Seismic isolation systems are widely recognized as beneficial for protecting both acceleration- and displacement-sensitive nonstructural systems and components. Furthermore, adaptive isolation systems have been shown to enable engineers to achieve various performance goals under multiple hazard levels. These systems have been implemented for horizontal excitation, but there has been very limited research on isolation for vertical excitation. Thus, this paper seeks to evaluate the benefit of adaptive vertical isolation systems for component isolation, specifically for nuclear plants. To do this, three vertical isolation systems are designed to achieve multiple goals: a linear spring and a linear damper (LSLD), a linear spring and a nonlinear damper (LSND) and a nonlinear spring and a linear damper (NSLD). To investigate the effectiveness of the proposed systems, a stiff piece of equipment is considered at an elevated floor within a power plant. A set of 30 triaxial ground motions is used to investigate the seismic response of the equipment. The maximum isolation displacement and equipment acceleration are used to assess the effectiveness of the three isolation systems. While all systems significantly reduce the seismic accelerations on the equipment compared to the fixed-base case, a LSND system is shown to exhibit superior seismic performance across multiple hazard levels. / Thesis / Master of Applied Science (MASc)

<p>The rolling isolation system (RIS) studied in this dissertation functions on the principle of a rolling pendulum; an isolated object rests on a steel frame that is supported at its corners by ball-bearings that roll between shallow steel bowls, dynamically decoupling the floor motion from the response of the object. The primary focus of this dissertation is to develop predictive models that can capture experimentally-observed phenomena and to advance the state-of-the-art by proposing new isolation technologies to surmount current performance limitations. To wit, a double RIS increases the system's displacement capacity, and semi-active and passive damped RISs suppress the system's displacement response.</p><p>This dissertation illustrates the performance of various high-performance isolation strategies using experimentally-validated predictive models. Effective modeling of RISs is complicated by the nonholonomic and chaotic nature of these systems which to date has not received much attention. Motivated by this observation, the first part of this dissertation addresses the high-fidelity modeling of a single, undamped RIS, and later this theory is augmented to account for the double (or stacked) configuration and the supplemental damping via rubber-coated bowl surfaces. The system's potential energy function (i.e. conical bowl shape) and energy dissipation model are calibrated to free-response experiments. Forced-response experiments successfully validate the models by comparing measured and predicted peak displacement and acceleration responses over a range of operating conditions.</p><p>Following the experimental analyses, numerical simulations demonstrate the potential benefits of the proposed technologies. This dissertation presents a method to optimize damping force trajectories subject to constraints imposed by the physical implementation of a particular controllable damper. Potential improvements in terms of acceleration response are shown to be achievable with the semi-active RIS. Finally, extensive time-history analyses establish how the undamped and damped RISs perform when located inside biaxial, hysteretic, multi-story structures under recorded earthquake ground motions. General design recommendations, supported by critical-disturbance spectra and peak-response distributions, are prescribed so as to ensure the uninterrupted operation of vital equipment.</p> / Dissertation

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