| The reported study investigates the feasibility of developing an active system, the C.CC-B.S.M (Computer-Controlled-Concave-Ball Support Mechanism), for the protection of structures against earthquakes. The envisioned system is incorporated in a specially designed supporting base. A computer simulation of the system is utilized for selecting the optimum design parameters of the base and the supporting elements. The system is to be controlled according to preprogrammed rules in order to minimize the forces transmitted to the structure. The inputs to the controller are the signals from appropriately placed off-site seismic detectors.;The seismic structural response analysis of single and multi degree of freedom buildings for the rigidly supported and isolated cases is investigated. An illustrative example shows that the proposed system is implementable and can result in orders of magnitude reduction in the transmitted force to the structures.;It can also minimize the torsional effects of non-symmetric buildings resulting from any arbitrary distribution of the mass. The potential application and the limitations of the proposed concept for the protection of different types of structures against catastrophic damage by earthquakes are also investigated.;An active base isolation system for the protection of bridges subjected to earthquakes is also proposed. The system incorporates spherical supports, cams and springs which can be optimally designed to minimize the transmissibility of the seismic disturbances to the bridge structure. The considered examples show that the proposed design can provide an order of magnitude reduction in the maximum stress resulting from transverse or longitudinal seismic waves.;Since the system performance is highly dependent on the rapid unlocking of the cams in the event of a seismic disturbance, careful consideration should be given to the design of a reliable cam release control. This can be achieved by spring loading each cam such that it would be normally unlocked. A hydraulic actuator would be used to force it rotate to the locking position under fluid pressure which would be constantly maintained at the design level during normal conditions. The actuator would be equipped with a quick response release valve for rapidly releasing the pressure and consequently unlocking the cam as soon as an earthquake is detected. |
