Active control devices, such as active mass dampers, are mainly employed for the reduction of wind-induced vibrations in highrise\nbuildings, with the final aim of satisfying vibration serviceability limit state requirements and of meeting appropriate comfort\ncriteria. When such active devices, normally operating under wind loads associated with short return periods, are subjected to\nseismic events, they can experience large amplitude vibrations and exceed stroke limits. This may lead to a reduced performance of\nthe control system that can even worsen the performance of the whole structure. In this paper, a nonlinear control strategy based\non a modified direct velocity feedback algorithm is proposed for handling stroke limits of an active mass driver (AMD) system.\nIn particular, a suitable nonlinear braking term proportional to the relative AMD velocity is included in the control law in order\nto slowdown the device in the proximity of the stroke limits. Experimental and numerical free vibration tests are carried out on a\nscaled-down five-story frame structure equipped with an AMD to demonstrate the effectiveness of the proposed control strategy.
Loading....