Investigation into benefits of coupling a frame structure with a rocking rigid block

Abstract

This paper analyses the linear elastic coupling of a frame structure and a rigid block aimed at improving the dynamic behaviour of the frame. A multi-storey frame structure, modelled as a two-degree of freedom linear system, is connected by an elastic device to a rigid block. The nonlinear equations of motion of the coupled-system are obtained by a Lagrangian approach and successively numerically integrated to analyse the behaviour of the coupled system. Simulations are performed using harmonic excitation as forcing term. The results are summarized in gain maps. The maps show the ratio between the maximum displacements or drifts of the coupled and uncoupled systems in the plane of the system’s parameters. The results of the numerical simulations show that there are wide regions of the parameters where the coupling may be effective. Experimental simulations are then performed to verify the actual effectiveness of such a coupling. A scaled shear-type 2 d.o.f frame coupled with an aluminium rigid block is sinusoidally forced by an electro-dynamic long-stroke shaker. The system’s response in terms of displacements is measured by no-contact optical/laser sensors. The experimental tests confirm the effectiveness of the coupling as expected by the analytical model.