| Two hybrid control systems are proposed for protecting building structures against strong earthquakes. The hybrid control systems consist of a base isolation system connected either to a passive or active mass damper. The base isolation system, such as elastomeric bearings, is used to decouple horizontal ground motions from the building, while the mass damper, either active or passive, is used to protect the safety and integrity of the base isolation system. The performance of the proposed hybrid control systems is evaluated and compared with that of an active control system. It is shown from the theoretical and numerical results that the proposed hybrid control systems are very effective in reducing the response of either high-rise or low-rise buildings under strong earthquakes. The practical implementation of such hybrid control systems is easier than that of an active control system alone.; In reality, many tall buildings undergo large deformation when subjected to strong earthquake ground motion and hence exhibit nonlinear behavior. Passive protective devices, such as rubber base isolators and sliding systems, always exhibit large deformation behavior, leading to nonlinear equations of motion for the entire structural system. Hence, for the combined use of passive/active control systems, the active control system should be capable of dealing with nonlinear structures.; This study developed three optimal control algorithms that are flexible enough to reflect various hysteretic behaviors of inelastic systems and capable of describing the hysteretic behaviors of different base isolation systems. Extensive numerical and theoretical studies were conducted for applications to different types of hybrid protective systems. Results indicate that the optimal control theories developed here are efficient and practical. |
