Date of Award
Doctor of Philosophy
Base isolation is a novel concept for the protection of buildings up to eight storeys against severe earthquakes. The reduction in seismic forces on the building is achieved by inserting horizontally soft isolation elements between the superstructure and the foundation. As a result, inelastic deformations are limited to the isolators and the fundamental frequency is reduced from 2-3 Hz to typically 0.5 Hz. With the adoption of the base isolation concept, and the research already devoted to it, the questions remain as to the effect of soil-structure interaction, the reponse to turbulent wind in view of the increased flexibility and approximate methods of analysis for both seismic and wind loading.;In the first part of the study, the complex eigenvalue analysis is used to study the modal properties of three and five storey plane frames. The effect of soil-structure interaction is investigated for footings acting independently and also with dynamic interaction (cross-interaction) included. The effect of introducing vertical flexibility in the isolators (rocking) is examined. The suitability of approximate methods for free vibration analysis, idealizing the buildings as a sliding mass or as a rigid body on springs, is verified.;In the second part of the study, the seismic analysis of a five storey plane frame is performed in the time domain. The effect of base isolation in reducing the accelerations induced in the building is demonstrated. An approximate procedure for the time domain analysis of the multi-degree-of-freedom system using equivalent linearization is verified.;In the third part of the study, the wind characteristics of the lower portion of the boundary layer are studied in a wind tunnel and the forces acting on models of low-rise buildings are established. The response theory, with modifications based on the measured parameters, is used to compute the alongwind and torsional response of base-isolated buildings. For comparison, the response is computed using existing codes. A procedure, similar to the Canadian Code, is presented for computing both the alongwind and torsional response and is facilitated by a set of design charts.
Henderson, Paul Winston, "Dynamics Of Base-isolated Buildings" (1988). Digitized Theses. 1743.