Analytical and experimental investigation into the effectiveness of a pendulum dynamic absorber to protect rigid blocks from overturning

摘要

In this paper the effectiveness of a mass-damper dynamic absorber in preventing rigid blocks from overturning is investigated. The mass-damper is modelled as a pendulum, hinged at the top of the block, with the mass lumped at the end. The equations of rocking motion, the uplift and the impact conditions are derived in a rigorous way, while the results are obtained from the equations' numerical integration. Under an impulsive one-sine base excitation, an extensive parametric analysis is performed. In particular the frequency, the amplitude of the excitation along with the block and the mass damper's geometrical characteristics have been taken as variable parameters. Overturning spectra, providing the excitation amplitude of block's overturning versus the frequency of the one-sine pulse, are obtained. An experimental test is performed by using a linear electromagnetic motor that is used to realize a small mono-dimensional shaking table. A rigid block with fixed geometrical characteristics equipped with a pendulum is tested. Under a one-sine and a one-cosine impulsive base excitations, the overturning spectra are obtained. The results show that the presence of the mass damper leads to a general improvement of the dynamic response of the system. The experimental test confirms the validity of the analytical model as well as the effectiveness of the pendulum mass damper.