Semiactive control of earthquake-excited structures

A new semiactive closed loop control algorithm is developed using an actuator with variable stiffness and damping to suppress structural vibrations caused by unknown disturbances such as earthquakes. It is assumed that the stiffness and the damping characteristics of the actuator can be changed independently from each other. The closed loop control algorithm is obtained by forcing the rate of change of the system energy to be as negative as possible. Optimal active control algorithm, which is an application of the linear regulator problem to structures, is used for the purpose of comparison. To demonstrate the efficiency of the proposed method, controlled and uncontrolled behaviour of a single story damped structure subjected to earthquake forces is investigated. It is shown numerically that the proposed semiactive control can be used effectively to reduce the earthquake induced structural vibrations.