Preliminary studies for dynamical tests on a MDOF scaled model controlled by a semi active TMD

Innovative techniques based on the Structural Control approach are proposed and applied in many fields of engineering. Among the different kind of strategies, the semi active control appears interesting to be applied especially for civil and industrial structures for preventing damage due to seismic excitation. Tuned mass damper (TMD) has been demonstrated to be valid for response mitigation only in a small range of input frequencies, for this reason, in this paper it is proposed to connect the structure to protect and the TMD by means of a semi active device. The semi active damper is a magnetorheological (MR) damper, which can adjust in real time the control force by means of a control algorithm which acts modifying the input voltage (current) circulating inside the device. An ON-OFF control algorithm based on the Lyapunov stability theory is utilized to change the input voltage, in order to obtain variable mechanical characteristics for the device. To evaluate the performance of the control strategy, within an experimental campaign on the shaking table, numerical simulations are carried out on a 4 DOF scaled 1: 5 structure with a semi active TMD. Once the optimal mass ratio for the TMD and the optimal input voltage for the device has been estimated, some results about semi active control performances are illustrated. In particular, the case of semi active control is compared with both situations of no control and in case of MR damper acting in passive modality.