Semi-active continuous control of base-excited structures: An exploratory study

The semi-active (SA) control techniques appear a realistic way to adopt active control in structural engineering. This paper reports an exploratory study on SA continuous control, where the mechanical parameters of the devices may continuously assume any value between the given limits. First, a Lyapounov-based control strategy for SA continuous control is proposed and studied for base-excited structures. The obtained continuous control process is initially applied to a seismic-excited single-DOF structure with a variable stiffness device, in order to study the dynamics of the controlled system and the optimal configuration of the algorithm. Successively, the optimized control strategy is applied to single-DOF structures with more realistic SA elasto-plastic devices, and the performances of SA continuous control are compared with the ones of passive and SA ON–OFF control cases. Finally, the obtained results are verified and confirmed in the application to a 4-storey Multi-DOF-framed structure, equipped with continuously variable SA magnetorheological dampers. The study shows the applicability and the possible advantages of the proposed control case, also in comparison with passive and SA ON–OFF cases. Generally it may be stated that the best performances in terms of structural displacements may be obtained by using ON–OFF SA control. Differently, continuous SA control significantly reduces the absolute accelerations and the total forces transmitted to the structures.