OPTIMAL OPEN-LOOP CONTROL OF BUILDING STRUCTURES UNDER EARTHQUAKE EXCITATION

A study is made of the optimal open-loop control theory and its application to tall buildings under earthquake excitations. An active tendon control system and an active mass damper system are investigated. The earthquake ground acceleration is modeled as a stationary random process as well as a nonstationary random process. Random vibration analyses in conjunction with the optimal control theory are carried out to determine the building response and the required active control force. Since the building response under earthquake excitations is usually dominated by the first few lower modes, it is shown that the optimal critical-mode control can be as effective as the optimal global control. Monte Carlo simulation is used to study the response behavior of a building implemented with an active control system and excited by stochastic seismic loads. The sensitivity of the optimal open-loop control with respect to uncertainties involved in estimating the structural characteristics is also studied. It is shown that a significant reduction of the building response can be accomplished by use of either an active tendon control system or an active mass damper system while keeping the magnitude of the active control force within a practical range.