Semi-active predictive control of non-linear structures with controlled stiffness devices and friction dampers

A predictive semi-active control system used to improve the response of non-linear multistorey structures to earthquakes is presented. A system of controlled stiffness devices (CSD) and friction dampers (FD) is studied. The system combines the forces produced by the semi-active FD and additional stiffness supplied by the CSD in order to obtain an optimal structural response. A predictive algorithm is used to overcome the time delay problem in the control system. The control forces in the FD are calculated at every time step by applying the instantaneous optimum control law according to the structural behaviour predicted for the next time step at each storey level of the structure. The proposed system can be efficiently used for structural control because the forces developed in it are independent of the structure's displacements or velocities. Its efficiency is demonstrated by a numerical simulation of a seven-storey building subjected to various seismic excitations. The simulation shows that the behaviour of a structure with the proposed control system is significantly improved compared to an uncontrolled one, or controlled by friction dampers or by semi-active controlled stiffness devices only. The structural response with a predictive controlled system is similar to that with an instantaneous one.