Composite semiactive control of a class of seismically excited structures

The paper deals with the formulation of semiactive controllers for a class of nonlinear seismically excited base-isolated structures in order to reduce the absolute motion of the base and the inter-story drifts of the building structure. The advantage of the proposed control scheme is that semiactive control devices are only required at the base and the first floor to adjust on-line the damping and stiffness using their displacements and velocities as feedback information. The feedback control law is derived and analyzed via Lyapunov stability techniques. A numerical example is given to illustrate the effectiveness of the control scheme for a 10-story frictional base-isolated structure subject to seismic actions.