seismic analyses show that the main parameter to be tuned to achieve the protection of the rigid block-like structures is the apparent mass of the inerter device. A proper choice of such a mass improves the dynamics of the rigid block-like structures, leading to smaller oscillations for the same level of excitation.