Semi-active control of seismic response of tall buildings with podium structure using ER/MR dampers

A tall building with a large podium structure under earthquake excitation may suffer from a whipping effect due to the sudden change of building lateral stiffness at the top of the podium structure. This paper thus explores the possibility of using electrorheological (ER) dampers or magnetorheological (MR) dampers to connect the podium structure to the tower structure to prevent this whipping effect and to reduce the seismic response of both structures. A set of governing equations of motion for the tower-damper-podium system is first derived, in which the stiffness of the member connecting the ER/MR damper to the structures is taken into consideration. Based on the principle of instantaneous sub-optimal active control, a semi-active sub-optimal displacement control algorithm is then proposed. To demonstrate the effectiveness of semi-active control of the system under consideration, a 20-storey tower structure with a 5-storey podium structure subjected to earthquake excitation is finally selected as a nu merical example. The results from the numerical example imply that, as a kind of intelligent control device, ER/MR dampers can significantly mitigate the seismic whipping effect on the tower structure and reduce the seismic responses of both the tower structure and the podium structure.