Study of base isolation systems

Abstract

The primary objective of this investigation is to outline the relevant issues concerning the conceptual design of base isolated structures. A 90 feet high, 6 stories tall, moment steel frame structure with tension cross bracing is used to compare the response of both fixed base and base isolated schemes to severe earthquake excitations. Techniques for modeling the superstructure and the isolation system are also described. Elastic time-history analyses were carried out using comprehensive finite element structural analysis software package SAP200. Time history analysis was conducted for the 1940 El Centro earthquake. Response spectrum analysis was employed to investigate the effects of earthquake loading on the structure. In addition, the building lateral system was designed using the matrix stiffness calibration method and modal analysis was employed to compare the intended period of the structure with the results from computer simulations. Base isolation proves to be effective in reducing the induced inertia forces on a structure by increasing the effective period of oscillation. Keywords: Base Isolation, time history analysis, response spectrum analysis, matrix stiffness calibration method.