Abstract
A refined control scheme with an optimal observer is presented for active optimal control of civil engineering structures. The purpose is to increase the accuracy and robustness of the control system. The structural stiffness and mass distribution cannot be evaluated with 100% accuracy, because there is gradual (aging, shift of live and dead load, etc.) or abrupt (plasticity due to extraodinary external force) change in structural behavior. In the proposed control scheme, stable control is achieved in an asymptotic manner, if there is large mass variation. However, the proposed scheme is not applicable for decrease of stiffness; and it is concluded that the use of servo-control scheme is recommendable in that occasion.
